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Mixing capacitors

1/7/2006 9:09 AM
Kevin St.Pierre
Mixing capacitors
I have read that some builders recommend using a variety of capacitor brands-Sprague,Mallory, etc-in an amp to achieve a broader spectrum of tone.I guess using the same type throughout an amp would cumlativley accentuate that brands voice? Just as using a mix of preamp tubes can add up to a fuller sound.Does this idea hold up? I have also read of using caps in parallel to do the same thing.What is the end result of using different values in parallel to get a desired capacitance,if the values used are unequal to start, is the end result an equal mixing of the 2 or weighted toward the higher or lower of the 2 values?I hope I stated this clearly,It makes some sense to me but I am not all that knowledgeable in component function.
1/14/2006 7:12 PM
Steve A.
Mixing capacitors... and OCB!
    FWIW when I was working on my Peavey Classic 30, at one point I decided to replace ALL of the tone and coupling capacitors with Type 418 Orange Drop caps, which is a fairly smooth polyester cap. The results were a bit shocking... the sound was very powerful, but with not a hint of brightness at all. It would be an interesting amp for the Bizarro World, but not that useful in this world so I changed a few of the capacitors back to polypropylene and the brightness came back.  
    Not that you always need to mix and match caps, but like an artist and his pallette, if you feel the amp is too bright you might put in one cap, and if you feel the amp is too dark you might put in a different one. It sure beats smashing your head against the wall and starting over from scratch... ;)  
    That being said I do like to mix in something like a 1uF poly cap on the cathode of a preamp tube, adding it to something like a 2.2uF to 10uF electrolytic cap. To my ears it sounds better than just the electrolytic cap by itself, and I've noticed it used on a lot of boutique amp schematics.  
    I think that a lot of amp building techniques indicate obsessive compulsive behavior: something worked once so we will keep repeating it, hoping that it will work again. We might eventually discard a particular technique if it seems like it doesn't help at all, but until then, what the heck... :D  
Steve Ahola
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1/15/2006 1:59 PM
Kevin St.Pierre

Thanks Steve,Well said and I can identify with the O/C reference.I will try mixing caps on the cathode,interesting idea.By the way I have found your site to be a constant reference source.Well Done and thanks for the work and knowledge you make available.-Kevin
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