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TASCAM US-2x2HR loopback Measurments

kipman725

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I recently purchased this interface its a two input two output interface with decent specs. Interesting things I have found so far:
1) Gain on TRS input is lower than XLR so if using this interface with line level signals rather than microphones you need to use TRS to XLR adaptors on the inputs.
2) 'Peak' red light is hard clipping the THD goes up way before this. For Line level signals (+4dBu) this gain control should be set to minimum.
3) outputs are true differential unlike my previous interface

Output tests:

0dBFs, output gain maximum, sine wave 1kHz amplitude: 8.5Vrms = 20.8 dBu:
1640028409029.png

visibly clipped. Rated maximum output level is 20dBu which is met but probobly high distortion at this level.

-3dBFs sine wave 1kHz amplitude: 6.25Vrms =18.1dBu (attenuated digital domain):
1640028584697.png

No clipping visable. I don't have any equipment to measure distortion apart from this interface (unless very bad where the scope FFT will show it or visualy distorted).

Loop-back tests:
For these tests output 1 was connected to input 1 with a TRS -> TRS cable.

4Vrms output with 0dBfs sine wave (input gain set to minimum – Mic/line mode):
1640028743223.png

Noise shaping visable beyond 20kHz.

4V rms output with -3dB digital attenuation (input gain set to minimum – Mic/line mode):
1640028807706.png

No improvement visible, harmonic distortion originates not in DAC but in amplifiers or ADC. THD+N is very similar until 6.7Vrms output whereupon further increases cause harmonic distortion to increase. This is close to the earlier found DAC clip point, we can assume the ADC will not clip with 18dBu input.
 

peniku8

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1) Gain on TRS input is lower than XLR so if using this interface with line level signals rather than microphones you need to use TRS to XLR adaptors on the inputs.
My Fireface does the same thing on the XLR/TRS combo jacks. From the manual:
The two combo jacks also allow for the usage of mono and stereo TRS jacks. The TRS jacks
have a fixed level attenuation of 11 dB. Based on the adjustable amplification from +0 dB up to
+65 dB, the sensitivity is +21 dBu down to –44 dBu, referenced to full scale of the AD-converter.
Therefore the TRS inputs are true full level Line inputs, and the unit can also be used as Line
amplifier.
The distortion at 0dBFS is a bit disappointing, but 8Vrms is quite a lot. 100db SINAD at this price point for a 2x2 is quite nice thou.
Have you fooled around with the stepped loudness measurements yet? It would be interesting to see this interface's curve, since it distorts so heavily at max.
 
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kipman725

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Stepped sine results indicate distortion rapidly increases above -2dBfs with Line out gain on full and input gain at minimum (around 18dBu). Its a small imperfection but its kind of annoying as they could have reduced the maximum output to 18dBu easily and everything else about this interface is good.
 

AnalogSteph

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Going by the 4 Vrms testing, I assume stepped sine results would remain clean up to 0 dBFS if you were to turn down output gain a smidge (like -3 dB)? For kicks, here's a fs/4 90° test tone in steps going up to +3 dBFS as well, which the CS4272 should have a better handle on than chips with built-in ASRC.

I don't get what the fuss is all about when this interface still has pretty much the highest output in its class regardless. iD14 MkII and Minifuse = +12 dBu, SSL 2(+) = +12.5 dBu, UAA Volt = +15 dBu, Scarlett gen3 = +15.5 dBu, MOTU M2 = +16 dBu. You have to be aware that there is ~2 dB worth of excess gain but that in itself is hardly what I would call excessive. (In recording applications aiming for something like -12 dBFS peak is not uncommon, so having a bit more gain available when playing such raw recordings can't hurt.) It may be worth documenting which positions of the level knob give 3 and 6 dB below max.

Analog stage clipping seems to occur shortly above 11 Vp, which would amount to pretty much exactly +20 dBu. Distortion seems fine up to -2 dBFS = -3 dBFS + 1 dB = +19.1 dBu.

BTW, a previous poster noted that getting input gain on input channels 1 and 2 equal was nigh impossible, it would be interesting to know whether that really is this fiddly.
 

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kipman725

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Going by the 4 Vrms testing, I assume stepped sine results would remain clean up to 0 dBFS if you were to turn down output gain a smidge (like -3 dB)? For kicks, here's a fs/4 90° test tone in steps going up to +3 dBFS as well, which the CS4272 should have a better handle on than chips with built-in ASRC.

I don't get what the fuss is all about when this interface still has pretty much the highest output in its class regardless. iD14 MkII and Minifuse = +12 dBu, SSL 2(+) = +12.5 dBu, UAA Volt = +15 dBu, Scarlett gen3 = +15.5 dBu, MOTU M2 = +16 dBu. You have to be aware that there is ~2 dB worth of excess gain but that in itself is hardly what I would call excessive. (In recording applications aiming for something like -12 dBFS peak is not uncommon, so having a bit more gain available when playing such raw recordings can't hurt.) It may be worth documenting which positions of the level knob give 3 and 6 dB below max.

Analog stage clipping seems to occur shortly above 11 Vp, which would amount to pretty much exactly +20 dBu. Distortion seems fine up to -2 dBFS = -3 dBFS + 1 dB = +19.1 dBu.

BTW, a previous poster noted that getting input gain on input channels 1 and 2 equal was nigh impossible, it would be interesting to know whether that really is this fiddly.

I tried your test file, didn't return the same envelope shape but this could be the windows limiter as I used WSAPI playback in foobar and recording in audacity. I am unsure how to record and playback at the same time without modifying the test file?

yes the output is high enough for any use of mine I would just prefer to not have the 2dB excess gain available.

When recording line level signals the input gains should be minimum and under such circumstances the channels match. Dented controls and some kind of scale would be helpful for other signals though.
 
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