Midas CR01 Module Troubleshooting

Hi there,

bought some unusual vintage Midas EQ Modules a while ago and finally finished to put them into a rack.

In general they work but there is a strange behavior in equalization. I don't expect linear behavior here but this is a little bit odd. Eg turning bass down below 10 o clock results in bass boost. Also bass cut and cut shelf works strange. Cutting at 180 Hz works more like a boost. If i dial the mids to 3 o Clock and set Q to wide, so the whole mid area is lifted up a little bit, the other knobs seem to do more what they are supposed to do. Its seems a little bit like the offsets of the pots are shifted. 

I've attached the response curve which i get if i dial all knobs to zero.

By the way, its the same behavior for both units. The biggest change i made was replacing some E caps 25uF with 22uF. But made a additional check with the old ones.  Same result.

I would be very thankful for every hint or idea. I'm just a hobbist able to connect some wires together For debugging i need some help.

Hi,

I don't have your input-modules, but have all that is left from that console they came from.
Sadly there are no schematics to be found and this module is very unique.

It is quite a complex layout for the EQ, but it comes down to:
- Hi-cut-filter-switch 6kHz-10kHz-Out
- Hi-shelf (red knobs) +/-16dB & Frequency 20-4kHz variable
- Presence (green knobs) +/-16dB & Frequency 2-3-4.5-6-8-10kHz selector-switch
- Middle-parametric (blue knobs and right fader) +/-16db, Width, selector-switch A/B/C for the frequency fader
- Low-shelf (left black knob and left fader) +/-16dB, 40-300Hz frequency fader
- Low-cut-filter-switch (H.P.FILTERhz = small black knob) 180-120-80-50-30-OFF
As the bands are very much overlapping you can influence separate controls and can create dramatic effects.

If you set all controls (big knobs) to '0dB' and Hi-cut 'Out' and H.P.Filter 'Off', do you get a 'straight' frequency response?
If not, could you publish the graph?

here is a picture of the original console your modules came from:

If you set all controls (big knobs) to '0dB' and Hi-cut 'Out' and H.P.Filter 'Off', do you get a 'straight' frequency response?
If not, could you publish the graph?

Click to expand...

Thats what i did.

Eg here mid 0dB, frq: 300, Other set as you said


I get a 'flat' curve if i set mid to +4dB


If i go below -6db in mids i get a boost


If i set mid down to 35Hz +4dB