IVX
Major Contributor
Sorry, I have no plans to add that. You know, only 1-2 people asked about SPDIF, 0.1% of all Cosmos ADC users.
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E1DA Cosmos ADC
- Thread starter mansr
- Start date
melowman
Active Member
- Joined
- Sep 18, 2020
- Messages
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In this thread we’ve been more than 1-2. Plus I know many people in the music world which are interested in SPDIF (and Word clock). You’d gain a fair amount of clients thanks to those features implemented.
Anyways, it’s a shame. But you’re the boss. But it’s a shame.. :-(
Anyways, it’s a shame. But you’re the boss. But it’s a shame.. :-(
IVX
Major Contributor
In that model, I simply can't give you stereo SPDIF(two ADC chips, two mono SPDIF outputs), I2S only. If you really need, go ahead, use I2S->SPDIF adapter.
Re that word clock - is that meant to be input or output? Output is viable, one of the I2S wires + some buffer, but input would require PLL from the very low-freq to MCLK - I wonder what jitter would be then, apart of the extra required circuits.
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I would have kept the Cosmos ADC I had purchased if it had an optical (or coaxial or AES/EBU) output. For a measuring device it's nice, but if you don't measure things often, it sort of ends up just sitting around unused as a one-trick-pony. With a standard digital output: It could be used with most any recording studio interface via a standard converter: you can easily go from spdif to optical to aes/ebu. You could hook it up to a 20-year-old interface to upgrade your sound or connect it to most any professional recording studio device made including newer devices like a Neumann MT-48 or Motu MK5 for additional inputs.
I could see the use case for mastering studio engineers who want to simply implement the highest-quality ADC into their current setup with minimal hassle. Live sound and broadcast also implements ADC's to add two extra analog inputs into their system. By incorporating a standard digital output - you may be able to attract recording studios and mastering studios and commercial/industrial/live sound/ broadcast type customers which may end up being a much much larger customer base than your current customer base. Perhaps this is not the forum you'd want to market it to though as there are more pro-audio oriented sites which may be more interested in such a product?
Two separate digital mono outputs is fine for recording/mastering/etc. I2S to SPDIF: I don't think professionals would want to deal with that as I2S is not a normal thing in pro audio.
A good example of what could be done if there was a standard digital output such as spdif: you could hook it up to a RME Digiface USB and clock the Digiface (Or HDSPe AIO or Ray Dat or older 9652) to the input signal from the Cosmos ADC for 2 great analog inputs, and the optical outs can easily go to any DAC (Perhaps a future Cosmos DAC with standard digital input?) or digital speakers and volume can be controlled with the RME ARC USB - for 7.1.4 Dolby Atmos monitoring and a clean 2 channel ADC and you can route the Cosmos ADC inputs to anything really due to the Totalmix software including easily monitoring what your recording if tracking.
I probably went through a dozen pro audio interfaces from different companies since I bought the Cosmos - and if it would have had a normal digital output: I would have been able to use it with every single different audio interface and I'd still be using it right now.
IVX
Major Contributor
nanook
Addicted to Fun and Learning
The input impedance will drop accordingly, or do you hook up both ADC inputs to one OPA1612A?
Meanwhile I frequently use the Scaler in front of the ADCiso - I get a high-Z input and the output for mono-mode ( -> REW set to "cross correlation averaging) The ADCiso stays configured to 4.5V and in case I need some gain it's available at the turn of a knob. Most of the time I choose the gain manually.
-> Did you consider to integrate the functionality of the Scaler into the new design? This would need a broader case, but that wouldn't bother me at all.
Meanwhile I frequently use the Scaler in front of the ADCiso - I get a high-Z input and the output for mono-mode ( -> REW set to "cross correlation averaging) The ADCiso stays configured to 4.5V and in case I need some gain it's available at the turn of a knob. Most of the time I choose the gain manually.
-> Did you consider to integrate the functionality of the Scaler into the new design? This would need a broader case, but that wouldn't bother me at all.
IVX
Major Contributor
IVX
Major Contributor
And finally, we have a good question! Of course, I'm not a magician to get 3db lower noise with the same frontend. I added the feedback resistor switch 680/280ohms, so now the ADC has two groups of sensitivity. 680ohms, the same voltages and impedances as before(1.7/2.65/4.5/5.33V), and low-noise 280ohms group with higher voltages (3/4.7/7.8/9.5V) but the same impedances.
nanook
Addicted to Fun and Learning
That performance is indeed incredible!
IVX
Major Contributor
Don't you worry, it's a sweet spot of course
ES chip gives a worse result just going +.1dbfs or -.3dbfs, but indeed, DM is cleaner vs Cosmos ADC. Somewhere I lost about half of the DB on the noise-modulation, and found only part of this in the tight low-noise voltage regulation(including opamps rails). The ADC still doesn't gain 3db MONO vs STEREO due to some common noise fraction in both channels. I'm ready to investigate that one more year, but my boss, Sunny, is pushing me to finish the design.
IVX
Major Contributor
BTW, I've got the best THD+N@1k result from the chain like that: 9039S->Scaler->Cosmos_LPF. The result with Cosmos APU is -132.5-133db or around -127db for Cosmos ADC DM.
IVX
Major Contributor
IVX
Major Contributor
Right, it is the "thermostat" board, new one. BTW, I prepared a short video showing how the board affects THD/THD+N performance.
IVX
Major Contributor
Since the model is already Dual Mono (DM), the "MONO" mode is only available in the REW via "Virtual balanced input/Sum". The sine gen is E1DA9039S->Comos_Scaler->Cosmos_LPF with THD+N -132-133db.
IVX
Major Contributor
Cosmos ADC DM, DC Bias control via Tweak_Cosmos_DM.exe
IVX
Major Contributor
The video above is about rare^rare Grade 00 sample, but what about more common Grade B or A? Here is kinda Grade AB i.e. Lch 128.0db(A) and Rch 127.4db(A), MONO is 130.7db(A). I never saw Cosmos ADC/ADCiso THD+N@1k better than -125db, Cosmos ADC DM Grade AB gave us close to -126db(A)! Hence, Grade AA is surely better than -126db.
