TEAC NT 503 or UD-503: Opinions?

[Eluxe]

Hello,

 

This is my first post and I am sorry if this has already been answered but here is my question :

Does the upsampling, digital filtering etc is done by the AK4490 chip or is it done by a DSP chip with TEAC algorithm ?

 

By that I mean :

- If I turn off the upconverting on the TEAC, does it bypass the TEAC DSP chip and send NOS signal to the AK4490 which will upsample ? Or is it a complete NOS signal which will be converted in Analogue ?

- If I turn off Digital Filter on the TEAC, does it bypass the proprietary TEAC filter and use a preconfigure filter of the AK4490 ? Or will it turns the AK4490 in External Digital Filter mode and bypass all digital filter in order to use HQplayer filter ?

 

In summary I want to know if I can send a PCM signal upsampled and filtered with HQplayer and bypass everything until the delta-signal modulator ?

 

Thank you very much in advance !

[Eluxe]

Hello Jay-dub and thank you very much for your very informative reply !

 

The "Digital filter" options select settings of the AK4490;

I tend to believe the same thing as the filters looks like the same to the ones proposed on the AK4490 (with one missing : the super slow roll-off). But how can you be sure ? Also I thought upsampling and digital filter go together ..? I thought the upsampling and DG filter was maybe performed by the FPGA chip and the DAC is runing in EXTERNAL DF mode ..?

 

the "Upconversion" options select a separate DSP. Whether that DSP is a solution implemented by TEAC or an off-the-shelf chip that they incorporated into the 503 isn't clear.

On the website I found that it is a FPGA chip programmed by TEAC.

 

When you send PCM at 352/384 kHz, the PCM filters on the separate DSP are bypassed, as are those on the 4490. As long as you don't select DSD upconversion, the settings don't matter; the DSP will do nothing, and the 4490 will only do DS modulation followed by the 150kHz switched-capacitor.

Agree with that, but is there a difference between : a)passing through the interpolator of the AK4490 but with no processing when sending in x8 PCM and in standard mode. Or b) having the chip in External DF Mode and going directly to the DS modulator, bypassing the interpolator ... ?

 

I must ask, if you're using HQPlayer, why you want to use it to upsample to PCM instead of DSD. The latter option eliminates aliasing around 352/384 kHz and multiples, bypasses the modulator on the 4490 and gives the option of higher-performance DS modulators, and allows you to select between two switched-capacitor lowpass filters. There's no downside, if your computer can handle it.

I will probably ending doing that. I am not currently using HQplayer, but get curious about all the DSD stuff and want to try by myself every configuration possible and maybe do some measurement also... It is more for curiousity than for pure SQ. Also how can you be sure that the DAC run in real bypass mode (volume and DS modulator) and not in Normal Path ??

 

There is so much uncertainty on how everything is handle by TEAC inside that I might go for a DIY or boutique solution based on AK4490 (as Mirand Audio DAC or KLEIN DAC II) as I can be sure of the mode the DAC is really running with those ... Too bad because the TEAC seemed to be a really versatile device.

 

(Please refer to the AK4490 diagram to understand what I am saying : https://www.akm.com/akm/en/file/datasheet/AK4490EQ.pdf)