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Marantz MA500 thread

Yesterday I did an interesting test.
I finally got one of my Denon POA 6600 amps working and gave it it's first sound check in the left channel of the system.
DSC02520.JPG
The pair of MA500's in the right channel played considerably louder than the Denon, I had to adjust the balance about 2.5 points to the left to center vocals etc.
And the MA500 side had more prominent mids.

This got me to thinking about the op-amp swap. It will be interesting if there is much of a change, or any at all. The 49720's are some very nice clean sounding parts normally.

Cheers,
James
 
So I am almost at a loss for words.

Normally, if I have to ask myself if a change to some part of the system sounds better then I think that the answer is normally no. I mean, if I have to search to see if it sounds better then most likely there has not been a noticeable improvement.

This is the exact opposite. Changing the op-amps resulted in an immediate, positive and visceral change for the better.
Better highs, cleaner and tighter overall sound, even kick drums are more tight. I am very pleasantly surprised.

Someone please correct me if I am wrong. But I am thinking that being inverted each amp is producing a half wave in bridged mode. So I am making the WAG that if the op-amp has a faster slew rate then perhaps the amps are better in phase with each other?

In any case the sound is overall better, cleaner and more enjoyable. And I liked the sound that I was getting before. It's just better now.

Cheers,
James
 
rickl said:
Thanks for the update. I'm running njm2068dd in my C2. I might try these.
Click to expand...

Before sitting down to listen I was wondering if I would hear a difference at all. Before the first song was over I was grinning. The difference was unmistakable.

I have always liked the 49720 and have used them in a lot of CD players. But I am glad that I tried the 2068 first, just for the experience. The 2068 is very polite and was a nice upgrade from the 4558. The 49720 is in another class entirely. I didn't want to stop listening but Wife still has to work so at some point things have to get quiet.

Cheers,
James
 
Reviving this thread!
First time reading through this and it motivated me to pop on a pair of these MA-500s that I got on ebay for a good deal. One is supposedly in good working order and the other is triggering the protection circuit when the volume is turned up. My plan was to originally buy just one of these since Im going to use it for my center channel, but since I got a good deal I figured Id connect the working one while I recap and hopefully fix the other, than swap in and do the same for the working one. might need a third at some point and use these on my rears and center!

@Bratwurst7s just wanted to thank you for documenting this! Question for you...Did you happen to compile your list of what was replaced and where you sourced? I know you notated what you used throughout the threads, but was hoping a noobie can cheat and get a compiled parts list for ease of ordering. Maybe we can create a document to share with others that want to perform this.

This will be my first amp recap project and give me confidence to dive into a few others I want to do in the future!
 
Designguy said:
Reviving this thread!
First time reading through this and it motivated me to pop on a pair of these MA-500s that I got on ebay for a good deal. One is supposedly in good working order and the other is triggering the protection circuit when the volume is turned up. My plan was to originally buy just one of these since Im going to use it for my center channel, but since I got a good deal I figured Id connect the working one while I recap and hopefully fix the other, than swap in and do the same for the working one. might need a third at some point and use these on my rears and center!

@Bratwurst7s just wanted to thank you for documenting this! Question for you...Did you happen to compile your list of what was replaced and where you sourced? I know you notated what you used throughout the threads, but was hoping a noobie can cheat and get a compiled parts list for ease of ordering. Maybe we can create a document to share with others that want to perform this.

This will be my first amp recap project and give me confidence to dive into a few others I want to do in the future!
Click to expand...
Hi DG,

No, I never did make a replacement component spreadsheet. I used to do that extensively but a couple of factors led to me giving up on it.
One, I didn't get much of any kind of feedback that they were ever being used by other members, and Two, most of the time when I revisited them myself a year or two later many of the components were no longer being sold so I had to look them up again anyway.

I may have paper notes that I could scan for you. Getting late here right now but I'll try to remember to look tomorrow. If I forget (retired old guy here) please feel free to remind me.

They are really nice little amps better than I expected. I still have 5.5 of them sitting here. Unused now that I have my Denon monoblocks working.

:beerchug:,
James
 
Wow! was not expecting such quick reply. Understandable on why you didnt keep up on a list. If you can scan those that would be great, but no worries if not, there is a lot of info already in these threads.

Thanks again!
 
Designguy said:
Wow! was not expecting such quick reply. Understandable on why you didnt keep up on a list. If you can scan those that would be great, but no worries if not, there is a lot of info already in these threads.

