Cathode

[Atk1d]

I'm back, new question....

I am currently using a 6p7 Russian equivalent to a 6l6 which works great in this amp, as I pistes earlier sound is amazing! Like so many others I would like to try tube rolling, and install a true 6l6, and some EL 34 tubes. As of now when I install them sound is crackly, with some minor popping , to change the bias for thus amp requires changeling the cathode, this is where my brain turns to mush
I'm not sure I understand George's chart fully, if I Gould ask for a little help with this, I would for ever great full !

Cheers
Dale

 

[vinylkid58]

Are you using the 6p7's in adapters, because the pin-out is not the same as a 6L6, it's the same as a 6BG6GA?

jeff

 

[Atk1d]

oops I lied (not intentionally) the tubes that sound the best for me are 6p3p Russian
equivalent, an addendum to my earlier plea for help.
Is there a cathode that will handle the interchange to these tubes? A one shot deal if you will?

 

[vinylkid58]

6P3S? Do they look like the pic? They are basically a 6L6G, so don't know why you're having problems with other similar tubes. They should work fine.

jeff

 

[Atk1d]

no they are coke bottle shaped.
here is pic large rectifier and 6p3p in back.
I also have a set that looks exactly like your pic, I tried those today too, I did not measure the B+ but same result cracking sound, in all fairness I did not really give them time to warm up.
when I insert my messa 6l6 the B+ jumps from about 434(6p3p) to 500+ ( this tube I measured) was convenient.

I've not measured the EL 34 B+ value .

Not sure why the increase in hv, but is a considerable jump.

 

[vinylkid58]

Ok, the 6p3p is a Chinese tube, not Russian, but very similar to 6L6G. Not sure what's going on with the voltage jumping up by changing tubes. Sounds like somethings shorting to B+? Also the tubes shouldn't be making any weird noises either.

I wonder if this is somehow related to the cathode feedback feature?

jeff