NAD PP2 circuit diagram / schematics

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Werner

Member
Joined 2002
#1
Hi all,

months ago I reverse-engineered an NAD PP-2. Here is the conceptual diagram. Note that abstraction has been made of the actual semiconductors, and that the passives numbering does not match that on the PCB.

It is essentially a PP-1 with an MC headamp added to it. Note the copious use of elcaps for coupling. Also note that total MC gain is about 58dB, as opposed to the promised 60dB.
 

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#2
Note the copious use of elcaps for coupling
Click to expand...


Sickening indeed. If something sells cheap it absolutely needs to be nasty. Lots of free ways to avoid C18/16 but why make the effort?!
And C1? Either paranoia or a really bad opamp.

Thanks for making the effort to publish this. It's nice to know what people mean when they say they like the PP2.
 
#4
... since I have a PP2 which seems to do a fair job (although I have not paid the PP2 yet), reading this topic makes me wonder if it is worthwhile making the effort building a VSPS or if it would be better to invest in a better design or if it may be best to simply pay the PP2.

Just saying that the PP2 is a piece of junk is so easy. Could you elaborate on the differences in sound between a PP2 and a VSPS?
 
#5
Could you elaborate on the differences in sound between a PP2 and a VSPS?
Click to expand...

My english is not good enough, I fear.

Let's try: the PP2 has no dynamics, bad bass, weak mids, no highs compared to the VSPS or phonoclone.

I used it with a Shure V15-III and a Denon DL103.

My recommendation: build a VSPS!

Kind regards
Franz
 
#8
The sad part is that NAD obviously knew how to make a decent phono stage 20 years ago. And it wasn't even high-end 🙂 Some of their integrateds (3150?) had a very nice sounding phono stage (MM). It used a discrete opamp - Jfet diff input and another 4-5 bipolars and discrete PS regulators. At the time i built a clone using reasonable quality parts - the original parts were indeed horrendous - and quality wise it was easily as good as a Pass Ono. So much for progress.
 
#11
I would have to politely disagree with your assessments of the NAD PP-2 as I have found that what you guys say about it in this thread is only partly true.I did get burned once with the earlier model the PP-1 and I agree that it was for the most part a "disappointing" unit,but the PP-2 is different.The thing that won me over was to upgrade the power supply from the "poor" unregulated version that comes with the unit to a regulated one and Voila! bass,dynamics,detail etc.It is so good in fact that it bests a Moth 30V series 12v Phono Stage currently sold online for 275 Pounds-3 times the NAD's price.I lie not as I have done the A/B and the NAD wins.It is a poor sounding unit with that awful stock supply no bass etc,much as described,but once it doesn't have to fight for power it is quite a nice little unit for the money,better than the Creek also I hear.
 
#12
Indeed, this could be a big change, a good tweak for the PP2, to use a state of the art psu.

But you will still have FOUR electrolytics in the signal path. I for myself, I avoid such a signal path in my phono equipment. Just my personal opinion, of course.

One good cap at the output of a phono pre should do the job. Should you worry about an expensive cartridge, why not a cap at the input or, for a MC, a stepup transformer.

Again: for the same money you spend for a PP2, you easily build a phonoclone or VSPS in very good quality, including psu.

Franz
 
#13
You are right,of course it is cheaper to build it yourself,but if you have the stock NAD-PP2 already,a quick upgrade is to replace that unregulated power supply unit.There is a guy on Audiogon that does just that,selling over-priced, larger,unregulated(still) power supplies(up to 1000mA I think).What to do is make sure you get a regulated power supply unit mine is 24VDC 1Amp regulated,really did the trick!
 
#14
unregulated(still) power supplies(up to 1000mA I think

You are right,of course it is cheaper to build it yourself,but if you have the stock NAD-PP2 already,a quick upgrade is to replace that unregulated power supply unit.There is a guy on Audiogon that does just that,selling over-priced, larger,unregulated(still) power supplies(up to 1000mA I think).What to do is make sure you get a regulated power supply unit mine is 24VDC 1Amp regulated,really did the trick!
Click to expand...

I am thinking of buying a NAP PP-2. Sorry about my ignorance but what do you do with the original power supply?
Thanks
 
#20
Bigger PSU always helps on these affordable add on boxes.....
Well sadly, even on my ECP1 from Electrocompaniet too...

The supplied wallwart of the PP2 uses a whole 470mfd of smoothing before entering straight in to the regulator inside the unit. Just adding capacitance there helps a lot, in the box or in the wall wart. Soft recovery diodes as well. That opamp, yes, so many other choices, pick your flavour.

Ofcourse all those electrolytics in the signal path come from the lowest bidder......

WRT to a regulated PSU, I have not tried that on a PP2 yet but I have before on a Electronics and Wireless World design and distinctly preferred +-15 V supplies single regulators to feeding these into another set regulating down to +-12.
Could have been headroom of the PSU or current limiting that made the difference I suppose but thought +-12 should have been fine....
 
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