1098 mods: very good result !!!!

[Iggurk]

Good dual AD825 module cost around 35$

Good dual OPA627 module cost up to 110$

That's more expensive than your 1.2$ part as you see

[voxy]

Yves.... I can't wait for your results. How are you gonna place them? All at the output or input?

[Iggurk]

Hope to receive them today or tomorrow.

I'll replace the two output non smd 2604 for front L/R, center & sub by dual op-amp AD825 module.

If result is good I'll try to change the input, but available space is limited due to the caps...

[voxy]

Hi Yves, I decided to try a newer opamp from NS LM4562. These are new ones design for audio application and highly raved in diy forum. Basically use them for inputs and buffers. After that I think I will tune the output opamps to my liking. :B

So your experience on the expensive ones are highly apprecited. All the best. :T

[Iggurk]

Hi Voxy, just ensure that the op-amp you order are dual and support a tension of ±18V.

Otherwise you need to buy an adaptor like that :

http://cimarrontechnology.com/index.asp?PageAction=VIEWPROD&ProdID=19

Regards
Yves

[voxy]

hi Yves

I thought the supply voltage is 10v? So any opamp that meets the 10V should be fine?
The LM4562 is +_17v, should be adequate, right?

[Iggurk]

Microfast told me it's ±18V, I didn't verify by myself.

The AD825 I've ordered have a wide voltage acceptance from 10 VDC to 36VDC so this should be no problem at all.

Still not received them, hope them to be here on Monday....

Found that over the web too:

http://www.rock-grotto.co.uk/opamp.htm

Regards
Yves

[voxy]

Hi Yves

I just downloaded the schematics for RSP1068....
Rotel definitely uses cheaper parts for this set.... NJM5532 for all inputs (though I consider the 5532 implementation is sonically more superior to the TL072 in RSP1098 ) and TL072 for all output. You are also right about 18V which is the standard operating voltage throughout the board. This really limit the number of opamps which can be use for direct substitution of the TL072. Luckily I have not order the NS opamps yet so I now plan to swap all the DSP boards TL072 with OPA2604 and the LRC channel output with dual OPA627.

[voxy]

Hi Yves

Just for your info, there is still one opamp in the main PCB board for bypass mode which I believe is a buffer opamp. You should also swap this TL072 out with a faster opamp.

For 1068 owners, the multichannel output uses crappy 5532 opamp... :M

[Iggurk]

Hi Voxy,

thanks for the info, where is that op-amp supposed to be located???

I still haven't received the new op-amps, hope they will at least arrive that week.

After around 100h of burn in the sound seems now better than right after the mod, less cold especially, perhaps I'm just used to the new sound, who know.

My friends where mitigated, they doesn't said anything bad, they found the sound scene quite large, detailed and natural sounding. But they cannot really compare to the sound differences.

One of the good point is that the listening position is less important than before, it's less disturbing if you're not exactly in the middle of the speakers.

[voxy]

Yves, I had attached part of the schematics. You can trace the opamps from the CD input (from the top of the diag.) to the array switch (big chip) to the "bypass" circuit into the opamp (think it is a buffer). If you need a bigger one, PM me. On the circuit board it also has a "bypass" word next to it. I think this one you should try with OP275.

[voxy]

For RSP1068 owners, after studying the circuit for 2 days and with my limited knowledge, this is how the chips are used for audio applications

all Line Inputs = NJM5532 (ok, should leave it but can use better NE5532 from BB)
Multichannel inputs = TL072 (strange and find it most cheapo, should use better OPA2604 or OP275 if you have a good collection of SACD or DVDA or you are using DVD DAC from movie playback) Bottomline... change
All pre-out = NJM5532 (it is ok but not optimise I feel. It would be better with OPA2604 or dual OPA627 but watch out for total current drawn)
all other opamps =TL072 (ok but I would use something better like OP275)

So whatever I had written previously was corrected in this post. Main audio board voltage is 18V (that is why I recommend only 2604).

[Iggurk]

Hello Voxy,

thanks for schema.

I only modify the multi input & output, and I don't think that there is more op-amp to change on my card.

Still haven't received anything from Ref Audio Mods

They will send me news parts if nothing received until Friday.

I'm also thinking of trying HDAM module like these one:

http://www.bursonaudio.com/Burson_HDAM_Module.htm

Is that kind of thing that is used on my SACD player instead of the traditional op-amp.

The only isue is the size...

[Iggurk]

I'm also thinking to try to solder a MKP cap between V+ and V- pins to improve power.

I've good caps of 0.1uF and 0.82uF in stock.

