Wow! Thanks again for all the compliments and feedback, much appreciated. Replies follow.
Agreed, I used thermal grease between the bridge rec and bottom plate and as these are low Vf ~.75VDC, power dissipation is very low. I was also thinking of leaving the bottom plate intact, insulate the xfmr with proper material, and vent the center cap holding it, and drill some more vent holes in the bottom plate.
If this were an 400W into 2 ohm amp I would agree, but as this is only a 25W amp, and idling at ~2A, I believe 18ga wire is adequate. After all, the R47 resistor leads are ~24ga and the length of internal wiring is short.
I setup the copper plate as it is to reduce the ripple current from the first set of caps from getting into the ground, keeping the ground as a single point and yes the speaker returns go right to that center connection point on the plate, not the PC board. Quasi snubber in place right at the bridge rec.
They actually are soldered, I just left the insulation on them, you can see a few of them where I slightly overheated while soldering.
So again, thank you for all the great feedback and ideas, it's on the bench warming up again but with the xfmr sitting up on blocks to see how much cooler it runs. I will probably drill out some more holes in the bottom plate then sit down for a listening session.
I'll update later today.
Cheers
Agreed, I used thermal grease between the bridge rec and bottom plate and as these are low Vf ~.75VDC, power dissipation is very low. I was also thinking of leaving the bottom plate intact, insulate the xfmr with proper material, and vent the center cap holding it, and drill some more vent holes in the bottom plate.
The DC rails & returns, and the speakers' hookup wire, is very thin. I'd go with at least triple the cross-section. Even better, you could extend the copper plate to cover all 4 capacitors' screws
The transformer, if damped correctly (quasimodo snubber) , could dissipate a lot less heat... The speakers return wire should go straight to that copper plate.
If this were an 400W into 2 ohm amp I would agree, but as this is only a 25W amp, and idling at ~2A, I believe 18ga wire is adequate. After all, the R47 resistor leads are ~24ga and the length of internal wiring is short.
I setup the copper plate as it is to reduce the ripple current from the first set of caps from getting into the ground, keeping the ground as a single point and yes the speaker returns go right to that center connection point on the plate, not the PC board. Quasi snubber in place right at the bridge rec. kilohertz, that's a lovely clean build
The only change I would make is to remove the insulation from the crimp terminals and solder them for long term reliability.
They actually are soldered, I just left the insulation on them, you can see a few of them where I slightly overheated while soldering.
So again, thank you for all the great feedback and ideas, it's on the bench warming up again but with the xfmr sitting up on blocks to see how much cooler it runs. I will probably drill out some more holes in the bottom plate then sit down for a listening session.
I'll update later today.
Cheers
Last edited:
I finally have just about finished the Aleph J. I just need to install the blue LED and find the top cover. All the proper parts have been installed, all the .47Rs as they should be, all wiring is Teflon coated silver plated including the input coax. All of it came from the Boeing surplus store over 25 years ago, what a treasure trove that was. I even laced the wiring, something I learned back in the early 80's at BCIT.
I am very happy with the static results so far. Heat sinks ~55C with idle at 1.9A. The LVB2560 bridge rec. stays at the same temp as the chassis, about 45C. ~75mV of ripple on the supply and ~3mV AC on the output with inputs open. AC draw from the wall 220W.
A few pictures of it going together...I will post a few more once I get all the test leads out of it.
Cheers
Waxed string cable wrapping is a welcome sight. Looks so much better than nylon cable ties and is very effective.
I was a Hydropower Electrician for many years and am familiar with the technique, but let myself get lazy and craftsmanship usually suffers then.
You've inspired me to look for some waxed string.
Your job looks very good overall, my compliments.
I just did a quick Google search and there are many vendors selling waxed lacing cord. Also a big "retro" movement to get away from zap straps, and get back to this lost art form.
For example...
The Lost Art of Lacing Cable - The Broadcast Bridge - Connecting IT to Broadcast
Cheers
For example...
The Lost Art of Lacing Cable - The Broadcast Bridge - Connecting IT to Broadcast
Cheers
This is true, however you can get to this point of disassembly in 3 minutes, as I just did so that I could drill another 40 holes in the bottom plate, then simply remove the boards from the sinks leaving all the wiring intact.
BTW, I forgot to include you Mark in my earlier thank you message to all who have helped out here. Your work on transformer/rectifier ringing reduction is most appreciated.
It's all back together and am making another thermal test...going to start listening in a couple of hours.
Cheers
Attachments
I just did a quick Google search and there are many vendors selling waxed lacing cord. Also a big "retro" movement to get away from zap straps, and get back to this lost art form.
For example...
The Lost Art of Lacing Cable - The Broadcast Bridge - Connecting IT to Broadcast
Cheers
Learned something new today, thanks for posting this
Well, maybe Mr Levinson should have paid closer attention to the long haired engineer when he was in your building in 197X. Seems the long hair won over the short curly hair.
I spent a very long time listening to 3 amps tonight….Nelson’s Aleph J, ML's No.332 and an offshore 805 SET tube amp, and the results weren’t what I was expecting.
