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

[evilcat]

Hi,

I got some questions about the PCB...

- on the PCB R11=10k but on the BOM R11=9,1k
What is the good one ?

- R43 = 38,3k. i tested all my resistor and the 38,3k from Mouser are 38,8k. Is this bad ? Or that's OK ?

- Do you know where is R77 ?

Thanks

On my old BOM (maybe 1 or 2 years) R11=10k, so on my build too and it works!!
For R43, with 38,8k your still in a 5% range so it's ok.
R77 is only for the none rotary switch version : see the schematic in the Meter Driver section, near the "+8".

Best,

Ben

 

[The Beatsmith]

Hi guys

Have a Rev A kit from mnats/Hairball here, my buddy Sam's building it for me.

When i ordered the kit i opted for the LED meter instead of the standard. However we're struggling to figure out how to power the led meter directly from the pcb?

Does anyone have any tips on the wiring?

Sam thinks that he needs to take a supply from the rectified 30v on the main pcb and drop the voltage with a current limiting resistor. If there's a 6v supply anywhere on the pcb that would be easier! But he cant find one on the schematic

Help would be massively appreciated

Thanks!

Eddie

 

[Ilya]

Wouldn't it be easier to take -10V and drop from that rather then from 30V? Currents are small though, so this may not matter that much.

Oh, and I believe those LEDs are 2V, not 6V. Check the datasheet.

 

[jonathanmorbin]

Hi, Im new to this site but i have just built my first mnats 1176 Rev A with the hairball audio kit. i have a few problems i cant work out and was wandering if anyone here had any thoughts.

THe unit powers fine although i notice that at the moment the -10v Rail seems to take its time to reach -9.56v. I have also noticed that on occasions it seems to fluctuate but only between -9.2v and -9.56v. this also shows on the meter by the needle moving slightly up or down. the 30v is stable at 29.8v and doesn't fluctuate.

The problem i am having is with the compression. I can get an input and an output signal but with the compression on each ratio shows almost the same amount of compression. when feeding a 0.7vpp 1khz signal i seem to need a lot of input before compression takes place. compression still takes place and i can hear this when i using an audio track through the compressor. I have checked AC on Pad 22 and the sine wave is:

4:1  0.3vpp
8:1 0.6vpp
12:1 2vpp
20:1 2vpp
All 0.6vpp

i also checked DC voltage at pad 21

20:1 5.65
12:1 3.05
8:1 2.21
4:1 1.38

This to me suggests that both the ratio and threshold side are functioning correctly but correct me if im wrong.

I did notice on my ratio board that a couple of connections were missing. i have had to connect R78 with R19 and the 20:1 ratio switch as well as connecting R58 to R45.

interestingly when i remove pad 21 the meter shows a drop in compression when i flick from 20:1 down through to 4:1

I have double checked the wiring is correct and carried out the calibration a number of times with full success

Does anyone have any suggestions?

 

[Echo North]

THe unit powers fine although i notice that at the moment the -10v Rail seems to take its time to reach -9.56v. I have also noticed that on occasions it seems to fluctuate but only between -9.2v and -9.56v. this also shows on the meter by the needle moving slightly up or down. the 30v is stable at 29.8v and doesn't fluctuate.

That's an issue.  Did you build and test your power supply section before stuffing the rest of the board?  That would help in knowing if it's an issue with the power supply or something else causing a voltage sag.

The problem i am having is with the compression. I can get an input and an output signal but with the compression on each ratio shows almost the same amount of compression. when feeding a 0.7vpp 1khz signal i seem to need a lot of input before compression takes place. compression still takes place and i can hear this when i using an audio track through the compressor. I have checked AC on Pad 22 and the sine wave is:

4:1  0.3vpp
8:1 0.6vpp
12:1 2vpp
20:1 2vpp
All 0.6vpp

i also checked DC voltage at pad 21

20:1 5.65
12:1 3.05
8:1 2.21
4:1 1.38

This to me suggests that both the ratio and threshold side are functioning correctly but correct me if im wrong.

