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building a TPA3255 260-2-29A, and need some guidance

You said you have noise when the MiniDSP is powered off though? Can you be super careful and work through this process?
  • Speakers connected to amp, amp powered on, no cables connected to amp
  • Speakers connected to amp, amp powered on, RCA cables connected to amp only, not the Flex
  • Speakers connected to amp, amp powered on, RCA cables connected to amp and Flex, Flex power cable not connected
  • Speakers connected to amp, amp powered on, RCA cables connected to amp and Flex, Flex power cable connected and powered on
  • Speakers connected to amp, amp powered on, RCA cables connected to amp and Flex, Flex power cable connected and powered on, USB cable connected to PC, PC powered on
I narrowed it down to cross talk, or some sort of noise between the two modules. Once I remove BOTH channels from one module, all is well. The moment I add the other module, noise starts to happen. I appreciate the assistance in this matter.
 
I narrowed it down to cross talk, or some sort of noise between the two modules. Once I remove BOTH channels from one module, all is well. The moment I add the other module, noise starts to happen. I appreciate the assistance in this matter.
So with two modules installed, do you have noise with no RCA cables connected?
 
Look at these 2 pics, now see what I mean? This is working for me
View attachment 377659
View attachment 377658


EDIT - to clarify when I said "this is working for me" all that means is this wiring configuration produces audio sound as expected. The BIG question (not yet answered) is "does going to these extra efforts make any audible difference / under what specific conditions? Having listened both ways (2 masters vs master+slave) I cannot hear any differences. I am purchasing some more instruments so that I can make the kind of measurements that ASR expects for these kinds of evaluations. Will let you know how that goes (over in "my" amp build thread).
sadly this didn't help. Does lowering the mains voltage to the amp boards help?
 
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sadly this didn't help
I do have some noise coming from the power supply transformer, would that induce any noise into the system and cause this?
 

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There is 0 noise with NO RCAS connected (amp on, speaker wires plugged in)
Great! so, can you work through the rest of the list from post #41 and see at what pint the noise starts?
 
I do have some noise coming from the power supply transformer, would that induce any noise into the system and cause this?
Physical vibration in the Micropower SMPS would be a concern, suggesting either miswiring or a faulty PSU - but it wouldn't be likely to cause noise in the audio channels
 
Great! so, can you work through the rest of the list from post #41 and see at what pint the noise starts?
noise only happens when the second board is plugged into the minidsp FlexHT with the primary. :/
 
noise only happens when the second board is plugged into the minidsp FlexHT with the primary. :/
with the flex powered off and no usb cable connected?
Or?
 
with the flex powered off and no usb cable connected?
Or?
With the flex only having the rcas plugged in, do I have any noise (both audio boards). Once I put in the power cord, does the sound get very very little louder.
 
with the flex powered off and no usb cable connected?
Or?
With the flex only having the rcas plugged in, do I have any noise (both audio boards). Once I put in the power cord, does the sound get very very little louder.
I can send you a file of the audio hum that I'm having if that makes things easier.
 
I borrowed my friends receiver, and I can confirm that when both BOARDS (all four RCA) plug into the same source, there's noise. Does this mean a faulty board? Did I solder the chips wrong?
 
I borrowed my friends receiver, and I can confirm that when both BOARDS (all four RCA) plug into the same source, there's noise. Does this mean a faulty board? Did I solder the chips wrong?
If there is noise when the boards are connected to a source that is not powered on, then you probably have a wiring problem. The boards are being connected to each other through the common ground shared by all the RCA cables when they are connected to the source.

An easy check is to connect the boards to each other just with the cables, without any source at all. That is: connect board A input 1 to board B input 1, and board A input 2 to board B input 2 (or A1 to B2 and A2 to B1). Is there noise when you do this?
 
sadly this didn't help. Does lowering the mains voltage to the amp boards help?
to be clear, the wiring advice I gave you DID indeed "help" to at least enable the slave module again to produce audio? Because previously you had stated
there is a slave mode, but once I try it, then there's no audio...
My master/slave wiring advice was intended to address that problem (there's no audio) and I believe this WAS helpful as such.

