PASSIVE RELAY-BASED CONTROLL ROOM KITS BUILD/SUPPORT TREAD

[bobine]

After a year collecting parts, I switched on the CRM tonight and listened to it clickity clack. Works great, as far as I can tell. For now I'm just using it to switch an input to one of two outputs, so level will mostly stay on zero. But level control works down to the vanishing point.

On the ohmmeter, the resistance between the input and output does not increase exactly stepwise as I reduce the level. Some steps are out of sequence. A couple of drops in level may sound greater than others, but it's hard to tell. It's not a problem for me.

Haven't played with the trim yet. One segment of one LED display is out (lower leg of the "4"). I found the hard-to-find parts through Newark. This project required a lot of thinking about the parts and much care during assembly, but it worked first time for me.

Now I need to get the talkback PCB and integrate that.

Cool project. Makes me want to do something with robots next...

Thanks, Igor!

   

 

[Igor]

After a year collecting parts, I switched on the CRM tonight and listened to it clickity clack. Works great, as far as I can tell. For now I'm just using it to switch an input to one of two outputs, so level will mostly stay on zero. But level control works down to the vanishing point.

HURRAY!!!!! Happy to hear about this.
BTW, just kidding, was it cheaper than a kt?

On the ohmmeter, the resistance between the input and output does not increase exactly stepwise as I reduce the level.

Well, it shouldn't. You have to feed signal and measure the output.

With 2% resistors (it means, worst case), loaded properly, maximum difference
between the level you see at the screen and measured out is less than 0.3db.

Some steps are out of sequence. A couple of drops in level may sound greater than others, but it's hard to tell. It's not a problem for me.

To avoid misunderstanding, let's do simple thing.
Connect out of soundcard to CRM input, and CRM's out to input of soundcars, feed 0db, and pass on all level steps.
Depending on how your soundcard loads the CRM out, there can be variation in steps, but we should expect continuity,
like (for xample) -1, -1.1, -2.1, -3,1, -4.2, -5, -6, -7.1, -8, -9.2, etc.
When crm's out properly loaded and actual source out impedance is 0...100R, 
the step tolerances are very low. Both channels btw should match at every step within 0.1 db.

Haven't played with the trim yet. One segment of one LED display is out (lower leg of the "4"). I found the hard-to-find parts through Newark. This project required a lot of thinking about the parts and much care during assembly, but it worked first time for me.

Maybe, the pin was overheated. Or, check for shorts on PCB.
With good hands, some thinking and patience, yes, CRM supposed to work from first fire-up) Congrats again!

Now I need to get the talkback PCB and integrate that.

Da ea-sy part, aye!))))

Cool project. Makes me want to do something with robots next...

Thanx man. Ahmmm.... Talented ROBOSINGER?????

 

[bobine]

Yes, you're right. With a 0db signal input and measuring the output it tracks very well. 0db input returns -0.1 and it remains consistent to -20.

More importantly, variation from left to right is within 0.1 with an occasional 0.2 difference. Only one position (-20) is off by 0.4 left to right.

One odd thing: in the -40s, there begins some drift away by up to 2db, then suddenly at -48, the ouput drops to -54.3 (both channels) and remains out by 6db to the end.

I haven't checked what mono does, but there seems to be an apparent drop in level.

I don't think the kit was available when I got the boards.

A talented ROBOSINGER would solve SO many problems.

 

[Igor]

Yes, you're right. With a 0db signal input and measuring the output it tracks very well. 0db input returns -0.1 and it remains consistent to -20.

More importantly, variation from left to right is within 0.1 with an occasional 0.2 difference. Only one position (-20) is off by 0.4 left to right.

Exactly as it supposed to be)

One odd thing: in the -40s, there begins some drift away by up to 2db, then suddenly at -48, the ouput drops to -54.3 (both channels) and remains out by 6db to the end.

Check all the resistor's values.
Or, another thing: I've read about some soundcards have significant error in their meters at low levels.
Maybe, this is due to they use less bits for level measurement so save dsp? Dunno.
Just check everything again, if all resistors are within 2%, should be fine.
My old good over-modyfied Boonton 1120 have about 0.2 db max error, thou.
However, I did some tens of CRM's of 3 kinds (mastering version, regular version, and kit);
with use of 1% resistors and right output load, all they were exactly within specs of my analyzer.

I haven't checked what mono does, but there seems to be an apparent drop in level.

Press and hold TRIM, than (while holding TRIM) press MONO, release both, set 6, now the offset for mono is +6 dB.
Press TRIM again to exit from TRIM screen.
The summing into MONO is passive, and there is the level drop for 6 db, which is easy to compensate.

I don't think the kit was available when I got the boards.

Woa, you mean, you have green PCB's? We started to make yellow at 2009. Funny! Took some time to build, aye!  ;D

A talented ROBOSINGER would solve SO many problems.

