mike stehr Posted December 31, 2004 Share Posted December 31, 2004 "The bench supply is a model IP-17, the B+ will do 0-400V @ 100ma, C at 0-100v @ 1ma, 6.3v at 4 amps. Can help out for sure." Sounds like a decent bench supply. You won't be breadboarding any big hoggin' PP circuits or a Monster transmitting triode. But should be good enough for a little single ended amp and perfect for pre-amp/linestage circuits. I did trace out the Lowery 6550 PP mono organ amp circuit last night. I'll re-draw, recheck and should be good to go. I learned a few things about "pass" tubes this week from the experience..... Quote Link to comment Share on other sites More sharing options...
DRBILL Posted January 2, 2005 Share Posted January 2, 2005 "How much can you replace before it isn't what the name says?" Ask a vintage auto restorer that question! DR BILL Quote Link to comment Share on other sites More sharing options...
Marvel Posted January 2, 2005 Author Share Posted January 2, 2005 When my wife and I lived in Memphis, we had a neighbor with a garage that sat right on the property line. The back corner, with an alley behind the house. It was inpretty sad shape, and he wanted to tear it down and put up a new one in the same spot. The city wouldn't grant a variance. They did, however, let him replace portions of it. Ended up being a brand new garage anyway. I do have a 77 Sptifire that is next in line after the Dynaco! Got the replacement power tranny from Uncle Ned. The thing is massive, now the same height as the ouput trannies. I can't do anything with it until my new EL34s arrive , but it ought to run a bit cooler as the other was borderline on the specs. Marvel Quote Link to comment Share on other sites More sharing options...
dlb945 Posted January 14, 2005 Share Posted January 14, 2005 To Marvel & other watchers ... I rebuilt a pair of ST70's for a friend in the Atlanta Audio Society. I started with cleaning and replating the chassis(chrome not nickel), rust removal and repaint of transformers, original driver circuit board (Dynaco Doctor), high quality caps/resistors (matched on a bridge), new power supply capacitor board (SDS Labs), specially crafted test jacks and output terminals, and military spec hook-up wire (high-purity copper, silver plated and Teflon insulated). A picture of one of the completed ST70 units can be seen on my personal website at: http://home.bellsouth.net/p/PWP-dlblabs If any of you are futher interested, you can find rebuild pictures at: http://pg.photos.yahoo.com/ph/dlb945/my_photos How did they sound? Each amp was inserted between a Marantz 7T Preamp and a pair of Klipschorns. They sounded wonderful and created a very nice image that floated somewhat in back of the speaker plane with good (not excellent) depth and very good dynamics. I then strapped each unit for mono operation, one for the left Klipschorn and one for the right Klipschorn. The image was still back of the speaker plane but the depth increased and the dynamics were increased considerably. The power output of the strapped units must have been in the 50 watt range. Today ... I am rebuilding a ST70 for myself and should have it completed in a few weeks. I'm using the same rebuild philosophy as above. >>>Dan Quote Link to comment Share on other sites More sharing options...
Marvel Posted January 14, 2005 Author Share Posted January 14, 2005 Dan, Nice work. It looks like you went with the SS rectified PS on your rebuilds. I decided to keep the tube rectification. Still waiting on my EL34s to get here. Ned took time off for Christmas so they are a bit slow in coming. MArvel Quote Link to comment Share on other sites More sharing options...
dlb945 Posted January 15, 2005 Share Posted January 15, 2005 Marvel & Listeners ... I kept the tube rectification for the ST70 rebuilds. The SDS power board, available from Uncle Ned, allows for either SS rectifier or the tube rectification. I tried both but the tube rectifier gives what appears to be a more mellow tone and ... it is much more gentle to the other tubes during startup i.e. no startup DC surge before the tubes warm up. >>>Dan Quote Link to comment Share on other sites More sharing options...
mmmalmberg Posted February 3, 2005 Share Posted February 3, 2005 Marvel, which driver board did you use on your ST70? If it's a replacement with the same circuit as the original, then I think you could still call your amp a Dynaco, with an updated power supply. I've also fixed up a couple of ST70's recently. One, a later black-cage model, got one of Curcio's upgrade boards, but with fancier caps, and his power supply board, the same new power tranny you have, and all new sockets and wiring. The other, an early model, I just replaced the driver board, which was pretty rotten, with the original fiberglas one from the other ST70 that got swapped out for the Curcio board (I threw some new caps on that too). Both sound good, but the one with the Curcio driver board upgrade definitely has improved definition and dynamic response, and more extension of the frequency spectrum. I never rebuilt any amps before, but it was fun and rewarding. I then rebuilt the crossovers in the Heresey's (1968 models) which was much easier and even more rewarding (cheaper, easier and more obvious improvement) Now I'm looking for a good (great?) preamp for cheap for one of these. I have one PAS3, and two ST70's. And I'm using some Heresey's with the Curcio ST70, and some KEF Coda 90's with the other. So DLB945, do you think the Marantz you have is a really strong match to the ST70? Any other suggestions? Mark M. Quote Link to comment Share on other sites More sharing options...
Marvel Posted February 3, 2005 Author Share Posted February 3, 2005 Mark, My Dynaco was like your first upgrade. It was a later model with a fiberglas driver board. I replaced the same things you did. Curcio upgrade board (not premium), Curcio PS board, sockets and the heavey PS tranny from NEd. I was really only koking about whether or not it would still be a Dynaco. It sounds great for the money I have in it. I believe it is far better than the stock driver board. I'm using the 6922 tubes, but may find myself some 6CG7 as some say it is a better tube. Don't know that I really want to do any tube rolling yet. I'm on to speaker building for a while. Marvel Quote Link to comment Share on other sites More sharing options...
mmmalmberg Posted February 3, 2005 Share Posted February 3, 2005 Cool, we have just about the same amp. What are you using for a preamp? Also, guess what I have waiting for me in the garage..... a '68 Triumph GT6! Quote Link to comment Share on other sites More sharing options...
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