The official G9 help thread
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Help Support GroupDIY Audio Forum:
JingleDjango
Well-known member
Deepdark
Well-known member
Congrats. Do my BOM worked, finally?
JingleDjango
Well-known member
Your BOM was very helpful, but a little incomplete in minor ways.
There were some mismatched Molex connectors, like 5p terminals and 6p headers, 3p terminals but no headers. I should have checked these myself. I assume you were shopping based on what you were missing, possibly including other projects. So I ended up substituting some no name connectors from an electronics shop nearby. You don't understand the relative quality of Molex products until you compare them to the alternatives. I will need to stock up on a variety of Molex connectors of differing pin counts for future builds. They are worth the price.
There were 2 caps missing from my Mouser order. I don't have the unit in front of me anymore so I forget exactly which. They were the two 10uf caps directly above the 10p control connections. It's possible you had them in your BOM and I mistakenly deleted them when I merged your order with the one I had already started.
I substituted most of the resistors you chose with 1/4W ones.
There were some mismatched Molex connectors, like 5p terminals and 6p headers, 3p terminals but no headers. I should have checked these myself. I assume you were shopping based on what you were missing, possibly including other projects. So I ended up substituting some no name connectors from an electronics shop nearby. You don't understand the relative quality of Molex products until you compare them to the alternatives. I will need to stock up on a variety of Molex connectors of differing pin counts for future builds. They are worth the price.
There were 2 caps missing from my Mouser order. I don't have the unit in front of me anymore so I forget exactly which. They were the two 10uf caps directly above the 10p control connections. It's possible you had them in your BOM and I mistakenly deleted them when I merged your order with the one I had already started.
I substituted most of the resistors you chose with 1/4W ones.
Deepdark
Well-known member
good to know, I'll make a checkup soon and correct it 
Glad to hear yours work well, too. I think the principal problems have been covered through the thread and solution has been proven to work too.
Glad to hear yours work well, too. I think the principal problems have been covered through the thread and solution has been proven to work too.
JingleDjango
Well-known member
When it comes to mounting the G9 in a rack, can I fit it snug against other devices or do I need to leave room for ventilation? If so, how much? 1u? .5u?
No extra ventilation should be needed - we dissipate some 25-30W at max.
Jakob E.
Jakob E.
JingleDjango
Well-known member
Thank you.
Deepdark
Well-known member
Quick one. I tried the di on both track and it hum like hell, only when i plug in it a cable, once pulled out, the hum goes back to it's normal level. If the gnd exit is at the input xlr, and that pluging a jack into the di bypass the input transformer, then is it possible that the gnd is unconnected when jack is inserted? I used an solated jack, and checked for continuity between the hex nut on the chassis and gnd and it doesn't conduct until i plug a cable in it, then the nut conduct with gnd, probably normal, thought. Other than that, i used shielded cable and the bare wire is connected to the sleeve. It is connected at the gnd at the other extremity (i did the di mod). It's the same on both. Any idea?
Deepdark said:
Check that your jack input ground actually connects to G9 ground when you insert it.
If not, check your continuities.
And it's best to check hum with a shorted jack, as the inst-input is very-high impedance and WILL hum with an open input.
Jakob E.
Deepdark
Well-known member
I checked continuity gnd is ok when i connect a 1/4 jack ito it. I thought maybe i had solder the gnd to the switching side of the jack but no, i installed it the good side. One thing, on the 5 pins header, i connect all 5 wires, but 2 of them are the "to and from jack" so i wonder, maybe these 2 wires act as an antenna, being floating. When you said to check the hum with a shorted jack, what do mean exactly?
Deepdark
Well-known member
Are you saying that i should short the input with what, à load between pin 2 and 3 when using thé di, so thé input isn't left open. Right?
Deepdark
Well-known member
gyraf said:
Not sure to fpllow. By shorting jack, you mean the xlr input that should be shorted when testing noise? Or i should insert a shorted xlr plug when testing/using the instrument input, so the input isn't let open when the instrument jack is used? Or you mean anything else? When onserting à guitar, i tested the ground of the jack with the main bolt star ground and ir has continuity, but i tested without shorted input xlr.
