[gaboo]

First, I hate to be the bearer of bad news, but 1212m has confirmed ultrasonic rolloff.

Did any of the modders here manage to bypass the DA filter (i.e. get flat ultrasonic freq response)?

 

[yeeyy]

My ears can't hear anything beyond 17kHz, so no big deal for me.

 

[cosmopragma]

My bats won't like that.

 

[Glassman]

it's a well known fact, it's in order for the card to measure better.. removing ultrasonic noise helps keep SNR lower.. but the filter doesn't seem too steep, which is more important.. anyway it's just about 0.2dB at 20kHz, noone can hear that.. the other 0.2-0.3dB is due to the ADC filter so they add up when doing loopback tests..
Iron tried filter bypass but found it actually worse.. one thing you can do is to remove all the little surface mount ceramics from the filter network, this way you remove the filtering without removing the amplification.. try that..

 

[gaboo]

Quote:

Originally Posted by Glassman it's a well known fact, it's in order for the card to measure better.. removing ultrasonic noise helps keep SNR lower.. but the filter doesn't seem too steep, which is more important.. anyway it's just about 0.2dB at 20kHz, noone can hear that.. the other 0.2-0.3dB is due to the ADC filter so they add up when doing loopback tests..

Yes, but it falls off the RMAA chart around 70Khz. I'm not going to transform this into a debate on whether we can hear a rat's ass above 20Khz; you can use the 1212m to test stuff (e.g. amps) above 20Khz. My question is whether bypassing the filter flattens the freq response (without making other things way worse hopefully), so one can use it for testing (and still listen to it)...

Quote:

Iron tried filter bypass but found it actually worse.. one thing you can do is to remove all the little surface mount ceramics from the filter network, this way you remove the filtering without removing the amplification.. try that..

Ok, but what got worse (noise, thd I assume), and how much worse did get? And did the freq respnse get any better?

 

[Glassman]

frequency response shure get better, but then you have lots of HF garbage getting through and affecting the performance of active devices connected to it.. that garbage may well be from say 100kHz to some 6MHz in case of 128x oversampled sigma delta modulators.. what you shure can do is remove just one of the two poles, that will flatten freq response yet filter most of the HF garbage..