Monitor Controller

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Hi, last two days I built an MC624 Monitor Controller successfully  :) :)

Pictures can be found here: https://www.dropbox.com/sh/5emp3xi7px24dc6/AACoCecGIMjkwpo5z1wb3s0ta?dl=0

Thanks a lot for this phantastic kit.

All is working fine.

One issue is, that on Headphone out theleft - right  leves are not identical.
I noticed this on listening and then tested it out:

Fed the Controller with 1khz 1.274 V and measured Values on HP out

Pot Position Tip V trms Ring V trms
1 0.0002 V 0.0187
2 0.0502 0.0546
3 0.0956 0.0926
4 0.1400 0.1296
5 0.1956 0.1722
6 0.2478 0.2302
7 0.3333 0.3175
8 0.4751 0.4600
9 0.6879 0.6810
10 0.8577 0.8573

You see, the values differ a lot- maybe  a bad 10K pot.
Is it possible to replace with dual gang pot with fixed values Switch?
Which part would you recommend?


Further question arose:
I try to measure Trms V Values @ 1Khz on XLR in and XLR out but I do not get usable values. Only on unbalanced Jack out.
There my meter detects 1khz only on 00 to -04 Setting.

Voltage values are equal on both channels on unbalanced Jack out.


Thanks a lot for Support.

Erich T
 
The headphone level is set by a "logarithmized" dual gang linear pot and does not have the same accuracy as the main level which is done by relays.
Your figures seem  a bit "all over the place" and I am going to send you a replacement pot to check if it gets better.
It would be possible to use a 2x12 rotary switch and make a stepped attenuator. You will need a rather small device to fit the available space.
The AC voltage on XLR's must be measured between pins 2&3.
 
Thanks for fast answer.

I would really prefer a stepped pot for headphone. My Mytek 8/192  also has one  on HP  and i really like  it.
I would be very grateful if you could source a matching dual gang stepped pot.

I do not understand why i firstly can measure Hz and trmsV with my Multimeter on XLR (pin 2-3) Cable befor plugging into Monitor Controller, but with cable plugged in I get other values  and no Hz value on the MonitorController XLR Pins (2/3). This also on XLR out....
I really want to measure values on both Channels to be shure that there is no channel drift.

Edit:
Today I measured again.  Values on XLR out are o.k.  Must have been  a contact issue with my DMM.
What I do not understand why my DMM only  shows 1khz on att steps 00 to - 03. From -04 to -63 it doesent Show Frequenzy.

Below Values on XLR out:

Step CH1 In 1.280 V Ch2 In 1.280 V
00         1.2594 1.2580
-01 1.1248 1.1240
-02 1.0003 1.0000
-03 0.8930 0.8919
-04 0.7916 0.7905
-05  0.7073 0.7062
-06 0.6314 0.6300
-07 0.5635 0.5600
-08 0.5012 0.5016
-09 0.4474 0.4479
-10 0.3992 0.3995
-11 0.3564 0.3564
-12 0.3150 0.3148
-13 0.2813 0.2812
-14 0.2500 0.2508
-15 0.2239 0.2238
-16 0.1995 0.2002
-17 0.1781 0.1788
-18 0.1590 0.1596
-19 0.1418 0.1424
-20 0.1255 0.1254
-21 0.1114 0.1118
-22 0.0993 0.0996
-23 0.0889 0.0889
-24  0.0789 0.0790
-25 0.0704 0.0705
-26 0.0628 0.0628
-27 0.0558 0.0559
-28 0.0492 0.0492
-29 0.0434 0.0439
-30 0.0387 0.0390
-31 0.0344 0.0347
-32 0.0296 0.0298
-33 0.0263 0.0264
-34 0.0233 0.0234
-35  0.0206 0.0209
-36 0.0181 0.0183
-37 0.0161 0.0162
-38 0.0143 0.0144
-39 0.0125 0.0127
-40 0.0110 0.0112
-41 0.0096 0.0099
-42 0.0085 0.0087
-43 0.0074 0.0077
-44 0.0064 0.0066
-45 0.0056 0.0058
-46 0.0049 0.0051
-47 0.0043 0.0044
-48 0.0037 0.0039
-49 0.0033 0.0034
-50 0.0025 0.0028
-51 0.0023 0.0023
-52 0.0019 0.0019
-53 0.0016 0.0016
-54 0.0013 0.0013
-55 0.0010 0.0010
-56 0.0008 0.0009
-57 0.0006 0.0006
-58 0.0005 0.0005
-59 0.0004 0.0004
-60 0.0003 0.0003
-61 0.0002 0.0002
-62 0.0001 0.0001
-63 0.0000 0.0000

I think these values are really o.k. - bearing the inaccuracy of  DMM in mind ..

