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

[Echo North]

here is a video of what i have on Pad 7 :

https://youtu.be/AcZ3eas_C8U

You should have a negative DC voltage at the gate of Q1 ranging from 0 to -3VDC(ish) with qbias rotation.  Looking at the schematic:
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

It's fed via the qbias pot from the R80/60 voltage divider up through the attack/release and over to pad 7.  See if you can trace that voltage.

Mike

 

[tata]

Q1 Gate : DC voltage varies between 0 and -29mV when i turn the Q Bias trimmer.  (attack / release : fast)
thats no good, i guess..

DMM shows -9.65V on the neg. rail, and it shows -2.73V on the R60/R80 junction.
-2.39V on Pad  7 at fast attack/ratio, and around 0.87 at slow attack/ratio

 

[Echo North]

Q1 Gate : DC voltage varies between 0 and -29mV when i turn the Q Bias trimmer.  (attack / release : fast)
thats no good, i guess..

DMM shows -9.65V on the neg. rail, and it shows -2.73V on the R60/R80 junction.
-2.39V on Pad  7 at fast attack/ratio, and around 0.87 at slow attack/ratio

It's positive 0.87?

You need to look closely at that wiring.

 

[tata]

sorry, not positive. its -0.87V

 

[Echo North]

sorry, not positive. its -0.87V

Pad 7 is negative bit the Q1 gate isn't.  Look at the stuff on the schematic between those two points.  Only a few things/values.

 

[tata]

Q1 gate isnt? im confused a bit (and still measuring -29mV max. there)

You should have a negative DC voltage at the gate of Q1 ranging from 0 to -3VDC(ish) with qbias rotation.

 

[tata]

it works with BF245A (flipped compared to 2N5457).
i didnt change anything, but the FETs.

im 51% happy - but 49%  would love to know why the 2N5457s dont work.

 

[Echo North]

it works with BF245A (flipped compared to 2N5457).
i didnt change anything, but the FETs.

im 51% happy - but 49%  would love to know why the 2N5457s dont work.

damaged maybe? Are they our 5457's?  They are super sensitive to static electricity and solder heat.

Mike

 

[blackartmixing]

I'm onto the calibration steps but i'm having some problems with the third step (Reduction Meter Tracking Adjustment).  so far everything else has gone ok.  I setup  input to the compressor at roughly 0.775 VAC and then adjusted the input to 2.44 VAC with the attack ON as stated.  so step 5

Turn the attack control ON (Fully CW) and readjust the output level control for "0dBu" if necessary.

so i have the attack on and i try to adjust the output to 0.755 VAC but even the lowest setting on the output is only reading 1.25 VAC roughly so i cannot even get -10DBu.  i've chceked and i'm using the correct pots.  the output is the A250K pot and all the wiring looks to be correct.

any ideas?

 

[Echo North]

I'm onto the calibration steps but i'm having some problems with the third step (Reduction Meter Tracking Adjustment).  so far everything else has gone ok.  I setup  input to the compressor at roughly 0.775 VAC and then adjusted the input to 2.44 VAC with the attack ON as stated.  so step 5

You want to start with the ATTACK ON and adjust the output to 0.775VAC I believe.

Mike

 

[blackartmixing]

I'm onto the calibration steps but i'm having some problems with the third step (Reduction Meter Tracking Adjustment).  so far everything else has gone ok.  I setup  input to the compressor at roughly 0.775 VAC and then adjusted the input to 2.44 VAC with the attack ON as stated.  so step 5

You want to start with the ATTACK ON and adjust the output to 0.775VAC I believe.

Mike

step 4 is Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

also at the moment a full rotation of the output only changes the VU metre by 3 db (-3 to 0 for example). 

 

[Echo North]

I'm onto the calibration steps but i'm having some problems with the third step (Reduction Meter Tracking Adjustment).  so far everything else has gone ok.  I setup  input to the compressor at roughly 0.775 VAC and then adjusted the input to 2.44 VAC with the attack ON as stated.  so step 5

You want to start with the ATTACK ON and adjust the output to 0.775VAC I believe.

