Hi,
in a second system, I have a NAD 2100 amp with a very simple embeded switchable preamp and two 5K carbon volume pots... I like this to permitt a good set up of the stereo image... one needs a replacement.
The preamp section is maid by a JRC 2043D oap. NAD maid some effort on its PS : Pi filter, snubers, 4 transitors regulation...
It is musical as it is and not an ambitious device but I would like to know please if something can be gained by swapping the oap (modern one or not) ? Does it worth ?
regards
in a second system, I have a NAD 2100 amp with a very simple embeded switchable preamp and two 5K carbon volume pots... I like this to permitt a good set up of the stereo image... one needs a replacement.
The preamp section is maid by a JRC 2043D oap. NAD maid some effort on its PS : Pi filter, snubers, 4 transitors regulation...
It is musical as it is and not an ambitious device but I would like to know please if something can be gained by swapping the oap (modern one or not) ? Does it worth ?
regards
I would say yes. The 2043 is just a variation of the 4558.
Two devices to try, and each would be "different". The LM4562, which is about as good as it gets, and the OPA2604, which is somewhat "coloured" in comparison but can work wonders in the right system. Both are superb, its personal choice which you would prefer.
Disclaimer... as ever when swapping opamps... don't assume that any replacements will be stable although in a preamp circuit like this there should be no issues.
Two devices to try, and each would be "different". The LM4562, which is about as good as it gets, and the OPA2604, which is somewhat "coloured" in comparison but can work wonders in the right system. Both are superb, its personal choice which you would prefer.
Disclaimer... as ever when swapping opamps... don't assume that any replacements will be stable although in a preamp circuit like this there should be no issues.
Thanks Molly,
My fear was the D letter meaned higher current so difficult to find a good challenger....
I know well the 2604 and agree with you on this non universal character...especially in the low end - in some buffer stage I tested in CD players. Btw the same with 5534... creamy treble is prefered by me with both...
I will try maybe also the JRC 2114 which can be neutral...
The amp has a good sound enough : I just added 1500 uf Panasonic FC on the 10 K uF main caps and some KZ muse and Panasonic FM on the main amp circuit for the small values. The pre section was flavored with Elna Silmic I (better and less charicatural then the S II) and 1200 uF Lelon 105° as filtering diodes bridge for the preamp section were keeped as BC136 or FM/FC caps were worst here.
Will try this famous LM4562... often read about it here !
My fear was the D letter meaned higher current so difficult to find a good challenger....
I know well the 2604 and agree with you on this non universal character...especially in the low end - in some buffer stage I tested in CD players. Btw the same with 5534... creamy treble is prefered by me with both...
I will try maybe also the JRC 2114 which can be neutral...
The amp has a good sound enough : I just added 1500 uf Panasonic FC on the 10 K uF main caps and some KZ muse and Panasonic FM on the main amp circuit for the small values. The pre section was flavored with Elna Silmic I (better and less charicatural then the S II) and 1200 uF Lelon 105° as filtering diodes bridge for the preamp section were keeped as BC136 or FM/FC caps were worst here.
Will try this famous LM4562... often read about it here !
Looking at the circuit, I'd say you could use most anything that feels comfortable driving 2 Vrms into 3 kOhms at a non-inverting gain of 2.2 and has reasonably low voltage noise. Impedances are fairly low, bypassing appears to be decent. NJM2043 is a pretty good match to begin with, LM4562, NJM2068 or NE5532 should also work well.
Note that this unit uses el cheapo carbon film resistors throughout that may be worth upgrading in critical spots. I'd look at: R312, R314, R310, R405, R425, R431 (1 W) and R433 (1/2 W), plus their right-channel equivalents. It's not so much for the noise aspect - usually the preamp is going to dominate that anyway - but more the linearity.
You may also want to replace C307/308 by some nice bipolars (ditto for C417/418).
BTW, does anyone have a clue how the VAS in the power amp works, or rather how they go from differential input to VAS? (HFE has docs for this one.)
