Ampapa D1 Stereo Amplifier Review

[john61ct]

The way you have phrased this so meticulously as your opinion, there really is no way to argue with it.

Not as if you even imply that you think others should take your statement as objective, much less advice

 

[CptKaos]

The way you have phrased this so meticulously as your opinion, there really is no way to argue with it.

Not as if you even imply that you think others should take your statement as objective, much less advice

pretty much how all audio choices boil down

 

[xlinknz]

Correct, it's a block of anodised aluminium, TPA3255 one side and chassis the other. It's the exact solution Naim use on their amplifiers, only they use thermal compound both sides of the spreader and their chassis is 3mm thick so it works very well... This budget implementation is suboptimal but does now work after correctly applying compound. FYI It's not actually attached to the ribbon cable, just how the photo angle makes it appear. The ribbon cable is attached to the PCB and runs from there to the front panel, both ends of the ribbon cable were hot glued in place which made removal slightly more fiddly.

Yes, I started using a 36v 5A supply in place of the original 48v 5A. Quality doesn't seem very important, mine is a generic cheapie from Amazon but the sound quality is unaffected and there is no detectable added noise or hum etc.

I've not been inside an A80 but just looked on Google images and I agree with you, same problem but that means same solution, just use a 36v supply. The A80 also appears to use many electrolytic coupling caps, whether they affect the sound is endlessly debatable however it has been accepted good practice in higher quality consumer grade gear not to use them in the signal path since the early 80s making the A80 very unappealing to me.

I do intend to push on increasing the D1's long term reliability @48v. This will involve replacing the capacitor near the largest heat source (inductors) with something better, for example the UBY1J182MHL is rated up to 135c, has double the ripple rating and half the ESR of the factory installed Rubycon, it's essentially heaven sent for a Class D PVDD. I would also like to install a fan such as this:

View attachment 539085View attachment 539086

Installation would be simple as there is sufficient room, a local 5v rail and there is already ventilation with the Ampapa cutout, my only concern is noise... If I can hear the fan running at low volumes that would be a problem. Will have to experiment with resistor values to reach an equilibrium between sufficient heat extraction and noise level.

So the D1 does not use electrolytic coupling caps but the A80 does?. I would have thought they'd be the same but maybe that's a cost reduction to compensate for the A80's having a DAC?

 

[Oeilvert]

So the D1 does not use electrolytic coupling caps but the A80 does?. I would have thought they'd be the same but maybe that's a cost reduction to compensate for the A80's having a DAC?

Correct. They are entirely SMD in the D1, at a glance they look ceramic (shock, horror) but maybe a type of film? I'm doubtful as they're all very small.

Electrolytics as far as I can tell:

2200uf Local reservoir for the TPA3255 (PVDD)
2 x 470uf 12v Stabilisation for TPA3255 (VDD)
4 x 220uf x 4 Rail filtering for NE5532
2 x 100uf Local supply decoupling for NJW1194
1 x 100uf Local supply decoupling for CS4344

 

[Panelhead]

Small SM caps are most likely X7 ceramic. You are better off with decent quality electrolytics for signal coupling.

 

[Oeilvert]

Small SM caps are most likely X7 ceramic. You are better off with decent quality electrolytics for signal coupling.

Oh for sure. That said, there may not be any, or at least as many as previously feared.... Been working on reverse engineering the D1 a little today, got most of the power supply worked out now, quite a nice design actually. Opamps and NJW1194 are fed from proper split rail supply so whole thing is DC coupled unlike the A80 which is why that needs endless coupling caps.

 

[Oeilvert]

Oh for sure. That said, there may not be any, or at least as many as previously feared.... Been working on reverse engineering the D1 a little today, got most of the power supply worked out now, quite a nice design actually. Opamps and NJW1194 are fed from proper split rail supply so whole thing is DC coupled unlike the A80 which is why that needs endless coupling caps.

Just to update on this, tracing the signal path reveals that every location you could expect to find a coupling capacitor there is a 0R resistor instead.

One example:

Also completely replaced the thermal compound on mine with Arctic MX-7, the TPA3255 now actually runs cool so I'm happy with that.

For anyone interested, the power supply looks like this:

 

[whazzup]

I'm confused, so for the chinese amps the trend now is to say that there's PFFB when there isn't? Though its saving grace is that at least there's treble control to compensate and knock it down a little?