Indeed, the noise floor that I measure is lower than your's. I am still learning how to properly use the interface but what is already clear that I probably need an amplifier/bal-SE converter at the output and attenuator/SE-bal converter for the input to get the best performance out of the unit.
It's a Lynx Hilo, rather expensive if new, but I got a 4 year old used unit last year, which is much cheaper.
I also needed an output amp and an input attenuator to reach the sweet spot, but my soundcard do have these built in so it makes thing a little easier.
Your sound card is in a totally different league than entry level Focusrite 2i2 interface. If you've got it reasonably priced then you are really lucky
Looks not so impressive, but I can't get even that. I can only get 2nd harmonic of the 10kHz signal. For some reason I can't use sample rates beyond 48kHz. Anything higher and the noise floor makes a step down to -200dBFS past 20kHz. So far I can't find the cause of it but I think it can only be software related, hardware itself can't produce such a low noise floor. May be it is a problem of running Windows application on Linux!? I run ARTA on Ubuntu via Wine.
Here are the distortion figures for mine I did a while ago using REW, will have to give steps a try (never used it before). Basically shows similar trend. You can see when doing SE it is a lot worse.
I tried one loopback last night and found same as Oleg, to get NO visible 2nd or 3rd harmonic I had to back off to around -14 to -16 db. I guess this is where notch filters on the output may come in handy?? Or a dedicated very low distortion signal generator.... I haven't had a chance yet to do the proper tests but I have a vague recollection that the performance with the balanced to SE converter feeding back into TR on the input was actually better than the straight balanced loopback.....
Tony.
I tried one loopback last night and found same as Oleg, to get NO visible 2nd or 3rd harmonic I had to back off to around -14 to -16 db. I guess this is where notch filters on the output may come in handy?? Or a dedicated very low distortion signal generator.... I haven't had a chance yet to do the proper tests but I have a vague recollection that the performance with the balanced to SE converter feeding back into TR on the input was actually better than the straight balanced loopback.....
Tony.
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Hi Tony,
I played a bit with my unit and indeed the sweet spot for the generator output is -16dBFS, not more and not less. Playing with the input gain or external amplifier allows to squeeze a bit more out of the unit but not too much. Balanced connection has significant advantage in suppressing mains harmonics in my case. In SE configuration I get a lot of mains harmonics all the way up to around 2kHz. With the balanced connection I don't see them at all.
I started putting together an attenuator for the input. Then I figured out that I may need an amplifier for the output. But now I realise that using extra components like filters, attenuators, amplifiers before and after the 2i2 makes the whole thing more complicated and more expensive than it suppose to be. Once you arrive at 300 Euro (and above) total budget it would probably make sense to consider a more serious tool which has most of it built in. For me Focusrite 2i2 was meant for quick and simple tests to see if I haven't screwed up badly. Serious measurements down to 0.000x% THD figures should be done using other tools but that is not so important for me since so low THD is inaudible anyways, IMO. At the moment I just explore the limits of the 2i2 interface and possible performance improvements with minimal efforts. If, for example, changing output op-amps can prevent such a drastic THD rise with frequency or get down by one digit in the overall THD figures I'll consider it justified intervention. But if it only brings insignificant improvements than I'll stop and will just use the unit as is. The more I search around I see that the real performance limiter is the AD/DA chip itself but I still hope that some reasonable improvement is still possible.
I'll try to figure out how to open the unit and may be will swap output op-amps on one channel and see if it brings any improvements. If it does not I'll leave it at that.
I played a bit with my unit and indeed the sweet spot for the generator output is -16dBFS, not more and not less. Playing with the input gain or external amplifier allows to squeeze a bit more out of the unit but not too much. Balanced connection has significant advantage in suppressing mains harmonics in my case. In SE configuration I get a lot of mains harmonics all the way up to around 2kHz. With the balanced connection I don't see them at all.
I started putting together an attenuator for the input. Then I figured out that I may need an amplifier for the output. But now I realise that using extra components like filters, attenuators, amplifiers before and after the 2i2 makes the whole thing more complicated and more expensive than it suppose to be. Once you arrive at 300 Euro (and above) total budget it would probably make sense to consider a more serious tool which has most of it built in. For me Focusrite 2i2 was meant for quick and simple tests to see if I haven't screwed up badly. Serious measurements down to 0.000x% THD figures should be done using other tools but that is not so important for me since so low THD is inaudible anyways, IMO. At the moment I just explore the limits of the 2i2 interface and possible performance improvements with minimal efforts. If, for example, changing output op-amps can prevent such a drastic THD rise with frequency or get down by one digit in the overall THD figures I'll consider it justified intervention. But if it only brings insignificant improvements than I'll stop and will just use the unit as is. The more I search around I see that the real performance limiter is the AD/DA chip itself but I still hope that some reasonable improvement is still possible.
