Caps in parallel on each rail. -ve to GND on positive side and +ve to GND on negative rail. You could do something like this and use lots of smaller less expensive caps to get lower ESR for more bass authority. ESR effective is divided by number of caps.
68PCS 75V/220UF Power Supply Board DIY Kit for HiFi Audio Amplifier PSU Module 175864069323 | eBay
68PCS 75V/220UF Power Supply Board DIY Kit for HiFi Audio Amplifier PSU Module 175864069323 | eBay
Ah, it makes sense now. Thank you X. I was actually thinking of your low ESR cap banks for Class D amps that you posted in other threads - just not sure of the dual rail implementation. So, this can work for Class A too. I might just try this later.
Hi X. I'm busy collecting parts for various builds again now that my basement is finished and my workshop is up and running. Thinking about using SLB single rail boards to do a Zen Mod Singing Bush build vs. a CLC for each mono block. Considering I have most of the parts for the SLB's already it would be way more economical. Each Singing Bush channel needs +60v on the THF-51 SIT. The bias current is around 2.3A. Here is ZM's PSU advice:
"For all iterations , target positive rail is 60Vdc , plain logic and experience sez that's 48Vac secondary Donut
Schade (Full Mos) is having Iq in range of 3A/ch. ......... say 300VA Donut as minimum per channel
THF51/2SK180/2SK182 - having Iq in range of 2A2 , say 250VA Donut as minimum per channel
caps - 75Vdc rated, as minimum
cap bank for one channel - CRC fashion , 20mF-0R1/3W-20mF , as absolute minimum ; 30mF-0R1/3W-30mF is better ; more , the merrier"
So with these variables is a +60v supply possible with the SLB? I would plan on using 80v caps. What voltage are the BD139/140 seeing in the circuit? Any other components that wouldn't necessarily play nice with the +60v?
"For all iterations , target positive rail is 60Vdc , plain logic and experience sez that's 48Vac secondary Donut
Schade (Full Mos) is having Iq in range of 3A/ch. ......... say 300VA Donut as minimum per channel
THF51/2SK180/2SK182 - having Iq in range of 2A2 , say 250VA Donut as minimum per channel
caps - 75Vdc rated, as minimum
cap bank for one channel - CRC fashion , 20mF-0R1/3W-20mF , as absolute minimum ; 30mF-0R1/3W-30mF is better ; more , the merrier"
So with these variables is a +60v supply possible with the SLB? I would plan on using 80v caps. What voltage are the BD139/140 seeing in the circuit? Any other components that wouldn't necessarily play nice with the +60v?
Hi Jwjarch,
If we assume that a linear trafo will sag about 4v from a no-load condition and that the SLB drops 3v, we add 7v to the nominal 60v required. That is 67v and divide by 1.41 to get 47.5v ac. So ZM's advice of 48v, even though it was not for the SLB, seems spot on. All the actives can handle the 60v - just make sure you upgrade the caps. 10,000uF 80v caps might be sufficient. Look for ones with a high ripple current rating of circa 2x your current. So for 2.2A, look for 4.5 to 5A ripple current rating at 120Hz. I hope that helps. 250VA to 300VA rating seems about right.
If we assume that a linear trafo will sag about 4v from a no-load condition and that the SLB drops 3v, we add 7v to the nominal 60v required. That is 67v and divide by 1.41 to get 47.5v ac. So ZM's advice of 48v, even though it was not for the SLB, seems spot on. All the actives can handle the 60v - just make sure you upgrade the caps. 10,000uF 80v caps might be sufficient. Look for ones with a high ripple current rating of circa 2x your current. So for 2.2A, look for 4.5 to 5A ripple current rating at 120Hz. I hope that helps. 250VA to 300VA rating seems about right.
That all sounds good X. Just put in my order for two single rail SLB boards. What is the max diameter for the bulk caps that will fit on the boards?
Hi Jwjarch,
I currently have CDE 15,000uF 50v SLPX caps in there that are nominal 35mm dia x 10mm lead spacing.
https://www.mouser.com/ProductDetai...EpiMZZMukHu%2BjC5l7Ycd/H5%2BMxIQfeDabICBya9g=
You can look for other 35mm x 10mm caps for your application.
I currently have CDE 15,000uF 50v SLPX caps in there that are nominal 35mm dia x 10mm lead spacing.
https://www.mouser.com/ProductDetai...EpiMZZMukHu%2BjC5l7Ycd/H5%2BMxIQfeDabICBya9g=
You can look for other 35mm x 10mm caps for your application.
So I finally soldered up a dual rail SLB and powered it up tonight. I’m using an Antek 4222 transformer along with a Babelfish J2 board. Only one channel for testing right now. I’m getting 28.5V + and - with the single channel powered up. I believe I’m at about 1.5a bias at the moment. Everything seems fine, however, I’m not able to dial in any change in voltage with the pots on the SLB. I’ll have to go back and check my resistor values. I also have the LED on the negative rail in backwards but that shouldn’t affect anything, correct? Anything else I should be looking out for?
The amount of variation that the pots can change is very little. Maybe a few volts. It's not like one of the other cap Mx designs where you can basically dial in 6 or 7v or difference.
Are you not getting any change at all or very little?
Basically zero change. Maybe .1 or .2V. During my first test I hooked up a dummy load across each rail to ground, 16ohms to be exact. Could this have done any damage vs hooking up the dummy load across the positive and negative rails?
16ohm load should be fine. I the cap Mx reducing the ripple? What is the voltage drop?
Should be circa 100mV rms ripple in and 1mV ripple out.
Should be circa 100mV rms ripple in and 1mV ripple out.