So what you mean by "didn't help" is that your noise issue remains.

The exact purpose of master/slave is a bit unclear to me. I have read this document https://www.ti.com/lit/an/slaa787/slaa787.pdf which says the following:

Class-D amplifiers use pulse-width modulation (PWM) switching (450 kHz – 600 kHz), which are discrete packets of energy, to deliver large amounts of output power at a very high efficiency. However, issues can arise if multiple Class-D amplifiers switch simultaneously, but are not synchronized and managed. Issues include:
• Power Supply Overloading resulting from all amplifiers switching on the same edge, causing the supply to droop or sag below the regulated voltage.
• Beat Interference or Beat Tones are audible tones that occur when slightly misaligned switching frequencies interact to create another frequency.


The oscillator sync pins allow multiple devices to share a common clock and draw power on different phases to improve performance. Different phases reduce power supply loading during the switch cycles. Sharing a clock improves performance by preventing beat tones.

It seems that YOUR noise is not the type of issue that master/slave was ever intended to solve.

Having seen your pictures, the soldering around opamps and resistors (especially on one of them) looks unclean, perhaps even the board itself (traces) may be burnt. Have you thoroughly cleaned the places where you soldered (say with alcohol and Q-tips)? Can you try various combinations of boards/channels being connected/not connected to isolate this noise to a single channel?
 
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If there is noise when the boards are connected to a source that is not powered on, then you probably have a wiring problem. The boards are being connected to each other through the common ground shared by all the RCA cables when they are connected to the source.

An easy check is to connect the boards to each other just with the cables, without any source at all. That is: connect board A input 1 to board B input 1, and board A input 2 to board B input 2 (or A1 to B2 and A2 to B1). Is there noise when you do this?
There's noise being produced by each channel, but it isn't as bad as being connected to a source? Maybe. I would say this is acceptable (can hear it three feet away in a quite room though).
 
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to be clear, the wiring advice I gave you DID indeed "help" to at least enable the slave module again to produce audio? Because previously you had stated

My master/slave wiring advice was intended to address that problem (there's no audio) and I believe this WAS helpful as such.

So what you mean by "didn't help" is that your noise issue remains.

The exact purpose of master/slave is a bit unclear to me. I have read this document https://www.ti.com/lit/an/slaa787/slaa787.pdf which says the following:

Class-D amplifiers use pulse-width modulation (PWM) switching (450 kHz – 600 kHz), which are discrete packets of energy, to deliver large amounts of output power at a very high efficiency. However, issues can arise if multiple Class-D amplifiers switch simultaneously, but are not synchronized and managed. Issues include:
• Power Supply Overloading resulting from all amplifiers switching on the same edge, causing the supply to droop or sag below the regulated voltage.
• Beat Interference or Beat Tones are audible tones that occur when slightly misaligned switching frequencies interact to create another frequency.


The oscillator sync pins allow multiple devices to share a common clock and draw power on different phases to improve performance. Different phases reduce power supply loading during the switch cycles. Sharing a clock improves performance by preventing beat tones.

It seems that YOUR noise is not the type of issue that master/slave was ever intended to solve.

Having seen your pictures, the soldering around opamps and resistors (especially on one of them) looks unclean, perhaps even the board itself (traces) may be burnt. Have you thoroughly cleaned the places where you soldered (say with alcohol and Q-tips)? Can you try various combinations of boards/channels being connected/not connected to isolate this noise to a single channel?
It did work,as in the modification. It didn't solve my noise issue sadly. I appreciate the help. I did use brake cleaner to clean everything with no luck still. Should I just use the standard balanced to rca? Any negatives to this?
 
Thank you everyone for trying to help me with my issues!
 

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Would just going balanced out fix my issue, or is this more something else?
 
Would changing it to the standard balanced setup fix my issue? Any negatives to this?
 
Would changing it to the standard balanced setup fix my issue? Any negatives to this?
Worth trying. You could ask @3eaudio if there is a way to revert to differential without having to desolder the opamp...
 
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