When switching the tube.. - Jemsite
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post #1 of 12 (permalink) Old 09-21-2005, 01:29 PM Thread Starter
 
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When switching the tube..

Hi!
I've just bought myself some new tubes to my amp (a Marshall tsl 601), and I just wondered if the bias has to be adjusted since its another pair of tubes? I'm switching from EL34 tubes, to 6L6... anyone who knows anything?
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post #2 of 12 (permalink) Old 09-21-2005, 02:19 PM
rgr
 
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Re: When switching the tube..

Many amps will accept either type of tube and have a switch on the back, I don't think Marshall is one of those though, since EL34s are a huge part of the "Marshall Sound". The basic answer is yes, at minimum it will need to be rebiased. If you really want to run 6L6s in it, and provisions for running 6L6s haven't been made in the amp, it will require some component changes and possibly some minor rewiring of the tube sockets. It will probably also devalue the amp if provision is not made to switch back to EL34s easily, because most people looking for a Marshall want to use EL-34s.

Roger
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post #3 of 12 (permalink) Old 09-21-2005, 03:13 PM Thread Starter
 
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Re: When switching the tube..

ok... thank you for the reply!!
I've just tried to see if everything went well, and it did, and I'm much happier with my sound now! I'm not really that excited about the marshall sound, but I could'nt afford a new amp at the time so I thought I could just try and see, and if the result sucked, I would switch back to the EL34.

But right now I'm really happy!
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post #4 of 12 (permalink) Old 09-21-2005, 06:48 PM
rgr
 
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Re: When switching the tube..

You just stuck the 6L6s in and went for it? Does the TSL 60 have a switch for 6L6s? They are probably over-biased (I think, don't remember the specs off the top of my head) and one of the tube types has an extra ground pin that the other one doesn't, again, I don't remember off the top of my head, but if it's not wired correctly, it may be a short lived happiness.

Again, if it has the switch for 6L6s, it should be fine, otherwise check with a tech.

*edit* I just looked up the manual at marshallamps.com, it doesn't say anything about the TSL60 being 6L6 compatible, so, you're on your own. The 2 tubes aren't direct replacements for each other.

Roger
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post #5 of 12 (permalink) Old 09-22-2005, 03:32 AM Thread Starter
 
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Re: When switching the tube..

I haven't seen any switch for the 6L6 tubes on the amp. And I don't want to be fiddling in my amp on my own so I'll just wait for the tech to check things out. Until then I will leave the amp alone just in case.
And I didn't see any kind of info about the bias on marshall's website, it just stood when you change the preamp tubes, you don't have to adjust te bias.
Thank you for your replies!
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post #6 of 12 (permalink) Old 09-22-2005, 10:57 AM
rgr
 
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Re: When switching the tube..

EL34s and 6L6s are power tubes, not preamp tubes. No need to rebias for preamp tubes (12AX7s, the little ones).
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post #7 of 12 (permalink) Old 09-22-2005, 02:17 PM Thread Starter
 
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Re: When switching the tube..

I know that much was just saying the only thing it said about the bias on the marshall site
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post #8 of 12 (permalink) Old 09-22-2005, 07:05 PM
Gex
 
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Re: When switching the tube..

Lol, the thing was probabably baised so cold on EL34's that its biased warm for the 6l6s.
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post #9 of 12 (permalink) Old 09-25-2005, 05:30 PM
 
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Re: When switching the tube..

Quote:
Originally Posted by rgr
Many amps will accept either type of tube and have a switch on the back, I don't think Marshall is one of those though, since EL34s are a huge part of the "Marshall Sound". The basic answer is yes, at minimum it will need to be rebiased. If you really want to run 6L6s in it, and provisions for running 6L6s haven't been made in the amp, it will require some component changes and possibly some minor rewiring of the tube sockets. It will probably also devalue the amp if provision is not made to switch back to EL34s easily, because most people looking for a Marshall want to use EL-34s.

Roger
You still have to bias the amp to change tubes with the same type, so those switches are misleading anyway (unless you use Groove Tubes or test your tubes before you put them in and buy a quad or set that test identical).
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post #10 of 12 (permalink) Old 09-25-2005, 09:35 PM
rgr
 
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Re: When switching the tube..

Yes, but then you are biasing for tone. Even if the tubes test identical, you probably need to bias because that last set wasn't identical. Biasing hot means biasing toward Class A (but it's still AB) and usually sounds killer but eats tubes, biasing to cold allows too much crossover distortion where the sine wave doesn't line up.

Sorry, I was more concerned with the original caller plugging the wrong kind of tube in.

Roger
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post #11 of 12 (permalink) Old 09-26-2005, 09:10 AM Thread Starter
 
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Re: When switching the tube..

ok.. Im a bit confused here... The amp seems so far to be doing good, it's got better sound than ever before. I have no idea how to rebias the thing, and the only tech around here (yes I live in the middle of nowhere in Norway), had never done that before on a amp, so I'm not so very keen on having him experimenting on my amp... So should just put in the old tubes again?

Thanks for helping
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post #12 of 12 (permalink) Old 09-26-2005, 08:38 PM
Gex
 
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Re: When switching the tube..

until you find I tech, I would put the old ones back in.

You dont want to burn them up prematurely.
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