The official G9 help thread

[Jamie1234]

Thanks for the help Jacob, I will do some tests tonight and get back to you with some more useful information

 

[Deepdark]

Hey guys, couple of thing I would like to clarify:

- C03/103 is labeled 220n but it should be 470n. Is it alright? I check it on the schematic and it is supposed to be 470n. Just to be sure
- I didn't find R38, is it possible that there is no R38 (100r)?
- I saw on a couple of BOM that all the 4001 (D2, D8-D16) are replace by 4007. Is it ok to put 4007?
- What is the rating for the 78S12 heatsink? I found this one and I would like to know if it's ok? http://www.digikey.ca/product-detail/en/V5224C/AE10826-ND/3511429?itemSeq=142678372&uq=635253790339606984
- For the P01/101, is it ok with those 47K log pot? http://www.digikey.ca/product-detail/en/1624161-2/A105791-ND/2363637

 

[Jamie1234]

Yet another slow reply, sorry I don't have as much time to play with this stuff as I'd like 
I've got round to doing some tests to try and find the cause of my noisy crackle. Here's some info, if anyone has any bright ideas they would be much appreciated

I have a loud crackle on channel 1 (furthest from the transformers)
- it is still present when the input gain is turned down to 0, but gets louder as it is turned up.
- it changes volume with output level, and is not present when output is turned to 0
- it is always present (when using mic, line or DI)

Ht is measuring at 246

 

[kvark]

Finished my G9 and just wanted to thank Jakob for this great project. Sounds really, really great!!
Lundahl in/out transformers and Tung-Sol NOS 12au7.
I did the DI-trace-cut-mod which fixed the oscillation problems. The 100Hz (+ multiples) rippel got away when I moved the 12V and 245V to the "spare-psu". No sign of noise or hum of any kind.
I can really recommend to do these "mods" direct.
Next project will be G7 for sure.

 

[Deepdark]

Nice build. What brand are the 2 big blue caps? Atom? They look like the one I put in my LA2A

 

[kvark]

Correct! Sprague Atom from Banzai in Germany.

 

[Deepdark]

Really like the handgraved panel. Can you upload more pics? Eyes pleasur

 

[kvark]

Thanks!
I stole (borrowed?) the idea with the red chickenknobs for these guys:
http://www.vintageaudiorentals.com/de/artikel/vintageaudio-179.html

It's a great fun project but I think the PCB need some changes.
- Add the "trace-cut" modification and add connector holes for this
- Extend the PCB and move the 12V and 245V psu to an isolated area at the right side
- Add increased mounting holes for C25 (too small for my Atom Caps)
- Add some more holes for the large poly caps
- Move the output connector for the second channel. It's very tight.
- "Convert" the layout to doublesided though hole plate by adding "pads" to a second layer
- Add a couple of more non-plated tooling holes to stabilize the board around the tubes

I'm working in a PCB factory so I made the PCB's for free from the gerbers on the Gyraf site. I made some minor changes to the files in the solder mask and fixed a couple of isolations to get it to work with thicker copper without risking to get shortcuts in manufacturing or when soldering. If I should build a second unit I would to these changes in the gerber files. Not very hard if you have good CAM tools. Maybe Gyraf/Jakob would be interested to update the gerbers on their website? I can do the work.

I also think that the PCB thickness should be 2mm or 2.4mm. That would make the PCB more stiff and prevent the board to get bent when changing tubes. At least my tubes were really hard to fit into the sockets and too much bending and tension to the board might cause a crack in a solder joint.

 

[kvark]

Hey guys, couple of thing I would like to clarify:

- C03/103 is labeled 220n but it should be 470n. Is it alright? I check it on the schematic and it is supposed to be 470n. Just to be sure
- I didn't find R38, is it possible that there is no R38 (100r)?
- I saw on a couple of BOM that all the 4001 (D2, D8-D16) are replace by 4007. Is it ok to put 4007?
- What is the rating for the 78S12 heatsink? I found this one and I would like to know if it's ok? http://www.digikey.ca/product-detail/en/V5224C/AE10826-ND/3511429?itemSeq=142678372&uq=635253790339606984
- For the P01/101, is it ok with those 47K log pot? http://www.digikey.ca/product-detail/en/1624161-2/A105791-ND/2363637

1. I used 470uF and it worked good. (WIMA 505-MKS4.47/250/10)
2. R38 is not used
3. Use 4007 but consider doing the 12V and 245V psu on an external PCB. If you have the "spare psu" it's prepaired for two diod bridges. I had some laying around I think it was these 625-W04G-E4 (mouser p/n)
4. The heatsink looks ok but the bigger, the better.. Don't forget to add insulation
5. Should work I guess. I used Bourns 50k log pot in conductive plastic. Leftovers from another project. I love the smoothness in these pots. Think it was this one 652-91A1A-B28-D18L  (mouser p/n)

 

[kvark]

Hi everybody !

