The official G9 help thread

  Hi gregcs1

  Sorry for the confusion, I was trying to figure out the wiring myself, copied someone else s  diagram and and modified it cus I couldn't wrap my head around the 15v and 12v thing  , not realizing that the 12v was only for the HT the other way round.  :

  I,m not sure how or if I can remove it from this post as to not confuse anyone else, but I will try.

 

There is no need to remove pics. They're very helpfull. Just twist the wires of one secundar on T2. Then it will be ok.

OK. I had a little of spare time, and connected my Sansa Clip (actually is wife's  ) and played some music through both channels. It plays like heaven (even on my Truth B2031A  : ). The only thing that bothers me, is some kind of electric hum (buzz), which is present all of the time. It is quite noticable/disturbing when nothing plays. Changing gain and output levels is effectless on volume of this buzz (ok, on last three highest gain positions and output level crancked to max, new buzz/hum/hiss appears - is that normal?) But that electric buzz stays the same. It stops only when i disconnect G9 (so it's not behringer fault) I moved everything that is movable (trafos, in/out wires...) but buzzing remains and it doesn't change a bit, when i'm moving things around. The only thing i can't move are HT reservoir caps, and IC2 (which is mounted on heatsink on the back plate and connected with 2inch long wires - could that be a problem?).

I figured out, this might be some sort of a ground problem. I connected both direct ins, and mic on channel two. With no signal,  and gain&out on max settings, there is buzz on both channels, which is quieter if i touch the case or mic. Any thoughts?

pics for help:

http://picasaweb.google.si/lh/photo/5vxOHB9wRp1IEMCENcZZ1A?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/ZWPJeMwGupKx2hxE7NsVRQ?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/NMKhVn_kuoVClGSK4iwDYw?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/tv_37CLJby3xZqOXWIc5pQ?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/XHCQpJAi7aDZCn7g3bI90g?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/e0mm1FJRt-5tc9KXtWQGaQ?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/gQbIutg0L_oaG20xvLYeog?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/p0gCA9DkZ3XNYyIyatXJZQ?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

gregcs1 said:

I figured out, this might be some sort of a ground problem.

Click to expand...

Double check to make sure you followed the recommended grounding scheme.

BTW, I would put some heatshrink tubing on the legs of the regulator attached to the large heatsink on the back panel.  While I understand that the camera angle might be exaggerating how close they are to the heatsink, it might be good to have them insulated just in case you bump into them while probing around.

Cheers,
--
Don

It looks like you have all your XLR grounds connected. My understanding is only pin one to board input of first channel is connected by it's grounding tag, then through case to fixed ground connection. See page 29. That's what Ive done and it's quiet. Let me know if I'm wrong.

idylldon said:

BTW, I would put some heatshrink tubing on the legs of the regulator...

Click to expand...

Angle is really exaggerated, and legs are even bent away from the heatsink, so bythemself they can never touch it. But just in case, I will heatshrinked them. You never know... 

sethyrish said:

It looks like you have all your XLR grounds connected. My understanding is only pin one to board input of first channel is connected by it's grounding tag...

Click to expand...

I'll try that as soon as i get home from work. Should I scrape the paint away at the place where ground is attached?

After reading all the positive stories about this pre-amp I decided to start building one. There is one thing though. I have two jensen transformers that I have spare from another project.

Output Trafo:
JT-10k61-1M
http://www.jensen-transformers.com/datashts/10k611m.pdf

Input Trafo:
JT-115K-E
http://www.jensen-transformers.com/datashts/115ke.pdf

Can these be used in this design? I know they won't fit the PCB, but thats not a problem since I am designing a new PCB myself.

I finally finished my G9. I’m so pleased with my new found hobby that I went out and bought a new Hakko soldering station to celebrate its completion…..damn.  So thanks Jakob and Gustav and everyone else on this forum that made it possible for someone with limited experience to put something like this together. I’m sure people can see some of their own handy work such as audiofreaks recycled CPU heat sink and matta’s single toroid adaption so thanks for the input and great photos. The last thing I did before firing it up was to remove the solid core lightning bolt earthing system I had arranged. After reading the posts by fucanay and PRR.  Hopefully I’ve added something to the forum with some basic info on etching your own face plates.
http://www.groupdiy.com/index.php?topic=33056.0

WOW! Very neat! Congratulations.

