CM6631 usb audio interface .... any good ?

[KlipschKid]

Originally Posted by Navyblue

I messaged the ebay seller recently. According to him/her, the output is only a few mA, and is good for a Toslink module. But for a coax output extra circuitry is needed.

As for KlipschKid, I wonder if you are taxing the SPDIF output? May be something like a 6:1 transformer to step down the V and beef up the I is more appropriate here? (assuming that such suitable parts exist)

[wizard1238]

according to the cm6631 datasheet, the output current is 8mA 3.3V,
the coax circuit has 300 ohm plus the transformer as load,
uses the famous R=V/I equation,
it's still within 8mA specification, the circuit should work

[Navyblue]

Originally Posted by wizard1238

according to the cm6631 datasheet, the output current is 8mA 3.3V,
the coax circuit has 300 ohm plus the transformer as load,
uses the famous R=V/I equation,
it's still within 8mA specification, the circuit should work

Thanks. I tend to regard "a few" as closer to 0 than 10.

[bvs]

I've recently found a solution for issue that caused when CM6631A module is connected to any Mac USB 2.0 ports.
When you connect module to Mac it is detected as USB Audio Class 1.0 device and you have no ability to use anything more than 48/16.
Module has a reset chip LM810M3-2.93 (http://www.nscrus.ru/content/catalog/pdf/LM810.pdf), but as we can see from the CM6631/32 datasheet, the CM6631A has a power-on self-reset.
So, reset chip has been removed from a board and now the module is always correctly detected as USB Audio Class 2.0 device on any Mac USB port.
This method has been tested on MacBook Pro, Mac Mini and this CM6631A module:
New CM6631 USB Module Assembled Board for DAC3 AD1955 DAC7 WM8741 by Weiliang | eBay
LM810M3-2.93 is a 3-pin chip located on the top of CM6631A.

[Navyblue]

That's interesting.

So you just need to remove it and not jumper anything? To be sure, is that the chip that is marked "SA B"?

[bvs]

Originally Posted by Navyblue

That's interesting.
So you just need to remove it and not jumper anything?

Yes, you are right. XRST (reset) input of CM6631A (pin 98) is internally pulled-down and LM810 is triggering it high (3.3V) when the voltage threshold is obtained (2.93v).
So, when you remove LM810, CM6631A is doing self-reset at power on.

To be sure, is that the chip that is marked "SA B"?

Yes it is 3-pin small chip marked "SA B". I've seen it at many different PCB layouts of CM6631/CM6631A and it is located near pin 98.

[Wayne C]

Hi there I'm new to the forum and am very interested in purchasing one of these units fully made up including case, so that I'm good to go from the off. I have a few questions if I may ask them please?, I have read through all the pages of the thread and noted on one of the first pages that this spdif/USB connector is considered to better the hiface evo?, can anyone confirm this please?. I am considering purchasing a hiface version 2 here in the Uk, and would appreciate any advice on sound quality compared to the afore mentioned products.
I have a MacBook Pro computer and an Audio Synthesis dax decade Dac which goes up to 48 maximum. My main ambition is to buy one of these to connect to the dac as it has no on board USB.

Any links to fully made units would be most welcome, cannot find any on eBay regarding the 6631a with inbuilt power etc.

[Wayne C]

Would this suit my requirements please?

http://www.hifiwow.com/finished-dac-...r-for-dac.html

And would it better the hiface Version 2?

I don't understand the difference between non - synchronous and asynchronous which is the better of the two apparently the hiface is asynchronous thanks in advance.

[wklie]

HiFace 2 uses XMOS chip. Other XMOS-based products include Stello U3 and V-Link 192. XMOS seems to be very popular in high-end audio products.

The hifiwow web site bans my country IP, this fact makes me very suspicious of it.

My understanding is that asynchronous is better.

[bobbybland]

Hi
I've got one of DIYINHK's Isolated 24bit 192kHz USB to I2S/SPDIF CM6631A PCB replacing the faulty first half of an old Cambridge Audio DAC3. All is well except that anything over 96khz is very distorted. Does anyone have any suggestions? I am running windows 7 via usb2 to the four tda1541a, connected with LRCK, BCK and DATA. The original DAC was 16x oversampling, I tried removing the board with the 6 8-Bit Shift Registers but no change. There is a bonus prize for anyone who can explain what this actually did.
Many thanks in advance...