Valve Change...?

[stevie_bees]

I'm about to swap the Svetlana EL-34 valves in my amp for the JJ ones that B Bent donated (Thanks Greg!). I've found 2 Fender 12ax7, and a single Phillips ECC83 pre-amp valves. Should I swap them for the current valves? Which of the pre-amp valves should I swap? I know there are 4 in the pre-amp of my Marshall, and I believe they are the ones that come with the amp. Just thinking out loud really. What would you do?

 

[greendy123]

Re: Valve Change...?

After you get the JJ tubes get the amp biased, try the Phillips in v1 of your amp. Thats the pre-amp tube nearest to input of the amp. If you don't like the tone try one of fenders and see which you like best. After that put in the two left over pre-amp tubes in any of the slots that are left over. Then I would just get another tube so you can get all pre-amp tubes changed.

 

[aleclee]

Re: Valve Change...?

When it comes to preamp tubes, I tend to try everything everywhere, starting with the "really good" tubes (generally non-current production) going in either V1 or V2. That said, sometimes cheap tubes will surprise me and sound better than the more expensive stuff. That's why I maintain a diverse stash of tubes.

 

[stevie_bees]

Re: Valve Change...?

I was thinking of going with the Phillips in V1, and trying the Fenders in V2 and V3. I'm going to bias the amp myself.

 

[stevie_bees]

Re: Valve Change...?

I just realised that the Phillips is an ECC81, can I still use that ok?

Also, I take it that v1 is the valve in the metal shield?

 

[shredaholic]

Re: Valve Change...?

It will work, just with less gain.

In my Marshall, all the preamp tubes have metal shields. If you've only got one shield, it's likely to be V1 as that's the most succeptible to microphony. It should be the valve furthest from the power amp tubes.

 

[Gearjoneser]

Re: Valve Change...?

I think your amp has bias point for voltage on the back panel, so all you need is a voltmeter, right? I'm not positive of the voltage value, but if you find a spec sheet on your amp, or contact Marshall/Korg customer service, you can find out what voltage you should be reading.

 

[stevie_bees]

Re: Valve Change...?

I got the power tubes sorted, no problem. Set them for just under 80mV, which is the recommended level. I put the 2 12ax7's in V1 and V2, and the ECC81 in V3. My thinking was that the third channel would sound a little warmer with less gain. It certainly sounded a lot nicer, but the damn valve was microphonic!!! So, I've left the 2 Fender valves in, and am going to try and get another ECC81 to put in for the 3rd channel. Oh, and a V30 to replace the Wolverine. I bloody well started something now, haven't I? :smack:

 

[stevie_bees]

Re: Valve Change...?

It will work, just with less gain.

In my Marshall, all the preamp tubes have metal shields. If you've only got one shield, it's likely to be V1 as that's the most succeptible to microphony. It should be the valve furthest from the power amp tubes.

Yeah, thanks. I managed to figure it out. Curses to microphonic valves!! :yell: