All things G1176 - the new "repost" thread.

[xsmsx]

Hi there,

what's wrong when I get -7 insted of -10 Volts near the 5532. It's a really strange thing. When I touch the trace with my multimeter I sometimes get -10 Volts and the GR-Meter shows 0dB. I already looked for breaks and soldering faults but I coudn't find the reason. By the way, I get these problems on each of my 3 Units! Does anybody know what to do???

Christoph

 

[gyraf]

I sometimes get -10 Volts and the GR-Meter shows 0dB

does the GR meter ONLY act correct when you measure -10V, or does it work always?

Jakob E.

 

[xsmsx]

It only works right when I measure -10 Volts.
Christoph

 

[robomatique]

[quote author="MrShhh"]robomatique,

Sorry for the long wait, a virus took out my internet connection for the last week!

The tester is called "peak atlas DCA" and can be bought from Maplin for £49.99:

http://www.maplin.co.uk/Module.aspx?ModuleNo=31538&TabID=1&source=15&WorldID=&doy=10m11

Easier than a multimeter for testing transistors/diodes as you don't need to know which leg is which, the tester works it out for you.

:green:[/quote]

Thanks!!!

Looks really nice! But as I understand it I could use a multimeter for this purpose? I don't have a multimeter for the moment (using one from work) and I am thinking of buying one. For the moment I am only using them for measuring resistance and check for shortcuts, but would a £25 multimeter be ok for measuring transistor hfe?

Because I need my own multimeter, £25 for a multimeter would seem more useful than £50 for the tester? Anybody?

Robert

 

[Greg]

I finished calibrating my G 1176 yesterday afternoon. I then began to just sweep through some frequencies and get a feel for how this comp operates since I've actually never used one before.

One thing I noticed is that at lower ratios (ie 4:1 and 8:1) with 3 to 6 dB or so of compression, I couldn't always get the output back to 0VU (+4dB). At 12:1 and 20:1, I didn't have any trouble getting back to 0VU. I've heard mention and read about the mods that can be done for more gain. But I just want to make sure that the operation I'm seeing is typical of Gyraf's unmodded board/output trafo. I just want to rule out this it's not something else behaving improperly. Also, the signal looks great on a scope. Can I get some insight or thoughts on this?

I will be getting it into my studio this afternoon, so I'll be able to hear it and see how it operates in my setup... can't wait.

 

[gyraf]

Christoph,

Check for cold solderings..

 

[Greg]

I got my G1176 into my studio yesterday, and I must that this compressor/limiter sounds excellent (as many of you already know). I also did some tracking last night and used it on a bass track... it held things together well and I had it working rather heavily and I wasn't hearing any kind of pumping or artifacts. And the attack times are obviously extremely fast. And it doesn't sound like any other comps I have.

But I did have a little bit of hum coming from the unit. With relation to the signal, it is very small, but there was definitely some bzzzzzz introduced from the unit that was audible when no signal was present. I'm going to try and use an extra ground strap to see if that helps. Also, with the output all the way up I was only reaching -5dB on the VU. I'm thinking I should probably try one of the gain mods.

Any comments or suggestions?!?

 

[idylldon]

[quote author="Greg"]But I did have a little bit of hum coming from the unit. With relation to the signal, it is very small, but there was definitely some bzzzzzz introduced from the unit that was audible when no signal was present. I'm going to try and use an extra ground strap to see if that helps. Also, with the output all the way up I was only reaching -5dB on the VU. I'm thinking I should probably try one of the gain mods.

Any comments or suggestions?!?[/quote]

As to the hum problem, did you reinforce the ground plane around the board via adding a buss wire and also do the "hitchhiker" cut mod to the traces? Of course, if you have mnat's board then I don't think this applies.

I did both of these and pulled a ground wire from the board and attached it to the center of the back panel via a #10 bolt/nut. I also attached the AC ground point here. The ONLY ground I have from the board to the case is this one. Even with the output trannie mod that reflects the original design (1:2), I have zero hum unless the gain on my board and power amp is insanely high (read: higher than I'd ever use it), and even then it's barely audible.

As for the output level, I like what the 1:2 mod does for the output.

Cheers,
--
Don

 

[MrShhh]

[quote author="Greg"]

Any comments or suggestions?!? (Re: hum)[/quote]

I spent a lot of time trying to rid the unit of hum and what sounded like ground loop noise. I re-routing all the ground points, did the hitchhiker cut and soldered on the extra ground strap only to find that the problem was the cheap & nasty unshielded input cable I'd used to connect the input XLR to the PCB. As soon as I used good quality cable with a braided shield, the hum and noise reduced to almost inaudible, even at very high gain settings. I also kept this cable length as short as possible to try and minimise any interferance it might pick up.

