PDA

View Full Version : Dynaco Stereo 70

Ronflugelguy
08-14-2003, 06:29 AM
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3041118849

For anyone interested, this one looks pretty good.:cool:
Sckott
08-14-2003, 07:14 AM
Although it is beautiful, it's the factory built version. Most people love them kit versions....

That should go for about $460.
Gary
08-14-2003, 07:16 AM
Then you gotta get a preamp. The seller has one, apparently....
Ron Stone
08-14-2003, 08:26 AM
Is $750 a good price for the factory-built preamp/amp combo? That's what he's asking buy-it-now.
Bob Olhsson
08-14-2003, 08:37 AM
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.
Ron Stone
08-14-2003, 09:05 AM
Thanks much, Bob.
Ronflugelguy
08-14-2003, 10:45 AM
Originally posted by Bob Olhsson
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.

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!
Bob Olhsson
08-14-2003, 04:05 PM
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!

:-)
Ronflugelguy
08-14-2003, 04:11 PM
It will be going to my tech in the next couple of weeks to be gone over. Too large an investment not to. Thanks!!!!!
Clay
08-14-2003, 09:04 PM
Check the output with a DC voltmeter. If there's any significant DC voltage, get those caps changed

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?
Clay
08-14-2003, 09:40 PM
Is $750 a good price for the factory-built preamp/amp combo? That's what he's asking buy-it-now.

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.
Ronflugelguy
08-17-2003, 07:03 PM
Originally posted by Bob Olhsson
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!

:-)

Steve, what's your read on this?????
Pepzhez
08-19-2003, 12:14 AM
Van Alstine Super 70i rebuild:

http://www.avahifi.com/root/equipment/amplifier/dyna_amp_rebuild.htm
bassface
08-19-2003, 02:58 PM
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
Sckott
08-19-2003, 03:33 PM
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....
Ronflugelguy
08-20-2003, 06:41 PM
Originally posted by Bob Olhsson
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!

:-)

Thanks, Bob, Its in the shop being checked. Can't take any chances with my investment!!!!!!!!!!
indy mike
08-20-2003, 07:11 PM
Originally posted by Sckott
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....

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...