THD-N
I was thinking of my own PC based THD meter. In this case the SNR is much higher (see: pdf) Suppose the overall (DAC + ADC) SNR is 90dB and you want to bring it down to -150dB, being a reduction of 60dB, you have to average a million cycles. At 1kHz, for example, that means a measurement time of 1000 seconds!
So, at least when sound cards or similar HW stuff are involved, noise becomes really an issue.
Cheers, E.
Hi Scott,
I was thinking of my own PC based THD meter. In this case the SNR is much higher (see: pdf) Suppose the overall (DAC + ADC) SNR is 90dB and you want to bring it down to -150dB, being a reduction of 60dB, you have to average a million cycles. At 1kHz, for example, that means a measurement time of 1000 seconds!
So, at least when sound cards or similar HW stuff are involved, noise becomes really an issue.
Cheers, E.
Hi,
I did provide a ref earlier but no link so...
Here is the abstract:
An analysis of a state variable filter of the kind described by Bonello et al is shown which illustrates the effect the dominant pole in the transfer functions of the operational amplifiers has on stability. Two methods are shown which can substantially null this effect, one of which employs the inherent matching of circuits within an integrated circuit to automatically achieve effective nulling.
And a link:
AES E-Library Low-Cost Alternatives in High-Quality State Variable Filters
/örjan
I did provide a ref earlier but no link so...
Here is the abstract:
An analysis of a state variable filter of the kind described by Bonello et al is shown which illustrates the effect the dominant pole in the transfer functions of the operational amplifiers has on stability. Two methods are shown which can substantially null this effect, one of which employs the inherent matching of circuits within an integrated circuit to automatically achieve effective nulling.
And a link:
AES E-Library Low-Cost Alternatives in High-Quality State Variable Filters
/örjan
THD-N vs THD+N
That's exactly what the manufacture of my sound card did. Not only that, they even accused me of "disparaging" their product when I was complaining on their support forum about a serious (and rather stupid) design flaw. The thread in question has been blocked by now, but here is a <copy>
Distortion is clearly visible and about hundred times higher than normal, while their own THD+N measurements completely hide it due to noise (see the pdf on my previous comment). They consider THD+N an "industry standard", so nothing was wrong.
Curious about the design flaw itself? A 100nF XR5 cap in the signal path !!! In later versions they have replaced that evil cap by a zero Ohm resistor.
(So they knew it was wrong, but didn't have the guts to admit it)
BTW, The L22 (and L44) suffers a few more (less serious) flaws. Nevertheless, it's still the best PCI sound card you can get.
Cheers, E.
Hi Scott,
That's exactly what the manufacture of my sound card did. Not only that, they even accused me of "disparaging" their product when I was complaining on their support forum about a serious (and rather stupid) design flaw. The thread in question has been blocked by now, but here is a <copy>
Distortion is clearly visible and about hundred times higher than normal, while their own THD+N measurements completely hide it due to noise (see the pdf on my previous comment). They consider THD+N an "industry standard", so nothing was wrong.
Curious about the design flaw itself? A 100nF XR5 cap in the signal path !!! In later versions they have replaced that evil cap by a zero Ohm resistor.
(So they knew it was wrong, but didn't have the guts to admit it)
BTW, The L22 (and L44) suffers a few more (less serious) flaws. Nevertheless, it's still the best PCI sound card you can get.
Cheers, E.
I wanted to read this and then include a thank you with any discussion.
But I've been a bit delayed, will read it tomorrow, so thanks in advance.
Best wishes
David
That's evil.
PCI, what's that in 2016?
Anyway, nice to see some screen shots of DiAna.
I have some hopes for the DIY ADC+DAC by Jens.
Maybe a nice combination when they are both available.
Best wishes
David
Hi David,
The interface box however, has to be rebuild.
Perhaps we should collaborate. He is doing the HW and I'm doing the SW.
Cheers, E.
PS: THD+N as a so called industry standard should be outlawed.