 

[idylldon]

That's one data point I forgot to add; that is, I used shielded cable as well on the input.

Cheers,
--
Don

 

[Rob Flinn]

I did both of these and pulled a ground wire from the board and attached it to the center of the back panel via a #10 bolt/nut. I also attached the AC ground point here.

The point that you make you`re star ground connection to the chassis should ideally be as close to the input socket/s as possible for least hum.

 

[Greg]

Thanks for tips guys. I'll do all of the above and check back... I'm using unshielded I/O cables. I have some Mogami shielded cable lying around that I'll use for the I/O. I already did the hitchiker cut and I'll add the grounding buss wire. I'm sure this will rid my unit of hum as well.

But I must say, the more I use this compressor, the more I love it... I used it on a session today and it's a great tool to have.

 

[Greg]

Just an update... prior to the additions suggested, I was reading about 50-75mV peak "hum" on my scope when the input and output were cranked up with no input signal. After these tweaks, I'm now reading < 5mV peak. In fact, when I simply remove the connection to the chassis, it shoots up to about 50mV peak. Once I reconnect, it drop to < 5mV peak. I haven't tried this unit in my studio, but I'm fairly confident I won't be having any hum issues. What do you guys think?

 

[Rob Flinn]

It is normal to measure hum with the input grounded. If you have both gain controls fully up with the input floating you will be more likely to pick up interferance.

 

[Greg]

Hum is gone... thanks everyone.

Now for the final thing, the output tranny gain mod.

I've got the pin assignment:
2&4 - Input (negative side of C15)
5 and 1 to 3 - Ground
6&9
10 - (+) Output
7 - (-) Output

Now do I just just take 10 (+) and 7 (-) back to the board where the original trafo was connect, which is point Y and X, respectively?

 

[idylldon]

I used Dean's instructions as follows:

If you want to try it 1:2, in and out connections should be reversed - by cutting tracks and soldering on some wires. On the primary, pin 4 should be isolated from the ground plane by cutting the wide ground trace with a dremel tool or utility knife.

The trace connecting C15 to pin 1 must be cut.

On the secondary, pins 6 and 9 need to be isolated by cutting the traces near the pins.

Solder a jumper wire from pin 4 to the solder pad for point Y.

Solder a jumper wire from pin 1 to the solder pad for point X.

Solder a jumper wire from pin 9 to the solder pad for the negative side (output) of C15.

Solder a jumper wire from pin 6 to pin 3.

That should leave the transformer running 1:2, and increase in the signal line amp's gain by 12db.

For what its' worth, I measured the transformer's output impedance, wired stock (2:1), at about 30 ohms. This is encouraging, since, when wired 1:2, the output impedance should still be well under 600 ohms.

This worked out very well for me. I finished my second 1176 and both of them are working flawlessly. I truly don't know how I ever got along without them. I'm thinking of building another pair in one box and having the option to link them.

Thanks again to all who have contributed so freely with their knowledge to this great project. I couldn't have owned one of these without being able to do it myself because a *real* one is out of my budget range right now, and most likely will be for quite some time.

Cheers,
--
Don

 

[Greg]

I went ahead and wired mine up last night with the "Chef" mod, which actually puts the tranny in a 1:1 configration (it doesn't swap the primary and secondary, but rewires them), which gives about +6dB more gain... :grin: I decided to mount and connect the tranny on perf board so I could avoid cutting traces and this would allow me to go back to the 2:1 is necessary. But this mod puts it in 1:2, which gives +12dB more gain than the original :grin: :grin: ...

Hope I'm not beating this topic to death, but would either of these mods have an advantage regarding output impedence?

 

[gyraf]

would either of these mods have an advantage regarding output impedence?

Not really. The output stage has VERY low output impedance, and will happily drive just about anything on the output side.

But you may need to take care if you used the BC327/337 as output transistors - these will probably not survive shorting the output at full level with 1:2 transformer.

Jakob E.

 

[keithcamilleri]

Hi Guys,

finished a G1176, output and input gain working fine...I'm going to test the unti for the right voltages... my problem is that it is not compressing...

any thought from where I can begin to check the unit?

Thanks

by the way It has a small bzzzz to it but I havent earthed anything still...

 

[idylldon]

[quote author="keithcamilleri"]. my problem is that it is not compressing...

any thought from where I can begin to check the unit?
[/quote]

Double check all the solder joints and wiring. The first one I built didn't compress and it drove me crazy trying to track down the problem. It turned out to be a bad Lorlin switch. After changing it, the unit worked flawlessly.

Cheers,
--
Don