Ceramic caps -modern vs old

[guavatone]

I am trying to restore the ceramic caps on an '67 Bandmaster amp since I did not like the sound of the Silver-Mica caps nostly in the EQ circuits. Are the new ceramic caps(on right) similar in sound to the old ones (left)

The new cap is a Y5P 1000V

 

[bcarso]

Oh please don't change out silver micas for Y5P's! They are about the poorest caps you can get---lossy, piezoelectric, very large temperature coefficient, yuk.

I don't know what you disliked about silver micas, or how you determined that they were responsible for whatever it was you didn't like, but high-K ceramics are at best useful for bypassing.

 

[guavatone]

You may be right bcarso, As soon as I replaced all the blue caps with orange drops, replaced el-caps, fixed adjustable bias, and new PWR xfmr I loved the sound.

Then I replaced ceramics with silver mica caps, change the feedback to 1.5 or 1.6 from 820 Ohm, changed phase inverterinput cap. I wasn't too happy after this and I was thinking the silver micas had the latgest impact. It now sounds too sterile and less present. I'd rather not argue on preference of sound. I was wondering if there was much of a difference in the sound of old vs. new ceramics.

 

[bcarso]

I don't know about old vs. new ceramics, but there are some very low quality ceramics coming out of China etc. sometimes these days. Reputable manufacturers should provide decent parts though.

A batch of bad ones cost a certain megacorp about 2 million dollars when some turned into little ceramic heaters inside a plastic speaker. Most of that recall/rework money was reimbursed by another megacorp who had put the circuit boards together and selected the bargain basement supplier of the caps, but it was a harrowing time. It was not too much of a stretch that it could have started a fire and killed someone.

 

[Gus]

Silver Mica can sound "bad" in a guitar amp IMO its a guitar amp a producer of sound not a reproducer(HiFi).

The piezo effect(science) seems to be some of the "Magic" in guitar amps at certain sections of the circuit the lattice twists plate spacing changes and has a time delay. The voltage difference seems to have an effect on part of the "sound" the greater the voltage the bigger the change between the ceramic cap plates.

Change different lower value caps < 1000pf in certain parts of a guitar amp circuit that has larger signal swings or greater DC voltage difference between plates.

 

[Svart]

Y5P... i second that YUK!

today there is no excuse for the DIYer to buy such crap. you aren't going to save much money by going cheap when you are only buying a handful.

but.. I see you mentioned Orange Drops.. those are FILM caps not ceramic. if you used the polyester film caps this is likely what you like about the audio. ceramics do tend to be sterile and "brittle" sounding compared to the film's smoother, mushy sound.

 

[PRR]

> ceramics do tend to be sterile and "brittle" sounding

You can't lump all "ceramics" together.

As Hardy says, the small ceramics are nearly "perfect caps" except that they only come in small pFd, to 1,000pFd. (Of course in a gitar amp, perfection may not be the goal.)

As you go to 0.01 and 0.1mFd, the good glassy ceramic makes huge caps, so they use exotic compounds doped with loose molecules to increase the capacitance/size. These may be fine bypass caps, and in RF work the small size (low inductance) may be just as important as a high (but wiggly) capacitance. But 0.01uFd ceramic is one of the few caps that I can hear (most caps are all the same to me).

I don't know if old is different from new. I thought once they found a recipe that was useful, they gave it a code-number and stayed with it. (While the code strictly specifies tolerance and variation bands, I'm pretty sure they find a recipe first and then draw the specs around what the recipe gives.) Of course cap geeks must be constantly tweeking the fudge, and low-bid factories may mix the goo a little carelessly.

But I note that you seem to have replaced Z5U(?) with Y5P. This is like baking Chicken Cordon Blue with duck or pigeon... it's gonna taste different.

I can hear Z5U, but it is not necessarily offensive. It may be part of the BandBlaster tone. Try the original ceramic, not another very-different thing that happens to be ceramic technology.

 

[Svart]

True PRR, however I think the "sterile/brittle" sound is likely more the true sound of the signal, but the films tend to give the audio a more aural friendly nature even though it may be a modified version of the true signal.

As we've discussed time and time again.. What it sounds like is more important than it being a true representation of the signal in most instances.

 

[Gus]

To be clear I did not mean all ceramic caps are bad or good for a guitar amp. I was hoping people would just try different types to learn for themselfs.

The caps are cheap

More doing/learning less posting

I gave away some big hints in my post.

Guitars amps, BMPs even tone caps in guitars with high output pickups.

 

[John Hardy]

Please refer to page 8 (the back page) of my 990 data package:

http://www.johnhardyco.com/pdf/990.pdf

You will see that there are several types of ceramic dielectrics, the most common three types being the "COG" or "NP0", "X7R" and "Z5U". The COG/NP0 type is far superior to the others because the ceramic material is pure. The other types have additives in the ceramic to increase the volumetric efficiency (more capacitance in a smaller space) or to introduce a deliberate temperature characteristic. The additives cause an increase in distortion, so they are generally not good for audio circuits where they are part of an EQ circuit.

The COG/NP0 type is available in values from a few picofarads to more than 0.1uF. They get to be expensive and relatively large at those high values, so they are not as practical for EQ circuits and other audio related functions where a film capacitor is smaller, cheaper and very good (depending on the type of film).

John Hardy
The John Hardy Co.
www.johnhardyco.com

 

[Gus]

Did anyone read the posts I wrote?

Do some tests and learn something CAPS are cheap, makeup your own mind heck don't even believe me.

John Hardy gives away good info, not all ceramics are the same in sound.


Soundguy has heard an amp a homemade guitar and a few effects of mine pick your caps for what you want in the sound but it helps to try a bunch of cheap caps to learn.

FWIW I will use some caps I would never use in a HiFi in effects, guitar amps, guitars etc.

guavatone noted the replaced caps did not sound good CERAMICS can add a good thing to the sound IMO in certain places.

 

[dabo]

I agree with Gus and will add my comments.
I once rejected "bad sounding" caps out of hand on principle (and snobbishness) until a ceramic cap was the magic fix for and amp that sounded strange in the top end.
Voicing an amplifier is like cooking. You've got to know what the seasonings taste like before you can season to taste.