And rather stupid, I would say. Even a novice would know that a ceramic XR5 cap in the signal path is a big no-no. The problem here was that a THD+N measurement (also stupid) didn't reveal the error.
I bought them several years ago. Now they are obsolete and replaced by PCI-e versions.PCI, what's that in 2016?
Thanks. Apart from documentation and a manual, DiAna is ready.
The interface box however, has to be rebuild.
Do you mean JensH from Denmark?
Perhaps we should collaborate. He is doing the HW and I'm doing the SW.
Cheers, E.
PS: THD+N as a so called industry standard should be outlawed.
Hi Dimitri,
By "native" I mean something that is not an emulation, e.g. a shell on top of another driver.
Asus with their (overhyped) xonar essence xt did just that, resulting in fikle behavior.
I hope you haven't bought this sound card. For distortion measurements it's entirely unsuitable (too much noise, distortion and spurious sh!t).
An exception is ASIO4ALL (also an emulator), which performs reasonably well.
Cheers, E.
By "native" I mean something that is not an emulation, e.g. a shell on top of another driver.
Asus with their (overhyped) xonar essence xt did just that, resulting in fikle behavior.
I hope you haven't bought this sound card. For distortion measurements it's entirely unsuitable (too much noise, distortion and spurious sh!t).
An exception is ASIO4ALL (also an emulator), which performs reasonably well.
Cheers, E.
That's interesting loop through of their USB device looked good in ARTA.
Hi Edmond,
No, I don't I have lynx-two and I'm thinking to replace it. I couldn't find new card with decent ADC (AKM AK5394A).
Another issue was reported with lynx - high phase noise
No, I don't
I have lynx-two and I'm thinking to replace it. I couldn't find new card with decent ADC (AKM AK5394A).Another issue was reported with lynx - high phase noise
/OT
Hi Dimitri,
Since a Lynx isn't 100% perfect, I also was looking for an alternative and couldn't find one. Regarding distortion, you can nullify it by means of a differential measurement (one before the DUT and one after the DUT).
> decent ADC (AKM AK5394A): The Lynx has already an AK5394A on board, so what's your problem?
Cheers, E.
PS: Sorry guys for the off-topic discussion.
Hi Edmond,
No, I don't
Another issue was reported with lynx - high phase noise
Hi Dimitri,
Since a Lynx isn't 100% perfect, I also was looking for an alternative and couldn't find one. Regarding distortion, you can nullify it by means of a differential measurement (one before the DUT and one after the DUT).
> decent ADC (AKM AK5394A): The Lynx has already an AK5394A on board, so what's your problem?
Cheers, E.
PS: Sorry guys for the off-topic discussion.
/OT
Cheers, E.
Apparently, that was another (USB) audio interface. So I can't comment on it.
Cheers, E.
Do you mean Xonar Essence STX? I don't see an XT unless I'm missing something.
Was the device you had ASIO problems with based on a C-Media chipset?
Hi Chris,
Cheers, E.
I meant ST and STX. Sorry for typo typo and subsequent confusion.
I don't think it had anything to do with that chip. I had issues with initializing the sound card via the ASIO driver. This driver itself simply doesn't comply with the official guidelines from Steinbeck.
Cheers, E.
As far as I know, the ASUS drivers are not completely written from scratch, but modified from C-Media, so it would be interesting to know if other devices using C-Media chips have the same problem with their ASIO drivers.
That only works when everything is perfectly correlated. It usually is not for distortion (never in my experiece). If the distortion contribution is small (-100 dB harmonics) and the loopback is not much better you won't get useful info.
A soundcard with a good source (AK4490?) and an AK5394A is the current best option, which Jens is working on. http://www.diyaudio.com/forums/equipment-tools/277808-diy-audio-analyzer-ak5397-ak5394a-ak4490.html The only commercial products I know of are the Lynx and the EMU "m" series, with its limited DAC.
Who else even uses the CMedia interfaces? The CMedia guys are great to work with but its a really small and slow moving market. They get a lot of the low end USB audio business but not high end, however its hard to justify making a chip for high end audio.