Build Thread:MS76

[Gustav]

Hey everyone (and particularly Gustav),

I'm putting together a BOM for this project using the schematic and the board itself. I'll be happy to share it with the group once I've got it completed, as I believe (and hope) that it will be helpful for those of us that only have the boards (no full kit), since a published BOM does not exist.

To that end, I have a few questions that would really help me finish it up. Apologies that there are so many, but I hope you can help!

1. What is the value/taper/etc of the blend pot? I don't actually see it anywhere on the schematic, but I might just be blind.
2. The 10nF cap marked "(HP)" has an asterisk associated with it. Presumably this value can be adjusted to affect the frequency of the HPF (I'm just guessing). Is there any reason to include other options or perhaps clarifying information in my BOM, since an asterisk that leads nowhere tends to cause confusion?
3. The XLRS -- is there a product number for the male and female ones that will fit this footprint?
4. Is it alright to use 1n4004 diodes for all 1n400x designations in this design? Seems easier than ordering multiple varieties if a builder doesn't have any of these on hand.
5. Is there a meaningful difference between the FD333 and the more readily-available FDH333? Looking briefly at datasheets, they appear to be interchangeable, but I'd hate to assume and then be wrong.
6. The 2N5457 transistors seem to be a bit tricky to find (I grabbed some from Reverb, but who knows if other builders will have luck). I read that the PF5102 is a reasonable substitute, at least in guitar pedals, and I also found it easier to locate sellers for that one. Would that (or a different one) be acceptable in this design?
7. If substituting the 7912 for the 7910 as recommended in this thread, are any changes required for other components on the board?
8. For the two diode bridges in the PSU, are there any considerations when it comes to choosing one? The ones in the pictures in the build guide seem to be obsolete or otherwise unavailable. Will a W08G work? (I have a bunch lying around, so I'm hoping yes!)

9. Slightly off the topic of the BOM, but since the board is clearly meant to be supported in the rear by the XLR connections and there are no holes for stand-offs on that side, is it possible to get an fpd file or mechanical drawing of the rear panel so that we can have them made accordingly? This seems preferable to drilling new holes in the board lol.

Again, sorry for the numerous questions, and I hope that I'm not asking for redundant information that has already been covered in this thread (I did look, I promise!). Hopefully it is worth the trouble so that we can have a thorough and accurate BOM for these boards...

These were only sold as kits, and when I stopped those sales, I offered the spare boards. There were about 10, and I found a pile of another 20 when I cleared out the PCB storage. I dont think there is a huge need for a shared BOM based on that.

To try and help you.

1. 2 x 10K lin will do.
2. You are correct, it sets the SC HP. Its rather high "stock", but you can change as you wish.
3. They are just neutrik PCB mount XLRs.
4. Yes - 4003 is fine throughout.
5.You can use both.
6. No idea - youd have to try, but again, we dont really need a public BOM, so just find the 2n5457 for your build, and dont worry about universal availability.
7.Up the trimmer values a little - next step in line will be fine.
8. As long as the minimum voltage and amperage rating are fine, you will be fine. Your mentioned part is rated 800V, 1.5a, which is more than enough.
9.Lay board on bottom of case, punch markers, and drill, if you want to add support studs.

Gustav

 

[James Meder]

so ratios and compression move correctly, but the reference is off.

And all voltages work out.

So, at this point, I would look for an incorrect resistor value, either causing your input gain to be way too hot, or to the SC/in the ratio, causing the SC reference to be way too hot.

Did you measure resistors as you put them in? You mention some missing, so if you were missing a value, start by checking if that/those values went into the board somewhere incorrectly, possibly the same basic value, but incorrect multiplier (100R instead of 100K i.e.).

If the 20:1 ratio is within normal range, just bites a little, it could be a 560R/560K swap on the ratio board, for example.

You could also check, if the ratios are moving correctly by backing off what you send, if thats the case, its in the threshold compensation portion of the ratio switch.

Hope that helps move you forward trouble shooting.

Gustav

I'm checking back here after having to take some time away from the build due to work.

I have tried backing off the level of what I send and it doesn't change how the ratios react. It just does little to no gain reduction on all ratio settings after following the calibration setup. The level drops when I engage the 'comp in' and the threshold gets way low on the lower ratios - even when giving it no signal.

