6100 bias

[Braudy]

Its time to change the tubes in my 6100(el34s). Can anyone tell me the tubes that are closest to the originals that came in her(or personal favorites), and what the bias should be. Also, I've changed tubes in my Vintage Modern and it was pretty easy, is the 6100 just as simple?

[Erikk Von Hyde]

Hey man, I used to have one of these and tried a variety of tubes in it before settling on EL-34's. I believe the 30th came with 5881 power tubes so EL-34's are the way to go if you want to stick w/the intended tone. I tried 6L6's in it and it rounded the amp off too much, the 'bark' and punch was gone and I hated it! 6550's would give it a more muscular sound and not hurt the original tone, it would sound more 'American' and have more balls like a Zakk Wylde sound (he uses 6550's exclusively).

[Vemmy]

I replaced first my 6100's EL34's with JJ tubes, but they were somehow faulty, so I had a quartet of TAD tubes, and have been very happy with them. I biased the amp quite hot, works best for me. It isn't the easiest thing to bias, there are no bias points like the VM, and the chassis is full of PCBs and loads of cable...

I believe (someone will probably correct me if I'm wrong) that the 6100's came with EL34's like all the other amps in the early 90's, but Marshall changed to use 5881's in mid-90's in JCM900's and 6100's (probably at the time the LM version was introduced?) for supply problems of 34's at the time, at least that's what I've heard.

So if you don't know exactly what you're doing, leave the biasing to an amp tech. Hot/cold bias is just a matter of personal taste, in my opinion. The real old school dudes plug in and adjust the bias according to their ears, without any meters, and I know a couple that have done this since the sixties... But I've never heard they would have broke a tube...

EDIT: By the way, I don't think the bias trimmer's range is enough to use 6550's, at least all the other Marshalls I've seen to use 6550's have had bias mods for this reason. Dunno if SteveD knows about these? I heard a rumour that Bjorn Juhl would have been working for Marshall in the 90's, and my 6100 is full of 'BJ'-stamps, should ask Mad Professor about this...