I started with the Aleph, and was really discouraged when I first heard it, I thought something was wrong, it just sounded awful, like something was missing, no highs, muffled, WTH I thought, gain was very low, not like I have been told, that it is a high gain amp. I listened for a few minutes then thought I better try the No. 332 for comparison, after all, it’s a “Levinson”. Well, it didn’t sound any better, in fact it was worse. Turns out, warm up time is really important, and the Aleph had zero hours on it and the 332 had only been on for 20 minutes.
An hour later I now had 3 amps going in the rotation, as mentioned above, and observed the following.
The Aleph turned out to be amazing, it started out sounding like a Dyanco ST70/PAS3 combo, not bad, very musical, but veiled, just dull, very musical but dull, but after it warmed up, it came to life. Then I switched to the 332, and after a few minutes found I wasn’t listening to the music, it was boring, but found myself thinking about what it was like for Mr. Levinson to be in the Threshold building, what those two must have talked about. I went back to the Aleph and the music just seemed to jump out at me. I found myself just listening, very musical, it made me happy. I will say however that it is very sensitive to interconnects, I tried 3 before I found one it was happy with.
I then moved to the tube amp, a JAS Array 2.1, a 150 lb 805 SET beast. It immediately jumped out as the winner in terms of depth, clarity, and dynamics. It just was more musical. The way the Aleph was more musical than the 332, the Array, was again, just more musical, better depth, dynamics, toe tappingness.
So, one must realize that this is very subjective, and results will vary WILDLY with different systems. My system (currently) consists of a Technics SP-10, Audio Technica AT1005 arm, Shure V15 IV cartridge (don't bug me, I play a lot of old jazz records and it's tough as nails), I do have many better but they are so much more fragile. Preamp is a Yaqin MS-12B and the interconnects that worked are some old home made Mogami 2534 based cables. Speakers are Big Red monitors with Altec 604-16LN drivers and Mastering Labs crossovers, 16 ohms.
It’s late, I’m tired and off to bed, I will most likely repeat the whole event again this weekend…I sure am happy with the Aleph though, it’s amazing that such a simple amp can provide so much musical pleasure. Good job Nelson, I really appreciate your genius.
Cheers
PS if anyone wants to see the pictures from 197X I am referring to with Mark L. in Thresholds building, I will post the link. There is a GREAT picture in the file of Nelson, and I'm guessing his wife, (or girlfriend at that time) very 70's.
I spent a very long time listening to 3 amps tonight….Nelson’s Aleph J, ML's No.332 and an offshore 805 SET tube amp, and the results weren’t what I was expecting.
I started with the Aleph, and was really discouraged when I first heard it, I thought something was wrong, it just sounded awful, like something was missing, no highs, muffled, WTH I thought, gain was very low, not like I have been told, that it is a high gain amp. I listened for a few minutes then thought I better try the No. 332 for comparison, after all, it’s a “Levinson”. Well, it didn’t sound any better, in fact it was worse. Turns out, warm up time is really important, and the Aleph had zero hours on it and the 332 had only been on for 20 minutes.
An hour later I now had 3 amps going in the rotation, as mentioned above, and observed the following.
The Aleph turned out to be amazing, it started out sounding like a Dyanco ST70/PAS3 combo, not bad, very musical, but veiled, just dull, very musical but dull, but after it warmed up, it came to life. Then I switched to the 332, and after a few minutes found I wasn’t listening to the music, it was boring, but found myself thinking about what it was like for Mr. Levinson to be in the Threshold building, what those two must have talked about. I went back to the Aleph and the music just seemed to jump out at me. I found myself just listening, very musical, it made me happy. I will say however that it is very sensitive to interconnects, I tried 3 before I found one it was happy with.
I then moved to the tube amp, a JAS Array 2.1, a 150 lb 805 SET beast. It immediately jumped out as the winner in terms of depth, clarity, and dynamics. It just was more musical. The way the Aleph was more musical than the 332, the Array, was again, just more musical, better depth, dynamics, toe tappingness.
So, one must realize that this is very subjective, and results will vary WILDLY with different systems. My system (currently) consists of a Technics SP-10, Audio Technica AT1005 arm, Shure V15 IV cartridge (don't bug me, I play a lot of old jazz records and it's tough as nails), I do have many better but they are so much more fragile. Preamp is a Yaqin MS-12B and the interconnects that worked are some old home made Mogami 2534 based cables. Speakers are Big Red monitors with Altec 604-16LN drivers and Mastering Labs crossovers, 16 ohms.
It’s late, I’m tired and off to bed, I will most likely repeat the whole event again this weekend…I sure am happy with the Aleph though, it’s amazing that such a simple amp can provide so much musical pleasure. Good job Nelson, I really appreciate your genius.
Cheers
PS if anyone wants to see the pictures from 197X I am referring to with Mark L. in Thresholds building, I will post the link. There is a GREAT picture in the file of Nelson, and I'm guessing his wife, (or girlfriend at that time) very 70's.
