Class A transparent Control Room Unit

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SIXTYNINER

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hi guys ,
i'm not satysfied about the quality and clean of the various control room sections onboard on mixing consoles ,DAWS as pro control,control24,mackie presonus ecc.....some days ago i worked on a mastering section about a my friend new album , and the resident engineer of the studio where mastering was made using various fantastic units (as the same ....manley massenburg weiss prism pmc genelec,ecc) but as control room he use a cranesong avocet , i been able to state that much difference between a normal and a class a mastering  control room unit (differnce around 20/25%) the mastering have much sound transparency and detail !! (essential in mixing section but also in tracking)
the other side of "medal" are the price , very expensive......
...then go by diy ,
any one  need to ear the real sound run on his studio and
have info/helps for  make a class A-AB control room unit
with "transparent" and clean out,
are wellcome in this new "race",
some spec required:
3 stereo/dual mono trs/xlr balanced -10k impedance line in
a rotary switch for select source input
a rotary switch 12/24 step for control volume out
a rotary switch for select output destination 10k line out (speskers)
3 stereo/dual mono trs/xlr balanced - 10 k impedance line out
1 mono button/switch for ear in mono 
1 dim/mute button/switch for set out level in half or in mute (possible by a 3 stages on-off-on switch?)
the cherry on the cake will be :
a 2 raw 20 led meter (possible use the 20 led card by picocompressor?)
and a 1 raw 20 led meter for signal phase -/+

any other cool add on are wellcome!

helps available at now:
i have cranesong avocet "brain" pictures if someone want to have simply post a pm with email address
 

SaMpLeGoD

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Hello, I'm pretty intersted in build a control room like Avocet... I work with Protools Control24 and the control room is awful :(
I think if we put some lighted pushbuttons to switch between the speakers, even switch between the inputs, with the option to hear, for some reason more than one source at the same time... what do you think? like that central control on this JLM's Mastering console...
Could you send me the Avocet photos? will be a good start, do you have any schematic of that?
Your mailbox is full  :-\
Cheers,

Eddie
 

DaxLiniere

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Hey guys,

I have built a 3-in, 2-out "mastering-grade switcher", which has been in operation for many years and works reliably.

The unit is built around a special type of relay with "mercury wetted contacts". They have the lowest known contact resistance.
Each relay is SPDT so for stereo balanced, you need 4 relays.

My switcher does not have a gain control, I use RME soundcards which all feature TotalMix; so I control the monitoring level digitally. Perfect.

To get 3 inputs, I simply placed one "set" (of 4) relays on the input of a second "set" of relays and used a 2 pole rotary switch to do the rest. (relays cascaded)

In the past, I've toyed with adding gain control, but I feel the effort to build and then the sonic degradation is a step backwards.

Gain control COULD also be done with this relay method and would probably be the most awesome sounding overkill in such a device. However, once you start researching the topologies (shunt, series, ladder) and then consider how many step positions you would like in your control... you have a LOT of relays.
You should read the advantages and disadvantages of both here: http://diyaudio.co.kr/wwwboard1/data/board1/compare.pdf

It could be done in a kind of "binary form" - 0.5dB attenuator, 1dB attenuator, 2dB attenuator, 4dB attenuator, etc would get you all combinations: 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4, 4.5, 5, 5.5, 6.0, 6.5, 7.0, 7.5
Adding more blocks (8dB attenuator, etc) would be useful too.... BUT each additional stage of attenuation is an extra resistor that's adding theoretical noise to your system. (Even using Dale Vishay's, etc)
You would also need to use a microprocessor to engage each of those attenuator blocks 'cos there's no rotary switch that can save you now :)
 

Gold

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DaxLiniere said:
'cos there's no rotary switch that can save you now :)

Uhh, that's exactly what could save you if you make it into an attenuator. I just had a 10k/5k H attenuator made. It's surely overkill but what the hell, I'm only buying it once. 12 decks for stereo.
 

Rob Flinn

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DaxLiniere said:
Hey guys,
My switcher does not have a gain control, I use RME soundcards which all feature TotalMix; so I control the monitoring level digitally. Perfect.

Does this not mean that the lower volume that you are listening then the less bits you are using ???      I guess this is probably insignificant, but I think I would go with a passive attenuator if I were building this myself.
 

LewKellogg

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;)
I am interested as well. I have been looking at the Dangerous version as well as the Manley. Pictures of the Cranesong would be helpful.
 

DaxLiniere

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@Gold: No, rotary switches don't have mercury wetted contacts. That's the whole point of my post.

@Rob Flynn: (MachineHead Rob Flynn???) No, the volume control is not a bit-depth decimator. If it was, then I'd hear an extremely obvious distortion effect when I did it. Look up "bit crusher vst" for the effect you're describing.
Anyways, I was advocating stepped attenuators, but using the mercury-wetted contacts instead of the gold or silver contacts inside a standard rotary switch.
 

