There are some very impressive projects in this thread. I have contemplated such a task for sometime acquiring a few too many boards and not enough chassis (yes, plural as in "deer"). There has been a discussion on the last two pages about how many cables to run in one umbilical.
My intention is to combine the two power cables for each channel with the power for the DC protection board.
Looking at some of the early schematics, there are roughly 8-9 separate conductors depending upon the grounding scheme between the two chassis.
Is there an issue with running all of this together in one rather thick cable related to electrical interference?
I see options of using 1 thick cable with both channels and the DC board power, combining the amplifier channels and having a separate DC power cable or separate cables (and jacks) for each of the power sources. I do realize one much consider the cost/benefit ratio.
My intention is to combine the two power cables for each channel with the power for the DC protection board.
Looking at some of the early schematics, there are roughly 8-9 separate conductors depending upon the grounding scheme between the two chassis.
Is there an issue with running all of this together in one rather thick cable related to electrical interference?
I see options of using 1 thick cable with both channels and the DC board power, combining the amplifier channels and having a separate DC power cable or separate cables (and jacks) for each of the power sources. I do realize one much consider the cost/benefit ratio.
Thank you, @ItsAllInMyHead for driving this thread. I'm doing the same thing, so this thread is super helpful. Question: It appears folks are using Galaxy or Slimline chassis, so are you doing anything to get electrical continuity between panels (for safety earth)?
^ That's quite nice of you to say, and it's appreciated. I'm glad some of my posts/questions and the answers from the actual experts helped. However, I need to acknowledge that others got it going. I just ask a lot of questions. Please continue the trend. I learn from every post.
On to your question. All of mine have had good continuity between all panels as-delivered/as-assembled (I checked). I didn't have to go to any extra measures like removing paint / anodization or adding/changing fasteners, but I've seen it done. A little scraping here and there is probably not a bad thing to sleep a little better.
Edited to add - As assembled. The panels don't have great continuity as-delivered.
On to your question. All of mine have had good continuity between all panels as-delivered/as-assembled (I checked). I didn't have to go to any extra measures like removing paint / anodization or adding/changing fasteners, but I've seen it done. A little scraping here and there is probably not a bad thing to sleep a little better.
Edited to add - As assembled. The panels don't have great continuity as-delivered.
After reading this thread and numerous others looking for info on how to build an outboard PSU for the Class-A Pass +/-24V amps (F4, F5, F6, and Aleph-J), here's what I've come up with. So far it's just the PSU, but I've built and tested some of the amp boards and will next finish them in monoblock chassis with umbilicals to the PSU. The PSU chassis is a Modushop 3U Galaxy (GX385 330 x 350 mm). The transformers are Antek AS-3218 (300VA 18V). The PSU boards are ThatcherDIYAudio Monoblock PSU kits (Class A CRCRC dual rail) with GBPC3502 bridge rectifiers and 18,000uF 35V caps. The umbilical connectors are Neutrik 4-conductor speakON (+24V, 0V, -24V, and chassis ground). All of the hookup wiring is 16 AWG stranded. Any suggested improvements or critiques are very much appreciated, but mostly -- to the extent that I've maybe done this mostly right -- I'm hoping this helps the next person, since this seems to be something that lots of people want to do.
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^ Overall, I think it's fantastic. 
Very nice!
These are not all necessarily questions for you directly, but perhaps for the group as a whole. They're phrased as questions b/c I truly am not sure...
1 - Are soft starts in place? If they are not in place, are they advised?
2 - Are the PSUs individually fused? If not, I believe that is advised, but that's still probably best answered by someone a bit smarter than I.
3- Do you intend to use any sort of ground lifts or are they in place? I tried to zoom in on the boards and surrounding area, but I can't see with this screen at the moment. If they're not in place, but you plan to implement them, how will you implement?
4 - It's not directly related to the PSU you've built, but have you decided on your plans for any caps within the separate amp chassis?
Awesome stuff!
Edited for (hopefully) better clarity.
Very nice!These are not all necessarily questions for you directly, but perhaps for the group as a whole. They're phrased as questions b/c I truly am not sure...
1 - Are soft starts in place? If they are not in place, are they advised?
2 - Are the PSUs individually fused? If not, I believe that is advised, but that's still probably best answered by someone a bit smarter than I.
3- Do you intend to use any sort of ground lifts or are they in place? I tried to zoom in on the boards and surrounding area, but I can't see with this screen at the moment. If they're not in place, but you plan to implement them, how will you implement?
4 - It's not directly related to the PSU you've built, but have you decided on your plans for any caps within the separate amp chassis?
Awesome stuff!
Edited for (hopefully) better clarity.
