The official G9 help thread

yes. pcb marking glitch, sorry.

Jakob E.

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: :?:

Just curious. Could one use the Lundajl 1530 as an input? 1:7 would give even a little more gain than the OEP 1:6.45.

I would much rather use Lundahls for the high bandwidth. But also want the little bit of added gain from the OEP. I'm torn between which one to go with.

Maybe OEP input and Lundahl output?

Daniel

How about one channel Lundahl and one OEP?

[quote author="gregcs1"]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: :?:[/quote]

Yes, it's ok. Just take a look at the schematic.
First position switches 48v on (mic in + 48v), second position (no conection) switches the 48v off (still mic in.), third position switches to line input with a relay.
Really, when I first saw your question with the pic and all I was wondering my self how this was suppose to work but a look at the schematic made it clear....

Nice. Thanx

So my thaugts were right!

Does anybody know how to check if gain switch is switching or none switching? (switch is already soldered)

[quote author="gregcs1"]How about one channel Lundahl and one OEP?[/quote]

That wouldn't work for me as I do stereo location recording and having a stereo pair of mics running through mis-matched preamp wouldn't sound too good. :thumb:

Daniel

I would like to try different mic input transformers on my G9, does anyone know the impeadance this circuit wants to see on the load side? Most tube mic pre's want to see a pretty high impeadance, and get the gain as well, but this one seems different. What are the impeadances of the OEP's? I only see them listed as ratios....

From sheet:

Source Impedance: 150/600ohms
Optimum Load Impendance: 6.25k/25kohms

[quote author="ChrioN"]
Jacob do you remember what you said? hmm...something about checking the input wiring and see if signal reaches the instrument jumper or something.[/quote]

The signal doesn't reach the instrument jumper. I read 0v AC jumper->ground.

Then trace the circuit - referring to the schematic - to that point....

Jakob E.

Okey, thanks. Im still learning.

I feed the preamp with a 1.76vac signal, and I get 0.4vac after C2. Is this good or bad?

Also, it appears as I have 0.43vac on the input xlrs (pin 2 & 3 to ground) with nothing connected.

So as the schematic shows the input transformer coils wired in series, then the input is set up as 600 to 25K...whay 600 instead of 150 for a mic input?

whay 600 instead of 150 for a mic input?

Click to expand...

To get primary inductance up - for better low-end..

Jakob E.

working on my g9 all night, I've got lundahl 1538's fitted at the input and ll1517's fitted on the out.

the ll1517s on the out have a daughterboard on stripboard, and it gets the point across without too much ugliness, as nice i could anyway.

the ll1538 solution i found is actually decent, maybe there's a more clever way of doing it.... since the pinout is different, i got by nicely with 2 jumpers, 2 cuts, and one wire.

dont have a camera available at the moment, but figured i'd post in case anyone else has 1538's they'd like to use for this.

getting exciting over here! 4 countries are on board, solen, nos rca, lundahl, and nichicon pw! its a new world order mic pre.

I think I'll try an A-26 I have, it is 50/125/200/33/500 to 30K...

On R34, 100k 2w, is it ok to use a 5% instead of a 1%?

What exactly is a "switched" jack, as specified for the G9 DI inputs?

The jacks Ive used only have two connection points PLUS a ground, that goes to the PCB.

Im having some noise/buzz issues on higher gain settings when using the DI input, and Im looking into what I might have done wrong...

[quote author="analogical"]On R34, 100k 2w, is it ok to use a 5% instead of a 1%?[/quote]

Definitely ok, yes. 2W/1% are not easy to find at all, and not neded at all here (look at the schematic - this resistor sets working voltage)

Jakob E.

Finished my G9 today. It seems to be working OK except for some 90Hz hum on both channels. I suspect it might be something with the TL783 regulator.
I meassure 248V on cap #14 (before regulator) and 236V on cap #15 (after reg.) This seems a bit low.....should I replace the TL783 regulator?
Or maybe increase cap #14/15? (they are now 220uF BTW)

Also, ripple is 166mV on cap #14 and 3mV on cap #15......