Deepdark
Well-known member
forgot to mention that teh jack hum even with a guitar plug in it. Also, the level is low. Maybe I just reverse the To and From so when I insert a jack in it, the signal go to the transformer secondary instead of C2??
Deepdark
Well-known member
Turned out it was the to and from I had reversed. Now I got plenty of signal with the DI. The only thing left to check is the hum. I got some hum. I have a steady 60hz that won't diminish when I rotate the main transformers. And with gain at full, 120 and 240 harmonics. This ones get amplified when turning gain pots. I can live easily with the 60hz, since it is quiet low, but the harmonics are a little more painful. Since they got amplified when turning gain, means they must find their way to the tubes, or to the input transformer I guess. Any ideas other than that? Ground scheme is quiet simple: The main board exit at xlr 1 pin 1, then all xlr's pin 1 are taken together and go to the main bolt, as well as the iec ground.
Deepdark said:
Did you see this errata?
08. Jan. 2007: If you run into problems with oscillation on the highest gain settings, try running the connections to/from the front panel High-Z jack connector "directly" from the relevant points on the PCB - by cutting the PCB traces, and running a length of shielded cable directly to/from the jack. See this image for reference!!
http://www.gyraf.dk/gy_pd/g9/G9-EDIT.GIF
Gustav
Deepdark
Well-known member
Gustav said:
I do. No oscillation trouble here. Only 120 and 240hz harmonics on both channel. These harmonics get amplified when turning gain pot (worse at 3/4 turn and more)
Deepdark
Well-known member
Gustav said:
When listening to noise, i used a dummy source (200r) but i didn't short the jack.
Deepdark
Well-known member
I should also add the following:
- 78S12 is mounted on the chassis, nearest possible from the main board. It's insulated from the chassis with 2 layers of thermal foil and a grommet on the screw.
- Each pair of wire on the psu is tightly twist (I used my drill to do so)
- My power transformer are rated 50VA each, run not even warm. The dual 15V transformer feeds the 12V one, as on the schematic
- There is a 60hz hum, constant, quiet low, thought. And when boosting gain and output, it's like the harmonics get amplified (120 and 240hz)
- Instrument Jack mod done with shielded cable.
- Tested hum with a dummy source (200r shorted xlr plug), but instrument jack wasn't shorted
- C14 and C15 are 470uf
- HT is on the main board
- Input xlr cable is shielded. Output isn't but tightly twist pair of wire.
- Ground exit from the main board at the xlr1 ground connection, go to pin 1, take all pin 1 of all xlr and then to the main bolt
- OEP input transformer with shielded can (I tested the can and it has continuity with main bolt ground reference)
- Output transformer is Edcor. Wired with tightly twist pair or wires, installed on the opposite side of the chassis than the main transformer. I shoudl lift them with aluminium standoff, though and wire the output transformer with shielded cables
- Ground jumper are all there.
- Same on both channel, but channel 2 (nearest the transformers) is a little bit noisier
Any suggestions?
- 78S12 is mounted on the chassis, nearest possible from the main board. It's insulated from the chassis with 2 layers of thermal foil and a grommet on the screw.
- Each pair of wire on the psu is tightly twist (I used my drill to do so)
- My power transformer are rated 50VA each, run not even warm. The dual 15V transformer feeds the 12V one, as on the schematic
- There is a 60hz hum, constant, quiet low, thought. And when boosting gain and output, it's like the harmonics get amplified (120 and 240hz)
- Instrument Jack mod done with shielded cable.
- Tested hum with a dummy source (200r shorted xlr plug), but instrument jack wasn't shorted
- C14 and C15 are 470uf
- HT is on the main board
- Input xlr cable is shielded. Output isn't but tightly twist pair of wire.
- Ground exit from the main board at the xlr1 ground connection, go to pin 1, take all pin 1 of all xlr and then to the main bolt
- OEP input transformer with shielded can (I tested the can and it has continuity with main bolt ground reference)
- Output transformer is Edcor. Wired with tightly twist pair or wires, installed on the opposite side of the chassis than the main transformer. I shoudl lift them with aluminium standoff, though and wire the output transformer with shielded cables
- Ground jumper are all there.
- Same on both channel, but channel 2 (nearest the transformers) is a little bit noisier
Any suggestions?
