PASSIVE RELAY-BASED CONTROLL ROOM KITS BUILD/SUPPORT TREAD

The matter is not work, but my time. I can't put here custom and hopefully working solution for every request....sorry.
Regarding 2 transformers: it is not 2 transformers but 12V 2A switching
mode power supply and 2x (18...25)V 20...30VA toroidal trafo. I think this is simplest way to fire everything up.
There are +5V dig, +12V dig, +/-15V talkback combiner, +/-15V for plasma VU meter
(it is noisy, I'd not recommend to hook it on same supply as TB combiner),
and +245V for plasma display. Sure, there are many elegant solutions as building quiet switching power supply
for 6 outputs, but....trust me, the comb of 12V SW PS and toroid is the simplest one.

Thats cool man, just wondering if there was an easy way for everyone.

I'm guessing i lose sub functionality if i reverse the inputs and outputs. As in i can't use two outputs at the same time.
And by reverse the inputs/outputs could i just simply send the inputs down the outputs and vice versa or does it actually have to be hard wired on the board.



Sorry for the question, i just don't want to destroy this beautiful board of yours.

Nuff to destroy
Leave it as-is, SUB can be added over OUT1/2.

Hey guys,

Bit of a noob here trying to learn, so bear with me!

So i'm trying to figure how the in/out impedances are figured. For example, i want to know how you maintain a 3k impedance seen by the sound card. So i take the load resistance (10k) parallel with the shunt resistor and add the series resistor. This results in impedances varying from around 7.5k to 3k. What am i missing?

Also, i'm looking at the mono implementation and i cannot make heads or tails of it... anyone feel kind enough to walk me through it?

I sincerely appreciate any help!

The input impedance (seen by soundcard out) is 3k to ground at each + or - output.
Every attenuator's stage is calculated so, that we have 1,2,4,8,etc. db attenuation at 3k load.
If we need 19db attenuation, 16, 2,1 attenuators cascaded. Worst case, audio passing 6 attenuator's stages at -63 db.
Work situation, we need -40...-15db attenuation, audio passes 1...4 attenuator's stages (8 resistors max).

Compared to 10:11 resistors with Elma switch at mid (normal work position), it is IMHO better solution....
Ah yes, for audio-purists, relay contacts are goldplated and hermetically sealed,
i.e. no distortion caused by oxidation after year of work in smoking studio
I.e. pipe amateurs can use it!!!!

Power amp see output of soundcard through relay contacts at 0 attenuation;
Worst case of output impedance seen by power amp is approx. 1k2. I am not good at mathematics,
but can calculate it if someone persists

For precision 1dB steps, CRM monitor output should be loaded at 3k, however,
the steps will be within +/-0.5dB at 2...6k load.

There are attenuator's load resistors, RL on schematic.

Choose them so then Rl in parallel with your amp input will give 3k.

If different input impedance amplifiers used, take higher value for Rl, and terminate higher value amplifier with resistor at the input.

Anyway, perfect load termination does not affects or improoves audio quality, it is just precision.
Take RL in range 4k3...7k5 and be happy with +/-0.5 db steps at any amp with 5....20K input impedance

Mono: 3k resistors inserted between soundcard out and attenuator's input,
than tied together.
There is an offset which can be used to correct -6 dB insertion loss at mono;
press trim+mono, adjust say +6db, press trim again.. Every time MONO is ON, microcontroller will add 6dB to attenuator's value,
of course, if the level is lower than -6dB. Working level (normally) is between -40....-15dB, so, it quite correct.
Current system's state with all offsets, etc. is stored by holding the TRIM button for 5-8 sec.
Next time system powered on, it will be the initial state.

Huh...hope it is clear, despite my english

BTW. About 40 CRM kits are working arround the world. I very happy with it,
just because clean monitoring is one of important tools to make a good sounding music...
More good music=good!
So, if this makes happy someone except me, cool and enjoy!

Hi Igor

My tech friend is in the process of modifying my CRM to 2in 4out.

We are having some problems, in that the attenuator is not working and the 3 new inputs are not switching as expected. There is also a lot of bleed between the inputs.

Any ideas what may be wrong?

The ins are connected by d-sub to the main board via my d-sub patchbay. However we have checked them with a mogami snake I had and they are still doing the same thing.

The outputs are on XLR but they are switching OK.

In the instructions of how to do the mod you mentioned that we need to cut the connections to ground on outputs. Is this the same as cutting the bottom layer traces? Or do would we need to something extra.

It may be worth mentioning that this CRM is the silver one pictured earlier in the thread which I bought from Peter [Sinestar]. However we have separated the remote out and put the main unit in a rack behind the desk.

Cheers in advance for any help
George

Anybody else know what this could be?

Need to get sorted asap. I'm having to turn work away as this is an essential part of my studio.

Cheers

Hey,

Back again, trying to understand the schematic

What is the purpose of the 68 ohm R's? i.e. R3-R5?

thanks again!

