Ceramic vs Silver Mica caps in Fender amps

[Little Jay]

My Twin Reverb clone has silver mica treble and bright caps, also the small caps in reverb and tremolo-circuit are silver mica. Most amp books recommend to replace the ceramics for silver micas.

But that makes me wondering if ceramic caps aren't part of the Blackface (and Silverface?) sound, since all those amps use ceramics, and don't get changed out to preserve originality. Yet those amps are generally considered to be the Holy Grail in clean sound (never had the change to play one unfortunately).

I know the difference would probably be subtle, but I'd like to hear some experiences and opinions about ceramics vs silver mica.

 

[meric]

There is no difference in the sound. A capacitor does a specific function. It is the circuit that determines the sound not the individual components.

 

[printer2]

There is no difference in the sound. A capacitor does a specific function. It is the circuit that determines the sound not the individual components.

Actually, they just might.

There is a little more to a capacitor than just the uF rating on the part. Some are more stable as far as temperature is concerned, some change value depending on the dc across it, a whole host of issues. Ceramics have a bad rep but this is mainly due to using cheap ceramics. There are others made of different dielectrics that are more stable than other types of capacitors.

http://www.theeestory.com/topics/9505

 

[SoK66]

To my ears mica caps have a little less edge to them. I always try to replace vintage amp ceramics with either NOS (if I can find ones that haven't drifted) or modern production equivalents.

 

[Wally]

+1 with SOK66. I find a warmer, smoother high end with silver mica. I have even made the change for a customer...just the one change...and they heard the difference...playing there own guitar before and after teh change....professional player who is very attuned to what his DR's do.

 

[backline]

.....

 

[Little Jay]

Interesting replies! I think I'll just order some ceramics and see for my self. I was always under the impression that the type or brand of cap would not be audible, but I experimented with the mid and bass caps and that did make a difference to my ears (i had ODs, but TAD 'mustards' sounded better to me), so that's what got me thinking about the treble caps as well!

 

[alnicopu]

There is no difference in the sound. A capacitor does a specific function. It is the circuit that determines the sound not the individual components.

I have a nephew at Ga Tech. He's an engineering student and bass player. He and a guitar playing professor of his tested everything from the little .99 cent green ones to paper and oil and plotted them as well as recording and playing them back as a little project with an amp. They couldn't hear anything different. He said the graphs they printed out could be overlaid with one another, drawn over with a sharpie marker, and touched all the lines. The outliers were more out of tolerance than the others.

Don't mean to sound argumentative but sometimes i think we hear what we want to hear. The guy here in Atlanta that used to build Zach Browns amps told me the same thing. He offers a choice at different price points on components. Most opt for the more esoteric (expensive) stuff mainly for resale value.

 

[backline]

IMHO...if you hear a difference...it is because there is a Difference In Capacitance while operating in the amp.
Caps do not have an audible frequency response...like a speaker.

A friend of mine recently bought a SF Fender in real good shape. It still had all those blue tube caps. Took them out...installed Mallory 150...sold the caps on CL for 130 dollars...he bought a new Weber Speaker with the blue cap money.
I just would not worry about coupling caps...unless it is in a valuable amp...where people attach A Lot of importance to that kind of "stuff".
good luck

 

[Ringo]

re blue Fender amp caps

Well it's his amp, but IMO he just devalued the amp as far as resale value by replacing those original blue caps if he ever decides to sell it down the road.

 

[Middleman]

Dave Pearlman, of Pearlman mics, and I had a conversation about this several years back. He was emphatic that ceramic capacitors are the soul of vintage gear. His recommendation to me was to replace the originals with similar i.e. ceramic. The "grain" of the sound, his words, was found in ceramic caps.

 

[backline]

Well it's his amp, but IMO he just devalued the amp as far as resale value by replacing those original blue caps if he ever decides to sell it down the road.

Like I say...if it were a "valuable" amp....
When he leaves this amp to his kid in 20-30 years...nobody will care what color caps are in a SF Bassman.
The only thing I did not replace was the choke and tranny set.
This guy gigs A LOT.
He wanted reliable.
It now has a turret board... all new parts ...including resistors...jacks...pots...tube sockets...and coupling caps.
It still sounds like a BF Bassman...and has a Bass Channel with more mids and gain...and actually sounds good with guitar.
The amp will go another 30 years...except for tubes.
best

 

[xenrelic]

For anyone coming across this post in the future:

There's a pretty considerable difference in blackface amps when you use Silver Mica caps in place of the 250pF ceramic caps in the tonestack. The amps lose a bit of their vintage sounding magic when you switch over to silver mica. They sound a bit more hifi which jazz players might prefer if that makes sense. The smoothness of the Silver Mica isn't as desirable in that part of the circuit for indie rockers and surf guys and I always prefer the old ceramic caps there for those types of music. The ceramics have a particularly pleasing rounder bass quality to them that lends a lot of character to the overall tone.