I assume those pad 21 voltage are actually negative.  If so they seem fine.  Your 20:1 P-P pad 22 voltage should be a little higher than the 12:1.

I did notice on my ratio board that a couple of connections were missing. i have had to connect R78 with R19 and the 20:1 ratio switch as well as connecting R58 to R45.

I'm not sure what you are saying here?

interestingly when i remove pad 21 the meter shows a drop in compression when i flick from 20:1 down through to 4:1

That makes sense.  You've maid the threshold super low.

Remember also that the compression that you see on the meter (-3..-5 or whatever) is not indicative of ratio.  Ratio is the relationship between two different measurements.

 

[jonathanmorbin]

That's an issue.  Did you build and test your power supply section before stuffing the rest of the board?  That would help in knowing if it's an issue with the power supply or something else causing a voltage sag.

I did test this and from what i remember they were reading correct. i didnt notice any sag or odd readings.

I assume those pad 21 voltage are actually negative.  If so they seem fine.  Your 20:1 P-P pad 22 voltage should be a little higher than the 12:1.

Sorry yes these are negative and i made a typo on the P-P 20:1, it was higher as i would expect it to be

I'm not sure what you are saying here?

When i tested for continuity on my ratio board i found that R19 was connected on one side to R20 and the 12:1 switch but the other side was not connected to anything so i made the connection myself to one side of R78 and the 20:1 switch. there is a track between R19 and R78 but it must have got broken.

similarly R58 was not buzzing between R58, R61 or the 4:1 Switch so i made these connections. (i just realised i forgot to re-make the connection between R61 and R58 after doing some testing and now my negative voltage reads stable at -9.6V at the test point. it looks like no more sag. when i turn the unit on it rises up to this voltage over a period of 10 secs whereas the 30v rail is instant. is that normal?)

Remember also that the compression that you see on the meter (-3..-5 or whatever) is not indicative of ratio.  Ratio is the relationship between two different measurements.

Surely though with the same input signal, 1kh, 0.7 p-p, keeping the input controls the same i should see that when i increase the ratio the amount of compression will increases on the meter? (like when i remove the threshold and make it super low)

 

[Echo North]

You shouldn't be removing pad 21.  It's working correctly.  Under normal operation the compression displayed decreases as you move from ratio 4-20.  4 will show the most compression and 20 the least.  This is a one point measurement. 

You 21 and 22 measurement seem reasonable. 

Use the MNATS voltage doc on the rev A mnats site and check all of your DC voltages.

Mike

 

[jonathanmorbin]

Ok I have measured my voltages. they are all pretty close below are the only ones that are a little more off than others. The major difference i can see is that on Q2 i am not getting a negative reading i am getting a posative reading. im not sure why this is?

Q2 6.48 6.73
Q2 4.26 4.51
Q2 1.35 -2.22

Q4 12.27 13.72
Q4 4.38 6.6

Q7 4.5 4.71
Q7 4.6 5.22
Q7 16.8 16.93

Q10 13.9 14.96
Q10 13.7 14.39

 

[jonathanmorbin]

sorry just to confirm the bold numbers are the readings i am getting from my unit.

Jon

 

[mnats]

The major difference i can see is that on Q2 i am not getting a negative reading i am getting a posative reading. im not sure why this is?

It is probably due to one or more of the reasons mentioned on my troubleshooting page.

 

[supiarmando]

Hi there,

I am playing with the Attack Time for my build. JBL schema for Rev a tells R54 should be 12k. Mnats schema tells 1.2k. What do you think is correct?

Has anyone an idea how I could make a long attack time switchable comparable to UA Rev AE? My idea is the bring in an additional resistor. And I have two ways to do it. I make a sketch.

Should I use yellow or brown?

 

[mnats]

JBL schema for Rev a tells R54 should be 12k. Mnats schema tells 1.2k. What do you think is correct?

There is a clean copy of the Rev A schematic on my site. Have a look at that, then tell me if you trust the reproduction in the JBL document.

 

[supiarmando]

Great, and thanks for getting things clear!

Btw: do anyone has a glue how UA does long attack switch in their REV AE?

