rtaylor Posted August 23, 2003 Share Posted August 23, 2003 Hey! Those look familiar. How's it going Craig? Listening to the modified MKII's and liking them Randy Quote Link to comment Share on other sites More sharing options...
NOSValves Posted August 23, 2003 Share Posted August 23, 2003 Randy, Its going great busy as can be !! Yup I bet those do look familair . Craig Quote Link to comment Share on other sites More sharing options...
rtaylor Posted August 23, 2003 Share Posted August 23, 2003 You don't sleep much do you Craig. I believe I sas a post of yours from 1AM or something this morning. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted August 23, 2003 Share Posted August 23, 2003 Yup about 6 hours a day is all these sore old bones will allow me ! I begin and end everyday on my PC answering emails and checking out the forum. Craig Quote Link to comment Share on other sites More sharing options...
Audio Flynn Posted August 23, 2003 Share Posted August 23, 2003 Dave, Whenever you get them here is fine and dandy with me. Its to bad about the Cary seller I bet that is a fine preamp. I had Rick (Audioflynn) over today and I'm pretty sure my Mark III and Ultra 4A left him stunned !! I'm sure he will chime in Sunday or so he is off to look at a nice piece of property in northern Michigan the lucky Dog. Craig Pretty much! The Marks are cool. The Mapletree pre was awesome. I had heard Craig's Scott pre...I forget the number. ...And I thought that was hot. His rebuild of the Mapletree was impressive. The system flat out smoked! Smooth, firm and real. Tried to find a flaw i could hassle him about in 2 hours could not find one. And he did my hearing test to 16 KHZ or a little more. The most fun was the cableing MMF7 TT stcok tonearm cable Interconnects NOS Valve handmade ZIP cord none of them over $ 40 a pair probably One of the best systems I have heard 30 years of audio...maybe the best. Certainly in the top 3. And not a $ 200 cable in sight. You gotta love it. HEHE Thanks Craig Rick Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted August 24, 2003 Author Share Posted August 24, 2003 As already noted, 6SN7s and 12SN7s are electrically identical. The AE-1 uses a regulated 12volt heater supply, but of course uses the 6SN7s we have been talking about. There is also a dedicated high voltage AND heater rectifier and filter circuit for each individual channel. This means that the AE-1 has two bridge rectifiers for B+, and two full-wave bridge rectifiers for the heaters. The 6SN7s are wired in SERIES after the 12 volt regulator, which puts approx. 6.3 volts across the tubes. 12SN7s could also be used in this preamp (they are also less expensive!), but the heaters would simply need to be rewired for that voltage. Easy to do. Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted August 24, 2003 Author Share Posted August 24, 2003 Series connection using a 12 volt supply on 6SN7 heaters: Pins 7 & 8 are the heater connections. Since we are normally talking about DC in this application, the + (pos.) carrying lead off the rectifier will connect to pin 7 on the first 6SN7 (I am assuming a total of two tubes). The next connection is from pin 8 on the same tube: A connection is made between this pin 8 and pin 7 of the second 6SN7 (DO NOT JUMPER pins 7 & 8 on the same tube. This connection is internal). The last connection is from pin 8 on the second tube to ground. Please don't try the above unless you have experience with high voltage circuits and electrical soldering. Erik Quote Link to comment Share on other sites More sharing options...
NOSValves Posted August 24, 2003 Share Posted August 24, 2003 Erik, Actaully in this preamp you have 4 tubes to heat ! it is now setup so the 12SN7's get 12V and then pass it to the 6SC7 (phono) just as you described. So I would think to run 6SN7 in place of the 12SN7 you would feed 12V into each 6SN7 pin 7 and then just jumper pin 8 of the 6SN7 to pin 7 of the 6SC7 then ground pin 8 of the 6SC7. Is this correct ? So basically you running each channel in series starting with 12 votls the first tube takes 6V and passes the remaining 6V to the next. I believe this also could be done starting with 24V and run them all in series together. Craig Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted August 24, 2003 Author Share Posted August 24, 2003 Craig: Yeah, that sounds right. Are you just wanting to experiment with 6SN7s, or somethin? Or is the 12SN7 bad and you don't have a replacement? Good luck in any case! Erik Quote Link to comment Share on other sites More sharing options...
NOSValves Posted August 25, 2003 Share Posted August 25, 2003 Erik, Just playing around at this point. I have to order some more permanent parts for the preamp. I did some temporary adding and fiddleling with power supply filtering. Now that I have found a combination that seems to work for me I'll order some better fitting parts to replace the tagged on values I added. So while I'm in there I might give the 6SN7 a whirl and see if there is any sonic difference. I bet there isn't. I'm also going to try and score some 12SX7's which some say are the holy grail of the 12SN7 and 6SN7 family of tubes. Craig Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted August 25, 2003 Author Share Posted August 25, 2003 Sounds good Craig -- good luck! Please let me know if and when you get going on the Horus. I am actually considering some experimentation with the SS replacement for the 5AR4 -- a few different designs are made the just plug into the rectifier socket, only the heater supply is of course no longer used. Erik Quote Link to comment Share on other sites More sharing options...
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