After some thinking, no) The studios will have less work.

Cool than, check, fix, and let us know how it sounds!  8)

 

[plumsolly]

Is anyone else getting some buzz on their signal, possibly from the switching power supply? I have always had lots of noise on the talkback, but I recently discovered I may have some noise on my signal as well. I am running into an unbalanced power amp which may exacerbate the situation. Is it worth exploring a linear supply?

Best,

Ben

 

[Igor]

Is anyone else getting some buzz on their signal, possibly from the switching power supply? I have always had lots of noise on the talkback, but I recently discovered I may have some noise on my signal as well. I am running into an unbalanced power amp which may exacerbate the situation. Is it worth exploring a linear supply?

Best,

Ben

Nope) Looks like a grounds issue.
INA137 x2 (etc) and some parts can easy make your power amp input balanced.
In any case, to be at safe side, check how much AC do you have at out of power supply; up to 2mV is OK.

 

[yosh]

Hi, I've had igor's CRM working in my studio for almost two years now. I love it, but have had a couple issues happening for a while now that I would like to figure out.

When turning the encoder sometimes there are large jumps in level (like -30dB to -10dB) in an instant. This happens when I'm turning the encoder down and the jumps are always up. The display changes with the level, accurately showing the jump in level. Makes me look kinda dumb to clients sometimes. They ask me to turn something down and suddenly it's twice as loud. Heh heh. Oops.

I did try resetting the unit according to the instructions beginning with turning on the unit with the trim button pressed.

Any ideas on why this might be happening?

Thanks!
Josh

 

[Whoops]

Hello,
I'm building my own studio at the moment, and most of the stuff will be high quality DIY.

I really need a Control Room device, but I couldn't buy one of Igor's Kits at the time,
so I would like to ask if there's anyone that has one available for sale, please let me know.

Maybe there's people that bought more than one kit or that have one kit that they will not use anymore.

Thanks

 

[plumsolly]

Is anyone else getting some buzz on their signal, possibly from the switching power supply? I have always had lots of noise on the talkback, but I recently discovered I may have some noise on my signal as well. I am running into an unbalanced power amp which may exacerbate the situation. Is it worth exploring a linear supply?

Best,

Ben

Nope) Looks like a grounds issue.
INA137 x2 (etc) and some parts can easy make your power amp input balanced.
In any case, to be at safe side, check how much AC do you have at out of power supply; up to 2mV is OK.

I did a little more testing. I can more or less completely eliminate the buzzing by transformer isolating on the way to the speakers. That, however, is not an ideal solution for various, obvious reasons. I measured the AC coming out of my power supply at 50-100mV!!??. Here is a link to the PS: http://www.meanwell.com/search/PLP-30/PLP-30-spec.pdf It is the PLP-30-12. It has a quoted ripple+noise of 2V p-p. What do you think?

Thanks, Ben

 

[Igor]

Hi, I've had igor's CRM working in my studio for almost two years now. I love it, but have had a couple issues happening for a while now that I would like to figure out.

When turning the encoder sometimes there are large jumps in level (like -30dB to -10dB) in an instant. This happens when I'm turning the encoder down and the jumps are always up. The display changes with the level, accurately showing the jump in level. Makes me look kinda dumb to clients sometimes. They ask me to turn something down and suddenly it's twice as loud. Heh heh. Oops.

I did try resetting the unit according to the instructions beginning with turning on the unit with the trim button pressed.

Any ideas on why this might be happening?

Thanks!
Josh

One of these (or all of them) will work.
1). Replace encoder to a new one;
2). Change R13, R14 to 1k;
3). Change CE1, CE2 (15nF ceramic) to 10...22 nF poly, 5mm, 50...63V
(last one wasn't audiofullery joke

 

[plumsolly]

Is anyone else getting some buzz on their signal, possibly from the switching power supply? I have always had lots of noise on the talkback, but I recently discovered I may have some noise on my signal as well. I am running into an unbalanced power amp which may exacerbate the situation. Is it worth exploring a linear supply?

Best,

Ben

Nope) Looks like a grounds issue.
INA137 x2 (etc) and some parts can easy make your power amp input balanced.
In any case, to be at safe side, check how much AC do you have at out of power supply; up to 2mV is OK.

I did a little more testing. I can more or less completely eliminate the buzzing by transformer isolating on the way to the speakers. That, however, is not an ideal solution for various, obvious reasons. I measured the AC coming out of my power supply at 50-100mV!!??. Here is a link to the PS: http://www.meanwell.com/search/PLP-30/PLP-30-spec.pdf It is the PLP-30-12. It has a quoted ripple+noise of 2V p-p. What do you think?

Thanks, Ben

Is it worth investing in a new, lower ripple, psu?

Thanks,

Ben

 

[plumsolly]

Igor...? Anybody...?

