NAD 2200PE upgrading

[tonimxp]

Hi guys, what do you think about swapping the C313-C314 0.1uF electrolytic capacitors for polypropylene?

Under the Mouser code:

505-MKP2.1/100/10

Another question...
Is it possible to reduce the input stage from 7 dB to 0 dB (as buffer use) without affecting the frequency response?
I've currently noticed a slight hump around 10 kHz, which then straightens out.
I think it could be caused by the input filter.

 

[pwauk12]

Hi Peter!

My input board is labeled SW-610A, not SW-594 as in the service manual, and it has some capacitors that are not shown in the manual: C117, C118, and C119. (The front is labelled "2200 Power Envelope".)

Have you come across this board revision? If so, what did you use for C117–C118? (C119 seems insignificant to me, since I won’t be using bridged mode.)

In the circuit diagram, C117–C119 are marked 270K, which I assume means 0.27 µF. On my board, they are marked “27”.

Another difference between these revisions is the values of C105–106, which are 1 nF in this revision, and C107–108, which are 820 pF.

The parts lists for the two versions appear to be identical, so they don’t seem to have been updated.

Since you seem to have re-capped several NAD 2200s, I thought you might have come across this version and dealt with it before. I would be grateful for any suggestions.
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Hi

yes this is alter board revision- what version are your main boards?

the "27" are 27pf ceramic caps, and can be left in place or replaced withe 27pf C0G/NP0 ceramics.
The later versions had 1000pf (C105/C106) and 820pf (C107/C108)- use Wima FKP or similar

Peter

 

[pwauk12]

Hi guys, what do you think about swapping the C313-C314 0.1uF electrolytic capacitors for polypropylene?

Under the Mouser code:

505-MKP2.1/100/10

Another question...
Is it possible to reduce the input stage from 7 dB to 0 dB (as buffer use) without affecting the frequency response?
I've currently noticed a slight hump around 10 kHz, which then straightens out.
I think it could be caused by the input filter.

Hi,

for the caps that will work-polypropylene of polyester- you can also change them to 4.7uf as NAD did on the 2700's

There should not be a 10Khz hump, which suggests a component is out of spec (cap most likely). You can probably reduce the gain by making it all unity, but this will affetc the overall amp gain. There should be no relationship between the gain and the FR

Peter

 

[tonimxp]

Hi,

for the caps that will work-polypropylene of polyester- you can also change them to 4.7uf as NAD did on the 2700's

There should not be a 10Khz hump, which suggests a component is out of spec (cap most likely). You can probably reduce the gain by making it all unity, but this will affetc the overall amp gain. There should be no relationship between the gain and the FR

Peter

Hi Peter! Thanks for your reply!
Do you know how i can reduce gain by opamp resistors?
Antonio

 

[nicst]

Hi

yes this is alter board revision- what version are your main boards?

the "27" are 27pf ceramic caps, and can be left in place or replaced withe 27pf C0G/NP0 ceramics.
The later versions had 1000pf (C105/C106) and 820pf (C107/C108)- use Wima FKP or similar

Peter

Many thanks for the prompt reply!

My main boards are 593B.

I am planning to do what you write on your website, "also remove and bridge C115/C116. On the later versions of the 2200PE with B or C boards I have adopted this approach".

I settled on LM4562NA as these are BJT front end rather than FET - as is the OPA2134

I am planning to use LME49720NA, which apparently is the same op-amp as the LM4562NA.

I am also planning to increase C117–C119 (the three 27's) to 100 pF, as in the 2700. Do you think I should change the feedback resistors as well?

Any other concerns with this approach?

 

[pwauk12]

Many thanks for the prompt reply!

My main boards are 593B.

I am planning to do what you write on your website, "also remove and bridge C115/C116. On the later versions of the 2200PE with B or C boards I have adopted this approach".



I am planning to use LME49720NA, which apparently is the same op-amp as the LM4562NA.

I am also planning to increase C117–C119 (the three 27's) to 100 pF, as in the 2700. Do you think I should change the feedback resistors as well?

Any other concerns with this approach?

Hi-

yes do change the resistors to match the 2700 values and add 47uf low impedance across the power rails for each of the IC's on the input board (with 0.01uf in parallel)

Peter

 

[pwauk12]

Hi Peter! Thanks for your reply!
Do you know how i can reduce gain by opamp resistors?
Antonio

why do you want to reduce the gain?

 

[tonimxp]

why do you want to reduce the gain?

For obtain wider range on my tube preamp volume control , as already told from

pskaudio other member in this thread . I agree with him.​

 

[tonimxp]

why do you want to reduce the gain?

Problem solved !
I took the time to study where I could reduce the gain without expecting any "strange complications," and I discovered (and tested) that by increasing R121-R122 from 1K to 56K, I was able to achieve exactly what I wanted (20dB gain), which is the same gain as my Aleph 30.
Now everything is OK!

