G9 Finished - with External PSU - and Pics

bruce0

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Jan 24, 2010
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Boston
Just finished this G9 build. 

I used off the shelf PSU's that I had lying around for the power.  48V and 250V.
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I used Factory Automation cables rated for 600VDC.  Really nice, really cheap and pre-built.
The PSU will handle more than one unit, using a daisy chain T connector,shown below.
A bit of a "Steam Punk" look from drawing the front panel with an engraver by hand... but I like it.

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I may have to change the way I run the relays.  The RC filter drops 9V when the relays are activated.  But they only get activated in Line mode (so no phantom then) so it might be ok.

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I like the connectors, molded rubbery plastic, with machined aluminum screw closures, gold contacts.  They come in up to 6 conductors, and are very very flexible but 16AWG wire.

The interior of the case is pretty empty, in case anyone is interested here are some of the trace cuts in combination with a couple of straps this will run the 4 tube heaters in series on 48V.

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I use 24V relays, with dropping resistors.  I put an RC filter on both the 250V and the 48V on the board. 

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I am interested in the trace cut modification that is mentioned in the G9 thread, but I can't find any instructions on that.  If anyone can point me directly at that I would appreciate it.  I have not started audio testing on this yet, just checking voltages etc.  I may need to change the 48V around a bit - when the relays are activated the heaters don't get enough current.  But the heaters don't need to be filtered, so I think I can fix that and I think I will run some signal through it after the 4th.

I used some old Altec input transformers
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gyraf

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Nice!!

I am interested in the trace cut modification that is mentioned in the G9 thread,

http://www.gyraf.dk/gy_pd/g9/g9pd.htm - under edits of 08. jan. 2007

http://www.gyraf.dk/gy_pd/g9/G9-EDIT.GIF

Jakob E.
 

bruce0

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Jan 24, 2010
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1,065
Location
Boston
Well I got some test audio through it.

Channel 1 operates as expected, although it does go sort of nuts at high gain, so I guess I have the oscillation problem and will try the trace cuts and directly wiring a shielded INST jack.

Channel 2 does not make sense, in line mode the gain switch and output switch do nothing.  In Mic mode, works as expected.  I have to look into that.

Oddly, even with no PSU my test data shows 60hz noise, and all the harmonics are distinctly present.  So I need to look at my filtration and grounding.

More to follow.
 

bruce0

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Jan 24, 2010
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1,065
Location
Boston
All is better.

The channel 2 problem was the ground and atten. wires switched on the connector (oops).
Both channels work the same now.

Also, I need to change the gain switch because my switch (cheap chinese) has the 11th click on the beginning (so the all the way down position is like between 4 and 5.  So a little re-soldering there.

The noise is not really there.  My test gear is an unbalanced interface (or pseudo balanced) and I am picking up some ground noise.

I will get some better data when I put in the new switches and get it racked.
 

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