Im also looking for a better TPA board, of what is currently available online whats the best option? I see that the Sylph D200 looks nice but it says 5-8 weeks shipping time! Thats slower than the slow boat from China lol.
This is maybee an answer on my Q? 🙂
https://www.audiosciencereview.com/...ifier-module-review.25295/page-9#post-1144174
https://www.audiosciencereview.com/...ifier-module-review.25295/page-9#post-1144174
I hope that this is the correct forum to post this, and I hope that someone can help.
I recently resurrected an old, dead amplifier (happened to be a GAS Son of Ampzilla) by saving the power supply, discarding all of the internal circuitry, and substituting a pair of 3e-Audio "480W x 1 Channel" TPA3255 modules. I have attached a rough schematic showing how I wired it all up. The modules are configured for single-ended operation, and the inputs are via RCA jacks. Note that the inputs are completely isolated from the chassis ground.
Everything works, except that both output channels hum from a ground loop. The hum occurs even when the inputs are shorted, though the amplitude is reduced. I even tried transformer-isolating the inputs, including configuring the transformers as single-ended to differential converters, and again the hum is reduced but never goes away. I'm at my wit's end on this problem, so if anyone can figure out what I did wrong, I'd appreciate help in correcting it. Thanks.
I recently resurrected an old, dead amplifier (happened to be a GAS Son of Ampzilla) by saving the power supply, discarding all of the internal circuitry, and substituting a pair of 3e-Audio "480W x 1 Channel" TPA3255 modules. I have attached a rough schematic showing how I wired it all up. The modules are configured for single-ended operation, and the inputs are via RCA jacks. Note that the inputs are completely isolated from the chassis ground.
Everything works, except that both output channels hum from a ground loop. The hum occurs even when the inputs are shorted, though the amplitude is reduced. I even tried transformer-isolating the inputs, including configuring the transformers as single-ended to differential converters, and again the hum is reduced but never goes away. I'm at my wit's end on this problem, so if anyone can figure out what I did wrong, I'd appreciate help in correcting it. Thanks.
Attachments
Just my random 2 cents here: If this is indeed parts from an old amp the PS caps could be degraded and not doing much to filter/smooth the ripple coming out of the rectifier. A class D amp has less PSRR compared to your typical class AB amp.
If there is any way to provide the required rail voltage to the amp modules (even if you cannot meet the power needs) you can replace the linear PS with the (other one), fire up the amp, and see if the hum remains. Since you do not draw any current becuase there is no load, the test PS only needs to provide the necessary rail voltage.
If it turns out the linear PS caps are band, you can replace them and while you are at it split the total capacitance into two banks with a 0.47R power resistor inbetween to create a CRC arrangement, which will provide a little bit of additional filtering compared to one larger cap.
If there is any way to provide the required rail voltage to the amp modules (even if you cannot meet the power needs) you can replace the linear PS with the (other one), fire up the amp, and see if the hum remains. Since you do not draw any current becuase there is no load, the test PS only needs to provide the necessary rail voltage.
If it turns out the linear PS caps are band, you can replace them and while you are at it split the total capacitance into two banks with a 0.47R power resistor inbetween to create a CRC arrangement, which will provide a little bit of additional filtering compared to one larger cap.
D
Deleted member 148505
Make sure that the DC power cables going to the modules are either perfectly in parallel or tightly twisted together. Also, a common mistake is to connect wrong XLR wiring pinout to the module.
You could see if it is EMI induced hum in the line level wiring by unplugging the input headers or connections and switching the input type to balanced. Also, did you leave the unused (cold?) input floating? You might get better noise performance when that is connected to ground at the input header when using single ended mode.
I tried wiring it in balanced mode through a Jensen isolation transformer (single-ended in, balanced out using the center tap), and it made no difference. I haven't tried it in balanced mode with inputs "open".
No, it's tied to AGND at the input RCA jack, and all three wires are braided nicely from the RCA jack to the pin jack on the board, to get at least a bit of RF shielding.
I would tie to AGND at the board, not at the chassis/jack. There is no need for the cold wire to run from the amp board to the chassis.
OK I spent the last hour partially disassembling the amp, to twist the DC wires and check all connections. Everything looked good.
As an experiment, I completely removed one of the modules and checked the other for hum. Dead silence in the active channel.
Reconnected the other module. Hum in both channels. Sounds like predominantly 120 Hz.
The cause is some weird interaction between the two modules. The only connection between them is through the power supply. I'm stumped.
As an experiment, I completely removed one of the modules and checked the other for hum. Dead silence in the active channel.
Reconnected the other module. Hum in both channels. Sounds like predominantly 120 Hz.
The cause is some weird interaction between the two modules. The only connection between them is through the power supply. I'm stumped.
D
Deleted member 148505
I'm starting to wonder if I need separate rectification and separate capacitance for the two channels. They'd still both be common-grounded to the secondary center tap, but the two positive lines would be separated by reverse-biased diodes. Opinions?
Apologies for quoting myself, but there is some new information. When I performed the test discussed above, I had connected the amp to a single-ended two-channel source. Performing the same test with both inputs shorted: dead silence.
EDIT: BTW, this is different behavior than I observed previously. In the past there was still some residual hum with the inputs shorted. So perhaps my disassembly/reassembly corrected a loose connection or something.