I just bought for a song an almost brand new NAD PP-2 Phono Preamp. I bought it to use before I finish my Ono preamp.
I can also compare the sound and see if my Ono is as good as the review are saying it is
This is the inside. Pretty neat for such an inexpensive preamp. Already, for the price, it seems to be a bargain.
Very well built, metal film resistors, low noise transistors. Good quality, gold plated connectors, good, small casing. MM and MC separate inputs. Good specs. Difficult to beat even by diy.
If it is worth it, I plan to replace the cheap electrolytic caps inside with some Panasonic FC that I have in stock, can't hurt I guest.
I can also compare the sound and see if my Ono is as good as the review are saying it is
This is the inside. Pretty neat for such an inexpensive preamp. Already, for the price, it seems to be a bargain.
Very well built, metal film resistors, low noise transistors. Good quality, gold plated connectors, good, small casing. MM and MC separate inputs. Good specs. Difficult to beat even by diy.
If it is worth it, I plan to replace the cheap electrolytic caps inside with some Panasonic FC that I have in stock, can't hurt I guest.
Attachments
One thing that can probably be upgraded is the cheap 24V, 100ma wall adapter external power supply. I did some measurements inside the unit. It is using a LM317, adjusted at 20V. The input of the regulator is 26.6Vdc but has 167mv ac of ripple.
The output is 20.1V at 2.4mvac of ripple. I agree to some other posts on the net, that the circuit cannot sink more than 100ma, so there is probably no reason to have a supply more powerful. But a more silent supply can probably lower the noise floor of the preamp.
Anyway, I had all the necessary parts in stock (from previous projects) to build an 24V upgrade power supply. It took a few hours and there it is.
It is using an EMI filter, soft recovery diodes bridges with Wima snubber caps and a nice Panasonic FC 3300uf, bypassed with an 3.3 uf ERO cap. The cheap plastic power cable is now replaced with a nice length of Canare L-2T2S, twisted copper pair, 95% shielded with copper braid. The AC socket can now accept better power cord.
This little supply provides at the input of the preamp 23.8Vdc, 62mvac of ripple and now the output of the regulator is much quietter at 20.1Vdc and less than 0.5mv ac of ripple!
As I said, the parts are probably not optimal, the transfo can be bigger, can have more filtering caps, etc, but they were in stock, and I can do a quick check and see if I get improvements.
The output is 20.1V at 2.4mvac of ripple. I agree to some other posts on the net, that the circuit cannot sink more than 100ma, so there is probably no reason to have a supply more powerful. But a more silent supply can probably lower the noise floor of the preamp.
Anyway, I had all the necessary parts in stock (from previous projects) to build an 24V upgrade power supply. It took a few hours and there it is.
It is using an EMI filter, soft recovery diodes bridges with Wima snubber caps and a nice Panasonic FC 3300uf, bypassed with an 3.3 uf ERO cap. The cheap plastic power cable is now replaced with a nice length of Canare L-2T2S, twisted copper pair, 95% shielded with copper braid. The AC socket can now accept better power cord.
This little supply provides at the input of the preamp 23.8Vdc, 62mvac of ripple and now the output of the regulator is much quietter at 20.1Vdc and less than 0.5mv ac of ripple!
As I said, the parts are probably not optimal, the transfo can be bigger, can have more filtering caps, etc, but they were in stock, and I can do a quick check and see if I get improvements.
Attachments
I don't agree. I'm listening to it right now and the sound is very pleasant. A little bit on the lean side but medium and high are soft and musical. The bass are a little lean but it may be my cartridge, a MC Denon DL-110, see http://www.needledoctor.com/s.nl/sc.2/category.402/it.A/id.234/.f
http://www.positive-feedback.com/Issue15/denondl110.htm
The DL-110 output impedance is 160 ohms. The PP-2 MC input impedance was 100 ohms. Searching on the net, I found that the input impedance for MC should be about 2.5 times the cartridge coil impedance, see: http://www.xs4all.nl/~rabruil/ttadjust.html
So the cartridge was 160R X 2.5 = 400R. I had RN55 film resistors 499R in stock. I opened the preamp, found that the two input impedance matching resistors were R05 and R06, 100 ohms resistors indeed. I installed the 499R resistors instead inside the PP2 and Voilà!
