[BUILD] 1176LN Rev D DIY

[Echo North]

where should the input be set to when getting the 0 dBu reference on the input to start the calibration?  should i you see a change in value on the xlr if you change the input?  just double checking it should be at 12 o'clock and that i'm not mis-reading the instructions.

Ya all should start midway.  The input toad is not a perfect load, rotating it will change the input some.

 

[denov]

What happens to the DC at the gate of Q1 when you rotate the bias?

0  and -2.74

 

[Echo North]

What happens to the DC at the gate of Q1 when you rotate the bias?

0  and -2.74

If you set it up to do the qbias, with the input/output midway and GR off, with the 0dB 1K signal what is your output when you rotate the qbias...both extremes.  Don't touch the input/output...live then at 12 0clock.

 

[denov]

What happens to the DC at the gate of Q1 when you rotate the bias?

0  and -2.74

If you set it up to do the qbias, with the input/output midway and GR off, with the 0dB 1K signal what is your output when you rotate the qbias...both extremes.  Don't touch the input/output...live then at 12 0clock.

by GR off i'm assuming that no meter buttons are depressed.  i get no change.    i just realized that i haven't checked the solder joins on the meter board yet. 

 

[denov]

i took the meter board out and fixed a bad joint.  the sound is gone but also most the output.  the qbais changes the output but the output is always less than 1v.

 

[Echo North]

i took the meter board out and fixed a bad joint.  the sound is gone but also most the output.  the qbais changes the output but the output is always less than 1v.

You should have 20:1 selected and GR on the meter board.

Try adjusting your qbias again.

 

[denov]

no sure what happen but i'm back to where i started.  too much output voltage, and i can hear the tone.

i went back and doubled checked my meaurements on all the tranistors.  values for everything look really good but for 11, 12, and 13.  are these values ok?  or is there something wrong?

q11
g  -2.19
s  -2.31 
d  12.99

q12
e  -1.73
b  -2.31
c  13.01

q13
e  -1.58
b  -0.99
c  11.10

 

[Echo North]

no sure what happen but i'm back to where i started.  too much output voltage, and i can hear the tone.

i went back and doubled checked my meaurements on all the tranistors.  values for everything look really good but for 11, 12, and 13.  are these values ok?  or is there something wrong?

q11
g  -2.19
s  -2.31 
d  12.99

q12
e  -1.73
b  -2.31
c  13.01

q13
e  -1.58
b  -0.99
c  11.10

Slow down a bit.

- As I mentioned if you have a ton of output you're going to hear a tone.  That's normal. 
- You meter section isn't calibrated yet so a) voltages are not set right and b) it has not effect on our qbias

Asked earlier:
If you set it up to do the qbias, with the input/output midway and GR off, 20:1, with the 0dB 1K signal what is your output when you rotate the qbias...both extremes.  Don't touch the input/output...live then at 12 0clock.

I'm trying to ascertain if a) your amp sections are working right and b) if your FET is dead.

Mike

 

[Echo North]

If you're still getting around 8 VAC like before and rotating the QBias does nothing, something is wrong with your GR FET section.

Try reflowing joints on Q1 and R10.

If that doesn't work you should probably try a new set of FETs.

Mike

 

[denov]

If you're still getting around 8 VAC like before and rotating the QBias does nothing, something is wrong with your GR FET section.

Try reflowing joints on Q1 and R10.

If that doesn't work you should probably try a new set of FETs.

Mike

oh! i think i may have it.  the qbais is now having an effect on the output.  here's what i'm seeing now.

with everything set to calibrate the qbais.  i see

0.775 VAC - XLR in
8.5 VAC -  XLR out

turn out to 8 o'clock

2.75 VAC - XLR out

adjust qbais (which is very senstive when in within range) to about 10 o'clock to see 2.44 VAC.

but i can still hear the tone at this point with nothing plug into the out. if plug i cable in the noise is barely audible. 

does this sound like things are correct now?  i triple checked the all the solders and found that 1 of the legs of Q1 came out of the socket.  i took the advise the build guide and put Q1 and 11 in sockets.

 

[Echo North]

Sounds good.

Ya you want to load the output (have the out put plugged into your interface) and measure the output at the output + and - pads.

