The official G9 help thread

The 2 DI inputs don't work.
yes, the rotary was switched to line when i tested it.

I could be wrong but are those jacks switching jacks? Since the mic inputs are working: it seems like the jacks just aren't disconnecting the mic input if you plug in a jack connector to the DI input. I don't think there is really much that could be wrong.


Even if they are switching jacks it could be that it has just been wired wrong. The wires that should go to "from" and "to" may have been reversed.

Basically the switching jack should just be stopping signal coming from the mic/ line input. This obviously isn't happening. Or maybe it is, plug a line level signal into the line input, hook up th output from the G( so you can monitor the sound. Does the sound from the G9 disappear if you insert a lead into the DI input?

Here's a suggestion: with the unit off(and left for awhile to discharge) open it up and insert a lead into the DI input. Have a look at the DI connector. Part of the metal strip that the guitar lead connects to should be lifting up. Does this happen? which side of the metal strip on the DI jack does the wire from the "from" connection on the PCB go to? is it the longer part of the strip that lifts up when you insert a guitar lead into the DI jack?

Do you have a multimeter?

Rob

Like Rob said-first test.  Plug in a jack and retest mic input.  Does mic input work now?

Sorry, as Mbira made clear, it wouldn't actually be necessary to use a line signal. Just hook up a mic, making sure you can monitor the signal. Tap it or talk into it, then insert a jack into the DI input. does the sound the mic is picking up disappear?

Rob

Yes the mic input is ok...
and when i insert a jack, the signal doesn't disappear
I tried to reverse the To and From but it's the same

It may not be a switching jack then. If you have a multimeter: plug a lead into the DI, then check for continuity between "to" and "from".

Judging by your pictures, one of the channels doesn't have a DI attached at the moment. Is this the one you are working on? However what I'm thinking of may not matter seeing as you said both DI's aren't working.

I have one really stupid suggestion which I'm sorry for making: It looks like you're using TRS sockets as opposed to TS. It's fine because of the way you wired them: but make sure that the guitar lead is fully in. If it isn't inserted properly it won't cut off the connection from the mic input. (Sorry, it's an obvious one but could potentially be the cause of the problem)

Rob

So,
yes the second channel is not attached and i'm trying the first one.
and yes it's a TRS jack... then, it could be the problem !!!
i'm in Marrakech until thursday, I check back at home
i hope it's that !

thank you for your assistance & sorry for my english ...

Yes, as stated, if the jacks are actually hooked up correctly, when you physically put in a guitar cable, it should cut out the signal from the mic input.  You can safely assume that the jacks are either the wrong type or hooked up wrong.

Hi,
i came back !!!
I just soldered a TS switching jack and the problem is the same :
The signal from the mic input is not cutted when i insert a guitar cable in the DI
And no signal in the DI position
!!!

Well you'll need to use a multimeter to check for continuity along the line from the input transformer to the jack. It's possible that whoever built the unit decided to eliminate the connections to the DI to prevent oscillation at high gains.

It's a simple enough problem and will be easy enough to find.

Didierterrific said:

And no signal in the DI position

Click to expand...

What exactly do you mean by this? ( I realise you aren't a native english speaker but please explain it as best you can). Do you mean that you just aren't getting input from a DI'd instrument? As the G9 doesn't technically have a DI "position" as there isn't a switch you turn to activate the DI (like you do for the line, Mic and +48).

Were the DI jacks wired up when you got the unit?

Rob

from your G9-Did-3-.jpg, exchanging the blue with the white wire at the tip of your TRS-plug (or at the from/to inst.jack spot at the pcb) might do the trick.

I have already tried to invert the white wire and the blue wire, it's the same.

when i bought the G9 there were not Jack inputs...
i soldered wires with TS switching jack on channel 1, but with a guitar cable insert in the jack input (the one i have soldered) and the rotary in line position. i have no signal.

i go to try to check for continuity along the line from the input transformer to the jack. I really don't know how to make that, but i'm gonna try.

Since there were no jacks on it when you bought it, it would lead me to believe that whoever built it disconnected the wires or PCB traces,to prevent oscillation at high gains.

You could visually inspect the unit. But be extremely careful. Since you don't have a meter you won't know if the unit is fully discharged or not.Leave it plugged in, but turned off for 20 minutes or more. The G9 discharges quite fast but seeing as you don't have a meter you will want to give it a lot of time.

Then plug the unit out from your AC wall source.

You'll need to disconnect all the wires from the board that can be disconnected (no des-soldering required). Remove the tubes and screw that hold the PCB down. Lift the PCB to check if any of the traces from the input transformers, or others around that point, have been cut. Also see if there any additional wires on the underside of the PCB, that are bridging certain traces.

Obviously a multimeter might make this easier and would allow you to track down the problem faster. But it may be possible to solve the problem without one.

Rob

You know guys, we are talking about 245+ volts of DC.  Didleteriffic doesn't even have a multimeter, so I STRONGLY RECOMMEND that he just get someone with a little experience to take a look at the unit.  The G9 is a hard first build, and troubleshooting is always harder than building.  It should take a tech les than one hour to fix the unit.  THat is my recommendation.  Didlerterrific, this isn't meant as an insult or anything like that, just that inn\f you're into DIY, probably the best thing would be to start with somethingthat can't kill you easily.  Maybe you can evel look over the shoulder of the tech and learn what was wrong at the same time!

Good luck!
Joel

Don't worry !!!
i have got a multimeter. I know how to solder.I have build and wired my studio.
I am not electronics engineer. i'm a newbie in DIY but I have already modified small equipments as microphones or pedales.
I think have understood how to check the PCB.
tomorrow i 'll try to trace the signal and i'll inform you.
Thank you for your advices and your patience.

Yeah I was a bit hesitant to suggest a visual inspection unless you have experience.There's no need for pride on this forum: we're all here to learn and share! The most important thing is to just be safe.

Be extremely careful when doin anything inside the unit. As Mbira said the G9 as a very high B+.

Just use your meter very carefully (with your unit switched off, no need for it to be on with what you need to check). Do you know how to check if the G9 is discharged? It's an important one to know, and best to learn it early on.

Good luck with finding the problem. And be safe! The G9 sounds awesome (thanks again Jakob!) you'll love this unit.

Rob

I borrowed a friend's G9 to try it out.  Sounded great, very musical. 

But for acoustic music, I had to turn both channels and their output to full gain the whole time using an AKG 414 and a tube mic on a bashing acoustic guitar.  This seemed like very low gain for a relatively loud acoustic instrument and two hot microphones.

I'm interested in building one, but I'm concerned about the lack of gain.  It would never work with a ribbon mic on an acoustic source, for example. 

How much gain does the G9 officially have?  Is there a way to increase it?

thanks.

Officially, there's some 60dB available - which should cover most situations..?

I use a 414 here and I'd never need to crank it up all the way to get the gain needed for an acoustic.  There must be something wrong on that build...

To Ram and Mbira
Yes some traces have been cut and there are any additional wires on the underside of the PCB,  certain traces are bridging.

Here is a very bad photo of the pcb... it's a picture from my phone !

i found a mod on the Gyraf audio G9 page... i understood the problem.
I must remove the bridges of traces and running a length of shielded cable directly to/from the jack as explain in the mod.

can you confirm this?

thank you