Aleph J build guide for noobs

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Joined 2003
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23 volts of "output bias"? Where are you measuring this 23 v, at the speaker output? I assumed this since you say "zero volts across the output resistors?"

If its at speaker post, sounds like mosfet not turning on? At least you have one working channel to compare to the other.

Russellc
 
Thanks Dennis, and thanks to 6L6 for some serious help trouble shooting this, it looks like a dead ZTX550 may be the issue. I'm going to replace and will report back later this week. I can't say thank you enough to those of you who make the time to respond and help on these boards.
 
There are a TON of missing photos from that guide... casualties of Photobucket, sadly.

I need to go dig for the originals and upload them here.

Even without all the photos, I found some good tips there (and am the last post in that thread). But having the photos back would be lovely, for sure. Also in the "illustrated build guide" thread. But I'm doing my best to be exhaustive about photos in the noobs guide blog, too.
 
RCA or XLR for the noobs guide? I'm curious what you all think.


Both Please! With an explanation of best practice for handling both. I've seen some wired together without a switch, others with. Opinions abound and while there may be no clear "best" it would be great to at least have a summary of how to wire and amp for selectable RCA and XLR inputs.


I'm a mechanical engineer, and DIY audio is new for me - I learn a lot from both experienced folks and newbies on this forum. Keep up the good work!



Mike
 
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Joined 2019
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Chiming in, as always, with another thought. :D

I've already shared re: what I'd do if I were you re: XLR / RCA for your builds and possibly how you could incorporate that into the guide.

I'd personally AVOID trying to add a switch into the equation. Your guide is incredible, IMO, and it is for NOOBS. As people progress, they can add a switch if they like. It could be a fun next step, and there is enough information in other threads for someone to do it successfully. My opinion would be that if you're to add XLRs along with (not instead of) RCAs to your guide that you do it similar to the commercial model and recommend an external wire jumper. There are enough threads around chasing hum issues and other niggling things due to input wiring and other considerations. Adding complexity to a noob guide is unnecessary for a (potentially small) group of people that want special additions.

BTW - Mike... I am not implying that you're pro or con with "selectable" or using a switch. Just offering an opinion to the OPs.
 
Well, last night I traced my dead channel to a bad jfet. Luckily I had another pair of matched LSJ74s on hand because I’d ordered them incorrectly from the store originally. Took out the original JFETs and put the new pair in and she fired right up. I was able to bias to .4V and damn near .000 on the offset. Got a test run in last night and sounds great. Dead quiet at idle through my Zu speakers which claim 101db. I mean dead quiet, no hiss or him or anything. No pops or noises at turn on/turn off. Letting it cook today and will check all the numbers then button it up.

I used XLR connections only, and built this with a full dual mono power supply and I used the store soft start board. I used Antek AS-4200 400VA transformers. I used the 5U chassis and it was pretty tight with two power supplies; I had to mount the toroids vertically with brackets. In retrospect...I might have splurged for two 4U mono blocks and had more room to work. Do the dual supplies sound better? Don’t know! I also used all blue LEDs, recommend this as it gives a nice blue glow; I don’t think I’d use red/green. Glad I went with one color. Also did not drill out the front panel for LEDs, which is ok but I might eventually want to do something on the front as it’s a big expanse of bare aluminum.

This was my second build, after an ACA. I made it a little harder on myself by going with the dual power supply but honestly that didn’t add too much complexity. No way I would have been able to even attempt this without this community and resource. Thanks to all of you for your time. And thanks again to 6L6 for his support.
 

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