 

[tonimxp]

I came up with this upgrade shortly after I bought the 2200 in1984. Compared to my old amp the 2200 sounded flat, lacking in depth and transparency. So, being an audio engineer I set to work and changed the crummy caps for those mentioned above. Made all the difference. Now it sounded like it should have. I did some other mods at a later date. Replaced the input op amps with op275s. Also replaced the Class G switching diodes (S6K20) with Schottky power diodes (MBR10100). These mods got rid of a huge switching glitch when the amp went into high power mode. Now it transitions smoothly. Added four servos so the amp is now DC coupled from input to output. This solves the problem of drifting DC on the output and gets rid of some nasty distorting caps. I also redesigned some of the main amp input circuitry as they cut too many corners in order to save money. So now I have an amp which can hold its own against any amp you care to name.

I already have in my drawer 4 PCS of SRAF10150 it is also a good choise for replacement of S6K20?

 

[burnologist]

Hi everyone. I'm a bit of a newbie. Can someone explain what "eplace with short if servo, else shunt with 2uF polypropylene" means? specifically, what is servo referring to? I have SW-594B input board.

Also, any recommendations for swapping the RCA connectors? Mine are cracking and I can't find a similar part anywhere

 

[burnologist]

Update:
I made the following mods to the input board:
C111-C114: CAP TANTALUM 10UF 10% 50V (Digikey P/N: TAP106K050CRW)
C107,C108: WIMA CAP FILM 1000PF 2.5% 250VDC (Digikey P/N: FKP2F011001D00HSSD)
C115,C116: Shorted the leads without removing the Caps.
IC101-102: OPA2134PA-ND

Plugged it back in, it was fine for 30 seconds, then BOOM! loud pop out of speakers and it went into protection. It came out after a bit. When I turned it off, there was another small pop out of my speakers. I inspected the input again. didn't notice anything wrong. Removed the short across C115 and C116, plugged it back in, and turned it on. It was fine again for about a minute before another loud pop and going back into protection. This time it never came out.

Is there anything wrong with the modifications that I have done so far that could've caused this?

 

[pw5599]

That is not good. I would remove all mods and return it to og. That's just me, it's what I would do. But it may be too late, the damage may be done.

 

[burnologist]

My

That is not good. I would remove all mods and return it to og. That's just me, it's what I would do. But it may be too late, the damage may be done.

I'm thinking it has to do with the protection circuitry. For some reason it didn't like the new ICs or the caps on the +18V -18V lines that feed them. (10uF instead of 0.01pF). Or maybe the OPA2134 somehow draws more current, causing the protection circuit to trip? Can anyone confirm this?
I'm currently inspecting the unit to see if I can identify any issues along the power lines and protection circuit. I will share my findings.

 

[Pilot]

Search this forum for my mods to the NAD2200. I used stacked mylar for C313/C314 since they are small and are not part of the signal circuitry. However, polypropylene will do just as well.

Bryan

 

[burnologist]

I figured out what happened. I didn't know tantalum caps are polarized. I was treating them like a ceramic and two of them flipped. It is corrected and no issues.

 

[Sharky0816]

Recently picked up an NAD 2200PE that would not come out of protection mode. With some investigating I found the +18V supply was outputting 1V, that's not good. Turns out IC401 JRC78M18 regulator is kaput. Swapped in a new MC7818C and the amp comes out of protection mode after a few seconds as it should. I have full intentions on swapping IC402 for the matching negative MC7918C.
But, I was thinking.....Why not use discrete regulators like Sparkos or Belleson in the +/-18V supply? This supply feeds the opamps and front end, why not improve the supply to these sections?
Just curious if anyone has tried this modification.

While I was in there, the small elco caps, relays and R413 (new value 270R) were replaced.

 

[Sharky0816]

After replacing the +/-18V regulators, I pulled the input board SW-610B for some tweaking.
I don't plan to use the NORM input so didn't change any caps before LAB input. Used Vishay MBB and CMF resistors in the signal and feedback path and followed the 2700 scheme for reference to component value changes. Removed C115/116 and added wire jumper, added local opamp decoupling Panasonic FR caps with // surface mount C0G/NP0 between the legs. LM4562 installed, but the meandering layout of the power traces to the opamp does not allow the MCLL caps to get very close to the power pins. Oscillation could be a problem with modern fast opamps? Last but not least, Silmic II caps occupy C109/110.
Fired up the amp, no magic smoke escaped, Yayy!
Definitely a very noticeable improvement in focus and clarity...... But, the amp has too much gain to work well in my systems. Next move will be to bypass all the tidy work on the input board for a direct input signal and reduce overall gain.

 

[Sharky0816]

I went back in and made the modifications to bypass the input board as @pskaudio mentioned in post# 179. If you want to shed some gain, your source/preamp can handle ~20K input impedance and won't use the amp in bridge mode this is the best improvement in sound I've heard from the 2200PE so far. Used the 2700 schematic as a reference along with recommendations from pskaudio and pwauk12 for recapping the MAR/L593C boards. Some creative lead bending to fit the bigger caps in key locations, but all worked out well. Decided not to change the main caps, they measure fine. This experiment was more out of curiosity and purchasing the required caps would blow the 'cost to fun" factor out of whack. To be honest, after the relays were replaced, I wasn't impressed when I first listened with 2200PE in the system. The single biggest improvement was bypassing the input board circuitry, then increasing the tiny power supply rail caps, input cap to Muse ES and negative feedback cap also to Muse ES. Now this amp is a fun listen and even generates some toe tapping to music.