EVGuy Posted May 29, 2006 Share Posted May 29, 2006 I was at my father's today and talked him in to letting me borrow his Dynaco ST-70 amp and Dyna PAS pre-amp. I want to hear what it sounds like with the Klipschorns compared to my ss set up. It's been sitting in his basement for years, not being used, so I got it home, hooked it up and it sounds pretty nice so far. It's all original with Dynaco tubes and in excellent condition. I'm unsure on how to adjust the bias and what that even does being new to tubes. I'm going to listen to it for a while then probably send it off to Craig for his evaluation and advice on bringing it up to proper specs. So far, I like what I'm hearing. Quote Link to comment Share on other sites More sharing options...
scott0527 Posted May 29, 2006 Share Posted May 29, 2006 You have a volt meter? Ground one probe to the chassis, stick the other probe in the hole on the front that says "Biaset". Turn the pot behind the pcb board until you read 1.56 volts. You have to do this the left side, then the right side, then back to the left and so on and so until they both read 1.56 V. Here's one spot to get a manual for free, http://www.dynaco-doctor.com Quote Link to comment Share on other sites More sharing options...
Guest " " Posted May 29, 2006 Share Posted May 29, 2006 your lucky to be able to compare with no cost on your part...would like to know how you make out. Quote Link to comment Share on other sites More sharing options...
EVGuy Posted May 29, 2006 Author Share Posted May 29, 2006 You have a volt meter? Ground one probe to the chassis, stick the other probe in the hole on the front that says "Biaset". Turn the pot behind the pcb board until you read 1.56 volts. You have to do this the left side, then the right side, then back to the left and so on and so until they both read 1.56 V. Thanks for the help. I did what you advised. It was pretty close already but I kept adjusting until I got it at 1.56V , then the other side then back again but it never seems to stay right at 1.56V. Is that normal? Quote Link to comment Share on other sites More sharing options...
lwhaples Posted May 30, 2006 Share Posted May 30, 2006 Congrats! I'm thinking your Dad is happy to know his Dynaco will be enjoyed again. Larry Quote Link to comment Share on other sites More sharing options...
scott0527 Posted May 30, 2006 Share Posted May 30, 2006 Forgot to mention there should be no input on while you're doing this. Turning your preamp off is the easist way to accomplish this. Let the amp warm up for several minutes. Then get them as close to 1.56 as you can. They're supposed to stay steady although with your unit being as old as it is, a little movement wouldn't surpise me. Stay on the low side of 1.56 and you won't hurt anything. After you set it, if it's moving up and down more than a few tenths, something is wrong. I don't get too much more technical than that. I've rebuilt a couple of these over there years but that involved mostly just following instructions, removing and inserting components. If you like what you hear, their are lot of paths to take to improve the sound and make it a very reliable workhorse. They're pretty easy to work on yourself or you can have Craig go nuts on it. PS. I fixed that Dynaco-Doctor link above for manuals and other goodies. There is also some fun stuff at: http://www.dynakitparts.com Quote Link to comment Share on other sites More sharing options...
EVGuy Posted May 31, 2006 Author Share Posted May 31, 2006 It varies a little so I'm sure it's going to need a tune up. One more quick question, should I be connecting the speakers to the 16 ohm terminals using it with my Khorns? I've been listening to it all morning and I have to say that it does sound smoother, less harsh than SS does. Quote Link to comment Share on other sites More sharing options...
Colin Posted May 31, 2006 Share Posted May 31, 2006 you have some nice speakers there, can you use the Pas or ST70 only as pre and amp with the Pioneer as either pre-amp or amp? Quote Link to comment Share on other sites More sharing options...
EVGuy Posted May 31, 2006 Author Share Posted May 31, 2006 you have some nice speakers there, can you use the Pas or ST70 only as pre and amp with the Pioneer as either pre-amp or amp? Actually, I'm not using the Pas at all. I'm using a ss Mitsubishi DA-P20 pre-amp from one of my other systems. I'm not using the Pioneers right now but I could use them as a pre-amp by removing the jumpers and using interconnects from the pre-amp out to the ST-70. I understand the Pas is not well thought of. Any truth to that? Quote Link to comment Share on other sites More sharing options...
scott0527 Posted May 31, 2006 Share Posted May 31, 2006 you have some nice speakers there, can you use the Pas or ST70 only as pre and amp with the Pioneer as either pre-amp or amp? Actually, I'm not using the Pas at all. I'm using a ss Mitsubishi DA-P20 pre-amp from one of my other systems. I'm not using the Pioneers right now but I could use them as a pre-amp by removing the jumpers and using interconnects from the pre-amp out to the ST-70. I understand the Pas is not well thought of. Any truth to that? Klipschorns to 8 ohms output. I think very highly of the PAS. Just like the ST70, it's simple, easy to work on, easy to upgrade, has a phono section and sounds very nice. In stock shape, they sell for maybe $200. So you spend another $200 to have someone replace and upgrade bad/old components. For that money it's hard to find a better tube preamp with a phono section. Great introduction to tubes. For some it's all they ever need, for most, it's a beginning to bigger and sometimes better things. Quote Link to comment Share on other sites More sharing options...
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