Tube Based AKM4396 Output Stage - diyAudio
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Old 17th December 2011, 11:57 PM   #1
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Default Tube Based AKM4396 Output Stage

Would this output stage work successfully for an AKM4396 DAC chip?
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Old 18th December 2011, 12:32 AM   #2
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Quote:
Originally Posted by benproiii View Post
Would this output stage work successfully for an AKM4396 DAC chip?
Nothing appears to be faulty. I would make two suggestions which might improve the sound, though:

1) I never like when voltage output DAC datasheets say that they can drive 1k or 2k ohm loads. No doubt they can, but why load the DAC output more than necessary? I'd prefer to see a much larger load, maybe 20k ohms with 270pF in shunt. Noise will be a little higher, but I'd rather trade noise for distortion.

2) Depending on the load presented by the next stage, you might eliminate that MOSFET output buffer altogether.
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Old 18th December 2011, 12:47 AM   #3
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Thanks for quick reply, will do.

How about grounding for the system would this be good.

Common star ground for all PSU's.
Heater (-) and mosfet buffers resistors on separate ground to main gnd
Tube Shield and 47K resistors on separate ground connected to main ground also connected to chassis, with RCA jacks not isolated from chassis.
DAC PCB ground connected to star ground and grid stopper resistors and capacitors connected to DAC PCB ground.
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Old 18th December 2011, 12:49 AM   #4
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FINAL PCB
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Old 18th December 2011, 01:33 AM   #5
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Not enough filtering. Look in the datasheet at their LPF circuits (page 34, 35, 36) and ask yourself why the engineers that design the DAC show more than 1 pole filter (that you have now).
Are they stupid? Then probably you should not use their product.
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Old 18th December 2011, 05:13 AM   #6
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Filtering, filtering, filtering....some time less is more.
Audio engineers some time like too much graphics...

Happy Christmas.

Marco
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Old 18th December 2011, 06:06 AM   #7
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Quote:
Originally Posted by benproiii View Post
Thanks for quick reply, will do.

How about grounding for the system would this be good.

Common star ground for all PSU's.
Heater (-) and mosfet buffers resistors on separate ground to main gnd
Tube Shield and 47K resistors on separate ground connected to main ground also connected to chassis, with RCA jacks not isolated from chassis.
DAC PCB ground connected to star ground and grid stopper resistors and capacitors connected to DAC PCB ground.
Rather than comment directly, please allow me to send you to a rather comprehensive laypersons article here at diyAudio by Dave Davenport. Audio Component Grounding and Interconnection
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Old 19th December 2011, 12:32 AM   #8
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Could I use 3 diodes in series with the AKM's outputs, to prevent the possibility of a grid to anode short destroying the AKM chip.
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Old 20th December 2011, 11:36 PM   #9
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What should the CCS current be for this circuit
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