Does anybody think it's good idea or is it totally stupid?

[Iggurk]

Hi all!

I've received the op-amps from Ref Audio Mod today, and already fitted them.

Holly .... (can't write the word that start wit S and end with HIT on that forum I think...)

That sound totally amazing now, these 2604 are just junk op-amp.

The warm is back (ouf...), Diana Krall voice is more suave than she ever was, the sound scene is amazingly wide, everything is at the right place, lot of details, etc....

It's like if I've now a wall of front speakers, left and right are really difficult to distinguish, amazing, and the sound is also even better when you're not perfectly between the fronts.

Don't think twice, forget the cheap op-amps and directly for high end models with power regulation enhanced, they are clear winner.

Can't imagine that OPA627 or HDAM can sound even better, I'll change the input front op-amp by same model, then I'll stop the 1098 mods as the result is now far beyond that I could have expected.

Some pics of the output op-amps:





Yves

[Kevin D]

Yves,

What kind of camera are you using? Those are some amazing close-ups!

Kevin D.

[voxy]

Congrats... I am trying to get OPA627 :B . Did I see that you put it in the input stage?

[Iggurk]

Hello!

Input are still the 2604, soon replaced by same op-amps or by OPA627 with the adaptor I talked in a previous thread.

http://cimarrontechnology.com/index...WPROD&ProdID=19

Regarding the camera I'm using my good old Canon Powershot S45.

[voxy]

Hello!

Input are still the 2604, soon replaced by same op-amps or by OPA627 with the adaptor I talked in a previous thread.

http://cimarrontechnology.com/index...WPROD&ProdID=19

wow... :E

Just one question, looks like the ref mod's module is in DIP. Did you just solder them on the board ? The brown dog adaptor looks to be too tall for clearance between the boards.

in your opinion, how much improvement with ref to the stock unit?

[Iggurk]

The two output op-amps for fronts, center & sub are DIP8 socket on 1098, so for me it was a direct replacement.

If you only have SMD socket you need an adapter, or you can also solder wire between the board and the op-amp if there is not enough space.

The adapter is 0.410" x 0.500" x 0.062" (cm: 1.04x1.3x0.16), that must fit without any problem.

Added Value compared to stock unit? The sonic improvement is not empirically quantifiable...
it's a subjective assessment...but, to my ears, it's considerable !

[voxy]

thanks... so which one is the exact height of the adaptor? I am gonna put OPA627 for LRC... multichannel input and CD input with LM4562. All other LT072 & N5532 with 2604...

Change caps and voltage regulator in power supply.... lets see how it goes in 2 weeks.

[Iggurk]

Hi Voxy!

Can you update us regarding the status of your mods?

I'm still amazed the result I've got with these new dual op-amps AD825, I should receive the OPA627 for changing front input this week.

The height of the adaptor is 1.3cm.

regards
Yves

[voxy]

Hi Voxy!

Can you update us regarding the status of your mods?

I'm still amazed the result I've got with these new dual op-amps AD825, I should receive the OPA627 for changing front input this week.

The height of the adaptor is 1.3cm.

regards
Yves

Hi Yves... I am still waiting for parts to arrive. :M

Anyway, I recieved some advice from another forumer regarding changing the stock input/output coupling caps to Elna cerafine or film caps would also improve the sonic performance. You should try this only for the front channel and the cost is very low compare to your opamps. The only problem is space... BTW, do you happen to know what are those caps?

[McLoki]

Hello - I currently have an NAD T163 pre/pro and have been following your progress in swapping out the opamps in your rotel gear very closely.

I have purchased the service manual for my NAD and found that NAD uses all NJM5332 opamps in the T163. I have been thinking about replacing the opamps on the Pre-out (5 opamps) and DSP (6 opamps) boards.

The opamp I am considering using is the AD823.

One of the main issues that I have been having is that all the opamps in the NAD gear are SMT placement. (no socket) Would you recommend replacing the existing opamp with a socket adapter of some kind so I can test some different opamps or just solder in the replacement opamp as I am testing?

I am kind of heading into this blind but am very encouraged by the improvements that you have seen using the AD825 opamp. My system is about 90% home theater use and with the warm sound of the NAD combined with the warm sound of my speakers makes for a very laid back presentation of most movies. I am hoping to get more detail out of the high end (less laid back) as well as a better front and side stage (Steering) for home theater.

I believe that Iggurk only replaced 2 opamps on the pre-out side of his system so far (front Right/Left as well as Center/Sub) and has been very happy with the results. I was also going to go this route to start and decide from there if I like the sound of the AD823 or if I want to change back to stock or to something else.

