Topping PA5 Review (Amplifier)

[proplayer69]

Please read the tech note on PFFB carefully, Ti states the THD improvement is max 5 db with pffb. So it is not only PFFB!

You're right, it's not only the PFFB that makes the PA5 a huge improvement in THD. The PA5 and Topping's latest designs use an active phase compensator in the feedback loop that compensates for the reduced loop gain at higher frequencies and the phase shift created by the LC filter. By doing so, they can increase the negative feedback significantly without compromising stability and still maintain a healthy phase margin even with inductor slightly saturating. I bet you all know the theory behind this feedback and compensation thing but i just say it just in case someone don't know. Sorry for bad english, im from east, far from western english

 

[capslock]

Thank you for that explanation. I always suspected the PA5 used a composite approach but that was denied in this thread:

TPA325x composite amp

So the TPA325x series of chip amps came out about a decade ago, yes really that long! My datasheets for the TPA3251D2 are dated June 2015 and that's where we happen to be now only 10 years later, so, happy birthday TPA325x series. :Present: Over the years I've seen it mentioned a couple of...

www.diyaudio.com

When you say active, does it mean there is an op-amp in the feedback loop?

Is there any documentation about the feedback loop? I looked at gamerpaddy's reverse engineered schematic of the potted module but of course, without knowning the schematic of the main PCB, one cannot understand the full circuit and feedback/compensation strategy.

Part of the reason why some 325x amps (PA5, 3e AF5, Wiim Vibelink) are so much better than standard PFFB amps is their gain structure. They shifted some of the gain needed to the preamp stage. But that is just the flip side of the coin of saying the achieved more feedback around the 325x.

 

[NTK]

If Topping implemented its patent in the PA5, it is a composite design.

CN216959816U - High-fidelity D class audio amplifier circuit - Google Patents

The utility model provides a high-fidelity D-class audio amplification circuit which comprises a filter circuit, a D-class power amplifier and a low-pass filter, wherein the filter circuit is electrically connected with the D-class power amplifier, the D-class power amplifier is electrically...

patents.google.com

 

[F1308]

Merry Christmas.
My PA5 still working flawlessly.

 

[xaxxon]

Merry Christmas.
My PA5 still working flawlessly.

Great for you. The point is that it's not supposed to fail for nearly as many people as it did. "not every single one died within 6 months" is not the bar we should be holding places accountable for getting over.

 

[MAB]

Merry Christmas.
My PA5 still working flawlessly.

They are so fragile every Christmas it's still working is a gift.

 

[gvl]

My PA5 still working flawlessly.

Chances are you just jinxed it

 

[Roland68]

Chances are you just jinxed it

No, Topping already did that when they potted the modules with potting compound.

They are so fragile every Christmas it's still working is a gift.

Once the potting compound is removed, the circuit board underneath is cleaned, and all solder joints are checked, the PA5s are absolutely reliable.
I've refurbished over 15 of them now, and they're all running perfectly.

 

[F1308]

Chances are you just jinxed it

No, no, no... I never do, and you shouldn't either... Just connected it to my Fantom 8 and a pair of Mythos ST. I love the sound immensely. It feels like it's coming out of thin air, like magic.

 

[Martinvb]

No, Topping already did that when they potted the modules with potting compound.


Once the potting compound is removed, the circuit board underneath is cleaned, and all solder joints are checked, the PA5s are absolutely reliable.
I've refurbished over 15 of them now, and they're all running perfectly.

Interesting! Could you enlighten us and explain how you did that? I would be interested to do that myself.

 

[Roland68]

Interesting! Could you enlighten us and explain how you did that? I would be interested to do that myself.

Please only attempt this if your PA5 has this defect, is no longer functioning properly, and Topping does not replace it.
Otherwise, you risk turning your PA5 into a paperweight.

Information on this can be found in the threads "Poll for Topping PA5 owners only please" and "Topping PA5 fix - D01 Module Replacement for everyone" by @gamerpaddy , who can also supply a replacement module.