Yeah I still don't know what I'm doing to want to push things, even if it does decrease distortion. I noticed a difference in the sound, much cleaner, sharper presentation, I noticed highs much more, which I don't love. It kind of changed the character away from what I love about this amp. So it's back to 400mV and the Nutube B1 Preamp. Overall this thing is just amazing. I know it's probably a ridiculous statement, but I actually like it more than the XA25. It has more of its own distinct character. And by the way, it drives my 86db efficiency Proacs just fine in a 500 sq ft room (with a sub, so sue me).
Ahh, I just revisited the article from Nelson's website. Then, I noticed a few more articles there, like "Audio Distortion and Feedback", which is also a timeless piece. Beautifully written and explained. Both articles go hand-in-hand quite nicely.
The Nutube B1 and Aleph J would seem like a really nice combination.
The bias in my Aleph J was around 460mV for a very long time. Then I spent a few days playing with bias settings and settled at around 400mV... However, once I invested (even) more time and money in the quality of my source (mostly its power supply...), I easily adopted higher bias as being much better sounding. So now I have my bias sitting at around 440-450mV... and this is after the amp is fully settled (warmed up).
I'd go higher... the only limiting factor at the moment is my toroid transformer rating. Power dissipation per each MOSFET is okay, and heat dissipation is as well (5U deluxe chassis).
You should consider bypassing the C1 capacitor in Aleph J. That was a huge improvement in sound quality when I tried this mod in my setup (I pretty much removed it a few days after I built the amp). I also removed the short-circuit protection transistor. Of course, make sure that you understand what these mods could do if you are not careful with the source components. In your case, B1 pre-amp might provide an additional level of safety because (I think...) it may have a sound coupling/DC blocking capacitor at the output.
Edit: Aleph J is a differential input amp. As such, using the B1 preamp would also limit its (Aleph's) potential. Get a balanced source, ditch B1 pre-amp, ditch C1 capacitor... and see what happens 🙂
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@pestoman : It's fantastic that your AJ is working well for you. The minor downside is this means many of the FW designs could also be suitable and you might be tempted to build more in the future. 
It's not ridiculous to say you like the AJ more than the XA25. Every one of the FW of PL designs has its fans, and what you like in your system is what matters.
Enjoy your AJ.
It's not ridiculous to say you like the AJ more than the XA25. Every one of the FW of PL designs has its fans, and what you like in your system is what matters.
Enjoy your AJ.
I used 5W Ohmite Audio Gold, they fit but it takes a little finagling to get things to fit. I wanted 3W but couldn't locate any.
These work quite well:
https://www.mouser.com/ProductDetai...=sGAEpiMZZMtlubZbdhIBIFrK7/wwWlYE2df8UUV1DLk=
https://www.mouser.com/ProductDetai...=sGAEpiMZZMtlubZbdhIBIFrK7/wwWlYE2df8UUV1DLk=
Hi
I am thinking of building the Aleph J monoblock. Is there any advantage over the conventional design? I built it last year with the toroidy transformer and am extremely happy. But still suffer from upgrademania.
I am thinking of building the Aleph J monoblock. Is there any advantage over the conventional design? I built it last year with the toroidy transformer and am extremely happy. But still suffer from upgrademania.
Thank you Mikerodrig27
I use the universal PSU with 60000 micF 500VA (2x22V - running the amp at ~26V) transformer. Very quite!
I use the universal PSU with 60000 micF 500VA (2x22V - running the amp at ~26V) transformer. Very quite!
60,000uF seems pretty low for total capacitance unless I am not understanding you right. That would make each of the 8 caps 7500uf?
Dual monoblocks should give you a small improvement in imaging and separation over a stereo amp. But I wouldn't expect it to be a big upgrade.
Dual monoblocks should give you a small improvement in imaging and separation over a stereo amp. But I wouldn't expect it to be a big upgrade.
Ahh, that makes more sense. You could stack the cap bank boards after the rectification stage so you get CRC filtering for each channel. Basically, power gets rectified, then sent to two cap banks each with their own CRC filter. One channel gets hooked up to one board, the 2nd channel to the other board. I haven't done this myself. However, the thought is that the two CRC boards would separate each channel's power a bit without having to purchase another chassis, transformer etc.
Regardless of how your current PSU is configured or how you plan to do the future PSU...
Whether you'll hear an 'improvement' is totally subjective. Some people swear that they'll only do monoblocks or dual mono... some swear that it's a complete waste of money, space, and time. They're all correct. The devil seems to be in the details. Some very kind people are trying to explain PSU design to me... Ugh! I still don't get it.
I'll provide my own opinion from a totally listening perspective from a novice. Dual mono doesn't sound better to me, nor do monoblocks. A better configured / better PSU can have an audible impact... to me... all other things remaining equal. After my first few First Watt builds, I built 3 identical replicas of the power supply I originally started with. I started with the 'basic', but very, very good, CRC arrangement used for a lot of FW builds on the Universal PSU. I built everything thereafter dual mono and did some A/B. Was it fun... yes. Was it a good experience... yes. Would I recommend that others do what I did... not really.
Given the relative costs of amp boards and components vs. building an entirely new PSU... I'd suggest that trying new amps is more cost effective to head toward sonic bliss. Once you find your favorite 5 or 10 amplifiers
... then fiddle with the PSUs and configurations to get that last little bit of performance / upgrade mania out of the way. Now, if monoblocks are better for your personal layout, and you want to buy another chassis too... why the heck not... If it's worth it to you to try... I say go for it! It's DIY. No matter what, you'll have some fun and learn something.
Also, maybe search for a post or two by Zen Mod and include the terms "motor run, motorrun, and motor-run." For a potential sonic benefit at a relatively low cost... it's another option to consider.
This is coming from a person that is building external PSUs to try out... so... YMMV ... grain of salt ... I'm full of it... LOL!
Added after I was typing and saw Mike's post. Mikerodrig27 knows his stuff! Listen to him. His stacking configuration seems like a good compromise for sort of a dual mono vs. getting a full additional chassis and transformer. If you have room, that's a great consideration. It does take some consideration re: wiring and layout.
Motor run caps? I need to try some of those. I will add it to the list of all the things I need to try...
