All things G1176 - the new "repost" thread.

[orson whitfield]

[quote author="deanp920"] I have my star point set at the mounting screw for the input XLR. This is the spot called for by Jakob. Make damn sure you clean this spot to bright metal to ensure a SOLID electrical connection. When it comes to grounding, think BEEFY. Think BLACK HOLE for electrons. Make sure the panels comprising the chassis are making solid electrical connection with each other. Play with it to see if you can make an improvement and if you can't go back to what you had originally. Sometimes I'll use a length of heavy, tinned buss wire that I'll solder between various 0V, or ground, locations to try and get some clues about what helps. ....Try using the input XLR screw as star ground first. Put the heavy buss wire off the PCB here and the IEC ground here. [/quote]

Thank you Dean. You know I was wondering yesterday about that "bright Metal " point you made. It seems to me the enclosure I bought, which is the very one Jakob lists, should be abrased to ensure good contact - "Black Hole" for the star ground point. I will do this and I will try the input XLR screw as star ground. Thanks again. Oh, by the way, I assume you don't have this hum. Do you?

Jakob,

Since I have the same enclosure you used, I thought I would ask you this. When they manufactured this case do you know wether they painted over it after assembly or before? If before, perhaps I should abrase spots on each panel corner and solder buss wire connecting each panel for better results?

 

[keithcamilleri]

hi guys...

I would like to now whether the g1176 responds to compression faster then the original urei?

I.ve worked with the original one and ts a great comp but it is a bit slow has anyone compared the original with the g1176?

(promise last question0 how does it sound?

sorry 4 all th questions just want some info before I begin this project.

cheers..

 

[deanp920]

Orson,

Oh, by the way, I assume you don't have this hum. Do you?

Yes I do. It is so low in level now that I can't hear it unless I crank my monitors or a headphone amp to max. Same or less than the 'hiss' produced by the G1176 circuit amplifiers. Much less than a typical tube guitar amp. But that tiny bit of hum was really loud before I got the grounding sorted out with the buss wire et all. It behaves in the same non linear fasion you describe by turning the output knob. Others have mentioned this also.

I will do this and I will try the input XLR screw as star ground.

I hope that helps, but be prepared for it to get worse as well. Every chassis is different, and chasing ground loops is a form of black magic if there ever was one, at least for me. You can change the seemingly most subtle aspect of the grounding plan and have the hum just vanish, or get much worse.

Have fun :grin:

Dean

 

[orson whitfield]

[quote author="deanp920"]Orson,

Oh, by the way, I assume you don't have this hum. Do you?

Yes I do. It is so low in level now that I can't hear it unless I crank my monitors or a headphone amp to max. Same or less than the 'hiss' produced by the G1176 circuit amplifiers. [/quote] Hmmmm.... this makes me wonder if, perhaps, I should have left things alone. Your description of your units function , wait a minute , let me restate that, that sounded weird. The behavior of the sound of your G1176 sounds like what mine was doing. Perhaps I was being too critical? Well, actually I can hear it without my headphone amp totally cranked but its very low. I'll keep trying to get it better. If not Ill go back to the scheme I had before. And once more the cover comes off....

 

[Zee1usa]

Hello Dean and all,

I finished tuning up my G1176.

FYI

While doing my "GR meter Track" calibration the potentiometer
was not adjusting at all down to -6dbu per the Gyraf website
calibration procedure, so I looked at the schematic and noticed the
BF245A in the circuit and thought I should change it. Changing it fixed the problem.

I know about ESD and I was very precautious when stuffing my pcb.
Also, I know the 2 second rule (in and out) with the soldering iron just enough for the solder to completely flow to not overheat the components that are sensitive. I am not sure if they were damaged as DOA
or if I damaged them (most likely) but I sure find this strange
as I tried to be as careful as possible? :roll:

Any one have any input on this Fet being a sensitive little guy?

I know i have seen circuits in the past where a certain Fet/transistor
was the most sensitive to ESD in the circuit and it was the only component that would be bad, even thought the production
staff was regularly updated on ESD procedures.

Did'nt jakob suggest to socket these things possible due
to their sensitivity (BF245A) ?

Oh well it seems to work now...

Now off to go see if it has any hum I need to tend to...
Oh ya and to squash some signals too! :thumb:


:guinness: :green:

 

[deanp920]

Zee,

While doing my "GR meter Track" calibration the potentiometer
was not adjusting at all down to -6dbu per the Gyraf website
calibration procedure, so I looked at the schematic and noticed the
BF245A in the circuit and thought I should change it. Changing it fixed the problem.

Back on the old thread at RO, I believe Jakob mentioned that the BF245A was prone to damage by ESD.

However, the problem you mention here might have been caused by a mismatch in cutoff voltage between Q1 and Q10. The BF245A's vary considerably, and it is definitely easier to adjust when they are matched. Too great a variance makes it impossible. Of course, Q10 may have just been fried like you said.

I like a socket for both Q1 and Q10.

Now off to go see if it has any hum I need to tend to...

Let us know how your hum and noise is. Are you using a board from Gustav?

Dean

 

[nwsoundman]

I hope my parts aren't zapped!! :grin: :shock: :grin:

 

[Zee1usa]

[quote author="nwsoundman"]I hope my parts aren't zapped!! :grin: :shock: :grin:[/quote]

Not to worry nwsoundman, I used both your BF245A

I better order a couple more :grin:


The good news is, I think my G1176 is working ?!?!
I does have a "hiss" to it when the gain is cranked.
Seems to be no hum, other than maybe a very tiny
minute amount of 60 cycle which may be normal?

Dean said: Are you using a board from Gustav?

YES... I am.






Z

 

[al_p]

hi

has anyone made any progress with linking 2 G1176s? i know Kdawg is working on this and some others have briefly described proceedures. has anyone implemented anything with promising results?

 

[orson whitfield]

I have relocated the star ground to the input XLR screw. This has not helped but increased the hum just a tad. So far the best place I have found is the IEC screw. Oh well, if I adjust the output of the G1176 and the input on my mixer I can get it to where it is tolerable. I like to go in as hot as possible but in this situation it's better not to. I wonder if the tranny modification added more hum than would be there ratio wise with out it? I can't remember where, but there as a gentlemen here posting the results of his PCB design that changed the ground trace that was more quite. I noticed he has it cut so it doesn't go around the whole PCB. Would that help us in our situation if we cut the ground trace with a dremel?

 

[Rob Flinn]

Orson

I have been experimenting with the grounding theing.

Chef cut the ground traces to isolate the PSU & audio grounds & then star earthed them. He said it sorted the problem

I`m a bit cautious so I made one cut near the meter/meter lamp connection & the hum is better than it was before. It took some lumps that appeared on the scope out. I`m not sure if its totally cured it cos the desk that I`m using to check it is a bit flaky, so I`ve got to check it elsewhere to be sure.

I hope this helps!

 

[deanp920]

al_p,

has anyone made any progress with linking 2 G1176s? i know Kdawg is working on this and some others have briefly described proceedures. has anyone implemented anything with promising results?

Yes, I have two linked and they work great. I matched all the BF245A's, then linked point 7 of each circuit directly via a toggle switch that selects between stereo/dual mono. No problem.

Orson,

I wonder if the tranny modification added more hum than would be there ratio wise with out it?

I could be dead wrong here, but I'm pretty sure that without the tranny mod you would have nearly the same hum issue, combined with a frustrating lack of makeup gain. The stock OPT will yeild better S/N, but I'm afraid it might not directly address the hum issue you're dealing with here. I know the ground loop hum I had in the beginning was just as irritating with the stock OPT wiring. Try and see.

What size and type of wire do you have soldered around the PCB perimeter? Is it tacked in several places, or soldered all the way around with a continuous bead? Where does it start and stop?

Zee,

Seems to be no hum, other than maybe a very tiny
minute amount of 60 cycle which may be normal?

Is this result with no added modifications to the stock PCB grounding scheme?

Dean

 

[al_p]

[quote author="deanp920"]Yes, I have two linked and they work great. I matched all the BF245A's, then linked point 7 of each circuit directly via a toggle switch that selects between stereo/dual mono. No problem.[/quote]

cool good to know. thanks. here's an easy question. how are you guys matching the FETs? is there a test jig i could set up for this? or is it just putting them in the circuit and testing voltages?

