# Enhancing tone through changing caps and resistors....not new tubes



## greco (Jul 15, 2007)

Quote *"It's the actual circuit that really gives an amp its distinctive sound. How you arrange the resistors and capacitors and what values you pick for them. Changing the value of one capacitor can make a zillion times more difference than the brand of a tube." *End of Quote

Wild Bill wrote this is response to a recent thread discussing the choice of tubes.

I'd like to know more about which resistors and capacitors influence tone the most and how one decides to increase or decrease the value of the components. 

I understand that there are 1000's of circuit designs and that certainly complicates this request. However, any *basic* information would be appreciated.

Just hoping this thread will teach us more about what Wild bill is saying to us on a repeated basis. (I've read this comment a few times from him in other threads)

Thanks

Dave


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## bcmatt (Aug 25, 2007)

Are you sure that that kind of knowledge isn't classified?
Don't we have to keep the classes separated?
I don't know what would happen to the world if the Ken Fischers and Wild Bills were mixing and sharing forbidden knowledge with regular schmucks like us.

Hmm, that looks mean when I read it back to myself...I just mean it as a joke... I'm just not very funny.
I know Wild Bill helps us understand anyway he can, and on everything we show interest in. I think of the Amp Tech Section as Wild Bill's (and other helpful techs worth mentioning)'s free online University.

Ok Professor, I'm ready to learn; I'll shut up now...


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## Jeff Flowerday (Jan 23, 2006)

Specific value changes in specific places can have many different effects.

Without isolating to a single circuit and then a single portion of the circuit, the question is really unanswerable.

Maybe pull up a 5F1 champ circuit and start with that. That should make Bill's job much easier.


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## Wild Bill (May 3, 2006)

greco said:


> Quote *"It's the actual circuit that really gives an amp its distinctive sound. How you arrange the resistors and capacitors and what values you pick for them. Changing the value of one capacitor can make a zillion times more difference than the brand of a tube." *End of Quote
> 
> Wild Bill wrote this is response to a recent thread discussing the choice of tubes.
> 
> ...


Dave, you're right that there are many different designs so I can't really give you any universal tips. 

That being said, here are a few links to guys that have written FAQ's for both newbies and experienced tubeheads. Check 'em out and you won't be sorry!

http://www.aikenamps.com

http://tone-lizard.com/

http://www.blueguitar.org/

http://www/geofex.com

There's also a board for techs: http://www.firebottle.com/ampage/ This is actually a mirror of an old site. There's a link to their new one on the opening page. They kept the old one as an invaluable archive of tube stuff!

I've spent a lot of time on these sites. These guys have invested a lot of time to create info resources for us tubeheads. We owe each and every one of them beer!

Since all but Randy's Tone-lizard site are American a gift of a Canadian beer would be princely indeed!:smile:

:food-smiley-004:


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## Wild Bill (May 3, 2006)

Jeff Flowerday said:


> Specific value changes in specific places can have many different effects.
> 
> Without isolating to a single circuit and then a single portion of the circuit, the question is really unanswerable.
> 
> Maybe pull up a 5F1 champ circuit and start with that. That should make Bill's job much easier.


Good idea, Jeff! I shudda thought of that. Brain worked fine before the kids came!:smile:

Still, I was composing while your post arrived and the links I've given should answer all kinds of such questions!

I'll still be around to help as the guys wade through them!

:food-smiley-004:


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## greco (Jul 15, 2007)

Thanks for all the responses. 

Many thanks for the links, Wild Bill. 

Wild Bill: If I could get my brain to work as well as yours does now...I'd consider starting a family again !! LOL

If anyone else is interested, I'd like to try what Jeff suggested. Even if we just take one part of the circuit at a time.

Does anyone know how to post a pic of a 5F1 champ (or similar) circuit (or part of the circuit) that would fit (with reasonable detail) in one of these "response' spaces/boxes?

I'll try...but if others know a good method, it would really be helpful.

Hope this thread will keep going.

Thanks again.

Dave


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## Jeff Flowerday (Jan 23, 2006)




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## Stratin2traynor (Sep 27, 2006)

Since we are on the subject of tone...Can anyone somehow tell me what difference it will make to cut the bright cap on the Vibrato channel of my DRRI. The thing sounds amazing straight up with my Strat but once an OD is kicked on it just goes for shit - all fizzy with excessive treble. Hurts my ears, ya know. 

