# Component Drift



## ampaholic (Sep 19, 2006)

I've read a number of times where techs will go through a vintage amp and check every resistor and capacitor for a significant drift in value. My understanding has always been that to do this accurately you need to pull free at least one end of the component otherwise the value may be impacted by other components in the circuit.
This would be a really time intensive task though, and expensive if you are paying someone to do it. So I suspect that components are likely being checked in-circuit?
And are capacitors being checked with a capacitor tester?


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## greco (Jul 15, 2007)

3 dislikes for this post...deleted in case the post could be misinterpreted and/or misleading in any way.


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## Wild Bill (May 3, 2006)

First off, there's little or no need to check caps. They don't change much as they age and besides, the values are not at all critical anyway! The exception would be filter caps that slowly dry up inside over the years but the effect of that is excessive power supply hum - a totally separate problem.

That leaves resistors as the only real worry. Modern film resistors don't really drift but the old classic carbon comps are notorious! These are the ones to be concerned about. The kicker is lots of current causing internal heat. That means that grid resistors tend to stay stable but plate load resistors can drift a LOT! Plate current is significant but the current in a grid resistor or one in the tone stack is likely mice nuts.

I got a good tip from an old timer years ago that I have used ever since. Sooner or later carbon comps will add so much noise a player just can't stand trying to play through all the hiss and spit and so will bring me his amp to have them replaced with quiet, modern film resistors. The first thing I ask him is how happy he is with the tone of his amp, despite the noise. If he likes it the way it is I do NOT replace the resistors with the schematic values willy-nilly!

With any of the old carbon comps that are in tone sensitive areas of the circuit (which is NOT all of them!) I measure them and replace them with their drifted value, rather than that of the original value.

If I went with the original values the amp would then sound like it was brand new but that was NOT the tone the owner had become used to hearing! Using the drifted value keeps the tone the same as that to which he had become accustomed.

Be very wary of self-appointed internet gurus who tell you to replace everything. They really don't understand their electronics! They likely have never read a theory book in their life!

With some parts it's useful and with others it has no benefit and is a waste of time and money. 

A few hours of book learning now and then can make far more of a positive difference and save you lots of money in the bargain!

Wild Bill/Busen Amps


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## ampaholic (Sep 19, 2006)

Mine is not quite as modern! It's advantage though is the ability to test caps with voltage applied.









Maybe they are selective in what they measure but I get the impression they check everything.


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## JHarasym (Mar 27, 2007)

Wild Bill said:


> ... likely mice nuts.


I think "Mice Nuts" would be a great name for a breakfast cereal.


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## jb welder (Sep 14, 2010)

Like Wild Bill suggested, component drift can in fact be responsible for the vintage tone someone is in love with. So changing drifted parts can actually cause a loss of that great tone. 
Playing a vintage '59 Fender side by side with it as it sounded the day it came out of the box would be interesting.
As far as measuring resistors in circuit, resistors only increase in value, never decrease. Measuring in circuit can only cause a false "low" resistance reading. So if a resistor measures above it's value "in circuit", it has definitely drifted high.


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## nonreverb (Sep 19, 2006)

Wild Bill speaks the truth. The only exception I would bring forward is regarding very old amps with wax caps. They're very susceptible to moisture and will drift quite substantially off their spec (almost always upwards) which can cause undesirable tone. I know this because all Hammond organs made before '64 use them and are the main cause of dark, flat tone in them.


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## Lincoln (Jun 2, 2008)

just ever so slightly off-topic.......can anyone direct me to a chart where I can figure out the value of this type of capacitors? I can't seem to find a chart that makes sense. (I'm trying to copy something)









my wife doesn't love me near enough to get me a capacitance meter for christmas


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## ampaholic (Sep 19, 2006)

Lincoln said:


> just ever so slightly off-topic.......can anyone direct me to a chart where I can figure out the value of this type of capacitors? I can't seem to find a chart that makes sense. (I'm trying to copy something)
> 
> View attachment 9926
> 
> ...


Looks like a bunch of mice nuts to me.


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## dtsaudio (Apr 15, 2009)

Lincoln, do a google search for tantalum capacitor color code. 
There's too many to link. Unfortunately you may still run into non-standard coding.


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## dcole (Oct 8, 2008)

As far as measuring these components in circuit, you tend do do that with the amp powered off and power supply caps drained. When you put your meter across a plate resistor, there is effectively no alternative path in parallel with the resistor. The coupling network to the next triode stage acts as a very high impedance due to the capacitor and the tube also is not conducting at this time. What you end up with is the value of the resistor.


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## greco (Jul 15, 2007)

Wild Bill...why the "thumbs down" on post #2?

Cheers

Dave


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## ampaholic (Sep 19, 2006)

dcole said:


> As far as measuring these components in circuit, you tend do do that with the amp powered off and power supply caps drained. When you put your meter across a plate resistor, there is effectively no alternative path in parallel with the resistor. The coupling network to the next triode stage acts as a very high impedance due to the capacitor and the tube also is not conducting at this time. What you end up with is the value of the resistor.


Thanks! That's the kind of info I was looking for. And I guess if a resistor is measured in circuit and the value is too wacky then you need only lift one side and recheck to see if something else is affecting it.


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## jb welder (Sep 14, 2010)

ampaholic said:


> I guess if a resistor is measured in circuit and the value is too wacky then you need only lift one side and recheck to see if something else is affecting it.