Gold

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Looks like it's time to learn how to program micro controllers. I bought the CMOS cookbook and did some reading on Basic STAMP, PIC ect. My head hurt.

BTW 10k is a high output impedance. That's why I had a 10k/5k attenuator made. It's worth the 6dB loss IMO.
 

Rob Flinn

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DaxLiniere said:
@Gold: No, rotary switches don't have mercury wetted contacts. That's the whole point of my post.

@Rob Flynn: (MachineHead Rob Flynn???) No, the volume control is not a bit-depth decimator. If it was, then I'd hear an extremely obvious distortion effect when I did it. Look up "bit crusher vst" for the effect you're describing.
Anyways, I was advocating stepped attenuators, but using the mercury-wetted contacts instead of the gold or silver contacts inside a standard rotary switch.

Ok I was just checking, but surely your system runs your signal through some sort of algorithm ???  All Im guessing is that if you are going to the length of using mercury relays for you signal switching to achieve the purest of pure sounds, then using a stepped attenuator (using the mercury relays of course) would possibly be purer than he alogorithm  or method that  RME use to attenuate ???? What do you reckon ??  I'd be interested to know more about the RME system if you could give some more detail ?

And no I'm not Rob Flynn machinehead.  Whoever he is should get some spelling lessons so he knows how to spell "Flinn" correctly  ;) ;D
 

Sleeper

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Rob, I'm pretty sure you're correct. I use the RME and totalmix is ITB all the way.
It's great for signal routing, super easy but it's not a remote gain control system.

I don't know about the mercury wetted relay thing, but I could really really hear a difference when I hooked up my badass Shallco Bridged-H with .1 percent Holco resistors. It weren't cheap but it was dead simple to hook up and it makes me feel like Donald Trump with hair when I turn that volume control. So nice.
 

Gold

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Sleeper said:
when I hooked up my badass Shallco Bridged-H with

That's what I ordered minus the Holco's . I figure with only 6 resistors in the signal path at a time 1% is plenty good enough. Since I wanted unequal impedance ratio they didn't know how to make as a bridged H. They did a full H. My attenuator is bigger than your attenuator. I'm usinghttp://www.broadcasttools.com/view_product.php?pid=34 for source selection. I'm hiding it and using shiny metal illuminated push buttons to control it.
 

Igor

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Hi to all!
I can't see any reason to do it CLASS A....
But PASSIVE, yes.
I built a system which is tested by time and many people.
First mastering colsole with this kinda
relay attenuator working about 3 years, and 20-25 units based on same principe
are working without any probs, and claimed as very clean monitoring.
Attenuator's input impedance is 5kOhm, for each + or - input
(it is completely balanced), and output impedance changes from 0 to
worst case about 1.7K....

I think to offer a bit cutted version as a kit,
but please mind it is not a cheap system.
It can come up in total about EUR200...280 per kit.

Controller's surface:

plexi_contr_small_F.gif


4 inputs, 2 speakers outs, sub out, mono, dim and talkback with trim offset,
1 db steps, 63db of level controll+cut, audio passes thru  relays and metal film resistors only...
 

matta

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Hi Igor,

Looks great! You used to have pics of the more advanced version, but i can't seem to find them, they looked killer!

Just a question... is the trim available on each input? Just nice sometimes to be able to trim an input of say a CD to match similar levels to DAW when switching between inputs.

What would be nice is a CUE out so that you can send the same input to a separate CUE output to a headphone send for those of us using a monitor controller to do so ala Dangerous Music/Presonus Central Station etc.

Are all the inputs balanced? Might be good to have at least one input as an unbalanced -10 for consumer CD players/ipods etc.

Any chance you could add a digital input? Hah hah.

What would the kit contain? I don't think 200-280 Euros is THAT much if the unit is solidly built (no doubt there) and is flexible (as it seems it will be).

Cheers

Matt
 

Igor

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You used to have pics of the more advanced version, but i can't seem to find them, they looked killer!

Yes, this new forum search engine is absolutely FUBARU.
Got lost in new enchanced appearance...now forum looks like Behringer.

You can see 1st CRM version there:
http://www.groupdiy.com/index.php?topic=17757
http://img.photobucket.com/albums/v436/IJR/12082006012.jpg
and second version is there:
http://www.groupdiy.com/index.php?topic=18346

Some stuff there:
http://www.groupdiy.com/index.php?topic=14474

Just a question... is the trim available on each input? Just nice sometimes to be able to trim an input of say a CD to match similar levels to DAW when switching between inputs.
Yap. With use of uP-controller, it is possible
to add TRIM value to same attenuator while switching beetween inputs.
Compare to analog systems with few pots etc....

What would be nice is a CUE out so that you can send the same input to a separate CUE output to a headphone send for those of us using a monitor controller to do so ala Dangerous Music/Presonus Central Station etc.

Yes, there's "monitor" output used as meter feed, it is between inp. selector and level attenuator.

Are all the inputs balanced? Might be good to have at least one input as an unbalanced -10 for consumer CD players/ipods etc.

