Gates Tube Mixer Schematic New
« on: September 11, 2009, 12:53:47 AM »
Here's a schematic for a nice little 4 bottle 3 X 1 Gates tube mixer in case anyone's interested.  Bought this from a forum member recently.  Very good sounding amp.

Please note:

The capacitor in parallel with the 6C5 cathode resistor is not an electrolytic.  It appeared to be a mica type (small brown square - like a chocolate mint).  Could not read any code or value from it.  Perhaps a senior member can suggest an appropriate value here.

Also the 1620 cathode bypass cap is an electrolytic.  The question mark is there because it was impossible to read the exact value.  I ventured a guess of 40uF/25V based on size and the use of this value on the following 6J7.  

Current draw at 250V B+ is around 20mA


« Last Edit: January 02, 2011, 12:42:06 AM by lassoharp »


EmRR

Re: Gates Tube Mixer Schematic
« Reply #1 on: September 11, 2009, 03:06:57 AM »
Nice drawing.  25/25 and 50/25 is common on Gates cathodes of this era.  The mica is there for high frequency boost or correction, and was probably selected during QC.  Many Gates schematics state such. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

PRR

Re: Gates Tube Mixer Schematic
« Reply #2 on: September 11, 2009, 08:40:50 PM »
Volume pot is probably drawn wrong.

PRR

Re: Gates Tube Mixer Schematic
« Reply #3 on: September 11, 2009, 08:56:15 PM »
First three stages draw 1mA, 1.1mA, 2.9mA, total 5mA. This is clear by the helpful voltage notes and the resistance values. (And a small fudge for 2nd stage G2 current.)

Unless that 6N7 is sick, with that voltage and bias it will pull 6mA per section, 12mA.

Total 17mA.

Supply voltage is limited to ~~320V by the 300V cap in the 2nd stage and the 6N7 rating. I don't think a 20% change of supply makes much difference.

Re: Gates Tube Mixer Schematic
« Reply #4 on: September 11, 2009, 10:37:57 PM »
PRR

When you say supply voltage limited to ~320 - is this the no load voltage or max at full load?


 

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