• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

matched tubes?

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webelo said:
What should I be looking for in the numbers people are posting about the matching?

A small number of $. :D

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.
 
webelo said:
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!
 
Re: Re: matched tubes?

EC8010 said:

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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