Since you're on a roll, I would heartily recommend transforming that Aleph J of yours with a dual-mono power supply. You will be amazed 😉
Hi, I have a problem with my left channel. Right channel working perfectly. All started well. First power up fine and adjusted both offsets to 0v across the terminals, both bias to 4v. Left for hours, tweaked, perfect and stable. Connected to DAC, speakers, blew 1.25A fuse. Changed to 1.5A fuse. All good except for big hum on left channel.. Plays music but bad hum left side. Can no longer set left offset to zero. Now about 8v! No visible issues I can see. Many voltage measurements on attached schematic. Bad channel measurements on top. Good channel measurements on bottom for reference. Seek your guidance. I don’t know where to go from here..
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8V on input JFet gate ?
anyway , Aleph CCS is not conducting , while lower side is open , thus -8V on output terminals
supernice that you already attached schm with measurements ..... that also is confirming importance of precise explanations - you wrote that offset is 8V (positive) but schm is fully informative 🙂
besides checking upper mosfets for shorts , regular ( if not unnecessary) checking for conductivity of mosfets to heatsink , check or just replace Q4
also usual thing - visually etc. check for proper solder , no shorties etc.
be sure that DAC is output offset -free
anyway , Aleph CCS is not conducting , while lower side is open , thus -8V on output terminals
supernice that you already attached schm with measurements ..... that also is confirming importance of precise explanations - you wrote that offset is 8V (positive) but schm is fully informative 🙂
besides checking upper mosfets for shorts , regular ( if not unnecessary) checking for conductivity of mosfets to heatsink , check or just replace Q4
also usual thing - visually etc. check for proper solder , no shorties etc.
be sure that DAC is output offset -free
Thanks Zen Mod. Yes, -8.7v at the output. I’ve spent an hour or so looking at everything with a magnifying glass and can’t see anything that looks cooked..
What’s the best method to check the mosfets for shorts or conductivity to heat sink? I had the whole board and mosfets off the heat sink completely to inspect the back side again. I powered up for 10-15 seconds and still got -8.7v at the output.
What’s the best method to check the mosfets for shorts or conductivity to heat sink? I had the whole board and mosfets off the heat sink completely to inspect the back side again. I powered up for 10-15 seconds and still got -8.7v at the output.
DMM buzzer will buzz with everything less than 30 (or so ) ohms
use it
with amp off , poke between mosfet pins to check for shorts ; if buzzes at first , wait to allow caps filling .....
same applies to mid pin ( drain ) of mosfets , vs. case/heatsink
also same applies to Q4 , but - with cheap parts , if in doubt - don't measure , just replace
use it
with amp off , poke between mosfet pins to check for shorts ; if buzzes at first , wait to allow caps filling .....
same applies to mid pin ( drain ) of mosfets , vs. case/heatsink
also same applies to Q4 , but - with cheap parts , if in doubt - don't measure , just replace
Is q4 correctly oriented? Carefully check the Q4 biasing resistors and the trim-pot.
Are the input JFETs damaged?
Are the input JFETs damaged?
The first input JFET (one on the left, as you are looking at the circuit diagram) might be faulty.
Roo2, sounds like you're on the path to an answer with the mighty Zen Mod on your side.
Given the super neat job you did with the B1 NuTube, I'm sure you'll fix things soon. I forgot to test it with one of my ACAs. I thought you might like to try your B1 hooked up to an ACA while you sort out the Aleph. The B1 is a very capable piece of kit. Bodes well for when your Aleph is sorted.
Given the super neat job you did with the B1 NuTube, I'm sure you'll fix things soon. I forgot to test it with one of my ACAs. I thought you might like to try your B1 hooked up to an ACA while you sort out the Aleph. The B1 is a very capable piece of kit. Bodes well for when your Aleph is sorted.
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Thanks guys. I’ll check the mosfets for shorts tomorrow. Late here now.
I’ve ordered some Q4 ZTX450 transistors. I’m sure the orientation is ok as it appeared to work nicely for a few hours before I tried to play music through it.. I hope it’s this..
JFETs... I’m not good with desoldering and those things are hard to buy, expensive.. I hope not these please..
