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Old 31st May 2008, 11:22 PM   #21
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Quote:
Originally posted by coloradosound
OK,
Way too many pages here to read through everything
on a public library computer!
Is this Buffalo DAC suitable for 8 channels.
I wouldn't mind having some of the Sabre chips in stereo
mode to get top performance from each chip rather than
trying to do 8 channels on one chip.

You could do 8 channels with 4 Buffalo DACs.

Its a stereo DAC. If you want you can use a clock distribution IC (off board) and supply all 4 buffalos with the same master clock. But I doubt its really required to get excellent results. But you know someones going to try it.

Cheers!
Russ
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Old 31st May 2008, 11:27 PM   #22
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Russ,

Do you know how much gain the opamps give in the scenario you are using now?
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Old 31st May 2008, 11:32 PM   #23
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Quote:
Originally posted by khundude
Russ,

Do you know how much gain the opamps give in the scenario you are using now?

About 6db if you look at the DAC as a voltage source in series with its output impedance, which it actually is, go figure.

The resulting output will be 2VRMs at 0db output from the DAC.

Cheers!
Russ
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Old 1st June 2008, 01:49 PM   #24
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So the IVY is essentially acting as a buffer and SE output?
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Old 1st June 2008, 03:19 PM   #25
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Quote:
Originally posted by khundude
So the IVY is essentially acting as a buffer and SE output?

Even as I have it configured now its a bit more than that. For one thing its a filter too, and it acts to effectively cancel low order harmonics.

But yes it, does have the pleasant effect of creating a nice low output impedance and creating a SE output too.

Cheers!
Russ
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Old 1st June 2008, 06:37 PM   #26
matejS is offline matejS  Slovenia
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Hi!

One question regarding IVY...

THS4131 datasheet says:
"For the prevention of noise going through the device, use a 0.1µF capacitor on the VOCM
pin as a bypass capacitor."

IVY has it connected directly to the GND. Have you tried to bypass it?

Thanks,
Matej
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Old 1st June 2008, 07:26 PM   #27
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Quote:
Originally posted by Russ White



You could do 8 channels with 4 Buffalo DACs.

Its a stereo DAC. If you want you can use a clock distribution IC (off board) and supply all 4 buffalos with the same master clock. But I doubt its really required to get excellent results. But you know someones going to try it.

Cheers!
Russ

Russ,
Thanks for helping me get back up to speed on this thread
I get to use a public library computer for 55min per day if I
come down. (I usually only do every other day).
So who is selling the boards, how much, and what all is
on it? (blank board or w/sabre chip and or other components)?
I have various Jensen transformers as I notice many of you
are choosing various output devices and configs (OP amps,
tubes, tranny's, etc.
I wouldn't mind getting 4 if affordable.
Gary
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Old 1st June 2008, 10:53 PM   #28
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Quote:
Originally posted by matejS
Hi!

One question regarding IVY...

THS4131 datasheet says:
"For the prevention of noise going through the device, use a 0.1�F capacitor on the VOCM
pin as a bypass capacitor."

IVY has it connected directly to the GND. Have you tried to bypass it?

Thanks,
Matej

Well it only needs to be bypassed to GND if it some other voltage than GND. For example a single supply application where VOCM was VCC/2.

In case of the IVY VOCM is GND, so there is no logic in byspassing GND to GND.

Cheers!
Russ
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Old 9th June 2008, 03:17 PM   #29
ichiban is offline ichiban  United States
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Default RE: tweak of Ivy

Very nice

A finer resolution of detail and edgeless.

Keep up the excellent work.

Thank You TP-Guys
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Old 16th June 2008, 03:15 PM   #30
Vadim is offline Vadim  Canada
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I am looking to get the Buffalo-IVY-Dual-power-supply kit, when it becomes available, and use with my DCX2496. I have a question regarding the implementation of the IVY circuit.

Looking at the schematics of IVY board
http://www.twistedpearaudio.com/imag..._schematic.pdf

I noticed that the Low-Pass filter is a 1st order and has a cut-off frequency of 202 kHz. I also looked at White paper published by ESS Technology
http://www.esstech.com/techsupp/Appl...PCB_Layout.pdf

and there the filter is a passive 2nd order network implemented around the AD797 with a cut-off frequency of about 100 kHz.

The ESS White Paper does not seem to mention the oversampling rate of the Sabre DAC, so it is hard to comment on the appropriate anti-aliasing filter order or its cut-off frequency.

Still, why not use a lower cut-off, - perhaps in the 50-60 kHz range, because the 20kHz pass-band will not be effected by any more then a tiny fraction of a dB in this case anyway while getting a benefit of better noise suppression? Comments?

Vadim
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