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Messages - 45Triode

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Is QLS-HIFI planning on attending the Rocky Mountain Audio Fest (RMAF) this October 11-13th in Colorado USA?

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Suggestions and Requests / Re: QA660 usage with PCM1704 DAC
« on: May 15, 2013, 12:52:23 PM »
Normally people would use a digital filter to make the waveforms look good on test gear.
How do they affect the sound is what you should ask yourself? There is no free lunch in life
as you know there is always trade offs.

All amplifiers are low pass or bandpass filters like it or not. Mine is a bandpass where the
upper pole is low enough to add additional filtering of the unwanted high frequency products.
In listening tests these out of the audio band filters still have some effects in the audio band
that you hear.

Yes I'm running the WAV only firmware ver. WAV-1.0.0   date  2013.04.10.
Seems to work good.

There are 20 to 30 file formats out there and once again I'm using the best (UNCOMPRESSED) possible.

Only way to get the best sound is to very very carefully choose each part/ circuit of the player as it all has to
work as a system to bring out the emotion in the music.


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Suggestions and Requests / Re: QA660 usage with PCM1704 DAC
« on: May 15, 2013, 08:30:12 AM »
For now-  JUST SAY NO TO DIGITAL FILTERS.
I use a simple analog RC filter and a tube amplifier output stage for filtering.
Sound is better than the best JFETS, or OP AMPS.

Digital filters only look good on paper they do not improve jitter only make it worse.

The plan is to give this system analog like vinal quality sound. I have spent $$$ auditioning
digital playback devices and they all sound different and none as good as a good CD player.
Why is that? Even QLS says this is only equal to a few $$ CD player. Theory says a pure
digital devices like the 660 should sound better than all the processing that takes place in a CD player.

Look at all the power supply work QLS did in the QA660. That rigor needs to be applied
to the D/A processor also.

Remember all digital signals are really analog in nature. They can have overshoot, ringing, noise, etc.

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Suggestions and Requests / Re: QA660 usage with PCM1704 DAC
« on: May 14, 2013, 11:41:58 PM »
No reason that it should stop the other outputs.
I'm not using those outputs because they are compromised outputs and are lower quality compared to I2S.
It does not get any better than I2S the input format DAC's use.
There are many, many other less expensive players out there to buy if you want SPDIF or TOSLINK.

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Suggestions and Requests / Re: QA660 usage with PCM1704 DAC
« on: May 14, 2013, 05:27:40 PM »
The I2S output comes from a quad buffer U3 (74VHC125).
U3's input comes from a ATMEL  32UC3A3256 uP.
The processor is responsible for format/ timing of the DATA.

Anyone out there who can reprogram this processor, I will make it worth your while!
I'm a hardware guy as you can tell.

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Suggestions and Requests / Re: QA660 usage with PCM1704 DAC
« on: May 14, 2013, 09:09:12 AM »
Thanks Aliu

I all ready have a working shift register board to drive the worlds best ladder DAC (PCM1704). My board uses 7 SMD IC's
and lots of discrete parts. It would be great to get rid of all this extra hardware.

I'm looking for someone that can tweek the code to make the QA660 I2S output the correct
format for this DAC.

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Suggestions and Requests / QA660 usage with PCM1704 DAC
« on: May 13, 2013, 04:18:11 PM »
Is is possible to do a software update so the I2S output can drive a TI/ Burr Brown PCM1704 DAC?

This would reduce external circuit complexity and may lower jitter.  One must keep the rest of the system
as pure and clean as you have done in the QA660.

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