Note that this unit uses el cheapo carbon film resistors throughout that may be worth upgrading in critical spots. I'd look at: R312, R314, R310, R405, R425, R431 (1 W) and R433 (1/2 W), plus their right-channel equivalents. It's not so much for the noise aspect - usually the preamp is going to dominate that anyway - but more the linearity.
You may also want to replace C307/308 by some nice bipolars (ditto for C417/418).
BTW, does anyone have a clue how the VAS in the power amp works, or rather how they go from differential input to VAS? (HFE has docs for this one.)
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Wooow, thanks to had a look at the circuit !
I will try the three oap... (yeap 5532 and not 34 always mistake with the mono ref !) This amp is nice and drive with no problems my second system which is a switch between a Proac D15 and its very accurate tones and a punchy mid bass Kef 104/2 Reference !
I will say Nad seems to mix on the pcbs carbon and metals resistors for a more smooth sounds (controlled distorsions). Which types of (metal?) resistor would you advise here instead about the positions you gave ? standard one or some better choosed brands (Hificollective or Partconexions) ?
I maid many tests just with caps on the preamp section : standard Black Gate e.g. here are horrible, the theoric bad first Lelon Long Life does their job and are better than others 105°c BC 136 with low esr... I like to do simple empiric tests as I have no scopes and the knowledge behind it !
(Briefly what would be your advice for the few transistors of thr preamp stage ! In real life the preamp circuit involved long distance of cheap coax wires between input RCAs and preamp section; cheap carbon pots. The powerstage of the pre section is connected with the pots/oap little pcbs with wires for both PS & signals)
But still thinking Nad can makes smart cheap designs and this amp is one of the good amps they maid ! Good main power transistor (used by High End brands as well...). I buyed it at 22 off the shelf for 140 euros (francs at these days...) and it was my first serious amp ! Like it and never sell it !
Thanks guys for your kind advices.
I will try the three oap... (yeap 5532 and not 34 always mistake with the mono ref !) This amp is nice and drive with no problems my second system which is a switch between a Proac D15 and its very accurate tones and a punchy mid bass Kef 104/2 Reference !
I will say Nad seems to mix on the pcbs carbon and metals resistors for a more smooth sounds (controlled distorsions
). Which types of (metal?) resistor would you advise here instead about the positions you gave ? standard one or some better choosed brands (Hificollective or Partconexions) ? I maid many tests just with caps on the preamp section : standard Black Gate e.g. here are horrible, the theoric bad first Lelon Long Life does their job and are better than others 105°c BC 136 with low esr... I like to do simple empiric tests as I have no scopes and the knowledge behind it !
(Briefly what would be your advice for the few transistors of thr preamp stage ! In real life the preamp circuit involved long distance of cheap coax wires between input RCAs and preamp section; cheap carbon pots. The powerstage of the pre section is connected with the pots/oap little pcbs with wires for both PS & signals)
But still thinking Nad can makes smart cheap designs and this amp is one of the good amps they maid ! Good main power transistor (used by High End brands as well...). I buyed it at 22 off the shelf for 140 euros (francs at these days...) and it was my first serious amp ! Like it and never sell it !
Thanks guys for your kind advices.
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A better guess re the use of Carbon and Metal resistors is Price
At the time that Amp was designed Metal films cost More than carbons (no longer)
NADs were/are a decent 1st world design sent off to be built as cheaply as possible in the 3rd world.. no more no less.
Most assuredly ALL those carbon comp resistors will have drifted in value (gone higher in Ohms) over the years, effecting subtle and often not so subtle changes
At the time that Amp was designed Metal films cost More than carbons (no longer)
NADs were/are a decent 1st world design sent off to be built as cheaply as possible in the 3rd world.. no more no less.
Most assuredly ALL those carbon comp resistors will have drifted in value (gone higher in Ohms) over the years, effecting subtle and often not so subtle changes
I will check the values this winter...
Here the weather is so nice to do DIY... (but the night when family sleep with a glass of wine and smooth jazz of course... there are some limits to the non confort !)...
What resistors & brand are advised for replacement nowadays? Is the cements resistors needs a more serious ref as a Kiwame or non inductive wirewound?
