The best noise gate?

[Spencerleehorton]

ok, great stuff, i'll check the 6.8k and 1.5k resistors and also check all transistors, i have a few other FET's which i could change, also i could tweak the 50k trim before the 2M2 release pot see if that has any influence?

 

[Spencerleehorton]

ok, for some reason there was a 56k in where there should have been that 6.8k before Q6!!
Ive changed to 6.8k now, getting Q6 Drain/Source = 0.075v AC and if i turn the attenuation i can get 0.136v AC
so this works now i think?

still very low output and i've checked Q7,Q8 and Q9 transistors and i have 0.6v difference between Emitter and base, so these look good.

any other ideas?

 

[abbey road d enfer]

ok, for some reason there was a 56k in where there should have been that 6.8k before Q6!!
Ive changed to 6.8k now, getting Q6 Drain/Source = 0.075v AC and if i turn the attenuation i can get 0.136v AC
so this works now i think?

Yes, this part works. Now what is the AC voltage at the base of Q7?

 

[Spencerleehorton]

Sorry had to go to work, will try and get more voltages when I finish at 7pm

 

[Spencerleehorton]

AC voltage at base of Q7 = 0.003v

Are we sure that 8.2k/82k resistor is correct? I’ve got 82k in there at the moment.

Dc voltages

Q7
E - 8.74v
B - 8.06v
C - 6.27v

Q8
E - 5.63v
B - 6.27v
C - 23.93v

Q9
E - 5.00v
B - 5.63v
C - 15.22v

 

[abbey road d enfer]

AC voltage at base of Q7 = 0.003v

AC voltage at base of Q7 should be identical to that at source of Q6. Huge discrepancy here.
There is something wrong with the 4.7uF cap.
DC voltages seem correct.

 

[Spencerleehorton]

I didn’t have the ATN pot fully off!, so I am getting the 0.075v at Q7 base!
I’ve traced the signal and I’m getting good waveform until Q8 emitter, so something’s happening after that.
Will look tonight after work, hopefully got a few more days off to finish these.

 

[abbey road d enfer]

I’ve traced the signal and I’m getting good waveform until Q8 emitter, so something’s happening after that.

That is weird; you should have a quite small signal there. Maybe you mean it is clean bu what is the level?

 

[Spencerleehorton]

Pretty sure it was about the same as input 0.608v I think will check later, will check the 220R, 100uf, 15k incase there is a dry joint or wrong value.

 

[Spencerleehorton]

well i'm stumped?

Q8 emitter = 0.655v ac
Q9 b = 0.655v ac
Q9 e = 0.036v ac
Q9 c = 0.158v ac, but this only settles when i twist SENS pot to open closed? (SENS pot = 50k rather than 22k)

I've checked 15k, 560R and 220R all are correct?

signal input = 0.775v (or close enough!!!) signal output = 0.160v!!

 

[abbey road d enfer]

well i'm stumped?

So am I.

Q9 c = 0.158v ac, but this only settles when i twist SENS pot to open closed? (SENS pot = 50k rather than 22k)

What do you mean "open closed"???

signal input = 0.775v (or close enough!!!) signal output = 0.160v!!

Short-circuit at the output?

 

[Spencerleehorton]

ok, success in that i've removed the 47uf at output and i get signal here now,  so will try another or happy to try something different?

Ive tried 0.47uf here but still doesn't output, gate works as it should, just need to figure why this cap is stopping the output?

 

[abbey road d enfer]

ok, success in that i've removed the 47uf at output and i get signal here now,  so will try another or happy to try something different?

Ive tried 0.47uf here but still doesn't output, gate works as it should, just need to figure why this cap is stopping the output?

Probably because you have something shorting out the output.

 

[Spencerleehorton]

There is nothing there to short?
If I attach to the collector leg of Q9 the scope and have the cap in there is no signal, if I take the cap out I get signal?

 

[abbey road d enfer]

There is nothing there to short?
If I attach to the collector leg of Q9 the scope and have the cap in there is no signal, if I take the cap out I get signal?

Look again. What is the output connector? TRS? Can you post a pic of the connector? How is it connected to the main PCB? Cable may be shorted...

 

[Spencerleehorton]

I will remove the connectors and just use the wire and see if it sorts it!!
Sorry this is so painful!!!!

 

[Spencerleehorton]

Yep you were correct! Dodgy jack plug, removed and getting clean signal through, all works as it should.
I changed the 82k to 8.2k by the 120k resistor, seems to not make too much difference but I might be wrong!!

One channel down, 3 more to go!!

 

[Spencerleehorton]

Have to laugh at myself sometimes, i'm still finishing the RM68 4 channel gates but i just figured out if i use an AUX channel into a normal channel in protools and put a gate and TRIM on that channel (i use TDM dsp plugins) i can record with gate onto the channel, no need for external outboard.