I did measure the resistors when I put them in but I could have mixed something up so I'll go through those.
I have the pcb diaphragm for the main board from an earlier post, but could I get the one for the aux pcb's please?

 

[Gustav]

I'm checking back here after having to take some time away from the build due to work.

I have tried backing off the level of what I send and it doesn't change how the ratios react. It just does little to no gain reduction on all ratio settings after following the calibration setup. The level drops when I engage the 'comp in' and the threshold gets way low on the lower ratios - even when giving it no signal.

I did measure the resistors when I put them in but I could have mixed something up so I'll go through those.
I have the pcb diaphragm for the main board from an earlier post, but could I get the one for the aux pcb's please?

Ok!

https://www.pcbgrinder.com/pcbsandparts
Documents folder/MS76.

AUX board overlays (I "cut" it out of the main schematic to separate the board layout, but kept the placements for overlay reference).

Gustav

 

[James Meder]

Ok!

https://www.pcbgrinder.com/pcbsandparts
Documents folder/MS76.

AUX board overlays (I "cut" it out of the main schematic to separate the board layout, but kept the placements for overlay reference).

Gustav

I can't find it in there. I'm hoping for something like this:

 

[c1184701]

I'm checking back here after having to take some time away from the build due to work.

I have tried backing off the level of what I send and it doesn't change how the ratios react. It just does little to no gain reduction on all ratio settings after following the calibration setup. The level drops when I engage the 'comp in' and the threshold gets way low on the lower ratios - even when giving it no signal.

I did measure the resistors when I put them in but I could have mixed something up so I'll go through those.
I have the pcb diaphragm for the main board from an earlier post, but could I get the one for the aux pcb's please?

Hi James, I'm still certain we have the same issue. Apologies for not posting more, I have also been busy with work.

I have made some progress with my unit, and I can now get it operating correctly, although the fix is a bit unusual... I'm hoping you would be up for seeing if you get the same results with your unit.

With my unit in 2:1, the meter is buried to the left, and there is very little output. If I physically touch the top of the BC107 next to the 6-pin connector (I've highlighted it on the attached image) the meter springs back to zero where it should be. I can send drums through, and now the unit is compressing properly at all ratios, provided I keep my finger on the top of that transistor.

I know it seems unwise poking around with your fingers, but this component only has 15V DC on it, it won't cause you any harm.

 

[Gustav]

Hi James, I'm still certain we have the same issue. Apologies for not posting more, I have also been busy with work.

I have made some progress with my unit, and I can now get it operating correctly, although the fix is a bit unusual... I'm hoping you would be up for seeing if you get the same results with your unit.

With my unit in 2:1, the meter is buried to the left, and there is very little output. If I physically touch the top of the BC107 next to the 6-pin connector (I've highlighted it on the attached image) the meter springs back to zero where it should be. I can send drums through, and now the unit is compressing properly at all ratios, provided I keep my finger on the top of that transistor.

I know it seems unwise poking around with your fingers, but this component only has 15V DC on it, it won't cause you any harm.

Please measure from pin 1 on your XLR to chassis.

Do you have continuity/very low (a couple of ohms) resistance on the meter?

Gustav

 

[Gustav]

I can't find it in there. I'm hoping for something like this:

 

[James Meder]

Hi James, I'm still certain we have the same issue. Apologies for not posting more, I have also been busy with work.

I have made some progress with my unit, and I can now get it operating correctly, although the fix is a bit unusual... I'm hoping you would be up for seeing if you get the same results with your unit.

With my unit in 2:1, the meter is buried to the left, and there is very little output. If I physically touch the top of the BC107 next to the 6-pin connector (I've highlighted it on the attached image) the meter springs back to zero where it should be. I can send drums through, and now the unit is compressing properly at all ratios, provided I keep my finger on the top of that transistor.

I know it seems unwise poking around with your fingers, but this component only has 15V DC on it, it won't cause you any harm.

I'm really surprised but mine does seem to start working correctly as you mention when I place my finger on that transistor.

Please measure from pin 1 on your XLR to chassis.

Do you have continuity/very low (a couple of ohms) resistance on the meter?

