Beta Test: Multitone Loopback Analyzer software

[pkane]

So my immediate attempts in Multitone and possibly Deltaawave seem to be giving mixed results, but I'll admit there's a 100% chance of this being user error. I posted my first couple of attempts in here

A/B Testing two audio interfaces

I have two almost identical audio interfaces but one I've modified slightly. How would I go about A/B testing them to see if made a difference? Recording a square wave through both and comparing? Sine wave? Two WAV audio recordings? I'm new to this. Please be gentle lol.

www.audiosciencereview.com

But I genuinely have no idea if I'm doing it properly, I'm still learning and almost certainly am using it wrong. I suspect people more experienced than me understand this right out of the box, but we all start somewhere and I'm keen to learn so I suspect I'll get there eventually I would love to eventually post my results + some modifications for these interfaces as they're worth preventing from going to e-waste due to good driver support. I'm also thinking of socketing mine with an adapter so I can run multiple preamp chips and experiments, but its only really worth it, if I can fully understand the analysis

So for stuff like THD, am I simply looking for the lowest dB value?
SINAD, is that just SNR?
Noise, again just lowest DB?

Frequency response I'll have to learn.

For the comparison, I suggest you use a longer test file, 2-3 minutes. But even with a short one, you should get at least an idea of what's different. If you share the two recordings you already captured through two interfaces in that other thread, I can see what information I can get out of them.

 

[Skezza]

Thanks for your response @pkane really appreciate you taking the time to reply. I'm giving the Sweep THD vs Frequency a go (With some chatGPT assistance to explain some of the terminology

To save you burning your already valuable time, I can generate a new comparison, one a bit longer so the results are more useful.

I've just run a Sweep THD vs Frequency Preset on a non-modified version of the interface.

Going to run across the modified version. I've also got a Toneport UX2 and a KB37 which were marketed as premium products by Line6... yet I've had the Toneport apart and see the same TL072 Be interesting to see if there's an actual sound difference between them.

 

[Skezza]

And just like that, this is a modified version of the interface, where the nearest opamp to the 1/4 jack has been swapped from a TL072 for an OPA1642.

I've found another TL072 on the PCB.... kind of tempted to swap both out. Not sure if it would make a difference though.

 

[pkane]

Thanks for your response @pkane really appreciate you taking the time to reply. I'm giving the Sweep THD vs Frequency a go (With some chatGPT assistance to explain some of the terminology

To save you burning your already valuable time, I can generate a new comparison, one a bit longer so the results are more useful.

I've just run a Sweep THD vs Frequency Preset on a non-modified version of the interface.

View attachment 353073


Going to run across the modified version. I've also got a Toneport UX2 and a KB37 which were marketed as premium products by Line6... yet I've had the Toneport apart and see the same TL072 Be interesting to see if there's an actual sound difference between them.

Are you sure you want to have play gain set to +1.5dB? That will clip the DAC input. 0dBFS is the maximum digital sample value that a DAC can process. I would keep it to 0dBFS, or possibly even 1 or 2 dB below.

 

[Skezza]

Are you sure you want to have play gain set to +1.5dB? That will clip the DAC input. 0dBFS is the maximum digital sample value that a DAC can process. I would keep it to 0dBFS, or possibly even 1 or 2 dB below.

Ahh dang not sure why I bumped that, I'll do it again

Edit: It's worth noting that I'm currently using the headphone jack on the back of the Guitarport and looping back into the 1/4 inch jack. I've not considered whether there's a voltage / impedance mismatch!!

I will run again with this experiment tomorrow but with RCA instead!

 

[Sokel]

Ahh dang not sure why I bumped that, I'll do it again

Edit: It's worth noting that I'm currently using the headphone jack on the back of the Guitarport and looping back into the 1/4 inch jack. I've not considered whether there's a voltage / impedance mismatch!!

I will run again with this experiment tomorrow but with RCA instead!

Copy the yellow ones (or similar near for gain,or different sampling rate ) on the spectrum window before the sweep:

 

[Skezza]

I'll have a go with those settings!!

If the progress bar turns red, I assume it's clipping and I need to drop the gain some more? That might be where I'm going wrong here.

Going to pull out some RCA's nonetheless tomorrow.

 

[pkane]

I'll have a go with those settings!!

If the progress bar turns red, I assume it's clipping and I need to drop the gain some more? That might be where I'm going wrong here.

Going to pull out some RCA's nonetheless tomorrow.

Check just the spectrum view that @Sokel posted, don't jump into doing sweeps until you make sure you have everything set up correctly. Do a single 1000Hz tone capture and see what you get. If there's clipping, you'll see a lot of distortion spikes all over the frequency range. Since you have two digital devices (DAC and ADC) clipping could occur at either one, digital at DAC and analog at ADC input.

 

[Sokel]

I'll have a go with those settings!!

If the progress bar turns red, I assume it's clipping and I need to drop the gain some more? That might be where I'm going wrong here.

Going to pull out some RCA's nonetheless tomorrow.

Red is clipping,yes.
Some ADCs (like mine) don't like high levels,play with the gain a little until you find it;s sweet spot go from -4 to -1db to see,some like even lower.

 

[Skezza]

Thanks for all of your help so far

So this is the unmodified GP

The modified one.

