Aleph-X builder's thread.
- Thread starter protos
- Start date
Help to debug my Aleph-X issue
I made the Aleph-X back in 2004 based on the hifiZen version. After that, it was in my basement not long after I completed the project due to my workload and have to taken care of my sick family. Recently, I dig it out, but is seeing an issue. This Aleph-X is a 60W version with 4 output boards on each side. I found out after turning the power on, there are two output boards on the left hand side stay cool, while other 6 output bords are working OK and hot. I checked the source resisters on the output boards, the working one is about 300 mv, while on the other cool one is less than 90 mv. I tried to adjust the VR2, but cannot lift it any higher than 120 mv. I checked the DC power to both sides are all the same at around 20V. Anyone still having the Aleph-X can share your thought what might the problem be?
I made the Aleph-X back in 2004 based on the hifiZen version. After that, it was in my basement not long after I completed the project due to my workload and have to taken care of my sick family. Recently, I dig it out, but is seeing an issue. This Aleph-X is a 60W version with 4 output boards on each side. I found out after turning the power on, there are two output boards on the left hand side stay cool, while other 6 output bords are working OK and hot. I checked the source resisters on the output boards, the working one is about 300 mv, while on the other cool one is less than 90 mv. I tried to adjust the VR2, but cannot lift it any higher than 120 mv. I checked the DC power to both sides are all the same at around 20V. Anyone still having the Aleph-X can share your thought what might the problem be?
Attachments
tomchaoda1
that's actually the board I designed, it's based on the original circuit whose author I forget (besides NP of course).
I still have quite a few of these boards. I have been away from here for almost 12 years.
I would actually like to build it again but with fets at the input since I just discovered I have several unobtanium fets 2sk170 2sj74. I gave my complete amp away for free to a lucky guy when I moved from Jersey my truck was full!
I don't remember having any issues with performance. It was actually the easiest amp I've ever built. At the moment I don't fully understand your issue, but I haven't looked at this stuff for over a decade. LOL
BTW my built was using 4 mosfets total off the main board w/o the daughter boards and using +/-13V supply. It was very toasty already maybe 50C on a case that was maybe 30 lb of Aluminum
that's actually the board I designed, it's based on the original circuit whose author I forget (besides NP of course).
I still have quite a few of these boards. I have been away from here for almost 12 years.
I would actually like to build it again but with fets at the input since I just discovered I have several unobtanium fets 2sk170 2sj74. I gave my complete amp away for free to a lucky guy when I moved from Jersey my truck was full!
I don't remember having any issues with performance. It was actually the easiest amp I've ever built. At the moment I don't fully understand your issue, but I haven't looked at this stuff for over a decade. LOL
BTW my built was using 4 mosfets total off the main board w/o the daughter boards and using +/-13V supply. It was very toasty already maybe 50C on a case that was maybe 30 lb of Aluminum
Last edited:
tomchaoda1: see my Aleph-X page in my signature. The original wiki is there in pdf format. My web page was forced to a new server about a year ago and I haven't had the time to get everything back up, but most of the content is still there.
grataku: It's been a long time - still enjoying those amps that you helped share with the world all of those years ago. I think Grey Rollins was one of the key contributors to the circuit design. He hasn't been around here in quite some time. I think he tired of the trolls at the time.
grataku: It's been a long time - still enjoying those amps that you helped share with the world all of those years ago. I think Grey Rollins was one of the key contributors to the circuit design. He hasn't been around here in quite some time. I think he tired of the trolls at the time.
Thanks for the pdf Eric! You did a fantastic job on your site putting together all the information about the amp. As important as the boards themselves for the idea to be kept alive. My job forced me to move on from DIYing I sold all my instrumentation when I relocated but I continue to listen to the music.
grataku: my web page was more useful before I had to move it. It still has a few broken links and some of the images in the later half still need to be replaced with larger, more detailed images.
tomchaoda1: for your "cold side" of the amp, I would suggest tweaking your bias pots a little while you have a meter on the source resistors for the mosfets. See what you are getting for bias. Fully biased up, you should be somewhere near the 0.4v range I think. Maybe one of your pots just corroded/oxidized a bit over time. Since the layout of the board is highly symmetric, it should be easy to compare voltages from one side of the amp to the other. Start with bias for the input differential, then bias on the output transistors. Then move on to other parts of the circuit. This should be pretty easy to track down, it will just be tedious.
tomchaoda1: for your "cold side" of the amp, I would suggest tweaking your bias pots a little while you have a meter on the source resistors for the mosfets. See what you are getting for bias. Fully biased up, you should be somewhere near the 0.4v range I think. Maybe one of your pots just corroded/oxidized a bit over time. Since the layout of the board is highly symmetric, it should be easy to compare voltages from one side of the amp to the other. Start with bias for the input differential, then bias on the output transistors. Then move on to other parts of the circuit. This should be pretty easy to track down, it will just be tedious.
You will need four channels of amplification plus the crossover.
Iirc, Nelson recommends around 100W for the bass driver, so maybe an Aleph for the mids/tweeters and something with more heft for the woofers.
(Due to a fault on my M2x I'm running my Lx-Minis with an unlikely combination of Linn and Musical Fidelity amps - all it took was a small adjustment of the crossover pots. So assuming you have an amp already, there's no reason not to build any Pass amp plus the Lx as stage one.)
Iirc, Nelson recommends around 100W for the bass driver, so maybe an Aleph for the mids/tweeters and something with more heft for the woofers.
(Due to a fault on my M2x I'm running my Lx-Minis with an unlikely combination of Linn and Musical Fidelity amps - all it took was a small adjustment of the crossover pots. So assuming you have an amp already, there's no reason not to build any Pass amp plus the Lx as stage one.)
Well, the mistaken assumption is that I already have an amp... I just built an Amp Camp amp, but that hardly counts as "more heft".
Thanks very much for your reply, it does give me the info I need. I have the budget for a pair of speakers and the Aleph, and will probably buy/build this. Adding a crossover (plus its power, plus its chassis) pushes pretty close to the limit, adding the linestage (plus control board, plus chassis, plus power)... , and then a second amp, we are well over budget.
Thanks very much for your reply, it does give me the info I need. I have the budget for a pair of speakers and the Aleph, and will probably buy/build this. Adding a crossover (plus its power, plus its chassis) pushes pretty close to the limit, adding the linestage (plus control board, plus chassis, plus power)... , and then a second amp, we are well over budget.
Last edited:
Fortunately I have a whole pile of Eurorack modules to build, which may keep me from sliding down the amp/speaker rabbit hole...
Want to build my own speakers, just need to find something I can run from just the Aleph. I'm open for suggestions (recognizing that this is not the best thread for the Q)
Want to build my own speakers, just need to find something I can run from just the Aleph. I'm open for suggestions (recognizing that this is not the best thread for the Q)