The pedals sound better on the Normal Channel but the "magic" just isn't there like it is on the Vibrato Channel. I've read that the mod will make the Vib Ch sound more like the Norm Ch - but with the extra Db's gain on Vib 1 the magic is still there. 

True or not. Do tell. 

Also, is it possible to through an extra switch in there as a "Bright Switch" when needed????

If this is deviating too much from the current thread, I apologize.


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## Budda (May 29, 2007)

i've also wantd to do the cap/resistor change to an amp to make it more of a beast then it was intended.


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## bobb (Jan 4, 2007)

Just to give you a visual idea of how changes in the tone stack affect the sound, check out this Tone Stack Calculator.


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## bcmatt (Aug 25, 2007)

I don't know if I'm merely embarrassing myself by even suggesting this; or if I am ruining the whole education process by giving an alternative to the schematic, but when I look at a schematic (because I am a visual person) I am translating it to an image like this in my head; so maybe this picture from the ceriatone website is useful. I imagine Nik wouldn't mind:








Ignore this if this is not helpful.


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## davetcan (Feb 27, 2006)

Now that's what all schematics should look like. :smile:


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## greco (Jul 15, 2007)

That the schematic and layout diagram are perfect !! Thanks!!

I'm glad that we have both an actual schematic and a layout as I'm not very efficient with reading schematics myself, as yet. 

Now we have a starting point...many thanks again.

I'd like ask a question...but I'm at work and i'll need more time. Hopefully this evening.

Anyone else? ....

Dave


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## Scottone (Feb 10, 2006)

I used to mess around with this stuff a bit, and it really gives you an appreciation for the pros like Wild Bill. IMO it takes years of experience to get to the point where you can tune an amp to suit a particular customer's requirements.

A couple of pretty standard tweaks are:

- adding or removing cathode bypass caps on pre-amp stages
- changing the value of a cathode bypass cap
- changing the value of some or all of the coupling capacitors
- increasing or decreasing power supply capacitance

For example, referring to the schematic on the previous post, if you put a 25uf cap in parallel with the 1500 ohm cathode resistor on the first pre-amp stage, you would get an increase in gain and a change in frequency response. Now, this may or may not sound good. If you put a smaller value on there...let's say the classic Marshall value of .068 uf, then a brighter tone would be produced.

If you really want to get into this stuff, I highly recommend the London Power series of books by Kevin O'Connor (particularly "The Ultimate Tone" books). It goes into all of this is minute detail. 

Good luck..


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## bcmatt (Aug 25, 2007)

Scottone said:


> For example, referring to the schematic on the previous post, if you put a 25uf cap in parallel with the 1500 ohm cathode resistor on the first pre-amp stage, you would get an increase in gain and a change in frequency response.


Hey, that's pretty interesting! I just noticed that that is the first difference between this circuit and the BF champ circuit.
Wow! I learned something today; and it's only 8:42 am! Now I will always pay attention and observe what caps are in the first preamp stage.

Heheheh, I feel like I want to use this new knowledge for evil: Striking up conversations with annoyed music store clerks and asking them what value of cap might be in the first preamp stage of every amp they sell. I would probably only have to ask that question about one amp before they refer to me as a douche-bag when I leave the store.


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## greco (Jul 15, 2007)

I don't want this thread to get lost from view, so I'm posting in the hopes that it will continue to be of interest after the busy times of Christmas and New Year celebrations have calmed down.

Cheers

Dave


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## Adicted to Tubes (Mar 5, 2006)

Build it and it will come.

Tone that is!