Gustav

Yes - I have a reading of 11ohms. What does this mean?

Thanks for the pdf, that's perfect. I'm going to go through and see if I misplaced any resistor values.

 

[c1184701]

Please measure from pin 1 on your XLR to chassis.

Do you have continuity/very low (a couple of ohms) resistance on the meter?

Gustav

Hi Gustav, yes I have continuity from pin1 to chassis, under 1 ohm resistance.

I'm really surprised but mine does seem to start working correctly

Thanks for testing that James

 

[Gustav]

I'm really surprised but mine does seem to start working correctly as you mention when I place my finger on that transistor.



Yes - I have a reading of 11ohms. What does this mean?

Thanks for the pdf, that's perfect. I'm going to go through and see if I misplaced any resistor values.

It could be you are making the connection for a missing reference, so wanted to see if you have chassis connection on the GND

It could also be that you are skewing a reference, and thereby getting it into range, but messing up the reference, and just by chance being "spot on", relative to some build error, seems very unlikely.

Not sure here - one of those things where it could poke me in the eye, if I was sitting with it, or did 2-3 measurements to check, but Im not seeing it right now.

Gustav

 

[noisear]

Hi there,
I have another "problem-child" MS76 here on my work bench. I finished it a year ago and put it beside as I did not have time for trouble-shooting. Now, I try it again. I am not able to run through the calibration process.
Channel 1 is fine and I can go through the whole calibration process without any problems. On channel 2 am not able to calibrate the Q-bias (at step 8, I am not able to reach the 0dB by adjusting the Output. The nedle is around +1dB and I am only able to increase that level, not coming down to 0dB. Also, the Q-bias trimmer can not be set, so that the nedle shows -1dB... It does not react in any way).

What I have checked:
The PSU-Voltages are fine, the device is defenitly in "dual-mono-mode", all relays are switching as they should, all voltages on the board are measured and are fine (the biggest differences are 16,2 V where it should be 18V and 15,8V where it should be 16,7 V, so I think that is ok...), between the XLRs Pins 1 and ground I measured 0,5 Ohm, I got the correct Tantalum Caps (35V), all wirings are checked 10 times and are fine (I also flipped all frontpanel controls from the working channel 1 to channel 2 on the board - still the same, so the fault is defenitly on the main-board, all resistors are measured from hand before soldering, all soldering points are checked and also the passes from one soldering point to the next soldering points, and I also checked 10 times if I changed the polarity of every part on the board.... I could not find any mistakes!

Until now, I did not check the trick with the finger on the BC107 (as I want to use the unit without that trick : ) I need my fingers elsewhere during recording...

My next step is just to order all transistors as they are not expensive and I will get everything here at Reichelt-Elektroniks. And it is also fine to have some spare-parts for the future...

Question to Gustav: For the BC107 you recommend the BC107 B, correct?
What is about the BC560? Also "B", or better "C" ?
I am also going to change the BD140 and the BD139. Are there also different types and which should I choose?

It is just a try, but worth to do it... I will give an update if there is a progress with my unit.

Many thanks to all of you.

 

[Gustav]

Channel 1 is fine and I can go through the whole calibration process without any problems. On channel 2 am not able to calibrate the Q-bias

Question to Gustav: For the BC107 you recommend the BC107 B, correct?
What is about the BC560? Also "B", or better "C" ?
I am also going to change the BD140 and the BD139. Are there also different types and which should I choose?

It is just a try, but worth to do it... I will give an update if there is a progress with my unit.

Many thanks to all of you.

You can go through the path on the main board, and check for differences - check the test-points, for example.

If your voltages are good, I doubt its a bad transistor, but I understand it can give peace of mind to rule it out.

Transistors - just check datasheets, usually, theres a difference in Hfe, but there can also be differences in pinouts on the various types. Sometimes, the choice of one over the other is not important in a specific design, and sometimes it is essential - in some cases, we can forget some small idiosyncrasy causing a specific choice, in some cases, we just settled on the part that did the job, and keep using that, because we know it does

Use BC107B - its a tighter spec'd part than BC107
Use the 560B, if you are ordering in.
I dont have a recommendation for a specific BD140.

Gustav

 

[noisear]

You can go through the path on the main board, and check for differences - check the test-points, for example.

