PASSIVE RELAY-BASED CONTROLL ROOM KITS BUILD/SUPPORT TREAD

[Moby]

@Moby
what kind of thickness you choose for the remote panel ? 3mm ??

Nope, 2mm.

 

[jimkeaney]

I'm having some bizarre issues with my CRM these past 2 days. The input volume dropped severely on the right channel. When I put pressure on the audio board, it would become intermittent, so I tracked it down to a bad solder joint on one relay. After I reflowed the solder, things were functioning okay. But then a few minutes later I noticed the volume dropped again and this is the weird part... when I turn the volume from -33 to -34 it actually gets twice as loud. Then from -34 down, each step gets quieter (as it should). But something is definitely wrong. Any ideas out there?

One concern I have is... I'm using a 12v 2.1A PSU as Igor advised, but are we assuming the TB combiner can run safely from that too? Then, I also added a VU meter buffer amp (pulls 10mA) which I'm running from that same PSU as well. Could any of these issues be related to insufficient power?

Thanks for the help

 

[Audioman]

Hi Jimkeaney,
Can you try to power up the unit using an laboratory psu ? if yes you can measure the total absorb of your unit and if is more than 2.1 Ampere the problem is there .
let me know

 

[jimkeaney]

Thanks for the reply audioman. I do not have a lab psu, but perhaps I can use my DMM to figure out the load? Would need some instructions on that though.

Also in the build docs for the CRM it states that all Molex connectors are:

1: +
2: ground
3: -

When I DMM audio output molex pins 1 & 3 there is continuity. Should the hot & cold be connected at the board?

Also can anyone tell me exactly how they have these boards grounded? I see 2 Aground pads. Chassis? anywhere else? Should the db25 connectors claws also be soldered? I feel like my issue has something to do with bad grounding or balanced/unbalanced issues.

thanks!

 

[jimkeaney]

update on my issues... I reflowed all solder connections on the audio board and everything seems to be working again fine. I did find a couple suspicious spots (oops). I also figured out that I had a strange problem with one of the cables going to my RIGHT Genelec 1031a. Get this... when I would engage my API2500 compressor, the right speaker would drop drastically in volume. I still have no idea how that could be possible since I metered the compressor alone and it's in and outs were balanced fine. Maybe an impedance thing? Bizarre. anyhow, for now, I think I'm okay with the CRM  :-X

PS I'm still curious how and where other builders grounded their CRM's

 

[Audioman]

Hi Jimkeaney
you cannot measure the load of your unit with the multimeter in parallel you must measure it in series .
this is why i ask you if was possible power up the unit with a laboratory psu.
my unit is almost finished and i count to power up on saturday and i will make some measure
during the measures i make some picture and post here
yes claws are be soldered

P.S. i presume DMM mean Digital Multi Meter 

Thanks for the reply audioman. I do not have a lab psu, but perhaps I can use my DMM to figure out the load? Would need some instructions on that though.

Also in the build docs for the CRM it states that all Molex connectors are:

1: +
2: ground
3: -

When I DMM audio output molex pins 1 & 3 there is continuity. Should the hot & cold be connected at the board?

Also can anyone tell me exactly how they have these boards grounded? I see 2 Aground pads. Chassis? anywhere else? Should the db25 connectors claws also be soldered? I feel like my issue has something to do with bad grounding or balanced/unbalanced issues.

thanks!

 

[jimkeaney]

Hi Jimkeaney
you cannot measure the load of your unit with the multimeter in parallel you must measure it in series .
this is why i ask you if was possible power up the unit with a laboratory psu.
my unit is almost finished and i count to power up on saturday and i will make some measure
during the measures i make some picture and post here
yes claws are be soldered

P.S. i presume DMM mean Digital Multi Meter 

Thanks for the reply audioman. I do not have a lab psu, but perhaps I can use my DMM to figure out the load? Would need some instructions on that though.

Also in the build docs for the CRM it states that all Molex connectors are:

1: +
2: ground
3: -

When I DMM audio output molex pins 1 & 3 there is continuity. Should the hot & cold be connected at the board?

Also can anyone tell me exactly how they have these boards grounded? I see 2 Aground pads. Chassis? anywhere else? Should the db25 connectors claws also be soldered? I feel like my issue has something to do with bad grounding or balanced/unbalanced issues.

thanks!

cool, I'll solder the claws - can;t hurt Yes, I meant Digital Multi Meter.

