The official G9 help thread

[Bonke]

Thank you Jakob!
I must say it is fantastic that you and all the other pro´s keep helping us newbies out on this forum.
Thank you for this great project aswell!

Henrik

 

[Bonke]

Hi!
Do you guys think it will be possible to isolate the TL783 on a piece of wood like this? (it´s not connected to chassis) I ordered to big heatsink so I have to put it offboard. Or is it getting so hot that it will burn the wood? Also, it IS ok to heatsink the 78S12 to chassis right?

Here is a picture of the guts without tubes.

Henrik

 

[bpucekov]

yes

 

[Harpo]

Do you guys think it will be possible to isolate the TL783 on a piece of wood like this? (it´s not connected to chassis) I ordered to big heatsink so I have to put it offboard. Or is it getting so hot that it will burn the wood? Also, it IS ok to heatsink the 78S12 to chassis right?

What's so wrong with using a piece of mica and a TO220 isolation kit for a reliable job ? (your piece of wood will shrink from generated heat inside the box and the screw will come loose one day...)

The length of wires connecting to the off board regulators seem a little long (exceeding 3-4 inches from filter caps). Keeping the regulators stable might require additional bypassing at the regulators input terminal with a smaller cap.

Your build seems to be missing a connection between input-XLR-pin1 and 0V reference voltage to make +48V phantom work.

 

[Bonke]

What's so wrong with using a piece of mica and a TO220 isolation kit for a reliable job ? (your piece of wood will shrink from generated heat inside the box and the screw will come loose one day...)

I will get a kit next time I order.

The length of wires connecting to the off board regulators seem a little long (exceeding 3-4 inches from filter caps). Keeping the regulators stable might require additional bypassing at the regulators input terminal with a smaller cap.

Ok, so I move the heatsinks closer to the pcb and shorten the wires.

Your build seems to be missing a connection between input-XLR-pin1 and 0V reference voltage to make +48V phantom work.

I have input XLR´s pin 1 connected to starground. Is there another connection required?

Thanks Harpo for the answers!

Henrik

 

[Harpo]

Your build seems to be missing a connection between input-XLR-pin1 and 0V reference voltage to make +48V phantom work.

I have input XLR´s pin 1 connected to starground. Is there another connection required?

You have input XLR's pin 1 connected to case and safety ground.
Additionally connecting 0V reference voltage from your +48V psu to this junction (starground) will provide the else missing current return path for phantom voltage.

 

[Bonke]

Your build seems to be missing a connection between input-XLR-pin1 and 0V reference voltage to make +48V phantom work.

I have input XLR´s pin 1 connected to starground. Is there another connection required?

You have input XLR's pin 1 connected to case and safety ground.
Additionally connecting 0V reference voltage from your +48V psu to this junction (starground) will provide the else missing current return path for phantom voltage.

I am sorry for not understanding this but isn´t 0V connected via the "gnd" on the input-connection on the pcb?
My input xlr´s pin 1 is connected to "gnd" on the input-connection on pcb and also to starground on chassi. Should I connect another wire from 0V on pcb to starground???

Henrik

 

[Harpo]

I am sorry for not understanding this but isn´t 0V connected via the "gnd" on the input-connection on the pcb?

yes

My input xlr´s pin 1 is connected to "gnd" on the input-connection on pcb and also to starground on chassi. Should I connect another wire from 0V on pcb to starground???

If so, no other connection required. From your 1st pic, input XLR pin1 looks like to only have the brown wire attached exclusivly and this would be missing a connection. Maybe optical artifact.

 

[Bonke]

Ok! That would be the photo fooling you.
Cool, thanks for struggeling with me Harpo!

Henrik

 

[lumpylipton]

Hi,
I finally completed my G9, it powered up fine (no smoke!!) passed audio on both channels and other than one switch contact I somehow missed soldering, everything seemed ok......until....now.

The phantom power was originally trimmed to 48v and was working, however now I'm getting about 22V for phantom and the trimmer does nothing.
No parts are obviously smoked, and because it was working, I'm quite sure all the components are correct.

