25v caps to replace old ZX ones, is this ok?

[jamie6662]

So I have taken my amp to have the caps done. The guy who's doing it has been hand building high end home speakers and amplifiers for around 40 years so knows his stuff but doesn't normally do car audio he says the caps he wants to put in it are 25v 85c 4700uf he reckons itsbetter with 25v cap as it won't work to hard and that 85c should be adequate as it shouldnt get near that temp
Will this be fine or is there any major reason I should get the nichicon ones myself as I have a feeling he uses 25v ones and can get them easier.
Other question is the yellow topped adjuster on the board, is this the dc offset? Or bias? And should it be adjusted? He really wanted a wiring diagram before adjusting it so wanted me to double check
Cheers

[zeropoint0.5]

are we talking about the ps caps or also the railcaps ??

For the ps caps, i even put in 35V, so the 25V is not a problem. i would use 105°C, not 85°C, and 2200mF or more....

for the rail caps they have to be 50V or more, 2200mF or more, better use 105°C also (unless what is in is 85°C)


R130/R230/R330/R430 are the bias pots......

please contact Eric D or Valeks before doing mistakes.......

[StillKeen]

I just bought the caps that Eric recommends from digikey for the PS caps. For the $15 it costs (4 caps + shipping ... About $15), it means you know they'll work for sure. Have you looked at his guide? I followed it exactly, and it all four amps are successfully upgraded now.

[Eric D]

25V caps will work, you will just get more capacitance from 16V ones operating closer to their rated voltage. But, I am guessing a 25V cap with 4,700uF will still have more capacitance at 12V than the original 16V 2,200uF caps did.

105c caps are preferred over 85c, as many PG amps can run hot under load.

The yellow pots on the board are the bias controls. You should only adjust them if they have been messed with prior and need to be put back, or if you had to replace parts in an output channel (this can move the bias point).

[jamie6662]

Yeah sorry it is power supply caps, did read Eric's tutorial I asked for those caps recommended but its the guy doing the job for me that mentioned 25v ones but I think its alot more to do with he can source them easily . I will see if he can at least me 105c ones if not i will order Nichicon ones myself . As for them being bias pots will leave them alone then. Thanks guys

[freshkryp69]

Eric D, can you elaborate on the Bias just a bit. Is there ever a situ where you want it bias towards class A, say for tweeter use and biased toward class a/b for mid or mid bass use. and is there any benefit in rebiasing due to the use of certain speakers? A set bias cant work optimally for every speaker can it? Im aware of what the bias does when its biased towards class A it heats up big time.. know what im saying?? Or is the optimal bias setting just good for the amps all around efficiency at all loads and any ohm speaker it happens to be running?

[Eric D]

Honestly, I don't think the bias is all that critical on a PG amp. But, this is my opinion, I have no science or facts to back it up.

I have listened to PG amps with the bias all the way down (should technically be Class B operation), and they sounded just as good to me as they did with the bias properly set.

My best guess as to why I found this to be, is PG has enough feedback in their design it smooths out the crossover distortion on its own.

As far as general amp design goes, I would personally prefer to use a single device class A design over a complementary device design. With a single device design, the transistor sits across both rail voltages, and is entirely responsible for the output to the speaker. With a complementary device design, this often is not the case, but can be the case. Either way, I still think "less is more" when it comes to parts count in the signal path, and a desire for top sound quality.