Hi, the purpose of r3-r5 is to tie shorted (muted) amp's inputs to ground without hum if amp is unbalanced at all.
I know, this is 0.01% case, but...anyway.

Hi Igor

My tech friend is in the process of modifying my CRM to 2in 4out.

Click to expand...

I mentioned I can't always give support on modifications....the kits are AS-IS. Anyway.
Just finnished to move the lab to new bigger place and overloaded with tones of stuff.
Well, let's go little by little. Did this worked before the mod?

We are having some problems, in that the attenuator is not working and the 3 new inputs are not switching as expected.
There is also a lot of bleed between the inputs.
Any ideas what may be wrong?

Click to expand...

OK.... You mean cross-talk? Many missing info.

Grounds. Wiring. Pictures please.

Attenuator is not working: can you see 7-segment display changes according to rotary's rotation?
Do you hear relay's clicks from step to step?

The ins are connected by d-sub to the main board via my d-sub patchbay.
However we have checked them with a mogami snake I had and they are still doing the same thing.

Click to expand...

Huh. What is "same thing"? I am stupid Russian without multilanguage W7 support. PleaZZ slow

The outputs are on XLR but they are switching OK.

Click to expand...

It means, the outputs are wired to external XLR's via Molex 3-pin connectors?

Please suport some pictures after mods. It will be helpfull to solve the issue.

In the instructions of how to do the mod you mentioned that we need to cut the connections to ground on outputs. Is this the same as cutting the bottom layer traces? Or do would we need to something extra.

Click to expand...

Just see schematic. Idea is we swapping the input and output selectors. The input now is output.

Remove 68R resistors. White lines are indicating traces to cut from bottom. Signal now comes to "/outputs/" 1-2,
than goes to attenuator's INPUT (connect 4 wires) than goes from attenuator's OUTPUT to "/input/" selector (connect 4 wires).
Hope it is clear.

It may be worth mentioning that this CRM is the silver one pictured earlier in the thread which I bought from Peter [Sinestar]. However we have separated the remote out and put the main unit in a rack behind the desk.

Click to expand...

OK. Will try to help in a free minute.

Peter told me his CRM was working fine without any issues. Let me know more about "mods".

Anyone else have some pics of finished unit's? I am interested to see what people did with finishing! The mastering rack setup Sinestaraudio did is phenomenal for sure!~  ;D

i'll be finishing mine in about a month?  :

mpc3000limited said:

Anyone else have some pics of finished unit's?

Click to expand...

http://www.groupdiy.com/index.php?topic=35018.0

Dear Igor,
We have 2 of these units. Both have had problems with encoders. When first assembled everything works fine but after a week or so they begin to have intermittent problems with deciding if they are turning up or down and eventually they only work in one direction. We've tried several different encoders with the same result.

Also one of the units stopped working completely. At power up it displays U20 and then freezes with talback, input 1 and speaker 3 lit and the display at 0 and is completely unresponsive. Any ideas?

( I'm editing this but leaving this question in case someone else has a similar problem) The error U20 message was caused by a sticking #3 input(or output after mod) switch.

Tim, please check everything include power supply and especially
values of capacitors near the rotary encoder.
Maybe, there's a bad contact.
Check for shorts on pcb as well.
I never had prob like this, except if power supply has really bad contact,
the chip can go into wrong state.
It seems like both units have same wrong value resistor or capacitor,
or power supply is way noisy, or somehow it went into wrong configuration and was saved.
After checking every bit of hardware, do next.
Hold TRIM button than power on unit. You see S(e)TU(p).
Press in1 button, TRIM again, check all trim inserts are OK,
save initial state with all zeroed trims, than power off, wait minute, power on.

BTW, are these units were done from kits or you sourced the parts yourself?
Pics can be helpful.

There was another issue with guy who "modified" already working unit.
Really, this is not simple project and I simply can't give support
for every wrong case / have no time!!!! /. From the other side, if everything done carefully
and no mistakes, CRM works from first fireup.
I can offer next: if unit assembled from my kit, send it to me,
and we will fix it for a minor fee.

HI folks, I' ve to build mine CRM, so I need  to know what is IC5. an witch type of encoder
I've to use.

thanx

Mik

Hi Mik, there was a BOM posted on this thread.
IC5:
1    MM5540    LED CONTROLLER WITH BRIGHTNESS  IC5
http://il.farnell.com/micrel/mm5450yn/led-display-driver-34-seg-5450/dp/1213480

ALPS ROTARY ENCODER
http://il.farnell.com/alps/ec12e1220401/encoder-vertical-12-det-12ppr/dp/1520809?_requestid=8119

Hey, just finished my CRM with VU and talkback, just putting it in a box now. Will have pictures soon.

Just wondering if there were any things that i'd need to know, i saw to set dim level you hold down trim and dim and set it, then press trim then dim and it saves it. Anything else like that? Also setting Input/Output offsets?

thank you Igor, were's the link of the BOM ? I can't find it.

Mik.

The microcontroler comes with all settings inside, no need to do anything special.
Pictures are more then welcome!
@mik: I mailed you the BOM.