Well, I've gone and built an external power supply for the amp and I'm going to try that and see if I can get rid of the hum,
Here are some photos. This is just an experimental setup. If I like it and it works I'll transfer the innards to a Modushop chassis from the diyaudio store.
Here are some photos. This is just an experimental setup. If I like it and it works I'll transfer the innards to a Modushop chassis from the diyaudio store.
Attachments
It's the AN-6224 traffo with the inrush limiter giving me a +/-32VDC supply per rail. I'm using a 5 pin XLR to bring power to the main chassis. Earthing is through a bridge rectifier and thermistor arrangement. Live and neutral lines are both fused with a 6amp slowblow fuse.
The 5 pins are carrying +/-32VDC and earth for the amp pcb's and also the supply +/- for the front panel LEDs on the main chassis. Gotta have the blue light shining!
The 5 pins are carrying +/-32VDC and earth for the amp pcb's and also the supply +/- for the front panel LEDs on the main chassis. Gotta have the blue light shining!
Last edited:
Nice one!
Where did you put your second transformer, I thought you had two?
You need to carry PE to the amp's chassis as well in addition to circuit ground and the rail voltages.
I would use a Neutrik SpeakOn with 4 thick wires as an umbilical and eliminate the LED power, as it is enough if the PSU lights after powering on the system. But there is a bigger 8x SpeakOn as well should you really need more than 4 wires...
But I wouldn't use an XLR for this.
Edit: I just saw Zen Mod already shared the same idea. SpeakOn can do up to 8mm2 wire (8 AWG) which is more than enough in this case. PowerCon is only 3pins.
Where did you put your second transformer, I thought you had two?
You need to carry PE to the amp's chassis as well in addition to circuit ground and the rail voltages.
I would use a Neutrik SpeakOn with 4 thick wires as an umbilical and eliminate the LED power, as it is enough if the PSU lights after powering on the system. But there is a bigger 8x SpeakOn as well should you really need more than 4 wires...
But I wouldn't use an XLR for this.
Edit: I just saw Zen Mod already shared the same idea. SpeakOn can do up to 8mm2 wire (8 AWG) which is more than enough in this case. PowerCon is only 3pins.
Last edited:
Speakon Connectors arrived today and I built up a 4 core cable for the power connection from the PSU to the AMP. Thanks for the suggestion Zen Mod and Starcat. 3 cores for the +/-32V and PSU ground and a separate core for the main plant earth. I used 4 cores of 14AWG copper cable and installed a ferrite ring also. The cable is 5 feet long which should be okay.
Attachments
Very nice!
For simplicity I am using directly a speakOn 13AWG 4-wire cable, something like this. Goes very quickly.
just for the giggles - I hope you still have some proper capacitance in amp case
there must be local C bank, for proper results
observe umbilical as R in CRC
Dear Friends here's a quick update on things.
I finished the remote PSU for the amp and re-biased the amp last night. Success! Total silence at the amp from the PSU. I mean with my ear right up at the speaker - zero hum or any noise. Quietest amp I've ever built. Even my F5 had a little hum at the speaker, but nothing with this.
I have implemented a DC blocker for the mains feed to the PSU and I've also installed a filtered IEC connector. Both additions seem to have eliminated the noise on the mains.
If you look at the photos attached you can see the DC blocker just behind and to the left of the remote PSU.
With regards to capacitance in the PSU I have 120,000 uF of capacitance in the filter bank and with regards to umbilical, it is sized for my physical requirements. The amplifier is about 4 feet away from the PSU. It's just the physical reality.
Ultimately, I decided to hard wire the PSU to the amp using cable glands as every single Speakon chassis connector I tried failed their continuity checks. (I bought 10 of them, and every single one was faulty... who knew!)
As for the sound of the amplifier... It is truly remarkable! It's taken me 4 months to build and troubleshoot this amp, 4 completely different PSU implementations were tried until I got to a configuration that worked, and it was worth every moment of that time. What a sound!!!!
I finished the remote PSU for the amp and re-biased the amp last night. Success! Total silence at the amp from the PSU. I mean with my ear right up at the speaker - zero hum or any noise. Quietest amp I've ever built. Even my F5 had a little hum at the speaker, but nothing with this.
I have implemented a DC blocker for the mains feed to the PSU and I've also installed a filtered IEC connector. Both additions seem to have eliminated the noise on the mains.
If you look at the photos attached you can see the DC blocker just behind and to the left of the remote PSU.
With regards to capacitance in the PSU I have 120,000 uF of capacitance in the filter bank and with regards to umbilical, it is sized for my physical requirements. The amplifier is about 4 feet away from the PSU. It's just the physical reality.
Ultimately, I decided to hard wire the PSU to the amp using cable glands as every single Speakon chassis connector I tried failed their continuity checks. (I bought 10 of them, and every single one was faulty... who knew!)
As for the sound of the amplifier... It is truly remarkable! It's taken me 4 months to build and troubleshoot this amp, 4 completely different PSU implementations were tried until I got to a configuration that worked, and it was worth every moment of that time. What a sound!!!!
Attachments
And just for info, I have included the main earth and the PSU earth to the amplifier chassis, and yes, I got the Blue LEDs working on the main amp. Gotta have the blue lights!!! Papa Pass would be happy.
As for the Preamp, I'm using the Bride of Son of Zen. It sounds amazing!
As for the Preamp, I'm using the Bride of Son of Zen. It sounds amazing!
Attachments
Can you please share how/what exactly you tested? I too find it very odd for all your speakon connectors to be defective.