Yes, but this is what I meant before, you only need to disconnect and double check if it reads low. There is nothing that can make a resistor read a _higher_ value in circuit. So if a resistor reads high in circuit, it is bad/high, you don't need to lift a leg to recheck. That is the only exception I can think of.


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## ampaholic (Sep 19, 2006)

jb welder said:


> Yes, but this is what I meant before, you only need to disconnect and double check if it reads low. There is nothing that can make a resistor read a _higher_ value in circuit. So if a resistor reads high in circuit, it is bad/high, you don't need to lift a leg to recheck. That is the only exception I can think of.


Makes sense. Thanks


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## Wild Bill (May 3, 2006)

greco said:


> Wild Bill...why the "thumbs down" on post #2?
> 
> Cheers
> 
> Dave


Dave, coupling caps aren't prone to drift in value. It's just the physics and chemistry of the materials involved. I'll agree with nonreverb that the old wax ones will change over time as the wax dries up. I suspect that it's not the actual capacitance value so much as the internal resistance, or ESR. This might still change the tone but in a different way.

So I don't see the value in checking parts that rarely are likely to have changed! Furthermore, coupling caps have a VERY broad curve for their frequency response compared to their farad value! Changing from .01 to .022 just can't be heard by the human ear. The oldtimer's rule of thumb is if you are going to change a coupling cap for a different tonal range then use a factor of at least 10 times. That means changing a .01 to a .1 mfd or vice versa.

The only way I would expect to see a cap drift so much that your ear could hear it is if the cap actually opened up inside! The range of drift just couldn't be enough to matter!

I think of coupling caps as really AC resistors. AC resistance is called reactance. Unlike DC resistance it varies with the frequency of the signal. Lower frequencies will see a higher resistance trying to pass through a coupling cap than higher frequencies, depending on the specific cap value. This is how tone control circuits work, using combinations of caps and resistors in ways that can be varied, to change how well high or low frequencies can pass through or be bypassed to ground.

I can truthfully say that I have never bothered with a cap checker in my life! Never needed one! A short or an open tends to be obvious. A sufficient change in value due to drift over the years for the human ear to detect is exceedingly rare. 

Who has the time or the patience to just check EVERYTHING? Even those things that aren't relevant?

When I was a lad first starting to solder, I used to get very frustrated checking everything in a circuit 'cuz I had no idea of how things worked. Basically, I was just changing part after part after part until eventually by process of elimination I would find a bad one. Then I discovered by READING A BOOK how parts and circuits actually worked! That changed EVERYTHING!

What used to take me days then took only hours. What formerly took hours was reduced to minutes! I resolved to learn as much theory as I could, for the simple reason that I am inherently impatient and lazy!:Smiley-fart:

Wild Bill/Busen Amps


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## greco (Jul 15, 2007)

Thank for the reply, Wild Bill.

I worded my post poorly. However, I didn't mention anything about testing caps whatsoever.

I showed a pic of a cap meter because the OP asked _"__And are capacitors being checked with a capacitor tester?"_ ...I was showing an example of a basic dedicated cap meter (only to find out that the OP had a fantastic cap meter) but was NOT indicating that any of the caps need to be tested as a matter of routine to determine drift.

I think a cap tester is very handy for an electronics hobbyist, as the codes on (some) small caps can be a pain to read in order to be certain of their value. 

Cheers

Dave


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## jb welder (Sep 14, 2010)

I guess we're getting a bit into semantics here with capacitors drift vs defect. Caps go open or leaky. It is not uncommon. Electrolytic (usually filter) caps tend to go open, leading to loss of filtering (hum). Non-electrolytic (usually coupling) caps tend to go leaky, allowing DC to leak through from stage to stage and cause biasing problems, especially if leaking into the power tube grid circuits.
Both cases of going open or going leaky will show up as incorrect value if measured with a cap meter. Should we call this "drift"? I'm not sure, it's not really what I think of drifting, it's more of a failure. But you can call it what you like.
For myself, if I'm looking for bad caps in a circuit, I use my regular meter. Filter caps that measure more than minimal AC voltage on them are not doing their job. Coupling caps that are not blocking all the DC from getting through them are not doing their job.
Either case would also measure wrong with a cap meter.
How about electrolytic bypass caps in the cathode circuit of a preamp stage? Probably need a cap meter for that. Or for checking new or unused caps before installing them into a circuit. I don't do those things, but that doesn't mean I shouldn't oughtta' :smile-new:.

I do agree with Bill, I don't think anyone goes through and checks _everything_, just usual suspects. I suppose for super collectible stuff it may be done, but I doubt it.


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## greco (Jul 15, 2007)

jb welder said:


> I guess we're getting a bit into semantics here with capacitors drift vs defect. Caps go open or leaky. It is not uncommon. Electrolytic (usually filter) caps tend to go open, leading to loss of filtering (hum). *Non-electrolytic (usually coupling) caps tend to go leaky, allowing DC to leak through from stage to stage and cause biasing problems, especially if leaking into the power tube grid circuits.
> *
> *Both cases of going open or going leaky will show up as incorrect value if measured with a cap meter.* Should we call this "drift"? I'm not sure, it's not really what I think of drifting, it's more of a failure. But you can call it what you like.
> 
> ...


Very interesting, especially (for me) the bolded parts.