I would appriciate any tips or recommendations that you can make to me as I undergo this project.

Thanks,

Michael

[voxy]

Hi Mike... looks like the Brits like NJM5532. :W

First, you need to check what is the supply voltage on your board before venturing further. Rotel uses +_18v which is pretty high and therefore a lot of easy to swap good opamps are not useable like OPA2132, LM4562. :M This left us with OPA2604, OP275 AD825 and OPA627 which could be use without problem. I would encourage you to try the AD825 since 99% of the user praise its sonic charecteristics. I did read about AD823 but the application is only low voltage headphone amps. For pre-amps, it will probably be fried because of the higher voltage.

Anyway if your supply voltage is below 17v, try LM4562. This is a new NS opamp design that rival Burr Brown and AD. I heard many good things about it though in some system, the AD825 still comes out top. As for IC socket adaptors, you need to get good ones because of contact issue with the cheap ones. First try it out in the front channel output with interchangeable DIP on SO8 smt adaptor. Try all those opamps mentioned and see which one you like best then get SMT versions and solder it to the board. Move it to the input and do the same again. Once tuned, buy S08 and swap those inputs/outputs that you use. The other caution is also total current drawn which may exceed those NJM5532 you had swap. The NJM5532 uses I think 10mA so if the replacement opamp uses a higher current, the board invevitably becomes hotter... the more you swap the more current is required and if your power supply is weak, you may find the sound become compressed and less dynamics and worst case your transformer lifespan shortens immediately.

Therefore I reckon you swap your inputs for CD/multi channel/ opamps and the analog channel outputs would give you the safest route to the mod. Leave the rest intact so that you do not tax the transformer too much. Change power supply caps (if they are crap) and input coupling caps (all swap with same values) of the opamps if you need further enhancements.

Lastly I believe the NAD also uses crappy opamps on the DSP board. You may want to change these if you use the pre-amp's DAC.

[McLoki]

Hi Mike... looks like the Brits like NJM5532. :W

Supposedly all the opamps in my NAD are NJM5532. (DSP - multi-channel and Pre-out.)

First, you need to check what is the supply voltage on your board before venturing further. Rotel uses +_18v which is pretty high and therefore a lot of easy to swap good opamps are not useable like OPA2132, LM4562. :M This left us with OPA2604, OP275 AD825 and OPA627 which could be use without problem. I would encourage you to try the AD825 since 99% of the user praise its sonic charecteristics. I did read about AD823 but the application is only low voltage headphone amps. For pre-amps, it will probably be fried because of the higher voltage.

The AD823 is rated for 1.5 - 18volts. My pre-out and DSP boards are 12volts. The output current is very similar between the two chips. (15ma for the 823 and 9ma(typical) - 16(max) for the 5532)

Anyway if your supply voltage is below 17v, try LM4562. This is a new NS opamp design that rival Burr Brown and AD. I heard many good things about it though in some system, the AD825 still comes out top.

I have already ordered the AD823, but I am trying to track down some LM4562 that I can use. The lm4562 sounds like a good chip, more designed for what I am trying to accomplish. If I can track some down - I may end up going that route.

As for IC socket adaptors, you need to get good ones because of contact issue with the cheap ones. First try it out in the front channel output with interchangeable DIP on SO8 smt adaptor. Try all those opamps mentioned and see which one you like best then get SMT versions and solder it to the board. Move it to the input and do the same again. Once tuned, buy S08 and swap those inputs/outputs that you use.

I am a little confused about the adapters. How do they connect to the board? If soldered in - why the need to remove them after testing to solder in the SMT part?

The other caution is also total current drawn which may exceed those NJM5532 you had swap. The NJM5532 uses I think 10mA so if the replacement opamp uses a higher current, the board invevitably becomes hotter... the more you swap the more current is required and if your power supply is weak, you may find the sound become compressed and less dynamics and worst case your transformer lifespan shortens immediately.

The LM4562 uses 10nA (typ) input current. (how does that relate to 10mA?) and the 823 uses 25pA (max) input current. (once again how does nA, pA and mA relate to each other?)

Lastly I believe the NAD also uses crappy opamps on the DSP board. You may want to change these if you use the pre-amp's DAC.

The schematic for the DSP board shows that it uses NJM4560 but the parts list for the DSP board shows NJM5532. I have not opened it up yet to see what is actually in there.

