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

[blackartmixing]

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

thanks for your help.  i just tried for the first time with some audio.  it appears to be clean.  the input is working and attack is working as expected but then release and output done really seem to do much.  i'll check the wiring again

 

[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

thanks for your help.  i just tried for the first time with some audio.  it appears to be clean.  the input is working and attack is working as expected but then release and output done really seem to do much.  i'll check the wiring again

Make sure your release and output pots are not swapped.  Release is the 5M and output is the 250K.

Mike

 

[blackartmixing]

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

thanks for your help.  i just tried for the first time with some audio.  it appears to be clean.  the input is working and attack is working as expected but then release and output done really seem to do much.  i'll check the wiring again

Make sure your release and output pots are not swapped.  Release is the 5M and output is the 250K.

Mike

i checked that at the start.  the output pot has  A250K on it so i assume that one is correct

 

[tata]

this is an "angry monster" in a good way, imo:

http://beatbybit.com/gears/1176_revA_Myon_A-R_test_r001.swf

my rev.A build in action, 4:1. playing with release/attack and input

Meter is not calibrated yet (to be honest i couldnt care less about that..), and im gonna add some extras to it till its gonna be finished - but i must say Thank You for Hairball / mnats for this nice project. it was a fairly easy build - except my issues w/these FETs (not Hairball's fault).
the FET issue (and Mike) taught me new stuff - and thats the way i prefer learning.

Mike : this may be a stupid question, but would you consider selling separate LED metering for the FET/racks (and other products)? or.. hm.. how about an OLED display that shows the GR as i measured on my scope? 2-3 seconds of GR display..
one can dream, right? 

(something like this, but better resolution and DC mode, etc: https://www.youtube.com/watch?v=7-g2FvAQofk)

(Arduino gurus, could you help?..)

 

[Spencerleehorton]

Could anyone help me with correct information about the output transformer on the Rev A circuit.
I am winding my own transformer.
Im having to adjust R32 quite a bit so it sits around 200ohms which would imply that the feedback winding doesnt have enough resistance. Im wondering what ratio of winds the feedback winds are in relation to the 600ohm other Pri.
Or is it indeed a 600ohm winding as well?
I have been using 0.315mm but have other sizes which i could try, what inductance would get me in the ball park?

regards

Spence.

 

[blackartmixing]

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

thanks for your help.  i just tried for the first time with some audio.  it appears to be clean.  the input is working and attack is working as expected but then release and output done really seem to do much.  i'll check the wiring again

Make sure your release and output pots are not swapped.  Release is the 5M and output is the 250K.

Mike

i checked that at the start.  the output pot has  A250K on it so i assume that one is correct

Anyone got any idea what i might of done wrong here?  i've checked the wiring many times and it all looks correct.  i guess i must be missing something.  is there measurements i can take somewhere that can help me troubleshoot where the issue might be?  thanks

 

[Echo North]

If the output isn't working, that's really weird.  Keep the unit in GR OFF for now. Check your output wiring and signal line amp section. Compare to schematic w/ DC voltages:
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

With a 1 kHz, 0dBu signal on the input, GR OFF, and input/output at 12 o'clock....what is your VAC at 15 on the main board and your VAC at XLR out pin 2?

Mike

 

[blackartmixing]

If the output isn't working, that's really weird.  Keep the unit in GR OFF for now. Check your output wiring and signal line amp section. Compare to schematic w/ DC voltages:
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

With a 1 kHz, 0dBu signal on the input, GR OFF, and input/output at 12 o'clock....what is your VAC at 15 on the main board and your VAC at XLR out pin 2?

Mike

the output pin 2 read 1.53 VAC.  can you tell me how i can read point 15 on the main pcb please?  sorry i don't have too much knowledge of how to troubleshoot.  thanks again

 

[Echo North]

If the output isn't working, that's really weird.  Keep the unit in GR OFF for now. Check your output wiring and signal line amp section. Compare to schematic w/ DC voltages:
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

With a 1 kHz, 0dBu signal on the input, GR OFF, and input/output at 12 o'clock....what is your VAC at 15 on the main board and your VAC at XLR out pin 2?