Thanks

Cheers

Dave


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## Lincoln (Jun 2, 2008)

I was buying some .02uF caps today. Then I noticed the ones I picked out were +80% -20% so I found some better ones.
That's a pretty wide range! :sSig_Idontgetit: Supports what Wild Bill was saying about cap values not being
all that critical.


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## jb welder (Sep 14, 2010)

Very good point about the tolerance Lincoln, it's often not listed on the cap, and +80% could be interpreted as "drift" when it could have measured that value new !
And what I said earlier about caps "tending" to go open or leaky, I meant _when_ they go bad, which may be 30 or 40 yrs (or more or less) from new. I did not mean to imply they all go bad. Electrolytics have lifespans (often shown as hours in the specs), good non-electro's can live forever.


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## parkhead (Aug 14, 2009)

Lincoln said:


> I was buying some .02uF caps today. Then I noticed the ones I picked out were +80% -20% so I found some better ones.
> That's a pretty wide range! :sSig_Idontgetit: Supports what Wild Bill was saying about cap values not being
> all that critical.


If you were trying to duplicate an old amps tone I think you would be better served to pay attention to cap materials and physical dimensions. 

Some of the older caps were physically larger and made by rolling foil and a dialectic material together. later caps use mylar that is sprayed with aluminum to form the plate. Later still caps were "crushed" after this tubular form was rolled up. All of these changes were made to reduce ESR and Self inductance. These two factors have a dramatic affect on the ability of the cap to pass some higher frequencies. 

In certain cases "vintage caps" have a tendency to ring in the upper frequencies. We hear this as chime and sometimes swirl ! 
Many caps do not do this but some of the popular Mustards, astrons and others used in vintage amps have distinctive character. 

I would assert that you can hear the difference between a .02 cap and a .01 in a circuit ... 
Home builders try this experiment ...
Build a stock JTM45 circuit and wherever the schematic calls for a .02 use a .01 
to make the test consistent used mallory 150's or the same brand and make for both the .01 and .02 caps 

you might be surprised at how good that circuit sounds with that kind of small tweak. 
as someone noted if some caps are +/- 20% or worse there is a lot of factory fudge factor to play around with 

If you have built an amp with modern flattened mylar caps and crave a more traditional tone 
going to a tubular cap can be an eye opener 

IMHO this illuminates the debate around Orange Drops vs Mallory Tubular types. The Orange Drop has less ring 
so in certain distortion circuits & amps where tightness is desirable these caps are preferred.

in other amps where the goal is to make the amp RING trainwrecks, for example, ..certain marshalls and more traditional amps 
the tubular type with its "fizzy frequency" attenuation and upper mid-range ring is the way to go 

people like Dumble and Ken Fischer worked with these properties to create their "high tweak" sounds 
and this is why the clone amps tend to be less three dimensional or miss the mark completely 
it also explains why the designs changed slightly from build to build, in those cases the right cap or value was the one 
that generated the desired harmonics ... in that amp that day combined with those other components ! 

FWIW I have done extensive swap out experiments of this nature and use these techniques with excellent results. 


P


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## Lincoln (Jun 2, 2008)

good timing on the bump of this thread. I was just thinking about it.

I see things like NOS "mustard Caps" for sale on ebay all the time for about $30 each. To me that's for people trying to build an original marshal and they want it to look as correct as possible. I can't see them making a difference in tone that we could hear or measure. 

I've collected a fair amount of old caps from various sources. I've been warned not to use the old Areovox wax caps and I can see that. Then there are the TRW molded brown plastic caps from the 50's, and the white caps from the 60's (can't remember the name on them) which are probably very useable still. I've been struggling with whether to use old caps in my builds or not. Is it more than just looks? Dimensions on the old caps are certainly a lot closer to original.

I do look at pictures of original boards and try to use ceramic dics where the factory did, drops where they used drops, and tube caps where they used tube caps. That's more where my confusion lies.......wondering if I'm getting the right style of cap in the right places.


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## parkhead (Aug 14, 2009)

Lincoln said:


> good timing on the bump of this thread. I was just thinking about it.
> 
> I see things like NOS "mustard Caps" for sale on ebay all the time for about $30 each. To me that's for people trying to build an original marshal and they want it to look as correct as possible. I can't see them making a difference in tone that we could hear or measure.
> 
> ...


I made a test rig consisting of a project box with a copper buss bar connecting two input jacks 
I used an alligator clip running to ground through a 250k resistor 
I soldered every .02 cap I had onto the buss bar 

I then removed the tone cap from my guitar and plugged this rig into a fairly sensitive amp 
moving the alligator clip swapped the caps in real time while I played 

I did this to challenge the myth of the sprague bumble bee and instead 
had my head blown apart ! 

Here were some of the results 

#1 the sprague bumble bee and the sprague 160p double the sustain of a decaying chord or note 
they also add an obvious pulsing swirl of harmonics as the note fades out 

#2 ceramic disc caps make your pickups sound dull and lifeless and have the least sustain and harmonic content in a guitar circuit (get them out of your guitars NOW!) 

