Hi All,
When using a hammond "Hi-Fi" 1620 OT. Do I tie off the Blu/yel and Brn/Yel? Or do I jump them together to eliminate the "40% Screen taps for ultra-linear operation" . I going to use a Hammond PT (P-TF22723)for the D-lite build as well, and was wondering if anyone can double check with me about wiring it up. The two reds and the red/blue go to rectifier bd. The red/yellow to ground. The two greens go to filaments and the green/yellow goes to ground. Tie off the yellows. I think I have it right, I just want the reassurance I guess before I power it up. I included a few pictures of the PT and OT diagrams to refer to.
Thanks,
Dave
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You may want to not use the GN/YE on the filament tap and use 2 100 ohm resistors to ground (one from each GN filament leg) this raises the filaments off ground slightly and makes for a little less noise. Leave enough length on the other filament taps(yellows) for future use as a relay or DC fan supply.
heisthl,
I'm not sure what you mean about the filament wires. I was going to tie the GN/YE to ground and connect the two Green wires to one of the power tubes and daisy chain to all the other tubes.
heisthl,
Thanks for the diagram. Let me see if I got this, I'm not going to use the GN/YE(ct) at all. I'll just tie it off with some heat shrink. Then I'll run both green filament wires to ground with 100ohm(1/2w) resistors so it mirrors your diagram. Once that is done I will continue the filament wires to the power and preamp tubes in a daisy chain pattern. I wire stuff everyday at work but I have never built a tube amp before, so I'm always questioning myself. I just can't afford to get it wrong. So thanks again for giving me some great advice. So what is the theory behind the two 100ohm resistors anyways?
Yes you got it right. But your question about theory made me go "back to the books" and question why it would have lower noise. Answer there is no reason I can come up with - I had thought it had something to do with lifting the heaters above ground but that would only be accomplished by introducing a DC voltage at either the GN/YE or the 100 ohm junction, depending on which method you used. So I retract my suggestion and say it's ok go ahead and just use the GN/YE center tap to ground and forget the 100 ohm resistors. Here's one of many sites that advocate "lifting" the filaments above ground. http://www.lynx.bc.ca/~jc/hum.html
Be aware that this(filament hum) has never seemed to be an issue on the clone builds but all of the pictures I seen of the real HAD amps have the 2 100 ohm resistors for whatever reason.
heisthl,
I really appreciate all your help. I'm so glad I decided to build the D-lite amp. Not only is it alot of fun, guys like you are teaching me so much about it. This forum really helps with my questions. I'll check out that site, looks like there is a lot of good info there.
I going to use a Hammond PT (P-TF22723)for the D-lite build as well, and was wondering if anyone can double check with me about wiring it up. The two reds and the red/blue go to rectifier bd. The red/yellow to ground. The two greens go to filaments and the green/yellow goes to ground. Tie off the yellows. I think I have it right, I just want the reassurance I guess before I power it up. I included a few pictures of the PT and OT diagrams to refer to.