I'll try to figure out how to open the unit and may be will swap output op-amps on one channel and see if it brings any improvements. If it does not I'll leave it at that.
Hi Oleg, yes I think you are right. I originally bought mine as a portable unit I could use with my laptop for doing speaker measurements. Sure beats lugging a big PC tower around!!
The 2i2 is good for sanity checks and will show you when distortion is higher than the limits of the device, but it won't allow you to show how low the distortion is if it is lower than the 2i2's inherent distortion. For me that's enough (for now)
I did a measurement of my new DAC today and have a spray of 50Hz and it's harmonics much worse than I've had for a while, and I even made up a new cable (which improved things but is still not great. I think I do need an SE to balanced converter as well. I had researched one a while back and decided on a chip, but I can't remember what it was now.
I don't think there is much in the USB space that is high enough spec to do really good measurements, some of the PCI based cards are excellent, and I will probably go that route if I ever decide I want the next step up in measurement capabilities.
The attached is the DAC measurement. 1Khz provided via spdif on a different PC.
Tony.
The 2i2 is good for sanity checks and will show you when distortion is higher than the limits of the device, but it won't allow you to show how low the distortion is if it is lower than the 2i2's inherent distortion. For me that's enough (for now)
I did a measurement of my new DAC today and have a spray of 50Hz and it's harmonics much worse than I've had for a while, and I even made up a new cable (which improved things but is still not great. I think I do need an SE to balanced converter as well. I had researched one a while back and decided on a chip, but I can't remember what it was now.
I don't think there is much in the USB space that is high enough spec to do really good measurements, some of the PCI based cards are excellent, and I will probably go that route if I ever decide I want the next step up in measurement capabilities.
The attached is the DAC measurement. 1Khz provided via spdif on a different PC.
Tony.
Attachments
Using SE connection I get similar looking mains harmonics as you have in your DAC measurements. I'll try bal-SE and SE-bal configuration. This should be relatively easy to try for me since I have most of the parts at hands.
As for the THD measurements I interpret it such that if you can't measure any change in THD compared to the loopback test then the unit you measure has at least one digit lower THD which is really good. Of course it does not allow me taking part in a competition for smallest THD since I can't measure it but I am not able to invest an amount of money which can buy a decent car into the measuring tool just to show off
As for the THD measurements I interpret it such that if you can't measure any change in THD compared to the loopback test then the unit you measure has at least one digit lower THD which is really good. Of course it does not allow me taking part in a competition for smallest THD since I can't measure it but I am not able to invest an amount of money which can buy a decent car into the measuring tool just to show off
yes!! if the HD doesn't change then you know what you are measuring must be better, as it is, your gen 2 has better distortion than my Gen1 and 0.0004 is not too bad! Having listened to the DAC all afternoon, I can say that even 0.01 is not so bad! This is a measurment I did with just the input lead floating (ie unpluged from the DAC but still plugged into the 2i2, it's even worse than when connected to the DAC!!! Interestingly though when connected to the DAC but with DAC powered off, the 50 Hz harmonics pretty much disappeared... The weird thing with that one is the 1Khz as I had no generator running.. My old Audigy 2 ZS also does that, ie shows a 1Khz spike with no signal..... odd....
Tony.
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1kHz spike is strange. I don't see such in my measurements. Picking up mains harmonics with floating cable (basically loaded only by the high input impedance of the interface) is probably normal in nowadays urban conditions. When connected to a DAC the cable (say antenna) gets loaded by the much lower output impedance of the DAC and thus harmonics go down. At least this how I see it.
I haven't ever seen the 1Khz spike with the 2i2 in the past. It was a bit of a surprise, I'm not sure where it came from!! Sorry didn't get a chance to do the comparison measurements, was too excited getting my DAC going I've just been looking at Rod Eliot's site for a SE to balanced circuit Balanced Transmitter and Receiver II
Tony.
I've just been looking at Rod Eliot's site for a SE to balanced circuit Balanced Transmitter and Receiver II Tony.