Your power supply is not setup properly. Please refer to this youtube guide that I made of another member.
You must always, always, always confirm your supply voltages before you connect anything to your amplifier.
The schematic and the build guide will references these voltages as well.
Oh my, I was looking so hard at the board components I completely missed the power supply was connected 😱 Yeah, I don't think you'll get far in testing with it connected like that (its shouldn't have done any damage if R109 was at max resistance) , you need to establish the dual rails - a positive +30V rail, a "0V" (GND) and a negative -30V rail. As Daniel picture and Stuarts video show. Best of luck.
Ok guys, I understand what you are saying. I'm not quite sure how to accomplish it with my power supply. Can I get +30 V out of one channel and -30 V out of channel 2 by putting the channels in parallel? To get my 0 Volts do I physically have to connect the negative (black) output on channel 1 and the positive (red) output on channel 2 and run that to the PSU ground terminal on the pcb?
I appreciate the help. I've only had that bench power supply since the beginning of the year.
John
I appreciate the help. I've only had that bench power supply since the beginning of the year.
John
Yes, but this is a series connection, not parallel.
Check the power supply manual, let us know if you need a hand
Quick rough example. Your two channels get connected in series.
Why doesn't it fit? Transistors closer together? Or it will not fit the on the heatsink?
Could the transistors be connected to the PCB through short wires? Or is that a no-go?
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Yes, transistors are closer together on EF3-5. Probably not a good idea to flywire the outputs on this.
Hello @Gianluca thank you for your reply, What is the difference between these two Dissipante 5U chassis?
https://modushop.biz/site/index.php?route=product/product&product_id=235
and
https://modushop.biz/site/index.php?route=product/product&path=242&product_id=784
Do wither come with a screen printed rear panel like the DIYAUDIO store version of your 5U chassis (see here: https://diyaudiostore.com/products/2025-deluxe-chassis-5u)?
@All are most people choosing this 5U chassis over a 4U chassis for the EF3-4 stereo configuration?
Differences are noted in the specs.
You likely would not prefer the diyAudio deluxe chassis, because it already has the UMS heatsink pattern included, and that pattern does not match what you need for (most) Wolverine builds.
No. However, the Deluxe version does have pre-cut holes for a PEM, binding posts, and inputs.
With that said, @Gianluca can likely make one to your exact requirements. My many experiences working with them have been incredible. I usually just chat with G in using the function on their website and then confirm a summary via e-mail to ensure we got it all nailed down. If I don't take the time to summarize, I inevitably forget a critical detail.
FWIW - I like space to work and cooler heatsinks ... so I typically go with the biggest chassis I have room to use / have budget to include. Plus, with very rare exception, my chassis get used for multiple projects, so it's nice to have a few larger ones. YMMV.
Ok, checked the UNI T power supply manual. In series mode CH1 is the positive output and CH2 is negative just as you have marked above. Voltage and current can only be adjusted in CH1, and the CH2 settings will follow those of CH1.
The series voltage total value is twice as much as CH1, and the current total value equals that of CH1.
Thanks,
John
Ok Stuart. Thanks for the advice. I did watch your YouTube video on the subject.
John
You'll have to confirm with other members as I use a Variac and not a bench supply, but i think you don't want to use the "series mode" and leave it in dual channel. I think in series mode the unit might internally connect to make one channel only and you won't get the 0V return that you need as I show in the drawing, as those other terminals become disconnected. The whole point of having a dual rail supply is having the "center" or "mid" point 0V as the return, and one channel is positive, and one channel is negative relative, to that midpoint.
You have to adjust the voltage on each rail individually (I think its okay if they are only 0.5V apart at a time)
I'm not sure on this though and it may work fine, but you can see in Stuarts video he is using two completely separate supplies to make the dual rail. They cannot be put into "series" mode because they are physically isolated from each other. So he's running two or "dual" channels.
You have to adjust the voltage on each rail individually (I think its okay if they are only 0.5V apart at a time)
I'm not sure on this though and it may work fine, but you can see in Stuarts video he is using two completely separate supplies to make the dual rail. They cannot be put into "series" mode because they are physically isolated from each other. So he's running two or "dual" channels.
I had two supplies in series so I could double the voltage as well to +64v 0 -64v. If you look closely you will see some bridging jumpers connecting the appropriate channels.
Looking at the UNI-T UDP3303A manual I think its best to treat them as to separate supplies as @Mainframe said. Then just wire them as @danieljw suggested.
I do have a feeling that series mode may work as it probable just connects the negative of the first supply to the positive of the second supply internally.
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I hooked it up as you have it drawn, but not connected to the amp board (as suggested by Stuart). I'm getting +30 V and -30 V to 0 V. You can't adjust the two channels independently. Channel 1 sets the voltage for both channels. The voltage is twice what channel 1 is set for (60 V across plus and minus). Current is the same in both channels, and is again controlled by the current set in Channel 1.
This seems correct to me given what you, Stuart and Daniel have taught me.
I'm not in any rush. UNI T has excellent customer service in the US. I can call them Monday to confirm that there are no other internal connections when in series mode.
John
Dual "tracking" power supplies do what you described in tracking mode. It doesn't hurt to check with UNI-T. I think you are ok to test the amplifier though.
My suggestion is start at 0V and slowly wind the voltage up on Ch1. Both channels should track. At about 3V you should see approximately 26 mA with no output stage bias.
If that happens continue up to 30V and check per build guide.
Hope this helps
-Dan
My suggestion is start at 0V and slowly wind the voltage up on Ch1. Both channels should track. At about 3V you should see approximately 26 mA with no output stage bias.
If that happens continue up to 30V and check per build guide.
Hope this helps
-Dan
Hi John,
I also want to mention, after you check things with +30Vdc / -30Vdc please lower the bias down before you use your full intended power supply voltage.
- Dan
I also want to mention, after you check things with +30Vdc / -30Vdc please lower the bias down before you use your full intended power supply voltage.
- Dan
Yes Dan, thanks for all the input. As a test I wired the power supply as you indicated, but did not attach it to the amp board. I measured voltage on both legs in series mode and with the two channels operating independently. The results were exactly the same: plus or minus 30 V to the 0 volt line. The only difference appears to be that you can set the voltage and current on channel 1 and 2 independently when not in series mode.
I'm still going to call UNI T. I want insure I understand how over voltage and over current protection work under series, parallel and independent channel operation as well as the internal connections made when operating in different modes.
Yes, per section 17.1 of the Build Guide adjust R109 to maximum resistance when done taking measurements.
John
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