Aleph J illustrated build guide

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#5,902
I love AJ. Here's some artwork by one of our venerable leaders (I hope he doesn't mind if I post it)—it is detailed in the hifisonix/bonsai "quiet amp" docs—though not specific to AJ.

I wasn't ever able to get my AJ quiet. Not truly anyway—Not like M2X monoblocks currently in play. It's on my list to mono-block the AJs to see what's what—or swap out the transformer etc.. Rotating the transformer while listening to the speaks is definitely worthwhile.

Hum breaking resistors also worthwhile—didn't cure my build though.

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#5,904
I've completed my Aleph, it's operating perfectly and sounds great - no noise, no hum, just lovely music. So here's my dumb question:

Instead of adding a jumper from G to -IN on the amp boards, I just connected another wire between the negative pole of the RCA input to the ground on the amp board. Two wires soldered at the RCA, one going to -IN on the board and one going to GND.

I've done the same thing here as I would have adding that jumper, yes?
 
#5,906
VineSerf, have you resolved this?

My first thought is that Q2 is not working since the R8 voltage is way off.
I suggest replacing both Q2 (ztx550) and R8 (1k).

The D1 voltage is also a bit low, though not the cause of your R8 problem. Please
check your R5 value to ensure it's feeding enough current to D1.
 
#5,907
Thank you very much, Dennis Hui, for the response and help. I was beginning to think I'd somehow violated some DIYAudio norm, after nearly a week of resounding silence.

I did replace both Q2 and the Zener diode just before taking these measurements, but have not replaced R8. But...I think I placed a ZTX450 in Q2. As soon as I post this I'll double check the schematic and BOM. The wrong transistor certainly could explain malfunction!

Thanks again for the suggestions. I'm feeling well out of my competence zone here, being quite new to working with electronics and printed circuit boards.
 
#5,908
Q2 is a PNP transistor so a ZTX450 will not work. The standard part here is ZTX550.

20.8V across R8 (1k) corresponds to about 0.43W dissipation. That's quite a bit for a small resistor. If your resistor is a standard 1/4W part, it probably has been damaged
and drifted in value. So I recommend that you change it. (That part seems to show
some discoloration already.)

I think your D1 voltage is actually ok since it's within a couple % of the nominal value.

Cheers,
Dennis
 
#5,909
Doh!

Not sure how, but it turns out that when stuffing the board I'd swapped the transistors between Q2 and Q4. So, no surprise about the wonky measurements, I guess. I've now got the correct transistors in place, and the board powered up and adjusted just right - both bias and offset are now where they should be and the Mosfets are reassuringly warm.

I will go ahead and replace R8 as Dennis Hui has suggested. And then onward to finish wiring things and finishing the build.

And thanks again for the help. There's no way I'd be able to build these wonderful amps without the support from this forum. You folks are the greatest!
 
#5,919
It seems to me that maybe there is a grounding anomaly that these two devices together aren't happy with.

Could you try modding an RCA cable so the grounds don't connect and only the center conductors do?
For testing purposes only of course.....
 
#5,920
R6 and R30 - I'd suggest 0 ohms for the time being because this is likely a ground issue, because the amplifier works properly with other preamps...


How is audio ground connected to chassis in AJ?

Are all the devices plugged into the same power strip?
 
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