Connect 3 to gnd :)

Any chance you could add a digital input? Hah hah.

Enough!!! ME NOT TOUCHING THIS DIGITAL.
WHERE IS TWISTED EVIL SMILEYYYY???????????????

Seriously, it is easy to connect SPDIF receiver to D/A, locked on SPDIF clock.
There's a lot of such projects. It won't come neither Apogee nor Benchmark or Lynx...
in other words, not high quality stuff...then, not worth my time investment :)
Or, buy from evilbay for cheap kinda Audio Alchemy DAC with reclocking (OT, just love them)

What would the kit contain? I don't think 200-280 Euros is THAT much if the unit is solidly built (no doubt there) and is flexible (as it seems it will be).

PCB's, relays, MF resistors, pre-programmed PIC, some misc stuff which is hard to get.
Add XLR's, some Mouser/Farnell parts, VGA upto 20m cable, 12V switching supply,
case (PURUSHA!!!!) and nice control's box (wood pannels at sides please :)
I have to calculate final value.


IMHO, most sexy metering is:
http://www.groupdiy.com/index.php?topic=29839

I have 10-segment LED phase meter which is easy to hook to plasma at side...
 

matta

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Thanks Igor,

This looks beautiful!

crm4.jpg


Yap. With use of uP-controller, it is possible
to add TRIM value to same attenuator while switching beetween inputs.
Compare to analog systems with few pots etc....

Nice!!!

Yes, there's "monitor" output used as meter feed, it is between inp. selector and level attenuator.

Great! I assume the TB is also routed to the monitor/cue out to aid in communication from the CTR Room?
Also how is TB achieved? Are you using an integrated electret mic like most are (quite handy) or is is a separate mic input that needs to be driven from a mic pre?

Connect 3 to gnd :)

Hah hah!!!

ME NOT TOUCHING THIS DIGITAL.
WHERE IS TWISTED EVIL SMILEYYYY???????????????

Seriously, it is easy to connect SPDIF receiver to D/A, locked on SPDIF clock.
There's a lot of such projects. It won't come neither Apogee nor Benchmark or Lynx...
in other words, not high quality stuff...then, not worth my time investment :)
Or, buy from evilbay for cheap kinda Audio Alchemy DAC with reclocking (OT, just love them)

Indeed, better to get a standalone DAC and then feed the analog outputs into the Monitor unit than compromise on quality.

PCB's, relays, MF resistors, pre-programmed PIC, some misc stuff which is hard to get.
Add XLR's, some Mouser/Farnell parts, VGA upto 20m cable, 12V switching supply,
case (PURUSHA!!!!) and nice control's box (wood pannels at sides please :)
I have to calculate final value.

Cool, but it seems all in it could/should be built for under 400-500 Euros, still alot more economical than many of the current commercial offerings... and better quality.

I know that this controller is out of the spec of what the OP posted but is anyone feeling the love for this unit form Igor? I know a few expressed interest some time back when it was originally posted, if not then maybe I should start a new thread to get this back on track but I think Igor is onto something great here!

Cheers

Matt
 

Igor

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Great! I assume the TB is also routed to the monitor/cue out to aid in
communication from the CTR Room?
Also how is TB achieved? Are you using an integrated electret mic
like most are (quite handy) or is is a separate mic input
that needs to be driven from a mic pre?


Nope. Separate circuit (talkback combiner) is used.
Sometimes we need to listen in phones separate mix from controll room :)
Then, just feed say soundcard outs 15-16 into talkback combiner,
and take output mixed with talkback signal (when TB pressed) to phoneamp.
There's a balanced input, electret mic amp, summing circuit...quite simple.
I had no any patience to add audio power supply, and micropower
+5->+/-15 v converter used ($8-15).

Schem (old one with some errors, but possible to get idea):

http://i251.photobucket.com/albums/gg291/diy33609/ph_tbk.gif

Don't relate to lower part of schemo, it is relay's driver and SPI receiver.

Cool, but it seems all in it could/should be built for under 400-500 Euros, still alot more economical than many of the current commercial offerings... and better quality.

Quality yes, economical...yes, it is more or less in 400-600EUR range to DIY

Hey Igor, what type of attenuator network does it use?

First, I liked your signature!!!!

laser.jpg


Attenuator...old good known trick, 1-2-4-8 constant input impedance....
IIRC MCS from this forum used same (in today's world, info
spreads too fast, and we did it at a same time)...
I used 5k impedance. On old forum there were some calcs and equations.
Here is the idea in Russian I found 4-5 years ago:

att_small.gif


 

DaxLiniere

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London, UK
Ah, so it is like my idea of a binary-type thing. (1+2+4+8, etc)

My only concern with that method is that with maximum attenuation, your audio is travelling through ALL resistors. Metal film or not, this is still adding noise.
(It's just another reason I like using my RME for level control)

I do love the look and functionality of your kit though, super-duper nice! :)


PS. Thanks for the signature comment, in 4 years, not one person has commented ;)
 

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