OK,
I think I'm getting these right finally. I changed all the transistors and purchased a few new power transistors. I started small this time. I only connected one pair of output devices. This time I could adjust my DC offset to zero. Here is my question about biasing. If you look at my attachment, here is what I have done. I Left my black meter probe on the negative speaker terminal since it connects to my zero volt point. I hit R11 on the other side and adjusted it to .2v, then back to my DC offset and adjusted to zero, then back to the R11...etc.... Here is one question, on R12, I see voltage on either side well above .2v. Is this normal?
Second, if I have .2v, then I am biasing at 2A right? .2v/.1ohm = 2A quiescent.
Am I on the right track here?
Thank you!
Blair
I think I'm getting these right finally. I changed all the transistors and purchased a few new power transistors. I started small this time. I only connected one pair of output devices. This time I could adjust my DC offset to zero. Here is my question about biasing. If you look at my attachment, here is what I have done. I Left my black meter probe on the negative speaker terminal since it connects to my zero volt point. I hit R11 on the other side and adjusted it to .2v, then back to my DC offset and adjusted to zero, then back to the R11...etc.... Here is one question, on R12, I see voltage on either side well above .2v. Is this normal?
Second, if I have .2v, then I am biasing at 2A right? .2v/.1ohm = 2A quiescent.
Am I on the right track here?
Thank you!
Blair
Attachments
An interesting circuit with less changes than Geoff's one is posted in Nelson Pass PLH pdf, in fig 4 and 5. Basically the 69 version with parallel output transistors, and dc coupled.
The differential input that Nelson proposes is also a good idea, IMO.
I havent studied Geoff's circuit btw.
The differential input that Nelson proposes is also a good idea, IMO.
I havent studied Geoff's circuit btw.
...I guess deicide67 got the amp working as the strory ends here....
The thread started with which amp JLH or Hiraga sounded better, deicide67 you built the JLH, so where are your comments on the sound???? 🙂
I just finished my JLH 2005 version project and am still gobsmacked on the sound so cannot put words to what I am hearing yet. Still have alot of listening to do.
I must say that I was not that pleased on Sunday when I switched music through it for the first time, as I had a (I won't say it to lowd) HUMMMM problem!!!!
It was all fixed by ripping out ground from PCB's, tossing neat wiring out the window and applying a true star ground prinsiple and it all cleared up and the musicallity is something spectacular!
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