Tone caps in an amp

[lerxst88]

OK if anyone reading this is a tone purist just leave now because I am embarking on a small project that would scare away many tone purists.

1)its not a pedal
2)is a cheapo crate solid state
3)its a simple question that will mostly get "well why bother?"

Because I have a soldering iron and nothing else to do thats why!

Ok rant over! So I want to muck around with the circuit of a crate GX-15 (yes the 15 watt solid state piece of crap everyone gets for their birthday when they first start playing guitar and then use as a test amp for new pedals) and I wanna make something useable or pretty cool out of it.

For solid state amps, the tone stack is usually 10x higher is cap values and 10x lower in resistance values. Stock the amp has a fender style tone stack but is using two ELECTROLYTIC 1uF caps for the bass and mid pots. Would replacing these with a proper polyfilm cap of equivalent value improve the tone you think?


for anyone that has kicked around this idea of modding one of these, adding "bright switch" caps (ala fender) works wonders! I forgot the values I put in yesterday but if anyone is interested, I can look for you!

Thanks!!!

[R.G.]

For solid state amps, the tone stack is usually 10x higher is cap values and 10x lower in resistance values.

The formal name for this is "impedance scaling".

Stock the amp has a fender style tone stack but is using two ELECTROLYTIC 1uF caps for the bass and mid pots. Would replacing these with a proper polyfilm cap of equivalent value improve the tone you think?

The tolerance on electros is often very sloppy. Will it change the tone? Almost certainly, as polys are usually 10% or better.

Will it improve the tone? I'll tell you that when you can write a succinct, accurate definition of the word "tone" as it applies to this amp. 

[lerxst88]

I mean improve the tone as in smooth out the sound and response of the amp. I only ask because most amps have poly caps and i wonder if electrolytics sound better or worse by comparison, similar to how ceramic and poly caps sound different.

[R.G.]

I get a little queasy in the pit of my stomach every time the "does X capacitor sound better than Y capacitor?" comes up.

Apparently the hifi subjectivists have convinced the entire world that any sound coming through a politically-incorrect capacitor sounds like what you scrape off your shoes after a walk in the park.

There are slight - as in tiny - differences in capacitors. They can be measured - if you have the right instrumentation to do so. Sometimes, if the conditions are right and the wind is from a favorable direction, they can be heard. This has been blown up into convincing people that capacitors not made with gold-plated platinum foil insulated by Dead-Sea-Scrolls papyrus and soaked in the liver oils of cod fish captured on the night of the spring solstice must always sound horrible.

After I post this, the back and forth on the "issue" will start up again here. 

Electros have a wide capacitor tolerance. Capacitor value/tolerance is a much bigger effect on perceived response than cork-sniffing subtleties of ill-defined tone. Polys are much tighter tolerance, and have less drift with temp and time.

"Smooth out the sound and response of the amp" is, alas, just as indistinct as "tone". Does that mean subjectively smoother sounding (as in, duller trebles, the other way to say that) or less frequency response variation from flat (bad idea in a guitar amp) or change the time response of the amp to a transient (which is tantamount to saying changing the treble AND phase response of the amp)?

There is nothing I can say here that will have any meaning to your ears. If you think you can hear the subtleties of differences between capacitors, buy one of each and sub them in until you get what you like. Be aware that this kind of getting what you want is one-way. That is, if you like the ceramic, it does NOT mean that ceramic caps sound better somehow than polypro, or mylar, or polycarbonate, or electro as a general rule. The sample size, both of numbers of caps and numbers of listeners is too small, and the test is not controlled.

You will get advice that X or Y is the best. If you truly, really believe one of these, go with it. It will make you happy that you have the "right" caps. If you tell anyone what your choice is, you will be excoriated by the True Believers in the other kinds of caps. So go, do what pleases your ear. The advice you ask for is not possible to give in any meaningful way in today's context.

[petemoore]

3)its a simple question that will mostly get "well why bother?"

Because I have a soldering iron and nothing else to do thats why!
  Figure out something else, that's what !
  Since there's a general lack of info regarding 'where to start' for rig improvements, seems like a good time to mention:
  Having 1 amp that works is invalueable, having 2 means you have a spare.
  Even with nothing else to do, the losses versus gains...ok, I can only say with a grain of absolution that differences will be small, much greater gains can be had elsewhere...ie it's workin' just fine and probably wont be any better, might be a lot worse.
  Cabinet, Speaker...amp [shoppin' the used stuff mileage has proved useful]. yupp, change the speaker/cabinet and you can expect at least a good bit of difference, a reputable one that's called 'upgrade' actually is.
  And does cost more than the caps maybe, but you'll run out of caps to change before the amp really surpasses itself.