One interested thing for the Rotel 1066 users on the board. While I was researching OpAmps I came accross the service manual for the Rotel 1066. If anyone wants it, just drop me a PM with your e-mail address. (it is about 2.5 meg)

Thanks for all your help and I look forward to hearing your results.

Michael

[voxy]

If the supply voltage is 12v, go ahead with the AD823. But it seems a bit strange that the voltage is quite low for a pre amp. Check your main board voltage to be certain, they may be different if it is powered by seperate transformers.

The adaptors are for you to swap out the DIP ICs. Most people use this technique to do trial & error. You can also leave it there but it will be better (contact) to use back SMT ICs as intended by the designer.

If you look hard enough on OPAMPs tweaking in the net, there is one article relates to the operating current. Just make sure the IC you swap do not have a factor of 2x the existing current as it will draw twice the power. But I think you should not be overly worried if you are not going to swap every ICs out.

Assuming the DSP uses NJM 4560, the opamp to mod is those directly after the DSP (there should be 4 pcs of dual amp). You can keep these if you are only using them for movies. But for SACD digital inputs, the signal would go through the DSP and hence improving this part of the circuit should enhance the sonic performance as well. I suggest you mod this after you have tweak the analog input/output. THe current rating is pretty low (4.3mA) so a better replacement would be OP275 which uses 5mA and these opamps are also use in Krell's Showcase. I may also get these for the same application. They look good on paper and cheap as well for not so critical areas. Or simply use them for mass changes would also be fine.

[Tamas]

Hello, I would be interested in any thoughts regarding opa2134 op amps.

THX

Regards, Tom

[Habs4life]

Hello, I would be interested in any thoughts regarding opa2134 op amps.

THX

Regards, Tom

Im using the 2134's in my active crossover and can say they sound very good.They are detailed sounding without adding any high frequency edge and they are quiet.

[voxy]

Why use 2134 when 2132 cost slightly more with better performance. In a lot of tweak I read, most people claim the 2132 has better sonic qualities than 2134. The newer Anthem statement also uses 2132.

http://statement.anthemav.com/HTML/Products/D2/D2.html

Go for it.

[Iggurk]

Hi all!

I just modified the input op-amp for the fronts with a dual OPA627.



I'll wait some time for the new op-amp to burnin and I'll keep you informed of the global result.

Yves

[Iggurk]

Hello, I would be interested in any thoughts regarding opa2134 op amps.

THX
Regards, Tom

Take a look to the two links I already gave in the previous page:

http://www.rock-grotto.co.uk/opamp.htm

http://www.bursonaudio.com/Burson_HDAM_Module.htm

I've had a small listening session tonight with the new OPA627 installed, and the WOW factor seems to be here again.

AD825 and OPA627 are clear winnier to me, really forget about these poor cheap 2604, they sounds really poor compared to the two big brothers

Yves

[voxy]

Hi Yves... I am jealous. Somehow up till now, I only recieve the adaptors and the AD825 and OPA627 needs another 2 weeks. :M

Anyway pls keep me posted as I have excess ICs of 825 and 627 should they arrive and I am not sure if I should put the AD825 for all channel or use the OPA627 or a combo.... this is a tough decision. :B

[McLoki]

When you say the inputs for your OPA627 - what did you replace? (on what board)? It was your pre-out board that you put the AD825's on correct?

I got confirmation yesterday - my LM 4562's should be here next week. My AD823's arrived today, but I am going to try the 4562's first.

Michael.

BTW - I will let you know how things end up.

[voxy]

When you say the inputs for your OPA627 - what did you replace? (on what board)? It was your pre-out board that you put the AD825's on correct?

I got confirmation yesterday - my LM 4562's should be here next week. My AD823's arrived today, but I am going to try the 4562's first.

Michael.

BTW - I will let you know how things end up.

Well, I have not mod them yet... all talk no action.
Somehow, my parts take a longer while to appear bec they ran out of stock for those I request. I am not sure which one to put for input and out put. I have enough chips and adaptors should all the IC arrive.

Try the 4562 in the output before venturing the input. I am sure, it will outperform those crappy stock ones.

So I need Yves to advice which combo is the best... input with AD825 in + ouput OPA627 or all AD825 or all OPA627 or OPA627 in + AD825 out. This is a problem when you have excess chips...

[Iggurk]

Hello all!

I've only tried the following:

1) Original 1098

2) 2604 in & out (bad result for my ears)

3) 2604 in & AD825 out, much much better than full 2604.

4) OPA627 in & AD825 out, amazing result

I won't continue to test anything else, I'm pleased with the result.

I think that the OPA627 & AD825 are real winner, and they excell perhaps in different area, so the mix perhaps give you an average.

