Amp Capacitors, their differences and tonal affects?

[imsilly]

Lately I have been finding a lot of contradictorary opinion on capcacitors in vintage amps.

So I want to clear up a few queries:

Which particular caps need to be replaced and how often?

Which caps have the largest tonal effect on an amp?

Which modern caps give the most authentic tweed and blackface tones?

 

[muchxs]

Lately I have been finding a lot of contradictorary opinion on capcacitors in vintage amps.

So I want to clear up a few queries:

Which particular caps need to be replaced and how often?

Electrolytics in the power supply. How often do you replace them? It depends. It depends on age, brand and whether or not the amp has been used. Electrolytics "form" when voltage is applied to them. I can watch them "form" on my tester. An old cap will start below value and gradually rise hopefully to full rated value. Electrolytics tend to hold up better in amps that are used at least once a week. Stick it in a closet for ten years, the electrolytics "forget" that they're capacitors.

If you want your amp to perform consistently you may want to consider a cap job every ten years whether it needs it or not. The degradation in tone is so gradual you probably wouldn't notice it until it became really bad.

Which caps have the largest tonal effect on an amp??

ALL of them?!!

Seriously, if the electrolytics in the power supply are past their prime the amp will have no balls at all.

If the electrolytics used as cathode bypass caps are past their prime the voicing of the amp will drift from what the manufacturer intended. It may drift in a direction you prefer, it may not.

Leaky coupling caps dump DC into the next tube stage. DC on the grids makes all sorts of funky noises.

Drifted tone caps change the center frequencies of your tone controls.

Which modern caps give the most authentic tweed and blackface tones?

I shouldn't touch this with a ten foot pole!

It depends on what you mean by "authentic tweed tone". By "authentic tweed tone" some people mean how the amp sounds with dead electrolytics, drifted or leaky coupling caps, drifted resistors, maybe tubes well past their prime and a funky dried out old speaker. The amp isn't the way Leo intended it. If I serviced that amp you might complain bitterly because it sounds very different compared to before I worked on it.

Which one is the "authentic tweed tone"?!

 

[imsilly]

When I say "authentic" I should really say expected or cliched tone. Like you expect Fenders to sound cleaner and brighter as they go from Tweed, to Brown, to blonde, to blackface and finally silverface.

My issue is you oftern see people appauled that someone has popped some Orange Drops into a tweed. Or some other such combination. The idea is the amp goes in sounding like a blackface or a tweed and comes out sounding like one. Or even better sounding more like that cliche of an amp you recognise from recordings or that one time a friend of your's let you play on his amp or some other such occassion.

I also realised that certain manufactures of caps claim to sound like this or that old cap that is no longer manufactured. I mean everyone has seen at least a picture of an old tweed filled with Astrons and wondered if there was someone who manufactured a similar cap now. Or those blue molded Mallory caps in blackfaces.

On a final note, it would also help me altered the tone subtley to my own specs if I knew replacing this cap with that cap would have this effect.

 

[markw51]

Like muchxs sez, the electrolytic caps are the ones that don't last for many years. However, the non-electrolytics do - maybe they never need to be replaced, and unless they need to be replaced cuz they are shorted or open, I wouldn't. That's my take.

 

[muchxs]

When I say "authentic" I should really say expected or cliched tone. Like you expect Fenders to sound cleaner and brighter as they go from Tweed, to Brown, to blonde, to blackface and finally silverface.

I'll simply say there's a lot of misinformation on thios topic. Guys read something on one website, believe it to be true and mouth it on another website.

Common misconceptions are:

There are "right" or "wrong" speakers

There are "right" or "wrong" tubes

There are "right" or "wrong" capacitors.

Sure there's "right" or "wrong", say you stick a 6BQ5 in a 12AX7 socket or replace a .1uf@400v with a 1uf@40v. Swapping the same value for the same value, though? Some people think it's magic, stick EL34s in your Twin and it's a Marshall. No, it isn't.

The final answer is that your tone is your tone. If your tone comes from a cheap guitar with rusty strings played through an IC amp powered by a battery made out of a potato... that's your tone. Who am I to argue?!

My issue is you oftern see people appalled that someone has popped some Orange Drops into a tweed. Or some other such combination. The idea is the amp goes in sounding like a blackface or a tweed and comes out sounding like one. Or even better sounding more like that cliche of an amp you recognise from recordings or that one time a friend of your's let you play on his amp or some other such occassion.

Many claims of "tone" originate in commercial interest. There's rarely any science involved. My favorite bogus claim...

