The effect of different value coupling capacitors?

[paulluvsmusic]

Hi, recently i have moved on from just tube rolling my 300b set amp and have started replacing the coupling caps with better quality ones, the result was amazing, night and day. I replaced them with Mundorf Silver/oil of the same value. My question is what would happen if I tried different values. for e.g On the huge power output caps they have .33uF,what would happen if I put 1.5uF caps there instead. Would I do damage and what effect would it have on the sound?
Cheers,
Paul

[flatheadmurre]

A coupling cap is a part of a filter and is if the amp is well built calculated to the right value.

Changing value without the change of any other major parts as OPTs are not adviceable.

Going from 0.33 to 1.5 will take your filter down into subsonic and probably damage your OPTs or in best case add distorsion.

Stick to finding a better brand of tubes and caps if your not interested in a rebuild.

[paulluvsmusic]

Thanks you for your reply, very new at this. Another thing i have been considering which i read, Is adding 0.01uF in parallel with the caps i replaced.I have read that it adds more subtle detail. Is this a safe mod? He called them shunt(tweeter) capcitors.

[flatheadmurre]

A cap has a tolerance about 5% so as long as you keep in that region it´s safe.

Using several small versus 1 big and the mix is a never ending debate.
.
If you like what you hear use it.

We all have different preferences and like different sounds.

[paulluvsmusic]

Cheers. I might look into buying a book on SET amp building. Would love to build a amp from scratch. Thanks again.

[flatheadmurre]

A good book is an excellent start.

Search the forum there´s several good basic amps around.

Good luck

[commstech]

Originally Posted by flatheadmurre

A coupling cap is a part of a filter and is if the amp is well built calculated to the right value.

Changing value without the change of any other major parts as OPTs are not adviceable.

Going from 0.33 to 1.5 will take your filter down into subsonic and probably damage your OPTs or in best case add distorsion.

Stick to finding a better brand of tubes and caps if your not interested in a rebuild.

i do not think increasing a coupling cap could possibly damage output trans. the only damage i can think of is the wallet.

[jeffreybehr]

Originally Posted by paulluvsmusic

On the huge power output caps they have .33uF; what would happen if I put 1.5uF caps there instead. Paul

Is the 0.33 in parallel with the PS cap? If so, it's what is called a bypass cap, and increasing its value probably would be beneficial. Mundorf S/Os might be rated for 1200VDC, but they're lots more reliable if kept at lower Voltages. What's the Voltage across that 0.33?

[flatheadmurre]

Originally Posted by commstech

i do not think increasing a coupling cap could possibly damage output trans. the only damage i can think of is the wallet.

Depending on how good and what size the OPT is lowering frequencies will lead to saturation in OPT.

Driving the OPT into saturation will end up in overheating and shorting something.

The question was about coupling caps not PSU caps if i understand it right.

[Frank Berry]

If your amplifier has good low frequency performance with the existing caps, increasing the value of the coupling caps will not make a drastic improvement. As flatheadmurre stated, it may create OPT saturation problems at very low frequencies.
Going from .33uf to 1.5uf is a huge jump.