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Post by Telemanic on Aug 8, 2006 13:31:26 GMT -7
Hi Myles, if ya happen to glance at this maybe you could offer some guidance. Ive been looking at getting another set of GEC kt66's. I some time back picked up a set from Clark amplification, matched NOS, and of course trusted Michaels representation of the tubes. I was not disappointed and got the original "groovy" boxes as well. But lately have not been seeing any availible from a trusted source like Clark or KCA, etc. It seems the ones ive found lately on e-bay, the sellers use term "matched" pretty loosely. After inquery about one pair, the seller informed me that his use of the term matched was based on the mutual transconductance of the tubes. In the absence of a matched within (X) ma, measurement, what are the chances of getting a usable set for an amp with a single bias pot, and what criteria is THE one for this purpose, .........Plate current in ma's ?
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Post by myles on Aug 10, 2006 8:16:38 GMT -7
Hi Myles, if ya happen to glance at this maybe you could offer some guidance. Ive been looking at getting another set of GEC kt66's. I some time back picked up a set from Clark amplification, matched NOS, and of course trusted Michaels representation of the tubes. I was not disappointed and got the original "groovy" boxes as well. But lately have not been seeing any availible from a trusted source like Clark or KCA, etc. It seems the ones ive found lately on e-bay, the sellers use term "matched" pretty loosely. After inquery about one pair, the seller informed me that his use of the term matched was based on the mutual transconductance of the tubes. In the absence of a matched within (X) ma, measurement, what are the chances of getting a usable set for an amp with a single bias pot, and what criteria is THE one for this purpose, .........Plate current in ma's ? Find out from Mike Clark at what plate voltage and bias voltage the tubes were matched at and hopefully you have the numbers. A high end tube vendor should be able to match to TC or current output. Just tell them you are looking for something in that specific range. But ... in the end, it may be easier to buy a nice matched set and just bias your amp. If they are cheap and off ebay and more than 20% apart from each other they are not a good deal at any price. I prefer to stay within 10% at idle personally.
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Post by Telemanic on Aug 13, 2006 14:39:23 GMT -7
Thanx Myles, sorry my computer was down for a couple of days, and could not check the site till now.
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maction
Full Member
SRZ for me
Posts: 227
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Post by maction on Aug 19, 2006 12:21:27 GMT -7
Myles,
while we're talking about power tube matching...
if I were to buy a packaged quartet of Groove Tubes KT66HP for my Route 66, would I be able to have the amp biased for one duet, then swap in the remaining two without having to re-bias?
thanks again for your time spent on this forum!
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Post by myles on Aug 21, 2006 8:36:46 GMT -7
Myles, while we're talking about power tube matching... if I were to buy a packaged quartet of Groove Tubes KT66HP for my Route 66, would I be able to have the amp biased for one duet, then swap in the meaning two without having to re-bias? thanks again for your time spent on this forum! Anytime I buy tubes for an amp that uses a duet I always buy a matched quartet as to have a perfectly matched backup duet. One big mistake folks make at many dealers is if they do not have a matched quad and somebody needs one but they have two of the same number duets they sell them to the customer as a matched quad. This is NOT a matched quad. The 1-10 rating system really spans about 250 points so even in say a #4 set as an example there can be a spread too wide for my tastes. If you have a quad for you 66 and bias for half of them you will be right on the money and need no adjustment when you use the other set.
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