 

[Skezza]

For reference, this is a cheap Aliexpress interface I bought ages ago for no good reason

Edit: Above is invalid.

 

[pkane]

For reference, this is a cheap Aliexpress interface I bought ages ago for no good reason

View attachment 353206

See that red CLIP indicator on the status bar? You’re exceeding the device capability and causing it to clip. You’ll need to adjust the gain and/or test signal levels to get anything meaningful.

 

[Skezza]

See that red CLIP indicator on the status bar? You’re exceeding the device capability and causing it to clip. You’ll need to adjust the gain and/or test signal levels to get anything meaningful.

Dang, I must have missed it when recording. Will do it again!

 

[Skezza]

Cheap Aliexpress version attempt 2:

 

[Rantapossu]

Dang, I must have missed it when recording. Will do it again!

You may want to use a smaller FFT size too, for example 256k, like @Sokel suggested earlier.

 

[Sokel]

Cheap Aliexpress version attempt 2:
View attachment 353211

What exactly are you measuring?What is the devices (name them all,models,etc)

 

[Grooved]

Thanks for all of your help so far

So this is the unmodified GP

View attachment 353203

What Output and Input are you looping here? The L RCA output and the front jack input?

 

[Skezza]

I've just realized there's an Inv flag at the bottom of the GuitarPort due to the 'phase being inverted'...

Is that because I'm using half of a stereo jack cable ? It'll be a mono signal for sure.

@Grooved - I'm currently looping the stereo out back into the front jack. However the cable splits into two 1/4 as it's used in a mixing desk for liver performances. I do have an RCA to 3.5mm and if I dig deep I could probably pull out an RCA to stereo or if i'm lucky mono 1/4 jack from somewhere.

@Sokel, to give you the back story although I'll try and keep it short. I've been using various Line6 audio interfaces for going on 20 years. I still have my original GuitarPort that I purchased in 2003 as a teenager and mixed many tracks on... since then I've evolved to a Toneport UX2, and also own a KB37 which is the same interface + a Midi trigger/keyboard. I'm a guitarist and that's my primary use for these, mixing and recording guitar instrumentals but also backing tracks and other things like that. The drivers are rock solid on these things which is why I've persevered with them for so long.

I know many people are switching to the Focusrite's these days but I've heard a lot of reliability issues with the earlier models and the newer models are still unproven long term, and I'm not willing to slap £170< for an interface that might pack up after a few years. My oldest Line6 interface is 20 years old and still going strong today. Also the latency on these Line6 interfaces is unbelievably low.

So, I've been investigating what modifications you can make to the original GuitarPort etc, to see if I can improve any of the clarity. The opamp by the jack is a TL072. I've got a modified one where I've installed an OPA1642 and was hoping to potentially do further experiments to see what (if any) improvements I could make.

The Aliexpress interface was just a cheap one to run as a soundcard on a machine without one built in.

 

[pkane]

Cheap Aliexpress version attempt 2:
View attachment 353211

Sorry, but something is still clipping. Maybe the ADC input is too hot. What this spectrum represents is a nice square wave, rather than a sine wave with a few distortions. You can see what this really looks like on the Waveform tab and you can use the mouse wheel to zoom in on any portion to see the actual wave form.

 

[Sokel]

I've just realized there's an Inv flag at the bottom of the GuitarPort due to the 'phase being inverted'...

Is that because I'm using half of a stereo jack cable ? It'll be a mono signal for sure.

@Grooved - I'm currently looping the stereo out back into the front jack. However the cable splits into two 1/4 as it's used in a mixing desk for liver performances. I do have an RCA to 3.5mm and if I dig deep I could probably pull out an RCA to stereo or if i'm lucky mono 1/4 jack from somewhere.

@Sokel, to give you the back story although I'll try and keep it short. I've been using various Line6 audio interfaces for going on 20 years. I still have my original GuitarPort that I purchased in 2003 as a teenager and mixed many tracks on... since then I've evolved to a Toneport UX2, and also own a KB37 which is the same interface + a Midi trigger/keyboard. I'm a guitarist and that's my primary use for these, mixing and recording guitar instrumentals but also backing tracks and other things like that. The drivers are rock solid on these things which is why I've persevered with them for so long.

I know many people are switching to the Focusrite's these days but I've heard a lot of reliability issues with the earlier models and the newer models are still unproven long term, and I'm not willing to slap £170< for an interface that might pack up after a few years. My oldest Line6 interface is 20 years old and still going strong today. Also the latency on these Line6 interfaces is unbelievably low.

So, I've been investigating what modifications you can make to the original GuitarPort etc, to see if I can improve any of the clarity. The opamp by the jack is a TL072. I've got a modified one where I've installed an OPA1642 and was hoping to potentially do further experiments to see what (if any) improvements I could make.

The Aliexpress interface was just a cheap one to run as a soundcard on a machine without one built in.

So, is this?


Couldn't find any specs,however TL is good down to -105db THD+N and it's not it's weak link as it seems.

Before you measure:
Kill all gain,in and out (by the knob or any app using it)
Kill all effects and stuff.
If it's input is unbalanced use a short RCA to unbal jack for the loopback.
Use 48000Khz sampling rate as it seems is it's limit.