Mike

step 4 is Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

also at the moment a full rotation of the output only changes the VU metre by 3 db (-3 to 0 for example).

Should be measuring the output at the XLR. Ignore the meter for now, it's not calibrated.  Try try these videos:

https://www.youtube.com/watch?v=pgSWfsEzU40

He has videos for all the steps.

Mike

 

[blackartmixing]

I'm onto the calibration steps but i'm having some problems with the third step (Reduction Meter Tracking Adjustment).  so far everything else has gone ok.  I setup  input to the compressor at roughly 0.775 VAC and then adjusted the input to 2.44 VAC with the attack ON as stated.  so step 5

You want to start with the ATTACK ON and adjust the output to 0.775VAC I believe.

Mike

step 4 is Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

also at the moment a full rotation of the output only changes the VU metre by 3 db (-3 to 0 for example).

Should be measuring the output at the XLR. Ignore the meter for now, it's not calibrated.  Try try these videos:

https://www.youtube.com/watch?v=pgSWfsEzU40

He has videos for all the steps.

Mike

yes i have seen these videos already.  what seems to be strange with mine is that when he supplied the 0 dbu 1khz tone and turns up the input nothing happens on the meters until he turns up the output.  for me its totally red-lined before i even get to 12 o clock, with only the input turned up and the output turned down completely,  so its impossible for me to get the gain reduction down to -10. does that make sense? 

 

[Echo North]

I'm onto the calibration steps but i'm having some problems with the third step (Reduction Meter Tracking Adjustment).  so far everything else has gone ok.  I setup  input to the compressor at roughly 0.775 VAC and then adjusted the input to 2.44 VAC with the attack ON as stated.  so step 5

You want to start with the ATTACK ON and adjust the output to 0.775VAC I believe.

Mike

step 4 is Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

also at the moment a full rotation of the output only changes the VU metre by 3 db (-3 to 0 for example).

Should be measuring the output at the XLR. Ignore the meter for now, it's not calibrated.  Try try these videos:

https://www.youtube.com/watch?v=pgSWfsEzU40

He has videos for all the steps.

Mike

yes i have seen these videos already.  what seems to be strange with mine is that when he supplied the 0 dbu 1khz tone and turns up the input nothing happens on the meters until he turns up the output.  for me its totally red-lined before i even get to 12 o clock, with only the input turned up and the output turned down completely,  so its impossible for me to get the gain reduction down to -10. does that make sense?

Let's take a step back. So you're able to get a 10dB drop at the output XLR right? Just not calibrate the meter to show that drop?

Mike

 

[blackartmixing]

I'm onto the calibration steps but i'm having some problems with the third step (Reduction Meter Tracking Adjustment).  so far everything else has gone ok.  I setup  input to the compressor at roughly 0.775 VAC and then adjusted the input to 2.44 VAC with the attack ON as stated.  so step 5

You want to start with the ATTACK ON and adjust the output to 0.775VAC I believe.

Mike

step 4 is Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

also at the moment a full rotation of the output only changes the VU metre by 3 db (-3 to 0 for example).

Should be measuring the output at the XLR. Ignore the meter for now, it's not calibrated.  Try try these videos:

https://www.youtube.com/watch?v=pgSWfsEzU40

He has videos for all the steps.

Mike

yes i have seen these videos already.  what seems to be strange with mine is that when he supplied the 0 dbu 1khz tone and turns up the input nothing happens on the meters until he turns up the output.  for me its totally red-lined before i even get to 12 o clock, with only the input turned up and the output turned down completely,  so its impossible for me to get the gain reduction down to -10. does that make sense?

Let's take a step back. So you're able to get a 10dB drop at the output XLR right? Just not calibrate the meter to show that drop?

