Modding a Pre/Pro.

[GV#27]

I guess you could , just be sure you can do it if you do have problems.

[McLoki]

stupid question - but what voltage is running on the pre-out and DSP board into the opamp? I had thought it was 12v, but just wanted to be sure.

I also took the advice to talk to the people on the rotel forum who are modding their preamps and you can read what they have to say (if interested) here....

As always - thanks for your help and time.

Michael

[GV#27]

Yes both boards are 12 volts.
Your very welcome.

[McLoki]

Did you have any opinions one way or the other on which to try to replace the 5532's with? AD823 or LM4562.

The AD823 should be here on Monday. The LM4562 is not in stock and I am unsure if I will be able to source them or not. Just wondering if you thought it was worth waiting and not using the AD823?

Michael

[GV#27]

I have not used either but the LM 4562 looks like a great part and would probably be my choice of the two.I want to try them in an active crossover I am building but I think it is a bit pricey.( unless you are getting free samples).The AD823 should also work well, though it is impossible to say what the sonic differences will be between them.

[McLoki]

I will be getting in 11 of the AD823 and only using about 7 of them (based on the opamps you are suggesting I replace). You are welcome to the ones that I do not use.

If I am able to get in the 4562 I will use those instead. I hope to know if they can be sourced by Monday when the 823's arrive.

And yes - working for an electronics firm does have some perks. They are free samples... :)

Michael

[GV#27]

You are welcome to the ones that I do not use.


And yes - working for an electronics firm does have some perks. They are free samples... :)

Michael

Thanks for the offer but I need DIP packages.

I figured you were getting some freebies.:)

Good luck on your mods and keep us posted.

[GV#27]

I will be getting in 11 of the AD823 and only using about 7 of them (based on the opamps you are suggesting I replace).

hummm, I think I only suggested 4 actual IC's,U608,U613,U1O11and U1013.But seeing as they are free..

[McLoki]

The opamps that I would recommend changing are U609 and U612 on the pre out board and U1011 and U1013 on the DSP board .:)

I am an idiot - I read your recommendation as U609 through U612 and u1011 through u1013. On the pre-out board that would be the front, side, rear and center/sub. On the DSP board - I do not know what any of them are for. (speaking of which - what are they for? :) )

Michael

[GV#27]

on the DSP board - I do not know what any of them are for. (speaking of which - what are they for? :) )

Michael

On the DSP board U1011 is the front left and right,the U1013 is the center and sub.Both chips function as low pass filters/buffers at the outputs CS4228 codec chip.

[McLoki]

Confirmation today - all chips (LM 4562) should be sent out this week and I should get them by end of week next week.

Also saw a really cool SMT part removal device on our shop floor today. Looks kind of like a standard pen soldering iron with the tip removed, but blows hot air. It is used to remove SMT parts as it can heat/melt the solder on all the legs at the same time by waving the iron above the part. Once heated the part is just lifted off. Apparently it is really hot air (variable heat) as it can also burn a hole through the circuit board if used improperly.

Just thought it was cool. (part can then be reused or replaced if needed)

Michael

[MillerLiteScott]

Do you have a link to the tool?

[GV#27]

Confirmation today - all chips (LM 4562) should be sent out this week and I should get them by end of week next week.

Michael

Awesome:)

It sure is nice to have the proper solder/desolder equipment when working with SMD.

[McLoki]

Do you have a link to the tool?

It is a Hakko 850. Here is a link with a pic and a short description. (also with links to the manual and manufacturers website.)

We have 4 of 5 of them on the shop floor and apparently they work very well. (for part removal, not placement - although from talking to the people on the floor using the equipment, it can be used for placement as well)

Michael

Edit - here are some on the bay - not as expensive as I thought they would be used. THe nozzle that I saw looked more like the A1130 or A1170. The different nozzles are for different SMT parts so you can heat all the contacts without moving the tool around.

[McLoki]

I can't seem to find any local bypass caps near the opamps which is very odd.If you put in a faster opamp like the 823 it may oscillate with out them.
A nice touch though is that the pre outputs are driven by a discrete opamp.:)

Just so I am clear - what should I listen for to determine if the faster opamp is oscillating? What will it sound like or what will happen so I will know?

