Best spec ADC Chip currently.... ??

[lucian]

I never use sine gen, only cosine

alright - why not tan ?

actually - since THD is basically non linearity I could also imagine to do a static calibration of the transfer function. but guess it not really effective.

 

[IVX]

tan doesn't look similar to sine yet..

 

[Schallus]

Hi IVX,

I got the COSMOS ADC yesterday and am very happy with it. Workmanship, THD+N, delivery time and contact with Sunny !!!top notch!!!

I have already measured my DACs and PREs and now I would like to measure my amplifiers.
I have a TPA3255 here, which is a Class-D bridge amplifier with about 25VDC between the outputs and GND. What is the best way to connect it to the ADC? The ADC can handle 43Vrms at the 2.5mm input. But I still have worries about the 25VDC. Because the amplifier and the ADC are connected via ground. Or is this not a problem, because the input signal is divided in the ADC and then finally AC coupled?

43Vrms are possible with the 10Vrms switch setting? Are then in 4.5Vrms switch setting, only 19.35Vrms at the 2.5mm input allowed?

 

[lucian]

Hi IVX,

I got the COSMOS ADC yesterday and am very happy with it. Workmanship, THD+N, delivery time and contact with Sunny !!!top notch!!!

I have already measured my DACs and PREs and now I would like to measure my amplifiers.
I have a TPA3255 here, which is a Class-D bridge amplifier with about 25VDC between the outputs and GND. What is the best way to connect it to the ADC? The ADC can handle 43Vrms at the 2.5mm input. But I still have worries about the 25VDC. Because the amplifier and the ADC are connected via ground. Or is this not a problem, because the input signal is divided in the ADC and then finally AC coupled?

43Vrms are possible with the 10Vrms switch setting? Are then in 4.5Vrms switch setting, only 19.35Vrms at the 2.5mm input allowed?

I put the ADC on a laptop in battery mode. so you have true floating ground. Ofc. the DAC with source signal needs to be on other computer - or connected via optical.

Other option would be to use a DC - DC coupled USB adapter with floating ground.

 

[lucian]

tan doesn't look similar to sine yet..
View attachment 160337

But as you can see - has much more actual information - you just need to translate it to transfer function

 

[IVX]

Hi IVX,

I got the COSMOS ADC yesterday and am very happy with it. Workmanship, THD+N, delivery time and contact with Sunny !!!top notch!!!

I have already measured my DACs and PREs and now I would like to measure my amplifiers.
I have a TPA3255 here, which is a Class-D bridge amplifier with about 25VDC between the outputs and GND. What is the best way to connect it to the ADC? The ADC can handle 43Vrms at the 2.5mm input. But I still have worries about the 25VDC. Because the amplifier and the ADC are connected via ground. Or is this not a problem, because the input signal is divided in the ADC and then finally AC coupled?

43Vrms are possible with the 10Vrms switch setting? Are then in 4.5Vrms switch setting, only 19.35Vrms at the 2.5mm input allowed?

No more than 10VDC is allowed, hence you have to add non-polar caps after your DC-biased amp or as recommended above, use battery-powered laptop.

 

[lucian]

No more than 10VDC is allowed, hence you have to add non-polar caps after your DC-biased amp or as recommended above, use battery-powered laptop.

just to confirm - are the charge / discharge currents for those caps save for the ADC front end?

 

[SylphAudio]

Just received the unit today. Thanks IVX!

I'll pair this with Loxjie d30 for my amp measurements. Bought the DAC because of Amir's review. Another 2 weeks of waiting for me

 

[IVX]

jlesterp, you are welcome. The box looks like came from the burned tank
lucian, not sure if I understand your question but the ADC inputs has some DC bias and for sure should be AC couplet to the XLR inputs.

