The official G9 help thread

[gyraf]

Agree.
Also the spaghetti will confuse readings - this is sensitive stuff. Clean up cabling, twist everything twistable, place transformers on top of each other as far away from the input transformers as possible, and try rotating them while looking for an interference minimum. Then flip the upper transformer and look for an even lower interference minimum. Once found, fix in place.

Jakob E.

 

[Graph]

Graph,

It looks to me like you experience hum with harmonics which might be still related to the transformer. What I have used to lower that is special metal sheet that aids at reducing electro magnetic fields.

Have you tried taking the two transformers outside of the case to see if it makes a positive change?
have you also done the instrument in modification suggested earlier on the thread?

I will try, i dont know if its grounding or anything else. With these transformers i couldnt try getting them further, i tried placing them on top of each other, but, there was more hum. I found them in that position to have a little less hum.

I will check the instrument input and i will clean the spaghetti Is it safe to move the transformers while the G9 is on?

Something like this will work? (i guess connected to ground)
http://www.ebay.com/itm/Mumetal-Nikel-Permalloy-Magnetic-shielding-foil-Sheet-Mu-metal-0-1T-30-45cm-/171173026902?pt=LH_DefaultDomain_0&hash=item27dab51c56
Or is it too thin?

Thanks

 

[Spencerleehorton]

Hi Guys,

Im experiencing a little high frequency interference, usually this type of sound is down to an earth loop, just wondered if there is a specific way of testing for noise which is possible as this unit sounds great but if i could reduce this noise it would be absolutely perfect.

regards

Spence.

 

[whomper]

I will check the instrument input and i will clean the spaghetti Is it safe to move the transformers while the G9 is on?

Something like this will work? (i guess connected to ground)
http://www.ebay.com/itm/Mumetal-Nikel-Permalloy-Magnetic-shielding-foil-Sheet-Mu-metal-0-1T-30-45cm-/171173026902?pt=LH_DefaultDomain_0&hash=item27dab51c56
Or is it too thin?

Thanks

I have rotated the transformers while the unit was on, but did not dare move them further away.
The link looks like the right metal sheet. I would grab it.

 

[bruce0]

I bought an engineering kit ($186) which includes three types of mu-metal two thicknesses of high permeability and one of low permeability.

Lo perm is for shielding sources (high flux levels won't saturate as easily) the high perm for shielding sensitive circuitry.  Or maybe it is the other way around.  Anyway it is much more material (3 rolls of 4 feet long as I recall) some of it is the same thickness as the ebay listing, some is thicker.

It is more expensive but much cheaper if you want to have it around, and you get both types (hi-perm and low perm)


Specs are here.

https://www.advancemag.com/purchase.html

http://www.advancemag.com/

 

[Spencerleehorton]

HI Guys,

as suspected on my main pcb it didn't have an earth connected!!! once connected high pitch interference gone and unit as quiet as a mouse. Thanks to all that helped me, its time to put this on some recordings now!!.

regards

Spence.

 

[Voodoobeat]

Hi,

i've got my g9 finished and it worked first time
But theres some audible Buzz coming from T2, thought i'm sure they are wired correct.
I've also tried another Torroid, so thats not the issue.
Any ideas?

Thanks

 

[museic]

Doing the final wiring for my g9. I'm confused on the power transformers. I have avel lindberg y236103 and connected them like skylars diagram. I didn't wire to board yet so I could measure and see the voltages. But I couldn't measure any voltage. There was 120v present coming off the switch, but no voltages from the secondaries. Any ideas what to check?

 

[museic]

Sorry scratch that question. Little mix up using my dmm. So I measure 2x 18v and 295v off the transformers. Is the 295v normal?

 

[museic]

Glad to report another working g9! All voltages were spot on once connected on first power up... Only problem is it keeps shutting down so I have a problem with the 78s12. I made a heatsink by bending a piece of aluminum and mounted it to the case. I guess what I don't understand is how to electrically isolate it? I used some paper washers but obviously it's not transferring the heat away. So how do you have it isolated but still conducting heat?

 

[Harpo]

Museic, use a TO220 insulating kit, something like http://uk.farnell.com/multicomp/mk3306/insulating-kit-mica-to-220/dp/520214
and thermal grease (using less is more) for a non-conductive heat transfer.

 

[museic]

Ok thermal grease that's what was missing. Thanks!

 

[baol]

Hi you all
I'm just starting to collect all the stuff to start a G9.
Is there a Mouser list for the components?
thank you and merry christmas
Andrea

 

[CTmusic]

All, just read a couple of stories here, just amazing how many of you are working on these projects!
However, I decided to do it a little bit different and go for a retro discrete realization.
Feel free to let me know what you think about this!

 

[gyraf]

Looking good so far...!

Jakob E.

 

[Jamie1234]

So my G9 was up and running nicely and sounding great (apart from a hum on channel 2 DI, which I hope will be solved by a bit of metal shielding but haven't got round to it yet) but it has now developed a more serious problem.. 

My mic input on channel one has developed a loud crackling noise, kind of sounds like a dodgy valve but I tried swapping the valves on the two channels and it made no difference. I've also managed to rule out mic, leads, patch bay etc.

So I was wondering does anyone have any guesses at what might be causing this before I get in there and start messing with it? It has been working fine for the last 2 months and the problem has only just occurred so i don't think its a build error.. 

Thanks

Jamie

 

[gyraf]

What DC voltage across the 10uF polyester capacitor? what's it's rating?

 

[Jamie1234]

Sorry for the slow reply, only just got round to picking it up from the studio. The voltage across the 10 polyester capacitor reads as 79v when I start measuring then drops and settles at 42v. (Sorry I'm not sure which is the relevant reading, I really am a total novice)

they are WIMAs rated at 100v

 

[gyraf]

they are WIMAs rated at 100v

Then that is not your problem.

Maybe problems in switches or relays?

Need more info: Does crackling increase with gain and/or output level? Is it the same with line input or instrument input (on the front)? With and without phantom? Have you adjusted your phantom to 48V?

Jakob E.

 

[Deepdark]

Hi guys. I'm populating the board but didn't find R38 (100R), I looked at the schematic but no more chance. Is it possible that there is no R38?