#3 any tubular cap sounded better than the others with regard to sustain and harmonic content 

#4 reversing any cap marked with an external foil band showed that the caps sounded remarkably different based on orientation (mind blown) 

#5 the Mojo Dijon and Mullard mustard sounded close to the same, adding harmonic content only in the upper frequencies ... but were not as swirly and animated as the Bumble bee 

#6 the bumble bee or spargue 160p was the king of guitar tone caps hands down, and sounded identical in both orientations.. these added chime, sustain and angelic harmonics to the guitar sound 

Keep in mind that this test was in a pull down tone control to ground configuration 

Now if we want translate this data to amplifier circuits we have different scenarios depending on where we might find the cap. 
In a tweed deluxe the "tone control" works just like a guitar selectively grounding highs...
so in that location the cap data translates directly 
a ceramic disc .0047 would make the amp more dull than a bumble bee .0047 in the same spot 

in an inter stage cap the cap is a pass through device 
so theoretically the bumble bee cap would be attenuating some highs (in the tone control it worked better by blocking the highs from grounding out adding "sparkle") 
this effect might also account for the smooth top end of an authentic vintage amp compared to a reissue or repro

In the case of the mullard it had the jangly effect of the Bumble bee but only on the upper trebles 
the mids were clear and faded out quickly 
so I concluded that in an inter stage application in a Marshall Type amp the mullard cap would pass mids and upper mids cleanly while slightly attenuating the 
higher treble frequencies .. this would provide the Marshall with its upper miidrange CUT while smoothing some of the nasties out of that treble boost 
this should be obvious to anyone who has played older plexi marshalls and compared them to the HARSH reissue amps 

The Yellow astrons are a little darker and more swirly like the Bumble bee ... and so the tweed Bassman despite sharing the same circuit as 
the JTM45 bass and pa models sounds darker and more elegant in its mid range
The Marshall while a copy of the bassman would have better upper mids but still attenuate some of the fizzy trebles 
IMHO if you want a JTM45 tone you need this kind of cap 

Obviously some will argue the conclusions I have drawn and extended from a simple tone cap listening test, however 
in subsequent amp build experiments I have been able to select caps based on these ideas and more quickly achieve 
the desired tones ... in particular a tweed deluxe with a non stock .0047 bumble bee on the tone pot sustains better with more harmonic bloom 
than with the non stock ceramic disc .0047 I replaced. 


I don't think this is drift... these things had these "defects from new" and if you are going to waste your dough on anything 
genuine NOS caps will do more for you than you might ever imagine.
However, I do not think you need them in every circuit in the amp, probably just a few key places where they ring the right frequencies 
or attenuate the fizzies. 

Many people spend way to much on boutique Les Paul pickups looking for PAF nirvana 
the bees and 160p caps are 50% + of that sound and can still be found as pulls for $10 to $100 each 

Here's a good example 
http://youtu.be/66pnwYUnT2c

modern PRS Guitar with boutique pickups and sprague 160p .02 tone cap 
modern vox ac4 with just the tone cap replaced with a sprague 

at the fade out 2:75 you can hear the sustain



If you have a ceramic cap for the tone control in any electric guitar... replace it with anything tubular 
of the same value you have laying around ... then send $5 in a brown envelope to me or name your first born after me 

p


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## WCGill (Mar 27, 2009)

It's quite a stretch extrapolating shunt capacitance tone in a guitar tone stack to coupling cap applications in amps.


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## parkhead (Aug 14, 2009)

WCGill said:


> It's quite a stretch extrapolating shunt capacitance tone in a guitar tone stack to coupling cap applications in amps.


totally, however, it did successfully predict some good sounding caps to use so I stand by my bad voodoo pseudoscience. 

I don't think the capacitance is the factor, The sound of the cap is changed by the ESR and that ESR is frequency dependent. Modern cap makers are striving to lower ESR by rolling tighter caps and crushing them into chicklets after rolling them. 

At the end of the day I do not have to fully understand what is going on to extract a tonal and musical benefit. 
Undertsanding can lead to more fresh ideas. If someone were to prove bumble bees sounded good because of the brand of paint used on the casing... I would be happy to be corrected especially if I could buy some of that paint and make my own great sounding caps. 

as I noted I started experimenting with these caps specifically to disprove that they could make an audible difference in a guitar circuit 
now I believe that specific "defective" or "low quality" or "high ESR" capacitors are the elusive tone of certain guitars. 

this makes me happy 

p


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## WCGill (Mar 27, 2009)

I fail to understand how a shunt cap can "add" anything to a guitar's tone. It's role is to roll off high frequencies and nothing more. With old caps, I'm sure if you measure 10 of them, you'll get 10 different measurements and 10 different corner frequencies. What are you hearing? Bring your caps over and I'll clip them in and out of circuit while you listen. I guarantee you won't be able to tell which is which. I don't doubt you will probably hear differences but the identity of each will be beyond yours or anyone's capabilities. I had a fellow who I mentored who insisted on building amps with Sprague caps and carbon comp resistors-all pulls. I see these amps on a regular basis and the caps are mostly all leaking DC and none of his builds are outstanding in any way.


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## nonreverb (Sep 19, 2006)

I think the blind test would be required here. Someone doing the testing themselves WILL skew the results 100 times out of 100. It's not a balanced test under any circumstances.


