FET "Grinder"

[Mazieresantoine]

i will do it tomorrow with my sound card.

On my DMM tech specs, it say : Alternative voltage measurement 40hz to 400Hz

So i generate a 200Hz and i see what happen?

O.K.,generate a sine wave lower than 400Hz and bring the output of your soundcard to a defined level,say +4dBu as it´s the studio standard.
Before pluging in the xlr to the compressor you can verify it by measuring between pins 2 & 3 again,it should give you a reading of 1,226 VAC (DMM set to AC reading of course).
Now plug it to the compressor,set it to bypass mode and measure the output xlr.You should get roughly the same voltage as on the input.If it´s in the range of 0,625 VAC you have a -6dB drop leading to a faulty input/debalancing stage.
If this is o.k. compared to the input then Gustav or anybody else (Jacob?) might chime in.As said I haven´t built this compressor version (yet),so I´m not too familiar with it.

Ok so i have 1,3VAC in the XLR input, and 0,00VAC in the XLR output
I check back the transformateur and it's OK.

 

[kante1603]

With 0 vac at the output you while feeding a +4dBu sine you would never have heard anything from it.........

 

[Mazieresantoine]

OK this because i forget to push up the input trim, so i've got 0,5VAC, it's not so muche better, and it's with 300Hz frequency, i need to have in and out at maximum.
i think it is because of my bass problem, and so i think my problem come from input stage, but maybe i'm wrong.

So maybe you know how i can check this area?or maybe you think ineed to check anything else before?

Thanks

 

[kante1603]

O.K.,the only easy thing you can do is to swap out the input receiver ic (the NE5532).This costs just a few cents.Watch the plug in direction,there's a little mark on it.
If that still does not help you have to trace the signal through the circuit until it stops.At this point somebody who has already built this may go on helping you.

Best,

Udo.

 

[Mazieresantoine]

Ok I will try it tomorrow,

Do you think it can come from the BF245?
i'm not sure about him, I will change it to.

 

[kante1603]

Ok I will try it tomorrow,

Do you think it can come from the BF245?
i'm not sure about him, I will change it to.

One after the other please.

Udo.

Edit:0,5vac equals roughly -3,8dBu,so it's way better than nothing!

 

[Mazieresantoine]

This is 0.5 because It s low frequency but with high frequency i need to shut down my input

Ans yes sorry i will change one by one

 

[Mazieresantoine]

Now when i put power on nothing happen  :'(

i have to find this now, thanks for your help for the rest, I keep you in touch

 

[frereyvan]

Hi guys.
I have just finished my Fet Grinder old layout... and it works ! Good compression, no hum, everything is ok... except the Vu-Meter.
The Gain reduction mode works fine, and the 3 trimmers seems to be fine, but for a good calibration, I need the VU mode.
In Vu mode, the needle doesn't move, or just a little when a put 1Khz at 0dB.
If my comprehension is good, the Vu mode read the output of the compressor, after the lundhal and after a resistor (1 K).
Is that right ?
I have check all the resistors before mount them, and everything was ok.
But now, the R67 gives me 52 ohms... Maybe is there a big problem with here ? It will be too noce...
Any idea ?
Thanks.
Tom

 

[Gustav]

Hi guys.
I have just finished my Fet Grinder old layout... and it works ! Good compression, no hum, everything is ok... except the Vu-Meter.
The Gain reduction mode works fine, and the 3 trimmers seems to be fine, but for a good calibration, I need the VU mode.
In Vu mode, the needle doesn't move, or just a little when a put 1Khz at 0dB.
If my comprehension is good, the Vu mode read the output of the compressor, after the lundhal and after a resistor (1 K).
Is that right ?
I have check all the resistors before mount them, and everything was ok.
But now, the R67 gives me 52 ohms... Maybe is there a big problem with here ? It will be too noce...
Any idea ?
Thanks.
Tom

If you are using a DC meter with a VU scale (like the small, round Behringer style meter). You'll need to put a bridge in front of the meter.

https://pcbgrinder.com/download/Data_Sheets/Bridge.jpg

You will want to use germanium diodes.

Gustav

 

[Gustav]

Now when i put power on nothing happen  :'(

i have to find this now, thanks for your help for the rest, I keep you in touch

My initial hunch about the connectivity may have been wrong, or some problem was added while you were trouble shooting  - Did you take the trouble to check voltages as well as pursue the help offered by Kante?

Gustav

 

[frereyvan]

It's the G1176 meter from frontpalnels.de
I don't see the difference between mine and the Behringer style... ?
And about the wrong resistor ?
But thanks, i have some diode, i will try a bridge !

 

[Gustav]

And about the wrong resistor ?

Sorry, I missed that part.

You cannot rely on resistance measurements of single resistors "in circuit".

Gustav

 

[Harpo]

..the Vu mode read the output of the compressor, after the lundhal and after a resistor (1 K).
Is that right ?

VU measurement is taken between XLR-pin2 and XLR-pin3 with a 3K6 series resistor (R87) in between (and is not related to gnd).
The numbering of the output connector X2-1..X2-3 on pcb doesn't correspond with the XLR pinout (XLR-pin1=shield, XLR-pin2=hot, XLR-pin3=cold.
Maybe it is only a cold solder connection at the GR/VU meter switch.

 

[frereyvan]

Thanx, it seems to be much better with a bridge.
I start the calibration...

 

[Mazieresantoine]

Now when i put power on nothing happen  :'(

i have to find this now, thanks for your help for the rest, I keep you in touch

My initial hunch about the connectivity may have been wrong, or some problem was added while you were trouble shooting  - Did you take the trouble to check voltages as well as pursue the help offered by Kante?

Gustav

Thanks for your help, i check again the resistance value Kante say to me, but i think i have a problem with the PSU, it seems to be not very regular on the +30V

I will check again this afternoon and i come back to you.

 

[Gustav]

Now when i put power on nothing happen  :'(

i have to find this now, thanks for your help for the rest, I keep you in touch

My initial hunch about the connectivity may have been wrong, or some problem was added while you were trouble shooting  - Did you take the trouble to check voltages as well as pursue the help offered by Kante?

Gustav

Thanks for your help, i check again the resistance value Kante say to me, but i think i have a problem with the PSU, it seems to be not very regular on the +30V

I will check again this afternoon and i come back to you.

Do you have a picture of the PSU setup?

 

[Mazieresantoine]

Now when i put power on nothing happen  :'(

i have to find this now, thanks for your help for the rest, I keep you in touch

My initial hunch about the connectivity may have been wrong, or some problem was added while you were trouble shooting  - Did you take the trouble to check voltages as well as pursue the help offered by Kante?

Gustav

Thanks for your help, i check again the resistance value Kante say to me, but i think i have a problem with the PSU, it seems to be not very regular on the +30V

I will check again this afternoon and i come back to you.

Do you have a picture of the PSU setup?

This my Fet Grinder...
What i found is that i think it come from the cable between the two board, when i move them a little, the 30V leave or come back.
Now i have the 30V, but the Vumeter do what you see in the picture, and if i move the MTR-Zero trim the meter go in the wrong way (going up instead of going to the +1db in gr mode

 

[Mazieresantoine]

this is my complet compresseur

 

[Mazieresantoine]

And the VUmeter in GR mode