 

[Zee1usa]

Hello Dean,


[quote author="Rob Flinn"]
Chef cut the ground traces to isolate the PSU & audio grounds & then star earthed them. He said it sorted the problem

I`m a bit cautious so I made one cut near the meter/meter lamp connection & the hum is better than it was before. It took some lumps that appeared on the scope out. I`m not sure if its totally cured it cos the desk that I`m using to check it is a bit flaky, so I`ve got to check it elsewhere to be sure.

I hope this helps![/quote]

What do you think about doing the above rob flinn/chef mentioned
about isolating PSU and Audio grounds and starring them?


Dean wrote:

What size and type of wire do you have soldered around the PCB perimeter? Is it tacked in several places, or soldered all the way around with a continuous bead? Where does it start and stop?

Dean, I used a 12AWG soldered around the perimeter tacked on in about
8 places but not with a continuous bead. Would a countinuous bead be better? Jakob mentioned I believe this was not needed and he thought it would just look ugly.



Zee, Quote:

Seems to be no hum, other than maybe a very tiny
minute amount of 60 cycle which may be normal?

Dean Wrote:

Is this result with no added modifications to the stock PCB grounding scheme?

only mods are :

perimeter 12 awg tacked on in 8 places.

I have a ground LUG which has a ground from each of these points:

1) AC main.

2) direct from pcb ground/perimeter 12awg.

3) 4th chassis pin from XLR input wich is jumpered to 4th chassis pin on output XLR.


I have been thinking of any possible changes to this ground scheme
that would be for the better.

I have seen a note on Gyraf site that says:

"- Make sure that the centre tap of the 2x24V at the power transformer is connected to ground"

"- Connect 0V/Ground to chassis at - and only at - the input XLR(F) connector. Here you can also connect the mains power ground from the IEC power connector if you need that"

1) I am thinking that I may have my XLR grounded improperly

2) Should I not go to star ground direct from pcb perimeter ground
plane? Or is this ok.

3) what about ground on the toroid? It is already going to the pcb which goes straight to the ground plane, I think this should be sufficient?

4) potentiometer should be grounded? My input and output is conductive plastic (bourns 90 series) but attack and release are (Alpha) which are metal. Should these go to ground other than the (1,2&3) wires that go to their normal place on the pcb?


Thanks Dean!

Thanks for the info on the stereo connection as well.

:grin:
Z

 

[Rob Flinn]

Zee, Quote:

Seems to be no hum, other than maybe a very tiny
minute amount of 60 cycle which may be normal?


This is not normal. I & a friend have done a side by side comparison with a pair of revision H UREI`s & the g1176 (in standard form) has noticably more hum. The revision H circuit is very simlar to the G1176 without input transformer.

 

[orson whitfield]

Well, I haven't refered to the AWG and measured thickness of the wire I am using but it is soldered ALL THE WAY AROUND the PCB perimeter. I haven't cracked open my G1176 yet to see where I started and finished it either. Today I 'll get to that and then post the info here. I am using thin wire for the rest of my grounding scheme. I will try thicker wire and see if this helps. I am tempted to cut traces but I'll be abstemious with the Dremel till I hear more.

 

[deanp920]

Z,

What do you think about doing the above rob flinn/chef mentioned
about isolating PSU and Audio grounds and starring them?

I can't comment because I have not tried it. I am satsfied with the arrangement I currently have:

No. 14AWG tinned copper busswire soldered around perimeterw/ continuous bead, starting/exiting between the pads for input/output XLR connections.

This wire goes to a lug I fastened on the mounting screw for the input XLR. AC mains ground here as well.

That is all I have done. Hum is less than hiss.

Z wrote:

Dean, I used a 12AWG soldered around the perimeter tacked on in about
8 places but not with a continuous bead. Would a countinuous bead be better? Jakob mentioned I believe this was not needed and he thought it would just look ugly.

That is probably as good as it gets. I got a very tiny improvement with a continuous bead, but you're using #12 wire compared to my #14.