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## parkhead (Aug 14, 2009)

WCGill said:


> I fail to understand how a shunt cap can "add" anything to a guitar's tone. It's role is to roll off high frequencies and nothing more. With old caps, I'm sure if you measure 10 of them, you'll get 10 different measurements and 10 different corner frequencies. What are you hearing? Bring your caps over and I'll clip them in and out of circuit while you listen. I guarantee you won't be able to tell which is which. I don't doubt you will probably hear differences but the identity of each will be beyond yours or anyone's capabilities. I had a fellow who I mentored who insisted on building amps with Sprague caps and carbon comp resistors-all pulls. I see these amps on a regular basis and the caps are mostly all leaking DC and none of his builds are outstanding in any way.



with all due respect to you both..... you know more that I ever will However, 

I assure you that I was firmly and happily in your camp. Then I decided to prove I was right by making a cap test rig. 
This unleashed the genie from the bottle. Despite what we assume, certain cap construction styles do affect the sustain of a guitar when used as a standard pull down type tone control. You do not have to believe me, I outlined the test rig I made and it is dead easy to duplicate. 

As far as the science of why this is happening I have done enough reading to identify the mechanism in action but would rather keep that info for my own use. 
I do not build amps or guitars with old pulled parts, however for the purposes of sharing information in this forum, most home-builders would not go too far wrong 
using genuine sprague 160p .02 or bumblebee .02 in their humbucking guitars if they are seeking the original tone. 

I have identified a modern equivalent but keep this information private. 

Everyone I have shared this info with who has tried these caps in their instrument has used foul language and expletives to indicate their joy. 

I have extended the experiment to amplifier builds (I do not use old caps) and have found that these type of misbehaving caps were part of the original sound of certain 
amplifiers. This is working for me and I share this info to encourage others smarter than myself to stumble upon their own answers. 
I would also point out that there are only certain circuits in an amp that are drastically affected by the cap quality, in 90% of the functions a common modern cap would be inaudible. 
However in key spots magic can happen. 


As I noted the #1 take away from the experiments was that ceramic disc caps in standard guitar circuits Kill Sustain, and that tubular constructed caps do not kill sustain, and the old spragues the hardcore Gibson burst (not reissue) guys rave about are not snake oil or cosmetic mojo they are doing THAT THING ! 

Disclosure: I do not own a 59 burst, a generous and good friend does, and he has let dozens of people play it in clubs and live situations, including some guy name Joe... needless to say his Dog Ears and non technical insights have helped a great deal in highlighting the science behind whats going on in these guitars. 

the bottom line is you may want to remove those ceramic discs from your mid 90's les paul especially if you have had more than one set of pickups in it! 

even Paul Reed Smith has stumbled upon this phenomena, originally his guitars all came with ceramic disc .02 caps 
as all of his recent guitars now come with a modern tubular cap, still not a great cap, but clearly a step in the right direction 

Gibson's recent Warren Haynes 335's had the Mojo and Sustain, a call to gibson revealed that they are using reproduction*** 1961 style sprague 160p caps 
they will not sell these or disclose who or how they are being made. I am assuming that whoever made these caps for Gibson also made the Bumble bees 
for the more recent Beano and Kossoff guitars which sounded closer to right than any recent gibson guitars. If you find anyone with a Beano or Kossoff 
who will let you crush and unravel the cap please let me know. Gibson has now dropped the ceramic disc in their production guitars as well making a big fuss about using Orange Drop caps. 

*** the good news is that no one tools up to make 200 capacitors so whatever Gibson is now having made, for their uber custom shop guitars is out there somewhere ! 

p


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## parkhead (Aug 14, 2009)

nonreverb said:


> I think the blind test would be required here. Someone doing the testing themselves WILL skew the results 100 times out of 100. It's not a balanced test under any circumstances.


A friend whom I gave two Capacitors for his LP called me up and said ya know "I used a stopwatch on a G chord 11 seconds with the ceramic disc ... 20 seconds with the new caps.... CRAZY" 
Blind tests are great but not needed if the results are this Obvious. 

I gave one to a guitar repair "god" and former burst owner, to try, and he came back the next day and said "can I have more, one for each of my guitars?" 

P


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## WCGill (Mar 27, 2009)

I have a Beano and apparently the "Bumblebee" caps in this guitar are only cheap Wesco caps in striped bodies. Not an issue for me as I don't use the tone controls on this or any of my guitars.


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## greco (Jul 15, 2007)

Retail at ~$175.00...on sale for ~115.00










And then you remove the "wrapper" to find.......


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## nonreverb (Sep 19, 2006)

Yup....case and point.



greco said:


> Retail at ~$175.00...on sale for ~115.00
> 
> 
> 
> ...


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## parkhead (Aug 14, 2009)

POINT 1 
Regarding Case and POINT ... whoop, so Gibson can't even get the box right notice it says .22 mfd ,
it should be .022
This photo is very old news, this photo has been circulating since 2008 or earlier 

I believe they are using something else in the Beano and some of the more expensive clone guitars as they do sound different 
the change happened around 2012 or 13 and only on the clone guitars like the Beano, Kossof & Haynes 335 
The Haynes uses a new production 160p style cap... I asked if they were using NOS and they insisted it was new production 
I asked if they will be selling the 160p clone and they will not...
My guess is that the mylar wesco cap has been replaced by a wesco or other kraft paper and foil cap... 

POINT 2 

I would hope that anyone reading this thread is acutely aware that a guitar tone capacitor is still altering the tone of a guitar even when the control is set on 10.

This is why the enhanced sustaining effect provided by authentic bumble bee and 160p caps is active even when the tone control is full up. 

also note that any vintage cap marked with a outside foil band sounds very different when reversed in the same circuit! 