 

[jimkeaney]

I put VU meters in my CRM rack just to show where the program level is. But because I work mostly in the DAW (dbfs) I'm starting to think VU's were a bad idea. My convertors "zero" is +22 (SSL alphalink). The VU meters only have about 25db of 'range' as it is. I envy Janzoulou's meters (like 40db of range) post #428

Would it be silly to add a switch at the meters that adds an attenuator to the meter feed before it hits the VU amp? Or after? If I did this, I'd like to pad it accurately so I imagine some sort of trimpots would be necessary. Can anyone point me to a schematic or general ideas of what it would take to make this happen?

One big concern, will attenuating the meter feed effect the (resistance) anywhere else in the CRM?

 

[Audioman]

Hi Jimkeaney,
i though to put vu meter on my build but after read your post the doubt are coming !!
The meter showing the inputs ?
i have a pair of sifam R32AF but i don't know if is a good or a ba idea installing in the unit ...
i also use DAW for work and i don't know what to do now
I also looking for the datasheet of the sifam R32AF for the cutout of the meter bezel anyone can sent me ?

P.S. did you solve the problem of volume drop ?

I put VU meters in my CRM rack just to show where the program level is. But because I work mostly in the DAW (dbfs) I'm starting to think VU's were a bad idea. My convertors "zero" is +22 (SSL alphalink). The VU meters only have about 25db of 'range' as it is. I envy Janzoulou's meters (like 40db of range) post #428

Would it be silly to add a switch at the meters that adds an attenuator to the meter feed before it hits the VU amp? Or after? If I did this, I'd like to pad it accurately so I imagine some sort of trimpots would be necessary. Can anyone point me to a schematic or general ideas of what it would take to make this happen?

One big concern, will attenuating the meter feed effect the (resistance) anywhere else in the CRM?

 

[Moby]

One big concern, will attenuating the meter feed effect the (resistance) anywhere else in the CRM?

If you put any resistance in parallel to your existing input impedance it will be changed of course. But, you can make cheap opamp hi Z input buffer and after that to trim signal for your VU's. That way  the impedance change will be aceptable.

 

[Audioman]

Hi Moby,
Your advice is make a meter buffer for attenuate the meter feed ??

One big concern, will attenuating the meter feed effect the (resistance) anywhere else in the CRM?

If you put any resistance in parallel to your existing input impedance it will be changed of course. But, you can make cheap opamp hi Z input buffer and after that to trim signal for your VU's. That way  the impedance change will be aceptable.

 

[Moby]

Hi Moby,
Your advice is make a meter buffer for attenuate the meter feed ??

One big concern, will attenuating the meter feed effect the (resistance) anywhere else in the CRM?

If you put any resistance in parallel to your existing input impedance it will be changed of course. But, you can make cheap opamp hi Z input buffer and after that to trim signal for your VU's. That way  the impedance change will be aceptable.

Right. Or you can do it passivelly but with possible impedance degradation. What's the input impedance of your amplifier ? Try to calculate parallel resistance of the amp and passive attenuation network and see is it drops below 10k. If yes, then is better to go with active buffer. Just my 0.2 c
Edit: sorry, i missed the detail of VU measuring the input. Right? Sorry if I confused you, I was typing in hurry. Maybe the best route is to try passive. If you don't have any signal drop, than you are done.

 

[jimkeaney]

One big concern, will attenuating the meter feed effect the (resistance) anywhere else in the CRM?

If you put any resistance in parallel to your existing input impedance it will be changed of course. But, you can make cheap opamp hi Z input buffer and after that to trim signal for your VU's. That way  the impedance change will be aceptable.

Thanks Moby

I already have a buffer amp before the VU meters. This one from JLM http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=163

They come with 25-turn trimpots to calibrate the meters. Would I be able to take the signal after that trimpot and add a switch in the path with another trimpot to further pad it (-22)? or is this a messy idea? If ok, how could I add such a switch/circuit? Thanks for the ideas/help

 

[Moby]

I already have a buffer amp before the VU meters. This one from JLM http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=163

They come with 25-turn trimpots to calibrate the meters. Would I be able to take the signal after that trimpot and add a switch in the path with another trimpot to further pad it (-22)? or is this a messy idea? If ok, how could I add such a switch/circuit? Thanks for the ideas/help

You can probably make that with paralleling one more trim , but I can't see the schemo of the buffer. Is the trimmer gain of the amp or input pot? If it's gain, than adding one more trimm and making it switchable can do the job.

