Dynaco ST-70 with Genalex Gold Lion KT66's

[Bob01605]

On the advice an audiophile friend I tried a matched quad of the new Genalex Gold Lion KT66's in my personal Dynaco ST-70. They are still breaking in and only have about 50 hours on them but so far sound better than any tube I have ever put in that amp - even vintage Mullards. A really great sounding tube BUT expensive - $170 a quad plus shipping. The price should come down a little on these tubes in the next few months. Extremely well made (in Russia) tube. I looked them over inside and out with a magnifying glass. On the advice of the same audiophile I was told that they should be biassed a little higher than EL34's - about 50 - 55 milliamps per tube. I am using 50 milliamps right now. They look like a little coke bottle KT88 and the glass seems thicker than a normal tube.
Very large soundstage and good extension at both frequency extremes. Airy but smooth highs. Most listening was done in the normal pentode ultralinear mode. Nice mid range projection when running this amp in triode. Some tubes respond better than others when running an amp in triode. IMHO this is probably the best current production output tube you can use in your Dynaco ST-70, Mark II, Mark IV or any EL34 based amp.

Bob Latino

Photo at of this amp at > http://i9.photobucket.com/albums/a78/Bo ... thKT66.jpg

[Ty_Bower]

Nice looking tubes. I see you have the "upgraded" power transformer. Do you think the stock PT could handle the extra bias current?

[mesherm]

The 6CA7/EL34s on a stock ST70 were run at 50 ma each.
Also the filament current for a EL34 is 1.5 amps compared to 1.27 amps for a KT 66.

Bob, have you compared the KT66s with JJ KT77s?

[Bob01605]

Ty - Since a stock ST-70 biased at 1.56 volts uses 50 milliamps per tube - yes - a stock amp can use these tubes.

mesherm - I WAS using a matched quad of JJ KT77's in this amp. Aside from the mechanical issues with this tube (poorly soldered pins, some tubes still with slighly thinner pins) the JJ KT77's are great sounding tubes. I think the soundstaging on the Gold Lion KT66's is even better and the top end seems smoother and more effortless than the KT77's - but not by much. The Gold Lion is a much better made tube - the pins fit the sockets nice and firm without being too tight and the glass is thicker. This is truly a premium tube for the Dynaco ST-70. Unfortunately it comes with a premium price. Look for the price to drop a little in the few months.

I don't think it is now necessary to find a quad of vintage Mullard's for big $$$ to get the best sound out of your ST-70 - these tubes sound even better than the quad vintage Mullards that I have. Of course the Mullards have many hours on them and so the comparison may not be fair. The top end on these KT66's has noticeably more extension than my Mullards.

Bob Latino