For HP stepped Pot replacement I found this one:
http://www.ebay.com/itm/DACT-Type-SMD-Stepped-Attenuator-21-step-Volume-control-pot-D-Shape-Shaft-/181534837651?pt=LH_DefaultDomain_0&hash=item2a4451cb93

better part is always welcome.

I checked dimensions: max diametre could be 29 mm to main PCB. Front PCB could be cut out.




I want to say again, this is a phantastic kit and it is really a pleasure to build

Erich T
 
This 21 steps attenuator looks very interesting.
It almost fits the available space , only requiring filing half a mm from the side of the front PCB.
Use the 10K one. The attenuator surely has a log law so you should remove R103 and R119 which were used to give  the linear pot a log response.

Please keep us posted about your results.
 
etiefenthaler said:
For HP stepped Pot replacement I found this one:
http://www.ebay.com/itm/DACT-Type-SMD-Stepped-Attenuator-21-step-Volume-control-pot-D-Shape-Shaft-/181534837651?pt=LH_DefaultDomain_0&hash=item2a4451cb93

better part is always welcome.

I checked dimensions: max diametre could be 29 mm to main PCB. Front PCB could be cut out.


I want to say again, this is a phantastic kit and it is really a pleasure to build

Erich T

Hello Erich,

Did you try this stepped pot replacement for HP ?

Thanks !

Matteo
 
Hi Matteo,

Yes I installed this stepped pot and desoldered the two resistors.
Its working great.  Mounting shaft diameter is too small so i had to make a bush for proper  fitting.

Besides that,  one day surprisingly  I had a replacement pot from JPK in my mail. Awesome service!
Kudos

At the moment I am happy with the low cost stepped pot.

Erich

 
Hi Erich, thank you for your feedback !

I will contact Jean-Pierre for this stepped pot alternative.

All the best,
Matteo@IM
 
Hi,

Finally, I have built the monitor controller.  It is just GREAT.

However, I would like to ask two things.
1.  Is it possible to use OP604 instead of OP134?  The sound quality would be much more superior if changing that?  They are directly interchangeable?

2.  I would like to add a meter for the monitoring.  Would you mind pointing me what part / product I can buy for 624?

Kinglok, Fong

 

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1. Yes you can use OPA604 in place of OPA134, they are compatible. I doubt you can hear a difference but I could be wrong.

2. You can use any meter as long as it is buffered (and powered). Are you looking for moving coil or LED?
 
Just wanted to say Thanks! Amazing kit, had everything needed and went together easy. I can already hear the difference from my last setup.

IR Remote control works great too  8)
 
My personal experience with stereo pots is that they never match.

The same thing happens in the Dangerous Monitor ST on all of the physical pots.
When you are in the lower range of the pot, the stereo is way off balance.
Had the same with a SPL stereo monitor box, had to keep the DIM on the be in the right range of the pot.
It just has to be expected I guess.

These stepped pots are more acurate but they feel strange, no?
 
j.frad said:
My personal experience with stereo pots is that they never match.

I've been working on a monitor controller (scratching an itch, you know), and I went with the PGA2320 chips instead of stereo pots for exactly that reason.

-a
 
For anyone interested, I have developed a wired desktop remote design for this. 

I've posted about it here:  https://groupdiy.com/index.php?topic=66236.0
 

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chadblinman said:
For anyone interested, I have developed a wired desktop remote design for this. 

I've posted about it here:  https://groupdiy.com/index.php?topic=66236.0
A very nice project you have here,exactly what I was after,thank you for sharing.
I wished I could do this for my controller,but sadly I have no idea what's going on when it comes to digital stuff like this.


Best,


Udo.
 

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