Coupla 73 Marshall preamp tube questions

[75lespaul]

I want to try some tubes I have laying around in this amp my friend got last night and just want some opinions on what order to put them in. It's a 73 50 watt Marshall. They are a JJ ECC83S, 12AX7EH (Electro-Harmonix) and a NOS Mullard 12AT7. The tubes in there now say CET or CIT or something like that. Anyone ever hear of them? Also, the EL34 tubes have no markings at all but the plastic bases are brown. Sound familiar? The amp sounds really good but we want to get it into that "great" territory.

Now if I'm looking at the tubes from the rear of the amp, from left to right the preamp tubes are v3, v2, v1, right?

Thanks guys.

 

[Gearjoneser]

Re: Coupla 73 Marshall preamp tube questions

No, v1 is the pre tube furthest from the power tubes.

I'd probably put 2 new JJ E-34L's in it. Then, listen carefully as you move 3 12AX7's of different brands around. The one in the 1st position should be your hottest and/or most toneful tube. I'm not sure if I'd use the AT7 for anything. Stick with all functionally quiet 12AX7's.

It'd be a good idea to have a bias tool and mA meter, so you can check where the bias mA are. It'll probably sound best from 36-40mA. Look at my Jubilee bias thread in the Vault, if you haven't already.

 

[75lespaul]

Re: Coupla 73 Marshall preamp tube questions

No, v1 is the pre tube furthest from the power tubes.

I'd probably put 2 new JJ E-34L's in it. Then, listen carefully as you move 3 12AX7's of different brands around. The one in the 1st position should be your hottest and/or most toneful tube. I'm not sure if I'd use the AT7 for anything. Stick with all functionally quiet 12AX7's.

It'd be a good idea to have a bias tool and mA meter, so you can check where the bias mA are. It'll probably sound best from 36-40mA. Look at my Jubilee bias thread in the Vault, if you haven't already.

Me....a bias whosawhatsit...meter....HAHAHAHAHAHAHAHA. Oh man, thanks gear, I needed a good laugh. Man, I crap my pants at STATIC electricity never mind the real stuff, lol. I don't mess wit dat. Yeah, when he retubes (if he ever does) it will be all new stuff, but I've just got these tubes sitting here so we thought we'd try them out. I know the AT7 is a cleaner tube but hell, it's a Mullard, lol. So maybe V3 for that one then?

 

[Gearjoneser]

Re: Coupla 73 Marshall preamp tube questions

Don't worry about the bias then. Just pop'em in and see how they sound. Just be sure to wiggle them out in a circular pattern while holding onto the base.
As long as the tubes aren't old and shot, the amp will sound fine.

 

[75lespaul]

Re: Coupla 73 Marshall preamp tube questions

Those preamp tubes must have been cooked man. I put the JJ in V1, the EH is V2 and the Mullard 12AT7 in V3 and the amp tightened up, a lot of the mush going away. I guess the JJ is the tube that set the tone there. I gotta get him to get a matched set of three and some new EL34s for this amp. It's one of the better sounding non-masters I've heard, and the best PC board amp I've heard--that I knew had a PC board, lol. Even with the 12AT7 is really overdrives. Got some cool Maiden and Priest sounds using my Plexitone and Bad Monkey too. Lotta fun we had tonight.

 

[Gr8Scott]

Re: Coupla 73 Marshall preamp tube questions

The AT7 will clean things up a lot. Maybe good maybe not. Sounds like it was interesting at least. In a severely heavy amp like the peavey XXX it took 2/3 of the distortion out when in the V2 slot.

 

[75lespaul]

Re: Coupla 73 Marshall preamp tube questions

I didn't really notice any less distortion--maybe because the 12AT7 was in V3? It really changed the sound though. Much better. I gotta wonder how many people (like my friend, lol) think there's something wrong with the amp and sell them or something, when all it needs is some tubes.

 

[OlinMusic]

Re: Coupla 73 Marshall preamp tube questions

I just did some of these experiments

AT7 cleans things up a bit too much, you might get a Bastard Marshall that chimes but not like a vix, and lacks the balls for a real Marshall. Stick with 12AX7s

The JJ's tend to have the sweetest and most harmonic Midrange to me. I like the EH mix or a Tung Sol mix for some highs and chime, but JJ's are cheap, heavy duty, and never go wrong in Marshalls