# Another "help, please!" email from a newbie - Wild Bill



## Wild Bill (May 3, 2006)

Here's another email for help I'm sharing with everybody on the board:

*"Dear Mr Wildbill Costello I have a Vox AC30 CC2 and I would like to have it modded to the JMI specs as per the Lyle Caldwell mods but as I live in England I cannot send the amp to you for you to do the work so I hope you may be able to sell me instructions or even just the 3 vox cc diagrams off the net with all the parts clearly marked by you[ I have run coppies off the net of these diagrams so they are readily available ]that I would need to change and state what I have to change them too. I have managed to get a lot of the info off the net but in most cases it states to change the signal resistors to a certain type and the power resistors to another the problem for me is I do not know which are the signal resistors or which ones are the power resistors so I need more detailed instructions for example change r1 to 1/2 watt metal film value ?? or r2 to 1 watt carbon comp value ?? and the same with the capacitors, I have looked on the Sozo site at the vintage mustard Vox capacitor kits but they all seem to have different values to the existing caps in my amp on the board with the ecc83s there for I have no idea which ones to swap for the correct changed values, I also know that some ceramics on the same board need changing, at least 1 to a Sozo at c23 and some other ceramics to silver mica for all pf values I have already replaced all the 450v electrolytic caps on the board that has the el84s on it and also the 2 ceramic caps on the same board as Vox UK advised me they needed changing as most of the power was going mainly to 1 valve and constantly blowing it and those cheap caps are a common cause of that problem, I used vishay bc and that problem is know sorted and OK, I have also done the normal channel pre amp gain with a jumper on the resistor and will do the bright cap mod on c13, I am good with a soldering iron and know the safety precautions and to discharge the caps before undertaking work so don't worry about that and with detailed instructions I can easily do the work my self so could you please tell me what you would charge for the info I need to allow me to do the work, presumably the easiest way would be after I pay you you could then email the attachments with the instructions, also I would like to swap out any cheap parts that are prone to fail and replace them with top quality ones so I could also do with that info as well, my aim is to make the amp the best it can possibly be and also make it more reliable, please email me as soon as you have time to let me know if you can send me the info and the price that you will charge, thank you and Kind regards, D.... J.....[ I have sent a photo attachment that shows where the Sozo caps go "*

Hi D.....l!

This is not the first time I've been asked to help in this way and I'm sorry, but it just isn't practical!

What you are really asking me to do is to map out detailed instructions so that someone can do such a job without understanding anything about tube amp electronics. This is far more difficult than it sounds! First off, I don't keep a Vox AC30CC2 of my own in the shop to refer to when writing the instructions. Also, it would be like writing a small book! To be of any value to you it would have to be almost fool-proof, 'cuz if someone made a mistake they would have great difficulty getting back on track, since they didn't understand what they were doing.

So if I came up with a custom instruction manual for you it would be prohibitively expensive. My shop rate is $60/hr. I could easily spend a LOT of hours on a manual, making it more expensive than taking it to a tech and paying him to do it for you. I could do the mods myself within 2-3 hours. I couldn't imagine making you an instruction manual for less than double that.

There just isn't any substitute for gaining your own education and experience! Could you imagine trying to rebuild an automobile engine from an instruction manual when you had never before "popped the bonnet"?

Some years ago I gave it a try for one fellow and it became a very ugly experience. Despite what I thought were explicit instructions he couldn't help but make a few mistakes, which meant more emails and eventually telephone calls to answer. The time involved became crazy!

Another problem I have is that I find pictures almost impossible to work with! They never show clearly where the connections are going or which parts connect to what. A wiring schematic is plain as day but a picture I just find totally confusing.

I really suggest D.... that you either pay a tech to do the work for you or find a local friend with experience who's willing to coach you. Coaching would be the best solution as that would be education for life!

It's like building a kit! Most people build a kit or two when they're starting out. They teach you what the parts look like and how to wire and solder. However, after you've built a kit you realize that you still don't have a clue as to how it works or how to repair it if it breaks down. So more kits will not give you anymore education. When I was a kid there was nowhere for classroom instruction so I devoured every electronics book I could find and blew a lot of things up! 