[PRR]

> Would replacing these with a proper polyfilm cap of equivalent value improve the tone you think?

You could replace the caps and find out.

Probably faster and with more self-certainty and satisfaction than yakking about it.

My yak:

If the cheapo caps are really crap, even a good electro may be better.

If you have Golden Ears, the film caps may sound different. (But the large size may be a problem.)

I say "different", not "better", not only because "better" may be open to debate, but because things which may be clearly "better" for reproducing recordings (hi-fi) are sometimes boring for guitar amplification. Crate could have selected those specific electro caps FOR their "flaws" (though I bet price was the only object).

BTW: whenever you mod an audio path in a way that you THINK is better, and is not acutely worse, it always "sounds better to you". OTOH if you have a partner who can A/B the two versions while you judge, it may be hard to pick the "improved" one consistently. I have also seen cases where a modder rang all the changes, each result better than the last, and ended up essentially where he started.

> ceramic and poly caps sound different

Do not lump all "ceramic" caps together!

Ceramic, like electrolytic, or any insulator, is imperfect. BUT unlike simple plastics and Al Oxide, "ceramic" covers a w-i-d-e range of substances. Think of flower-pots, fine dinnerware, and rocket-engine seals. There are dozens of basic ceramics and any of them may be "salted" with odd stuff to modify the properties.

Ceramic caps below 1,000pFd are made with a pure glass-like ceramic and are very nearly "perfect". Even in high-precision applications they replace glass and silvered-mica.

Ceramic caps 0.01uFd and up are made with a "salted" mix, loaded with loose-end molecules. This gives a LOT more capacitance in less space. But the capacitance varies more with voltage (DC and signal), temperature, strain, frequency, etc. While I can _not_ hear most caps, I can hear the nonlinearity of an undersized X7R coupling cap. And I know players who prefer this sound.

[petemoore]

  Great stuff all the time PRR, great stuff here.
  I can hear the nonlinearity of an undersized X7R coupling cap.
  What is that^, and what was the application, gear for the testings ?

[tackleberry]

The whole tone thing you want to fix is just the nature of low end SS practice amps with small speakers. You could swap every cap inside for high end parts will it give the tone your hoping for unlikely. I have a little peavey rage practice amp. I have tried all sorts of pedals thru it and EQd it nine ways to sunday it still sounds shrill. I ran it once in stereo with my tube amp when I got a new stereo chorus. I thought something was wrong with the pedal it sounded so bad until I found a different amp to use in place of the rage.

If your bored and have a soldering iron build a pedal.

[petemoore]

 Just a note, low bang for bukk on these endeavors.
A larger speaker enclosure will extend bass response and make it sound like a different amp.
I haven't looked at the specs on that particular amp, but amps aren't so much problem as they used to be, noise is a good indicator of power supply quality, which is of course caps and transformers and...
  The platform that supports it.
  A working amp is a good thing.
  Any improvement in amplifier technology [such as a different amplifier platform with improved specifications via design/experience and related strategies] will be most limited with a mini-solid-openback cabinet.

[Brymus]

One thing I didnt see addressed.(not exactly)If so then my apologies.
If the amp in question is older,and I had one way back part of a beginer package I was given a long time ago.
I hated that amp,my 20 watt GX20M I love WAY better...The two are like night and day tone wise.
Anyway ,if its a fairly old amp just replacing the old electros in the tonestack could have a profound effect.
As they were junk when new,and dont age well at all.
So any cap thats new would likely sound better  Even electros

But I think Pete has the best suggestion > hook it to another cab for instant improvment.
That amp was made cheap for people to afford with their cheap entry guitar.The spkr was the bare minimum that would make noise loud enough for beginners to Rock N Roll
Basically they had to make it loud enough to be annoying so the target demographic would buy it,sound quality was not a concern for that amp.
But as said before so many times if you like the way your mods sound thats all that counts.

[Ronsonic]

I like the idea of replacing small value electrolytics with film. For <1uF the size isn't usually a problem. In a lot of pedals and circuits they do seem to sound better; clearer and more distinct. In most of the capacitor debates there is little to pick between the contenders in measurable specs, here the difference in ESR is substantial. Besides, small electro's are simply cheap and crappy things that I dislike just on GPs. I don't think any of the guys who are suggesting that such a change is pointless would ever use them in their own projects and products.

It's an inexpensive experiment. Have fun. Try tantalum if you like, yet another flavor to experiment with. Only a dimwit would spec one of those in an area where the exact value is critical, but I am aware of things like speaker crossovers where the ESR has been factored into the design process. I doubt these are going to be that critical and are likely just coupling caps where anything within shouting distance of the original value will be fine.

And even if it ends up making no difference whatever, well, it's not like you'll ruin this thing's collector's appeal.