output tubes unmatched tolerance?

[highstream]

Coming back to tubes after maybe 35 years. I have a Lampi tube dac on the way where the tubes -- output and recti -- are plug and play on top, no user biasing. For the output pair, I'm looking around for GEC KT66's and wondering in the case of pairs not advertised as matched, as many aren't, how much tolerance between them is actually workable. Here's an example: a pair where the seller presents them as 78ma @-15v (120%) and 74ma @-15v (114%). What do I make of this? Thanks,

Btw, are there other posts on this topic? I did a search on the tube-audio forum but didn't find anything directly relevant.

 

[peterh]

Tubes will happiliy vary +-25% on most parameters. Use of unmatched pair in a pushpull amp
is not recommended. Better buy new matched pair from a reputable dealer. Or even better, but a matched quad, this will give a matched pair even if one or two tubes gets broken during use.

 

[highstream]

Is a dac a push-pull amp?

Part of why I'm asking is that reputable dealers that have the GEC KT66's - not many - are charging two to three times private sales, which themselves are relatively high right now.

 

[larryderouin]

DAC = Digital to Analog Converter. No amp, no preamp. If this thing has output tubes (ie: KT-66, el-34. 7189, etc., etc) with a DAC included, then it's most likely an integrated amp (preamp and amp). A preamp will not have output tubes (in the literal sense) but the last tube is usually considered a driver tube. Some pictures of this Lampi unit with a model #, or documentation you have will help determine what you actually have.

ORIGINAL GEC KT66 tubes are getting rare as hens teeth. Supply and Demand. They ain't made anymore. Look for a 7581 (U.S. Version of KT-66) if your wallet is having a stroke.

 

[peterh]

Is a dac a push-pull amp?

Part of why I'm asking is that reputable dealers that have the GEC KT66's - not many - are charging two to three times private sales, which themselves are relatively high right now.

Don't care about old "unknown" stuff. Get new tubes, a matched quad JJ KT66 will cast $166
https://www.eurotubes.com/store/pc/KT66-c65.htm

 

[highstream]

DAC = Digital to Analog Converter. No amp, no preamp. If this thing has output tubes (ie: KT-66, el-34. 7189, etc., etc) with a DAC included, then it's most likely an integrated amp (preamp and amp). A preamp will not have output tubes (in the literal sense) but the last tube is usually considered a driver tube. Some pictures of this Lampi unit with a model #, or documentation you have will help determine what you actually have.

ORIGINAL GEC KT66 tubes are getting rare as hens teeth. Supply and Demand. They ain't made anymore. Look for a 7581 (U.S. Version of KT-66) if your wallet is having a stroke.

I am aware of what the letters in dac stand for, but it doesn't seem you are aware that there are some tube dacs on the market which use output tubes (usually inside the case). I won't cover the field, but attached is a screenshot of the upgraded Lampi Atlantic 2 TRP similar to the one I'll be receiving in a couple of weeks, the main difference being that mine has a volume control knob/preamp already installed (TRP = Tube Rollers Paradise). The outside two tubes are output. You can check the Lampizator website (Poland) to check that it's actually a dac, and not integrated with an amp (the photo there still shows the former version with two tubes).