Topping PA5 fix - D01 Module Replacement for everyone

[Mr. Wax]

It is the left channel. I poked it many times with a toothpick.

It made no changes to the sound volume nor distortion levels.

Thanks!

 

[gamerpaddy]

ask your guy to swap the left and right opamps and see if the problems moves with it. if yes, one or more opamps is dead on that side, if not, problem is somewhere else

 

[Jukka]

Hi everyone.

I have an opportunity to acquire one or two PA5 units for a very low cost (less than 50 €). So I was wondering if getting and fixing them would be worth the effort, even though I have no immediate need for them. I would soon need a small amp for my work desktop set. I have one TPA3116 based, but this opportunity sparked my interest.

1) Is it possible to modify the unit with a stock pot or modify the pot itself to extend it's life?
2) Does @gamerpaddy still have replacement boards?

 

[gamerpaddy]

@Jukka
i definately would buy another pa5 if its just 50 bucks, even tho i dont need another one.
due to my repair hobby i collected some neat stuff over the years, some big boys like asr emitter, accuphase, yamaha 1000' series, nad, rotel.. but i still prefer and use the pa5 for listening 99% of the time.

you could bridge the pot to bypass it entirely. you could also replace it with another 4way (100k logarithmic i think it was) but i havent had a failed pot on a pa5 yet. its more a ayima disease

i got at least one module left.. two if the guy that asked two weeks ago for one doesnt answer soon.

 

[Mr. Wax]

ask your guy to swap the left and right opamps and see if the problems moves with it. if yes, one or more opamps is dead on that side, if not, problem is somewhere else

I have had the left opamps changed, unfortunately the issue still remain : the left side being quieter and distorting.

The troubleshooting is beyond my local repair guy's abilities, unless you would have something else to suggest we look into.

Thanks in advance for your time and happy new year!

 

[gamerpaddy]

i test every module i made before shipping it out, ordering them yourself at the pcb fab is cheaper but also means you gotta put time and money into it in case something doesnt work.
if he had a oscilloscope and know how schematics are read he could check the signal path properly to pin point where the issues starts. if its happening before or after the module, before or after the first stage etc.
i dont think there are any misplaced components but if they had a reel of 100000 resistors and a a single failed one that they put on your board you better buy a lottery ticket.
he could check those yellow caps for short circuits, they are made of ceramic and if the board flexes slightly they can crack (not visibly) and short out.

 

[ITJ]

I am on the fence with this Amplifier. (PA5 II)
Having read the many problems with the potting compound due to what seems to be heat. I believe I read here that the volume pot can be bypassed, which would be a working solution for me as I like to use it in combo with an E30 DAC and user its volume control.

Is there something else to do about the heat to make it more reliable?

 

[Ricwa]

I am on the fence with this Amplifier. (PA5 II)
Having read the many problems with the potting compound due to what seems to be heat. I believe I read here that the volume pot can be bypassed, which would be a working solution for me as I like to use it in combo with an E30 DAC and user its volume control.

Is there something else to do about the heat to make it more reliable?

Note that the PA5 II is a newer model than the original PA5. Changes were made to mitigate the reliability problems in the original and, although it’s early days, there have not been any significant reliability problems reported in the PA5 II to date.

 

[capslock]

Great work! For those building it, getting metal film rather than thick film resisitors is probably more important than worrying about the small extra distortion introduced by the 5532. It might also be worthwhile to redo the layout to accept larger resistors (0804, 1206 or preferably MELF).

 

[mocenigo]

From the reverse engineering, is it a composite amplifier? And actually four of them because there are two channels and they are balanced?

 

[Roland68]

From the reverse engineering, is it a composite amplifier? And actually four of them because there are two channels and they are balanced?

TPA3255/3251 are 4 channel amplifier ICs. You can also operate these as 2 channel (btl) or mono (pbtl). Inputs and outputs must be configured for this.
You can only operate the PA5 as a 2-channel amplifier.