Mike

No I can't even get that. When I turn down the output it doesn't drop far enough as I mentioned above. From 2.44 vac to only around 1.24 vac and not 0.775 vac

 

[Echo North]

I'm onto the calibration steps but i'm having some problems with the third step (Reduction Meter Tracking Adjustment).  so far everything else has gone ok.  I setup  input to the compressor at roughly 0.775 VAC and then adjusted the input to 2.44 VAC with the attack ON as stated.  so step 5

You want to start with the ATTACK ON and adjust the output to 0.775VAC I believe.

Mike

step 4 is Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

also at the moment a full rotation of the output only changes the VU metre by 3 db (-3 to 0 for example).

Should be measuring the output at the XLR. Ignore the meter for now, it's not calibrated.  Try try these videos:

https://www.youtube.com/watch?v=pgSWfsEzU40

He has videos for all the steps.

Mike

yes i have seen these videos already.  what seems to be strange with mine is that when he supplied the 0 dbu 1khz tone and turns up the input nothing happens on the meters until he turns up the output.  for me its totally red-lined before i even get to 12 o clock, with only the input turned up and the output turned down completely,  so its impossible for me to get the gain reduction down to -10. does that make sense?

Let's take a step back. So you're able to get a 10dB drop at the output XLR right? Just not calibrate the meter to show that drop?

Mike

No I can't even get that. When I turn down the output it doesn't drop far enough as I mentioned above. From 2.44 vac to only around 1.24 vac and not 0.775 vac

Are you starting with both at 12 o'clock, and with GR ON setting the output knob to 0.775VAC first?  I think it's important to start with setting the output knob, then set the input knob.

Mike

 

[tata]

damaged maybe? Are they our 5457's?  They are super sensitive to static electricity and solder heat.

no Mike, these particular FETs arent from you.
solder heat shouldnt be an issue here - i used precision sockets for all transistors.

 

[Echo North]

damaged maybe? Are they our 5457's?  They are super sensitive to static electricity and solder heat.

no Mike, these particular FETs arent from you.
solder heat shouldnt be an issue here - i used precision sockets for all transistors.

Could be a different pin out then.

 

[blackartmixing]

I'm onto the calibration steps but i'm having some problems with the third step (Reduction Meter Tracking Adjustment).  so far everything else has gone ok.  I setup  input to the compressor at roughly 0.775 VAC and then adjusted the input to 2.44 VAC with the attack ON as stated.  so step 5

You want to start with the ATTACK ON and adjust the output to 0.775VAC I believe.

Mike

step 4 is Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

also at the moment a full rotation of the output only changes the VU metre by 3 db (-3 to 0 for example).

Should be measuring the output at the XLR. Ignore the meter for now, it's not calibrated.  Try try these videos:

https://www.youtube.com/watch?v=pgSWfsEzU40

He has videos for all the steps.

Mike

yes i have seen these videos already.  what seems to be strange with mine is that when he supplied the 0 dbu 1khz tone and turns up the input nothing happens on the meters until he turns up the output.  for me its totally red-lined before i even get to 12 o clock, with only the input turned up and the output turned down completely,  so its impossible for me to get the gain reduction down to -10. does that make sense?

Let's take a step back. So you're able to get a 10dB drop at the output XLR right? Just not calibrate the meter to show that drop?

Mike

No I can't even get that. When I turn down the output it doesn't drop far enough as I mentioned above. From 2.44 vac to only around 1.24 vac and not 0.775 vac

Are you starting with both at 12 o'clock, and with GR ON setting the output knob to 0.775VAC first?  I think it's important to start with setting the output knob, then set the input knob.

Mike

i have both at 12 o'clock with GR on and i can only get 1.24 (lowest output) or 1.85 (highest output) on the output XLR so it seems like the signal after the input XLR somehow gets boosted somewhere ?

 

[Echo North]

The compressor has 50dB of total gain. Lots of amplification in it. 

I'll have some stuff for you to check in a bit.  Check your wiring carefully. Does it pass clean signal or is it noisy/oscillating?

Mike