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In Reply to: RE: DAC Output Stage - a few more questions.... posted by bcherry on December 30, 2009 at 21:17:09
Hi Brian,
I ordered the kit today, I decided on (1) UTS.
It was going to be tough to shoehorn two of those modules in there anyway... :-)
The only thing to clarify is the wiring between the DAC chip and the module, let's see if I've got this close:
DAC pin 26 (L-) to UTS terminal 'in L'
DAC pin 25 (L+) to 22 ohm resistor, resistor to GND
DAC pin 18 (R-) to UTS terminal 'in R'
DAC pin 17 (R+) to 22 ohm resistor, resistor to GND
In the Denon schematic, all four AGND pins (16, 19, 24, 27) are tied together....this will be my analog ground, correct?
If correct, let's call this GND.
GND to UTS terminal 'Gnd L'
GND to UTS terminal 'Gnd R'
GND to UTS terminal 'Vcom L'
GND to UTS terminal 'Vcom R'
So far so good?
The schematic on page 22 of the manual shows (4) 51 ohm resistors.
What do I do about those?
I could locate the 22 ohm resistors close to the DAC chip, or I could mount them somewhere on the UTS....which is preferred?
Thanks,
Mike
Follow Ups:
> DAC pin 26 (L-) to UTS terminal 'in L'
Please remember to connect a 51 Ohm resistor in parallel to in L and to connect Vcom & Gnd.
This gives the correct output levels for a 7.8mA Current output.
> DAC pin 25 (L+) to 22 ohm resistor, resistor to GND
Yes .
> DAC pin 18 (R-) to UTS terminal 'in R'
See notes for L-.
> DAC pin 17 (R+) to 22 ohm resistor, resistor to GND
Yes.
> In the Denon schematic, all four AGND pins (16, 19, 24, 27) are tied
> together....this will be my analog ground, correct?
Yes.
> If correct, let's call this GND.
Ok.
> GND to UTS terminal 'Gnd L'
> GND to UTS terminal 'Gnd R'
> GND to UTS terminal 'Vcom L'
> GND to UTS terminal 'Vcom R'
Yes.
> The schematic on page 22 of the manual shows (4) 51 ohm resistors.
> What do I do about those?
The two for the inputs to the UTS stay, the other two become 22 Ohm.
> I could locate the 22 ohm resistors close to the DAC chip, or I could mount
> them somewhere on the UTS....which is preferred?
Makes little difference, just do what is most convenient to do.
And of course you must disconnect the existing I/V conversion stages in the Denon Player (cut trace or remove Op-Amp and Op-Amp feedback resistor).
regards
DIY - Done Right!
on the underside of the existing analog board to mount the 22 and 51 ohm resistors.
- What's the minimum wattage I can get away with?
- Will metal film resistors be fine?
Mike
> - What's the minimum wattage I can get away with?
1/8 Watt (0.125W)
> - Will metal film resistors be fine?
Yes.
DIY - Done Right!
and is making sweet music!
Here are a few photos of the installation:
I nestled the power transformer behind the existing power switch, after relocating a few circuit boards.
The transformer was fastened to the chassis with one 6MM bolt thru the bottom.
To fit the tube output board, I had to remove the video portion of the player. This was not a problem
for me as I use the unit for CD playback only. An aluminum plate was fabricated to mount to (4) newly
vacant mounting tabs....in turn, the board was bolted to that plate.
The output signals were taken to a pair of chassis mounted RCA jacks installed into some unused holes.
The sound is very good! Smooth, extended frequency response, and very musical....MUCH better than stock!
Thanks for all the help Brian,
Mike
Hi Mike,
Would you mind sending me an e-mail through the forum system, I'd like to ask you something in private?
Ciao T
Thanks Mike for taking the time to post that and your listening impressions. The word is finally get out that real tube anode output as opposed to a tube buffer delivers the music.
worst: opamps
better: tube buffer
best: tube output stage
regards
Brian
DIY - Done Right!
Brian
Where does passive IV conversion with transformer fit into this list?
Regards
Grantn
We haven't done any A/B comparisons as difficult to implement. But I would expect it to sound very good if done right.
regards
Brian
DIY - Done Right!
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