2 Quad EL34 sets for Dynaco ST-70


I am new to tube amp and I really need your help. I have one current quad Russian EL84 running in ST70. My friend gave me another brand new quad Mullard EL34 Russian tubes for me to test sound. What is the best way to remove old quad tubes out and replace new quad tubes? If I do not like new one, I also can put my old tubes back.
sanjose_audio_guy
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
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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.
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