passive mastering console with PICS

[dagoose]

I built a passive, relay based masteringconsole some time ago and i always wanted Mid/Side and so i took out the iron and modded it to the console of my dreams.  ;D

Is has 6 inserts, 3x compressor, 3x EQ with flippable order (comp>eq eq>comp) by the push of a button.
The inserts are selected by 2x 3 steps lorlins powering relays.
Both eq and comp have a dedicated hard bypass.
Then we have the mid/side option (wayne kirkwood ms matrix) that can be inserted in the EQ path or compressor path by the push of a button, so ms eq or ms compressor all with full bypass, order etc functionality! (it has 16 relays just for the insertion)
Ofcourse it is fully balanced all the way and inserts are done with 24 6,3mm jacks in the back of the panel, in and out are XLR's.
The psu is external, 12v for all relays and + and - 18v for the MS matrix, both have their own tranny's and psu.
In total it has 63(!) relays to make everything work, all done on veroboard!  8)
All settings are visual by the color of the buttons, they have 2 color leds so when red it is in bypass and when green (comp) or yellow (eq) is lit you can see it's active, same for MS, green is comp, yellow is ms eq.
The front is done with lasertran but i wll probably go for mittelbronze schaeffer panel soon.

It is totally clean and reall works like a charm and i'm really proud of it!

ok... time for some pics...

 

[JoleFIN]

Really nice!

 

[AUDIO-ON]

Looks relly awesome...
Respect

 

[kambo]

what brand are those lorlin type switches?

 

[Ptownkid]

Needs some more relays! Just kidding, great job!

 

[user 10827]

sheesh kebab! looks fab man..

I built one of those MS boards too...highly recommend those..

 

[kambo]

m/s boards are sold out

 

[dagoose]

what brand are those lorlin type switches?

well... one is a lorlin, the other is a gold plated version from musikding or banzai.
I had to replace the regular with the goldplated but now that i see the pic myself i forgot but now it's already in my rack so i'm not going to replace it anyway.  ;D

 

[ChrioN]

looks pro! I want one  ;D

 

[Igor]

Cool. Very nice! Breadboard and low crosstalk router...ok. I think it is possible.
Still not tried
Some attension needed to wiring.
Did you separated left and right boards or everything done at one board?

Can share some stuff on ms, if this can be usefull....
The MS circuit from Wayne is not best crosstalk-wise, about -70db @10kHz practiacally.
There's not enough 0.1% precision of resistors of THAT chips,
however, maybe you can find quartet which will have perfect match.
Anyway, MS is mostly used for effect purpose at our days and THAT chips are very clean...
70db can be tolerable.
As well, another prob with Wayne's m/s is keeping gain structure 0dbin/0db out,
i.e. keep the whole chain (matrix/rematrix) at unity gain.
In other words, "ms and 3 db" stuff. IMHO it should be like lr/ms(-3db)->(-3db)ms/lr
or at least lr/ms(-6db)->ms/lr(0db). This way less chips used-> better sound.
Dale velvet resistors or Roderstein are wellcome.
Trimpot paralleled with low value metal film resistors will give last db's of separation
in range -70....-90 db.

 

[dagoose]

Cool. Very nice! Breadboard and low crosstalk router...ok. I think it is possible.
Still not tried
Some attension needed to wiring.
Did you separated left and right boards or everything done at one board?

Can share some stuff on ms, if this can be usefull....
The MS circuit from Wayne is not best crosstalk-wise, about -70db @10kHz practiacally.
There's not enough 0.1% precision of resistors of THAT chips,
however, maybe you can find quartet which will have perfect match.
Anyway, MS is mostly used for effect purpose at our days and THAT chips are very clean...
70db can be tolerable.
As well, another prob with Wayne's m/s is keeping gain structure 0dbin/0db out,
i.e. keep the whole chain (matrix/rematrix) at unity gain.
In other words, "ms and 3 db" stuff. IMHO it should be like lr/ms(-3db)->(-3db)ms/lr
or at least lr/ms(-6db)->ms/lr(0db). This way less chips used-> better sound.
Dale velvet resistors or Roderstein are wellcome.
Trimpot paralleled with low value metal film resistors will give last db's of separation
in range -70....-90 db.

Thanks!  8)

The left right is not on seperate boards but the wires and relays are pretty much seperated from each other. The closest the l and r come in eachothers path is something like 5mm. I haven't really measured the crosstalk but it's at least 90db since when i was connecting things again in my studio and had left/right muted for testing l and r connections i didn't have any crosstalk on the meters in wavelab which are set to 90db.
All 12v wires for the coils are at least 1cm away from the linelevels, all audio is on the bottom of the board and the 12v's goes directly to the top of the board to avoid lines crossing.
It is really clean, even cleaner then i expected it to be in the first place since there is a lot of wiring going on. (forgot to took pics of the wiring on the bottomside of the board.)

