E1DA Cosmos ADC

[staticV3]

Not really possible with XLR-4 to dual XLR3 adapter right?

Sure it is, if the adapter is configured appropriately.

Even for a normal DAC connection to Cosmos, an XLR-3 to dual XLR-3 is required? For this mono measurement

Yes.

 

[Music1969]

Nobody's talking about the DAC to AMP connection.

Ok so now it is clear adding a headphone amp change's nothing at all - still need the same special adapter even with direct DAC connection to Cosmos ADC needs

And in case it helps anyone, here is a cheap option on Amazon

 

[IVX]

Music1969, please select the shortest cable(1/2m is enough) and full of copper. On your pic, I see a too thin one.

 

[Music1969]

Music1969, please select the shortest cable(1/2m is enough) and full of copper. On your pic, I see a too thin one.

Thanks.

I think Hosa is widely available globally

I found this Hosa YXM-121 XLR(F) to Dual XLR(M)

 

[IVX]

Oh yeah, looks better.

 

[Music1969]

Hi @IVX

I have many high SINAD DACs with very low output impedance where Cosmos is great.

but I also have a DIY DAC that has 2000 ohm output impedance, 4Vrms XLR output

Cosmos ADC is not really suitable / accurate for measuring this DAC right ?

Since Cosmos ADC input impedance is so low ?

 

[staticV3]

Cosmos ADC is not really suitable / accurate for measuring this DAC right ? Since Cosmos ADC input impedance is so low ?

Right.
You will need some kind of input buffer to raise the load impedance that the DAC will see to get acceptable measurements.
Many just build their own, though the Cosmos APU is also an option for this.
Its Notch filter has 20kΩ Zi and the Preamp has 47kΩ (both with Bal input).

It should be said though that nowadays there are quite a few Amps with Zi in the neighborhood of 2-10kΩ.
So while adding an input buffer to your Cosmos ADC would most likely improve things with that DIY DAC, those results may not necessarily be representative of real world use.

 

[IVX]

WOW, 2000 ohm sounds like a typo, maybe 200?

 

[Music1969]

WOW, 2000 ohm sounds like a typo, maybe 200?

using audio transformer on output, it is indeed 2000ohms at DAC output unfortunately

So while adding an input buffer to your Cosmos ADC would most likely improve things with that DIY DAC, those results may not necessarily be representative of real world use.

Yes, as per my posts above where I was measuring out of the headphone amp XLR-4 output, I will do this real world measurement

My SMSL SP400 amp has input impedance 47k ohm and output impedance <1 ohm

So probably this will be nice buffer and real world use

I'm more interested in 2 or more tone tests, not really single tone, so not sure the APU is going to benefit what I do much

 

[XLR111]

Hi All

I hope I'm not derailing the threat but I have a quick question.

I have a set of Buchardt a500 speakers connected to a Platin Hub via WISA. The Hub has RCA analogue inputs, but I've heard that the ADC inside the hub isn't very good.

I'm looking for an external ADC that would allow me to connect my Hegel V10 photo stage to the Hub. The Hegel sounds best if I use its balanced XLR out. So ideally I'm looking for a balanced XLR to digital ADC.

Would the Cosmos ADC work for this? My concern is I'm not sure if the Hub can power the Cosmos. I understand the USB input on the Hub is designed to be connected to a computer. Likewise, I understand the USB out on the Cosmos is designed to be connected to a computer.

Any advice appreciated. Many thanks.

 

[somebodyelse]

You're right to be worried about the USB - both the Platin and the Cosmos need to be connected to a computer. You need to look for an ADC with spdif or toslink output.

 

[Music1969]

So my Hosa XLR splitter cable arrived and I ran my measurements

Headamp mainly only adds crap above 20kHz.

I also measured the XLR-4 headamp output and the rear XLR-3 outputs - same output impedance of < 1ohm

It might be cleaner out the back, I haven't checked


SMSL D-6 DAC direct into Cosmos ADC (not headamp connection):



SMSL D-6 DAC connected to SMSL SP400 pre/headamp XLR-4 output:





THD+N of the DAC alone with 1kHz tone :



THD+N of DAC+amp at 1kHz tone:



Frequency response of DAC+headamp:

 

[XLR111]

You're right to be worried about the USB - both the Platin and the Cosmos need to be connected to a computer. You need to look for an ADC with spdif or toslink output.

Many thanks. A sub-$300 ADC with XLR in / spdif or toslink out is surprisingly difficult to find!

 

[Music1969]

I measured frequency response of my DAC+Amp/pre

This is using PCM353kHz periodic white noise generator in REW - so frequency response should be flat to over 100kHz



Obviously this is the frequency response of my SMSL SP400 headamp/pre , since frequency response should be flat to over 100kHz with a PCM353 test file

@IVX For Cosmos APU , how many dB down at 100 kHz is the preamp frequency response?

Edit: Actually I just measured my DAC direct into Cosmos ADC and it gives same response (PCM353 kHz test file).

So my amp is not actually causing any additional roll-off up to 100kHz . Nice !

So I wonder if this roll-off is actually the Cosmos ADC, not my DAC or amp ?

 

[IVX]

Music1969,
please read the product description https://e1dashz.wixsite.com/index/cosmos-adc

 

[Music1969]

Music1969,
please read the product description https://e1dashz.wixsite.com/index/cosmos-adc

I did, I am using the default (linear phase apodizing)

Do you expect Cosmos ADC to look like my plot above with PCM353 kHz input

Approx -5dB down at 100 kHz ?

I am not saying there is a problem - there is no problem - I only want to understand where this rolloff is coming from

 

[IVX]

Guys, I have one question about Win11+ADC issue. The user just reported that his new HP laptop with Win11 records ONLY the left channel from Cosmos ADC, and sends that to the right channel as well, like a mono ADC interface. Again, it is not about my MONO mode(i.e. not about internal ADC regime), the user can switch that by Windows volume slider and see the LEDs become green, so the problem isn't about that, but seems about UAC2 implementation in Win11, at least in that particular build. Another W11 PC of the same user works ok with the same ADC. Please leave a short text about your experience with W11 if any. Thank you.

 

[IVX]

the out-of-band noise hump is reduced, just by the way.
I think you guys remember that hump if used 384k of sampling rate, it starts from 100k and higher so that hump is reduced. Furthermore, 10-20k H3 is also dropped to 3db or so. A-weighted noise may be .1db improved, so the new FW is about out-of-band noise mostly.

 

[IVX]

Old vs new FW:

 

[VintageFlanker]

THD+N of the DAC alone with 1kHz tone :

Your input level is too high. You should be way closer to 0dBFS. Try to lower it (say, 3.5Vrms switch for 4Vrms XLR outputs, when plugged in Mono/Y XLR splitter).

I am using the default (linear phase apodizing)

Use Minimum Phase for a flatter FR.