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E1DA Cosmos APU - Teardown and personal thoughts and measurements

pma

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Your audio buffer looks nice! Before purchasing Cosmos APU, I made a simple imput buffer using an OP AMP (Analog Devices AD797). I have adopted the noninverting configuration of the OP AMP, and its impedance is enough high for the DAC. However, I could not lower its noise level as Cosmos APU's. Unfortunately, I am a software engineer, not a professional circuit designer. :D
AD797 is an excellent opamp, still one of the best ones. However, it may be prone to oscillations. Looking at the noise floor modulation in your plot, I would say it was the case. You know, it is hard to find anything with lower noise than AD797, even nowadays. Kudos to Scott Wurcer.
 
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trl

trl

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There are many situations when we need input impedance at least 10kohm and more.
Per https://e1dashz.wixsite.com/index/cosmos-apu I see that input impedances are higher than the E1DA Cosmos ADC:

"Notch: balanced (FDA) up to 10Vrms(active clamp to 15Vpeak)
gain = 20db + 0/6db(switchable), Zi=20/10kohm bal/unbal [...]"

"Preamp: balanced (FDA) up to 3.5Vrms(10oHm to TVS clamped!), gain = 34/60db
Zi=47/23.5k bal/unbal [...]"


Unless I'm wrong here, we're talking about 20 KOhm input impedance @ Notch inputs and 47 KOhm @ Preamp inputs, so I guess we can easily use the APU in front of the ADC without getting worried much if the input impedance affecting the output stage of the DUT.
 

Herbert

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But it's small enough to be called portable, right? We're talking about a PCBA of 90x50x29mm or 104x61x39mm with the original case, so pretty similar with a power bank containing a couple of 18650 or 21700 batteries inside, like the one I've used in my test. APU is using a case with the same dimensions as E1DA ADC, see below:

No, THIS is portable. Just a 48V Phantom power supply but lacking any means to rise the output gain:
P1-scrolljack-image.jpg

Dimensions are 105 x 44 x 33 mm / 4.13" x 1.73" x 1.3"
Can be easily mounted on a boom pole next to the mic.
 

pseudoid

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Probably, I am too late to the party after 3+ pages but a poll would have been a nice addition to you great post.
I would have voted at least a "3. Fine".
Thank you , @trl
 

thin bLue

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As one of the early proponents of the 48V power option, I'm very happy to see this review in here ASR.
 

IVX

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As one of the early proponents of the 48V power option, I'm very happy to see this review in here ASR.
Yeah, 48DC power isn't my idea at all, someone in our discord recommended adding it. The same about vinyl ripping. Both these options are nearly free for the Bill Of Materials so, why not.
PS: even the gain value for the Neumann-like mics did suggest to me @Rja4000 as I remember. In other words, Cosmos APU is almost completely based on the feedback from the field.
 

thin bLue

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Yeah, 48DC power isn't my idea at all, someone in our discord recommended adding it. The same about vinyl ripping. Both these options are nearly free for the Bill Of Materials so, why not.
PS: even the gain value for the Neumann-like mics did suggest to me @Rja4000 as I remember. In other words, Cosmos APU is almost completely based on the feedback from the field.
+Without you, no one in the world can get device like this. Thanks a lot!
 

IVX

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I wonder how difficult it would be to ‘add’ the 48V and variable / adjustable gain to the Cosmos ADC?

So, a high quality two channel audio interface for pro mics and MM/MC cartridges.
That would be easy if you don't care about the distortions, however, in that case, the reason to use so high-performance ADC is disappearing. I have another Cosmos device(Scaler) prepared for production but afraid I'll sell just 100pcs and I doubt releasing that device. There used relays to switch the gain 0..26db + programmable level autorange.
Cosmos_Scaler2.jpg

Cosmos_Scaler1.jpg
 

thin bLue

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I wonder how difficult it would be to ‘add’ the 48V and variable / adjustable gain to the Cosmos ADC?

So, a high quality two channel audio interface for pro mics and MM/MC cartridges.

That would be easy if you don't care about the distortions, however, in that case, the reason to use so high-performance ADC is disappearing. I have another Cosmos device(Scaler) prepared for production but afraid I'll sell just 100pcs and I doubt releasing that device. There used relays to switch the gain 0..26db + programmable level autorange.
View attachment 233686
View attachment 233687
With XLR form factor and L/R separate 48V switch, I'm sure at least over 250 will be sold in short term.
 

thin bLue

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4 XLRs require 2x bigger housing, and >>cost.
Like 48V, the factor make way better accessibility to normal people.
Volume difference at the market will be huge!

Make E1DA popular!
 

DownUnderGazza

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That would be easy if you don't care about the distortions, however, in that case, the reason to use so high-performance ADC is disappearing. I have another Cosmos device(Scaler) prepared for production but afraid I'll sell just 100pcs and I doubt releasing that device. There used relays to switch the gain 0..26db + programmable level autorange.
View attachment 233686
View attachment 233687
Are those TRS inputs and outputs?
If so, then there’s no need for XLR connections.
That could be what I was hoping for.
 
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