PCM1704 DAC with ECC88 output - diyAudio
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Old 17th October 2007, 03:38 AM   #1
sandy is offline sandy  India
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Default PCM1704 DAC with ECC88 output

Hi,

I'm using a PCM1704 DAC with 8414 received. I have connected the PIN 14 of the PCM1704 directly to the ECC88 buffer stage...which is from AudioNote. I have attached the schema.

When i turn on the digital signal to the DAC, i get a big "hiss" sound...with the actual music slightly in the back. When there is not digital signal coming in from the transport....the hiss sound disappears.

Could this is a problem due to impedance. Can someone help me integrate the DAC and the tube buffer....any help would be great.

Regards
Sandy
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Old 17th October 2007, 07:42 AM   #2
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Perhaps at 220K the i/v resistor is a little on the large side.
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Old 17th October 2007, 02:49 PM   #3
mgm31 is offline mgm31  France
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See datasheet : http://www.datasheetcatalog.com/data.../PCM1704.shtml

This is a Iout DAC -> needs an I/V converter. The 220k resistor can't be an I/V converter, something is missing
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Old 17th October 2007, 03:04 PM   #4
spencer is offline spencer  Hong Kong
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Change the 220k to 50 to 100 ohm - IV resistor.
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Old 17th October 2007, 05:19 PM   #5
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Quote:
Originally posted by mgm31


This is a Iout DAC -> needs an I/V converter. The 220k resistor can't be an I/V converter, something is missing
I happen to own the dac associated with the shown schematic. The SRPP stage is preceded by a transformer based i/v stage. By connecting directly to the grid of the SRPP stage, the 220k resistor becomes the de facto i/v converter, like it or not, and it is way too big.
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