Z wrote:

Seems to be no hum, other than maybe a very tiny
minute amount of 60 cycle which may be normal?

If the hum is below the noise floor of the circuit(which is relatively high, compared to modern gear), then I would say you're good to go.

Z wrote:

3) 4th chassis pin from XLR input wich is jumpered to 4th chassis pin on output XLR.

Not really necessary; try with/without to see if you get some improvement.

3) what about ground on the toroid? It is already going to the pcb which goes straight to the ground plane, I think this should be sufficient?

Yes, you've already got it at the PCB.

) potentiometer should be grounded? My input and output is conductive plastic (bourns 90 series) but attack and release are (Alpha) which are metal. Should these go to ground other than the (1,2&3) wires that go to their normal place on the pcb?

It is OK if the metal pots form a connection to the chassis through the standard mounting. You don't need to do any extra grounding on any of the pots.

2) Should I not go to star ground direct from pcb perimeter ground
plane? Or is this ok.

Yes, this is really the one and only wire, besides the AC mains, that should go to star ground.

I am thinking that I may have my XLR grounded improperly

Use 2 conductor sheilded wire; pins 2&3 use the two conductors to the PCB, and the sheild connects pin 1 to the PCB.

Rob Flinn wrote:

Zee, Quote:

Seems to be no hum, other than maybe a very tiny
minute amount of 60 cycle which may be normal?


This is not normal. I & a friend have done a side by side comparison with a pair of revision H UREI`s & the g1176 (in standard form) has noticably more hum. The revision H circuit is very simlar to the G1176 without input transformer.

Rob, when you refer to the G1176 in standard form, is that without a heavy wire soldered around the perimeter of the ground plane?

Dean

 

[Rob Flinn]

Rob, when you refer to the G1176 in standard form, is that without a heavy wire soldered around the perimeter of the ground plane?

Dean

Yes & also without any of the Chef grounding mods. Just the straight PCB.



I`m intrigued by your method of soldering a heavy wire round the board perimeter. This souinds quite a job if the board is professionally made with a solder mask.

 

[orson whitfield]

OK, I used thicker wire ( 12 guage copper ) and I went back to the original grounding scheme. Definately lowered the hum. The hiss is louder than the humming. But then again it was before aswell. But this is a marked improvement. When I turned the output knob full CW the hum was more noticable before. Now it's hardly noticable at all. This makes me happy. I don't know where I started and ended the PCB perimeter wire or what Gauge it is but it's definately not 12 guage. It's a little thicker than standard hook up wire. By the way my grounding scheme is as follows. Mains IEC ground and PCB perimeter ground meet at the middle of the jumper wire connecting xlr input and output pins number #1 ( I believe but not sure about the number) . Then from that point to the IEC screw connected to the chasis which I guess would be called Star Ground.

 

[deanp920]

Orson,

OK, I used thicker wire ( 12 guage copper ) and I went back to the original grounding scheme. Definately lowered the hum....I don't know where I started and ended the PCB perimeter wire or what Gauge it is but it's definately not 12 guage. It's a little thicker than standard hook up wire.

:?: So, what wire did you replace with #12?

When I turned the output knob full CW the hum was more noticable before. Now it's hardly noticable at all. This makes me happy.

Alright! :grin:

I`m intrigued by your method of soldering a heavy wire round the board perimeter. This souinds quite a job if the board is professionally made with a solder mask.

I'm certainly not the person who came up with this idea originally; for sure, bluebird did it on his as well as some others who I can't recall at the moment. I think Jakob may have been the first to suggest it, though I believe that using such a heavy guage may have started with me. My board is home built, so soldering the wire all the way around was no problem...I tacked it first, then came back and ran the bead.

I think using #14 solid copper or heavier is important for best results.

Zee1usa has a board with the solder mask, and it appears that he used #12 wire and just tacked it in several places(~8?) around the perimeter where I'm assuming the solder mask was scraped/sanded/filed off.

Just how did you do it, Z? Also, Z, did you ever try Gustav's board without the extra ground wire to see if it had an inherent hum issue?

Dean