 

[jimkeaney]

I already have a buffer amp before the VU meters. This one from JLM http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=163

They come with 25-turn trimpots to calibrate the meters. Would I be able to take the signal after that trimpot and add a switch in the path with another trimpot to further pad it (-22)? or is this a messy idea? If ok, how could I add such a switch/circuit? Thanks for the ideas/help

You can probably make that with paralleling one more trim , but I can't see the schemo of the buffer. Is the trimmer gain of the amp or input pot? If it's gain, than adding one more trimm and making it switchable can do the job.

The trimpot on the board looks like it's right at the input, so maybe I should grab the output of the buffer amp (right before it hits the vu meter) and add a switch 2nd trimpot there?

 

[Moby]

It's really hard to judge without schematics. All you can do is to try.

 

[Audioman]

Hi All
yesterday i power on for the first time my unit , without the box because at the moment is not ready
after trying 3 different vga cable i must solder a DIY vga cable because all three have a short inside on the pin 4 (as describe in the before pages of the thread )
after that the unit is working correctly and comparing to the mixing desk control room (tac scorpion) is absolutely amazing clean sound !!
it was like change my studio monitors !! absolute fantastic thanks to Igor for this amazing work !! he is an absolutely genius !!
now it's time to finish design the box of the remote control and the front panel
when i finish the unit i post some pictures
at the moment looks like this  ;D ;D ;D ;D ;D ;D ;D ;D

 

[jimkeaney]

Hi All
yesterday i power on for the first time my unit , without the box because at the moment is not ready
after trying 3 different vga cable i must solder a DIY vga cable because all three have a short inside on the pin 4 (as describe in the before pages of the thread )
after that the unit is working correctly and comparing to the mixing desk control room (tac scorpion) is absolutely amazing clean sound !!
it was like change my studio monitors !! absolute fantastic thanks to Igor for this amazing work !! he is an absolutely genius !!
now it's time to finish design the box of the remote control and the front panel
when i finish the unit i post some pictures
at the moment looks like this  ;D ;D ;D ;D ;D ;D ;D ;D

Congrats! Doesn't it feel great to see it come alive? I too had issues with pin 4 on the VGA. So I grabbed pin 4 with needlenose plyers and just pulled them out on each end. Problem solved

 

[Audioman]

yes when you see it come alive is amazing !! technologic miracle
right now i design the front panel and the control panel ... front panel design time !!
the only doubt is regarding install or not the vu meter on the front panel
do you think are useful or not ?
another think that i don't understand is the setting of the dip switch on the audio board
can you explain me the function of that ?
thank you in advance
Fabio

Hi All
yesterday i power on for the first time my unit , without the box because at the moment is not ready
after trying 3 different vga cable i must solder a DIY vga cable because all three have a short inside on the pin 4 (as describe in the before pages of the thread )
after that the unit is working correctly and comparing to the mixing desk control room (tac scorpion) is absolutely amazing clean sound !!
it was like change my studio monitors !! absolute fantastic thanks to Igor for this amazing work !! he is an absolutely genius !!
now it's time to finish design the box of the remote control and the front panel
when i finish the unit i post some pictures
at the moment looks like this  ;D ;D ;D ;D ;D ;D ;D ;D

Congrats! Doesn't it feel great to see it come alive? I too had issues with pin 4 on the VGA. So I grabbed pin 4 with needlenose plyers and just pulled them out on each end. Problem solved

 

[Moby]

DIP3 switch SW2 used to adjust  controller/amp's impedance.
In 99% cases, EXCEPT you need very precision level steps, exactly 1db,
it is not necessary to mess with it. You can even go without ZL and ZR relays.

Regarding VU, it's really personal choice but I will never install it in the master controller. Maybe some precision led/peak with more useful functions (peak, rms, bla, bla..) Moving coil? I can't see any reason for it . Again, that's just my 0.2c  8)