Mike

the output pin 2 read 1.53 VAC.  can you tell me how i can read point 15 on the main pcb please?  sorry i don't have too much knowledge of how to troubleshoot.  thanks again

Set your DMM to read VAC and pop the black wire in a common point like the chassis ground lug or the 0V pad on the power supply, then put your red lead on pad 15.  It's on the back of the PCB, just touch the probe to the screw holding the wire.

If the numbers of covered you can reference the overlay on the MNATS.NET site.

Mike

 

[blackartmixing]

If the output isn't working, that's really weird.  Keep the unit in GR OFF for now. Check your output wiring and signal line amp section. Compare to schematic w/ DC voltages:
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

With a 1 kHz, 0dBu signal on the input, GR OFF, and input/output at 12 o'clock....what is your VAC at 15 on the main board and your VAC at XLR out pin 2?

Mike

the output pin 2 read 1.53 VAC.  can you tell me how i can read point 15 on the main pcb please?  sorry i don't have too much knowledge of how to troubleshoot.  thanks again

Set your DMM to read VAC and pop the black wire in a common point like the chassis ground lug or the 0V pad on the power supply, then put your red lead on pad 15.  It's on the back of the PCB, just touch the probe to the screw holding the wire.

If the numbers of covered you can reference the overlay on the MNATS.NET site.

Mike

ok got it   ok i read 0.775 on input, 1.75 on point 15 and 2.22 on output

 

[Echo North]

GR OFF.  Input/output mid way?

 

[blackartmixing]

yes! attack all the way clicked to off and input and output at 12 o'clock.  meter set to +4, release 7 and ration 20:1

 

[Echo North]

yes! attack all the way clicked to off and input and output at 12 o'clock.  meter set to +4, release 7 and ration 20:1

if you turn the output up and down to you see the VAC at pin 2 of the output fluctuate?

Mike

 

[blackartmixing]

yes but not by much.  full CCW is 2.06 middle is 2.22 and full CW is 2.98

 

[Echo North]

yes but not by much.  full CCW is 2.06 middle is 2.22 and full CW is 2.98

Your output is either wired wrong or your output amp has an error. You need to go through the output amp, check voltage vs the schematic.

Mike

 

[blackartmixing]

could you give me a quick explanation of how to check the voltages please?  where should i connect the red and black leads from my DWW??  and what should i expect to see?  thanks

 

[Echo North]

could you give me a quick explanation of how to check the voltages please?  where should i connect the red and black leads from my DWW??  and what should i expect to see?  thanks

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Put your black on common again, test for DC, google/datasheets will help you identify leads.

 

[tata]

Mike,

ive put in the pair of 2N5457s  i got from you - and Q Bias calibration went smoothly (same w/ the BF245A, so i guess i have a bunch of 'different' 2N5457s..)

now im at the meter calibration step, and i just cant get 0 on R74. its static 0.462VDC no matter how i turn the trimmers.
this is a V1.2.5 05.12.10 board with TP 10/11, so i thought i should put the meter there to see/set the 0.
the DC value changes there as i turn the trimmers, but cant get lower than 0.35-ish VDC. what am i doing wrong, please?

i use 2N5088s in places of 3707s. Q12/13 are hFE matched as close as possible.

do i need to change a trimmer to a higher value?

thanks

 

[Echo North]

Mike,

ive put in the pair of 2N5457s  i got from you - and Q Bias calibration went smoothly (same w/ the BF245A, so i guess i have a bunch of 'different' 2N5457s..)

now im at the meter calibration step, and i just cant get 0 on R74. its static 0.462VDC no matter how i turn the trimmers.
this is a V1.2.5 05.12.10 board with TP 10/11, so i thought i should put the meter there to see/set the 0.
the DC value changes there as i turn the trimmers, but cant get lower than 0.35-ish VDC. what am i doing wrong, please?

i use 2N5088s in places of 3707s

do i need to change a trimmer to a higher value?

thanks

You want to use TP10/11 for the A.  Did you match the HFE of those transistors.  You ant them within 10%.  If they are socketed you could try a different set, or HFE test them with a meter, or try increasing the trimmer.  Better to match however.

 

[tata]

i modified my previous post a bit too late - your answer was faster.

so yes, ive matched Q12/13 as close as possible. (better than 10%)