Point 3 

The dramatic enhanced sustain effect of the 160p and bumblebee are a byproduct of the authentic vintage cap and a result of its kraft paper & foil layered construction.
Other companies used the same materials but layered the materials in a different pattern to provide a higher quality cap... they don't sound like spragues. 
Modern Tubulars share a small element of this 5%? as do modern paper in oil caps 7%
unfortunately all of these modern caps use the better winding techniques and better materials so they add just a little sustain 
this is an inevitable fact of electronics parts construction where change is constant in order to improve quality and miniaturization 

ceramic discs do not enhance sustain, they are zero on our scale 

I have nothing more to add, those who choose to do their own tests with an open scientific mind will be pleased


P


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## nonreverb (Sep 19, 2006)

Some believe in Jesus....some don't.


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## ampaholic (Sep 19, 2006)

nonreverb said:


> Some believe in Jesus....some don't.


I don't think this discussion could be summed up any better than that.


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## greco (Jul 15, 2007)

It is ironic that a thread entitled "Component Drift" has "drifted" so much.

Cheers

Dave


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## Lincoln (Jun 2, 2008)

greco said:


> It is ironic that a thread entitled "Component Drift" has "drifted" so much.
> 
> Cheers
> 
> Dave


Talking tubes and capacitors around here is like talking religion and politics elsewhere - best to be avoided :sFun_dancing:


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## JeremyP (Jan 10, 2012)

Lincoln said:


> Talking tubes and capacitors around here is like talking religion and politics elsewhere - best to be avoided :sFun_dancing:


HELL YES!!! Everyone has their own opinion on this. Quite some time ago I decided to put it to the test and tested a bumblebee against a same value (both measured) greenie. I could hear no difference at all. I also have swapped caps in amps lots and as long as values were the same , brand never changed the tone .. To my ear...... That said I have friends who swear it's like night and day for them, and we have all argued til blue faces ensued.

In the end I think as a community we have to put this in the "Lets agree to disagree" pile, unless we want to slide into CIVIL WAR...


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## parkhead (Aug 14, 2009)

I will have to disagree with some of you here. 

I have done the tests and have my data, if you don't have it and that makes me a believer... so be it. 

The original question was 
"I've read a number of times where techs will go through a vintage amp and check every resistor and capacitor for a significant drift in value. My understanding has always been that to do this accurately you need to pull free at least one end of the component otherwise the value may be impacted by other components in the circuit.
This would be a really time intensive task though, and expensive if you are paying someone to do it. So I suspect that components are likely being checked in-circuit?
And are capacitors being checked with a capacitor tester?" 


To sum up yes, many techs check components for drift in circuit. 
You don't need to lift the component to know that its out by 20% or more or that the "wrong" component was used from the factory 
ie a killer sounding super bass I own with a single original and clearly marked .002 cap instead of a .02 as marked on every schematic. 

I have Data on well over 100 significant vintage amps. I have interesting proprietary (personally collected) data on a small number of significant celebrity modded amps. 
One a local legend of "superlead tone" that was subtly modded to be more like a vox AC50 ! 3 or 4 parts changed ! 
I have been luck enough to have been able to take detailed notes on several significantly killer sounding guitars and amps and later been able to 
reproduce the oddity. These days people bring me very cool things to look at and take notes... including a Fender modded by a Legend who wrote 
"F$%CK OFF get your own mod !!" in sharpie inside the amp. That mod was interesting because of what had been removed (lots) & and significantly "unnecessarily" added in!
a real head scratcher... why would someone build in a unused circuit unless it affected the tone dramatically? 

The point I was endeavoring to make was that chasing drift may not be the right methodology. 
Perhaps chasing production errors, bad repairs (that sound good! or bad) and other quirks may be more fertile ground. 
Taking Notes and now photos is key! 

Take for example a 59 Les Paul, the pickups are supposed to be 7.25k however they average about 8k 
this is not drift, as much as it is very poor manufacturing tolerances and those components measured around 8k when they were new. 

as many know from experience slapping an 8k humbucker into a new les paul does not produce the 59 tone... 
changing the TP to aluminum, the studs to steel, the pickups to real PAF's and the caps to real Bees... DOES 
as does changing the pickups to XXXXXX and the caps to YYYYY the studs and TP as described
(that research took took 2+ years with the co-operation of a burst owner) 

(there are people who do not accept that real PAF pickups have a significant tonal property... OK .. does this make me a BELIEVER? or just a guy who's played them and listened?) 


Take a 65 reissue Deluxe and park it next to a 65 deluxe reverb... they sound very different even if you cross swap the speaker leads 
(the 65 is Darker, warmer more complex, smokey swirly? harmonically rich and a host of other flavors) 
is it because the carbon comp 100k resistors measure 110k or is it because carbon sounds different than 1/4 watt carbon film resistors? 

or... is it because the tiny brown chinese mylar 400 volt caps sound dramatically different than the blue molded caps from 65 

the point being of the 100 parts options that could sound different and they may taken individually each sound 2% different
they probably did not drift there, they were probably + or - 20 % when new 
In the case of Blue molded caps they use separate layers of aluminum foil and paper to make a cap. The modern caps are mylar sprayed with aluminum molecules
layerd with mylar rolled very tight and then crushed into a flat cap to reduce ESR.. they may both be .02 capacitance but every other spec is wayyyy better in the modern cap!

