The official G9 help thread

[JingleDjango]

Looking over all the pictures people have posted here of their internals, I keep seeing what looks like full mic cable with thick, thick insulation running to and from the XLR jacks on the back panel. I have a bunch of Mogami console cable (Seen here:http://www.mogamicable.com/category/bulk/console/) that I bought for use in my Hairball/MNATS 1176. I imagined this would work perfectly well for the G9 but I just wanted to double check. The conductors are quite narrow, if that makes a difference.

 

[gyraf]

The only place you really want shielded wire is between trace-cut-modification and frontpanel jacks.

Jakob E.

 

[JingleDjango]

Couple questions about the power supply chain:

1) It's been suggested that the two toroidals be mounted one on top of the other. To accomplish this, would you just find a bolt roughly twice as long as the ones supplied with the transformers and stack them? Would there be any reason not to mount them like this, horizontally from the side of the enclosure? I'm trying to avoid having a bolt sticking out the bottom of my enclosure that might scrape other devices in my rack.

2) I haven't got my PCB delivered yet, but I was planning on wiring the transformers (including ground to pin 1 of XLR input 1) and stuffing only PSU section of the board first, to check for faults before continuing with the remaining parts. Does this sound wise, or more a waste of time?

Thanks again.

 

[JingleDjango]

deepdark, did you have success with the heatsink in your Mouser cart? Did you mount it directly to the VR on the PCB? Compared to all the heatsinks I've seen in images here, it seems very small.

 

[Deepdark]

Honestly i decided go not use it, and install the regulator straight on the case, with insulator between the reg and the case. This heatsink came from a previous bom i found over here, can't remember who made it. I must have had success with it if he put it on his bom

 

[JingleDjango]

Do you find the back of your case gets very hot to the touch with it mounted like that? I've been poring over Mouser looking for a bigger heatsink that would mount flush with the back panel but so far I haven't seen anything just right.

 

[gyraf]

Using case as heatsink is fine - we're not dissipating that much heat.

Just remember to isolate - and check isolation with a continuity tester before power-up.

Jakob E.

 

[JingleDjango]

Thanks again.

 

[Deepdark]

Just a thought about the grounding. The way it has been thought is to use the input xlr 1 pin 1 as the main exit and then we strap it to IEC bolt. Right?

What if we decide to use the 0v connection, used to C14/15 0v connection, and strap it to the IEC bolt, and simply connect xlr's pin 1 to chassis, in a classis way? The way I see ground is to separate what is shield and what is signal ground. Shield go to the chassis with the minimum lenght as possible (that include shielded cable connected at xlr's pin 1, transformer shield, etc). And signal ground is taken in a hierarchical manner from input to output, take the psu ground and then go to IEC bolt. Input is as far as possible from the HT input, output is as close as possible to the HT input. I know shield has been sent to signal ground in the design and for what I see, ground isn't taken in a hierarchical manner, so I wanted to know if what I suggest (using 0v tap to connect to IEC and strap XLR's pin1 to chassis) would work? I know there is some manner to manage ground so I wanted to validate if there was other way of managing the gorund in the G9. Simple curiosity  ;D

 

[gyraf]

There are probably many ways we could arrange a good grounding in the G9 - but there are also extremely many solutions that would create problems of all sorts.

So the suggested solution is not by any means the only right one - just one that has been tested and is known working.

Jakob E.

 

[Kir_For_Pleasure]

Listen to the clips, you can hear the lack of bass and hiss from the G9 preamp
Is this normal ? About seven years ago i built the G9, have tear it apart several times
Tried to come up with something to get it quiet with help from posts here on the lab but nothing seems to help.

G9 preamp https://drive.google.com/file/d/0B2AdteJUCk4OSVBkWkhiM2FCQjA/edit?usp=sharing
Tascam M3500 https://drive.google.com/file/d/0B2AdteJUCk4OLTROYnlPUXNiRDg/edit?usp=sharing

 

[Deepdark]

How is you shielding, ground, which transformer did you used?

 

[Kir_For_Pleasure]

stargrounded as suggested with the pin 1 thing, shielded oep transformers. Metal box around power transformers(didnt do anything at all for the hiss)

 

[Deepdark]

For hiss, use shielded cable for all input and output , as well as the DI, do you made the DI mod (wiring it directly on the main board) do you twist you pair of wire as tight as possible? Are you sure the shield can is properly soldered? I mean, did you made a continuity test to be sure everything was allright? Be sure you don't cross audio wire with ht cable, etc.

 

[Deepdark]

Oh and did you tried other tubes?

 

[JingleDjango]

Deepdark:

I'm confused about the wiring of the power transformers (seems to be a common problem here). You and I have the same Triad transformers. I'm looking at Skylar's old wiring diagram. It would be easy to follow, but as you know, the specs have been updated for one 115/2x12V & one 115/2x15V transformers instead of the previous two 115/2x15V ones.

So I don't know which of these connects to my mains switch and which follows. Is it the 12V or the 15V? The wiring colours of the Triad transformers are the same as the Avels in the diagram.

 

[Deepdark]

The first one is the 15v secondary instead of the 12v. The rest is the same, same way of wiring them,  even the color code is identical. So the first transformer, the one that connect the main, is the 15v secondary one.

 

[JingleDjango]

Thank you! And I'm using a  DPST toggle switch on the mains. I'm assuming I should run Grey/Brown & Blue/Violet each to their own terminal on the switch, rather than just the Grey/Brown shown in the diagram?

 

[Kir_For_Pleasure]

For hiss, use shielded cable for all input and output
Have  shielded cables.

as well as the DI, do you made the DI mod (wiring it directly on the main board) do you twist you pair of wire as tight as possible?
Yes done that mod

I mean, did you made a continuity test to be sure everything was allright?
Not done !

Be sure you don't cross audio wire with ht cable, etc.

 

[Deepdark]

The continuiy test is to be sure the base abd the can are well connected, and once solder on the board, you can test the continuity with one probe on the can and the other on the main bolt, to be sure the shield is well grounded, so it will reject noise down the ground path.

And your lack of bass could be related to the oep transformers. They Re known to lack a little bass, not only on that build, i heard the same thing on some projects. It depends of the bass lack, of course, but a drop at about 30 to 60 hz looks typical of what people seems to encounter on that build.