All things G1176 - the new "repost" thread.

[keithcamilleri]

thanks idylldon..

for your reply....

Maybe this narrows it down... at point 7 the voltage are not changing , I cheked point 21 and voltages there goi between -5 -2 approx..so there it's looking that is working fine...

the gr tracking setting is not done since the unit is not doing gain reduction all other setting are done...

Thanks

 

[idylldon]

I'm curious as to what fuse values everyone is using. It seems as though the UREI schematic says 1/4 amp for 125V (though the schematic is hard to read and it doesn't specify fast or slow blow), the Purple Audio schematic says 1/8 amp--slow blow, and the North American Parts List gives a Mouser number that is a .375 amp fuse.

Is there a consensus on the rating? Fast? Slow?

Thanks,
--
Don

 

[gyraf]

Keith,

First of all - does point21 change with signal level?

There is a "threshold" - the negative voltage at point21 - that has to be overcome by input signal level before the FD333 diodes starts to conduct.

Input a loud signal, input at max, and measure changing DC voltage at point21. When this voltage is some +0.6V higher than the DC voltage at point19 (which is set by Q-bias), the diodes conduct, and gain-reduction sets in. Start out with trying different settings for your Q-bias, just in case it is at one extreme.

Does meter and gain change with Q-bias adjustment? This verifies that the FET's and the release circuit is working.

Jakob E.

 

[keithcamilleri]

hi jakob,

i'll check if point 21 changes with signal...it sure does change without signal...

Input a loud signal, input at max, and measure changing DC voltage at point21. When this voltage is some +0.6V higher than the DC voltage at point19 (which is set by Q-bias), the diodes conduct, and gain-reduction sets in. Start out with trying different settings for your Q-bias, just in case it is at one extreme.

I will try this tonight

as regarding if the meter and sound level changes qith q bias trimmer yes it does change...

 

[gyraf]

as regarding if the meter and sound level changes qith q bias trimmer yes it does change...

Which means that the FET attenuator part is OK, but just not receiving any control-voltage from the rectifier circuit..

If voltage changes correctly with signal level minus threshold at the output of the two diodes, then check that your attack pot is correctly mounted and working. This is the only component between rectifiers and the FET gates.

Jakob E.

 

[keithcamilleri]

Hi Jakob,

had a bc107 soldered badly...now the unit is compressing but I can't calibrate it since I don't have enough tools... and my DMM died on me yest... aaaagggrrrhhhh...

I'm not convinced that it's working well I'll post some voltages here later today...

 

[radiance]

Today I did the Fet matching thing using PRR's setup.
After putting the transistors in the wrong way for some time (I hope it did not fry them) I got the hang of it. I got values between 4.71v DC and 7.42v DC (matching the BF245A FET Transistor).

Q) How well should I match for building a stereo 1176. Is for example 6,51v DC and 6,40v DC close enough or is this way overdone?

Also, what about the other transistors like the BD517 ,BD518 and the BC560 , BC107, should I match them as well? And if so, can I use PRR's setup for this?

Thanks

 

[gyraf]

Rad,

Q) How well should I match for building a stereo 1176. Is for example 6,51v DC and 6,40v DC close enough or is this way overdone?

The "real" 1176's are known to not track well. I'd say 6,51V and 6,40V is close enough - after all the last bit of trimming is what the 1176SA stereo-adapter is for..

Also, what about the other transistors like the BD517 ,BD518 and the BC560 , BC107, should I match them as well? And if so, can I use PRR's setup for this?

No. These are non-critical.

Jakob E.

 

[radiance]

Thanks Jakob!

 

[keithcamilleri]

Hi guys,

finished up two 1176s ..just calibration needed. Made the romejesus cut to the board and done ground reinforcement (the hum is very very very low) but there is a hiss not loud but it's there... just wanted to ask whether anyone got rid of this hiss...

units still not grounded yet to the cases (no star ground , and no shieled ins and outs....)

thanks

 

[gyraf]

Some hiss is a part of any FET compressor..

 

[keithcamilleri]

cheers jakob :green: :green:

gonna do the calibration I'll post pics later...

thanks dean, jakob and orson and everybody learned loads by reading your posts :thumb: :thumb: :thumb:

 

[daArry]

Hey

Right, got me boxed near done! time to calibrate...which i've never done before - not with any audio hardware...

So, from readin the gyraf site I rek I can handle tests 1, 2 and 3...but 4 is where the headache starts...How/where do i get a 50mV signal from? IS this what those scope things do i take it ye? I have a PC and a multimeter - can i do nefin with these? I can send out tones n shit at specific levels n meter on the box too...