The bass is much better. The sound from this little preamp is very acceptable and goes quite well for casual listening.
http://www.positive-feedback.com/Issue15/denondl110.htm
The DL-110 output impedance is 160 ohms. The PP-2 MC input impedance was 100 ohms. Searching on the net, I found that the input impedance for MC should be about 2.5 times the cartridge coil impedance, see: http://www.xs4all.nl/~rabruil/ttadjust.html
So the cartridge was 160R X 2.5 = 400R. I had RN55 film resistors 499R in stock. I opened the preamp, found that the two input impedance matching resistors were R05 and R06, 100 ohms resistors indeed. I installed the 499R resistors instead inside the PP2 and Voilà!
The bass is much better. The sound from this little preamp is very acceptable and goes quite well for casual listening.
Algar_emi said:
That is just an unfounded opinion. The true required load will depend on the actual case.
Anyway, a high-output MC like the DL-110 is designed for a load impedance of 47k. Not 100, not 500.
Would you care to reverse engineer the PP2 and post a schematic here? I may embark on a modification programme for an acquiantance, but would like to know if it is worth the trouble. I don't have a PP2 on hands.
Thanks
Hi! Algar,
I am a newbie to this DIY thing, most of my DIYing is done on soldering cables to RCAs and power sockets.
I am also new to this phonostage thing, but I do have an NAD PP-2 which I had upgraded the power supply, not as impressive looking as yours, but still got some improvements out of it.
I am now having a slight problem which I really hope you can help me.
I am using a Rega Ellyias MM Cartridge on my table to go with the NAD PP-2, but found the MM gain not insufficient. The NAD specs 34.5db gain for MM. I need something between 42-45db gain.
I was informed by a local DIYer, that by piggybacking a pair of resistor at the pre-out area of the NAD can achieved the desired results. However, he is unable to help me more as distance separates and photos via e-mail can only do so much.
Since you have the NAD with you and have seen the phono board,
can you help me identify which resistors to piggyback and if possible value of resistor required?
Your help is much appreciated.
Thanks.
I am a newbie to this DIY thing, most of my DIYing is done on soldering cables to RCAs and power sockets.
I am also new to this phonostage thing, but I do have an NAD PP-2 which I had upgraded the power supply, not as impressive looking as yours, but still got some improvements out of it.
I am now having a slight problem which I really hope you can help me.
I am using a Rega Ellyias MM Cartridge on my table to go with the NAD PP-2, but found the MM gain not insufficient. The NAD specs 34.5db gain for MM. I need something between 42-45db gain.
I was informed by a local DIYer, that by piggybacking a pair of resistor at the pre-out area of the NAD can achieved the desired results. However, he is unable to help me more as distance separates and photos via e-mail can only do so much.
Since you have the NAD with you and have seen the phono board,
can you help me identify which resistors to piggyback and if possible value of resistor required?
Your help is much appreciated.
Thanks.
Good to see an old thread reviving.
Ok, first I'll re-open my PP2 and will certainly change the load resistor to 47K. I also need to fine tune the VTA of my arm for the Denon cartridge.
Yes Henkel, I'll try to find your answer.
Just a question why don't you try the MC input instead of the MM one. It has much higher gain (but probably to much but worth trying)
The MM section seems to use a basic op-amp gain section. It is maybe not that difficult to figure how to increase the gain.
We will see. I just hope your not in a hurry. I may take a few weeks before I have the time to look at the matter.
I'll let you know.
Bye...
Ok, first I'll re-open my PP2 and will certainly change the load resistor to 47K. I also need to fine tune the VTA of my arm for the Denon cartridge.
Yes Henkel, I'll try to find your answer.
Just a question why don't you try the MC input instead of the MM one. It has much higher gain (but probably to much but worth trying)
The MM section seems to use a basic op-amp gain section. It is maybe not that difficult to figure how to increase the gain.
We will see. I just hope your not in a hurry. I may take a few weeks before I have the time to look at the matter.
I'll let you know.
Bye...
Algar,
Thanks for your reply.
I did try to use the MC input of the PP-2 but the RIAA equalisation is not set up for MM. The sound is louder at 52 db gain, but I got sound that's rolled off from high mids onwards.
Kinda hard to describe but is a very mono like sound but in stereo!
I still need the MM gain section to be higher.
Your help is much appreciated.
Thanks for your reply.
I did try to use the MC input of the PP-2 but the RIAA equalisation is not set up for MM. The sound is louder at 52 db gain, but I got sound that's rolled off from high mids onwards.
Kinda hard to describe but is a very mono like sound but in stereo!
I still need the MM gain section to be higher.
Your help is much appreciated.
