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Coupling caps, upgrade, similar values

Hi all,

One question I have with regards to changing or upgrading signal coupling caps in a preamp (or any amp in that matter). Replacing the cap with a capacitance value that is not identical to the original, but that of a similar value ... wouldn't this change the output impedance of the preamp, as well as bass roll off frequecy, sound etc, etc. Cos then you're actually changing two variables, brand and value ... so how can you make an accurate judgement of the difference in sound? eg. If the orignal coupling cap is a 5.0uf, and you change it to a 3.3uf or a 10.0uf ... what happens?

Sorry, but I'm all new to this. Thanks for your time.

Regards,
David
linnmaster
magnumpi205
504 posts
 
Cap value should stay very similar, say 5.0uf to 4.7uf and not change the voicing of the preamp.
Obviously the voltage value can go up but not down.
Changing the brand by going up the food chain will clean up the sound, darker backgrounds, etc. The increase in cap price will only give you an upgrade commensurate to the value of the preamp.
A Vcap will not make a Sony an Einstein but will make what you have better.
linnmaster OP
45 posts
 
thanks for your response Magnumpi205

Would 5.5 to 3.3 be too far and end up changing the voice of the preamp? I think currently the cap in there is a MIT 5.0.
optimationman
7 posts
 
Hi,
If you know the input impedance of the next piece in the gear lineup, you can calculate the needed value to prevent roll off and possible distortion. Google for this formula. It seems most gear is designed for very low input impedance, one size fits all. I find that most values can be reduced(I have all tube equip). I would think that going from 5 to 3 should only be a problem(sound wise) in the one in a thousand. That said, remember if you change that next piece of gear for something else, you need to qualify you choice of capacitance value for the new gear!
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