A certain transformer manufacturer claims their expensive transformers transform a certain cheap amp. It wouldn't have anything to do with the three essential resistor changes, would it?

I also realised that certain manufactures of caps claim to sound like this or that old cap that is no longer manufactured. I mean everyone has seen at least a picture of an old tweed filled with Astrons and wondered if there was someone who manufactured a similar cap now.

I certainly hope not.

Those old Astron electrolytics are very poorly made compared to modern electrolytics. It's not that they weren't the best technology available at the time, it's just that there's been 50 years of technological progress since then.

Joke: John 5 should play through old tweeds with original Astron electrolytics. Because they're Zombie caps! If they're not dead yet they're living on borrowed time.

Or those blue molded Mallory caps in blackfaces.

You're really splitting hairs when it comes to differences between one replacement coupling cap and another. The usual situation is to replace a drifted component with one that's in spec and say, "Wow! Those caps sure made a difference!" Or make other changes while you're in there.

On a final note, it would also help me altered the tone subtley to my own specs if I knew replacing this cap with that cap would have this effect.

You'd be altering the tone very subtly. Having said that:

I wish I could get old yellow Astron coupling caps at a decent price. It sidesteps an argument if nothing else. Replace Astrons with Astrons in pre-63 Fenders. That's signal caps only. 50 year old electrolytics are for display only.

Lacking Astrons I reach for Cornell-Dubilier "greenies" or Sprague 6PS "Black Beauties". All tested and spec'ed, of course.

I have absolutely no problem using 715P or 716P "orange drops". As far as I'm concerned they're a perfectly acceptable replacement for "blue caps".

Original "mustard" caps are still available for old Marshalls if you're willing to pay the price.

 

[tonebro]

I'm about to build my second amp, a 5E3... and am considering using Sozos. I also have some SBE 6PS Orange Drops, too. Any comments on either or?

 

[muchxs]

I'm about to build my second amp, a 5E3... and am considering using Sozos. I also have some SBE 6PS Orange Drops, too. Any comments on either or?

I've used 6PSs in 5E3s. No complaints. You can easily build a great sounding Deluxe with those. If you have a nagging feeling that maybe you're missing something you could build another Deluxe with Sozos...

 

[Wicked-T]

Very interesting thread.

 

[Staggerlee666]

According to the owner of Victoria Amps it is the resistors that have quite an effect on tone. Old resistors introduce distortion in the signal that is an integral part of the tweed sound.

 

[Silverface]

The original questions are not ones that can be covered completely in a forum.

If you Google the subjects "coupling capacitors" and "tone capacitors" AND the particular brand (or general type) and model of amp you are thinking about you can find hundreds of various threads and posts on the subject. There are NO "rules" - tone is subjective and there are as many opinions as there are techs.

Personally I don't use any of the orang drop types in Fender amps. I find all to be slightly on the brittle side with an overly bright top end. I stick with Mallorys, Sozos or my stash of vintage blue tubular and other caps.

As far as Electrolytic filter caps, one fairly well-accepted rule of thumb is that 15 years is the maximum service life for those caps in amps that have been played regularly; OTOH, if an amp has been sitting for extended periods the caps can crystallize early and cut that time in half or less. Many amps go far beyond that without problem, but caps can blow without warning - usually when the amp sounds fine.

Cathode bypass caps, which normally are subjected to very low voltage, can last much longer. When they fail usually the amp becomes noisy or gain decreases.

 

[JD0x0]

Electrolytic caps are the ones that go bad relatively quickly.

'Paper in oil' are also known to leak as they age.

Ceramic caps can be noisy and microphonic.

There's definitely measurable difference in tone with different cap composition. For example, ceramic coupling caps show 3rd and 5th order harmonic distortion, while polystyrene, of the same value, in the same circuit showed virtually no distortion.

Polyproylene are generally 'brighter' to my ear than polyester caps of the same values.

Difference is notable, but not incredibly apparent.






There's no magic cap. Different caps work better/worse for certain styles and ears. People are often concerned with using the same cap type throughout the amp. Unless, you're mass producing, there's a bigger advantage in mixing cap compositions. For example. I'll often use Polyester in preamp stages and polystyrene in power amp stages, and places where stability is favored. One of my amps has Polypropylene on one side of the phase inverter going to the power tube, and polyester coupling caps on the other side of the PI going to the other power tube. I thought it made the amp sound thicker and more complex than having the same composition. I keep polystyrene, ceramic and silver mica caps in pF values, because they're great for tuning the top end of the amp, in the tone stack. Ceramic is good for the grainier top end, like a marshall, while Silver mica has a more 'hifi' like top end, very bright (brittle) detailed high end. Polystyrene sounds a bit 'smoother' than silver mica, not quite as detailed on the highs.

