[BUILD] 1176 Rev A - Back to the beginning...

[Rob Flinn]

Thanks Rob
I can use it in new Mnats rev F ?
thanks

It would appear so from looking at Makos white market page where it says it is suitable to use with the new B11148 transformer that Ed designed !  What do you reckon ?

 

[muffy1975]

Hi team Rev A,

I've now build two Rev A models and both have the same slight problem.

The negative rail measures -9.8V when disconnected to the attack and release pot.

When I connect them the negative rail measures -9.3V!!!!!!!!!!!!!

This negative rail voltage can measured in the PSU.

I am using the pushbutton wiring diagram. And I have tried re wiring the attack and release pots but with the same problem.

What is going on?????

I notice this does not happen on my REV D.

Thanks in advance.

Michael

ps has anyone else checked for this or is this just me

 

[ilfungo]

Ciao
I had the same problem with one REV A and 2  REV B (not in the second rev A)
to me the negative voltage down to -8.6 when connected ratio  and meter board ...
I do not know if I did well but changing R 81 (1K) with 470R tension is ok now

 

[muffy1975]

Hey there,

thanks so much for getting back.I'm glad I'm not the only one.

Would this appear to be some kinda inherent design flaw?

So R1 needs to be changed? Has Mako said anything about this.

My -9.3V does not seem to be effecting the units but all the same I would like it up nearer -9.8 or -10v!!

Warmness and gratitude

Michael ( a Rev A lover )

 

[ilfungo]

Hello Michael
I just wanted to say that I changed R81
I do not know if it's the right thing and if it can create problems
but on my 1176 it worked
hello and see you soon

 

[Stagefright13]

I doubt there is an inherit design flaw! The schematic is as old as I am. Why are you measuring voltages anyway? You don't have a working unit yet? Does it sound good?

Mine is the original Mnats board with no mods and sounds great. But just recently removed it from the rack for some cable ties on the wiring. And for a reference on another build.

John

 

[stereokillah]

hello
i'm finishing the my second rev A, and when i started to calubrate it i found a problem:

when i put a sine signal 0.775 vac in input i need to put input and output full to have a smal signal in output xlr, and don't have compression .

i've tried to put the main board in my first unit who work great and it's same problem, so the problem is from this board and wiring and transformer.

if someone had the same problem and can help me !!!

thanks

 

[Biasrocks]

hello
i'm finishing the my second rev A, and when i started to calubrate it i found a problem:

when i put a sine signal 0.775 vac in input i need to put input and output full to have a smal signal in output xlr, and don't have compression .

Here's how I did it.

Do the QBias calibration procedure, dropping 1db first. That gets the FET conducting,

Next, taking the tracking adjustment out of circuit with the jumper. Test your null points at TP10,TP11
and adjust the Null control as needed.

Then try the calibration procedure with 1.22 volts (0dBVU), it worked a lot better than .775v for me.

Mark

 

[ChrioN]

I've now read through most of this thread, as I'm waiting for the PCBs.
Some diyers seems to have problems building this unit.
Whats the most common pitfalls? Any mods or changes that one should be aware of? I'll be doing the pushbutton version...

 

[stereokillah]

hi Biasrocks , thank you i'll try it

hi ChrioN , there less problem than the gssl i think, there is some resistors changement , the link is in this thread, if i find it i'l post it.

 

[ChrioN]

stereokillah: thanks, that would be very kind of you!

 

[Biasrocks]

hi Biasrocks , thank you i'll try it

hi ChrioN , there less problem than the gssl i think, there is some resistors changement , the link is in this thread, if i find it i'l post it.

To add a little more from memory.

After adjusting QBias, I set up the limiter as specified in the instructions.

20:1, Attack & Release full CW, Input & Output around midway point.

When I was aligning the meter for 10db of reduction, I used a -10dBu tone in my DAW and brought that up to around read 0dBVU (1.22vac) on the limiter. I went into GR metering and played with the input level until I was just bumping into the start of gain reduction, where the meter just started to show GR and then backed it off slightly to show no GR. That way when I increased the tone in my DAW by 10db I was guaranteed to be getting 10db of GR through the limiter. Then it was a matter of bouncing between the ON/OFF Attack position and adjusting the tracking to get it to read 10db of GR on the meter.

Regarding mods.

I mapped out all of the differences between MNats REV A version and three versions of the Urei schematic (REV A, AB, B). I setup the GC Amplifier and QBias control to be exactly like the "REV B" version of the schematic, which I verified against the real version of the limiter. It came down to 3 resistor value changes and one additional resistor; plus two more changes if you REALLY want to be picky and be true to the original version.

I like the sound a lot and I'm not having any issues with All Buttons In mode, aside from it sounding pinched if you hit it too hard and don't have your ATT/REL settings in an appropriate spot.

I will say, that it seemed to be a bit more challenging setting up the REV A metering when compared to the REV J I completed a while back. But the resulting sound was well worth the trouble.

Mark

 

[ChrioN]

Thanks for the info Biasrocks! Is there a "plosive mod" for the rev A too?

 

[mnats]

there is some resistors changement , the link is in this thread, if i find it i'l post it.

Rob Flinn and others did the work on this and their efforts are reflected in the BOM linked from the first post. Look for the optional resistor values. One change has been incorporated into the BOM as there was a mistake on the earlier versions of the BOM and screen layer of the board.

 

[Rob Flinn]

Biasrocks

Could you detail exactly what changes you made?  I'm just interested because I am unable to compare my clones to an original.

 

[stereokillah]

hello Biasrocks ,
it was what you said ,just the tracking adjustment was full instead of OFF now it is finish just need to be calibrated when i 'll have time.

 

[gary o]

hi folks is there any further news on the this Rev A wired as a 1108 mic pre.....thanks

 

[mnats]

hi folks is there any further news on the this Rev A wired as a 1108 mic pre.....thanks

All the info is out there and it is still possible to modify the current Rev A 1176 boards to become an 1108 but I suspect what you are asking is if a stand-alone 1108 board has been created. I have started one but got stuck trying to work out the attenuation scheme at the front end. Currently I don't have a lot of time on my hands and I don't see that changing soon. It might be nice to see a breakaway thread and more people experimenting with this circuit. Maybe one way for that to happen is for me to clean up the existing files and post some self-etch PDFs of the main circuit and let people try it out for themselves?

 

[gary o]

Thanks Im planning to add transformer switches and mic socket to my rev just wondered if any extra info out there Im sure it will work 

 

[gary o]

had quick try connected a mic transformer to across the pot works nicely gonna add a mic pre compressor switch & extra socket

thanks