12BY7A pentode or triode in a guitar amp

[Jelle]

Hi,

I have a couple of 12BY7A tubes that I would like to use in a guitar amp.

I have found that they are high gm pentodes. Can they be used as the first tube in a guitar amp? I would like to test them as a pentode and as triode but I cannot find a typical circuit on the net to get started.

Does anybody know typical plate , screen and cathode resistor values? I have build an EF86 based amp that I would like to adapt to test these tubes....

Thanks,

Jelle

[Arthur B.]

12BY7s are power output valves, not preamp valves. Here's what TDSL brought up:

http://tdsl.duncanamps.com/dcigna/tu...ets/12by7.html

[Alex/Tubewonder]

Better look in a right place for data on 12BY7A which is a video pentode. Used as triode it has amplification factor 28.

[Jelle]

Thanks for the replies! I had already seen that they are videopentodes...what does this mean other than bandwidth? I also found out that this tube is used in the Harman Kardon Citation II. Please see:

http://www.bassboy.com.au/getreel/si...rcuits/cct.gif

Can I use this tube instead of a EF86 in the preamp? It may need some rewiring and different resistor values. Can I use the Citation II first input wiring for this. And is there a set of resistor values that work for the triode mode?

Any help is appreciated. Thanks!

Jelle

[Arthur B.]

Originally Posted by Jelle

Thanks for the replies! I had already seen that they are videopentodes...what does this mean other than bandwidth?

They're also considerably more linear and tougher than their audio counterparts.

Originally Posted by Jelle

I also found out that this tube is used in the Harman Kardon Citation II. Please see:
http://www.bassboy.com.au/getreel/si...rcuits/cct.gif

With that much power going into the grids, I'm puzzled at at why they didn't use an interstage transformer.

Originally Posted by Jelle

Can I use this tube instead of a EF86 in the preamp? It may need some rewiring and different resistor values. Can I use the Citation II first input wiring for this. And is there a set of resistor values that work for the triode mode?

Any help is appreciated. Thanks!

Jelle

Since the 12BY7 is so linear, the only effect you would would notice is that of a clean boost at the front end. There will be no little to audible coloration. In any case, the datasheet links posted earlier should answer some of your questions.

[Jelle]

I will try this in the next days. Thanks for the answers. I will report back when I have some news. Looking forward to test it!

Jelle