Attachments
Last edited:
Well... I did mention a few things:
- do not use silver-plated wire. Use solid core copper, or wide, pure silver ribbons - annealed
- use much thicker cross-section wire (or ribbons, as mentioned above)
- use polystyrene cap (10pF is the minimum that can be found in polystyrene flavour of dielectric), instead of silvered mica ... or, use two wires, twisted together, approximately 5cm long (silvered mica sounds awful). This one I did not mention before
- the wiring should be as short as possible (the braided wiring in your amp looks amazing... but the wiring should be as short as possible)
- the 220uF caps should be Black Gate F types... if you can find them. Or, leave the Silmics II, but remove the bypass caps. By the way, those Silmics II have degraded in quality dramatically... they sound terrible, compared to old Silmics II that I removed from some high-grade Denon gear. I will not be buying Silmics II any more.
- the 1uF cap can be removed, but be careful... with DC at the input. Also, the DC offset, without this cap, will never really be 0... but would drift 10-20mV up/down. Not a big deal, compared to the sound benefit if the cap is removed, especially in improvement re low frequencies definition and extension.
- remove the short circuit protection; a transistor and both resistors.
The only thing I can not get out of Aleph J, to my satisfaction, is the depth perception of the soundstage... no idea why...
- do not use silver-plated wire. Use solid core copper, or wide, pure silver ribbons - annealed
- use much thicker cross-section wire (or ribbons, as mentioned above)
- use polystyrene cap (10pF is the minimum that can be found in polystyrene flavour of dielectric), instead of silvered mica ... or, use two wires, twisted together, approximately 5cm long (silvered mica sounds awful). This one I did not mention before
- the wiring should be as short as possible (the braided wiring in your amp looks amazing... but the wiring should be as short as possible)
- the 220uF caps should be Black Gate F types... if you can find them. Or, leave the Silmics II, but remove the bypass caps. By the way, those Silmics II have degraded in quality dramatically... they sound terrible, compared to old Silmics II that I removed from some high-grade Denon gear. I will not be buying Silmics II any more.
- the 1uF cap can be removed, but be careful... with DC at the input. Also, the DC offset, without this cap, will never really be 0... but would drift 10-20mV up/down. Not a big deal, compared to the sound benefit if the cap is removed, especially in improvement re low frequencies definition and extension.
- remove the short circuit protection; a transistor and both resistors.
The only thing I can not get out of Aleph J, to my satisfaction, is the depth perception of the soundstage... no idea why...
Interesting. This is one of the strong points of my Aleph J.
What's your power supply? Mine is a SMPS (pretty clean DC to start with) feeding a dual RCLC filter. The resulting DC rails look like a short circuit on my scope.
Well, maybe Mr Levinson should have paid ....
coincidentally , my dear AR2 is playing these days with Super Big Reds
OK , his intention was to acquire just drivers , but he found offer which wasn't for refusal
I'm teasing him that Altec is Poor Man's Tannoy is Poor Man's RCA
The Aleph J definitely takes an hour to reach a better operating temperature, and better sound. The 1.9A bias should have been confirmed after more than an hour of bench burn-in.
The amp will also improve significantly during the first 20 hours of playing time. I have developed the habit of leaving my new builds on overnight before doing any serious listening. As mentioned earlier, my Aleph J is left on 24 hrs a day when it is in rotation.
The power supply plays a very significant role in the sound of your amp. I noticed that you have done a couple things – installed an IEC powerline filter at the AC entry point, and added some film caps on the output of your main capacitor bank. I am not convinced that the metal can IEC inlet filters are beneficial to high continuous current amps. You may find an improvement with a simple switched AC inlet, and possibly a ferrite clamp on the AC lines leading to your transformer primary. I use the ferrite clamps for peace of mind more than anything else, but they definitely don't choke the inlet current. Given the use of the large can capacitors, adding some high quality 1000 uF to 2200 uF electrolytics in parallel with those big cans can help significantly. If you want to try something really interesting, try locating those at the VPOS and VNEG inputs on your channel boards. Use a pair per board, between their respective power rails and ground. I like the Nichicon KW and KA series caps for this application. Or try some 70 uF, 250V motor run caps instead. Just for fun
The amp will also improve significantly during the first 20 hours of playing time. I have developed the habit of leaving my new builds on overnight before doing any serious listening. As mentioned earlier, my Aleph J is left on 24 hrs a day when it is in rotation.
The power supply plays a very significant role in the sound of your amp. I noticed that you have done a couple things – installed an IEC powerline filter at the AC entry point, and added some film caps on the output of your main capacitor bank. I am not convinced that the metal can IEC inlet filters are beneficial to high continuous current amps. You may find an improvement with a simple switched AC inlet, and possibly a ferrite clamp on the AC lines leading to your transformer primary. I use the ferrite clamps for peace of mind more than anything else, but they definitely don't choke the inlet current. Given the use of the large can capacitors, adding some high quality 1000 uF to 2200 uF electrolytics in parallel with those big cans can help significantly. If you want to try something really interesting, try locating those at the VPOS and VNEG inputs on your channel boards. Use a pair per board, between their respective power rails and ground. I like the Nichicon KW and KA series caps for this application. Or try some 70 uF, 250V motor run caps instead. Just for fun