Analog section performance

Started by warjon, August 26, 2022, 04:21:48 PM

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warjon

I have looked through the measurement section but can't find information on the performance of the UP2 analog section. The reason I'm asking is my current turntable setup is 10m away in another room. The phono stage has a good quality ADC using the AK5572 (see attached data sheet) and I use a balanced SPDIF  cable to the AES/BEU input of the preamp.

The improvement in my analog music was pretty good, but the improvement in my digital was extraordinary over the MiniDSP. This got me wondering if I swapped to using the analog balanced inputs on the UP2 would I get an improvement over the internal ADC in the phono stage. To swap to balanced analog I need to buy the cables and connectors to modify my phono stage so before I go spending $100's $$$ on new cables and connectors I thought I'd the question.

ADC_AK5572_factsheet_v120.png

Tranquility Bass

The AK5572 is a very good ADC. Similar to the AK5394 used in the dScope III measurement analyzer except the 5572 is 32 bit and the 5394 is 24 bits. Probably similar effective number of bits ENOB of 21 bits. Currently the UP2 used a TI chip PCM1863 which is also a 24 bit ADC but probably not quite as good as the AK5572. However it does have a lot of peripheral functions such as programmable gain stages etc and even the ability to run some EQ which is why I was attracted to it after ESS dropped the ES9102.

How are you implementing the inverse RIAA filter ?

warjon

I use this phono preamp, with the ADC inside the case so the only output is the digital XLR.

I cannot use the UP2 phono input because my TT is too far away (10m).

https://audiokarma.org/forums/index.php?threads/ultra-high-spec-opamp-mc-mm-phono-warp-elliptic-filter-line-headphone-amps.937686/


Tranquility Bass

Hi

In the UP2 there is 20dB of analog pre-gain before the signal hits the ADC's. Another 40dB of digital gain is generated by the DSP and the inverse RIAA is also applied in the digital domain. It is possible that the pre-gain could be done external to the UP2 at the cartridge end in a similar way to an antenna masthead amplifier. You could then use a standard balanced cable from the pre-gain amp output and run much longer lengths compared to the standard phono interconnect. Alternatively more amplification could be applied and standard line level input with the appropriate inverse RIAA applied in the DSP. These are just software tweaks. Alternatively one of those standalone phono preamps with EQ/line-level outputs would work as well.

Also one of the main advantages of doing the inverse EQ filters in the DSP is that it allows you to customize any EQ curve you want and indeed the later firmware allows this from the main menu.

https://analog-precision.com/forum/feature-requests/phono-input/msg118/#msg118

cheers
david

warjon

I think I've come up with a solution. I have a Neurochrome Universal Buffer PCB that will easily drive 10m of balanced cable, has excellent specs and will be used in unity gain mode as a line driver from my phono preamp to the analog inputs of the UP2 (NOT the phono input).

I'll report back when I've made the change.