I'm thinking it must be one or more of the tripler caps, since I'm just not getting anywhere near the voltages expected.  Would this be a good place to start?  I've double-checked the AC voltage getting to the tripler is 16VAC, so it's not the transformer.
Thanks, this thing sounds fantastic, I'm excited to try it with condensers once I get this phantom sorted.
Warren

 

[gyraf]

..double-check that the phantom power is not loaded down by a shortcircuit somewhere, doublecheck orientation of electrolytics(!!).

Maybe first try disconnecting P48-stage from rest of G9 for troubleshooting (maybe cut a trace and resolder later).

If it worked initially, and not later, my guess is a electrolytic in the tripler section, try replacing (maybe use higher rated voltage types)

Jakob E.

 

[chrispbass]

Has anyone tried the Haufe ST8456 sold by silent arts on the input yet?

 

[sam system-d]

I'm new here, so please, excuse those words :
THANK YOU!
I'll do a real post as soon as I will finish my GIX (very few more stuff to do)
Great project, great sound, I think I'm in love with it
I've got to fix something (gain pos #5 doesn't work on both channels) but everything else is ok.
The only negative thing I got to say about it is once you've build one, you just want another

 

[lumpylipton]

Thanks Jacob, I fixed my problem, it was one bad cap in the tripler.  I replaced all of them with the next voltage up just to be sure.  Now the phantom does work.  Next problem; I now have a rather loud 60Hz hum that is only present when the phantom is on, both channels.  I'm going to search through the forum to see if I can find something on this.  Obviously a grounding issue somewhere....

Many thanks for the project, it sounds great and I learned a lot building it.

Warren

 

[haima]

Are you sure it's 60Hz?

Or might be 120Hz + harmonics?

Perhaps the phantom supply might have heaps of ripple - that could be heard as "hum" on the output - does it hum in the 48v setting if you just terminate the input without any Mic attached? (i.e. put a 150ohm (or anything between 50 and 1k) resistor between pins 2+3 on the input XLR).

 

[lumpylipton]

It's definitely 60 Hz, I measured it with my DAW.  I tried terminating with a resistor instead of a mic, and the hum is far louder that way.

Any other ideas?  I've rechecked the grounding, and it is XLR inputs pin 1 tied together, XLR input one pin 1 tied to star ground, IEC ground tied to star ground, which is then bolted to the chassis, nothing else is tied to the star ground.

Moving the transformer or power switch wiring around does nothing, just a steady 60Hz hum, only with phantom on, otherwise it's silent.
Thx,
Warren

 

[Cardinen]

Hi,
I finally finished my G9, seem to work fine but i have a few question about.

1- One of the toroidal transformer (12+12V 50VA) make a bit of noise, even when the case is closed. Is that normal ??
(It scared me at first !!)

2- Switching between Line/Mic don't work on channel 1. I've checked the connections from the switch to relay and all is fine. 12V goes to relay but it seem to don't work. is a standard Omron G5V2. maybe is faulty ?? what could try before desoldering it ??

3- I have a bit of noise at high settings using the Direct In whit my guitar/bass while the mic ins are really quite.
the noise appear at step 7 and rise. i think this is normal, can you confirm ??

Thx

Cardinen

 

[sam system-d]

Hi Cardinen,
1 - I got no idea, sorry, I'm a newbie in electronics
2 - I would check the 1N4148, I used to do a project with lot of them and relays, and few of them didn't work for no reason, so the relay didn't switch.
3 - you can avoid this problem with a shield cable from input transfo to jack, jack to Input cap. There's a topic about this, search on the meta Once you've done it, the G9 is really quiet.

 

[tmuikku]

3 - you can avoid this problem with a shield cable from input transfo to jack, jack to Input cap. There's a topic about this, search on the meta Once you've done it, the G9 is really quiet.

Not until HT supply is done out of the board Check this thread a few pages back, there is plenty of info including pics and FFT charts before and after.

 

[Matador]

Moving the transformer or power switch wiring around does nothing, just a steady 60Hz hum, only with phantom on, otherwise it's silent.

How closely matched are the 6.81K phantom coupling resistors?