A bit more advice. Don't get all excited about carbon comp resistors and Sozo caps. Any REAL tech knows this is all mojo! Carbon comps are the biggest hiss, spit and crackle generators on the planet! The electronic industry was overjoyed when films were invented and the whole world bailed out on carbon comps almost overnight! Expensive coupling caps are also just mojo. This stuff leaks over from the audiophile world, where nobody has ever actually read an electronics book but instead figures that the more expensive a part is the better it must work!

Again, this is just unscientific crapola! Resistors do NOT affect tone! They impede ALL frequencies equally! Capacitors couple AC signals. The material doesn't affect the tone. You should never forget, electronic parts don't deal with sound. They deal with electrons flowing as electricity. It's not sound until the speaker cone moves some air! It's not like an acoustic guitar where the sound vibrations travel differently through different kinds of wood. There is NO sound inside a guitar amp circuit!

This means that half the mods out there actually do nothing to change the tone! What's happening is that guys are trying to duplicate exactly the parts used in the original version of an amp, even though many of them are not part of any tone influencing part of the circuit! They have to duplicate EVERYTHING because they don't understand what is or is not important, or what is safe to substitute and what isn't.

All the technobabble sure can sound pretty! It just doesn't actually mean anything, technically.

If the bit about coupling caps was actually true, why in the world would someone use audiophile caps in an electric guitar amplifier? To make a great rock and roll amp sound like your hifi? Do you want to sound like Brian May or Mantovani? Eddie Van Halen or John Tesh?

Anyhow, good luck! I am posting your email on the guitarscanada.com board for all other newbies to share and it's possible that some others with more tech experience may be able to help you on a more "hobbyist" level (meaning the time is free!)

WB


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## greco (Jul 15, 2007)

Thanks for sharing this Wild Bill. Very enjoyable and well written, as always.

As per your advice (to the person above) , I'm (also) still reading books on electronics theory, I just haven't had any luck blowing anything up ...YET ...LOL. Does a very hot, smoking transformer count?

Just to let you know, specifically in your honour, I use the term "mice nuts" as often as possible (while giving you full credit). Gotta love that phrase !!

Cheers

Dave


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## nonreverb (Sep 19, 2006)

+1 Bill....and to further your argument against this mod, there is much more which would need to be done to fully convert it to a JMI...its a totally different design! The old amp has different transformers, has 6 inputs(3 channels), no master or reverb and the vibrato circuit is different...It would be like trying to make a silk purse out of a sow's hear. (no offence to cc2 users)


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## GuitarG. (Apr 1, 2010)

Wild Bill said:


> A bit more advice. Don't get all excited about carbon comp resistors and Sozo caps. Any REAL tech knows this is all mojo! Carbon comps are the biggest hiss, spit and crackle generators on the planet! The electronic industry was overjoyed when films were invented and the whole world bailed out on carbon comps almost overnight! Expensive coupling caps are also just mojo. This stuff leaks over from the audiophile world, where nobody has ever actually read an electronics book but instead figures that the more expensive a part is the better it must work!
> 
> Again, this is just unscientific crapola! Resistors do NOT affect tone! They impede ALL frequencies equally! Capacitors couple AC signals. The material doesn't affect the tone. You should never forget, electronic parts don't deal with sound. They deal with electrons flowing as electricity. It's not sound until the speaker cone moves some air! It's not like an acoustic guitar where the sound vibrations travel differently through different kinds of wood. There is NO sound inside a guitar amp circuit!


Interesting Bill. I do agree with you on the sozo caps deal. 5 dollars for a cap is a bit outrageous. Alot of that is hype. On the other side of that, some of the cheap foreign caps are poor for use in guitar amplifiers, especially when you want too "push" an amp. Capacitance can be increased by larger plate surface or wider distance between the plates. Some manufacturers actually etch the plates to give them more surface area. Thus more capacitance in a smaller package. Saves them money. While this works in most electronics, and can sound fine in a guitar amp at low volumes, an amp sounds poor at high volumes. For that reason i would only stick too certain "brands" of caps for guitar amps.

With regard too your view on mods involving resistors and capacitor values, could you please explain too me why a Marshall Super Bass and a Marshall Super Lead, while having the same transformers and being played through the same speaker cab sound different? The circuitry is essentially the same with some differences being cap values and resistor values.

