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In Reply to: RE: Do rectifier tubes need to be "matched?" posted by mnilan on May 28, 2014 at 10:34:26
As far as the two sides of each individual rectifier tube,they should measure reasonably close and usually do.As as far as one complete tube to another,they don't have to be perfectly matched but you don't want one tube reading 40% while the other reads 90%.If you have two rect tubes in the same amp as in the case of the Mac Mc60s,those you want to be pretty close because they work in conjunction with each other but again,it is not absolutely necessary otherwise many dealers would be selling matched rectifier tubes.You do want them within 20% of each other maximum performance.
Honest amplification is better than excessive 2nd order distortion anytime.
Follow Ups:
Mikey,
What parameter are you saying should be "matched"?
Jim
I usually check voltage drop and emission..There isn't much to check in a rect tube that I see as far as matching goes.
Honest amplification is better than excessive 2nd order distortion anytime.
Understood. So we agree that the issue of matching is by and large a non-issue. The likelihood is VERY high that two new (or strong/healthy used) rectifiers that have been tested on a decent tube tester will work well in the vast majority of cases.
Exactly it's a non issue.You will notice when I said if one tube read 40% and the other read 90%,that can pose a problem but as a rule,it's not an issue.The likelihood is VERY high that two new (or strong/healthy used) rectifiers that have been tested on a decent tube tester will work well in the vast majority of cases.
Absolutely correct.
Honest amplification is better than excessive 2nd order distortion anytime.
Edits: 05/28/14
Such as the 2 EZ-81's in the Eico HF81?
The same rules apply. As long as you don't have one near dead and one brand new (I'm exaggerating a bit) you'll be fine. One rectifier will virtually always be passing a bit more current than the other for any number of reasons.
The Amplitrex AT-1000 has the nice ability to test voltage drop across a rectifier with 275 volts AC applied to each plate. But even if those tested absolutely equal, small differences in heater voltage or AC voltage in the amp means the "match" will still be off some.
You can put a small value resistor between the rectifier and the filter - that will help equalize things as well.
Jim
I'm just going to buy a new Amplitrex because that used one went for 2400. I will see if I can con the company out of a basic schematic.
Honest amplification is better than excessive 2nd order distortion anytime.
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