Building my Crack - Finally

[davew]

Thanks. I'll burn-in the amp with the stock tubes and see how it improves.

 

[George Napalm]

I had a similar problem with the driver tube (some 12AU7 I couldn't identify). I heard audible hiss and extensive burn-in didn't help. Since installing other tubes I'm amazed how dead quiet this amp is.

I'd suggest installing 47K resistors at the input jack between the solder cup and the hot for each channel that will help the balance of the PEC pot at lower levels.

-PB

Interesting! I have a slight imbalance at lower level too. Is this resistor supposed to change the taper of the pot somehow?

 

[Doc B]

Interesting! I have a slight imbalance at lower level too. Is this resistor supposed to change the taper of the pot somehow?

No, it cuts the signal down a bit so you can put the volume control at a higher setting where the two channel levels track better. Pots tend to get farther apart balance-wise at the low end of the scale.

 

[Doc B]

If you use a decent metal film resistor it should be fine, since that should be of a bit higher quality than the pot itself.

 

[George Napalm]

Ok! So to make sure I understand everything: "connecting solder cup and the hot" means connecting + and - of the input jack? I haven't seen the term "hot" before...

 

[davew]

Hot is an old school term for the positive side of a pair of terminals.  "... installing 47K resistors at the input jack between the solder cup and the hot for each channel ..." means remove the positive wire from the RCA jack center terminal (solder cup) and install the 47k resistor inline between the wire and the now vacant RCA jack center terminal.

------------wire-------->] RCA jack center terminal

becomes
                          47k resistor
------------wire----/\/\/\/\---->] RCA jack center terminal

I think there may be a picture of this buried in the gallery somewhere. If I find it I'll attach it here.

 

[George Napalm]

Thank you for the explanations. Now it's clear. No need to look for picture

 

[Doc B]

BTW - any relation to Wallace and Wilder?

 

[George Napalm]

BTW - any relation to Wallace and Wilder?

No, I was a big fan of death metal music at some point, especially the British band Napalm Death. I completely switched to classical music since then, but the nickname stuck. Moreover, George Rachmaninoff would sound too pretentious