Is biasing really nessasary?

[donf]

Hey sm5150

See if this helps.

I just use the multimeter. Very easy once you play with it.

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

[Twisteramps]

Clarification - 'same type of tubes' hopefully means same RATED tubes, or same rated by whatever system your toob manufacturer uses - 1-10 for Groove tubes, colors for boogie, etc.

Just buying the same brand doesn't mean crap, Tubes can vary widely from one batch to another. As long as you aren't red plating the tubes, your amp isn't getting hurt... but I never understood why people would obsess about pickups, or strings, or preamp tubes, or whatever... and not bias their fuckin' amps!

Pete

[sm5150]

Hey sm5150

See if this helps.

I just use the multimeter. Very easy once you play with it.

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

THanks to everyone who responded.
looks like the topic is more in depth than I thought.
anyway, from that vid it DOES look fairly simple, but i read everywhere that if I dont know what Im doing, I can kill myself. And thats not good ...

[Rsmacker]

If you learn nothing else about valve amps, and there will always be schools of thought towards one way of doing things or another, the ONLY thing you need to remember is that they are FUCKING DANGEROUS if you aren't sure of what you are doing.

You could almost certainly get away with poking around inside a transistor amplifier, you might get a belt, or a fright, and you could certainly do some expensive damage. An AC shock is unpleasant, but unless you are very unlucky and end up fibrillating your heart, you will more than likely walk away from it a little wiser and pretty sheepish.

A high voltage discharge from a cap is another story, burns and is more likely to kill you. Valve amps hold charge long after they have been switched off, and even when you have drained them, you still have to be wary.

I learned long ago to keep my left hand in my arse pocket when looking inside amplifiers, so if I did get a belt, I wouldn't get it across the heart. Watch any old technical bod and they all do the same without thinking - they lean forward to look inside and their left hand is in their back pocket. I used to think they were about to get a round in......shows how naiive I was!!!

If you are technically minded, have some electrical/electronic experience, it is well within your capabilities. Just be careful, take precautions and don't think "I wonder what this bit does, or if I turn this thing here......"

[jgcable]

As long as you stick with the same brand just swap them out. If you are not sure... call or email Bob from Eurotubes and he will hook you up.

[Infernal Death]

As long as you stick with the same brand just swap them out. If you are not sure... call or email Bob from Eurotubes and he will hook you up.

Hey John, have you read what was said before ? Really, it's wrong what you are saying. The same brand of tubes doesn't mean anything. It's the values of the actual tubes that are important in terms of biasing. Bob from Eurotubes probably will hook you up with the same rated tubes and that's ok but only buying the same brand of tubes doesn't mean the bias settings are working for your new tubes.

Flo

[DonP]

The only time I remember you could get by without re-biasing is with Groove Tubes. If you got an H-5 set of tubes and stuck with H-5, you wouldn't need to re-bias.

The 5150 gets by with a fixed bias by having the bias safely in the middle of the range. Might be a little hot for some tubes and a little cold for others.

[Twisteramps]

One other thing too - bias is set by a resistance. Well, resistors and pots can change value over time - it's called component drift. I'd still check my bias at every tube change if at all possible, whether I was using same 'number' or 'rated' tubes. It's just common sense.

Pete

[jim777]

I got a matched set of 6L6s for my X100-B a while back from the Tubestore.com, and when they came they all had little stickers on them that said "35" in pen ink. I guess that's how they tell if they're hot or cold or whatever and match them up. After a year or so they didn't sound as good as new, and when I ordered another set I mentioned the last set all said "35" on the box, and they sent me another set that also said "35". I'm not sure what the 35 measurment means, but it does seem easy enough now