Thanks again!
Click to expand...
OK, I found my notes. I can say that I probably won't get them scanned today, but they are on my desk as a reminder.

The notes are fairly rudimentary and you will probably find that it will be easier to just go through the thread and make your own notes, or, do as I sometimes do and take screenshots of the useful posts, save them as JPG's and print them. That would probably be your quickest and easiest path forward.

Last summer my brother-in-law picked up a parts unit for me and when I was over in Arizona last September I brought it home in my suitcase minus the transformer. So sometime this year I will be pulling the main PCB from it and using it to replace that broken one that I repaired in my first unit.

:beerchug:,
James
 
Ok sounds good. Couple of things I need to learn about is how to do the light bulb test? and properly adjusting the bias. I got the service manual downloaded. The amps should be here today so I'll get to really see what Im working with. Supposedly these were "serviced in 2015", if they really were, hopefully they werent hacks like the first one you had to deal with!

Also, one question...just to verify, you had to do your cage modification, and hole drilling to make more room for the caps due to the smaller caps(same as original) not being available, or was this for sound quality improvement... I should anticipate needing to do this part as well?
 
Designguy said:
Ok sounds good. Couple of things I need to learn about is how to do the light bulb test? and properly adjusting the bias. I got the service manual downloaded. The amps should be here today so I'll get to really see what Im working with. Supposedly these were "serviced in 2015", if they really were, hopefully they werent hacks like the first one you had to deal with!

Also, one question...just to verify, you had to do your cage modification, and hole drilling to make more room for the caps due to the smaller caps(same as original) not being available, or was this for sound quality improvement... I should anticipate needing to do this part as well?
Click to expand...

The dim bulb tester is a very simple and useful item. In principal you are just putting a lightbulb in series with the device under test, and it limits how much current it can draw, thus keeping it from drawing so much current that parts burn up if something is damaged. But the voltage stays close to what it should be, letting you test while still protecting the device from more damage.

Use the search function to look for DBT and you will find better explanations and instructions on how to build one, which is pretty easy.

Setting the bias is pretty easy, you just have to follow the directions in the SM. The original single turn pots can be pretty touchy to adjust, one of the reasons that I replaced the pots with 25 turn ones. The second reason is that those open frame pots tend to oxidize over time and can cause problems. Vishay and Bourns trim pots are nice little things.

Re the main filter cap replacement, it will be hard to find 10,000µF caps in 30mm diameter in the correct voltage. I couldn't. You can go up in voltage (and there are reasons to do so), but you can't go down. 35mm was all that I could find, and that diameter causes space problems, hence the offset of the upper cap and the cutting of the frame, to make space without anything pressing on the caps and causing strain on the PCB.

Going up in capacitance for those filter caps can be an advantage if you don't go crazy. First, a lot of caps are being produced on the low end of the tolerance to save money, so the 10,000µF cap that you buy might actually be only 9,000µF, which sucks. And they will lose some value over time, especially if they are under a lot of heat. So it pays to buy 12,000µF, and in reality the ones that I bought tested at about 11,000µF.

:beerchug:,
James
 
OK, for what they are worth here are my notes. And I don't think that they are worth all that much. In many ways this thread is my notes. I cheated and took photos rather than scan them but they seem to be legible within the limits of my writing.

DSC03494a.jpgDSC03495a.jpgDSC03496a.jpg
:beerchug:
 
Thanks for uploading the photos of your notes! Ill see what I can get from them. I received the amps over the weekend and as expected, one seems to be working ok and this one, cuts the sound in and out when you turn the volume up a bit. There is a little bulging on the caps, not sure if these were replaced at some point, the only thing i noticed when I took it apart were the zip ties that hold the transformer wires to this board were nice and white compared to the rest.
20250127_133158.jpg
20250127_133133.jpg20250127_133239.jpg20250127_133026.jpg
 
Bratwurst7s said:
One of my amps had those same caps also. The bulging thing would scare me.
Did you test them after removal? It would be interesting to know how badly degraded they were.

:beerchug:,
James
Click to expand...
i'm sure i did but it was too long ago to remember... but 9 out of 10 times, when i have tested bulging caps in the past, they tested within spec. that would have only been testing with a mini component tester so not real world results. i doubt i would have tested them for leakage on my sprague to4 back then.
 
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