Modding my Old Mixer

[lrichner]

Hey guys,

I am new to this board and somewhat to modding (not engineering though.)

Now, I found this old and crappy Samson MDR10 mixer and an idea sparked in my head. I want to switch the 4580 JRC op-amps to NE5532s and that’s not a problem. What i’d like to do is mod the EQ to sound and perform better. What modifications could I do to enhance an EQ section?
I’m painting the chassis and pretty much redoing this small console.

Thanks,

Louis

 

[pacificblue]

Without knowing what exactly is inside it is hard to tell you what to improve. The usual suspects are power supplies, potentiometers, switches, connectors.
Replacing op amps with others is usually only useful, if you adapt the surrounding circuit accordingly.

What is it exactly that annoys you about the sound?

 

[Mooly]

If you want to experiment with opamps perhaps fit sockets and try the NE5532 and also some less obvious ones such as TL072 (really) and if you like those then try something like the OPA2604. The LM4562 is the successor to the NE5532.

 

[geraldfryjr]

I did that to my fostex 450 mixer and it sounded great!

It was quite a job,it was.

I had to first clip the old chips out ,then yank each pin out and clean each hole seperately inorder to not destroy the board.
And then I installed sockets for all 32 (aprox) of them.

Tedious but it was well worth the effort as it was marginaly worth recording with stock.

I tried both the TL072 and NE5532.
The NE5532 would not work properly in the filter sections as they turned into oscillators for some reason,but they worked fine in the line sections.

So I just stuck with the TL072 throughout the board and the sound was transparent and had no noise.

Seriousley,It rivaled my mackie 32-8 in an a/b comparison.

I just read on a pro recording forum that the OPA2604 was the best to date for audio,but,I personaly don't have any experience with that opamp yet.

I hope this helps you. jer

 

[geraldfryjr]

What exactly are you wanting to do to the filters?
As their center frequencies are where they should be musicaly.
Except that the midrange could be shifted up a bit IMHO.
That could probably be done with a simple resistor change.
Do you have the scematic? jer

 

[lrichner]

Thanks guys,

I don’t have the schematics yet, but i’ve taken it apart and studied it. I’m trying to learn as much as I can of the board for now, so thanks. I might go with the OPA2604 or the NE5532. I’m used to recording and mixing on Neves and SSLs, so when I found this old mixer I decided to give it a new engine if you get what I mean.
It’s a small project, just 10 channels, so it shouldn’t be too hard.

So what you guys are saying is that if just by replacing the op-amps, the whole board would sound that much better? EQs, Filters, Inputs, etc?

 

[simon7000]

Thanks guys,

I don’t have the schematics yet, but i’ve taken it apart and studied it. I’m trying to learn as much as I can of the board for now, so thanks. I might go with the OPA2604 or the NE5532. I’m used to recording and mixing on Neves and SSLs, so when I found this old mixer I decided to give it a new engine if you get what I mean.
It’s a small project, just 10 channels, so it shouldn’t be too hard.

So what you guys are saying is that if just by replacing the op-amps, the whole board would sound that much better? EQs, Filters, Inputs, etc?

LM4562 Input Preamp
TL072 Filter section
LM4562 Output Stages

5532 might not work in preamp and will oscillate in the filter section.

Change any electrolytic capacitors to film types where possible, but absolutely replace the input pair at each mic preamp.

 

[geraldfryjr]

Oh yes very much so.

Very good advice on the caps.

In my a/b comparison the one thing that didn't let it top the mackie was a very slight lack of punch on the low end with precussive instruments but it was only noticeable because of the comparison test.

Otherwise it was perfect.

And my guess is that it was due to the caps.

But I didn't get a chance to try different ones and I don't have that board anymore. jer

 

[nigelwright7557]

Old mixers usually have scratchy pots, so that would be my first point of attack.

 

[Mooly]

Also, if there are a lot of opamps remember that the current requirements add up so check the data sheets and make sure it all falls within the supply capability.

Twenty 4558's will run happily from a 78L12 79L12 supply, twenty NE5532's will not.

The OPA2604 is a personal favourite, particularly in CD player output stages or I/V conversion from a DAC.

 

[simon7000]

Old mixers usually have scratchy pots, so that would be my first point of attack.

Not too long ago I rebuilt a Yamaha PM3000-48. Using Caig DeOxit products. They make cleaners and lubricants for conductive plastic pots and different chemicals for the switches. Worked well except I forgot to clean the input gain trim pots as they seemed to be working. Turned out the the standard microphone used was an SM58 so at the right trim position for them the pots were really worn. Twisted around they worked fine in the shop but three months later problems showed up.

 

[geraldfryjr]

Good point ,Mooly.
IMHO, I would stick with a good bifet and/or the new standard, the OPA2604.
There a lots of intense discussions about replacing opamps with a NE5532 but in my example it simply did not work properly. jer

 

[lrichner]

Thanks a lot guys, I really appreciate it. You helped a lot!
I’m going to start shopping for my op-amps. Any legitimate website suggestions?

 

[geraldfryjr]

Jamecco and Digikey are two good company's. jer

 

[Mooly]

Depends on your location...

 

[lrichner]

Depends on your location...

Florida, United States. I looked into the previous poster’s websites and looked great.

 

[geraldfryjr]

Well,it was what I could come up with since I didn't know where you are located.
I guess I should have asked first, Cheers. jer

 

[jon68z]

Hi,

Take a look at Future Electronics, ( Electronic Components from the Best - Future Electronics ). I just ordered some parts from them and they had a great turn around time and fair prices IMHO. They had a good selection of Op Amps, (I bought some LM4562s from them along with some LME49710/20s) with several package options (DIP and SOIC when available). Great service as far as I am concerned (was my first purchase). As some on mentioned earlier, Jameco has a fair amount of National Semi Op Amps but is not the best in package selection IMHO.

Hope it helps,

Jon