Thanks,

GuitarG.


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## gtrguy (Jul 6, 2006)

GuitarG. said:


> With regard too your view on mods involving resistors and capacitor values, could you please explain too me why a Marshall Super Bass and a Marshall Super Lead, while having the same transformers and being played through the same speaker cab sound different? The circuitry is essentially the same with some differences being cap values and resistor values.


I believe Bill was referring to cap and resistor types and not values. Changing values _is_ how you can modify your amps to sound different. That's the difference between your Super Lead and Super Bass example, some (relatively minor) differences in component values in the preamp and the negative feedback circuit if I recall....


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## GuitarG. (Apr 1, 2010)

gtrguy said:


> I believe Bill was referring to cap and resistor types and not values. Changing values _is_ how you can modify your amps to sound different. That's the difference between your Super Lead and Super Bass example, some (relatively minor) differences in component values in the preamp and the negative feedback circuit if I recall....


Could be. I would say that changing values will attenuate or boost certain frequencies in different parts of the circuit with regard too how it interacts with different parts of the circuit. This in turn will effect how the speaker responds with changes in electron flow within the circuitry.


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## Wild Bill (May 3, 2006)

GuitarG. said:


> Could be. I would say that changing values will attenuate or boost certain frequencies in different parts of the circuit with regard too how it interacts with different parts of the circuit. This in turn will effect how the speaker responds with changes in electron flow within the circuitry.


Of course changing values changes tone in a tone circuit. That's how the circuit works! A resistor attenuates all frequencies equally. A capacitor is like an AC voltage resistor, only with AC we call it reactance and not resistance. To a higher frequency a given value of capacitance looks like a lower number of reactance ohms than a lower one. By doing a bit of math you can set the mid points of a tone control and how fast it changes its effect on frequency, which we call its slope.

However, as far as the sound of different materials, I stand by my position. It's possible that some caps may show a very slight difference, due to a fixed internal reactance called ESR, which stands for "Equivalent Surge Resistance". Rarely could a human ear hear much difference, particularly with a guitar amp. If you change out such caps you might notice an overall volume change, since as I said resistance is equal across all frequencies but the idea that it might make a "subtle change in the highs and more emphatic mids" is just advertising mojo coming from people who have never opened an electronics textbook.

Again, there is no sound inside a guitar amp circuit! NONE of the parts deal with acoustic energy! It is all electricity, or electron flow. A tube, capacitor or resistor has no way to tell the difference between an audio signal, radio, video or a control voltage for the speed of a motor. Nor does it care!

The materials do not vibrate with sound energy, like rosewood versus ebony on a guitar neck. Again, they deal with electrons. It's not sound until the speaker cone moves some air! That's why a speaker change can make such a HUGE difference in tone! All the materials and the method of construction DO deal with acoustic energy!

No, so-called differences in caps and such are purely psychological. Virtually NEVER do we hear about any scientific, blindfold tests!

Even if these myths were true, why on earth would someone take an amp like a classic Fender or Marshall and change all those parts to give a more "hifi" sound? Why not just buy a home hifi amp and plug into that?

That's the sound of the Boston Philharmonic Orchestra, NOT rock and roll!

WB


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## gtrguy (Jul 6, 2006)

I thought ESR meant 'Equivalent Series Resistance'?


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## GuitarG. (Apr 1, 2010)

Sorry Wild Bill, I misunderstood what you were getting at. I am not familiar with the CC2 or the mod the emailer was talking about. Most mods I know of usually consist of changing values too impact changes in the overall tone of an amp. I assumed the emailer was looking for different brands including alternate values from what the amp is stock.


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## Wild Bill (May 3, 2006)

gtrguy said:


> I thought ESR meant 'Equivalent Series Resistance'?


You're right! Remind me to drink coffee first and type later!


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## Wild Bill (May 3, 2006)

GuitarG. said:


> Sorry Wild Bill, I misunderstood what you were getting at. I am not familiar with the CC2 or the mod the emailer was talking about. Most mods I know of usually consist of changing values too impact changes in the overall tone of an amp. I assumed the emailer was looking for different brands including alternate values from what the amp is stock.


I think you're right in your assumption. Not being technical, he seemed to think that the brand or type was more important than the value!


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