Phase Inverter Cap

OrangeJTM46 · Post by **OrangeJTM46** » Tue 12/20/05 1:14 am

In the most recent 36W layout, there is a 47pF cap in the phase inverter section of the board. What is the purpose of this? I have not seen it in any other designs.

Post by **zaphod_phil** » Tue 12/20/05 7:51 am

Generally I hate trying to decipher layout drawings. Anyway, if it's between the PI anodes, then it's probably a "buzz cap", used to remove any high frequency buzzines or harshness.

KT77 · Post by **KT77** » Tue 12/20/05 11:23 am

Mrshall did this w/ a lot of their designs....to suppress osc possibly......it is useful for taking the edge out of a design (increasing the value will smooth tone of a 'grainy' amp)

47pF doesn't do much to a well constructed circuit
100pF is noticable tho......in a good way

johnny5 · Post by **johnny5** » Thu 01/12/06 6:45 pm

would this same idea work for a Concertina style PI? i imagine it would since it's doing essentially the same thing.

kd · Post by kd » Thu 01/12/06 7:55 pm

The JTM45 also uses that cap on the phase inverter.

Ken

JohnDandry · Post by **JohnDandry** » Mon 06/12/06 9:54 pm

Does the 100pf cap work in a 18 watter. I find my 18watt a little buzzy and harsh up high sometimes.

KT77 · Post by **KT77** » Mon 06/12/06 10:54 pm

try that or the Ruby mod (see downloads section)

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Phase Inverter Cap

Phase Inverter Cap

Does this work on a 18watter