To match quad EL34 tubes

Unless you run the tube in your amp or a similar amp and knows what to measure, there is no guarantee that you are buying a "Match" tubes. Most of the "Match" tube advertised have close or equivalent Gm (transconductance) measurements when measured with a tester. While when you run a tube in an amp, this is not the only parameters that are important.

My experience: Like you, I still have a Dynaco ST70. In my quest to get a match set of Mullard tubes, I had tested at least 10 to 14 pieces before I got lucky with a quad and returned the rest. Some have high Gm measurements, but does not bias in the amp. You see what I am getting at?

Test it in your amp and see if it holds bias, then compare the GM on a tube tester. Buy from a seller that have return policy or accepts replacement.

Where did you find brand new Siemens tubes?Do you mean NOS?I don't think Siemans have made tubes for many years,but,I could be wrong,have been before.I'd hate to see you buy something that was misrepresented.

My friend in LA has couple brand new Siemans EL34 tubes for sale. I want to buy them but no clue on quad for my Dynaco ST 70. ST70 has biaset voltage only.

Yes, the price is fine, but as noted above, you'd have to buy a large batch to find a matched quad.

ST70 manual>>>[http://www.curcioaudio.com/st7_mnl.pdf]

The two tubes on the left side need to be a matched pair,and the pair on the right need to be matched.The left side matched pair doesn't have to be the same as the right pair.The left half of the amp is biased up separately from the right side pair.Like Viridian says you don't have to buy 4 matching tubes.It can be two separate matched pairs.The pair on the left could be a different brand than the pair on the right.The left will sound different than the right if you did this,but it would work.The manual link may help.

Thanks for all your information. Are Siemens tubes better than Russian tubes?

'Better' is really a matter of taste, and the balance of the rest of your system.

Different brands of tube will have different tonal balance.

If you're looking for a different sound from your ST70, a different driver board might be what you seek. Some will also allow you to set the bias of each tube seperatly.

John C.

One important thing I forgot to mention.Anyone new to tubes,please don't turn a tube amp on without speakers hooked up to it.If you do,you may ruin the output transformers. Always make sure your speakers are hooked up first.♫