Do i really need to do this? the damn thing sounds great as is! :green:

- I would like to understand a lil more tho :thumb:

Cheers

D

 

[keithcamilleri]

hi guys,

I'm in the process of calibrating, but or I am doing something wrong or the 1176s (both of them) are not working as they should. :sad:

Q BIAS SETUP

I am putting a 1khz .775mv , I'm adjusting the output and input to get a voltage reading 0.875 for +1db used the formula db = 20(log[v1/v2]). (Hope I used it right I'm not great in maths :roll: ) IS THIS RIGHT?

This sets up the gate of q1 around -.9 mv.

GR Tracking

I can't get unity gain here it's seems that there isn't enough gain to get the 50mv that I'm putting through.

Am I doing anything wrong in the q bias setting?

cheers

 

[idylldon]

[quote author="keithcamilleri"]hi guys,

I'm in the process of calibrating, but or I am doing something wrong or the 1176s (both of them) are not working as they should. :sad:

Q BIAS SETUP

I am putting a 1khz .775mv , I'm adjusting the output and input to get a voltage reading 0.875 for +1db used the formula db = 20(log[v1/v2]). (Hope I used it right I'm not great in maths :roll: ) IS THIS RIGHT?

This sets up the gate of q1 around -.9 mv. [/quote]

Seems you're going the wrong way. Here's the method I used with an addition at the end (kudos to those who posted this initially):

Here is Kdawgs procedure:

Q Bias
Release: Fully CW (Fast)
Attack: Fully CW (Fast)
Input: Fully CCW (off)
Output: Fully CW
Ratio: 1:4
Meter: Bypass
Q bias: fully CCW

Signal Generator: 0.245 V (AC) sine wave 250 Hz
Measuring across input pins 2 and 1 & 3 for ground

1. Turn up input control until I get 0.100 V AC, measuring across output pins 2 and 1 & 3 for ground

2. Rotate Q Bias until reduced to 0.089 V AC across output. [ 1 dB = 20 log (0.100 / 0.089) ]

kdawg, when you adjusted the Q-bias, did you remember to turn the q-bias trimmer fully counter clockwise, before turning up the input control. This is not mentioned on the Gyraf site, but mentioned in the manual. If you forget this you will end up with the problem you describe.

GR Tracking

I can't get unity gain here it's seems that there isn't enough gain to get the 50mv that I'm putting through.

Am I doing anything wrong in the q bias setting?

cheers

Get the Q-bias setting right and then try again. When my unit did what yours is doing, it turned out to be a bad Lorlin switch, but it seems highly unlikely that your problem is the same.

Hope some of this helps.

Cheers,
--
Don

 

[keithcamilleri]

hi don,

Thanks loads man :thumb: :thumb: ... one of the 1176 is workin fine now...the other one is not behaving well. I made the qbias settings on the second one but I still cannot reach unity gain when doing the gr tracking settings and the compression is not working well, it's like compressing for a few seconds then the compression just goes.. any ideas?


cheers

 

[radiance]

I'm about to order parts for this project and I was wondering what kind of resistors everybody is using. Are they metal film (1%) resistors? Or are the carbon 5% ones sufficient?
I'm asking because I have some carbon 5% resistors left from the SSL project.

More in general: do metal film resistors make better sound quality because they match the value closer, or because of the stuff they're made of?

 

[idylldon]

[quote author="keithcamilleri"]hi don,

Thanks loads man :thumb: :thumb: ... one of the 1176 is workin fine now...the other one is not behaving well. I made the qbias settings on the second one but I still cannot reach unity gain when doing the gr tracking settings and the compression is not working well, it's like compressing for a few seconds then the compression just goes.. any ideas?
cheers[/quote]

Sorry I didn't respond sooner, but I didn't see this post until now. For some reason, the email notification must've burped and forgotten to remind me when someone posts to this thread.

Have you got that second one working yet?

Radiance: While I won't get into the audiophile discussion about different resistor types, I think it's safe to say that metal films are generally considered quieter in a circuit.

Personally, I tend to use metal films in my studio "projects" because of this.

Cheers,
--
Don

 

[radiance]

Thanks for the answer idylldon.

 

[keithcamilleri]

Hi Idylldon,

no luck yet the first one is working great but the second one is not.. it's compressing I know it is because when I set up the qbias full ccw i can hear it working... I'.m a bit lost I can reach unity for the ratio settings...


cheers