All good, agreed 👍
Dummy place everything into your chassis and put up a pic and we can pitch ideas, from my experience keeping the transformers, and especially the rectifiers, away from the IPS boards gives a way lower noise floor. Transformers will couple a little 50-60hz into the input stage, but the rectifier diodes are the worst for spraying the noise floor with 120hz and harmonics. This noise does not come through the power rail wiring but is instead capacitively coupled by proximity. I like your idea of having the rectifiers above the transformer, so long as they are at the front of the chassis and the IPS boards are at the back. There will be no magnetic field issue with this so long as you don't inadvertently close a mechanical loop through the center of a transformer.
It's up to you how to proceed. You can either do a bench full power test or do the full power test later in chassis with all auxiliary's and speaker protects.
I like to set up (in your case, one of) the intended board power supply on the bench (that's including soft start and ground lift if applicable, but no speaker protect) and test the amplifier at final rail voltage with the heatsink oriented vertically, as it would in the final chassis, to get the bias correct with the right airflow over the heatsink. No need to put in a signal or music if your don't have the means to on the bench. Just gives me reassurance its ready for full rail voltage and is cooling sufficiently as the outputs do generate more heat with final rail voltage as opposed to 30V test rails.
EDIT - always use soft start (or Variac) for transformers larger than 400VA, even when setting up a bench supply. Otherwise you will just end up blowing through multiple Tx input, or output fuses as the caps charge up.
Ok, I'm currently re-reading the wiring document that talks about loop area. I built the chassis when I got it from ModuShop, and then tore it apart to mount the power boards. I'll just mock up one channel for placement. I was told I could use just one SS Board and Ground Lift for both channels, so that's all I've built. Let me know if there's a problem with this.
I used the Quasimodo jig to determine the snubbers for the PSUs. I need to mount to two film caps and the snubber resistors in each of the two psu's.
Then I'll set up a bench test. When you do this, do you utilize the PEM that you're using in the chassis to get mains voltage to the transformers? The PEM I'm using is identical to the one included in the diyaudio store back panel kit (I believe it's unfiltered).
I can provide a signal as my scope has a built in waveform generator. I'm going to build a dummy load with four 16 ohm 100 watt resistors mounted on heat sinks. I also have a preamp and DAC available with old speakers to play through on my bench.
I think I may need to order wire for the power supplies. I was thinking 14 AWG (2.5mm). Service at the wall is better than 120 V 15 A. Come to think of it I think this is the gauge wire Daniel used.....and you guys have 240 V 10 A service. I can't imagine I need heavier than 14 AWG though or can I get away with 16 AWG?
Thanks,
John
I used the Quasimodo jig to determine the snubbers for the PSUs. I need to mount to two film caps and the snubber resistors in each of the two psu's.
Then I'll set up a bench test. When you do this, do you utilize the PEM that you're using in the chassis to get mains voltage to the transformers? The PEM I'm using is identical to the one included in the diyaudio store back panel kit (I believe it's unfiltered).
I can provide a signal as my scope has a built in waveform generator. I'm going to build a dummy load with four 16 ohm 100 watt resistors mounted on heat sinks. I also have a preamp and DAC available with old speakers to play through on my bench.
I think I may need to order wire for the power supplies. I was thinking 14 AWG (2.5mm). Service at the wall is better than 120 V 15 A. Come to think of it I think this is the gauge wire Daniel used.....and you guys have 240 V 10 A service. I can't imagine I need heavier than 14 AWG though or can I get away with 16 AWG?
Thanks,
John
The one soft start is fine for both PSU's, but you ideally need 2x ground lifts if doing a full dual mono.
It is probably better to set up the boards for full power in the chassis if you haven't done this before, as you can correctly earth everything that way before applying any mains. You can use the mains entry module from the chassis and make sure all exposed mains terminals are protected correctly, and your PSU and SS boards are lifted off the chassis base with standoffs. A mains setup on bench is risky if you haven't done so before / built a few power amplifiers before.
16awg (1.5mm) is plenty for AC mains, DC rails and amp to speaker terminal wiring, 14awg (2.5mm) is starting to make life difficult for no gain IMO, unless doing something ridiculous like kW amp channels.
It is probably better to set up the boards for full power in the chassis if you haven't done this before, as you can correctly earth everything that way before applying any mains. You can use the mains entry module from the chassis and make sure all exposed mains terminals are protected correctly, and your PSU and SS boards are lifted off the chassis base with standoffs. A mains setup on bench is risky if you haven't done so before / built a few power amplifiers before.
16awg (1.5mm) is plenty for AC mains, DC rails and amp to speaker terminal wiring, 14awg (2.5mm) is starting to make life difficult for no gain IMO, unless doing something ridiculous like kW amp channels.
I would need a CAD drawing with the required holes to drill. After that it should be a breeze to produce one