Cathode current meter.....build question

[Garydean]

I'm finally getting around to building a bench top, tube bias meter for matching tubes and setting the bias on tube amps. I've been checking analog panel meter prices, and they're all over the place. Mouser has Simpsons for 80 bucks a pop.... that may be over kill for what I'm doing. Does anyone have a lead on a brand of meter that's perfect for what I'm doing and won't put me too far in the hole? I'd rather have 2 on-board, 100ma meters, instead of using my DMMs.... or should I use 2 DMMs? That may be cheaper in the long run.

My build consists of a box that houses 2, 8 pin sockets complimented with analog meters. I'll have 2 octal extension cords from the box, each 30" long, that I'll use to plug into the sockets on the amp.

What else would I need to add?

thank you!!

[Steve Conner]

You can get DMMs for 10 bucks each, which is hard to beat. But I think analog meters look nicer. Try Ebay. Also remember that most voltmeters or ammeters can be re-scaled to read whatever you want.

If you were using 30" extension cords, you might get trouble with parasitic oscillations caused by coupling between the screen, grid and plate conductors inside the cord. You probably want to add another grid stopper resistor at the tube end of the cord, at least. Screen and plate stoppers would be nice too, but they will affect the bias current you're trying to set.

[Garydean]

Thanks Steve, great ideas.

Gary