I didn’t even get to the point of turning in my preamp or source equipment. As soon as I powered on the ALeph and heard hum, I stopped there and powered it down.
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I thought you have no hum while you do not connect pre, correct? If input is open (positive is not grounded), you may hear the hum, and it's normal.
The soft start replaces the thermistors in series with the transformer primaries. It does not replace the ground lift thermistor.
Yes, twist them.
You have the speaker negative going directly to the speaker jack and the positive then going to the protection board. Instead, continue the speaker negative to the protection board and then to the speaker jack.
See the practical recommendations by Hifisonix (Bonsai). The easiest way to achieve it is to take the ground off the PS board at the middle of the board. However, I think the ground lift and twisting the ground wires with the power and signal wires are probably more important. Fix that first and give it a try before trying this change.
I think your orientation is close to best. What I have found is that the locations where the wires exit the transformer point toward the front and back of the amp is the best.
But please read the Hifisonix article.
I have followed his recommendations with all three amps and one preamp that I have built and they are all quiet with my 103 dB speakers.
Many have not done that and they have had no hum problems. That may be due to having less sensitive speakers. But with very sensitive speakers, every little thing can make a difference.
Ben Mah has already noted that your audio ground and chassis ground are hard wired together. You also confirmed this. This is very likely a source of the hum.
It may seem like a good idea to have a special soft start board, and also a special speaker protection board, but these things are more likely to cause the type of problem you are having than to actually solve anything.
It may seem like a good idea to have a special soft start board, and also a special speaker protection board, but these things are more likely to cause the type of problem you are having than to actually solve anything.
If so, it's most probably ground loop as the other guys say, but I still think it's not wasting time to test your preamp hum level before doing something else.
Disconnect AJ from preamp, and measure AC voltage across positive and negative @ your preamp output RCA connector or cable end. You may have to set your meter to mV range.
Connect AJ again, and measure speaker terminal voltage in the same way. You don't have to connect the speakers.
When disconnecting/connecting equipments, turn them off. Measure while source equipment is connected and power on, but no music playing.
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Ok. I installed the thermistor inline with the PSU ground and while I was at it, I removed the speaker relay board and tidied up the wiring a bit more.
Connected to my preamp and speakers and I get very, very faint hum; about what I'm accustomed to with my 2A3 SET amplifier. So, I'm calling it good.
I sat down and listened for a little while today and I have to say, the resolution of this amplifier is really quite remarkable. I'm looking forward to spending more time with it and at some point, perhaps building the B1 with Korg Triode if that is a good match.
Thank you to everyone for your help in getting things straightened out, I truly appreciate it.
Connected to my preamp and speakers and I get very, very faint hum; about what I'm accustomed to with my 2A3 SET amplifier. So, I'm calling it good.
I sat down and listened for a little while today and I have to say, the resolution of this amplifier is really quite remarkable. I'm looking forward to spending more time with it and at some point, perhaps building the B1 with Korg Triode if that is a good match.
Thank you to everyone for your help in getting things straightened out, I truly appreciate it.
Absolutely fantastic news!!!!!!!!
Congratulations!
Continue listening and enjoying - it only gets better from here. The AJ is a remarkable amplifier.
Thanks 6L6, I can already tell this one is special and look forward to more listening.
Interestingly enough, removing the speaker relay board has minimized the turn off thump pretty dramatically to where now it's very subtle.
Hi All -
I am at the final stages of the board population for the AJ.
I am learning from this group to always re-confirm everything. I've read this thread from front to back, and clearly I may have missed something. So before I may fry some really expensive JFETs, help is appreciated.
Below is a portion of the datasheet I found for the 2SJ74. I have blindly in the past followed the "shape" on the boards for components like this, but building a few other designs, it has been stressed to always check the datasheet for which legs are which.
Link to full data sheet
https://www.mouser.com/ds/2/408/6903-18063.pdf
Per the datasheet (I think) - these would go "backwards" to the silhouette on the boards.
I pulled up the datasheet for the LSJ74, and they seem to be "opposite" and/or aligned with the board.
Could someone please confirm and/or tell me I'm paranoid/wrong
I am at the final stages of the board population for the AJ.
I am learning from this group to always re-confirm everything. I've read this thread from front to back, and clearly I may have missed something. So before I may fry some really expensive JFETs, help is appreciated.
Below is a portion of the datasheet I found for the 2SJ74. I have blindly in the past followed the "shape" on the boards for components like this, but building a few other designs, it has been stressed to always check the datasheet for which legs are which.
Link to full data sheet
https://www.mouser.com/ds/2/408/6903-18063.pdf
Per the datasheet (I think) - these would go "backwards" to the silhouette on the boards.
I pulled up the datasheet for the LSJ74, and they seem to be "opposite" and/or aligned with the board.
Could someone please confirm and/or tell me I'm paranoid/wrong