Henkel I got your answer. The gain is set by R37 (Left Channel), and R28 (Right). The default value is 249R, gain of about 34dB
If you parallel a resistor of this value with R37 or R38 you'll have these gains:
R38 or R37 // 220R = Gain 40dB
// 100R = Gain 45dB
You should use metal film 1% resistor, otherwise you can have left and right gain missmatch.
Solder the resistor on the bottom of the PCB, much easier.
Try that and let me know.
The image is showing where R37 and 38 are located.
Have fun.
If you parallel a resistor of this value with R37 or R38 you'll have these gains:
R38 or R37 // 220R = Gain 40dB
// 100R = Gain 45dB
You should use metal film 1% resistor, otherwise you can have left and right gain missmatch.
Solder the resistor on the bottom of the PCB, much easier.
Try that and let me know.
The image is showing where R37 and 38 are located.
Have fun.
Attachments
the predecessor, the PP-1, was reviewed by Gary Galo in Audio Electronics 3-2000. He pointed out a couple egregious errors in the design (some were pretty glaring) which have hopefully been corrected in the PP-2. One of the designers responded to the critiques, but it was pretty lame.
One thing of note in your power supply -- the capacitors across the diodes just lower the ringing frequency -- possibly bringing it down into the "hearable" region -- remember that the secondary inductance and the diode capacitance form a resonant circuit. This actually becomes important in a low level gain stage like a phono preamp -- you can demonstrate the ringing in LTSpice.
MUR860's have a capacitance of around 130pf at 24V -- try using a 390 ohm resistor in series with a 1nF capacitor --
One thing of note in your power supply -- the capacitors across the diodes just lower the ringing frequency -- possibly bringing it down into the "hearable" region -- remember that the secondary inductance and the diode capacitance form a resonant circuit. This actually becomes important in a low level gain stage like a phono preamp -- you can demonstrate the ringing in LTSpice.
MUR860's have a capacitance of around 130pf at 24V -- try using a 390 ohm resistor in series with a 1nF capacitor --
WOW!
This thread is turning into a treasure trove to NAD PP-2 users like me!
Algar, you're a genius!
I paralleled R37 and R38 resistors with your suggested resistor value of R100 and R 50, (47 actually) and got the gain that I want.
The value of R100 gave a more laid back sound as with less gain, but the R47 gave a more dynamic kind of sound and it's louder too. The beauty is that the highs becomes very airy. I settled for the R47 resistors.
I had the modded NAD benchmark against Trichord Research's Dino, a phono stage that is about 5X the price of the NAD. The Trichord was set to MM at 48db gain to match the modded NAD.
The NAD was better than the Trichord?, Nope!
As it should, the NAD did not win in any category against the Trichord, but in some respects it's actually pretty close. The most noticeable areas areTrichord had a clear upper hand when it comes to bass control and definition. The Trichord is also a lot better in letting low level resulotion thru the system.
Now I can't wait to do more on the little NAD.
Cheers! guys.
This thread is turning into a treasure trove to NAD PP-2 users like me!
Algar, you're a genius!
I paralleled R37 and R38 resistors with your suggested resistor value of R100 and R 50, (47 actually) and got the gain that I want.
The value of R100 gave a more laid back sound as with less gain, but the R47 gave a more dynamic kind of sound and it's louder too. The beauty is that the highs becomes very airy. I settled for the R47 resistors.
I had the modded NAD benchmark against Trichord Research's Dino, a phono stage that is about 5X the price of the NAD. The Trichord was set to MM at 48db gain to match the modded NAD.
The NAD was better than the Trichord?, Nope!
As it should, the NAD did not win in any category against the Trichord, but in some respects it's actually pretty close. The most noticeable areas areTrichord had a clear upper hand when it comes to bass control and definition. The Trichord is also a lot better in letting low level resulotion thru the system.
Now I can't wait to do more on the little NAD.
Cheers! guys.
After a few days playing with the louder PP-2, I noticed that certain records that sound louder, will overload the input of the pre-amp.
So I switched back the R100 resistors in and settled for 45db gain.
jackinnj. What do you suggest I replace the 220nf caps (the brown ones next to C41 and C42 on the board) with?
Are you saying that I should replace the said caps with a 390ohm resistor in series witha 1nf capacitor?
Curious to get more out of the NAD PP-2 please help?
Thanks.
So I switched back the R100 resistors in and settled for 45db gain.
jackinnj. What do you suggest I replace the 220nf caps (the brown ones next to C41 and C42 on the board) with?
Are you saying that I should replace the said caps with a 390ohm resistor in series witha 1nf capacitor?
Curious to get more out of the NAD PP-2 please help?
Thanks.
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