Would you mind sharing details about this ? (Diagram, components) in PM ?
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E1DA Cosmos APU - Teardown and personal thoughts and measurements
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What does APU mean?
IVX
Major Contributor
I forgot to leave the link about Cosmos Scaler proto https://archimago.blogspot.com/2022/11/early-look-e1da-cosmos-scaler-prototype.html
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1. Add Switchable gane range selecter(default, 2nd about +50dB and 3rd about +70 dB) would be really sweet.
2. Add 48V power like APU. It would be killing point again!!!!
3.XLR Cable soldered version make more customer purchase the Scaler. XLR is Tradition quite many people refuse non XLR connections.
IVX
Major Contributor
hm, what about the knob gain control, just replace that for your switches? 
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IVX
Major Contributor
Anyhow you can see that by the knob position, however, the autorange mode is blind.
Nice review. If you sell the Scaler, I will definitely buy it! Having said that, it would have been nice if the APU's 1kHz/10kHz notch switch were 1kHz/No-notch switch. I do not use 10kHz notch, however, the No-notch option will be useful for various measurements such as J-Test, multi-tone signal, etc. The APU can be used as an input buffer for the ADC. My primary issue with Cosmos ADC is low impedance, gain control is only secondly.
Exactly. The race for lowest noise pushed the designers to offer low input impedance ADCs and preamps (Topping …). However, it is not practical at all. Cosmos ADC would need a high impedance, low noise input buffer (FET). This would be a real challenge for the designer. Anyone can use the low impedance BJT opamp. A good anti-alias input filter would be good as well.
@IVX
I have APU plus Cosmos ADC
With 34dB gain setting, I am getting 14V out of the APU preamp output.
Obviously this is too high for Cosmos ADC (10V max input)
What are my options for gain matching? Prefer not to use digital volume control of the DAC because I lose a lot of SINAD dB's this method.
How is everyone tackling this issue ?
I have a DAC with output impednace 2000 ohm that I am trying to measure - obviously not suitable with Cosmos ADC's low input impedance.
APU has 47k ohm input impedance which is great for measuring my DAC
I have APU plus Cosmos ADC
With 34dB gain setting, I am getting 14V out of the APU preamp output.
Obviously this is too high for Cosmos ADC (10V max input)
What are my options for gain matching? Prefer not to use digital volume control of the DAC because I lose a lot of SINAD dB's this method.
How is everyone tackling this issue ?
I have a DAC with output impednace 2000 ohm that I am trying to measure - obviously not suitable with Cosmos ADC's low input impedance.
APU has 47k ohm input impedance which is great for measuring my DAC
This is 100% normal.
60/34dB Gain are supposed to work with either -60dBFS or -34dBFS signals, in intend to measure SNR/DR (not SINAD). That way, you bypass the Noise from the ADC itself.
A Look at ADC Noise Limits and Distortion - Or "How much difference does the Cosmos APU make?" And a look at 2-channel Room EQ Wizard measurements!
A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.
archimago.blogspot.com
Noted thanks.This is 100% normal.
60/34dB Gain are supposed to work with either -60dBFS or -34dBFS signals, in intend to measure SNR/DR (not SINAD). That way, you bypass the Noise from the ADC itself.
A Look at ADC Noise Limits and Distortion - Or "How much difference does the Cosmos APU make?" And a look at 2-channel Room EQ Wizard measurements!
A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.
Confusingly Archimago uses SINAD (he highlights THD+N) to calculate DR
staticV3
Master Contributor
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It indeed should be Noise ("N" in REW RTA).
Well the multitone of DAC + amp is really nice
20 bits of SNR
(without APU of course but this here is APU thread...)
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