Ceramics are terrible for the vibrato circuit though, a lot of them are prone to ticking noises which is why I would avoid them in that part of the amp and opt for film and foil caps or some other more reliable type without noise issues.

 

[Antoon]

For anyone coming across this post in the future:

There's a pretty considerable difference in blackface amps when you use Silver Mica caps in place of the 250pF ceramic caps in the tonestack. The amps lose a bit of their vintage sounding magic when you switch over to silver mica. They sound a bit more hifi which jazz players might prefer if that makes sense. The smoothness of the Silver Mica isn't as desirable in that part of the circuit for indie rockers and surf guys and I always prefer the old ceramic caps there for those types of music. The ceramics have a particularly pleasing rounder bass quality to them that lends a lot of character to the overall tone.

Ceramics are terrible for the vibrato circuit though, a lot of them are prone to ticking noises which is why I would avoid them in that part of the amp and opt for film and foil caps or some other more reliable type without noise issues.

I recently heard exactly that same difference when comparing ceramic and mica caps in parallel to the pickups in my Tele. The difference between ceramic and mica was stunning in that particular application.

I cannot explain why but that is not that important to me. Maybe it is because a pickup or mic is so early in the signal chain. This guy Dave Pearlman that is quoted above, I tend to believe him when he says that in a mic or some other pickup, the soul of vintage gear is in the ceramic caps.

This goes sharply against the online forum dogma that "a cap is a cap" and within reason it is only the capacitance that matters. To me this seems not to be the case.

 

[Paul G.]

Ceramics are microphonic, even brand-new. They were absurdly cheap in the day, hence Fender used them wherever they could. Silver micas are not microphonic. I can hear a bit of difference in the top end, being very slightly less harsh and prefer them in the signal path. The difference is not huge.

In tremolo oscillators or as snubbers, there is no reason to not use them.

 

[Antoon]

Ceramics are microphonic, even brand-new. They were absurdly cheap in the day, hence Fender used them wherever they could. Silver micas are not microphonic. I can hear a bit of difference in the top end, being very slightly less harsh and prefer them in the signal path. The difference is not huge.

In tremolo oscillators or as snubbers, there is no reason to not use them.

I the tweed era Fender used a SM treble cap in the tonestack, probably because of the closer tolerance of SM. Not shure what cap was typically used in the BF era. They look like ceramic caps but they seem larger/thicker than the equivalen ceramic cap of that era.

 

[Henry Mars]

There is no difference in the sound. A capacitor does a specific function. It is the circuit that determines the sound not the individual components.

The do actually .... pump a square wave thru the same ckt with different capacitor types of the same value and observe the output .... wary the frequency ang watch the wave shapes. It tells the story. You have to deal with leakage, resistance and inductance as secondary properties. This will affect harmonic content differently in each case. In audio ckts there will be some effect. As frequency increases the secondary effects become more noticeable and different ckt models must be used.

 

[SnidelyWhiplash]

re blue Fender amp caps

Well it's his amp, but IMO he just devalued the amp as far as resale value by replacing those original blue caps if he ever decides to sell it down the road.

Depends on which blue caps. The amp in ? is a SF. Fender was already
phasing out the blue tubular Mallory type in the early SFs. By the early
70s, they were gone entirely.

 

[larsjm]

This is an old thread, but it has the correct topic for my reply, so let's not fill the Internet with tons of new threads covering the exact same topics over and over. There is nothing wrong with adding new information to old information if it's related. Let's try to reduce content, not create more of the same thing we all have to weed through.
With that out of the way, there is definitely a difference in certain capacitors in how they will sound in a circuit. It's not something you can measure with diagnostic equipment because those are just measuring frequency, voltage, current, leakage, etc, etc. It's the reason a tuner works for multiple instruments, but can't tell you what instrument it's tuning. It's just looking for the frequencies. But you can't tell me there is no difference between an "E" played on a guitar vs an "E" played on a trumpet. It sounds completely different even though it's the exact same note, same frequency, same pitch.
A trained ear can tell you the different sounds of guitars and pick out a Strat, Tele, Les Paul, 335, even though they're all guitars. Diagnostic equipment can't make that distinction. it's just frequencies to the equipment. It would tell you, they're all guitars. They're all the same.
It's the same principle with capacitors. Some of them are different "instruments". Just because a graph says it's the exact same frequency, voltage, capacitance; that does not mean the sound is going to be identical.
Case in point: some of the earliest recorded examples of a wah sound coming out of a guitar were when people would rapidly rotate their tone knobs and bingo; a wah-like sound. This does not work with all guitars though. Cheap ceramic or shiney green film caps don't tend to wah. I've tried it. But, I put in an old Ajax blue-molded cap like the ones Fender used in many of their 60's amps and viola; my tone knob on my guitar could produce a wah-like sound even though the capacitance was exactly the same as the cheap green cap I replaced. Obviously, the cap was doing something more to the sound than just passing frequencies. It is a different "instrument", different sound.