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toufu 9th April 2012 08:37 PM

AD1865 vs AD1955
I have built an AD1865 DAC and have been happy with the sound. I am want to try a hires DAC, can anyone comment on the sound quality of AD1865 vs AD1955? Are they similiar in sound? Thanks.

SoNic_real_one 9th April 2012 09:59 PM

Different animals. First is a multibit R-2R type with THD+N of -90dB, the second is "multibit sigma-delta" with THD+N of -110dB. Usually that means there are a few multibits (usually 4-10, they don't say how many here), each modulated by a sigma-delta signal.

On paper the second is definitely better and as proof... it is used in a lot of high-end devices.
Some people say that the pure multibit (like your first one) sounds "better" than a noise-shaped delta-sigma.
To me... it's a close call. I have both types and I listen mainly to a 18 bit multibit too because I think it sounds slightly better while playing CD signals.
But I didn't conduct extensive tests, when I have a hi-res format or a SACD, I am using the sigma-delta.

abraxalito 9th April 2012 11:50 PM

Although I haven't tried the AD1865 I'd predict it will sound more dynamic (jump factor) in NOS than the AD1955 which clearly has noise modulation issues (examine the difference between noise at full-scale and at zero signal).

SoNic_real_one 10th April 2012 12:06 AM

Did you examine those issues? Can you post measurements to show that difference?
I don't own one.

abraxalito 10th April 2012 12:08 AM

Yeah I posted it up on SNA - here's the link to my post: Mutibit vs Delta Sigma (old vs new) - StereoNET Australia - Page 4

SoNic_real_one 10th April 2012 12:51 AM

Ahhh come on...


[#10171] You do not have permission to view this attachment.
From what I read there, the same faults can be found in the multibit cips too. All have a difference between THD+N and SNR, because the first one includes the second plus the THD.

abraxalito 10th April 2012 12:56 AM

2 Attachment(s)
Ok here are the two plots I posted there - I realize now you have to sign up to see them.

What's hidden (because these are FFTs) is any short-term changes in the noise floor. FFT is just showing us the average noise over the acquisition window, but we know that the noise out of an S-D loop is instantaneous level dependent. ESS's Sabre datasheet shows that - the noise varies with DC level.

The noise spectrum is also dependent on the signal level - notice how it slopes upward with zero signal, but ostensibly remains flat with a full-scale sinewave present. Thus we can expect the timbre of the noise to be a dynamic thing.

If you think multibit has the same issue, then post up the plots to show it.

SoNic_real_one 10th April 2012 02:56 AM

At -140..-130dB it is unlikelly to be heard. THD are at -112..115dB and they will cover any noise (the result THD+N is at -110dB).
I don't know, it doesn't make sense. Let's not hijack this topic, maybe we can make another one for this.

abraxalito 10th April 2012 03:05 AM


Originally Posted by SoNic_real_one (
At -140..-130dB it is unlikelly to be heard.

You're making the common misinterpretation of an FFT. The data points represent noise voltage into a very narrow bandwidth - much narrower than the critical bands in the ear.


THD are at -112..115dB and they will cover any noise (the result THD+N is at -110dB).
How do you know?


Let's not hijack this topic, maybe we can make another one for this.
This is germane - the OP is asking for differences in sound between two ADI parts. I hear that the AD1955 is less dynamic and in the absence of any other reasonable hypothesis, I put it down to noise modulation. Those plots are the smoking gun. What more do you want? :D

SoNic_real_one 10th April 2012 03:10 AM

Noise modulation that is not semnificative for the level of audition. Is at the level of air molecules brownian movement.
If it is a difference, it must be something else.

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