My final advice is to forget about the cheap op-amps, why replace the poor stoc model by less poor model? you will loose your money.
Go directly to op-amps that are reputed to be excellent.

The final result is far beyond my expectations, so I'm more than happy now.

And you guys? what are you waiting for modding :B

Where did you order your? It seems very slow.

Regards
Yves

[Iggurk]

Hi McLoki !

Perhaps it could be better if you open a dedicated thread for your NAD, what do you think?

I've changed the op-amps of the multi input/output board only.

Yves

[voxy]

Hi Yves

Great review. It will be OPA627 in and AD825 out for 3 front channel. Thanks a lot for sharing. Now I am thinking of getting more browndog adator if this operation is a success for the multi channel inputs.

I will probably use the spare 2604 for tuner and video in. Hopefully the parts arrive in 2 weeks time. :M

BTW, this thread was read like 2800 times but it only seems like only 3 of us talking. :B

[Iggurk]

Hello Voxy!

Still no news of your parts?

I'm still enjoying my mods, every time I insert a cd I'm amazed about the quality I now have.

The improvement in low bass is simply amazing, as well as the opening of the scene.

On some cd I thought that the lack of definition was due to bad recording, but I was so wrong, it was simply my old system that wasn't unable to resolve it, now it's near perfection.

Yves

[McLoki]

Great news - all chips are in. All in all I ended up with 11 AD823's and 6 LM4562's.

I spoke with the person doing the work for me out on the shop floor and we plan to do the work on Thursday of this week.

Right now I plan on replacing the fronts, Sub-Center, and all 4 surrounds on the pre-out board with the LM4562 chip. I will then reinstall the pre-out board and do some testing.

If I like the results, I will use the AD823 on the DSP board to replace the sub crossovers for the fronts, center/sub, and surrounds.

the second stage (with the AD823) will take place in the coming weeks. I will spend at least a week with just the pre-out board upgraded and decide how much I like the results from there.

I will report in over the weekend and let you all know how the results went.

Michael

[Iggurk]

Hi Michael!

Don't forget to inform us about the result

With some pictures of the mods of course

Still no news from your parts Voxy?

Yves

[McLoki]

Well got the chips replaced for me today. I have not had much time to test it well yet. (wife and kids were home and they are not demo friendly.. )

Initial impressions:
1) Maybe a little better steering, but to be honest not much.

2) Seem to get much better low level details so far. More clear and neutral than before. I would not call it bright at all (very detailed though) but not as laid back as it was either.

3) Much louder than before more in line (volume wise) with my AVR when it was used as a pre-amp. Will need to recalibrate my system tomorrow.

So far, I am very happy with the results. It has made the NAD the more of the upgrade I was hoping for when I purchased it. I think it mates much better with the LSi's now. I have not done anything with the DSP board, I am happy enough with the results, I do not feel like I need to. I do have the chips though, so we will see in the coming weeks.

I have not done alot of testing yet, but I will report back to give more in depth results once I do.

Michael

[Iggurk]

Hi Michael!

Good to see that you enjoy the mod result

Did you find time to do more tests?


And Voxy, did you finally received your op-amps?

Yves

[voxy]

Hi Michael!

Good to see that you enjoy the mod result

Did you find time to do more tests?


And Voxy, did you finally received your op-amps?

Yves

Hi Yves, just recieved all but the OPA627 are of wrong package. :rofl:

I think will try all AD825 first... 8)

[McLoki]

Hi Michael!

Good to see that you enjoy the mod result

Did you find time to do more tests?

Still not a full review - but thought I would give you all a quick update.

The opamps that I used are truely incredible. The level of detail I have now is huge. I notice small details that I could not hear before, also more sounds seem to be made up of a bunch of small sounds rather than 1 big one. (think of a mosaic painting - I just took a few steps closer to it so I can see the inividual strokes rather than just seeing the entire finished picture.)

One down side to the level of detail that I am geting now is that I notice anytime the soundman slips and lets any sound in a movie distort. Basically the problems come through just as clearly as the other sounds. They actually draw more attention to themselves, since the problems just sound wrong as opposed to part of the scene. Based on this - I do not plan to mod further for fear of it becoming "to much of a good thing". I am about 90% home theater / 10% music listening)

My speakers are certainly up to the challenge of the new preamp and I am very happy with the results of this mod and how well it allows the NAD to work with the rest of my system.

Many of the issues I had with the overly laid back sound of my system seem to have been resolved with this mod. Thank all of you for your help and suggestions.

Michael