Is E1DA Cosmos ADCiso a "decent" Phono-ADC?

[wgh52]

Hi folks,

the thread title actually really is the question I'm asking myself because my budget is limited.

Now... I'm just occationally using USB-Out as my audio chain is SPDIF connected. In the "E1DA Cosmos ADCiso" review thread was some talk about this ADC having an internal "SPDIF signal pin just needing output circuitry". So, I'd like to ask the experts to kindly elaborate on that.

Well, so actually two questions arose:
1. Is "E1DA Cosmos ADCiso" fairly well usable as Phono ADC, especially fed by a phono-RIAA-preamp?
2. Which circuitry needs to be implemented for koax and or Toslink SPDIF Output (e.g. driver ICs, transformers, ...)

Thanks a lot for your feedback on the questions!
Regards,
Winfried

 

[MCH]

For the toslink mod part, see here:

Post in thread 'E1DA Cosmos ADC' https://audiosciencereview.com/forum/index.php?threads/e1da-cosmos-adc.27038/post-1848909

 

[KSTR]

2. Which circuitry needs to be implemented for koax and or Toslink SPDIF Output

TOSLINK (recommended as it fully isolated) is easy.
SPDIF pin (3.3V logic) ==> some buffer/driver gate (3.3V) ==> TOTX1350(V,F). Level shifting to 5V is not strictly required as forward voltage is 2.1V(max) but a higher voltage gives a more constant current mode of operation of the LED, mitigating tolerances.

SPDIF coaxial also requires driver, then divided down (impedance matched) to SPDIF level (0.5Vpp into 75Ohm) and capacitively coupled to SPDIF transformer. Or skip the transformer. See for example https://sound-au.com/project85.htm

Be aware that you still need USB connection switch sample rates etc and it might even be required to actually read from USB to start ADC data stream and keep it alive (haven't checked since I own Cosmos ADC for just a few days).

 

[AnalogSteph]

It is a "decent" phono ADC in the same sense that a Ferrari is a "decent" grocery hauler. It can be done, but why? The thing probably has at least 25 dB more dynamic range than you'll ever need for vinyl, and a lot of phonopres aren't necessarily going to be jumping for joy when presented with its input impedance. I mean, you could use the 10 Vrms input range and generally be fine with phonopres that are using decently beefy opamps, or feed it with a headphone amplifier...

It is true that the world is not exactly drowning in good consumer-level ADCs with SPDIF output. Almost nobody needs such a thing these days, not to mention it's also impractical because you have to choose the sample rate on the device itself. It's not like the '90s when you could have requisited a DAT deck. There may well be more options than you'd think, but some thinking outside the box is likely to be required.

 

[wgh52]

Hi Steph,

you're touching points interesting for me. My phono preamp is a Lehmann Black Cube SE II (with modified PWX supply) which I consider "decent" for my music listening system. But "decent" is basically "undefined" or "individually defined".

So, maybe it would help (not just me) to define: What is a "not decent" ADC for phono in a "decent chain"?
I've found this ADC at Audiophonics with a seemingly low spec and old PCM1804 ADC Chip, but can't judge its quality. The good thing for me is its coax & optical SPDIF output and clocking flexibility. Does this qualify as "not decent"?

I'd value your comments.
Greetings,
Winfried

 

[narshorn]

Hello,

I've just installed today this little baby, and using it for the first time with my Douglas Self RIAA ...

A Grade

Balanced RIAA outputs / balanced Cosmos ADC iso inputs, USB3 outs

Nano-switch backplate actual input settings : 1.0kOhm / 2.7V

Acquisition in foobar via foo_record in 32float/96kHz

For now, input level plays between -30 and -20dBFs

So far, no glitches and sound quality is GREAT

Cheers !

n.

 

[AnalogSteph]

Oops, looks like I missed something last year... Better late than never, I suppose?

So, maybe it would help (not just me) to define: What is a "not decent" ADC for phono in a "decent chain"?
I've found this ADC at Audiophonics with a seemingly low spec and old PCM1804 ADC Chip, but can't judge its quality. The good thing for me is its coax & optical SPDIF output and clocking flexibility. Does this qualify as "not decent"?

The meagre specs - including ADC performance being copy-pasted straight from the datasheet - are not exactly promising, there's not even an indication of full-scale input level.

That being said, if it provides a 0 dBFS level around 2 Vrms and performs anywhere near its specs, this board would be a "more than decent" ADC for this application. The chip, while old and basically obsolete now, was deemed good enough for the EMU 1820, 1616 and 0404 audio interfaces in 2004 (though they also released the 1820M, 1616M and 1212M with the now-legendary AK5394 and a better analog stage). (*) Dynamic range is still approaching CS4272 level (plenty for a phonopre), the digital filter is good for an aliasing-free 20 kHz even when operating at 44.1 kHz with an ultimate rejection generally exceeding 100 dB, and digital filter periodic ripple is of modest amplitude (±0.005 dB) and of such high frequency that it should be entirely benign. It's not "mastering grade" but certainly qualifies as "studio grade".

With the benefit of being the better part of a year in the future, the MiniDSP Pocket ADC seems like a hot contender in this space now.

*) Huh, I never knew about the Creative Professional / E-MU -> Universal Audio connection. You live and learn.

 

[wgh52]

Hi Steph,

sincere thanks for responding eventually , even more so for your evaluation of the little PCM1804 ADCboard

I had tested the PCM1804 ADC board, it worked without flaw, no overloads detected with my Lehmann BC SE II, the levels were OK for my chain. Nevertheless, I've seen the miniDSP pocketADC as well as a tempting modern alternative. It's not available in Europe yet, though, but I will probably test it for my use once available. There's not a lot of data about it, so I hope someone in the US can/will provide a unit to Amir so he can thoroughly test it.

Regards,
Winfried