Mysterious mixing console

[Harvey Birdman]

Very impressive magazine project.
I'm 73 and have been building projects from magazines since I was about 15 and I must say that I've never seen a mixer project as well documented as this one, (mind you I don't read German unfortunately, just basing my comments on the schematics and BOM).

This could be the basis for a DIY analog console project of any size as it's easily configurable from a simple 4 in 2 out mixer to something of the scale that qspart has acquired. Most of the components are still available and there's nothing wrong with a mixer based on 5534/5532 technology. Could be a good learning curve for newbies or those looking for a sidecar mixer to compliment their in the box DAW. I might even build the mic pre just to see how it performs, always had a soft spot for the 5534.

Did a quick google and found the specs for the output xfmrs:

http://www.revoco.cz/data/datasheets/dbe1130c1.pdf

Would love to get a translation of the complete article!

Thanks qspart and Madman for bringing this to our attention and the pdf of the original article.

 

[qspart]

Or Left and Right...

Is there a Mic/Line switch ?

Yes there is .

 

[nashkato]

😳that is one insane project
i can only imagine the financial resources that went into this .
i really gotta finally finish the quadriga tube amp from mr. haas

 

[qspart]

Some of the pushbutton switches are not working, and I’m struggling to find replacements labeled as Elma 19-482 in the parts list. I’ve searched online but haven’t had much luck locating this specific model.

Does anyone know of a compatible switch or where I might be able to source these?

Additionally, I discovered that there are no line outputs for the 13 mic/line channels , there’s line outputs only for 4 aux and 8 group channels which wouldn’t be enough if I decided to record a band on it . so I’ve ordered 12 UTM3524 output transformers to add line outputs, along with 12 VU meters for some modifications.


One more question: would it be beneficial to replace the 4558 opamps with 5532s? The power supply +-15 volt rails has 22A each should be capable of handling the extra load from the 5532s.is there anything else I should consider before proceeding with that ?


Thanks in advance.

 

[MidnightArrakis]

Some of the pushbutton switches are not working, and I’m struggling to find replacements labeled as Elma 19-482 in the parts list. I’ve searched online but haven’t had much luck locating this specific model.

Does anyone know of a compatible switch or where I might be able to source these?

Additionally, I discovered that there are no line outputs for the 13 mic/line channels , there’s line outputs only for 4 aux and 8 group channels which wouldn’t be enough if I decided to record a band on it . so I’ve ordered 12 UTM3524 output transformers to add line outputs, along with 12 VU meters for some modifications.

One more question: would it be beneficial to replace the 4558 opamps with 5532s? The power supply +-15 volt rails has 22A each should be capable of handling the extra load from the 5532s.is there anything else I should consider before proceeding with that ?

[I’ve searched online but haven’t had much luck locating this specific model] -- Are there any indications/markings on the switches themselves? Can you provide some clear and well-lit close-up photos?

[would it be beneficial to replace the 4558 opamps with 5532s?] -- Probably. The slew-rate response will go up and the noise-floor will probably go down. However, you will probably also need to add some power-supply bypass capacitors at each chip and it may also be necessary to add some circuit compensation capacitors on each chip as well. One of the "Circuit Designer Dudes" on this forum will be far better to advise you about this than I am.

[The power supply +-15 volt rails has 22A each] -- Are you sure it isn't -- 2.2A -- instead? 22-Amps is enough to run your clothes dryer!!! Is this console connected to its own 30-Amp circuit-breaker in your mains-box? It seems as though at that amount of current-draw, your hourly studio rate will need to be rather hefty, just to pay for your electrical bill!!!

[along with 12 VU meters for some modifications] -- In case you -- just might -- need some manner and/or type of an enclosure or meter-bridge panel for your VU-meters, you can let me know if you need any assistance, OK???



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[Murdock]

Some of the pushbutton switches are not working, and I’m struggling to find replacements labeled as Elma 19-482 in the parts list. I’ve searched online but haven’t had much luck locating this specific model.

Does anyone know of a compatible switch or where I might be able to source these?

Additionally, I discovered that there are no line outputs for the 13 mic/line channels , there’s line outputs only for 4 aux and 8 group channels which wouldn’t be enough if I decided to record a band on it . so I’ve ordered 12 UTM3524 output transformers to add line outputs, along with 12 VU meters for some modifications.


One more question: would it be beneficial to replace the 4558 opamps with 5532s? The power supply +-15 volt rails has 22A each should be capable of handling the extra load from the 5532s.is there anything else I should consider before proceeding with that ?


Thanks in advance.

Why did you buy transformers? According to the schematic each input module already has an output transformer. And are you sure, that none of the multipin connectors on the back are the line outs?

 

[qspart]

Why did you buy transformers? According to the schematic each input module already has an output transformer. And are you sure, that none of the multipin connectors on the back are the line outs?

That’s what I assumed initially without checking properly. But yes, only 8 of the group channels have output transformers, while the mic/line channels don’t have any. They just have a mic input, line input, remix input, and unbalanced insert sends and returns.

 

[qspart]

[I’ve searched online but haven’t had much luck locating this specific model] -- Are there any indications/markings on the switches themselves? Can you provide some clear and well-lit close-up photos?

[would it be beneficial to replace the 4558 opamps with 5532s?] -- Probably. The slew-rate response will go up and the noise-floor will probably go down. However, you will probably also need to add some power-supply bypass capacitors at each chip and it may also be necessary to add some circuit compensation capacitors on each chip as well. One of the "Circuit Designer Dudes" on this forum will be far better to advise you about this than I am.

[The power supply +-15 volt rails has 22A each] -- Are you sure it isn't -- 2.2A -- instead? 22-Amps is enough to run your clothes dryer!!! Is this console connected to its own 30-Amp circuit-breaker in your mains-box? It seems as though at that amount of current-draw, your hourly studio rate will need to be rather hefty, just to pay for your electrical bill!!!

[along with 12 VU meters for some modifications] -- In case you -- just might -- need some manner and/or type of an enclosure or meter-bridge panel for your VU-meters, you can let me know if you need any assistance, OK???

View attachment 138286

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1. I attached photo of the switch
2 . I know that there are some bypass capacitors already added in circuit . I believe 4.7uf 50 volts. And some smaller ones for highs in parallel. But not sure if they are compatible with 5532s .thanks for info and hopefully someone can clarify it.
3. I should have been more clear on power supply . I use switch mode power +- 15 . So shouldn’t be bad on electric bill. .but I know it’s overkill 😅.
4 .Your vu meter design looks great. How ever I already designed my own .thanks for sharing . It’s good to know something like that is accessible and might be useful in future projects.

 

[living sounds]

Looks like a very nice console, lot's of similarities in regards to component selection with ADT.

Pushbuttons often can be made to work again by spraying some CRC-3-36 into the U-shaped hole and pushing the button 20+ times. This is the recommendation ADT gives and I had a great deal of success with this method.

I'd strongly advise against replacing RC4558 (especially the good vintage parts) with 5532s. You will lose the stability / RF insensitivity the 'lesser' op amps provide. Additional decoupling caps will pollute the ground in ways not anticipated by the designer. Been there, done all that too many times. In the end, I always put the old op amps back in and was happy. And even if the PSU can handle the additional current draw, you will generate more heat that may or may not be too much in the console and age every component faster.

The thing to check and probably replace are the red-brown Roederstein bipolar electrolytics. These tend to go bad over time. Replace them with Nichicon Muse (green) bipolars, maybe up the size in the signal path a little (2-4x) if the frequency/phase response mandates it and space allows for it.