Finally you have to really understand the circuits you are looking at even beyond the depth that the design engineers did, they just selected parts from the bin 
tested and amp till a few people liked it and figured out how to build it to meet the cost specs 
any major company making a serious effort to reproduce their vintage product has been forced to call in outside experts and tone GURU's... people who have done this research 
this is why you get "this years new spec re-issue syndrome" 

in a typical BF fender there are four Caps and one resistor which dramatically influence the overall tone ... the other 100 components are needed but do not create the 
signature tone of the amp. 


Bottom line this is not about belief ... this is about a question, and the answer 
I am confident I have done the research to share some insight, but I will not GIVE away all my hard earned answers 
with any luck one of you will stumble onto another element of the puzzle and share a clue or two and inspire further research 

Just as a race motor builder will not give out his exact Cam Profiles ... 
but might be happy to talk cam ideas all day long 

I won't give away FISH but I am happy to talk about Fishing Techniques 

If this is just about BELIEF why is tone ever a topic on any guitar forum 


p


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## jb welder (Sep 14, 2010)

There are tests and there are scientific tests using scientific method. If you don't use the scientific method, then it can be mostly belief.
Scientific method requires double blind testing.
Parkhead, I'm less opposed to what you are saying then some here, but your testing leaves too much to your beliefs and imagination.
If you want to re-do your tests of all those caps in the guitar with alligator clips with double blind method I'll be all ears. Same with the reversal of the foil band thing.
Until then it is unknown whether it is just belief or not.


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## parkhead (Aug 14, 2009)

I once suggested to a well known amp company they build the power supply in a tube amp a very specific way. 
The engineers built two, called in a bunch of guitar players and asked them what they liked. 

they all chose the specific modded version... and built it

I had reached the correct conclusion via my own ear tests and they later validated 
the specs 

when I do a test I build two units, and play them both on a gig 
one with the change and one without ... by the end of the night it should be clear which is better 
this may not be double blind enough for you but the methodology works well enough for my needs 
sometimes I use a switch in the polarity hole in an amp... If I can't tell which way the switch is flipped 
by playing the amp the idea is not significant 

It's like being in the recording studio... with the right sound engineer 
you can trust a simple A B fader swap decision without a formal blind test 
at some point you CAN trust people with trained ears and later validate the results formally if need be 

the key scientific principle is that the results must be repeatable 
if I said red painted output transformers sounded better and gave you the paint code 
you painted a transformer and it did not sound better then we would have failed 

if I gave you a schematic for a power supply and said "guitar players will love it" 
and you built it into an amp and compared it to the stock version, and they loved it
the science would be valid without a full formal blind test 

a double blind test is not needed if you use other methods to remove your bias and have trained your ears 

in other words if I am in the shop and I hear a difference with a parts swap 
I do not assume My ears are being fooled I try and understand why the sound has changed 

example: the V1 coupling cap is far more audible than the final power amp pair in an amp. though most techs 
would say they can hear a value change there ... can I call a .02 vs .1 from outside the amp ?
not yet, there are 100 other components involved. 

can I say that a traynor ygm3 amp sounds better with a .02 or .01 v1 coupler vs the factory .1 
absolutely ! I would at least hear the amp and say 
"its sounding tight in the bottom so someone has tweaked something" 
or "wow that xyz amp sounds killer may I have a look and draw the schematic, and take pics? " 

PS> with the foil reversal thing just try it (some caps (newer) don't do it) no one believes it.... 
but when you try one that does it you will spew a stream of colorful expletives! it is so darn obvious WTF! 

Final point ... When I got my first 160p I slapped it into my PRS and went to rehearsal 
that night the guys all turned to me and said "whats with you? you are on fire tonight" (I am not that good!) 
Afterwards that I constructed the test rig to try and identify what they could hear...

if you build a race car motor and turn in a significantly faster lap at the track you don't need to put the old motor back in to double blind your findings 
all else being equal the lap time is sufficient proof of concept to validate your build 

if you are able to stopwatch a 9 second sustain increase on a G chord after a cap change... you probably want to dig deeper into that cap type 
and find some more examples 

FWIW when you have 9 seconds extra sustain to play with your guitar is a LOT more fun and things are way more "on Fire" 

Soooooooooo
Here's the Formal Challenge 

Go out and obtain a Sprague 160p 400 volt .02 capacitor and a ceramic disc .02 as a baseline (10$ on fleabay... often found in Gibson amps) 
install it in a humbucking type guitar ... some of you will have access to one of these 160p caps and can report back

Played clean you should hear 
A) an obvious increase in the tail lentgh of a note 
B) increased harmonic content and swirl in the decay of that note (angel voices, backup singers?) 
C) using a clean tone and held chord or capo to remove variables you should be able to verify this with a stopwatch 
or looking at a waveform in protools if you want to be super strict 

Go ahead prove me wrong 

cautions 
I have not tested these with a ceramic high output metal type pickup but the results should hold 
With distortion you are introducing a secondary variable, however your distortion tone will improve dramatically 
and this should be "seat of the pants" noticeable 
provided you can fix your amp settings you should be able to use distortion for this test though distortion has its own harmonic content


if you have a poorly setup guitar that does not ring you may not get the string vibrating long enough to hear it 


Bottom line all of this is verifiable and repeatable. no matter the bias of the naysayers who choose their belief over science and reason
The test above is repeatable 

p


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## nonreverb (Sep 19, 2006)

The original question was 
"I've read a number of times where techs will go through a vintage amp and check every resistor and capacitor for a significant drift in value. My understanding has always been that to do this accurately you need to pull free at least one end of the component otherwise the value may be impacted by other components in the circuit.
This would be a really time intensive task though, and expensive if you are paying someone to do it. So I suspect that components are likely being checked in-circuit?
And are capacitors being checked with a capacitor tester?" 