 

[gamerpaddy]

the tpa3255 doenst have a negative supply, its output cant go blow ground level so you need two outputs that push one after another so ground level is on positive and negative for each half cycle.

technically its possible to float the outputs at vcc/2 if the tpa doesnt kick any protection mechanism in and run it as 4 channel but not without major modifications.

the TAS5630 can do this, see page 19 of its datasheet. capacitively floats the negative terminal between gnd and vcc

https://www.ti.com/lit/ds/symlink/tas5630.pdf

 

[mocenigo]

TPA3255/3251 are 4 channel amplifier ICs. You can also operate these as 2 channel (btl) or mono (pbtl). Inputs and outputs must be configured for this.
You can only operate the PA5 as a 2-channel amplifier.

The buffer has, per se, nothing to do with the configuration of the TPA3251/55. It is quite agnostic. If I can follow its circuit properly, it takes the inputs of two channels (which can be RCA or balanced), creates a balanced signal per channel, and then you use these to drive the next stage. In particular, for a TPA3251/55 you can use them to drive the channels pair-wise as hot+cold, so you get balanced outs for the speakers.

 

[Roland68]

The buffer has, per se, nothing to do with the configuration of the TPA3251/55. It is quite agnostic. If I can follow its circuit properly, it takes the inputs of two channels (which can be RCA or balanced), creates a balanced signal per channel, and then you use these to drive the next stage. In particular, for a TPA3251/55 you can use them to drive the channels pair-wise as hot+cold, so you get balanced outs for the speakers.

Of course, the inputs/input buffers on the TPA3255/3251 must be configured to match the outputs.
With the PA5 you only have a differential input, with the PA5 II you also have an SE input. But you have to select it on the front panel with a switch that switches internally in the PA5 II relay for it.
All options for input and output configuration are described in the TPA3255EVM manual, see Table 4.
In the text under Tables 3, 5, 6 and 7 you can read how the inputs and outputs are connected and also when they require inverted and non-inverted input signals. For example, you can read in Table 7 that 4 non-inverted signals are required for 4-channel operation (4 x in/4 x out).
The signal processing in the input circuit is configured with jumpers J4/J19.

 

[akafreak]

My PA5's left channel has gone quiet after 14 months of use. I can try going for Topping's 2 year warranty but honestly that is too much trouble when they are replacing the defective potted module with another potted module which will go bad again. And I will have to pay for shipping.

So, going to try the gamerpaddy replacement board. I can only get the PCB manufactured and then will have to solder the components myself. I have very basic soldering experience. So, few questions. Would greatly appreciate if anyone could help:

• The capacitors are 50v or any other voltage?
• I can use 4 OPA1612AID, right? Or do I need, 2 NE5532DR and 2 OPA1612AID?

 

[mocenigo]

The really sad thing (as the OP to this thread shows) the IP obfuscation can be circumvented by one guy working alone in a few hours. How long did it take their competitors do you think?

Topping near massacred their own reputation for absolutely no benefit whatsoever.

And apparently the D90mkIII has a lot of small potted, or at least encapsulated, modules…

 

[gamerpaddy]

My PA5's left channel has gone quiet after 14 months of use. I can try going for Topping's 2 year warranty but honestly that is too much trouble when they are replacing the defective potted module with another potted module which will go bad again. And I will have to pay for shipping.

So, going to try the gamerpaddy replacement board. I can only get the PCB manufactured and then will have to solder the components myself. I have very basic soldering experience. So, few questions. Would greatly appreciate if anyone could help:

• The capacitors are 50v or any other voltage?
• I can use 4 OPA1612AID, right? Or do I need, 2 NE5532DR and 2 OPA1612AID?

50V ceramic smd capacitors, the most common type. you only go 25v or lower if you need more capacity .. like 10uF or more. not needed here.

my pa5 runs all 4x opa1612 no problem, but you dont get any benefits, it doesnt sound better or anything it just costs more.