They are xrk's SSR speaker protect boards from a group buy, the PSU is Prasi's LT4320 based CRC boards. I'm getting 24v rails under load using a 2x18v transformer. Currently cranking the bias to 450mV as my sinks are only at 44c so we'll see what happens
I measured the A/C from the power supply out and have 35mV. I raised the bias to 410mV and reset offset to 0 VDC, here is the results, 2 V output into 4 ohm load. I increased the output of the sound card to just below clipping. The 60Hz, 120Hz, 180Hz etc noise is from the Akitika 1kHz sine wave generator.
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Nice! I’ve been listening to my AJ with the recent H2 boards and am really enjoying it. Specifically, a positive phase second a little below 1% has been my sweet spot.
Good news! After a month of waiting for some more LSJ74's to arrive in the UK Aleph J no2 is alive
It is currently cooking slowly waiting for another check of bias and offset.
I think I damaged the JFETs with the zip tie when I pulled them together as the leg broke off one of them when I desoldered it..
Finally I will be able to listen to them!
Looks great! I really like your work on the front panel - what do the center controls do? Power and ?
Thanks. Cutting large holes in 10mm aluminium isn't as easy as I thought!
One switch is for power and the other one is a mute which cuts power to the SSR boards. It was the only way I could get around the switch off thump. As my speakers are active biamp then the amp will be connected directly to a compression driver and I thought it might damage them.
Spent the afternoon listening to these awesome amps and I can say that they beat any commercial amp I've owned hands down! So smooth and detailed, you can listen all day without any fatigue. I'm hearing things on music i've known for 30+ years that I knew was there but with these you can tell EXACTLY what it is! Stereo imaging is also excellent although I am using an amp per side for the first time so that might help. They also have a way of making you forget all the audiophile stuff and just get into the music though 
I was concerned at having a puny 25 watts having always used much more powerful amps but on my 95dB speakers it's easily loud enough.
Thanks to Mr Pass for sharing his genius and all who've helped on here, I would never have attempted it without this forum!
Only problem is I've now got the urge to build something again...
I was concerned at having a puny 25 watts having always used much more powerful amps but on my 95dB speakers it's easily loud enough.
Thanks to Mr Pass for sharing his genius and all who've helped on here, I would never have attempted it without this forum!
Only problem is I've now got the urge to build something again...
Spent the afternoon listening to these awesome amps and I can say that they beat any commercial amp I've owned hands down! So smooth and detailed, you can listen all day without any fatigue. I'm hearing things on music i've known for 30+ years that I knew was there but with these you can tell EXACTLY what it is! Stereo imaging is also excellent although I am using an amp per side for the first time so that might help. They also have a way of making you.....
Only problem is I've now got the urge to build something again...
Thanks for your review!
Do you mind expanding on what I have highlighted above? What amps, pray tell?
Best,
Anand.
Hi Anand,
My day job is in Pro audio so I've always stuck to pro amps and have owned literally dozens over the years from many brands. My current home amps (before the Alephs) were from MC2 Audio. IMHO the Alephs don't have the slightly glassy harshness that I've found in most others. But I guess you could argue that the Alephs are the first 'HiFi' amps that I've had. You don't find many class A amps in Pro audio!
On the last DIYAUDIO Aleph J board that I built, I get offset of 19v. Measuring voltage across r16 r17 r18 and r19 I get 1 volt instead of the recomended .5 volts...Mosfets are running hot.
rails are 24 v.
JFETs are DIYAUDIO so are Mosfets.
Can anybody suggest where to look for the problem??
rails are 24 v.
JFETs are DIYAUDIO so are Mosfets.
Can anybody suggest where to look for the problem??
audionut - I had a similar problem with my amp, I found that when I first powered it up, the offset was 18 v, when I started to adjust R27, the offset would fluctuate from 18 v to less than 1 volt. After that, I had no trouble adjusting bias and offset, until the other day after the amp had been playing music for a couple of hours, I decided to increase bias from 400 mV to 415 mV. When I was adjusting R27, a couple of times I had offset voltage of 18 v again for a split second.
I think R27 has an intermittent dead spot inside, I was going to order another Bourns pot and replace it to prevent any issues in the future.
I think R27 has an intermittent dead spot inside, I was going to order another Bourns pot and replace it to prevent any issues in the future.
