You probably used the fast-switching soft recovery diodes??
The conventional bridge rectifier square blocks would result in a greater DC voltage drop. Just make sure you mount them properly (with good heat transfer) on the bottom plate.
With Toshiba JFETs and a large heatsink area, you'll be okay. The loaded voltage will probably be 26V DC (@ 2A bias per each amp PCB).
..., or - just get the 400VA transformer at 20V AC secondary.
The conventional bridge rectifier square blocks would result in a greater DC voltage drop. Just make sure you mount them properly (with good heat transfer) on the bottom plate.
With Toshiba JFETs and a large heatsink area, you'll be okay. The loaded voltage will probably be 26V DC (@ 2A bias per each amp PCB).
..., or - just get the 400VA transformer at 20V AC secondary.
I'll probably go ahead and order the 400VA transformer, double check the rectifiers have good heat transfer and run it that way until the new transformer comes in. Much appreciate the assistance!
Hey folks, I am interested in swapping my F5 boards and trying an Aleph J. I am having trouble accessing the BOM document in post 1. If there is a BOM document about, could someone direct me that way?
(If not I am happy to populate my own from the schematic)
Also another THANK YOU to @Zen Mod and @6L6 's presence here year after year. Your patience and support are much appreciated.
(If not I am happy to populate my own from the schematic)
Also another THANK YOU to @Zen Mod and @6L6 's presence here year after year. Your patience and support are much appreciated.
^ Maybe your browser doesn't like the download link. See attached.
You may have already seen it, but a really nice walkthrough is on the site linked below. They include BoMs for all key areas of the build.
https://diyalephj.blogspot.com/
You may have already seen it, but a really nice walkthrough is on the site linked below. They include BoMs for all key areas of the build.
https://diyalephj.blogspot.com/
And it's alive!
Bit of a scare, did all the biasing, DC offset, everything good. Hooked it up to speakers and audio...nothing. Well turns out my Bluesound was being a dork and wasn't playing even though it should have been. Once I reset things, music!
First listen on my KEF LS50 Meta, which are 85 dB. sensitivity speakers. They sound AMAZING, wow! This is my upstairs background system and I drive it with a Rotel RA-12 integrated (which is a respectable unit). Using the Rotel as a preamp, and the sound difference is night and day. The speakers just come alive with the J vs. with the Rotel they 'play the music'.
Going to hook this up to the downstairs system and really let it rip.
So excited!!!
NOTE: for anyone reading this in the future, the Neutrik NA2MPMF works perfect to connect unbalanced, standard RCA cables to the XLR inputs.
https://www.neutrik.com/en/product/na2mpmf
Bit of a scare, did all the biasing, DC offset, everything good. Hooked it up to speakers and audio...nothing. Well turns out my Bluesound was being a dork and wasn't playing even though it should have been. Once I reset things, music!
First listen on my KEF LS50 Meta, which are 85 dB. sensitivity speakers. They sound AMAZING, wow! This is my upstairs background system and I drive it with a Rotel RA-12 integrated (which is a respectable unit). Using the Rotel as a preamp, and the sound difference is night and day. The speakers just come alive with the J vs. with the Rotel they 'play the music'.
Going to hook this up to the downstairs system and really let it rip.
So excited!!!
NOTE: for anyone reading this in the future, the Neutrik NA2MPMF works perfect to connect unbalanced, standard RCA cables to the XLR inputs.
https://www.neutrik.com/en/product/na2mpmf
Hi,
After 4 years Aleph J got multiple upgrades. I decided to remove C1 as suggested by few and add speaker protection board. I can highly recommend this that (big improvement in the bass region and more details and clarity).
I changed the trafos and run the amp with almost 26V rails (my speaker are 18Ohms), 400mA bias. I have to say that trafos from toroidy handle much better different loads – less voltage drops with higher current. Also DC is much more stable and do not drift like with Antek.