Concerning the MS, i think it does a really good job but what i think is quite anoying is when i go for MS comp the mid channel has a couple of db of extra GR because of the output of the M and S is lower.
I was also thinking of something like dropping level on the output of the M and going up again after the processing and the oposite for the S channel.

Any idea how i could do this with the wayne kirkwood circuit since there are no resistors in the circuit itself? is the best thing do do is skip the 1246/1646 circuits and go for something else to balance again?

 

[radiance]

what i think is quite anoying is when i go for MS comp the mid channel has a couple of db of extra GR because of the output of the M and S is lower.

Why not lowering the threshold (or up de gain) from the side channel?

Any idea how i could do this with the wayne kirkwood circuit since there are no resistors in the circuit itself? is the best thing do do is skip the 1246/1646 circuits and go for something else to balance again?

It's all off the shelf chips. Like Igor said, you need to fabricate something yourself using precision resistors when you want to achive this...
It would be nice to have a -6dB MS encoder output signal so the inserted device would not have to deal with a +6dB MID (m) signal.
Especially when using modersn near 0dB levels...
OTOH, the signal level will have to be lowered somewere. I don't care whether it's done in hardware (i.e. in the m/s circuit somewere) or in software by lowering the signal in your DAW or so.
Either way, you WILL want to use dual mono processing gear when working in M/S mode.

 

[zayance]

Very nice indeed, and just to let you know, if you bought the Modushop case directly, you can ask for having the slimline without the IEC perforation if you want, i actually wanted to fill it with a metal plate as you did, but when i asked they said no prob, just leave us a note when you purchase, and you'll have backplate unperforated, just for info....

 

[hobiesound]

ongeloveloos vet.... !

 

[dagoose]

what i think is quite anoying is when i go for MS comp the mid channel has a couple of db of extra GR because of the output of the M and S is lower.

Why not lowering the threshold (or up de gain) from the side channel?

Any idea how i could do this with the wayne kirkwood circuit since there are no resistors in the circuit itself? is the best thing do do is skip the 1246/1646 circuits and go for something else to balance again?

It's all off the shelf chips. Like Igor said, you need to fabricate something yourself using precision resistors when you want to achive this...
It would be nice to have a -6dB MS encoder output signal so the inserted device would not have to deal with a +6dB MID (m) signal.
Especially when using modersn near 0dB levels...
OTOH, the signal level will have to be lowered somewere. I don't care whether it's done in hardware (i.e. in the m/s circuit somewere) or in software by lowering the signal in your DAW or so.
Either way, you WILL want to use dual mono processing gear when working in M/S mode.

Lowering the threshold of the M channel is indeed possible (when compressing) and that is what i will do right now. The thing is that for AB'ing stereo/ms it's quite anoying to set the threshold back again, then it's not really AB'ing to me. When using MS eq it's no problem because the input can handle the extra amount of gain because my DA converter is set to someting like -2db anyway. It's just the compression that i would like to change but it's also not REALLY a must since i think i will end up using 80% ms eq of the maybe 30% MS processing anyway. I'll think i'll end up using 70% stereo processing though now that i have the option it might be a bit more.. time wil tell.  ;D

What i understand concerning the that's is that they have precision resistors built in so no need for fine tuning that circuit though i'm not sure HOW precise they are ofcourse.
Maybe i'll try to built something with prec. resistors on the M out to get something like -6db and an opamp circuit on the M input to get back to unity gain again.

This is maybe a noob question, why is it so important to have precision resistors anyway? Is it because of the MS en/decoding +/- caluculations? if that is the case then after and before the 1240's it doesn't matter that much to me anyway or am i missing something here?

 

[abbey road d enfer]

what i think is quite anoying is when i go for MS comp the mid channel has a couple of db of extra GR because of the output of the M and S is lower.

Why not lowering the threshold (or up de gain) from the side channel?

Any idea how i could do this with the wayne kirkwood circuit since there are no resistors in the circuit itself? is the best thing do do is skip the 1246/1646 circuits and go for something else to balance again?

It's all off the shelf chips. Like Igor said, you need to fabricate something yourself using precision resistors when you want to achive this...
It would be nice to have a -6dB MS encoder output signal so the inserted device would not have to deal with a +6dB MID (m) signal.
Especially when using modersn near 0dB levels...
OTOH, the signal level will have to be lowered somewere. I don't care whether it's done in hardware (i.e. in the m/s circuit somewere) or in software by lowering the signal in your DAW or so.
Either way, you WILL want to use dual mono processing gear when working in M/S mode.

You're opening a big can of worms here. The debate about -3 or -6 at M/S is the same as the debate over -3 or -6 pan-law. Just like DAW's designers have decide to provide users wit the possibility to adjust the pan-law, I reckon a modern M/S matrix should have level adjustments. The ideal would be simultaneous complementary cut of the L/R to M/S and boost of the M/S to L/R.

