You and ZenMod sound dangerously close to hero worshippers!Nelson Pass, The Ultimate Enabler?
I'mm sure the modest & self-effacing Mr Pass is quite embarassed by such adulation. (or probably well used to it!)
always better to line them to "deep"
with 6" high, now you're good for 80W of heat per side
I recently received my kit and ran into a couple things.
- A BD140 was missing but I saw they don’t need to match so I will order another from Mouser
- I read the build guide after pouring all my parts onto my bench and realized I could have received a kit with the JFets separated into two matched quads.
I pulled out my matching Jig and tested each one of them. I found four tightly matched around 4.07-4.08ma so I used those for one board. But I found the other four to be a bit all over the place.
3.94, 3.98, 4.04, and 4.06ma
Any concerns here with using these 4 on one board?
Thanks!
- A BD140 was missing but I saw they don’t need to match so I will order another from Mouser
- I read the build guide after pouring all my parts onto my bench and realized I could have received a kit with the JFets separated into two matched quads.
I pulled out my matching Jig and tested each one of them. I found four tightly matched around 4.07-4.08ma so I used those for one board. But I found the other four to be a bit all over the place.
3.94, 3.98, 4.04, and 4.06ma
Any concerns here with using these 4 on one board?
Thanks!
I'd like to use one of these but it's too expensive although much smaller than my existing fan cooled monster.
https://uk.farnell.com/fischer-elektronik/la-7-150-12v/heat-sink-fan-cooled-12v/dp/1222524
https://uk.farnell.com/fischer-elektronik/la-7-150-12v/heat-sink-fan-cooled-12v/dp/1222524
Sorry about that. Thanks!
No. There were enough (so far) to not have to break them into quads for each channel.
Nicely done. Since you did that awesome work, you could... if you wanted... pair 3.94 and 3.98 for J2 and J4. Others for J1/J3. Will it make a difference? Doubtful, but you did the extra work to measure. So...
You're good to go.
Thank you! Enjoy!
Edited for clarity and brevity.
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matched enough in my book
use 3.94 and 4.06 on positive input side, use 3.98 and 4.04 on negative input side
whatever you did measure those for other channel, you'll never hear difference ..... simply your criteria for JFet matching is too high
Hi guys,so I put together my jzm boards and have a problem.When I go with my variac up to 1/3 ac voltage so is about 75-80 volts I have on the bouth boards about 6,60V of dc,the leds are going on BUT I the bias is on bouth boards already on 500mV and I can set it lower with bias trimer.I can go up with bias but I can go down.And if I go up with variac Ac voltage of 100V than the bias is almost 700mV and the trimer pot is already in min.position.And is the same problem on the bouth boards identicaly with identicaly voltages on the boards.So what went wrong.I have put some old BD140 in there becose Iv become only one in my package,but I buy now new pair and put it in and the same problem.🤔Plese for help😉
Definitely post pictures, but please also read Step 60 in the build guide. Watch the video in the link. If yours is behaving similar to what is shown in the video, this is completely normal.
Critical bullet from step 60 copied below for your convenience.
The Aleph J may not behave like you expect when powering up with a variable transformer. Fellow DIYer KevinHeem was kind enough to post a video I made of a typical sequence. Aleph J Bias As Mains Voltage Is Increased Note that the bias rises to a point and then decreases. This is totally normal.
So,Jzm final setings.Everything looks OK.Iv build this in my test aleph enclosure with big heatsinks(36×26×6,5cm)and using my psu from my F6 amp in CLCLC configuration.I will try to make the final bias today and than over weekend I will put the amp in my main hifi system.Till now everything looks OK.😉
