Hi Matt!
Still a bit confused about the 'talkback' options. Trying to make heads and tails of the schematic, seems there is a monitor out which can be used to feed a separate monitor mix? I assume that the MONITOR OUTPUT is feed by whatever IN is selected from the remote or is there a way to feed a DIFFERENT input to the MONITOR OUTPUT instead of what is going to one of the 3 OUTPUTS?
I decided to move talkback combiner/phone amp outside the box.
First, more than 60% of potential users will not use talkback option.
Second reason, as long as everything is passive, only 12V 2A switching power supply for
relays and logic used.
It is very cheap for these days and possible to buy in most electronics stores.
Then, power supply for audio inside same box will be bit messy.
PCB's for talkback combiner/phone amp will be offered as well for cheap cost.
There's 9 pin SUB-D-9 socket for this purpose.
It feeds balanced signal from input selector (without level controll) and talkback command
to combiner/amp. If there's a need of separate mix in phones, feed signal from
souncard output (say 7-8) to talkback combiner.
Also while on Talkback, in a previous thread you mentioned that an electret mic could be used and the circuit would be onboard? Is this still the case?
Yes, talkback combiner contains 2 balanced line receivers, electret mic amplifier with "gain" pot,
and kinda "summing circuit" which serves 2 purposes: put down mix level for 7-8 db
and feed talkback signal when TB ON.
Phones signal passes to output at unity gain when talkback is off.
Circuit is simple, 1xquad opamp and 1xsingle opamp, about 25 misc parts total.
I have a small board for phone amplifier, it contains dual opamp and current boosters,
volume pot, 6.3 stereo jack....simple at all, nothing special.
Then, for phones, just take one combiner board and some
phone amp's boards, put this into 1RU...done.
Or use talkback combiner with external phone amp.
For me, and hopefully others this is important, I want to be able to have a small electret mic mounting into the 1U audio PCB rack case and use the controller to be able to turn it on and off, like the Central Station and Dangerous boxes work. Is there a way to control the attenuation of the TB as well, maybe via the remote or a pot mounted to the audio rack?
Answered
If it isn't accommodated, maybe your could make a small daughter board that could be mounted to the front panel of the AUDIO rack with a volume pot for attenuation and the electret mic and it can be powered from the rails inside the rack and then feed the output to the TALKBACK INPUT?
Answered
Also is the TB switch on the control panel latching or momentary, and or both?
Talkback is momentary, but when pressed for more than 5 sec, it latches on. Press it again to off.
Talkback have an offset-user adjustable value, 0-40 db, which puts down monitor level
when talkback in.
BTW, offsets is very usefull thing.
To define offset level:
Press TRIM+IN1 for example
Screen shows offset value
Set offset with rotary (say, 3 db)
Press TRIM again, screen shows level.
To save all offsets and current system's state as INITIAL (when power up),
press TRIM for 15 sec, it shows SAVe, done.
For example:
LEVEL -40
IN1 and MON1 selected
Offsets:
-3dB for CD, IN1
0db for Workstation, IN2,
+1 db for NS-10, MON1
0db for Genelec, MON2
-12 db for talkback,
+6 db for MONO
-30db for DIM
Sorry for all the questions, just trying to get it worked out in my head and for others so we can get the best features out of this unit.
Matt, all these are good questions.
Feel free to ask.