Hi Jwjarch,
Congrats on your new SLB! The trimpots have very little adjustment on the output voltage, less than 1v. Also, flip the LED so they are both working. 🙂
Congrats on your new SLB! The trimpots have very little adjustment on the output voltage, less than 1v. Also, flip the LED so they are both working. 🙂
Thanks Vunce! Can’t believe how long I’ve had these sitting in my parts stash and haven’t built them up.
It seems to be filtering the ripple X. I’m not getting a single mv AC on my Fluke meter, unless there’s a better way to test. I have a cheap eBay scope I could put on there but I haven’t tried it yet. Not sure if it’s good enough to measure what I want to measure and not blow it up in the process. I’m no EE.
It seems to be filtering the ripple X. I’m not getting a single mv AC on my Fluke meter, unless there’s a better way to test. I have a cheap eBay scope I could put on there but I haven’t tried it yet. Not sure if it’s good enough to measure what I want to measure and not blow it up in the process. I’m no EE.
SLB is doing its thing with Babelfish J2 boards. I originally planned for dual mono but the single board seems to be working well so I’ll probably hold off on the second board for now. Best part? Both LEDs are working now. 
Thanks for the great power supply design everyone!
Thanks for the great power supply design everyone!
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Interesting! I am planning to do a dual mono SissySit anplifier. What makes you say one SLB is fine? My reason for dual mono is lower ground loop noise, as I have 110db efficient horn compression drivers.
And may I ask, how hot is that base plate now that you have screwed the fets to it?
And may I ask, how hot is that base plate now that you have screwed the fets to it?
Nice work Jwjarch! Glad it’s working out with just one. Dual mono will reduce ground loop noise, if it was a problem. If not then that’s cool. You will also get better stereo imaging with two.
@RobinDW, those are actually BJT pass transistors. You can calculate the dissipation if you know the current. For a stereo 25w Pass amp the bias is typically 1.25A per channel. So 2.5A x 3v drop. Or 7.5W or 15W for both. Not insignificant but I don’t think it’s too hot.
@RobinDW, those are actually BJT pass transistors. You can calculate the dissipation if you know the current. For a stereo 25w Pass amp the bias is typically 1.25A per channel. So 2.5A x 3v drop. Or 7.5W or 15W for both. Not insignificant but I don’t think it’s too hot.
Thanks X! Pretty easy build when all is said and done. A bit of info, I used TTA1943 and TTC5200 Toshiba fets. Got a great deal on a quantity order from LCSC. I also used sockets on the LT4320’s just in case. 😉
The jury is still out on the ground loop noise since I haven’t hooked these up to high efficiency speakers yet. Will try that soon. On my workshop speakers I can’t hear any hum or noise. In my listening room I have an open baffle setup with Lii-Audio Crystal 10’s on top and GRS-15’s on the bottom. With the crossover I think they’re in the 95-96db range for sensitivity. I would think you would need to go dual mono no matter what on super sensitive horn compression drivers.
Regarding imaging I still need to do an A/B with the F7 clone but what I’m hearing so far is nothing less than amazing. I looked up a recommended album for stereo imaging, Roger Water’s, Amused to Death. The first track has a soundstage I have never heard on stereo speakers before. And all this from my little PS95-8 mini-k’s fed by a cheap Bluetooth receiver streaming Amazon Music. Even without dual mono I think this amp will outperform the F7 clone in that regard, which is dual mono with CapMx PSU’s. It will be interesting to see what the BabelJ2 with SLB can do with a preamp, CD/vinyl source, and really good speakers.
And at the end of the day I can always build up the second SLB when I have time. 😀
The jury is still out on the ground loop noise since I haven’t hooked these up to high efficiency speakers yet. Will try that soon. On my workshop speakers I can’t hear any hum or noise. In my listening room I have an open baffle setup with Lii-Audio Crystal 10’s on top and GRS-15’s on the bottom. With the crossover I think they’re in the 95-96db range for sensitivity. I would think you would need to go dual mono no matter what on super sensitive horn compression drivers.
Regarding imaging I still need to do an A/B with the F7 clone but what I’m hearing so far is nothing less than amazing. I looked up a recommended album for stereo imaging, Roger Water’s, Amused to Death. The first track has a soundstage I have never heard on stereo speakers before. And all this from my little PS95-8 mini-k’s fed by a cheap Bluetooth receiver streaming Amazon Music. Even without dual mono I think this amp will outperform the F7 clone in that regard, which is dual mono with CapMx PSU’s. It will be interesting to see what the BabelJ2 with SLB can do with a preamp, CD/vinyl source, and really good speakers.
And at the end of the day I can always build up the second SLB when I have time. 😀
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Update: I was listening to the BabelJ2 with single SLB PSU tonight. First, there is virtually no noise or ground loop hum on my setup. I have to press my ear to the speaker cone to hear any noise. So not completely silent but pretty darn close with 96db speakers.
Using the Chesky Vol 2 Jazz test track CD, I ran through the usual test tracks I like to use. Everything sounds phenomenal in terms of definition, detail, impact, etc., except the image. Compared to the F7 I am not getting the clearly defined right to left panning of the image on tracks 60-70. So tonight I immediately started to solder up my second SLB board. 😉
So much for me getting away with the single SLB. Hoping to report back that the imaging I am used to with the F7 will return by going dual mono.
Using the Chesky Vol 2 Jazz test track CD, I ran through the usual test tracks I like to use. Everything sounds phenomenal in terms of definition, detail, impact, etc., except the image. Compared to the F7 I am not getting the clearly defined right to left panning of the image on tracks 60-70. So tonight I immediately started to solder up my second SLB board. 😉
So much for me getting away with the single SLB. Hoping to report back that the imaging I am used to with the F7 will return by going dual mono.