Master Section Controller

[ruffrecords]

OK, so you should be able to diode wire OR straight into that input. We just need to sort out the actual logic. Can you describe the conditions under which the relay is operated and not operated?

Cheers

Ian

 

[dmp]

Can you describe the conditions under which the relay is operated and not operated?

Relay should get an "on" CV +5v when front panel +5v and/or the footswitch ground are activated. The two transistor circuit works so this problem is resolved. I just need to clean up the build because it is prototyped on a breadboard at the moment.
I think I also am and going to swap the DRV134 balancing boards for boards with a trimmable gain, as suggested by Kante1603. Adding 12 dB to go from the -10 dBv nominal to +4dBu will be an improvement.

 

[dmp]

Finished the front panel

 

[dmp]

Frequency response shows some high end rolloff. Seems there is a some capacitance causing a RC LPF
The 10k resistors I am using means it is about 1500 pF (using F=1/2piRC)
Cabling is only 50 pF/ft
strange

 

[Gold]

Impedance mismatch? Do you get the same roll off at all positions on the Elma switch? Is the Goldpoint a potentiometer style attenuator or does in need to see a specific termination resistance?

 

[dmp]

Impedance mismatch? Do you get the same roll off at all positions on the Elma switch? Is the Goldpoint a potentiometer style attenuator or does in need to see a specific termination resistance?

For this test I was using a preamp for make up gain after and maybe there is an issue there. RMAA needs the return signal to be the same nominal level as the send - I'll try a different way to make up the level. This was with the goldpoint all the way up. I can try a few more positions.
The goldpoint switch is a 4 deck series of resistors. I don't think it needs a termination.

 

[Gold]

At the top position of the attenuator it should measure 0Ω from input to wiper if it's a potentiometer style attenuator. A mic preamp input impedance is pretty low (usually around 1500Ω) compared to a line level input usually above 10KΩ. Can whatever is driving the output handle a 1500Ω input impedance?

Also I'd double check the Goldpoint wiring. It should measure the total resistance of the attenuator (assuming it's a potentiometer style attenuator) in all positions from Input to Ground or Audio Common. The resistance from wiper to Input should increase as the knob is turned CW.

 

[dmp]

I used VP28 in line mode for make up gain and the response is much better - small difference in the R/L seems to stay with the monitor controller. I'll check the Goldpoint switch.

I am using an audiofire12 interface.

 

[dmp]

So I can hear a difference through some of my monitors when I use the vp28 line amp as a buffer.
With Genelecs, I don't notice (10k input impedance) but with my Altec 128B amps, I hear high end loss. These have 600 ohm input impedance.
I guess this is a drawback of the series resistor method for a passive monitor controller.

 

[dmp]

I built a INA137->DRV134 as a unity line driver on a breadboard and it makes a big improvement on driving the 600ohm amps.
I think I'll add a line driver like this to the monitor controller out, possibly with a switch to make it optional. But I don't think having this 'in' will degrade the monitor quality.
Could go back and make the whole switching unbalanced