Dear Forum,
Good day,
Before purchasing a new audio interface, I would like to ask whether my current sound card, the Focusrite Scarlett Solo 3rd Gen, is suitable for performing T/S parameter measurements using REW.
According to the diagram provided for T/S measurements, it requires one output and two line-level inputs (L/R). The Scarlett Solo has the following configuration:
I would like to ask:
Thank you in advance for your help and for the excellent tool you’ve developed.
Best regards, spyros
Good day,
Before purchasing a new audio interface, I would like to ask whether my current sound card, the Focusrite Scarlett Solo 3rd Gen, is suitable for performing T/S parameter measurements using REW.
According to the diagram provided for T/S measurements, it requires one output and two line-level inputs (L/R). The Scarlett Solo has the following configuration:
- 1 line output (L/R) via RCA
- 1 line/instrument input (TRS)
- 1 microphone input (XLR)
I would like to ask:
- Can this interface be used for T/S measurements in REW with reliable results?
- Is it possible to use the mic input as the second input without enabling phantom power (48V), or would this still affect the accuracy due to different gain structure or impedance?
- If this interface is not sufficient, what are the minimum required specifications for a compatible audio interface for T/S measurements?
Thank you in advance for your help and for the excellent tool you’ve developed.
Best regards, spyros
why "without phantom power"?
just use a cheap USB doc with a separate power plug. that will have enough current draw to power the microphone 48V power.
just use a cheap USB doc with a separate power plug. that will have enough current draw to power the microphone 48V power.
When you switch off the phantom power, the mic input is just an input. The impedance is 3kohm. Too low for electric guitar, everything else does work fine. I used it to input a current probe.
Best regards, Bernd
Best regards, Bernd
Output impedance is rather high, you can use a low output impedance buffer amplifier or the headphone output instead and it helps.
The XLR on these units are combo types, aren’t they? On my interfaces three out of three have those.
[Edit] No, obviously not. That is a strange choice Focusrite made.
[Edit] No, obviously not. That is a strange choice Focusrite made.
Yes, kind of.
But you are better off with a 2i2.
For time domain/phase measurements accurately, you need a timing reference, which that is a good solution for.
I DIdn't notice the question was about a solo. My comment was about the 2i2.
You need 2 channels of input and one of output to make T/S measurements. The problem with high output impedance is that the jig won't calibrate with a low ohm resistor and it won't necessarily be as accurate with a high ohm resistor. Mine won't calibrate with 10 ohms and it will "roughly" calibrate with the headphone output.
You need two inputs to make frequency response measurements with a timing reference as well. The solo won't work for this, AFAIK.
You need 2 channels of input and one of output to make T/S measurements. The problem with high output impedance is that the jig won't calibrate with a low ohm resistor and it won't necessarily be as accurate with a high ohm resistor. Mine won't calibrate with 10 ohms and it will "roughly" calibrate with the headphone output.
You need two inputs to make frequency response measurements with a timing reference as well. The solo won't work for this, AFAIK.
Because it doesn’t have fixed Line-level inputs you need to be careful to match the gains of the MIC and INST inputs. Assuming you can match the gains (e.g. via Loopback for each input) it should work, but you need to check every time since your accuracy depends on relative positive of volume knobs.
I would use Headphone out as a signal source since it is better suited to drive the range of impedance of a speaker.
I would use Headphone out as a signal source since it is better suited to drive the range of impedance of a speaker.
Dear Forum,
Thank you very much for your helpful answers and the time you took to respond to my question. I truly appreciate your support.
Based on your advice and what I found through further research, I decided to purchase a used MOTU M2, which seems to be a good match for what I need.
Thanks again for your help!
Best regards,
Spyros
Thank you very much for your helpful answers and the time you took to respond to my question. I truly appreciate your support.
Based on your advice and what I found through further research, I decided to purchase a used MOTU M2, which seems to be a good match for what I need.
Thanks again for your help!
Best regards,
Spyros
It has two inputs and is just fine for that. The impedance thing is a bit fiddly, matching the channels. But that also should work. Best to use a separate amp (I presume everyone has one or more lying around…) as you need low impedance output indeed.
If you are to use your interface for impedance measurements often and plan on doing dual-channel measurements, I would strongly recommend stepping up to the M4. It has fixed-level line inputs/outputs which save you time over the long because you have no level adjustment to do for impedance measurements.
@markbakk regarding the need for a low output impedance : My understanding is/was that since one input channel of the sound card monitors the sound card headphone output, the effect the output impedance (or FR variations with frequency) should be canceled out. Please let me know if I’m missing something here.
