challenge: record your amplifier voltage and do DeltaWave comparison

[restorer-john]

I'm not sure what settings you are using in Delta wave for display. They are obviously different to mine. I just aligned the same file against itself. But there's definitely a mess in the high end in your spectrum, there is a boost of noise starting before a brickwall and then raised noise after.

 

[pjug]

I'm not sure what settings you are using in Delta wave for display. They are obviously different to mine. I just aligned the same file against itself. But there's definitely a mess in the high end in your spectrum, there is a boost of noise starting before a brickwall and then raised noise after.

View attachment 144743

The low end looks different too. You can buy just the single track if you are interested in really comparing.

 

[pjug]

Click Level EQ and next to it Phase EQ. Close the window. Run your comparison. DW will now correct frequency response errors, and phase errors. Sometimes this will improve the null results considerably..

Checking those settings does seem to help. Now the spectrum of the delta does not have a low frequency hump and the loopback seems to track pretty well. Still, the results are not great for a loopback. Maybe I should upgrade the ACD but I wonder how far I'm going to get with all this. Would you be willing to do a loopback using this track with your equipment to give me an idea how much better is possible? Here are spectrum of delta and zoomed matched waveform plots of my latest loopback run. I'm holding off on more speaker level measurements for now.

 

[pjug]

I am looking at this database of loopback results and the numbers don't look that great. Although I think most were made with DiffMaker instead of DeltaWave so I don't know how they compare.
https://gearspace.com/board/showpost.php?p=14630377&postcount=1922
Is it likely that amp differences (typical cases) would be measurable even if I upgrade my ADC?

 

[Blumlein 88]

I am looking at this database of loopback results and the numbers don't look that great. Although I think most were made with DiffMaker instead of DeltaWave so I don't know how they compare.
https://gearspace.com/board/showpost.php?p=14630377&postcount=1922
Is it likely that amp differences (typical cases) would be measurable even if I upgrade my ADC?

The Diffmaker, Deltawave, and Matlab method (now used instead of Diffmaker) getting the null depth are effectively equivalent. Results with all three will normally be within a db or so of each other. Looking at that database and having done this with a handful of pieces of digital kit are why I think your results at the speaker are pretty good.

 

[pjug]

The Diffmaker, Deltawave, and Matlab method (now used instead of Diffmaker) getting the null depth are effectively equivalent. Results with all three will normally be within a db or so of each other. Looking at that database and having done this with a handful of pieces of digital kit are why I think your results at the speaker are pretty good.

Thanks. The other thing I was wondering is how dependent the results are on the track choice. I assume in this database they use the same track (sorry for being lazy I will go back and read that thread to see Edit: OK they have a track to use so I should check how my ADC compares using their track).

I guess I am ready to give another go at the speaker measurement. I will twist the leads this time. Also make sure voltage into the ADC does not exceed 1.25V. And using your suggested DeltaWave settings. If it seems I am at the limit of what I can do with what I have, I will follow that with a comparison Outlaw M2200 vs Sonos Amp, kind of a decent budget Class AB vs ClassD comparison. Both driving the easy load of the V601.

P.S. Would it be worthwhile comparing the same amp with speaker load vs 8-ohm resistor?

 

[Blumlein 88]

Thanks. The other thing I was wondering is how dependent the results are on the track choice. I assume in this database they use the same track (sorry for being lazy I will go back and read that thread to see Edit: OK they have a track to use so I should check how my ADC compares using their track).

I guess I am ready to give another go at the speaker measurement. I will twist the leads this time. Also make sure voltage into the ADC does not exceed 1.25V. And using your suggested DeltaWave settings. If it seems I am at the limit of what I can do with what I have, I will follow that with a comparison Outlaw M2200 vs Sonos Amp, kind of a decent budget Class AB vs ClassD comparison. Both driving the easy load of the V601.

P.S. Would it be worthwhile comparing the same amp with speaker load vs 8-ohm resistor?

Sounds like a good plan.

Tracks if extreme enough make some difference, but largely most tracks give similar results with Deltawave. Just to see grab a handful of tracks of at least two minutes and record it for each of your upcoming measures and you can see what differences the track does or does not make.

 

[HammerSandwich]

P.S. Would it be worthwhile comparing the same amp with speaker load vs 8-ohm resistor?

Yes!

 

[pjug]

I am happy to say I am getting much better results now. The biggest improvement comes from using the DAC in the UCA202 instead of the Project DAC. I guess because having synchronous DAC and ADC is more important than DAC Sinad for the purposes of this kind of loopback recording. A bonus is that this makes the setup very simple since now I send the UCA202 output straight to the amp (don't do this with a bridged amp though!).

Here are the Behringer UCA202 loopback results:

The M2200 into an 8 ohm resistor (below) is almost as good! (I'm using the 220-ohm/3.3-ohm divider).

M2200 into Usher V601 (below) is also almost as good:

I think I am pretty much doing as good as this equipment can do now, so all I can say here is that the amp seems to drive the speaker as well as a resistor within my measurement limits. My guess is that I will have to upgrade the recording device to have any hope of seeing differences is competent amplifiers. Unfortunately I think my idea of testing the Sonos Amp is sunk because I don't see how I can use the synchronous DAC and ADC without using the crappy Sonos analog input. Instead, I am thinking of upgrading my office amplifier with Icepower or something along those lines. Any suggestions (shoestring budget please)?

I look forward to comments and suggestions on this. I hope we can keep improving and maybe get to my ultimate goal of seeing differences in amplifiers when driving real speakers.

 

[pjug]

A precautionary story I thought I would share...

I thought I would go ahead and do the measurement with the Sonos Amp, using the crappy analog input just to see what I get. I checked continuity of speaker - to RCA - and it was open without power to the amp. Maybe a relay I thought so I powered the amp, played something then turned down the volume. Audible continuity with by meter then sounded. But resistance was not showing zero. Hmmm.

This is where I went stupid and tried going forward anyway. I hooked everything up except the RCA output of the UCA202. Then with very low sound level I plugged this in. Amp shut down immediately. Luckily it seems there was no harm. The UCA202 has optical output so I ordered the adapter for optical input to the Sonos so I can measure it using the UCA202 output and ADC.

Question: Using the UCA202 optical output, will this be in sync with the ADC? I've been thinking that my previous improvement gained by using the UCA202's DAC was from syncing DAC and ADC so that DeltaWave can get better timing matching, but maybe this isn't even true. Any insight that anyone has on this would be greatly appreciated. [edit: is the optical output of the UCA202 putting out from the ADC? I was assuming it put out a direct copy of the source signal? Seems this sinks my idea of going optical from the UCA202 to Pro-ject DAC. Sorry to be so thick headed about some of this stuff. I am not in my comfortable realm here never mind, just improper connection]

Also, anyone know the inner workings of the Sonos Amp, why the - speaker connection is not ground? Pretty sure it isn't a bridged amp.