I got to do a lot of testing by ear, with some of my prototype amps.

Old resistors introduce distortion in the signal that is an integral part of the tweed sound

It's not 'old resistors'
It's carbon comp resistors, which will distort with a large voltage drop across them (plate resistors are the only place where this effect would have any difference) The disadvantage is more drift with CC, more risk of failure with CC and more noise (hiss) with CC resistors. If you're using CC's in other areas of the amp, besides the plate resistors, you're basically just adding to the noise floor, IMO.

 

[jackleg]

Electrolytic caps are the ones that go bad relatively quickly.

'Paper in oil' are also known to leak as they age.

Ceramic caps can be noisy and microphonic.

There's definitely measurable difference in tone with different cap composition. For example, ceramic coupling caps show 3rd and 5th order harmonic distortion, while polystyrene, of the same value, in the same circuit showed virtually no distortion.

Polyproylene are generally 'brighter' to my ear than polyester caps of the same values.

Difference is notable, but not incredibly apparent.






There's no magic cap. Different caps work better/worse for certain styles and ears. People are often concerned with using the same cap type throughout the amp. Unless, you're mass producing, there's a bigger advantage in mixing cap compositions. For example. I'll often use Polyester in preamp stages and polystyrene in power amp stages, and places where stability is favored. One of my amps has Polypropylene on one side of the phase inverter going to the power tube, and polyester coupling caps on the other side of the PI going to the other power tube. I thought it made the amp sound thicker and more complex than having the same composition. I keep polystyrene, ceramic and silver mica caps in pF values, because they're great for tuning the top end of the amp, in the tone stack. Ceramic is good for the grainier top end, like a marshall, while Silver mica has a more 'hifi' like top end, very bright (brittle) detailed high end. Polystyrene sounds a bit 'smoother' than silver mica, not quite as detailed on the highs.

I got to do a lot of testing by ear, with some of my prototype amps.




It's not 'old resistors'
It's carbon comp resistors, which will distort with a large voltage drop across them (plate resistors are the only place where this effect would have any difference) The disadvantage is more drift with CC, more risk of failure with CC and more noise (hiss) with CC resistors. If you're using CC's in other areas of the amp, besides the plate resistors, you're basically just adding to the noise floor, IMO.

thanks for the demo... i hear a startling difference between the two fender amps.. the second amp you played sounded much brighter and defined , to me. i still don't know which of the two i would keep, but i lean toward the second example. thanks

 

[Henry Mars]

There are differences in cap types. How much these differences effect the sound of the amp is another story.

set up a test circuit with a 1Khz square wave. resistor in series with the generator and output across the cap ... ( obviously simple ). Then substitute different types of caps with the same tolerance and value in the circuit and observe the integrated output for each one. the difference in the output waveform will tell you the story. Crude but it will illustrate the point. I became aware of this when I was designing low frequency trigger ckts. How much it effects audio ckts is another story ... but there is some difference between cap types.

 

[Middleman]

I agree with muchxs on every point except respectfully, the use of orange drops. This comes from an overhaul I had done on my vintage Vibrolux and the amp just sounded hard and edgy. Orange drops were the best alternative at the time i.e. 70s and 80s when a lot of original Fenders started needing cap and filter work. Today you have better alternatives from Fender and Vintage as well as some other companies to get replacements close to original performance.

Last year I used a combination of Fender and Vintage caps to replace the orange and also components in the tone and PI section of the amp that had drifted. I also used Astrons for the filter caps. These provided a much truer original tone of the amp similar to it coming out of the factory.

On the recommendation of Dave Pearlman, the head of Pearlman mics who builds vintage era replicas of early Neumann and Telefunken mics, I bought a bunch of carbon comp resistors to replace the original ones instead of using the metal film resistors so common today. I did use a couple of the metal film on the grid resistors (fire resistant). Dave felt the use of original era type resistors can play a factor in the tone of the amp. I have to say the carbon comps are getting harder to find and they are not always in spec when you to find them. I agree with the comment above of their propensity to drift.

The amp sounds gorgeous by the way with all these changes.

 

[bent-string]

I want to reopen this thread about caps, I've been restoring a 53 Fender Deluxe and
found a working set of Astron caps. They even test better than my other caps but
having them in the amp for a few days I find them bright sounding is this the way
they should sound?

 

[tubedood]

One thing about my stash of old capacitors is they might have spot on values for the capacitance but once they get charged up they are leaky with the DC voltage.