Marshall tube biasing

PTO · 10-09-2010 11:22pm #1

Hey I have been told that this forum would be the best place to get help for biasing new tubes! basically.....

I'm after replacing all the tubes in my Marshall JCM 2000 DSL 100 head but I've been told that I have to bias them before I can start playing again. I've tried ringing around shops and even some electricians I know but so far I'm having no luck. Guitar repair places wont do it cause I'm not buying the tubes from them!
Anyone able to shed some light on the whole biasing thing?? Or know of anyone who can do it?

cheers!!

punchdrunk · 10-09-2010 11:24pm

Amp Repair In Dublin
Aladdin's Amps
Phone: +353-1-4935553/+353-0-862490940
Email:aladdinsamps@yahoo.co.uk

PTO · 10-09-2010 11:45pm

Thanks Punchdrunk, could I ask do you by any chance work for them or are you just passing on the details? I only ask because I actually emailed them on Monday and never heard back!! I've been told that some places would be very hesitant to do the biasing for me since I'm not buying the tubes from them

punchdrunk · 11-09-2010 12:09am

PTO wrote: »

Thanks Punchdrunk, could I ask do you by any chance work for them or are you just passing on the details? I only ask because I actually emailed them on Monday and never heard back!! I've been told that some places would be very hesitant to do the biasing for me since I'm not buying the tubes from them

nope don't work for them but have gotten work done by "him"

i'd say ring him is your best bet

PTO · 11-09-2010 12:15am

Cool, thanks for that! I'll give them a shout!

stephenshields2 · 11-09-2010 1:22pm

Where are you based man?

MoveOverSeamie · 11-09-2010 5:31pm

If you replace the tubes yourself, the amp will still work but the level of distortion may be different at the settings you previously used, then again you might not even notice the difference.

PTO · 11-09-2010 6:18pm

Stephen, I'm based in Clontarf. Do you know how to do it??

MoveOver, I heard that before alright but the only problem is I've bought custom tubes for higher gain so to get the right sound (and my monies worth) I'm probably better off doing everything by the book!!

darrenw5094 · 11-09-2010 9:41pm

If you are replacing the power valves, EL34's, it needs a re-bias alright. If you are unsure, take it to a tech. The amp must be powered on for this and voltages can be fatal if you are unsure.

Preamp valves just pull out and push the new ones in when the amp is off.

PTO · 12-09-2010 1:53am

thanks Darren, I replaced the 34's so I definitely need a biasing by the sounds of things.

This is not as easy as I thought it would be!!!

darrenw5094 · 12-09-2010 2:21am

PTO wrote: »

thanks Darren, I replaced the 34's so I definitely need a biasing by the sounds of things.

This is not as easy as I thought it would be!!!

http://www.eurotubes.com/euro-Marshall-DSLTSLV.htm

stephenshields2 · 12-09-2010 1:11pm

PTO wrote: »

Stephen, I'm based in Clontarf. Do you know how to do it??

MoveOver, I heard that before alright but the only problem is I've bought custom tubes for higher gain so to get the right sound (and my monies worth) I'm probably better off doing everything by the book!!

I bought a regular old multimeter for about 15 Euro, and learned how to bias myself. Its not hard by any means, the Marshalls make it so easy!

Marshall recommend bias of 90mV (well, thats for mine, the TSL 100) but I found that to be running very hot, so I run it on 84mV with JJ Tesla's and she sounds sweet as a nut man!

PTO · 12-09-2010 5:41pm

Thanks for the tips and the video folks. Looks like I'm gonna be getting myself a multimeter and giving it a go!! I knew I shouldn't have sacked that guitar tech!!!

Eoin Madsen · 12-09-2010 8:23pm

If you're going to do it, just be really careful, and do a whole lot of reading about it before you put your hands inside. It is possible to die while biasing an amp. Which just seems like a bit of a lame way to go.

PTO wrote: »

I've been told that some places would be very hesitant to do the biasing for me since I'm not buying the tubes from them

I can't think of any practical reason why they should be. They may not like it, but that's their own problem.

MoveOverSeamie wrote: »

If you replace the tubes yourself, the amp will still work but the level of distortion may be different at the settings you previously used, then again you might not even notice the difference.

Probably, but that's assuming the replacement valves are pretty close to the old ones, and that the old ones were biased correctly in the first place. The hotter the bias with respect to the valve, generally the shorter the life of the valve. You could be talking about anything from shortening it to a couple of months, or a couple of minutes. Bias should not be overlooked.

Marshall tube biasing

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