Back to my problems with hum. Done some more testing with ground connections (btw - idylldon, i fixed that regulator legs isolation). I removed ground connections from all xlr's because this removed hi-gain hum. I tryed all variations of connecting ground, but sound is much clearer without ground. However, that electric buzz remain. Then i connected G9 to my Motu 828 mkII, and buzz disappeared! Now explain that!

gregcs1 said:

WOW! Very neat! Congratulations.(btw - idylldon, i fixed that regulator legs isolation).

Click to expand...

Excellent!  I've learned this lesson the hard way.  ;D

I removed ground connections from all xlr's because this removed hi-gain hum. I tryed all variations of connecting ground, but sound is much clearer without ground. However, that electric buzz remain. Then i connected G9 to my Motu 828 mkII, and buzz disappeared! Now explain that!

Click to expand...

Have you followed the exact grounding instructions mentioned earlier in this thread?  Also, you mentioned:

Should I scrape the paint away at the place where ground is attached?

Click to expand...

I see your grounding point is a long machine screw that also holds your caps in place, right?  Is this screw making a good connection to the case; that is, have you scraped the paint under the head of this screw?  You've checked continuity on all your ground with an ohmmeter?  

Cheers,
--
Don

Have you tried this yet? Also, I think I read if the leads to 78S12 are to long it can cause problems. Other than that I'm not sure.

In regards to the Jensen JT-115-KE, it should work, but looking at the schematic I'd add ~150K 1/4w resistor from the ground rail to the top side of the secondary to provide proper loading for it. Should sound great and I am planning on trying these instead of the Lundahl's I have in mine.

For Line out, go ahead and try the JT-10K-61-1M. Increase C13, maybe to 20-30uF. Please let me know if you do these, if it sounds wonderful I will try them too. I like my Lundahls but want a little more color. I am also going to get some Mullards...

With my G9 I grounded all of the pin ones as soon as possible. Straight to the chassis with wires about 2-5 cm or a little more and it's extremely quiet. If you haven't already tried it: try turning the toroid to remove some of the hum.

Rob

One of the hums disappeard when I removed ground from inputs/outputs. There is still that brum when it's working in standalone mode (out to monitors) which totally disappear when G9 is connected to Motu 828mkII, and one barely noticable buzz on channel two, related to longer direct in cable, which runs too close to psu part. I will fix that in future (problem is only on highest gain&volume). As said, buzz is there only in standalone mode, recordings are clear as they should be. Could go something wrong if there is no ground on input?

btw... observation on brum: when i turn the unit on, it's silent, then (about 10s) it gets louder (but not disturbing in any way)

.. sethyrish..  WOW..

  That's one beautiful G9 !  That face plate is absolutely stunning, clean work, you should be very proud.  Thanks for the shout-out on the CPU heat sink, so happy to have inspired someone, as I have been inspired by so many in this forum.

... after finishing such a great piece of gear..... watchya gonna build next !!! 

 

sethyrish said:

Have you tried this yet? Also, I think I read if the leads to 78S12 are to long it can cause problems. Other than that I'm not sure.

Click to expand...

Other than the fact the the color coding for the wires is wrong in that drawing, yes, that is how I grounded mine. I also did the oscillation mod for the DI jack before I fired it up. This thing is dead quiet. The leads from my 78S12 isn't short either probably 5 inches to reach the head sink that is mounted to the rear panel.

Matt

Thank's audiophreak. I've almost got all the stuff for mnats ver A 1176. How about you?

I have a thoroughly busted in Mnats Rev A. And is top Class! But this is the G9 forum. I heard the CD after I sent it for mastering and the drummer is freaking out. I used the G9 for overheads. No samples of that not even on my site...

    sethyrish .... I have been working on a pair of G7's for about 10 months now, it slowed down because I had to out source some  tasks ('cus I just dont posses thoughs skills ) so started  a pair of GSSL's, and about 1/2 way into another G9 with the ecc88 output stage and different output Trans. - yeah......I fell hard in to DIY  ;D

  Stagefright13 ... if you don't mind sharing.... what mics were used as the overheads?