If your voltages are good, I doubt its a bad transistor, but I understand it can give peace of mind to rule it out.

Transistors - just check datasheets, usually, theres a difference in Hfe, but there can also be differences in pinouts on the various types. Sometimes, the choice of one over the other is not important in a specific design, and sometimes it is essential - in some cases, we can forget some small idiosyncrasy causing a specific choice, in some cases, we just settled on the part that did the job, and keep using that, because we know it does

Use BC107B - its a tighter spec'd part than BC107
Use the 560B, if you are ordering in.
I dont have a recommendation for a specific BD140.

Gustav

Hey Gustav,

thanx for your kind support. My MS76 made the next step.

I ordered the transistors (plus some spare ones) and checked them before solder them. That was a good decision, one of the new BC107 was defect straight out of the bag ! Being too lazy to check each of the transistors I already had soldered on the board, I simply exchanged all transistors of channel 2 and it fixed it.

Now, I can go through the whole calibration process on both channels without any problems. But I am not able to exactly say which one of the transistors I changed caused the problem... But I don`t care, it works now and I did not have to do very different settings on the trimmers and the Input and Output. The results of the calibration make sense...

BUT: I found another issue (and I think it will be the last one : )
After finish the calibration with a 1khz tone I just turned the ratio-knob to see what happens (still with the 1khz tone, same levels as during the calibration-process) and I think it does not behave in a correct way. And this happens exactly in the same way on both channels (1 + 2 in Dual Mono)

Comp-Bypass and Ratio 2:1 = 0dB GR, than I switched Com-In
Ratio 2:1 = about 3 dB GR
Ratio 4:1= about 6 dB GR
Ratio 8:1= stays at 6 dB GR
Ratio 12:1= less GR than in 8:1
Ratio 20:1= less GR than in 12:1
All Mode in= less than 3 dB GR
(if I remeber correct, I did that yesterday evening..., maybe not the absolute correct GR-values but that describes the way it reacts...)
Did not change the source level, nor any other setting beside the ratio.

I checked the wiring again from the ratio-board to the main-board, all fine 1=1, 2=2 ...
I checked If I installed the Lorlin in a wrong way but that is not the problem (And I found that it is nearly impossible to do it wrong as long as the center-taps A and C are correct, which they are at my build.

Today I will checkt the resitors on the ratio-board again, but I am very, very sure, they are correct. I did it with great care and measured every resistor before soldering and checked everything a lot of times.

Any other idea what could cause that problem on BOTH channels?

Thanks a lot!

 

[Gustav]

Hey Gustav,

thanx for your kind support. My MS76 made the next step.

I ordered the transistors (plus some spare ones) and checked them before solder them. That was a good decision, one of the new BC107 was defect straight out of the bag ! Being too lazy to check each of the transistors I already had soldered on the board, I simply exchanged all transistors of channel 2 and it fixed it.

Now, I can go through the whole calibration process on both channels without any problems. But I am not able to exactly say which one of the transistors I changed caused the problem... But I don`t care, it works now and I did not have to do very different settings on the trimmers and the Input and Output. The results of the calibration make sense...

BUT: I found another issue (and I think it will be the last one : )
After finish the calibration with a 1khz tone I just turned the ratio-knob to see what happens (still with the 1khz tone, same levels as during the calibration-process) and I think it does not behave in a correct way. And this happens exactly in the same way on both channels (1 + 2 in Dual Mono)

Comp-Bypass and Ratio 2:1 = 0dB GR, than I switched Com-In
Ratio 2:1 = about 3 dB GR
Ratio 4:1= about 6 dB GR
Ratio 8:1= stays at 6 dB GR
Ratio 12:1= less GR than in 8:1
Ratio 20:1= less GR than in 12:1
All Mode in= less than 3 dB GR
(if I remeber correct, I did that yesterday evening..., maybe not the absolute correct GR-values but that describes the way it reacts...)
Did not change the source level, nor any other setting beside the ratio.

I checked the wiring again from the ratio-board to the main-board, all fine 1=1, 2=2 ...
I checked If I installed the Lorlin in a wrong way but that is not the problem (And I found that it is nearly impossible to do it wrong as long as the center-taps A and C are correct, which they are at my build.