To sum up yes, many techs check components for drift in circuit. 
You don't need to lift the component to know that its out by 20% or more or that the "wrong" component was used from the factory 
ie a killer sounding super bass I own with a single original and clearly marked .002 cap instead of a .02 as marked on every schematic. 

This is not drift. This is a manufacturing error.....completely different thing. Of course it will change the tone. 

I have Data on well over 100 significant vintage amps. I have interesting proprietary (personally collected) data on a small number of significant celebrity modded amps. 
One a local legend of "superlead tone" that was subtly modded to be more like a vox AC50 ! 3 or 4 parts changed ! 
I have been luck enough to have been able to take detailed notes on several significantly killer sounding guitars and amps and later been able to 
reproduce the oddity. These days people bring me very cool things to look at and take notes... including a Fender modded by a Legend who wrote 
"F$%CK OFF get your own mod !!" in sharpie inside the amp. That mod was interesting because of what had been removed (lots) & and significantly "unnecessarily" added in!
a real head scratcher... why would someone build in a unused circuit unless it affected the tone dramatically? 

The point I was endeavoring to make was that chasing drift may not be the right methodology. 
Perhaps chasing production errors, bad repairs (that sound good! or bad) and other quirks may be more fertile ground. 
Taking Notes and now photos is key! 

Chasing drift is excellent methodology!...and it's far more common than production errors.

Take for example a 59 Les Paul, the pickups are supposed to be 7.25k however they average about 8k 
this is not drift, as much as it is very poor manufacturing tolerances and those components measured around 8k when they were new. 

as many know from experience slapping an 8k humbucker into a new les paul does not produce the 59 tone... 
changing the TP to aluminum, the studs to steel, the pickups to real PAF's and the caps to real Bees... DOES 
as does changing the pickups to XXXXXX and the caps to YYYYY the studs and TP as described
(that research took took 2+ years with the co-operation of a burst owner) 

(there are people who do not accept that real PAF pickups have a significant tonal property... OK .. does this make me a BELIEVER? or just a guy who's played them and listened?) 

Sorry, but I've had the rare pleasure of playing several real '58,'59 and '60's...some were excellent, some were great and some were just OK....kinda like CS Les Pauls made today.
Remember....those guitars probably sounded different new than they do today....so does that make them superior than todays offerings? Not really....just a shitload more expensive for reasons that have little to do with their intended purpose.

Take a 65 reissue Deluxe and park it next to a 65 deluxe reverb... they sound very different even if you cross swap the speaker leads 
(the 65 is Darker, warmer more complex, smokey swirly? harmonically rich and a host of other flavors) 
is it because the carbon comp 100k resistors measure 110k or is it because carbon sounds different than 1/4 watt carbon film resistors? 

Because of component drift.....why else?

or... is it because the tiny brown chinese mylar 400 volt caps sound dramatically different than the blue molded caps from 65

the point being of the 100 parts options that could sound different and they may taken individually each sound 2% different
they probably did not drift there, they were probably + or - 20 % when new 
In the case of Blue molded caps they use separate layers of aluminum foil and paper to make a cap. The modern caps are mylar sprayed with aluminum molecules
layerd with mylar rolled very tight and then crushed into a flat cap to reduce ESR.. they may both be .02 capacitance but every other spec is wayyyy better in the modern cap!

Finally you have to really understand the circuits you are looking at even beyond the depth that the design engineers did, they just selected parts from the bin 
tested and amp till a few people liked it and figured out how to build it to meet the cost specs 
any major company making a serious effort to reproduce their vintage product has been forced to call in outside experts and tone GURU's... people who have done this research 
this is why you get "this years new spec re-issue syndrome" 

in a typical BF fender there are four Caps and one resistor which dramatically influence the overall tone ... the other 100 components are needed but do not create the 
signature tone of the amp. 

Really?? So THE most important component in the entire amp doesn't factor in??? The speaker is where EVERYTHING passes, all the tone modifiers in the amp don't mean squat if the speaker ain't makin' it. How about that insignificant little item called the output transformer?? Undersized? Interleaved? impedance mismatched? 
Power transformer? tube rectified, converted to SS? I think your synopsis is lacking many other factors well beyond caps 'n resistors....
You want to change the tone? Start where it really counts!

Bottom line this is not about belief ... this is about a question, and the answer 
I am confident I have done the research to share some insight, but I will not GIVE away all my hard earned answers 
with any luck one of you will stumble onto another element of the puzzle and share a clue or two and inspire further research 

Just as a race motor builder will not give out his exact Cam Profiles ... 
but might be happy to talk cam ideas all day long 

I won't give away FISH but I am happy to talk about Fishing Techniques 

If this is just about BELIEF why is tone ever a topic on any guitar forum 

BELIEF without all the facts is just that belief...


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