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That's a nice looking and well designed external PSU for sure! Certainly not claiming to be smarter than anyone else (especially in this domain), but I would echo the sentiments above.
It's hard to see much detail because your images are somewhat small, so I don't know if you included any of this or not. It's a good idea to have a thermistor inline with each transformer primary for a little bit of a soft start. Fusing each transformer primary (separately) is also a good idea. It looks like there is a fuse built into the AC power entry on the rear, though. It's likely safer to use a smaller fuse on each transformer. I would keep the ground lifts out of the PSU and put them directly in the amps - use thermistors here as well. Group all of the signal and PSU grounds together inside each amp, then run them through a thermistor before hitting the umbilical ground point to the outboard PSU. Adding additional local caps in the amp chassis creates a CRC, using the umbilical as the resistor.
These are all easy tweaks to an already great external PSU box. I used Neutrik connectors for mine as well, along with some heavy 13g cable that I got from PartsExpress.
Nice build!
It's hard to see much detail because your images are somewhat small, so I don't know if you included any of this or not. It's a good idea to have a thermistor inline with each transformer primary for a little bit of a soft start. Fusing each transformer primary (separately) is also a good idea. It looks like there is a fuse built into the AC power entry on the rear, though. It's likely safer to use a smaller fuse on each transformer. I would keep the ground lifts out of the PSU and put them directly in the amps - use thermistors here as well. Group all of the signal and PSU grounds together inside each amp, then run them through a thermistor before hitting the umbilical ground point to the outboard PSU. Adding additional local caps in the amp chassis creates a CRC, using the umbilical as the resistor.
These are all easy tweaks to an already great external PSU box. I used Neutrik connectors for mine as well, along with some heavy 13g cable that I got from PartsExpress.
Nice build!
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I have a power amp with a 1000VA transformer and its bigger brother with a 2000VA transformer .
Neither of them have a soft start . However , I found that connecting a small cap between the 2 hots of the power switch
really helps because it reduces arcing of the switch contacts.
From what I understand 10nF value is required in this application - double check this but I think this cap needs to have a X2 AC rating .
.
Rdb64 ,
I'm certainly no expert , but a few comments
I'm certainly no expert , but a few comments
- From the photos , I don't see where hydro earth is connected to the case - hydro earth must have its own dedicated ground machine screw
- Its good you have both the hot and neutral switched , but I don't see the hot and neutral wiring to the transformers.
- Consider building your own Fo Felix EMI filter - which was designed specifically for audio
- Recommend adding a power switch cap as discussed in post #248 above .
- The wire gauge used for the DC wiring looks a bit light - unless you were intentionally using this to create an impedance .
Wow, thank you all for the thoughtful comments. Clarifications:
Soft start: There's a thermistor (CL-60) on each transformer primary live and neutral (so 4 CL-60s total). Looks like I'm fine with that.
Fuses: There are fuses in the AC power entry: 3A on live and 10A on neutral. Sounds like it would be better to have separate fusing at each transformer with a lower current rating, maybe 2A instead of 3A. Makes sense.
Ground lift: Each PSU filter board has a thermistor connecting power ground to chassis. It sounds like it would be better to move the ground lift to each of the amp chassis. Not sure why that is.
Caps in the amp chassis: I'm planning to use a pair 18,000 uF caps in each. That's the same capacitance as is used in each C stage of the PSU. Even after searching through these forums and asked the question, I have yet to find much information on how to size the capacitance in the amp chassis.
Earth ground: Earth ground from the AC power entry is connected to the chassis with a tooth nut on the bottom side of the base plate (so it can't be seen in the photos). Sounds like I need to add some tubing to protect that wire from the edges of the base plate.
Wiring: Sounds like the 16 AWG that I used is a bit light, and I'd be better with 14 or maybe 13.
Thanks again.
Soft start: There's a thermistor (CL-60) on each transformer primary live and neutral (so 4 CL-60s total). Looks like I'm fine with that.
Fuses: There are fuses in the AC power entry: 3A on live and 10A on neutral. Sounds like it would be better to have separate fusing at each transformer with a lower current rating, maybe 2A instead of 3A. Makes sense.
Ground lift: Each PSU filter board has a thermistor connecting power ground to chassis. It sounds like it would be better to move the ground lift to each of the amp chassis. Not sure why that is.
Caps in the amp chassis: I'm planning to use a pair 18,000 uF caps in each. That's the same capacitance as is used in each C stage of the PSU. Even after searching through these forums and asked the question, I have yet to find much information on how to size the capacitance in the amp chassis.
