Vintage Yamaha 1204 Mixer Opamp upgrade

[ReRibbon]

A buddy gifted to me an old Yamaha MC1204 mixer. It works. It sounds cool. Is a little loose on the low end.
Is running JRC 4558DV opamps all over the place. It has 12 channels and I wanted to mod a few of them to be a little tighter sounding.

Any suggestions for a direct swap for these JRC4558DV's?

Thanks in advance.

 

[JohnRoberts]

A buddy gifted to me an old Yamaha MC1204 mixer. It works. It sounds cool. Is a little loose on the low end.
Is running JRC 4558DV opamps all over the place. It has 12 channels and I wanted to mod a few of them to be a little tighter sounding.

Any suggestions for a direct swap for these JRC4558DV's?

Thanks in advance.

If it's a nominal 0VU=-10dBV then 4558s are probably fast enough...

If you want to make op amp swap upgrades, maybe benchmark before and after performance with some bench tests.

Or not...

JR

 

[ReRibbon]

It seems to be +4. I base that on the aspect that my interface Digi 002 BLA Modded is set to +4 and when I use the Yamaha for a pre (and with the gain input turned all the way down on the 002), the channel gain from the Yamaha translates equally as if I was using any other +4 preamp or the stock 002 pres. Maybe a variable that would negate that statement is that my inputs are set to +4 vs. -10 on the 002. Either way, the Yamaha translates if not equally, very very similarly.

 

[rock soderstrom]

I also have a Yamaha MC1604 version 1 in my music room at home. It's fine for mixing my instruments to quickly sketch out some ideas or jam around. I like the oldskool user interface and find the console very ergonomic for my modest purposes at home.

I've also been wanting to change or mod a few things on the mixer for a long time. Unfortunately, I'm not the mixing console expert and have so far preferred other DIY projects in terms of time...

From my point of view it would make sense to upgrade the summing amps or the master bus first, I expect the most from it.

It would also be cool to adjust the routing a bit, since you always have to route via the subbuses to the stereo bus. I would like to change that.

It's obvious that a few modern ops and passive components don't make a Neve console out of this lowbudget mixer, but it would be interesting to make the sound a bit more broadband and punchier.

Any ideas besides buying a better console?

Schematic here:


https://groupdiy.com/index.php?topic=74471.msg943692#msg943692

 

[jensenmann]

If the lowend sounds loose then I guess the coupling caps are the problem, not so much the chips. There are many coupling caps between parts of the circuits which all together form a highpass filter. With age these electrolytics lose capacity hence the -3dB point of the HPF rises. That could be what you´re describing as loose lowend. The cure would be a recap. And while you´re at it you could increase these coupling caps e.g. x2. That will give you another octave below the original -3dB point. Swapping chips will change only little w.r.t. the highpass filter.

Besides that recapping makes more of a difference sonically than any other mod. And new electrolytics are a lot less leaky than old ones, which helps to prevent pots to get scratchy and switching noise.

 

[abbey road d enfer]

To add to Jensenmann, indeed new capacitors are much better than those made 40 years ago, not only because they are new, but also because the have lower ESR, which is quite noticeable for decoupling caps (those across the supply rails),(not so much for coupling caps (those that pass signal). Be sure to use 105° type, which are more durable.
New 'lytics are also less bulky, which is a good point regarding stray capacitance.
And increasing the value minimizes LF distortion, as the voltage is inverse-dependant on capacitance.
As this is likely to bring the overall LF cut-off in subsonic regions, it is necessary to make sure it is defined at one point, if possible early in the signal path, using a good film capacitor.
Not always easy in an existing product, though...

 

[analogguru]

..... new capacitors are much better than those made 40 years ago, not only because they are new, but also because the have lower ESR,.....

I wouldn't be so convinced - here is the proof of the opposite:

 

[rock soderstrom]

I wouldn't be so convinced - here is the proof of the opposite:

I will give it a try. FYI, this mixer series was equipped with high quality Nichicon capacitors, but they get old too....

 

[scott2000]

I wouldn't be so convinced - here is the proof of the opposite:

Those things any good for ESR testing?? I had a similar thing years ago and never really trusted it...

On that note....This was kinda interesting...although he had issues with some results in another video iirc and I can't remember if he ever figured out some better method to decipher certain results...

https://www.youtube.com/watch?v=VdF7iwWvgPA&t=0s

 

[analogguru]

Those things any good for ESR testing??

