Just picked up a Dynaco Stereo 70, have a few questions

[nj pheonix]

The real issue is : will it sound worse unmatched? I do not know,i don't have that kind of ears. Sensitivity to
small amounts of distortion is debatable.

As I said before, my ST70 with clearly , unmatched (good but not great testing and surely past their prime) tubes sounds fine to me. I clearly won't be investing in NOS Mullard EL34s (I do have a matched quad of some new variant (don't remember which) if / when i go to them , I'm guessing presentation will be slightly different (though i don't know that. ) They will be matched but not Blackburn Mullards. If i had to guess . If i listened tonight, and the tube fairies pulled my old ones, put in my new ones (while I was sleeping) biased them, when I woke and listened the next time, I probably wouldn't notice the difference in sound.
Wow , a lot of projecting, and guessing here.
Tempted to do it myself now, except I'd know it happened and the whole experiment would be ruined.

 

[Dandy]

We could start doing double blind experiments, but where’s the fun in that and whose ears are good enough to judge?

 

[gadget73]

I recently swapped the unmatched old Mullards out of my Rauland-Borg amps to new (well, lightly used at least), matched Shugang tubes. Honestly I think the Mullards sounded better. I might try the JJ tubes, I thought they were better than the Shugang in my Pilot. I have a different set of Shugang too, that might be worth a try. Those amps don't measure terribly well in terms of distortion but they have a certain something about them I find appealing.

 

[Dandy]

As promised, I have tried my matched set of Shuguang Treasure 6CA7s in my modified Dynaco ST70 with replacement PT and VTA board. The tubes are all matched and labeled Ia 42mA.



They sound crisper and brighter than the unmatched and unbranded Chinese-made EL34s that have been there for the past year. It is still dead quiet when idling. So, without being able to point to test results, I would accept Peterh's point that it is preferable to use a matched quad in there. Biasing is certainly easier.

But, I am grateful to peterh for his contribution to this thread, as I found out that there were some dry joints in my ST70 (a kit assembly, which I had not gone through completely when I got it about 10 years ago). Some joints were working loose as I moved the amp and the original builder's filament wiring was pretty untidy. So I did some tidying and checking while I was in there, and I'll enjoy listening to the Shuguangs in the amp for now.

 

[RS Steve]

I recently swapped the unmatched old Mullards out of my Rauland-Borg amps to new (well, lightly used at least), matched Shugang tubes. Honestly I think the Mullards sounded better. I might try the JJ tubes, I thought they were better than the Shugang in my Pilot. I have a different set of Shugang too, that might be worth a try. Those amps don't measure terribly well in terms of distortion but they have a certain something about them I find appealing.

I have older Mullards in my ST-70 and think they sound best all around. I have a couple other pairs for my Eico HF-87's I'm working on also.