 

[yosh]

One of these (or all of them) will work.
1). Replace encoder to a new one;
2). Change R13, R14 to 1k;
3). Change CE1, CE2 (15nF ceramic) to 10...22 nF poly, 5mm, 50...63V
(last one wasn't audiofullery joke

Replacing the encoder did the trick! Thanks Igor!

Josh

 

[Igor]

Is anyone else getting some buzz on their signal, possibly from the switching power supply? I have always had lots of noise on the talkback, but I recently discovered I may have some noise on my signal as well. I am running into an unbalanced power amp which may exacerbate the situation. Is it worth exploring a linear supply?

Best,

Ben

Nope) Looks like a grounds issue.
INA137 x2 (etc) and some parts can easy make your power amp input balanced.
In any case, to be at safe side, check how much AC do you have at out of power supply; up to 2mV is OK.

I did a little more testing. I can more or less completely eliminate the buzzing by transformer isolating on the way to the speakers. That, however, is not an ideal solution for various, obvious reasons. I measured the AC coming out of my power supply at 50-100mV!!??. Here is a link to the PS: http://www.meanwell.com/search/PLP-30/PLP-30-spec.pdf It is the PLP-30-12. It has a quoted ripple+noise of 2V p-p. What do you think?

Thanks, Ben

Is it worth investing in a new, lower ripple, psu?

Thanks,

Ben

I completely misunderstanding:
"I can more or less completely eliminate the buzzing by transformer isolating on the way to the speakers. "
You use switch mode PS for CRM, right? It does not adding hum like power trafo. Strange.
The CRM is completely passive and the effect of power supply is negligible, it used ONLY for powering the relay coils and isolated
from talkback combiner by use of dc/dc converter.
In any case, take 12V STABILIZED power supply and check. I think the issue is ground loop. However, there are many variants

 

[Igor]

One of these (or all of them) will work.
1). Replace encoder to a new one;
2). Change R13, R14 to 1k;
3). Change CE1, CE2 (15nF ceramic) to 10...22 nF poly, 5mm, 50...63V
(last one wasn't audiofullery joke

Replacing the encoder did the trick! Thanks Igor!

Josh

See, black magic worked! Enjoy

 

[bobine]

I thought I'd share how I inlaid my controller in a little wooden table...my entire work surface.

I plan to spray paint the back of the Lexan white once I decide how to label the buttons. 

 

[CapRock]

Hey Igor,  I dont know if this is normal or not but for some reason, when I adjust the trim for my sub it adjusts the level of SPK1 + SPK2 also, as in the volume of all outputs is adjusted.  Is that how it is supposed to be?  Another issue I am having is the Speaker 2 output decreases volume between steps -48 to -47, -32 to -31, and -16 to -15.  I see a pattern there what is your take on it?  I ran the outputs back into my DAW to meter them and saw that when speaker 2 is active the sub output also responds the exact same way.  SPK1 output increases gain properly all the way from cut to zero.  When I was looking at my software meters I noticed another weird thing at the steps in which I listed above.  When I was actually looking at what the meters were reading it showed that at the step before each of the ones listed above, only one side (say the right side) would bump up a small bit in level, but the left would not, then at the next step the left channel only, would bump up to match the right.  After they were back inline the steps would become normal again until I reached the next step listed above, and then the same process would repeat again.  This has been going on since the unit was completed about a year ago and I just never had the time to address it, let me know what you think, thanks...

 

[plumsolly]

Speaker 2 output decreases volume between steps -48 to -47, -32 to -31, and -16 to -15.

I had the same problem. I made sure I had all the resistors correct and finally figured out that it was because I was trying to drive a 600-ohm load - the loss was different at different steps (presumably because of the change in output impedance) which meant that at -47, for instance, the additional loss from trying to drive a low impedance load with a higher impedance output was larger in magnitude than the 1db increase caused by going from -48 to -47, thus a net loss. Mine works fine when going into a bridging input.

Best,

Ben

 

[CapRock]

Thanks for hitting me back.  That makes sense to me when I hear the audible difference when listening through the speakers that are connected to SPK2 output, but why would it show up also when I send the signal from spk2 output back into my DAW to view the meters?  I have that set of speakers connected to the output of speaker 2 through a patchbay so it was easy to take those very same sends and route them back through my converters into my interface.  It appears that i see a visual representation of what I am hearing when I let the signal actually pass to the speakers.  Its not the biggest deal, just something I wanted to try and troubleshoot while I have the time.  I flipped the dip switch both directions with no change at all. 

 

[plumsolly]

why would it show up also when I send the signal from spk2 output back into my DAW to view the meters?

Yeah - this is confusing, your speaker's input should be high enough not for this to happen there either. Do you have anything else loading the outputs of the controller? What are your values for RL1-RL4?

Best,

Ben