Earth ground: Earth ground from the AC power entry is connected to the chassis with a tooth nut on the bottom side of the base plate (so it can't be seen in the photos). Sounds like I need to add some tubing to protect that wire from the edges of the base plate.
Wiring: Sounds like the 16 AWG that I used is a bit light, and I'd be better with 14 or maybe 13.
Thanks again.
Nice build!!!
I saw the CL-60/AC Cap board tucked in on the faceplate. Did you drill and tap that? It's a clever solution, well done!
My only comment is regarding adding 1 fuse per donut. It's a matter of 2 drill holes on the back plate for some panel mount fuse holders. Then a little wiring.
Your PSU is CCRCRC, and 18kuF in that config should be A-OK. Will you be adding a cap bank in the amp chassis? Do you have/need a board for that?
I don't know specs on your connectors. I trust they're up for a rating that can handle the current and voltage you're going for.
I saw the CL-60/AC Cap board tucked in on the faceplate. Did you drill and tap that? It's a clever solution, well done!
My only comment is regarding adding 1 fuse per donut. It's a matter of 2 drill holes on the back plate for some panel mount fuse holders. Then a little wiring.
Your PSU is CCRCRC, and 18kuF in that config should be A-OK. Will you be adding a cap bank in the amp chassis? Do you have/need a board for that?
I don't know specs on your connectors. I trust they're up for a rating that can handle the current and voltage you're going for.
I think 16 AWG wiring is OK for power supply and high level audio. For low level audio (i.e. input cabling) I use 24 AWG twisted pair or small coax. Any drop in the umbilical will simply form another "R" in the filtering scheme. I actually label that "r" so it would look something like CCRCrC... Should work great..
Thank you, @rhthatcher, and thank you for those PSU boards. They're excellent.
Yup, drilled and tapped on the faceplate to mount your soft-start boards.
For the caps in the amp chassis, I was planning to use chassis mount with screw terminals. Then just point-to-point hookup wire, so no PCB. I welcome other suggestions.
The connectors are quick-connect 14-16 AWG crimp connectors (DNF14-250FIB). The one thing I don't like about them is the insulation makes it impossible to see the crimp. I pull pretty hard on them to check, but I'd rather be able to see. Was thinking of using non-insulated and then shrink wrap after.
Yup, drilled and tapped on the faceplate to mount your soft-start boards.
For the caps in the amp chassis, I was planning to use chassis mount with screw terminals. Then just point-to-point hookup wire, so no PCB. I welcome other suggestions.
The connectors are quick-connect 14-16 AWG crimp connectors (DNF14-250FIB). The one thing I don't like about them is the insulation makes it impossible to see the crimp. I pull pretty hard on them to check, but I'd rather be able to see. Was thinking of using non-insulated and then shrink wrap after.
I've been collecting parts for the separate power supply and thought Neutrik 3 Pin connectors were being used. Am I mis-taken?
^ Heavily discussed... There are also many different types of Neutrik jacks.
Some factors may include, but are not limited to... and in no particular order.
1 - Is the part recommended by the manufacturer for the task at hand?
2 - Connection style for wire to "jack". Some can be fiddly, IMO. Some people will only do a soldered connection. Some like mechanical connections of various types.
3 - Available in gauge range needed?
4 - Ease of assembly / reliability of assembly when done properly. Failure modes if not done properly. Probability of not doing it properly? See also #2.
5 - Is it "keyed"?
6 - Could it be mistaken for something else commonly used in my (or others') systems? Chance of sticking wrong thing into wrong hole?
7- Mechanical stability of connection. Does it "lock"?
8 - Special tools recommended / required for assembly?
9 - Cost
10 - Mounting requirements / size / type of cut out / tools required for chassis?
11 - Longevity (contacts and mechanical). How often will it be connected / disconnected?
Some or none of those things may factor in along with many other things I may not have considered.
Some factors may include, but are not limited to... and in no particular order.
1 - Is the part recommended by the manufacturer for the task at hand?
2 - Connection style for wire to "jack". Some can be fiddly, IMO. Some people will only do a soldered connection. Some like mechanical connections of various types.
3 - Available in gauge range needed?
4 - Ease of assembly / reliability of assembly when done properly. Failure modes if not done properly. Probability of not doing it properly? See also #2.
5 - Is it "keyed"?
6 - Could it be mistaken for something else commonly used in my (or others') systems? Chance of sticking wrong thing into wrong hole?
7- Mechanical stability of connection. Does it "lock"?
8 - Special tools recommended / required for assembly?
9 - Cost
10 - Mounting requirements / size / type of cut out / tools required for chassis?
11 - Longevity (contacts and mechanical). How often will it be connected / disconnected?
Some or none of those things may factor in along with many other things I may not have considered.