Dynaco Stereo 70

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3041118849

For anyone interested, this one looks pretty good.

 

Although it is beautiful, it's the factory built version. Most people love them kit versions....

That should go for about $460.

 

Is $750 a good price for the factory-built preamp/amp combo? That's what he's asking buy-it-now.

 

The cover over the circuit board is interesting, I've never seen that before.

Stereo-70s are notorious tube-eaters so the original tubes testing "new" suggests this amp was almost never used. That in turn suggests it's going to need all new caps and the buyer may have to choose between having a working amp or a museum piece with all of the original parts.

 

Thanks much, Bob.

 

Good point. I know what happens to caps when they are not used for a long time: My Mac 240. My C-20 was used daily as long as the last owner owned it (8yrs). The 240 needed caps replaced, the C-20 is fine for now!

 

Beware that when my C-20 finally needed caps, it took a power amp and some speakers out with it when I tried an amp that didn't have input filtering! Check the output with a DC voltmeter. If there's any significant DC voltage, get those caps changed.

Now you've been warned!

 

It will be going to my tech in the next couple of weeks to be gone over. Too large an investment not to. Thanks!!!!!

 

Do I just check the DC voltage where the Grover cables are plugged into the C20 main out RCA sockets?
What is the level that is acceptable?

Can the same test be used for power amps?
What would be the acceptable level? 0?

 

I think it is reasonable.

The ST70s go for $300-$700
Just the Mullard EL34s could be sold for ~$200-$300+

IMO It is a nice combination for the price. It is a little bit on the high side.

If you want a lower prices set up try http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3040565029&category=3284 currently less than $300 for st70, pas2, and fm3. Or search garage sales...

I may have paid too much, yet one of my ST70s cost me $699 fully restored original with all upgraded components and 3 mullards.

The preamps tend to go for ~$129 - $279. I think they came with Telefunken 12AX7s so that is $80 worth of tubes.

Eventually I will be selling a few $K of extra vintage hi fi stuff on ebay. I just like it so much it is hard to part with it.

 

Steve, is this a concern????????

Steve, what's your read on this?????

 

Van Alstine Super 70i rebuild:

http://www.avahifi.com/root/equipment/amplifier/dyna_amp_rebuild.htm

 

I've gotten lots of life out of my st70 tubes, FWIW.

Some people like to bias 'em a little lower to get more life (and to compensate for greater ac voltage now than when the amp was designed.)
David

 

Bob is correct. The Dynaco ST70 (my favorite weapon) draws an incredible ammount of juice. Sucky tubes go up QUICK in a Dynaco. Even for Chinese and Russian replacements, if you have a brand or type that does well for you, if the tubes don't go FOOM in 2 years, that's great. Keep rockin'.

NOS American stock of Tele's and Mullards are strong as hell and last for years in an ST70. A good EL34 will always show its strength in the ST70 amp. A bad one will wuss out within a short time....

 

Thanks, Bob, Its in the shop being checked. Can't take any chances with my investment!!!!!!!!!!

 

Do you think mebbe folks really oughta scrounge up some NOS GZ-34's? I've read that the Chinese ones are crappy - could that lead to premature tubular demise these days? I have a pair of MK IV's (basically each a half ST-70) that I have good old Mullard models in (one GE rebranded courtesy of a kindly forum Dynaco lover!)... I check the bias several times when I bring them outta hibernation to get as much life from the tubes as possible...