now, when yo get them lightning properly, this is the Drek you need to celebrate with
crank it Babe!!
I'm about to connect everything---the power supply has been tested and works as expected. But I forgot to set the bias pots to 69K before installing them. Setting them now is tricky: The value keeps changing as I test it (I'm guessing because some power is being absorbed by capacitors). Should I just turn the pots way down to start? or...?
Set them to mid-point (count the turns between clicks). During your first power up, which of course is with a dim-bulb tester and/or variable AC power transformer on one channel at a time, you can quickly adjust down without fear of harm.
Connect your DMM (DCV) to one of the source resistors. Power up. If there's no concern with the DBT result, turn the pot a bit one way, then the other, to discern directionality of the increase or decrease in voltage. Mark it with a pen on the pot if you choose. Bring the voltage to the lowest point if you want, or just to a 100mV or so. Do that for the other channel.
Remove DBT, set the "bias" and null the offset.
Hi all,
I’m just in the beginning of collecting the parts for an Aleph J and was thinking about the transformer. I see a lot of people using transformers with double primaries. Is there a benefit for me living in a 240V country using a 2x120v primary transformer instead of using use a transformer with a single primary of 1x240v?
I’m just in the beginning of collecting the parts for an Aleph J and was thinking about the transformer. I see a lot of people using transformers with double primaries. Is there a benefit for me living in a 240V country using a 2x120v primary transformer instead of using use a transformer with a single primary of 1x240v?
Joppepoppo - As the esteemed ZM says, one primary will be fine.
Essentially, the choice is based on what transformer you can easily purchase - if it has dual primaries, there will be no issues, you can configure it to work perfectly, and if you can only get a single primary, that will work perfectly also
If, as ZM suggests, you intend to send the amplifier around the world on a tour, or use it as a (not very) portable headphone amp
, you could consider getting universal primaries to facilitate that. 
Of course, if you are like the vast majority of Aleph builders, you’ll build it and love it and it will play music in your house continuously.
Essentially, the choice is based on what transformer you can easily purchase - if it has dual primaries, there will be no issues, you can configure it to work perfectly, and if you can only get a single primary, that will work perfectly also
If, as ZM suggests, you intend to send the amplifier around the world on a tour, or use it as a (not very) portable headphone amp
, you could consider getting universal primaries to facilitate that. Of course, if you are like the vast majority of Aleph builders, you’ll build it and love it and it will play music in your house continuously.Thanks for the quick and informative answer. I guessed something like that but this is my first amp build (i'm more of a speaker diy:er) so when looking through posts and watching pictures and videos all kind of questions and thoughts show up. I will probably be back with more
Really looking forward to both the build and the result. Nelson Pass has always intrigued me, both as a person and amp designer.
Might as well start off by thanking all contributors to this forum as well, its easy to feel at home here
//Jakob
Really looking forward to both the build and the result. Nelson Pass has always intrigued me, both as a person and amp designer.
Might as well start off by thanking all contributors to this forum as well, its easy to feel at home here
//Jakob
I'm considering to try to display the real iq, as I bought a 3A instrument. Obviously removing internal resistor and making it adjustable . If not accurate, I'll go back to "center is ok"
customizing the scale seems easy by using the rear of the scale, coating it with primer and white acrylic paint.
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Oh boy! Just got back from a 2 week trip to visit the family and (almost) everything showed up. Now to take inventory, make sure things look good, buy a few remaining parts.
(Don't worry, I was not sliding those bags around on the carpet, and humidity is high so little static - I know that is not good practice).
(Don't worry, I was not sliding those bags around on the carpet, and humidity is high so little static - I know that is not good practice).
Need help, I have put together the Aleph J and was doing the biasing and DC offset, while making adjustment on the right channel, I noticed a smoke coming off the left channel so I immediately turned the whole thing off.
I noticed on the left channel board that the zip tie on the 2sj74 melted which indicated the FETS were getting terribly hot.
As I was troubleshooting I decided to take off the power on the left channel and continue biasing and adjusting offset of the right which I was able to achieve.
Now, I am totally at lost with the left channel, I checked for any solder issues but cant seem to find any.
Did any for the MOSFET get fried? I only have a multimeter at hand, any suggestion on where to look for issues would be much appreciated.
Thanks again.
I noticed on the left channel board that the zip tie on the 2sj74 melted which indicated the FETS were getting terribly hot.
As I was troubleshooting I decided to take off the power on the left channel and continue biasing and adjusting offset of the right which I was able to achieve.
Now, I am totally at lost with the left channel, I checked for any solder issues but cant seem to find any.
Did any for the MOSFET get fried? I only have a multimeter at hand, any suggestion on where to look for issues would be much appreciated.
Thanks again.
I am caught at a dead end at the moment, Q1A and Q1B are fried, though I still have a couple of the FETs left but I don't dare popping them in until I find the source of the problem without powering the left channel board.
I am at the moment pulling out one leg of each resistors one by one, as this is the only thing I can check with a DMM.
I am still confirming that I have them installed at the right spot on the board and will probably stop here for now until I get more suggestions on what to check next.
I have no idea if the IRFP240's are still good as I don't have a means to check them. Will probably try to get replacement as well.
Until then, I hope to hear from the experts here on my next move.
I am at the moment pulling out one leg of each resistors one by one, as this is the only thing I can check with a DMM.
I am still confirming that I have them installed at the right spot on the board and will probably stop here for now until I get more suggestions on what to check next.
I have no idea if the IRFP240's are still good as I don't have a means to check them. Will probably try to get replacement as well.
Until then, I hope to hear from the experts here on my next move.