All things G1176 - the new "repost" thread.

[a2d]

when turning the release pot it causes the meter to swing from +2  to -20?? has anyone had this problem??
when  in GR mode or in bypass mode

 

[gswan]

I am interested in the relationship the Attack pot has on the compression circuit however. I used Lin 25K pots for attack in this unit and I noticed a difference in the behaviour between my unit and the "real thing" particularly when fully counterclockwise, and in slam mode.

Can someone help me to understand why the BOM states Lin or Log. Wouldnt this make a difference to the way the signal is presented to the GR circuitry?

The Lin or Log type refers to the taper curve, ie how much resistance there is from a particular ens of the pot and the wiper for a given rotational position. However the values at the end points still remain the same (0 or 25K). It just means that different attack time values from those marked on the front panel will be present if a log pot is used. Same goes for release.

Also, the other noticable difference is that often my gain settings when in GR mode make it hard to flick the "bypas" switch without the output jumping up several dB, and making me grab for the faders. Is there a way of pading the bypass so that it permanently reduces output by say 3 or 4 dB? Anyone else tackled this issue?

If you have gain 'reduction' in play and you bypass it you would expect the gain to go up (ie you are no longer reducing the gain with the FET), unless you had the makeup gain (output pot) set to bring the gain up to the bypassed signal level.

 

[gswan]

when turning the release pot it causes the meter to swing from o  to -20?? has anyone had this problem??
rev J

Is this when measuring gain reduction?
Sounds like a wiring problem.

 

[a2d]

yes in GR mode or bypass mode
on the low side of the release pot there are 2 wires one goes to the ratio board and the other goes to pad 18
nothing on the wiper except the resistor,
on the high side of the release  pot  there is 1 wire that goes to the attack pot
on the low side of the attack pot there is a single wire that goes to pad 19
on the wiper there is a resistor and a cap
on the high side of the pot gets connected to the release pot high side

 

[gswan]

Could also be a cracked pot.

 

[a2d]

a cracked pot??? it seems to change resistance throughout its travel, measures out ok

 

[gswan]

If you get a step change like that when slowly changing the wiper position it is a good indication of dirt or damage to the pot.

 

[a2d]

ok I'll get a new one on Tuesday and see what happens
I really don't think its the pot,but who knows
when I turn the release CCW the needle goes to -20 and stays there,
and when I turn it CW it goes to +2 and stays there,???/
the needle seems to follow the position of the pot
Its an interesting one, my voltages seem to be ok +/- .5V

 

[Chrome Heart]

Hello all
Im using mnats rev. J board and I have the Hairball meter with 12v lamp. I was going to just take the power from the "VU Lamp" feed on the PCB. Its showing 30+ volts on the meter from that point. I think I read something about a 220 OHM 5W power resistor to get the voltage in the neighborhood. Anyone using this setup? How is the lamp brightness?
I wish I could just go to Resistors R Us and get a few to check out.

 

[gswan]

ok I'll get a new one on Tuesday and see what happens
I really don't think its the pot,but who knows
when I turn the release CCW the needle goes to -20 and stays there,
and when I turn it CW it goes to +2 and stays there,???/
the needle seems to follow the position of the pot
Its an interesting one, my voltages seem to be ok +/- .5V

Sounds like a wiring error then. Your description does not sound like a step change so it's unlikely to be the pot. The pot should not change what is seen on the meter unless you are changing the voltage going to the gate of the FETs.

 

[mac]

Hey Chromeheart,
I figured it out like this,
R = (30 - 12) / 0.02 = 900ohm. So you could use 910ohm resistor, if my maths is right.

Have a look at the the J board though, because if you are using Mnats separate power supply, you can still populate the components between where the 30v feed comes onto the main board and the VU power feed leaves the board - thats what I did for my meters. Look around C23, R89, R87 (from memory - mine is bolted into my studio rack now  ;D, and I am avoiding unbolting it and taking the lid off).

Mac

 

[mac]

I nearly forgot...thanks for your response too Geoff.

If you have gain 'reduction' in play and you bypass it you would expect the gain to go up (ie you are no longer reducing the gain with the FET), unless you had the makeup gain (output pot) set to bring the gain up to the bypassed signal level.

I guess I just noticed that the comparison is more noticable than the original when you apply the same signal source and compression settings. Makes it hard to A/B when listening for siblance etc.

If I did decide to pad by a few dB - could this be as simple as a small pad circuit fed off my"bypass" toggle switch, thus reducing signal to the outputs when the unit is in bypass?

Mac

 

[gswan]

Hello all
Im using mnats rev. J board and I have the Hairball meter with 12v lamp. I was going to just take the power from the "VU Lamp" feed on the PCB. Its showing 30+ volts on the meter from that point. I think I read something about a 220 OHM 5W power resistor to get the voltage in the neighborhood. Anyone using this setup? How is the lamp brightness?
I wish I could just go to Resistors R Us and get a few to check out.

You could just use one of the 25Vrms secondaries and power two 12V lamps in series with it, unless you only have one lamp in there.

 

[Chrome Heart]

Yeah, its one lamp.

 

[Chrome Heart]

Well Ive fired up the comp and Im a bit shocked, it works!   All functions seem to work properly including the slam mode thanks to mnats switch pictorial. Ive managed the Q Bials as per the calibration procedure, and meter 0 adjust. I seem to be running out of adjustment room with the input and output pots during the tracking adjustment. Im using 10K Mouser PN 31VJ401-F on the In and 100K 31VJ501-F for the out. I have also shorted pin 22 to ground for half the test. Any pointers are much appreciated.
cheers
BR

 

[mac]

Well done BR, - congrats.  The wiring is a bit of a killer eh!!

these things sound great - heaps of gain. Not sure what you mean by running out of room on your tracking adjust.
Mac

 

[Chrome Heart]

hey mac
I thought the wiring would be tougher than it was, I guess because it works When I try to make the adjustment for tracking, I either run out of pot for output or input, that is to say, I cant turn it up enough to get it to 0db on output. or down low enough to get it to -10. Are the pot values correct?

 

[a2d]

for the tracking adjustment you don't change the level on the 1176, you turn up your source input (OSC)

 

[a2d]

ok I'll get a new one on Tuesday and see what happens
I really don't think its the pot,but who knows
when I turn the release CCW the needle goes to -20 and stays there,
and when I turn it CW it goes to +2 and stays there,???/
the needle seems to follow the position of the pot
Its an interesting one, my voltages seem to be ok +/- .5V

Sounds like a wiring error then. Your description does not sound like a step change so it's unlikely to be the pot. The pot should not change what is seen on the meter unless you are changing the voltage going to the gate of the FETs.

well I looked at the wiring again everything seem to be in its place, I'm really not sure

 

[Chrome Heart]

for the tracking adjustment you don't change the level on the 1176, you turn up your source input (OSC)

Interesting. I did not read that in the calibeation pdf. If it says to do that it certainly isnt clear to me.