Mysterious mixing console

[qspart]

Some capacitor date codes indicate on 2006.
But not sure . .also I attached previously mentioned board with some markings on it .

 

[qspart]

Thank you again, everyone, for your input. Although we didn't figure out who made it, I still managed to build a power supply for it, and it runs beautifully. It has extremely low noise, tons of gain when necessary, and the sound quality is excellent. The transformers add a nice weight to the sound, and I couldn't be happier with the result.

 

[Madman]

It is a PM500 console from the German DIY magazine Elrad mid of the 80s, designed by our esteemed colleague Gerhard Haas (RIP 2020) from Experience Electronics (Germany).

 

[rock soderstrom]

It is a PM500 console from the German DIY magazine Elrad mid of the 80s, designed by our esteemed colleague Gerhard Haas (RIP 2020) from Experience Electronics (Germany).


View attachment 134486

Really, they had such high-quality projects in the Elrad? Amazing! There is a certain similarity. Do you have the complete original article?

Gerhard Haas was a nice man, I spoke to him several times on the phone, he was very informative and eager to provide information. RIP.

 

[Madman]

yes in the 80s there some high-quality projects, here´s the article of the PM500

 

[rock soderstrom]

yes in the 80s there some high-quality projects, here´s the article of the PM500

Wow, 30-page monster project. I wonder how many of them were built?

Dank dir!

 

[ruffrecords]

I just downloaded the article and perused the schematics. That is one very competent design. Should easily be able to hold its own with the best of today's offerings. I am impressed.

Cheers

Ian

 

[qspart]

It is a PM500 console from the German DIY magazine Elrad mid of the 80s, designed by our esteemed colleague Gerhard Haas (RIP 2020) from Experience Electronics (Germany).


View attachment 134486

Thank you so much! I can't believe you actually found it. I had almost lost hope of figuring out what it was. I really appreciate the information, you’re a legend !

 

[Murdock]

yes in the 80s there some high-quality projects, here´s the article of the PM500

Wow, what a great find!
Do you know if the pcb layout was also published?

 

[RuudNL]

Isn't it a bit strange that the phantom power resistors are connected after the (M-L) attenuator?

 

[qspart]

Isn't it a bit strange that the phantom power resistors are connected after the attenuator?

I'm not sure if it's strange , but it seems like parts of the circuit diagram are missing in that schematic. , when I switch the line input, the phantom power automatically turns off and won't engage. So probably that’s why.

 

[RuudNL]

What happens is that the phantom power is almost shorted through two 100 ohm resistors, causing a dissipation in each phantom resistor of (48/6900) * 48 ~ 330 mW. So 660 mW 'wasted'.
I can imagine why they wanted a low source impedance when in the line mode, but I would have done this differently.

 

[MidnightArrakis]

Some capacitor date codes indicate on 2006.
But not sure . .also I attached previously mentioned board with some markings on it .

Should you ever need any of these ancient and undocumented PCBs to be "Reverse-Engineered" so you can have "New/Old" PCBs fabricated.....let me know, OK??? I have done PCB "Reverse-Engineering" projects for old 1974 API mixing consoles and 1979 U.S. fighter jet PCBs. Just sayin'.....


/

 

[Evertide]

Mic > Phantom , Line > No Phantom And Attenuator

 

[ruffrecords]

Mic > Phantom , Line > No Phantom And Attenuator

Exactly my thought too. You do not want significant dc reaching a line input. With the 100 ohm resistor my calculator says the dc is reduced to 70uV.

But I agree, it is wasteful of power. Better to put the mic/line switch on the transformer side and have the pad permanently connect to the line input.

Cheers

Ian

 

[Evertide]

The input is for Mic and Line , look at Bild 1 on page 3...

 

[ruffrecords]

The input is for Mic and Line , look at Bild 1 on page 3...

Oops.

Ian

 

[Madman]

Wow, what a great find!
Do you know if the pcb layout was also published?

The PCB layouts was normally printed in the magazine but in this case it was too big to depict it in 1:1 scale, back in the 80s you did have the chance to purchase PCB foils from the publisher of the magazine.

 

[qspart]

The input is for Mic and Line , look at Bild 1 on page 3...

I suspect there is a different modification in my channel strips
, as it seems there are two input transformers on the board. It’s likely that one transformer is dedicated to the line input, while the other is for the mic input.

 

[Evertide]

Or Left and Right...

Is there a Mic/Line switch ?