Need assistance addressing hiss

[Grainger49]

That says your problem is between the input and the output tube.  Quite possibly in the driver tube.

[bjorgens]

Noise did not follow the tube

[Paul Birkeland]

You can put a big cap across -reg and Kreg on the A side.  I would try 10,000uf at 6-10V. 

[bjorgens]

will give it a try Paul...thanks
Acknowledging my own ignorance, could you briefly explain what you think is going on and what the cap will do? 

WRT to the leaking electrolytic on my PS board...any sage wisdom on how to get that thing off so I can replace it without pulling the whole board? 

b

[Paul Birkeland]

will give it a try Paul...thanks
Acknowledging my own ignorance, could you briefly explain what you think is going on and what the cap will do? 

WRT to the leaking electrolytic on my PS board...any sage wisdom on how to get that thing off so I can replace it without pulling the whole board? 

If the TL431 biasing the tube is being a little noisy, the cap across it will present a low AC impedance that will calm that down.

I'm still suspect about the leaky electrolytic, does it exhibit any signs of a bad cap?  The top of it should bulge out and rupture the plastic wrap if the cap is bad.

[Paul Joppa]

While we're at it, did the jumper solve the hum problem? I know, two things at once is confusing, but it's less long-winded.  :^)

[bjorgens]

PJ.
the jumper eliminated the hiss.  There was still a SMALL amount of background hum.  I did not have a chance to compare to the other channel, but will check tonight.

PB
WRT to the electrolytic, don't think the top is bulging (will reconfirm tonight), but the amount of fluid that cumulatively has come out seems pretty substantial.  Mind you... I'm not hell bent on pulling that PS board again.    I may just monitor it for a while and see if the seepage dissipates.  In the interim, I have some replacement 270uF's on their way form mouser along with the 10000uFs you recommended

b

[Grainger49]

The remaining hum might be banished by a fine tuning of the hum pots.

[bjorgens]

Hi Grainger
you mean with a DMM connected to speaker outputs and inputs shorted (as per normal), or is there another way to tune even further?

bryan

[johnsonad]

Grainger and I have ten turn pots in our builds. They won't get it any lower but they can find the sweet spot easier. You can tune by volt meter but I find it easier to tune by ear with my ear next to the driver.  I have the faintest of hum with my 95dB sensitive speakers.

[bjorgens]

Interesting... What pot(a) are you using?
Bryan

[bjorgens]

PJ
WRT hum...  In amp with jumper between terminals 7 and 10 near 300B, hum is negligible at best.  Is substantively less than other channel without jumper... This said, the other channel was pretty low to begin with.

I.e., the jumper completely eliminated hiss, and seems to have reduced hum as well.

PB
Electrolytic is not bulging so far as I can tell.

Bryan

[Paul Joppa]

Re: hum, that means the 2A3 is fine, and the hum is coming in somewhere earlier. Useful to know. Check the connection of 12AT7 pin 9 to the chassis ground as a first step. Ater that it gets harder, so maybe it's time to concentrate on the hiss first.

[Doc B.]

If that cap has leaked at all you really need to replace it.

[bjorgens]

Ok... Will replace the cap... Should have parts Saturday hopefully.

Will check the ground connection on the 9 pin and advise tomorrow

Thanks again folks for the help.
B