Michael

[GV#27]

Depends,You may not hear anything obvious ,or you may find the treble to be somewhat harsh sounding.It could also cause problems with your amps bias circuit.Monitor your amp to be sure that it is not getting excessively hot when the moodded pre is hooked up to it.
To properly diagnose an oscillation you really need to hook it up to an oscilloscope and check the power supply pins and the outputs of each LM4562.

[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

[McLoki]

Chips are replaced. I took a bunch of pics that I will post later. I have to head home and get her all hooked back up. Can't wait to see if it makes a difference or not.

(chips replaced were the chips for all channels on the pre-out board. njm5532 were replaced with LM4562's)

I also verified that the dsp board does use the njm5532 opamps.

I will be able to reuse the NJM5532's if I need to.

Michael

[McLoki]

Here are the pics....

1. Start - the NAD T163
2. Cover off
3. Boards out ready to have the opamps replaced. (had to remove 2 boards even though only one was getting 4 new opamps.)
4. My coworker Tim. He does this all day and after finishing an 8 hour shift, stuck around for another 1/2 hour to do this for me. Thanks Tim - he did a great job. (although the blue circuit board did throw him a little.) BTW - those 3 dots by his left knuckle are 3 of the chips that he placed. Pretty small and 8 legs. I would not have tried it on my own.
5. Work is done, boards are back in - just have to put the top back on.

Initial impressions.

• Maybe a little better steering, but to be honest not much.
• 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.
• 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 start a new thread to give more in depth results once I do.

Michael

[GV#27]

Great stuff Im glad that the mod was a success.

[McLoki]

Great stuff Im glad that the mod was a success.

Would have been much more difficult without your help. Thank you for both the help and support along the way.

Michael

[Ferres]

Great news! I'll definitely considering modding my pre-pro first before I think of going into any new purchase.

[McLoki]

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".

The LSi's 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.

I will definately plan to bring this to the chicago fest this spring/summer and let you all take a listen to it. I look forward to others opinions of it especially those who have heard a NAD (pre or AVR) with the LSI's before.

Michael

[GV#27]

It's good to see that all that money it cost you for those op-amps is paying off.:D

[nmartinezs]

I have the .pdf file of the service manual that I would be glad to e-mail you (it is 10 meg in size). The schematic of the DSP on a normal 8.5x11 sheet of paper is so small it is useless.

PM me your e-mail address and I would love to have you take a look for me.

Thanks,

Michael

Hello, please e-mail me the service manual to nmartinez@initel.com.mx, thank you in advance.

[McLoki]

Sorry the modification to the 163 is complete. As for a first post to ask for the service manual - I will respond with I purchased mine off of e-bay for about $15.00. (was a .pdf file that I downloaded so no shipping)

Stick around and contribute some. Let us know what your equipment is and what your goals are.

Other than that - for now - welcome to club polk.

Michael

[GV#27]

Hi Michael,after a few months of listening are you still happy with the mod's?

[McLoki]

Love the mods, but now that I am used to the sound - I want more. I have changed jobs so I will have to actually purchase the parts this time :) but I am still thinking about taking it to the next level.

I have decided that the sound man does not slip that often and if I can get more resolution - why not go for it.

I think I will replace the remaining opamps (channel opamps anyway) on both the DSP and 7.1 input board. I am not using the 7.1 board right now, but with the cost of shipping - it will not add greatly to the cost to have them all done...

I will let you know how it goes when I do the replacement. Right now - the budget is going to non-audio things. (house and vehicle maint.)

Michael

[GV#27]

Love the mods, but now that I am used to the sound - I want more.

Michael

Sounds like you may have a bad case of upraditis.:)

[McLoki]

Not that bad - but I do like the sound I get and wonder how much better it can become. Like I said - I do not have much of an audio budget right now due to other family issues, but I am pretty sure I can upgrade the rest of my opamps for under $100 installed. That makes it one of the cheapest (and possibly next) upgrades I can do.

If I end up going for it, I will let you know.

Michael