Open-source USB interface: Audio Widget

[UnixMan]

Originally Posted by 2A3SET

I am not sure if we can design a good CCS with low dropout of 1.7V (5v-3.3v) and good PSRR to work with shunt.

Although for best quality I'd definitely use an indipendent power supply with (much) higher voltage, doing that would be great for portable use. Problem is, available voltage is really too small.

Perhaps for portable use you should consider a dedicated DC/DC converter which is completely disabled when providing an external power supply? (I'd say at least 12V!).

[UnixMan]

In the AW thread on our italian forum a friend asked about the possibility to use the AW digital board (USB/I2S module) with the TP "Buffalo" DAC that he already owns. See post #94655, post #p94671, etc.

I'm not sure about all the details, so I ask it here 'cause I bet that there are quite many owners of a Buffalo DAC which may be interested to the answer...

Q: is it possible to use a Buffalo (I, II or III) in place of the AB? how easy/hard would it be to do so?

Q: What modifications needs to be done to the Buffalo and/or to the AW?

Q: What extra circuitry needs to be added?

(perhaps we should start another thread dedicated to this subject?)

[borges]

Could you point me to an updated schematic for the Buffalo?

The signals that pass throgh the USB-I2S module are I2S (11.2896 or 12.288MHz bit clock) out and MCLK (same two frequencies) in. The module can be VBUS powered or use an external power supply. The latter case might pose some challenges to bootup and enumeration. But that is only speculation from my side.

Børge

[UnixMan]

Originally Posted by borges

Could you point me to an updated schematic for the Buffalo?

no idea where to find it.

On the TP site there is the page about the new Buffalo III, but I can't find the schematics for it. At the end of the page there are a few links to old Buffalo's (I, II & 32s) documentation, but no schematic whatsoever (except perhaps for the very 1st one).

[2A3SET]

Hopefully this helps, wiring from Musiland to Buffalo II.

Musiland 03 I2S to Buffalo II DAC: Playing 352.8Khz Music H i F i D U I N O

And the Buffalo III manual,

http://www.twistedpearaudio.com/docs...ide_V1.0.1.pdf

Originally Posted by UnixMan

no idea where to find it.

On the TP site there is the page about the new Buffalo III, but I can't find the schematics for it. At the end of the page there are a few links to old Buffalo's (I, II & 32s) documentation, but no schematic whatsoever (except perhaps for the very 1st one).

[GeorgeBoudreau]

Hi Borge,

The Buffalo III uses the ES9018. Between the users manual and the spec sheets you have you have enough info.

I thought the MCLK from your I2S module ran 22/24 mhz ?

[borges]

Hi George,

yes, the MCLK to the DAC is 22/24. But the serial output of the MCU won't run that fast, so there's a /2 JK flip-flop between the XO and the module.

The ES9023 needs to run its sigma-delta modulator at 22/24 in order to have high enough oversampling rates for 176.4/192 input. We could use 44/48MHz MCLKs too. The AB-1.1 board allows for that by coupling two JKs in series to divide by 4. Higher frequencies mean more jitter but also higher oversampling rates. Might be a profitable and audible trade off.

BTW, what is your clock setup like? AB-1.1 MUXes two fixed-frequency XOs from Golledge.

11/12MHz is sufficient for 24 + 24 bits at 176.4 / 192. I use the same rate in my CD player for 24 bits at 352.8 / 384. That leaves 8 dead bits which is practical since running I2S bumper-to-bumper can be a little uncomfortable.

Børge

Originally Posted by GeorgeBoudreau

Hi Borge,

The Buffalo III uses the ES9018. Between the users manual and the spec sheets you have you have enough info.

I thought the MCLK from your I2S module ran 22/24 mhz ?

[borges]

The manual says:

"The Buffalo III DAC board uses a custom on-board ultra low jitter, low phase noise 100Mhz clock from
Crystek. The clock module lowers jitter significantly when compared to normal clocks. The clock is placed
on the board near the DAC chip to keep phase noise at low levels."

That is not immediately compatible with the USB-I2S module. But I'll have to read a bit more to tell.

Børge

Originally Posted by 2A3SET

Hopefully this helps, wiring from Musiland to Buffalo II.

Musiland 03 I2S to Buffalo II DAC: Playing 352.8Khz Music H i F i D U I N O

And the Buffalo III manual,

http://www.twistedpearaudio.com/docs...ide_V1.0.1.pdf

[GeorgeBoudreau]

Hi Børge

I use a Si532 dual output clock into a divider to feed the cpu. Output freq is selected by the cpu depending on the bit rate requested.

Although it makes for a compact board the clock is custom ordered at $20 a pop not including shipping. warning::: do not order small quantities as the courier costs at almost $90 are a killer.

George

[UnixMan]

Originally Posted by GeorgeBoudreau

The Buffalo III uses the ES9018.

as does version two. IIRC Buffalo II by default had a slower clock, either 40 or 80 MHz.