Pulling power tubes;

[Bernardduur]

Hey all!

I wanted to do the following:
My amp has 8 output tubes, EL34, that'll give her 200W power. Now lately I got into the posession of a couple of good 6550's.

I would love to swap the 8x EL34 to approx 4x 6550's

Could this be done in an easy / swap way (with of course the alteration of the bias) or do I need to take into account an impedance change (for example because I run 4 tubes instead of 8 tubes)????

Thanks!

[Steve Conner]

To get 200W from four 6550s, you need a supply of 600-700V.

An amp running EL34s would only have around 450-550V, so you can put in the four 6550s, and they'll work fine, but you'll probably only get about 120-150W from them. Should still be a pretty potent sonic weapon, though

It might help to mismatch the impedance one step: plug an 8 ohm speaker into the 4 ohm tap, etc. You can experiment and see what gives the highest power without redplating.

[Bernardduur]

To get 200W from four 6550s, you need a supply of 600-700V.

An amp running EL34s would only have around 450-550V, so you can put in the four 6550s, and they'll work fine, but you'll probably only get about 120-150W from them. Should still be a pretty potent sonic weapon, though

It might help to mismatch the impedance one step: plug an 8 ohm speaker into the 4 ohm tap, etc. You can experiment and see what gives the highest power without redplating.

Thanks! That were the things I needed to know!!

Might even try 6 6550's but I don't know how to measure the impedance then

[Albert Kreuzer]

An amp running EL34s would only have around 450-550V

Some have more than that...
This one runs off 800 Volts
Sonic weapon? Yes.

Cheers,
Albert

[Bernardduur]

Some have more than that...
This one runs off 800 Volts
Sonic weapon? Yes.

Cheers,
Albert

Yes, sweet!

Too bad my amp only goes to 500