I'm con of light tweaking but not spend 100 euros in relation to the layout limitations of this amp e.g. : my aop askings : cheap to test with Dil support before definitive soldering !
I will carefully test the oaps first : here I have 4 refs given and have already 2 !
Here the weather is so nice to do DIY... (but the night when family sleep with a glass of wine and smooth jazz of course... there are some limits to the non confort !)...
What resistors & brand are advised for replacement nowadays? Is the cements resistors needs a more serious ref as a Kiwame or non inductive wirewound?
I'm con of light tweaking but not spend 100 euros in relation to the layout limitations of this amp e.g. : my aop askings : cheap to test with Dil support before definitive soldering !
I will carefully test the oaps first : here I have 4 refs given and have already 2 !
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Dunno what you are after.
But decent quality Metal film resistors are Very cheap to buy ~a penny each in small quantities.
Even Vishay ones are only a few cents each.
If mine; I would reinsert Identical opamps ... assuming they have a problem.. do they?
Switching Opamp brands / types is not always "fool" proof.
Few are exactly compatible drop in replacements. Be 100% sure your intended ones actually are
Getting the old girl back to 'as built' condition may prove as a rewarding improvement by itself.
But decent quality Metal film resistors are Very cheap to buy ~a penny each in small quantities.
Even Vishay ones are only a few cents each.
If mine; I would reinsert Identical opamps ... assuming they have a problem.. do they?
Switching Opamp brands / types is not always "fool" proof.
Few are exactly compatible drop in replacements. Be 100% sure your intended ones actually are
Getting the old girl back to 'as built' condition may prove as a rewarding improvement by itself.
Agree. Btw fellows above give just few ref for a very close match I assume.
Ears will tell me after many hours of listening if swap is good or not (it's an hobby, time is not spent !). Happy with that list of 4 oap, i have not too many ref here to try.
I'm more suscidcious about 100% metal resistors. i'm not against some carbon and a descent pleasant distorsion (maybe to hide some others
defaults that such cheap models have... trade off) against a more sterile acurate sound. But have few experience with resistors. Advises are welcome if it worths a swap.
Ears will tell me after many hours of listening if swap is good or not (it's an hobby, time is not spent !). Happy with that list of 4 oap, i have not too many ref here to try.
I'm more suscidcious about 100% metal resistors. i'm not against some carbon and a descent pleasant distorsion (maybe to hide some others
defaults that such cheap models have... trade off) against a more sterile acurate sound. But have few experience with resistors. Advises are welcome if it worths a swap.
Resistor types can devolve into a never ending arguement.. Fill your boots.
Significant issue is that they should ...all... be within design specifications.
As for opamps, the issue imo is not entirely sound qualities (unless really poor ones) some have minor electrical needs that can cause odd unexpected result when stuffed into a circuit not tailored to them.
IF capable of doing the adaptations?.. again Fill your Boots.
Significant issue is that they should ...all... be within design specifications.
As for opamps, the issue imo is not entirely sound qualities (unless really poor ones) some have minor electrical needs that can cause odd unexpected result when stuffed into a circuit not tailored to them.
IF capable of doing the adaptations?.. again Fill your Boots.
Yes I know Bare, wise advise, Thanks for that.
Off course I have no knowledge to choose the good swaps but answers above and rational short list is helpfull and good enough... As for PS transistors (have a BOM soom for Mouser...)
Here few money is involved: just 2 oap to buy for fun , have already the two others ref! Come back stays possible with no damage !
My major concern is to find two mono 5K pot ! as I need it I say to myself why not try an aop as I need to open the case and front panel !
I didn't know resitors could have a drift in the time... a myth is collapsing for me, believed it was the most resistant parts in electronic ! Btw once more it's very surprising how fews new caps at right positions after tests can improve a well born amp like this NAD !
Off course I have no knowledge to choose the good swaps but answers above and rational short list is helpfull and good enough... As for PS transistors (have a BOM soom for Mouser...)
Here few money is involved: just 2 oap to buy for fun , have already the two others ref! Come back stays possible with no damage !
