Lots of G9 related stuff recently, so I thought I'd join in.
Having lost my first G9 to the studio forever, I put together second G9 for home use (if I'm lucky), based on leftovers from other projects, and bargain bin bits.
I got two lundahl 1530 xfos from canford audio (1:7) at discount price for the inputs, and used a pair of BBC LL228s for the output (a fiver each!). These are 2.8:1 ratio but work fine - a little less output level than 2:1, obviously. I changed the 10K resistor across the secondary to 5K so that the output stage is still seeing the same load.
Some other changes - I was short on rotary switches and had no relays around so I skipped the whole phantom power and line level selection, and also omitted the phase switch. I'm usually using ribbons or tube mics, so I can live without phantom. HPF is just on-off; I picked a cap value somewhere between the two that Jakob uses - 15nF, I think.
Had some trouble with earth hum on this unit at first. Carful rotation of the two toroidal mains transformers was necessary. I got a great improvement by connecting the -ve side of the output transformers directly to ground using thick guage wire - that fixed it.
Some pictures showing the simpified front - haven't cleaned or labelled it yet so you can still see my marking out for drilling. BIG chicken head knobs always sound better....
Inside, you can see the transformers next to the PCB (one of Swedish Chef's - very good quality :wink: ), and the thick ground bus. It's not quite complete yet. Still need to nail down a couple of components.
Cheesy picture of the tubes lighting up..... :green:
:thumb: z50
Having lost my first G9 to the studio forever, I put together second G9 for home use (if I'm lucky), based on leftovers from other projects, and bargain bin bits.
I got two lundahl 1530 xfos from canford audio (1:7) at discount price for the inputs, and used a pair of BBC LL228s for the output (a fiver each!). These are 2.8:1 ratio but work fine - a little less output level than 2:1, obviously. I changed the 10K resistor across the secondary to 5K so that the output stage is still seeing the same load.
Some other changes - I was short on rotary switches and had no relays around so I skipped the whole phantom power and line level selection, and also omitted the phase switch. I'm usually using ribbons or tube mics, so I can live without phantom. HPF is just on-off; I picked a cap value somewhere between the two that Jakob uses - 15nF, I think.
Had some trouble with earth hum on this unit at first. Carful rotation of the two toroidal mains transformers was necessary. I got a great improvement by connecting the -ve side of the output transformers directly to ground using thick guage wire - that fixed it.
Some pictures showing the simpified front - haven't cleaned or labelled it yet so you can still see my marking out for drilling. BIG chicken head knobs always sound better....
Inside, you can see the transformers next to the PCB (one of Swedish Chef's - very good quality :wink: ), and the thick ground bus. It's not quite complete yet. Still need to nail down a couple of components.
Cheesy picture of the tubes lighting up..... :green:
:thumb: z50