The monobolocks from modushop are very good. My only complain is that heat sinks and are not well aligned. This is why UMS threads do not fit to the Aleph J board. Maybe it is improved in the production version (I bought a beta version for a discounted price).
Great amp, awesome sound.
Cheers!
After 4 years Aleph J got multiple upgrades. I decided to remove C1 as suggested by few and add speaker protection board. I can highly recommend this that (big improvement in the bass region and more details and clarity).
I changed the trafos and run the amp with almost 26V rails (my speaker are 18Ohms), 400mA bias. I have to say that trafos from toroidy handle much better different loads – less voltage drops with higher current. Also DC is much more stable and do not drift like with Antek.
The monobolocks from modushop are very good. My only complain is that heat sinks and are not well aligned. This is why UMS threads do not fit to the Aleph J board. Maybe it is improved in the production version (I bought a beta version for a discounted price).
Great amp, awesome sound.
Cheers!
Attachments
Very nice! I'm surprised to see you noting an improvement in sound with the protection board...I would have assumed anything in the signal path would only harm the sound, let alone improve it.
Regardless, very nice build!
Regardless, very nice build!
Well done.
I have moved from Dynaudio Contour 1.3 to Contour 30i... 🙂. My modified Aleph J drives them with aplomb. Stunning sound.
You should remove the short circuit protection components as well (a transistor and 2 resistors).
Once the amp has settled and you are happy with the bias and offset, remove the trim pots and replace them with resistors. That will be on par with the C1 bypass mod - the major improvement in sound quality.
The mono cases allow for a very nice layout, segregation of AC wiring, and very short DC wiring (which is another reason the sound has improved). You should consider using thicker wires... though.
It was my concern as well. It was definitely an improvement in my case to remove C1 and add the protection board.
Thanks a lot for the recommendations. I read your posts about those upgrades before. It is on my todo list just after I finish Ben’s SIT amp.
Now, it is time to have a break from dyi work and enjoy the music.
See 10191...
- C1 bypass
- Remove short circuit protection
- Fixed resistors vs. pots (particularly for offset pot, if I recall due to it behaving like an I/V) - Typical builds don't include the pot for the LTP bias. I am not sure if moving to a fixed resistor for the output MOSFET bias pot has any advantage.
- There are lots of other "mods", but mainly I view them as good build practices that E_B outlines in a number of posts -
- Low output impedance PSU (and/or nice ways to utilize the "Universal" PSU to keep the ground 'clean' / less noisy).
- Short, thick wiring from PSU to amp boards and tidy AC wiring (E_B's layout shown in a number of places is incredibly "clean").
- Proper grounding scheme (speaker return to PSU vs. amp board)
The coolest DIY Philosophical High Fidelity Question of the day:
At some point, of course, the line is passed. And it has become a different amp.
But:
Exactly At WHAT point on the modification journey is the amplifier no longer really the good old smooth yet detailed sounding Aleph J?
🙂🙂🙂
At some point, of course, the line is passed. And it has become a different amp.
But:
Exactly At WHAT point on the modification journey is the amplifier no longer really the good old smooth yet detailed sounding Aleph J?
🙂🙂🙂
^ Well, maybe when the output devices were changed from the original. Everything since has been a 'variation on a theme' vs. a copy/clone. Maybe that helps reconcile the modification demons. I've often wondered how my DIY builds compare to factory units. Soon... I may know for at least one of the First Watt amplifiers.
In fairness, I don't worry too much... I just fiddle around with them and convince myself that all the mods make it "better". Don't we all?
In fairness, I don't worry too much... I just fiddle around with them and convince myself that all the mods make it "better". Don't we all?
)
In the not-too-distant future, I may get to hear an authentic First Watt J2. I will certainly tell everyone in the world when I get the chance to really do it. Now, I'm just excited to have the possibility.
Then, I'll know whether my Babel J2s are the same "kettle of fish".