Successful Aleph J build
My apologies to everyone first. I don't know what I was smoking last night. The fuse did blow two times. Could be because the transformer wire came out and touched something or just the power line voltage had a surge.
After I replaced the fuses and disconnected the amp and just checked the power supply, fuse did not blow. Led me to believe that there was something wrong with the amp. My first mistake.
Once I connected the bulb in series and when the light bulb started glowing bright enough, I made the second mistake - that the light should not glow at all (from my F5 testing hangover and due to whatever I was smoking).
With disappointment of having incorrectly assumed that the amp board has gone bust...I went about assembling another board. Tested the board with the bulb and had the same behavior as the supposedly "bad board". That's when the light bulb in my head truly came on. That the series bulb is not going to go off but will remain lighted (unlike a F5) when testing a Aleph J.
Then went about disconnecting the light bulb, adjusted the offset, connected the preamp input and speaker. Played music. Absolutely wonderful sound. Full impact of Mr. Pass's brilliant design. Played for sometime to let the electronics settle, readjusted the offset and now I am all set with two fully working boards.
Now the story of the discarded board - Nothing wrong with it. Works perfectly, after having replaced C1.
To sum up the experience, there were only two major problems in my Aleph J build. Both are related to faulty components. First one is using fake FETs and the second one being a faulty decoupling capacitor C1. Just that. Everything else I did was a load of BS.
Thanks for all the help and advice. This forum is super. I will come back after I have my pot, with more questions
Cheers.
My apologies to everyone first. I don't know what I was smoking last night. The fuse did blow two times. Could be because the transformer wire came out and touched something or just the power line voltage had a surge.
After I replaced the fuses and disconnected the amp and just checked the power supply, fuse did not blow. Led me to believe that there was something wrong with the amp. My first mistake.
Once I connected the bulb in series and when the light bulb started glowing bright enough, I made the second mistake - that the light should not glow at all (from my F5 testing hangover and due to whatever I was smoking).
With disappointment of having incorrectly assumed that the amp board has gone bust...I went about assembling another board. Tested the board with the bulb and had the same behavior as the supposedly "bad board". That's when the light bulb in my head truly came on. That the series bulb is not going to go off but will remain lighted (unlike a F5) when testing a Aleph J.
Then went about disconnecting the light bulb, adjusted the offset, connected the preamp input and speaker. Played music. Absolutely wonderful sound. Full impact of Mr. Pass's brilliant design. Played for sometime to let the electronics settle, readjusted the offset and now I am all set with two fully working boards.
Now the story of the discarded board - Nothing wrong with it. Works perfectly, after having replaced C1.
To sum up the experience, there were only two major problems in my Aleph J build. Both are related to faulty components. First one is using fake FETs and the second one being a faulty decoupling capacitor C1. Just that. Everything else I did was a load of BS.
Thanks for all the help and advice. This forum is super. I will come back after I have my pot, with more questions
Cheers.
Thanks Sam. At the moment you can listen to my F5 amp. You can listen to AlephJ once I mount the boards into it's enclosure.
I am planning to use two channels of F5 and two channels of AlephJ in a biamped configuration with my Altec Onkens. Wish I could build a B5....that will be the perfect setup.
Cheers.
Hello,
I need help with Aleph J...
What is the reason of changing voltage in output?
When I use input "+IN", the output shows about 300 mV and it's going down fast to about 100mV.
I set 10mV with potentiometer, but it changing again +/- 20mW
When i use input "-IN", everything is alright.
Could it be that my JFets are not matched very well, or maybe the 2sj109 is bad?
Thank you.
I need help with Aleph J...
What is the reason of changing voltage in output?
When I use input "+IN", the output shows about 300 mV and it's going down fast to about 100mV.
I set 10mV with potentiometer, but it changing again +/- 20mW
When i use input "-IN", everything is alright.
Could it be that my JFets are not matched very well, or maybe the 2sj109 is bad?
Thank you.
Hello again,
I tried to make it like you said - same problem, the output voltage is changing anyway. I do not use balanced inputs, I use RCA.
As I mentioned the problem is when I use input "+IN". The voltage is changing like this:
I turn on the amp, the output voltage – about 330mV and going down, waiting about an hour, when amp. reaches 50-60C temp, then with potentiometer I set 20…30mV in output. After 15 min. it change to –(minus)40..55mV, next 20 min. it changes to positive potential about +15mV, and so on and on (the numbers are given always changing, it just an example).
One more thing, for example I set output voltage to aprox. 0 and turned off the amp. When I turn it on output voltage is 330mV again. It just fails to set.
With the input “-IN” there are no such problems. I noticed when I just turn Amp, output voltage is showing aprox. 35mV and for an hour voltage stops to 10…8 mV and don’t go any further up or down , like it should be.
Thanks
I would like to ask you one more question.
Can i use (it doesin't matter in which input) 1k resistor instead of 22k, that the input gain woud be more sensitive.
Thank you
gain is set with ratio of 220K/22K
replacing 22K with 1K sounds like trouble for me .............. asking more gain from circuit than circuit even have OLG
how much more gain you need ?
anything above 15x (23.5db) is already letting steam out ........... taking in account output impedance and few other things
replacing 22K with 1K sounds like trouble for me .............. asking more gain from circuit than circuit even have OLG
how much more gain you need ?
anything above 15x (23.5db) is already letting steam out ........... taking in account output impedance and few other things
gain is set with ratio of 220K/22K
replacing 22K with 1K sounds like trouble for me .............. asking more gain from circuit than circuit even have OLG
how much more gain you need ?
anything above 15x (23.5db) is already letting steam out ........... taking in account output impedance and few other things
I did like you said, and now output voltage is like it shoud be, everything is just fine. So thank you for your time for me and advises.
Good luck!
I did like you said, and now output voltage is like it shoud be, everything is just fine. So thank you for your time for me and advises.
Good luck!
I'm glad to hear that ;
but - you didn't answer to this :
One thing I've wondered about that i now want to ask you experts:
If you halved the output power of the Aleph J by removing one mosfet pair, would the distortion at 1w/10w increase, decrease or be roughly the same? (halving bias to adjust for halv mosfets)
Why I wonder is because I probably won't need more than 1-10w and thus wonder if I could halve power output without disadvantages or if it's better to keep the amp at 20-25w.
If you halved the output power of the Aleph J by removing one mosfet pair, would the distortion at 1w/10w increase, decrease or be roughly the same? (halving bias to adjust for halv mosfets)
Why I wonder is because I probably won't need more than 1-10w and thus wonder if I could halve power output without disadvantages or if it's better to keep the amp at 20-25w.