Aleph J illustrated build guide

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Demonkleaner

Demonkleaner

Member
Joined 2012
A quick update….
This amp is breaking my heart. Looks like it will relegate my beloved PP KT-88 to garage duty.
It has been my main amp since I built it a few years ago before tube prices went nuts.
A quick newb question. My power supplies
are delivering 24.5V under load and I’m running the outputs @ 450MV across the output device resistors. Case is 5U and is relatively cool. What would be a good compromise setting for sound vs
MOSFET life? MOSFETs are mount on aluminum oxide insulators and arctic silver. Thanks!
 
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L

Lorado

Member
Joined 2014
MrPete831 said:
Question: Why do the 0.47 ohm 3W resistors R16-R23 specified in the BOM cost so much? ($8 each at mouser)
Does it make any sonic difference if I use cheaper parts (still 3W 5% flame retardant metal film like the TE RR03JR47TB at $0.48 each)
Click to expand...
I know this is an older thread, but I found a very good replacement for the obsolete resistor Panasonic 0.47 Ohm 3 Watt:
Koa Speer MOSX3CT631RR47J, looks much like the old Pana (although they are pink instead of blue), and they cost US$6.76 for 25 pieces @ DIGIKEY. Ideal for the Aleph J and the DIYAudio Power Supply, etc. Datasheet https://www.koaspeer.com/pdfs/MOS.pdf

470 mOhms ±5% 3W Through Hole Resistor Axial Flame Retardant Coating, Safety Metal Oxide Film
DigiKey Part Number2019-MOSX3CT631RR47JTR-ND - Tape & Reel (TR)
2019-MOSX3CT631RR47JCT-ND - Cut Tape (CT)

Mouser's part number is 660-MOSX3CT631RR47J and they sell 100 for only US$10.80!
 
E

Eitan100

Member
Joined 2019
I plan on putting speaker protection, the Gaurdian-86 (Neurochrome) https://neurochrome.com/products/guardian-86. I was wondering whether I need the C1 input capacitor at this point. Of course, I am sure the input to the amp is clean AC. My main aim is to increase the sound quality; if one can recommend a very good capacitor that will not color my sound, I would greatly appreciate it.

​

 
Extreme_Boky

Extreme_Boky

Member
Joined 2003
Eitan100 said:
I plan on putting speaker protection, the Gaurdian-86 (Neurochrome) https://neurochrome.com/products/guardian-86. I was wondering whether I need the C1 input capacitor at this point. Of course, I am sure the input to the amp is clean AC. My main aim is to increase the sound quality; if one can recommend a very good capacitor that will not color my sound, I would greatly appreciate it.

​

Click to expand...

In addition to that link, Dennis has pointed out, the most reasonably priced and very neutral-sounding cap is AuriCap XO. I tried a lot (during my diyDAC days... some were very expensive) and this one proved over and over again to be very neutral. But, do your best to try and bypass the C1 with a wire link.

Another upgrade to this beautiful amplifier is documented here:
https://www.diyaudio.com/community/...ated-build-guide.241729/page-489#post-7560419

... in the end, I firmly settled on these TX2352 'Naked' Bulk Metal® Foil Resistors. Outstanding:
https://www.texascomponents.com/pdf/tx2352.pdf
Texas Components will cut the exact resistor value; send them an e-mail request.
 
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L

Lorado

Member
Joined 2014
Extreme_Boky said:
I was on holiday for a few weeks, so I had a day here and there I could spend on my hobby. So, logically, I looked at the Aleph J schematics again and considered what else I could do to improve the sound even further. The things I've done so far were a bypass of C1 with a copper link, removing a short circuit protection transistor and associated voltage divider resistors, and the work I put into decoupling power supply rails with polypropylene film caps and my favourite Black Gate N-type caps.

So, I kept looking at the schematics diagram hoping the Muse would strike... and then I realised that 2k trimpot that sets DC offset should be treated the same way as I/V reisistor in current-out DACs. What I had there before the mod, was a Bourns 2k trimpot, but I decided to find a suitable discrete resistor replacement to see what would happen with the sound. The more I looked at it, the more I wondered how the hell I didn't realise the importance of that 2k resistor before...?

So, I ended up using my favourite graphite film resistors, 1.2K each, 0.25W. And the result was mind-boggling. My kids thought that I bought a brand-new amplifier. What stood out was the speed, extension at both ends... and in particular the top-end extension in "all directions".

The resistor choice (carbon, metal film, Rhopoint (could be inductive!), TX2352, Holco...) would depend on your personal listening preferences and definitely on the rest of your system. I remember achieving very good I/V results with TX2352s, and TDA1541 / DDDACs... but in the case of Aleph J, the carbon films worked best for me.

So, if you do not have better things to do this 2024, put the above mod at the top of your list (of improvements).
Click to expand...
Hi Extreme_Boky,
I read this just now. By the Bourns 2k trimpot, you probably mean R7' for offset adjustment in the original Aleph J schematic?
How do you propose the new 1.2k resistors you mentioned to be installed in place of the trimpot?
Cheers, Walter
 
Extreme_Boky

Extreme_Boky

Member
Joined 2003
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Set the bias to your liking, trim the DC offset to be as close to 0 as possible.
Remove the 2k trimmer and measure its resistance.
Order the TX2352 from Texas Components
Install it as per above.
 
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spoiler

spoiler

Member
Joined 2020
There’s this little sentence in the build guide that recommends like this: “check all resistors before installing,” or something along that line.

Do it. I got lazy, and didn’t check the big Dale 3 watters, and it turns out that even though they are all marked as .47 Ohm, they all measure at .7. All 18 i bought. At more than $7 each. Gahhh! And of course i clipped the leads.
 
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