Build a champ and tweak the crap out of it and you'll soon see that Leo already did it and the original design is damn close to having all the tweaks necessary.


www.claramps.com


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## fraser (Feb 24, 2007)

i went this way with a valve junior, just swapping resistor and cap values, using better quality stuff. i learned a lot, and the thing sounds incredible, ive got a good creamy distorted tone at about 3 oclock on the dial lol- no clean headroom. eventually i had to tell myself to stop- i was spending too much time on it because i just couldnt stop. ive left it alone for a while now lol.
when i was done i tried different tubes, but the originals work the best to my ear now. lots of fun, some frustrating moments, but still fun.
going to do a champ kit next, soon as ive got the scratch:smile:


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## Kapo_Polenton (Jun 20, 2007)

Sometimes even a simple portion of the circuit is all that it takes. I know through biasing my Laney pro tubes that the factory bias pot is set so that you run slightly colder. No matter what the tubes, they want you to be able to throw in EL34's and not have to bias. I often bet that if I changed that pot and dialed in the tubes a bit hotter, this thing would really open up and sound closer to the godly 1982 JCM800 I just picked up on the weekend . As a result, the stock pot makes the amp a bit gritty and sterile because it is cold. Bill does this reasoning make sense to you as well?


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## Wild Bill (May 3, 2006)

Kapo_Polenton said:


> Sometimes even a simple portion of the circuit is all that it takes. I know through biasing my Laney pro tubes that the factory bias pot is set so that you run slightly colder. No matter what the tubes, they want you to be able to throw in EL34's and not have to bias. I often bet that if I changed that pot and dialed in the tubes a bit hotter, this thing would really open up and sound closer to the godly 1982 JCM800 I just picked up on the weekend . As a result, the stock pot makes the amp a bit gritty and sterile because it is cold. Bill does this reasoning make sense to you as well?


Absolutely! However, there's a bit more to the story.

The factory doesn't really care if you have to re-bias or not, as long as the warranty is over!:smile: That's the real reason they ship the amps biased so cold. Less chance of any failures during warranty. Now that players are more aware of the need to bias I'm not surprised if the factories are restricting the range on the bias pot. They have a real reason to worry that someone who doesn't understand how to calculate the max safe idle current may crank the bias pot and burn out his tubes early. Then the player is likely to go back to the store where he bought the amp and give them a hard time about the cost of the new tubes!''

The scariest thing I ever see on so many Internet sites is some guy saying "I always bias my EL34's to 43 ma!" without saying anything about the plate voltage or any other factors. Such a statement only proves he's a complete maroon but I see it every day, usually from guys who sell tubes!

:food-smiley-004:


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## Kapo_Polenton (Jun 20, 2007)

Holy smokes that is high! I think the most i may have had mine at one point was 35 or so.. so what do you think about the 70% hoopla? Is running them at 70% too hot?


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## Wild Bill (May 3, 2006)

Kapo_Polenton said:


> Holy smokes that is high! I think the most i may have had mine at one point was 35 or so.. so what do you think about the 70% hoopla? Is running them at 70% too hot?


Calm down, KP!:smile:

I pulled that 43 ma. figure out of my butt! It has NO relation to what's safe in your Laney!

How could it? I don't know the plate voltage in your Laney!

I'm fine with 70% in class AB1, which is most guitar amps. Actually, I can't hear much difference from 60-70% so I'm not too anal about being all the way to the limit. If I check the bias and it's in that ball park area I just leave it. The tubes won't complain!

:food-smiley-004:


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## bcmatt (Aug 25, 2007)

Scottone said:


> For example, referring to the schematic on the previous post, if you put a 25uf cap in parallel with the 1500 ohm cathode resistor on the first pre-amp stage, you would get an increase in gain and a change in frequency response. Now, this may or may not sound good. If you put a smaller value on there...let's say the classic Marshall value of .068 uf, then a brighter tone would be produced.
> Good luck..


I was just rethinking this today. Isn't the Tweed usually higher gain than a Black Face Champ? So, wouldn't adding the 25uF cap clean up the Tweed a bit?
I have a BF, and I was contemplating putting that on a DPDT so that the cap could be added or removed in parallel to the 1k5 resistor, putting it back and forth between BF and Tweed. Am I a complete idiot?


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## bcmatt (Aug 25, 2007)

Wild Bill said:


> Dave, you're right that there are many different designs so I can't really give you any universal tips.
> 
> That being said, here are a few links to guys that have written FAQ's for both newbies and experienced tubeheads. Check 'em out and you won't be sorry!
> 
> ...


I've been to these sites before but I think I helped remedy some of my ignorance today by studying the great Canadian Tone-Lizard site and in particular the breakdown of the different stages of the classic Fender amp:
http://tone-lizard.com/Mods_and_Odds.htm
He actually describes what altering some of these resisters and caps produce in tone. There's even a chart.


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