 

[jonathanmorbin]

Not having much luck at the moment..

looks like my sag is back. When the q-bias resistor is ccw (unbiased) i have a stable -9.62v but as i turn it during the bias adjustment my -9.62v voltage begins to drop and the sag occurs. i continue the calibration and as i get to the end the sag is slightly worse and my voltage has dropped to around -9.5. Also if i remove pad 18 my voltage goes back to steady -9.62v i also find that when im trying to achieve a 10db drop with 20:1 ratio as per the calibration steps i have the input knob turned all the way to 6 to achieve this and output at about 40. This doesnt seem right to me, can anyone confirm this for me.

I also still dont have a negative voltage on my q2, can someone confirm whether this is definetley wrong? Im thinking that it is and this is the cause of all my problems but i dont know what could be causing it.

I have checked all connections in the area of q2 and they are all fine. I checked all the resistors in my board before they went in so i know these are correct. Everything is grounded well and ive tripple checked my wiring and thats all fine. Can anyone suggest what i can try next?

Its frustrating as the compression sounds like its working correctly at the different ratios.

 

[mnats]

I also still dont have a negative voltage on my q2, can someone confirm whether this is definetley wrong? Im thinking that it is and this is the cause of all my problems but i dont know what could be causing it.

There is no way the voltage could be negative at that point - it was a typo. I've corrected and posted an updated version.

 

[Echo North]

One thing that can cause your neg rail to be low would be too much current draw.  You need to look at all the R values and components/traces along that rail.  You can see what it feeds on the schematic.  Check your power supply negative R's again.

 

[jonathanmorbin]

Still struggling with this problem. ive checked my r values in all the parts of the -ve rail and they are all fine. ive checked continuity in all the negative parts of the circuit and that all looks fine. Do you have any suggestions of things i can do to try and narrow down this problem?

I dont know if this is relevant but i noticed during testing continuity (i am using a homemade buzzer with a 9v battery) that i get a very low buzz between my rails and ground. I would have thought that this should be silent, no connection at all. The buzz is extremely quiet but it is there. when i use my DMM between the same points the resistance just keeps rising. Is this normal behaviour?

I beginning to think my next step is going to be ordering a new board, removing the components from the old board and re-testing all the components as i stuff the new board.

 

[germoju]

Hi everybody

I just finish a Rev A and I begin the calibration. My problem is step 3 : I follow the instructions, but when I have to turn R44 (Trimmer 5K) to fix -10dB, nothing happen...
R44 doesn't work....
I check all but I dont see anything.... Step 1 and 2 are good....

Did someone had the same problem ?

EDIT :

I find something... I had a stereo link card on it... And at the step 3, when R44 doesn't work, I push the stereo switch, and now R44 is working BUT I cant see the 10 dB drop anymore, no more compression. To see the 10 dB drop, I have to push stereo switch again, compression is back BUT R44 doesn't work
I check + 10x everything but I can't find !

Here are some picture if you see something wrong, please tell me


_IGP5976 par volcanovap, sur Flickr


_IGP5977 par volcanovap, sur Flickr


_IGP5981 par volcanovap, sur Flickr


_IGP5978 par volcanovap, sur Flickr


_IGP5983 par volcanovap, sur Flickr


_IGP5982 par volcanovap, sur Flickr


EDIT #2

That's it : I disconnect the stereo PCB. I plug the wire from the output pot to Ratio Bord pad 15, and calibration is OK ! R44 works perfecly.
So the problem is from Stereo PCB ? my wiring ? the stereo switch ? ... I dont know !!

Someone canhelp please ?

 

[stitch-o]

Hello,
Finishing up a Rev A and ran into something:
1:20 button works but 1:12-4 buttons do no compression.
Everything else seems to be fine.

Any thoughts anyone?

 

[Echo North]

Hello,
Finishing up a Rev A and ran into something:
1:20 button works but 1:12-4 buttons do no compression.
Everything else seems to be fine.

Any thoughts anyone?

Sounds like something is wrong with your offset switching. Check R63 on the ratio switch. Make sure it's 1.5K.  Check for continuity around it.  With ratio 4 selected, what is your DC at pad 21?