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Old 15th December 2007, 12:20 AM   #1
webelo is offline webelo  United States
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Default matched tubes?

I'm looking to pick up a pair of matched Mullard el34's for a marshal 18watt. What should I be looking for in the numbers people are posting about the matching?

are these matched well?
mullard el34
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Old 15th December 2007, 02:53 AM   #2
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Default Marshall 18W uses a pair of EL84

And matched pairs aren't so necessary for guitar amps. Just so long as you can bias them properly.
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Old 15th December 2007, 10:44 AM   #3
EC8010 is offline EC8010  United Kingdom
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Default Re: matched tubes?

Quote:
Originally posted by webelo
What should I be looking for in the numbers people are posting about the matching?
A small number of $.

More seriously:

You probably don't need matched valves.
A single point measurement is only useful if it's at your operating condition.
The AVO CT160 gm measurement is based on a very dubious assumption.
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Old 16th December 2007, 03:04 PM   #4
PRNDL is offline PRNDL  United States
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Default Re: matched tubes?

Quote:
Originally posted by webelo
I'm looking to pick up a pair of matched Mullard el34's for a marshal 18watt. What should I be looking for in the numbers people are posting about the matching?

are these matched well?
mullard el34

Yikes ... NOS tubes are expensive!!

Personally, I recommend getting tubes from a vintage tube amp tech. Fortunately, there's one in my town that's very helpful: Larry Rodgers at (239) 649-8799.

Last time I was there he had a Ceriatone TMB in for repairs and new tubes. It's an 18-watt that sounded very cool!
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Old 16th December 2007, 03:05 PM   #5
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Default Re: Re: matched tubes?

Quote:
Originally posted by EC8010

You probably don't need matched valves.

A single point measurement is only useful if it's at your operating condition.

The AVO CT160 gm measurement is based on a very dubious assumption.
Let me mention a couple things:

1. Current matching of the valves/tubes is a real necessity in a Marshall since there is no individual bias adjustment. Tubes matched for cathode current are a requirement.

2. In discussing single vs. multi-point measurements and the way a CT160 measures Gm - it's not really relevant here. The absolute value(s) of Gm is not really a concern, it's Gm relative to each other that may be important. So as long as the method of measurement is consistent it's fine.

Besides, some players prefer mismatched Gm, they like the tone better. But current matching is a must.

The tubes on the eBay listing would have likely been fine.
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Old 16th December 2007, 10:37 PM   #6
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Ive been ripped off a couple times on eBay. You're much better off buying NOS tubes from reputable websites like AES or TubeDepot.
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Old 16th December 2007, 10:57 PM   #7
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Quote:
Originally posted by TubeHead Johnny
Ive been ripped off a couple times on eBay. You're much better off buying NOS tubes from reputable websites like AES or TubeDepot.
That wasn't what he was asking, nor what I was recommending. I just meant the matching listed would do fine.
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