G9 finished + Pic's
« on: April 28, 2012, 11:36:11 AM »
I proudly present my finished G9 Tube Preamp. It took over a year to design the pcb's, front plate, get the components and build the preamp.

I made 3 PCB's for PSU, transformers and the pre's. All pcb's separate star-grounded. The cabling with the front-plate (pot's, Grayhill step-switches, switches;) point to point (seperate shielded). I have shield the 230V mains cable with metal braid too.  Lundahl transformers, Siemens/Wima/Epicos-caps. Phase switch and Mic/Line switch with relay's. At first TAD and JJ tubes.

The preamp worked after first power up  8) After first check up: flat frequency response. 2k and 3k parts. No hum, no noise, sounds neutral. More later.

Here some pics:

Sebastian Barth


Re: G9 finished + Pic's
« Reply #1 on: April 28, 2012, 12:26:08 PM »
Well, there is an unit that is not a clone!:D Very nice job!


Re: G9 finished + Pic's
« Reply #2 on: April 28, 2012, 12:32:47 PM »
Holy Moly,
that´s a beautiful G9. Jacobs concept of the G9 is really outstanding, but the pcb design has got some issues that could be improved. A complete redesign of the pcb was discussed more than once earlier. You did it! Excellent! Any plans for making your pcb design public? What are the LEDs for? Congratulation! "Made in Germany" :)
kind regards


Re: G9 finished + Pic's
« Reply #4 on: April 28, 2012, 12:45:21 PM »
Cool  8) 8) 8)
SSLtech: No bypass, I don't believe in it.
Gus: I think this build might have problems with DIY builders that don't know things like ohms law.


Re: G9 finished + Pic's
« Reply #5 on: April 28, 2012, 02:46:57 PM »
Excellent build. Congrats.


Re: G9 finished + Pic's
« Reply #6 on: April 28, 2012, 05:34:32 PM »
Really great work!!


Re: G9 finished + Pic's
« Reply #7 on: April 28, 2012, 08:39:20 PM »
... well if I remember right it's more than one year ago when we mailed and you wrote about your G7 project...
good things take some time... looks great... how does it sound??? Anything well known like...??


Re: G9 finished + Pic's
« Reply #8 on: April 29, 2012, 11:11:40 AM »
Thank you for your positive feedbacks.

There are 3 LED's: The first LED is for "Line/Mic" switch. It has two colors, green for "Line"- mode, red for "Mic"-mode. The second and third LED are for "Phase" and "Phantom". I took 12V (from heater) with resistor and used two and three-pole switches to switch LED's and functions together - very simple.

I played around with Rightmark Audio Analyser at Metric Halo I/O: frequency response +/- 0,3dB; noise floor at -120db some peeks to -95dB  >:(; THD of the output stage seems a little bit higher: 1,6% at +4dB.

I'll compare the sound with my V72, V672 and V676d with sound examples but this need time.
Sebastian Barth

Re: G9 finished + Pic's
« Reply #9 on: April 30, 2012, 08:17:21 AM »
Wow, well done Barthman!   8)

Re: G9 finished + Pic's
« Reply #10 on: May 11, 2012, 09:47:13 AM »
At first I tested the DI inputs. I compared the G9 with my Manley Tube DI (combined with V72/V672/V676d). I can say that the G9 is a little more brilliant. But I don't know wether this is because the tubes in the Manley DI are older. The brilliance at the high end is not harsh it sounds very good and is a good addition to the rest of my equipment.

Second I tested the line mode with a drum loop and a synth loop. Seems that the G9 output stage lifts the low end lightly if the input stage is on position 1. But there is a lot of well-known gear wich do this to (Urei 1176). Analog audio is not digital blessedly.

Thirdly I raised the input gain. You get a very good sound with higher RMS level in extremely settings too. Very very very nice on Drums and other signals that needs more "dirt" or RMS. But this "dirt" sounds very natural.

Next time I'll write about some mic-settings. A friend gave me a VM1 and I have a cmv 563, KM84 and some AT4050 available for the test. Please bear with me  ;)
Sebastian Barth


Re: G9 finished + Pic's
« Reply #11 on: May 13, 2012, 05:54:26 AM »
No doubt the best looking/most original G9 I have ever seen, well done  ;)

sam system-d

Re: G9 finished + Pic's
« Reply #12 on: June 18, 2012, 07:39:07 PM »
So far one of the coolest I've seen. Congratulations!
« Last Edit: July 01, 2012, 10:41:28 AM by sam system-d »
Je mets les pieds où je veux, et c'est souvent dans la gueule...


Re: G9 finished + Pic's
« Reply #13 on: June 28, 2012, 04:32:49 AM »
Superb! Great work! I looks really classy and modern at the same time.


Re: G9 finished + Pic's
« Reply #14 on: June 28, 2012, 03:39:43 PM »
Wow Sebastian!
Ein Prachtstück!



Re: G9 finished + Pic's
« Reply #15 on: June 28, 2012, 06:44:10 PM »
Wow, thats a some fantastic work!


Re: G9 finished + Pic's
« Reply #16 on: July 08, 2012, 04:37:57 PM »
Wow! That's A real beauty there!!! Great job! I know ya like the sound. I luv mine!

Amateur experimenter


Re: G9 finished + Pic's
« Reply #17 on: January 30, 2013, 09:59:01 AM »
Great design! Especially the I/O trafo. Interesting how it's sound )


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