Pulling tubes

The Scarecrow · Post by **The Scarecrow** » Thu Dec 08, 2005 10:28 pm

So, I blew a tube in the DSL the other day, and took out the corresponding pair, and it seems to work fine on 2xEL34 instead of 4. I'm guessing it's running at 50w now instead of 100w? Any danger in doing this - I hear all about guys saying this is a good way of reducing output to get a nicer toner at lower volumes. I intend to replace the tubes (all 4) before Christmas, but was wondering if it's okay to use in the meantime? I have had a couple of jams on it, but nothing too loud, seems to go okay. Anyone able to confirm/deny this?

ash · Post by **ash** » Fri Dec 09, 2005 8:07 am

You have to change the speaker impedance setting to avoid killing the output transformer. I can't remember which direction, so hit the google and find out before running the amp again.

B45-12 · Post by **B45-12** » Fri Dec 09, 2005 8:43 am

Yeah second Ash with a vengence - the output stage is designed to work with 4 tubes and 2 can fry the output xformer. Find out the adjustments you need before powering up again and thank your lucky stars you're OK this far.

The Scarecrow · Post by **The Scarecrow** » Fri Dec 09, 2005 12:20 pm

Mmmkay, so apparently you should pull either

- the inner two tubes or
- the outer two tubes

and as far as the impedance goes, it approximately doubles.

http://www.torresengineering.com/mar20latving.html