Mike

If you're still getting around 8 VAC like before and rotating the QBias does nothing, something is wrong with your GR FET section.

Try reflowing joints on Q1 and R10.

If that doesn't work you should probably try a new set of FETs.

Mike

oh! i think i may have it.  the qbais is now having an effect on the output.  here's what i'm seeing now.

with everything set to calibrate the qbais.  i see

0.775 VAC - XLR in
8.5 VAC -  XLR out

turn out to 8 o'clock

2.75 VAC - XLR out

adjust qbais (which is very senstive when in within range) to about 10 o'clock to see 2.44 VAC.

but i can still hear the tone at this point with nothing plug into the out. if plug i cable in the noise is barely audible. 

does this sound like things are correct now.  i triple checked the all the solders and found that 1 of the legs of Q1 came out of the socket.  i took the advise the build guide and put Q1 and 11 in sockets.

 

[denov]

i can get calibration steps 1 and 2 done.  i run out of trimmer for step 3.

the sound is coming from board. if i press on the pcb with a screw driver he sound goes away.  what did i mess up?

 

[Echo North]

i can get calibration steps 1 and 2 done.  i run out of trimmer for step 3.

the sound is coming from R44. if i press on it with a screw driver the sound goes away.  what did i mess up?

When doing the R44/zero adjustment you need to go back and forth adjusting a little at a time.  Anticipate how they interact.

 

[denov]

i can get calibration steps 1 and 2 done.  i run out of trimmer for step 3.

the sound is coming from R44. if i press on it with a screw driver the sound goes away.  what did i mess up?

When doing the R44/zero adjustment you need to go back and forth adjusting a little at a time.  Anticipate how they interact.

the closest i can get after a few tries is 0  and -8.5.

and the sound stops if i press anywhere on the pcb with a screw driver. 

 

[Echo North]

You'll have to go through the discrete meter circuit and check the components and joints. 

Always start with R44 and Zero adj centered and make small adjustments.

 

[midwayfair]

if i press on the pcb with a screw driver he sound goes away.

This sounds like you have a solder joint that is making or breaking contact when you press on the PCB, and usually indicates a bad solder joint. I'd highly recommend reflowing your solder joints.

 

[justinheronmusic]

No Gain Reduction at 20:1 Ratio

Stuck on 3rd Calibration step. Tried searching through the forums and I can't seem to find any clear solution to this issue, there are also a lot of dead links and the GroupDiy search isn't working (I think it's a website issue)

With attack fully CW:
I've got GR/Voltage drop at the output XLR with Ratio @ 4:1
As I move up the ladder, I get less and less GR/Voltage Drop.
At 20:1 Ratio I have absolutely no voltage drop/GR at the XLR output

I can do all the other calibration steps, it's just this meter issue revealed that there isn't any GR at 20:1 so I know something is wrong. Where should I be looking? What should I be checking?

 

[Echo North]

No Gain Reduction at 20:1 Ratio

Stuck on 3rd Calibration step. Tried searching through the forums and I can't seem to find any clear solution to this issue, there are also a lot of dead links and the GroupDiy search isn't working (I think it's a website issue)

With attack fully CW:
I've got GR/Voltage drop at the output XLR with Ratio @ 4:1
As I move up the ladder, I get less and less GR/Voltage Drop.
At 20:1 Ratio I have absolutely no voltage drop/GR at the XLR output

I can do all the other calibration steps, it's just this meter issue revealed that there isn't any GR at 20:1 so I know something is wrong. Where should I be looking? What should I be checking?

The threshold decreases as you go from 4 to 20 so your GR will decrease.  Keep in mind ratio is not overall compression.  Can you get compression at 20:1 if you increase the signal and output?

 

[denov]

if i press on the pcb with a screw driver he sound goes away.

This sounds like you have a solder joint that is making or breaking contact when you press on the PCB, and usually indicates a bad solder joint. I'd highly recommend reflowing your solder joints.

reflowed a few things. now pressing on the pcb doesn't do anything.  it sound like the sound if coming from the audio transformer.

with a perfect build should you hear anything at any point?  under normal operations should you every hear anything?

 

[Echo North]

- As I mentioned if you have a ton of output you're going to hear a tone.  That's normal.