At least for relative ESR between two electrolytics.....

 

[JohnRoberts]

Measure twice cut once...

Start by measuring frequency response of individual channels looking for outliers. Common symptom from old tired electrolytic caps is weak LF response. If you identify any bad caps, replace all of the same value caps as they are likely from the same production batch and suspect to fail like the others.

The 4558 is a widely used (cheap) general purpose op amp. You can certainly do better on paper substituting modern op amps and perhaps worth it for the bus summing amps. Wholesale op amp upgrades could exceed PS current output.

Measure twice, cut once.

JR

 

[radardoug]

And the very important takeaway from John? MEASURE!!!

 

[abbey road d enfer]

I wouldn't be so convinced - here is the proof of the opposite:

I'm not convinced of the statistical value of your test. My opinion is based on having to replace many electrolytic caps over a few decades.

 

[Gold]

I'm not convinced of the statistical value of your test. My opinion is based on having to replace many electrolytic caps over a few decades.

From a practical standpoint if you are restoring an old piece of equipment with a zillion electrolytic caps it's easier and faster to just replace all of them. When I restore lathe electronics that's what I do. When I got my Telefunken M15 tape deck I wanted to hear what it sounded like stock before changing anything. I didn't do that work but Bob Shuster went through the audio cards and only replaced what was out of spec. That was only four audio cards though. If it was a multitrack I wouldn't have tortured him like that. Recently I've noticed the range on the low end sometimes can't make it up to calibration. Might be time to finally change the electrolytics. Most of them were good. A lot of the tantalum's were no good. Those were replaced with Tantalum. I love the sound if this deck so don't want to screw with it too much.

 

[abbey road d enfer]

Going back to the subject of opamps, JRC/NJM2068 is a good contender. As JR mentioned, one has to take into account it draws 5mA instead of 2.5. It is also often necessary to increase power rails decoupling.

 

[analogguru]

I'm not convinced of the statistical value of your test. My opinion is based on having to replace many electrolytic caps over a few decades.

Ok, feel free to name the value of the - vintage - electrolytic, used/unused and the number of pieces and I will present you the test results - vintage electrolytics are not always bad only because they are old.

Of course in such an idiotic case as shown below you will probably be not wrong to assume that the electrolytic is bad - as if there would be no other place for it.

Going back to the subject of opamps, JRC/NJM2068 is a good contender.

You could also choose the NJM4562 with the same current consumption as the 4558 but better performance.

 

[abbey road d enfer]

Ok, feel free to name the value of the - vintage - electrolytic, used/unused and the number of pieces and I will present you the test results - vintage electrolytics are not always bad only because they are old.

I haven't made a log of all the electronic components I have replaced over the years, but I know that electrolytic caps come a close second to transistors.

Of course in such an idiotic case as shown below you will probably be not wrong to assume that the electrolytic is bad - as if there would be no other place for it.

I must be thick, but I don't get it...
Language barrier, perhaps...?

You could also choose the NJM4562 with the same current consumption as the 4558 but better performance.

IIRC the 4562 is not compensated for unity-gain...Would be good for summing amps and maybe mic pre, but not for tone controls and to be discussed for post-fader amp.

 

[emrr]

I haven't collected much data yet, but have suspected I see a trend of brand new electrolytics improving their ESR reading somewhat once used a bit.  Certainly seems that way with things I've briefly installed for testing, then pulled after a bit of use. 

I definitely see new old stock caps showing higher ESR than the new equivalents, neither yet used. 

 

[analogguru]

.... I must be thick, but I don't get it...
Language barrier, perhaps...?....

So if you have a closer look at the highlighted area you will see a 47uF electrolytic cap beside an 15k power-resistor which gets hot during use - sometimes both even touching each other.  You can be sure that this electrolytic will be dried out with time.  Even if you leave the 47uF in place and bend it above R10, R11 it would be better (and a cure).

And here we have a 100uF/63V FRAKO electrolytic cap produced in 1978 and as can be seen, heavily used in a computer board (from Kienzle).  You can see the values for yourself now 42 years later:

And BTW: yes I measured all three capacitors with similar values - there were not more.

 

[analogguru]

IIRC the 4562 is not compensated for unity-gain...Would be good for summing amps and maybe mic pre, but not for tone controls and to be discussed for post-fader amp.

Then the NJM4560 is your choice, but better noise (and slew rate) performance are only relevant when there IS some gain.