6AK5 for Power Stage?

[furrnornos]

I've got a bunch of 6AK5 pentodes, and I think I can't use them as mini-push/pull stages because the plate impedance is too high.

Can someone confirm this is true?

[matt h]

(deleted)

[Kagliostro]

Also I've a bunch of those tubes

I've think to use it as preamp tubes

but also as final tube may be interesting

I'll try to do a search about that use

K

[martin manning]

Looks like a Hammond 125A OT wired to show 22k5 on the primary into an 8 ohm load would work for a push-pull quad of 6AK5, with 180V on the plates and 120V on the screens.

[Kagliostro]

That is interesting

Without result I given a search for a schematic that uses 6ak5 as power tube

but I've find this

[img623]http://grandpaslab.com/wp-content/uploa ... 24x623.jpg[/img]

[img915]http://grandpaslab.com/wp-content/uploa ... em-1.1.jpg[/img]

that seems to be an interesting project

K

[furrnornos]

I was initially under the impression that output (i.e. impedance matching) transformers were spec'd for actual impedance, but after some research it looks like impedance matching is purely a function of turns ratio and power handling.

If thats the case, then a ~1000:1 turns ratio transformer should be ok as long as it power rating is ok.

Can someone confirm? I've got ~20 of these things and I'd love to use them for power stages, but finding a cheap output transformer with ~30k on the primary is difficult/impossible.

[morcey2]

I was initially under the impression that output (i.e. impedance matching) transformers were spec'd for actual impedance, but after some research it looks like impedance matching is purely a function of turns ratio and power handling.

If thats the case, then a ~1000:1 turns ratio transformer should be ok as long as it power rating is ok.

Can someone confirm? I've got ~20 of these things and I'd love to use them for power stages, but finding a cheap output transformer with ~30k on the primary is difficult/impossible.

Impedance ratio is the square of the turns ratio. If the trannies are really 1000:1 turns ratio, then the impedance ratio is a completely useless (for our purposes) 1,000,000:1. If the impedance ratio is 1000:1, then the windings ratio is ~32:1. For a 30K on the primary, find an 8k:4 impedance ratio transformer and run a 16-ohm speaker in it. that will give you a 32k:16 transformer. The easiest single-ended OT for that is the good old reliable tweed champ OT.

http://www.classictone.net/40-18030.html

I don't know if I'm missing something, but that's what you'd need if you're looking for a ~30k primary.

Also, power handling has nothing to do with impedance ratio. At least not directly. That's more a function of transformer size, wire gauge, and how things are constructed.

Matt

[furrnornos]

...awesome stuff...

Amazing... this is exactly the summary i was looking for.

Thanks!!!

-Jordan

[Kagliostro]

I've just find this schematic

it is the only 6ak5 / 5654 I've seen used as power tube

but this is proof it can be done

K