 

[radiance]

The thing is that for AB'ing stereo/ms it's quite anoying to set the threshold back again, then it's not really AB'ing to me. When using MS eq it's no problem because the input can handle the extra amount of gain because my DA converter is set to someting like -2db anyway.

Sorry, I don't get it. I know that in the early days the m/s technique was mostly used to compensate for the not so well matched mono eq's or comps. I don't see the point in MS processing when you're going to use the same EQ or comp setting for side and mid signals.
For me, the power of MS processing lies in the fact that you can apply different compression (or EQ) for side and mid. Hence, AB-ing between MS and srtereo mode makes no sense to me...

What i understand concerning the that's is that they have precision resistors built in so no need for fine tuning that circuit though i'm not sure HOW precise they are ofcourse.

Well, you can check the data sheet http://www.thatcorp.com/datashts/1240data.pdf
It says "the R3/R4 ratio is trimmed to within ±0.005 % of the R1/R2 ratio". So with the THAT1240 it's as close as 0,5 OHM. To me it seems pretty well matched and I don't understand what Igor means by

There's not enough 0.1% precision of resistors of THAT chips

Igor, can you explain what it is exactly you mean? Do you mean that the resistors in 1 THAT IC are matched but that the value will vary slightly  in each THAT IC?

Maybe i'll try to built something with prec. resistors on the M out to get something like -6db and an opamp circuit on the M input to get back to unity gain again.

Basicly you'll have to rebuild the encoder and decoder part using precision resistors and an opamp to achieve that.

This is maybe a noob question, why is it so important to have precision resistors anyway? Is it because of the MS en/decoding +/- caluculations? if that is the case then after and before the 1240's it doesn't matter that much to me anyway or am i missing something here?

They are important. For example, the side signal is achieved bij R-L. If R is slightly louder due to mismatched resistors the mid side part of both R and L will not cancel each other out completely. 

 

[W DeMarco]

Did you get the chance to use some relays?  That would be sweet!!

 

[radiance]

Reading through this thread my post seem as if I don't think Waynes MS board is the real deal.
Well, I build this MS encoder / decoder in my mixer and I can say that I don't hear any difference when I switch the MS encoder and decoder  in the signal path.
I did not use Waynes pcb and in my version I don't have the NE5532 in the signal path...dunno if that makes much of a difference though..

 

[Twenty Log]

I too am wondering what Igor meant with the 0.1% too... I could be wrong but I wonder if it is the datasheet also saying that the absolute resistance lot-to-lot may vary +/- 30%, which may not be too critical at "first look" since they are laser trimmed and the matching is what is critical...  But then there is that pesky temperature coefficient (TCR) (and insertion absolute impedance)....  higher valued resistors would potentially "drift" more with the TCR and temperature change...

The good news is that hopefully the IC layout designer for the THAT chips has probably placed the matched resistors near each other with the appropriate "dummies" (if their process needs dummies) nearby on the microchip die so they probably track thermally ok...  But I am having a hard time finding the TempCo (TCR) of the silicon-chromium material, with only white papers that denote -1500ppm/C to +500ppm/C with 27% chromium content being the best  TCR...

But I am also confused since Vishay has some super precision stuff with 0.05ppm/C TCR and 0.001% matching...  Might just be superior binning and sorting coupled with film uniformity on the wafer run? (and of course PRICE!)

I have been avoiding trimmers in my MS design since the TCR is +/-100ppm even with a 150 ohm trimmer, the temperature rise of 20C ~ 40C range would dump the CMRR and crosstalk into the lower 70 dB and upper 60 dB range (in theory)...  Maybe there are better trimmers out there for TCR, but then arises the issue of calibration every year (this is why, when we used to design telcom test equipment we avoided trimmers and went with software calibration; less opening of the box; maybe only slightly less downtime).

As it is, a 20C change renders performance into the 70s dB range with 5ppm/C resistors using a 10k precision resistor for the design here ..

I have been finding that the insertion loss in relays adds about 0.5dB (+/-) of degradation for contact resistances less than 0.05 ohms when considering a 10k precision and nominal system impedance (just using the simplified formula of CMRR is 20 log (resistor match tolerance) where the 0.05 ohms of relays when compared to 10k of precision tolerance moves the tolerance a little bit).

The Backbone mentions that it has trimmers, which is all well and good to calibrate on the bench at one temperature, but they also mention that some of the trimmers (not all) should be tweaked once a year or so... Granted, it may not be  the trimmers for the match, rather perhaps trimmers to offset drift and aging?  I wonder about the specs on the Backbone over temperature...

Nice pics indeed!  I like the smooth and clean routing abilities for the different processors...