2 Quad EL34 sets for Dynaco ST-70

At the risk of opening a horrible can of worms, when the Dyna was designed, the tube of choice was the Mullard EL-34, though many owners used the GE 6CA7. These were quite different in terms of build quality than the stuff that we currently get from Eastern Europe and China. Even though the new tube says "Mullard" it is no more a Mullard than that Rolex that you bought on your last trip to Hong Kong is a Rolex. The new tubes are much more frail than their forebears, even though many sound quite good. The Siemens that you had mentioned earlier are quite frail as well. I think that a lower bias voltage is appropriate for these tubes in the Dyna. Perhaps 1.4 or 1.3V. How can you determine what will work best for you? Well, the lower the voltage is, the longer the tube will last but, at some point, the sound suffers. So if you can't hear any difference biasing at 1.3 than you can at 1.56, go for it. If you feel that 1.56 sounds best and don't mind a little shorter tube life, then that is best for you. Interstingly, the 1.56V was arrived at because the inexpensive volt meters of the day were not particularly accurate and a battery put out precisely 1.56V. So all the user had to do was measure a battery with the voltmeter and bring the needle up to exactly the same place with the bias control. And now back to your regularly scheduled program, already in progress..................

Thanks for all your information. I did change 4 Russian Mullard El84 tubes. Sound is much better than Svetlana tubes. Tubes need more time to burn in. I set biaset around 1.40V for both channels. Less money but sound is much better than solid state costing more than $1500. Klipschorn sings better than before. I did try Siemens EL34 tubes but sound is not much better than Russian EL34. For me, system matches speaker, amp, and pre-amp. Expensive systems do not mean sound better just look and brand name. For amp connection, I found better right adapter for high end RCA. I want to keep original connection. radioshack.com/produc/index.jsp?productId=2102594

Sag, which Klipsch are you using; I use the original Fortes and like them quite a lot. I have been thinking of moving up to Cornwalls? The LaScala's are not for me, but a pair of Altec Valencias may be in my future.

I currently use Klipschorn with Dynaco St70 and PAS 3. My friend has Altec Valencia which sound is good with mid-range. I used to have Cornwalls with sound is good but La Scala is much better with vocal for Jazz.

Nice rig there. The La Scala's just don't do it in the bass for me. I enjoy full orchestral music, rock and dance, as well as jazz and bluegrass so I need a kind of all around speaker.