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E1DA Cosmos ADC
- Thread starter mansr
- Start date
You can't have lower leakage/RF/AC currents than using a powerbank (as long as you are not charging it from AC at the same time).
That's the reason ivan recommends it multiple times.
I always measure DACs using powerbank for ADCiso and laptop running on battery running REW
Why is that? Powerbank always have an internal DC/DC converter. That they operate in 100kHz’s or MHz may mean less problematic leakage, but is it always lower?
Isn’t it mainly for ground loops?
You cannot have any AC leakage current loop with powerbank
dlovesmusic
Active Member
- Joined
- Feb 24, 2024
- Messages
- 194
- Likes
- 104
Its harder these days to find non PD power banks tho
They will simply deliver the 5V needed. Like my Ugreen and Anker do - they are worldwide. Not hard to find.
a few questions on using a pair of APUs as mic preamps to feed an ADC DM
is the preamp gain defeatable (or reducable)? my incoming mic signal peaks in the range of 0.25V/-10dBu with my current device, a Topping M62 with 2Kohm impedance on the mic inputs.. +36 dB of gain puts me over the 10V max output of the APU im assuming it would run out of voltage and clip?
like a fixed gain of 10 or 20 dBu would be better, or no gain at all
i suppose i could use a scaler inline between the APUs and the ADC but i really dont need the variable gain feature so much
thoughts? the Topping M62 gets me 2x48V phantom with 111 dB of dynamic range/ 0.00023% THD @ at -10 dBu input. ive just been running mic-in with no gain as apart from some sudden gain stage switching around 19 dB of gain it appears to be all digital and offers no advantage.
so im not sure how much an improvement a Cosmos ADC DM would be, esp if i have to add gain to get into its best operating range. the datasheets are kinda cryptical, like the APU says it is max 10V output and has an output impedance of 47 ohms... so im not sure if it would be best to go xlr in or aux in
there are two input ranges listed for each
xlr in is 1.7-5.3V, but then says lowest noise sensitivity at 3V to 9.5V
correspondingly the aux-in is - 20.5-24V and says its more sensitive at 36-43V.
on top of that it says that unbalanced input impedance is 30% less (i thought aux *was* unbalanced ?)
given the lack of any manual or pics of the dip switches i couldn't be more confused as to what levels to expect between an APU and ADC, and how to set the dip switches to match the APU'S max 10V output
absent any gain if i just set the ADC to its most sensitive, 1.7V setting, FSD would be around +7.3 dBu so im like 17dB shy of max headroom and would anticipate a sinad above -110 dB?
adding gain to try to match the range of the ADC is also raising the noise floor so im losing there. Perhaps the M62 is a better fit and im barking up the wrong tree
is the preamp gain defeatable (or reducable)? my incoming mic signal peaks in the range of 0.25V/-10dBu with my current device, a Topping M62 with 2Kohm impedance on the mic inputs.. +36 dB of gain puts me over the 10V max output of the APU im assuming it would run out of voltage and clip?
like a fixed gain of 10 or 20 dBu would be better, or no gain at all
i suppose i could use a scaler inline between the APUs and the ADC but i really dont need the variable gain feature so much
thoughts? the Topping M62 gets me 2x48V phantom with 111 dB of dynamic range/ 0.00023% THD @ at -10 dBu input. ive just been running mic-in with no gain as apart from some sudden gain stage switching around 19 dB of gain it appears to be all digital and offers no advantage.
so im not sure how much an improvement a Cosmos ADC DM would be, esp if i have to add gain to get into its best operating range. the datasheets are kinda cryptical, like the APU says it is max 10V output and has an output impedance of 47 ohms... so im not sure if it would be best to go xlr in or aux in
there are two input ranges listed for each
xlr in is 1.7-5.3V, but then says lowest noise sensitivity at 3V to 9.5V
correspondingly the aux-in is - 20.5-24V and says its more sensitive at 36-43V.
on top of that it says that unbalanced input impedance is 30% less (i thought aux *was* unbalanced ?)
given the lack of any manual or pics of the dip switches i couldn't be more confused as to what levels to expect between an APU and ADC, and how to set the dip switches to match the APU'S max 10V output
absent any gain if i just set the ADC to its most sensitive, 1.7V setting, FSD would be around +7.3 dBu so im like 17dB shy of max headroom and would anticipate a sinad above -110 dB?
adding gain to try to match the range of the ADC is also raising the noise floor so im losing there. Perhaps the M62 is a better fit and im barking up the wrong tree
IVX
Major Contributor
Cosmos APU LNA has 2 fixed gain settings, you can change that only if you are ready to solder/replace some resistors inside.
can you help me identify the resistors and the values i would need for 10 and 20 dB gain?
IVX
Major Contributor
Ok. By default R50 = 200 and R51 = 3.9. A = 1+10000/(R50+R51) = 50 i.e. 34db. You can increase R51 according to your needs.
so if i change R51 to say 4.42 kohm to get to 10 dB gain does the switch on the front then go from +34 / +60 to +10 / ~+18 ?