 

[lucian]

jlesterp, you are welcome. The box looks like came from the burned tank
lucian, not sure if I understand your question but the ADC inputs has some DC bias and for sure should be AC couplet to the XLR inputs.

burned tank !? - didn't hear about that


I don't know the input stage of the ADC, but assume that common GND is referenced against circuit GND ( = shield). The virtual GND of the D_Amp is 50% of Vmax.
So if you connect signals via a capacitor its basically a short between those both GND till the capacitor is fully charged. Just wanted to make sure that this wont impose a problem (especially it the differential input is mapped to single input).

correct me if I am wrong. just burned already my fair share of electronics no being careful of relative potentials.

 

[IVX]

So far I have no even single case of burned input of ADC but the probability to kill that does exist. ESS disclosed the datasheet for ES9822 you can take a look.

 

[lucian]

So far I have no even single case of burned input of ADC but the probability to kill that does exist. ESS disclosed the datasheet for ES9822 you can take a look.

do you have a source? I could not find it - only with request for NDA:

https://ismosys.com/audio-chips/audiophile-adcs/es9822pro/

 

[staticV3]

do you have a source? I could not find it - only with request for NDA:

https://ismosys.com/audio-chips/audiophile-adcs/es9822pro/

Clicking on the 9822 hyperlink on this page will download the datasheet: https://www.esstech.com/products-overview/analog-to-digital-converters/

 

[lucian]

Clicking on the 9822 hyperlink on this page will download the datasheet: https://www.esstech.com/products-overview/analog-to-digital-converters/

thx this worked

 

[lucian]

So far I have no even single case of burned input of ADC but the probability to kill that does exist. ESS disclosed the datasheet for ES9822 you can take a look.

did you implement the reference schematic ? cause here is already decouple capacitors integrated !?


so with assumption of the OPA1612 is sourced by +/- 7.5 V rails:

- max. output OPA ~ 6.9V (-600mV drop)
- max. allowed input in 9822, 4.75V
- Resistor between OPA - 9822 = 36 Ohm -> (6.9V - 4.75V) / 36Ohm = 60mA
- 9822 has ESD protection diodes, but continuous 60mA usually tooo high (didnt find rating in datasheet)

- the input of OPA is protected by series resistance of 2.8k, with a maximum input current of 10mA translates to a max. input voltage of 28V + 7.5V = 35V (without additional resistors taken into account).


-> so putting the OPA into overload (DC Input > ~5 V) could potentially damage the 9822

please correct me if I got something wrong

 

[IVX]

My 9822 inputs have additional clamping diodes protection.

 

[lucian]

My 9822 inputs have additional clamping diodes protection.

good to know. also that the influence is small enough to impair THD.

 

[audiofun]

a few questions to IVX:
- do you plan to support DSD recording in ADC?
- Same question to your unreleased Cosmos DAC. Does it support dsd playback?
- Is the APU single channel or dual? I can't tell it from the rendering. What's the connector?
- APU may work great as a mic pre. but how about phantom power?
- Any plan to make ADC and DAC as one device? If not, how can their clocks sync together?

 

[IVX]

a few questions to IVX:
- do you plan to support DSD recording in ADC?
- Same question to your unreleased Cosmos DAC. Does it support dsd playback?
- Is the APU single channel or dual? I can't tell it from the rendering. What's the connector?
- APU may work great as a mic pre. but how about phantom power?
- Any plan to make ADC and DAC as one device? If not, how can their clocks sync together?

1) no, DSD there made from PCM.
2) yes.
3) single, and today I finished APU modification - LPF is deleted, 48VDC phantom power added. Also, I bought cheap but seems quite typical Rode NT1 to find the optimal gain APU's switch +?db/+60db. 3.5mm jacks.
4) no such plans so far to make ADC/DAC device.

 

[audiofun]

3) single, and today I finished APU modification - LPF is deleted, 48VDC phantom power added. Also, I bought cheap but seems quite typical Rode NT1 to find the optimal gain APU's switch +?db/+60db. 3.5mm jacks.

That is good news. This is the dream device I'm looking for. Looking forward to it!