I'm back with my G9 and I need your help 

I'm trying to find the source of a 100Hz noise on the outputs. Even with the outputs levels at 0dB, the noise is present. Everything is correctly grounded (if I unplug ground wires, a 50Hz noise appears when I turn on outputs levels). I tried with power transformers and caps out of the case but the noise still the same :/

Do you have an idea ?

I had the same problem. Moved the 12V and 245V to the spare psu. Now my unit is dead quite.
I first changed C14 and C15 from 100uF (50+50) to 220uF and it help a bit but not very much.

 

[Deepdark]

Hey thanks Kvark

Yes I build the psu on the spare psb. Thanks to answering my questions I had a hard time, too, trying to insert my atom caps in the holes so I purchased two new caps but rated 250V instead of 450V. The molex connectors was hard to insert in the holes, too. But overall, it's a damned great project

 

[ding]

- Add the "trace-cut" modification and add connector holes for this
- Extend the PCB and move the 12V and 245V psu to an isolated area at the right side
- Add increased mounting holes for C25 (too small for my Atom Caps)
- Add some more holes for the large poly caps
- Move the output connector for the second channel. It's very tight.
- Add a couple of more non-plated tooling holes to stabilize the board around the tubes

I made some minor changes to the files in the solder mask and fixed a couple of isolations to get it to work with thicker copper without risking to get shortcuts in manufacturing or when soldering. If I should build a second unit I would to these changes in the gerber files. Not very hard if you have good CAM tools. Maybe Gyraf/Jakob would be interested to update the gerbers on their website?

This would be interesting! I think the double sided aspect would just make it that much more difficult for people that print at home. If you have already done the work and Jakob is ok with it I say post those babies here. I wouldn't mind trying my hand at self etching it. 

 

[baol]

Hi guys
is it possible to use 50k audio pot instead of unavailable 47K?
do they make a worse work?
thank you

Andrea

 

[Harpo]

is it possible to use 50k audio pot instead of unavailable 47K?

Marginal real world difference (HPF-3dB point might drop from 338Hz to 318Hz or 154Hz to 144Hz with doubtfully perfect caps and spot on 47K vs. 50K pot values). Pots for usual come with +/-20% parts tolerances, lower pot tolerances (FI +/-10%) on request for some extra bucks.

 

[Rigpa]

I have built 2 G9 and both units are a little too noisy. I can live with the noise level when recording vocals for songs but if it is speak only I very much need to use a noisegate as it becomes very audible. The noise is broadspectered also including lo freq. hum. I tried moving the power transformer and also tried bigger caps but no difference.

I cut the cable to the Instrument input and changed some of the cables to the controlboard to shielded cables, and that helped some.

The channel closest to the PSU-transformer is the worst in both units. The board is mounted as far away from the tranny as the case allows.

My original plan was: A mike -> G9 -> G1176 -> FF800 but this became too noisy so now I leave the G1176 out of the chain.

If anybody has an idea what to try next I would be very happy

 

[gyraf]

For broadband noise, try different tubes. For hum, grounding, shielding, and power transformer placement.

Jakob E.

 

[baol]

Hi, is there a particular way  to mount the lorlins? well no problems with the gain 'cause they have only one center leed but what about the others?
thank you

andrea

 

[havier3]

Hello Everyone.
I have the problem with my "almost finished" G9 - my problem is:

Line inputs works, but when I want to change the input on XLR and 48v - nothing happens - microphone doesn work. I wonder if I have maybe a problem with the SW1 pot. I see on the layout that this pot has different posisions than the rest pots - I mean the middle spot - A B C D positions. On the SW 3 and SW4 this middle legs are: A (down left) D (down right) B (up left) C (up right) and on SW1 i see: A (down right), B (down left) C (up left) D (up right). BUT on a users photos I see that all the Swithes has the same posisions ( different than on the layout).
Can You help me with it? What positions is correct? If this can causing my XLR Input problem?
Can You help me please?
Thank You
Maciek

 

[havier3]

I have another question about Input selection switch.

so:

When switch is in it's first position I have connection between A and 1, and C and 7

When switch is in second position there is connection between A and 2, and C and 8

And finally with switch in it's third position I have connections between A and 3, and C and 9.

Is that ok?

I understand first and third position, when there is connection, but I don't see the point in second position where no connection is made. (maybe thats just the way it is  :grin:  :?:

I think I see this as a problem too.  Using a 2x6 lorlin, you don't get the right combination of switching.

Hello - I am still searching..
Is this positions of SW1 is really correct?

 

[gyraf]

Is this positions of SW1 is really correct?

Yes.

As you can see, the switch is symmetric - so either way you put it in, it will work PROVIDING that the center connections A, C are connected to the tracks, not 90degrees rotated so they connect to empty/unconnected pads.

If in doubt, check with schematic and ohm-meter on the switch.

Jakob E.