My major concern is to find two mono 5K pot ! as I need it I say to myself why not try an aop as I need to open the case and front panel !
I didn't know resitors could have a drift in the time... a myth is collapsing for me, believed it was the most resistant parts in electronic ! Btw once more it's very surprising how fews new caps at right positions after tests can improve a well born amp like this NAD !
Hi, Eldam,
Better do not touch that JRC/NJM2043. I just finished some testing of Op.Amp alternatives for my Phono PreAmp Hack, and get amazed that one NJM2043MD is for almost -2dB quieter then my low cost favorite NJM2068 on test of noise spectral image with 50Omh terminated input and +60dB gain on 10-12V-DC bat.power.
I also measured that it have on +36dB a -3dB range up to 174kHz with amplification of 1kHz, 10mV input sin wave (phono cartridge input) and that is just 5kHz behind NJM2068 etc. Triangle shape input on +60dB from 3-5mV is linear up to ~6KHz.
For illustration only dual LT1028, OPA1611 are clearly better with -112.6 and -111.4dB vs its -107,5dB. Close to it is OPA2228 but after 5kHz NJM2043MD has noise level drop so at 20kHz it is better by ~-2..-3dB then OPA2228.
For comparation LM4562NA and LME49720 in the same test environment has pickup terrible harmonics from the ether, so in best case at 1kHz noise level they got is -102-103dB and NE5532AP has like -101..-102dB noise level.
All in all, I can tell you that old Chromium Dioxide Audio Cassette Tape from TDK has the best sound of anything that I ever heard on HiFi systems, but that is not technically and scientifically correct isn't it? Same mantra is with a Op.Amps on blogs, personal subjective biases, I for example have plenty of OPA2604,2134, NE5532/34... that I now do not even touch because in a real applications they tend to be (are) a mediocre in any way. Any application has its king of the hill favorite.
If you want to change it put something much better.
Best regards
dr Jovan I.
Better do not touch that JRC/NJM2043. I just finished some testing of Op.Amp alternatives for my Phono PreAmp Hack, and get amazed that one NJM2043MD is for almost -2dB quieter then my low cost favorite NJM2068 on test of noise spectral image with 50Omh terminated input and +60dB gain on 10-12V-DC bat.power.
I also measured that it have on +36dB a -3dB range up to 174kHz with amplification of 1kHz, 10mV input sin wave (phono cartridge input) and that is just 5kHz behind NJM2068 etc. Triangle shape input on +60dB from 3-5mV is linear up to ~6KHz.
For illustration only dual LT1028, OPA1611 are clearly better with -112.6 and -111.4dB vs its -107,5dB. Close to it is OPA2228 but after 5kHz NJM2043MD has noise level drop so at 20kHz it is better by ~-2..-3dB then OPA2228.
For comparation LM4562NA and LME49720 in the same test environment has pickup terrible harmonics from the ether, so in best case at 1kHz noise level they got is -102-103dB and NE5532AP has like -101..-102dB noise level.
All in all, I can tell you that old Chromium Dioxide Audio Cassette Tape from TDK has the best sound of anything that I ever heard on HiFi systems, but that is not technically and scientifically correct isn't it? Same mantra is with a Op.Amps on blogs, personal subjective biases, I for example have plenty of OPA2604,2134, NE5532/34... that I now do not even touch because in a real applications they tend to be (are) a mediocre in any way. Any application has its king of the hill favorite.
If you want to change it put something much better.
Best regards
dr Jovan I.
Attachments
Hi JovanEps,
I imagine you are modifying the phono section. I just got a nad 1600, with a very similar preamp section, and i want to improve it/modernize. For what you said, looks like there is very little value swapping the opamps. Guess that the next will be replacing all electrolotics and maybe the resistors in the opamps.
What about the phono stage, what have you done with it?
F.
I imagine you are modifying the phono section. I just got a nad 1600, with a very similar preamp section, and i want to improve it/modernize. For what you said, looks like there is very little value swapping the opamps. Guess that the next will be replacing all electrolotics and maybe the resistors in the opamps.
What about the phono stage, what have you done with it?
F.