I’ve ordered some Q4 ZTX450 transistors. I’m sure the orientation is ok as it appeared to work nicely for a few hours before I tried to play music through it.. I hope it’s this..
JFETs... I’m not good with desoldering and those things are hard to buy, expensive.. I hope not these please..
B1 is for Sissies
same as ACA
😀 that's why I went ACA mono blocks to start and then went hard core to the Aleph once I'd kicked off the trainer wheels. Well worth going the next step.
Plenty of inspiration and good advice here to help.
Roo2
at least check them with diode/buzz meter in situ , compare with good channel
check torque of mosfets , beside everything else , and be sure to have some safety against de-torque of screws (thermal cycling is tricky thing)
Pa is using nuts equipped with springy washers , while we Mortals are using separate spring washers
at least check them with diode/buzz meter in situ , compare with good channel
check torque of mosfets , beside everything else , and be sure to have some safety against de-torque of screws (thermal cycling is tricky thing)
Pa is using nuts equipped with springy washers , while we Mortals are using separate spring washers
Having same thought here, and with my M2 as well. I bought Deluxe 4U chassis for those two builds, so will require more chassis of the Deluxe 5U. to have plenty of room. I don't like crammed builds!
This has lead me to wonder about cannibalizing both of their power supplys and building a moving portable power supply, but I use 3 amps all the time....I just hate messing with an amp that works!
Russellc
I used two different 400mm deep chassis for my M2x and Aleph J. I went with a smaller 2.5U tall chassis for the M2x, and kind of painted myself into a corner with that one. I was mostly concerned with keeping as much distance as possible between the Edcor transformers and the main power transformer, which was covered by its own steel case. I have used a couple tricks to minimize the channel interaction through the power supply rails, but it still sounds less expansive and transparent than the dual-mono Aleph J.
The chassis I used for the Aleph J is 3.5U tall, 400mm deep and 320mm wide on the inside. It's a bit smaller than the Modushop 4U, 400mm deep chassis sold on the diyAudio store. Getting two separate power supplies to fit was challenging, but manageable. Transformers are Antek 300VA w/ 20V secondaries, and the PSU boards are CRCRC from a group buy a while back.
I originally intended to use a a set of "ideal" rectifier boards, but started out with LVP 2560 bridges in GSIB-5S cases. I'm happy with the +/-24.2V rails so far, and haven't felt the need (yet) to experiment with alternate rectifiers.
The chassis I used for the Aleph J is 3.5U tall, 400mm deep and 320mm wide on the inside. It's a bit smaller than the Modushop 4U, 400mm deep chassis sold on the diyAudio store. Getting two separate power supplies to fit was challenging, but manageable. Transformers are Antek 300VA w/ 20V secondaries, and the PSU boards are CRCRC from a group buy a while back.
I originally intended to use a a set of "ideal" rectifier boards, but started out with LVP 2560 bridges in GSIB-5S cases. I'm happy with the +/-24.2V rails so far, and haven't felt the need (yet) to experiment with alternate rectifiers.
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I think my next steps are:
1. Get a 2nd chassis and build another PSU, so I can always have one FW amp up even while I'm working on one. I have one in the cart...
2. Get the SissySIT, F4, and F5 tried out and try to A/B some amps. I'm an
3. Get a third (and dear heavens hopefully the last) chassis - and figure out how to build dual mono. At the same time, convert at least one chassis to switch between XLR inputs and RCA for those amps that may benefit. Get all three chassis set up as identically as I can.
4. Maybe see what the fuss is about re: motor run caps. Learn what they're supposed to do and give them a try.
5. Bask in the glow that I'll have 3 complete / identical chassis to swap amps in and out of to my heart's content. One of them can maybe be used for a burning amp or another projects that don't use the standard FW PSU and guts.
Baby steps.
On another note, I spent the morning with the Aleph J. I wish my "audio memory" were worthy. There's no way I could offer a thoughtful comparison between the M2x (with any of the daughter cards) and the M2x.
I can say with some level of confidence that cymbals have JUST the right sound to me. It's kind of uncanny. Someone (Maybe ZM or Jim) posted that picking a FW amp is kind of like walking into a garage full of Ferraris and trying to pick a favorite. Now, I think I understand. 😀