Today I will checkt the resitors on the ratio-board again, but I am very, very sure, they are correct. I did it with great care and measured every resistor before soldering and checked everything a lot of times.

Any other idea what could cause that problem on BOTH channels?

Thanks a lot!

There is no way to turn the lorlin the wrong way at all, so thats definitely not it.

Did you recheck voltages around the transistors?

Are your checking the ratio readings with an external meter, or on the internal meter of the unit?

Gustav

 

[c1184701]

Comp-Bypass and Ratio 2:1 = 0dB GR, than I switched Com-In
Ratio 2:1 = about 3 dB GR
Ratio 4:1= about 6 dB GR
Ratio 8:1= stays at 6 dB GR
Ratio 12:1= less GR than in 8:1
Ratio 20:1= less GR than in 12:1
All Mode in= less than 3 dB GR
(if I remeber correct, I did that yesterday evening..., maybe not the absolute correct GR-values but that describes the way it reacts...)
Did not change the source level, nor any other setting beside the ratio.

So for a given source level you are reading more compression at lower ratios? I think this is normal/correct. The 1176 design has a softer knee and lower threshold at lower ratios. Check out this graph of the ratios from the original 1176 manual. You can see how a -25dB input signal would result in compression at 4:1 ratio, but no compression at 20:1.

 

[noisear]

So for a given source level you are reading more compression at lower ratios? I think this is normal/correct. The 1176 design has a softer knee and lower threshold at lower ratios. Check out this graph of the ratios from the original 1176 manual. You can see how a -25dB input signal would result in compression at 4:1 ratio, but no compression at 20:1.

Hey Guys,

thanks a lot for your help and your fast reply!

If you are too deep into trouble-shooting and are still looking for issues although your device is already completly working, it is defenitly time to have a break : )

After having a short look at the diagram (thanks a lot c1184701) I think I am not closed by, I already hit it! I will check that this weekend and hopefully there is another working MS76 born.

Thanks Gustav for creating so many cool stuff and for your support with endless patience! And thanks to all other helpers and creatives in this forum!

I will report...

 

[Gustav]

Hey Guys,

thanks a lot for your help and your fast reply!

If you are too deep into trouble-shooting and are still looking for issues although your device is already completly working, it is defenitly time to have a break : )

After having a short look at the diagram (thanks a lot c1184701) I think I am not closed by, I already hit it! I will check that this weekend and hopefully there is another working MS76 born.

Thanks Gustav for creating so many cool stuff and for your support with endless patience! And thanks to all other helpers and creatives in this forum!

I will report...

Yes, I read your initial chart wrong - the threshold will move with the ratio!

Congrats

Gustav

 

[noisear]

Yeesssss !! Finished, tested and working without any issues!

I tried it on some drum tracks and busses today. Very quiet unit with a fantastic sound. After some minutes I know I will love it.
Next week I will take it to the studio from a friend who owns the Purple Auido. For sure, both units are not really comparable but we simply are interested in an A/B testing.

Than, it will mainly work in my live-setup for the master bus (absolutely looking forward to the day when I will be on tour again...)

Once again: Thanx Gustav for creating this little beauty and to all others here in the forum.

And for sure, here some pics of the unit (poor quality pics, sorry) This time I was too lazy to do a own frontpanel design, but there are still some projects to be done and then again with my own designs : )

 

[jaythebike]

Hey there,

I kept in the background because I am still kind of a noob in DIY electronics and i first wanted check all issues refrenced in this thread. Due to the information in this thread I was able to finish and calibrate my unit this weekend. For me it was also the 16 V Tantalum caps which caused issues and I also got confused by the blendswitch, which wasn't connected correct.

As far as I tested it, the unit sounds amazing. I will continue to experiment the next weeks. I have some small issues with the needle position, but I think i will solve this by recalibrating.

Thank you all for your information. I will try to help if it is in my abilities.

Best wishes

Julian

 

[rtron]

Does anybody know how the 1176 design can have attack times listed in the range of 20 us to 0.8 ms when the RC values look like 470ohm x 220nF = 100 us to 25k (attack pot) x 220nF = 5.5 ms. I am confused about how it can be so fast...?