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

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I am SO in love with my Hairball Rev A old version. It's just plain incredible and does something awesome to any vocals I run thru it.

So here's my question : if I want a pair of them, are there any circuit changes between the old and new kits ?
 
hi.
cannot wrap my head around Igor's F76 LL1524 schematic and Rev.A output feedback. Maybe this traffo can't be used with Mnats 1.25 boards?
As i have a LL1524 pair, i might as well use them. They are so good.
As per Igors, primary + 12/7 and - 11/8; output +6/3 and 4/1 shunt. But then i have 5/2 not connected but i tested these are outs too.

any help is welcomed
 
I am SO in love with my Hairball Rev A old version. It's just plain incredible and does something awesome to any vocals I run thru it.

So here's my question : if I want a pair of them, are there any circuit changes between the old and new kits ?
I've built the old ones and the new ones. The only difference I know of is the board layout, which makes it much easier to assemble and has an integrated option to add an active stereo linking option.

Thanks!

Paul
 
Hi everyone.
I just finished my 1176 rev D,
But the sound is completely distorted.
And the unit, more precisely, the transformer make a strange noise like whistling like a radio…
If someone can help me…
 
Hi. This is Rev A thread, not Rev D.
As for your issue, this sounds like an oscillation in high frequencies. Check for proper wiring.
 
Hi, ve built a pair of Mnats 1176 A's and I measured wrong DC Voltages on the two JFets J309. Also my Output Level feeding with an 1kHz Sine is very low.
So I ve measured the 309J's and have recognised that they are BJTs and not JFETs!!! Original Aliex Fairchild Quality....😫.... Hell.... Five meteres before finishing the units...... I also made the expierence with BF245A's... Especially always with Fairchild brands... Cheap BJTs reprinted in China... I am such an Idiox....👿.... Sorry for my words....
 

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Hi everyone, I hope you're having a good day!
I just finished building a Rev A kit (V1.25 05/12/10) but I've encountered some problems during the calibration procedure.
There's clearly something wrong with it.

I started by trying to set the Q Bias with the procedure on the hairball website:
------------------------------------------------------------------------------------------
Input = "24" mid-rotation, Output = "24" mid-rotation
Attack = full CCW (switched to off position)
Release = full CW
Compression ratio = 20:1
Meter mode = "GR"
Q-bias adjustment = full CCW
Shorting pin in "normal position" connecting the two pins closest to Q13

Apply a 1 KHz O dBu signal to the input and confirm with your DMM between pin 2 and 3 of the input XLR. Now move your DMM to the output XLR and measure AC between pin 2 and 3. Adjust the output control to read +11dBu (2.75 VAC) on your DMM at the output. Slowly turn the Q-bias adjust (R59) CW until a drop of 1 dB occurs, and your DMM reads +10 dBu (2.44 VAC). This places your gain reduction FET Q1 slightly into conduction.
------------------------------------------------------------------------------------------

I'm not able to have enough gain to reach 2.75 VAC on the output and proceed with the calibration, I barely reach 1.4v (all of this with the Q Bias pot fully CCW, If I start to rotate clockwise I can reach a much higher output level).


I tried to examine the Bias voltage on pin 18 and I noted an excursion from 0 to -2.8V which doesn't coincide with the values on the troubleshooting guide for Rev A (https://help.hairballaudio.com/hc/en-us/articles/360045942974)
I strangely have the same values present on Rev D......

I checked all the voltages, Power supply, and all the other voltages indicated on the schematic (Revision A DC Voltage Chart). They all are in the +-10% range, mostly spot on.

I checked the ac voltages and there's clearly a problem
Test PointRevision A (ideal)My Rev A
TP10.100 VAC0.100 VAC
Q2 Gate0.084 VAC0.003 VAC
Q3 Base0.051 VAC0.001 VAC
TP153.60 VAC0.040 VAC

I already tried to change Q1,Q2 and Q3 with no success.

I believe the problem is related to the Bias voltage or something related to it. When following the procedure to set the Q Bias I noticed that the output level increases with turning the trimmer clockwise, the bias voltage will go more negative as well reaching -2.8 at the end of the pot.
I attached a video of the failed calibration procedure.

Thanks to everyone that will find some time to help me!!!
Michele
 

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I'm not able to have enough gain to reach 2.75 VAC on the output and proceed with the calibration, I barely reach 1.4v (all of this with the Q Bias pot fully CCW, If I start to rotate clockwise I can reach a much higher output level).
you're looking for 0dBu or .775v AC signal on the input. Also, your q bias adjust should be in the position where you get most gain, then set output to +1dB on the meter. Then turn the trimmer so you get the meter showing 0dB. My experience if that the specific amount of signal you're putting in isn't important, just that your adjust is set to reduce the meter level by 1dB
 
Hi everyone, I hope you're having a good day!
I just finished building a Rev A kit (V1.25 05/12/10) but I've encountered some problems during the calibration procedure.
There's clearly something wrong with it.

I started by trying to set the Q Bias with the procedure on the hairball website:
------------------------------------------------------------------------------------------
Input = "24" mid-rotation, Output = "24" mid-rotation
Attack = full CCW (switched to off position)
Release = full CW
Compression ratio = 20:1
Meter mode = "GR"
Q-bias adjustment = full CCW
Shorting pin in "normal position" connecting the two pins closest to Q13

Apply a 1 KHz O dBu signal to the input and confirm with your DMM between pin 2 and 3 of the input XLR. Now move your DMM to the output XLR and measure AC between pin 2 and 3. Adjust the output control to read +11dBu (2.75 VAC) on your DMM at the output. Slowly turn the Q-bias adjust (R59) CW until a drop of 1 dB occurs, and your DMM reads +10 dBu (2.44 VAC). This places your gain reduction FET Q1 slightly into conduction.
------------------------------------------------------------------------------------------

I'm not able to have enough gain to reach 2.75 VAC on the output and proceed with the calibration, I barely reach 1.4v (all of this with the Q Bias pot fully CCW, If I start to rotate clockwise I can reach a much higher output level).


I tried to examine the Bias voltage on pin 18 and I noted an excursion from 0 to -2.8V which doesn't coincide with the values on the troubleshooting guide for Rev A (https://help.hairballaudio.com/hc/en-us/articles/360045942974)
I strangely have the same values present on Rev D......

I checked all the voltages, Power supply, and all the other voltages indicated on the schematic (Revision A DC Voltage Chart). They all are in the +-10% range, mostly spot on.

I checked the ac voltages and there's clearly a problem
Test PointRevision A (ideal)My Rev A
TP10.100 VAC0.100 VAC
Q2 Gate0.084 VAC0.003 VAC
Q3 Base0.051 VAC0.001 VAC
TP153.60 VAC0.040 VAC

I already tried to change Q1,Q2 and Q3 with no success.

I believe the problem is related to the Bias voltage or something related to it. When following the procedure to set the Q Bias I noticed that the output level increases with turning the trimmer clockwise, the bias voltage will go more negative as well reaching -2.8 at the end of the pot.
I attached a video of the failed calibration procedure.

Thanks to everyone that will find some time to help me!!!
Michele
Ha i have precise same issue as you with build A. My cue bias voltage is same as in build D (0v til -2,9
v in place A revision at TP18. I can set cue bias calibration but second step for metering is no go....
 

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