Retubing the preamp section in my amp?

[raymo]

I always hear people saying they have 12ax7's but ONE 12au7 in the phase inverter or driver or v1 spot or somefin like that and it gives them a much clearer tone, what does that really do?

I want to retube my DSL wtih Electro Harmonix, and I was think'n about get'n 5 12ax7's just to have one to fiddle around with and 2 12au7's if I understand exactly what that concept is behind it.

Please info on this would be appreciated.

[Twisteramps]

Re: Retubing the preamp section in my amp?

a 12au7 is a lower gain tube - so you're going to lose gain, especially if you put it in V1.

Also, when you get new preamp tubes, swap em around and see which ones sound best where. You have a little easier time if you have access to a tube tester, but otherwise you can use your ears. The tester never lies tho, and measures the gain of the tubes.

Generally speaking, the first thing I do when I get a new amp is yank the preamp tubes out and put the highest gain tube in V1, lowest in the phase inverter, and mix and match the rest, but usually the first tube is the most important.

On the JCM800 that was voodoo modded, two of the tubes in the preamp were nearly dead, and the amp sounded like CRAP when I got it. Good tubes in the right spot, and the thing sings.

One option you have if you don't have a tube tester is to get your tubes from somewhere that will grade them or sell tested high-gain tubes. Usually costs a few dollars more, but well worth it, in my opinion. Bob at Eurotubes www.eurotubes.com does this for a few dollars a tube. I think he pretty much just sells JJ tubes, however.

Pete

[raymo]

Re: Retubing the preamp section in my amp?

If I wanted to where would I get one, and how about much do they cost?

[Twisteramps]

Re: Retubing the preamp section in my amp?

look on ebay.

Pete

[raymo]

Re: Retubing the preamp section in my amp?

Ok thank you Pete, always helpfuly with me.

How do I know exactly which is the phase inverter, and I guess the v1 is the closest to the input? Where do I get one of these tube testers and how much do they cost?

Thanks Pete

-Raymond

[Twisteramps]

Re: Retubing the preamp section in my amp?

V1 is closest to the input, phase inverter is usually closest to the powertubes and furthest from the input.

If you get a tube tester, make sure it tests for mutual transconductance and also comes with a MANUAL. They have tons of knobs and switches, and they have to be adjusted for each tube type.

Pete