Focusrite Clarett 2Pre USB - quick measurements

[waterproofbeanie]

Has anyone measured the headphone output of these? I'm debating between Clarett 2Pre and Scarlett 4i4 - the difference in microphone quality isn't really a dealbreaker for me, but if the Clarett means I don't need an external headphone amp that would be perfect. Amir's measurements (and Julian's) of the Scarlett 2i2 headphone output is pretty horrifying :O

 

[Panelhead]

I have the 4Pre. It has two headphone amps. Both seem fine. But not a headphone listener.
The overall quality of the Clarett line is better than the Scarlett products. Look at the specs. And Focusrite has a corporate policy of selling products that exceed the published specs. The specs are a minimum level of performance.

 

[RayDunzl]

Has anyone measured the headphone output of these?

Headphone 1 out on a Focusrite Clarett 4Pre USB

PC REW -> USB -> Clarett DAC -> Headphone 1 analog out via TRS to input 7 -> ADC -> USB -> REW

Measurements not guaranteed...

4.6V out (maximum), 15.5dBu

Distortion

Impulse and Step

50mv RTA

1V RTA - would be 105dB on HD650 headphones

Conclusion:

Looks "good enough".

 

[Bamboszek]

These measurements looks fine, but line input impedance is probably 10kΩ or higher. With typical headphone load such as 32Ω it might look substantially worse. Another important thing what is missing is maximum power and output impedance.

 

[RayDunzl]

These measurements looks fine, but line input impedance is probably 10kΩ or higher. With typical headphone load such as 32Ω it might look substantially worse. Another important thing what is missing is maximum power and output impedance.

I saw over 4 volts indicated, and the output impedance is unspecified.

15dBu = 4.35V

My phones are 300 ohm.

 

[Nemx]

I still can't understand why they're hiding the headphones output impedance on the Clarett line, since they declare it on the Scarlett, that's a lower series... With low impedance headphones it's a deal breaker (I use 55 ohm hph at the moment). Is there any way to measure it?

 

[Bamboszek]

To measure output impedance you will need simple voltmeter and about 16-100Ω resistor.
Cheap DMM are accurate only at about 50 or 60Hz. Generate test tone in that frequency using REW for example.
Dial volume to obtain 2V or so at headphone output. Now connect known resistance to headphone output, don't change volume and again measure output voltage.

Zout = ( (V - Vload) * Rload ) / Vload

With near zero output impedance V should be nearly equal to Vload. Keep cables short, long can affect measurements with 0-2 ohms.

 

[RayDunzl]

I still can't understand why they're hiding the headphones output impedance on the Clarett line, since they declare it on the Scarlett, that's a lower series...

I found someone who say it is 7 ohms.

Focusrite says "you can generally assume less than 12 ohms" in a general statement in one of their general FAQs.

 

[Nemx]

Thank you for your answers! Yes I found the 7ohm value too, I was hoping for an official statement from Focusrite.
I got a reply from their CS and they say "10R, 5R for each side". I can't really understand that, is it R for resistance and they imply ohms? I see that they used the R in the THD and max volume output too (and it was 100R).

 

[Bamboszek]

Engineers are lazy. There is no Ω on keyboard so it is usual to see 100R = 100Ω, 0R22 = 0.22Ω, 1k = 1000Ω, 1M5 = 1500000Ω and etc.
I'm not sure what they mean. 5R for each side makes only sense for balanced outputs. Maybe 5R for each stereo side? But that doesn't makes sense.

 

[Nemx]

Engineers are lazy. There is no Ω on keyboard so it is usual to see 100R = 100Ω, 0R22 = 0.22Ω, 1k = 1000Ω, 1M5 = 1500000Ω and etc.
I'm not sure what they mean. 5R for each side makes only sense for balanced outputs. Maybe 5R for each stereo side? But that doesn't makes sense.

I'm sorry I forgot to specify I asked them about the 4pre. I assumed they share components, but I'm now seeing that the 2pre has only one headphones output, when the 4pre and 8pre both have two outputs (I read on a russian website that there's a second DAC feeding the second headphone output).
Could this be related to the "sides"?

 

[Bamboszek]

Still don't makes sense. Only reasonable way I could imagine about output impedance with "sides" is series resistor at balanced output - 5R at hot and 5R cold would mean 10R balanced output impedance. But headphone outs are unbalanced / single ended or whatever we want to call them.

 

[Nemx]

If it's not one amplifier into two outs (I read somewhere that it's common to have one main out and then a resistor for each physical output, right?), could it be that they consider each output as two channels? In their Control software you can have 10 different outputs for the 4pre (4line, 2 s/pdif, 4 headphones). I'll ask back the CS.

 

[ehabheikal]

Up until recently I was using the Digilent Analog Discovery 2 to perform audio measurements on my DIY audio projects - with 14-bits of resolution, it's a surprisingly powerful and cost effective little device. And while still an exceptional and blisteringly fast scope - I honestly can't see myself using a "traditional" oscilloscope when these insane USB devices exist! - the bottleneck is the noise floor, which doesn't get much lower than around -80dB. So while I could verify that my projects were relatively clean, I couldn't really plumb the depths of their noise characteristics.

I recently picked up the Clarett 2Pre to take over FFT/spectrum duties, freeing up the Analog Discovery as a full-time scope (and logic analyser) and giving me much more dynamic range to test out designs.

Apart from the abysmal software - "Focusrite Control" - I couldn't be happier. Great build quality, and effortless to integrate into my setup. My chain is as follows:

​

DUT -> Dummy Load -> Passive Attenuator -> Clarett 2Pre​

While I'm still fairly new to best practices regarding sound interfaces and loopback measurements, here are some quick results:

Setup

• Balanced 1/4" to balanced 1/4" cable from Line Out 3 to Input 1
• Focusrite Control set to Direct Routing (the only way I could find to prevent a feedback loop - still getting to grips with the software)
• Line Output at -6dB in Focusrite Control
• Input pot at 10-o-clock
• Mono only - didn't have a second cable on hand

REW @ -6dBFS 1KHz sine:

View attachment 43810

That third harmonic hops around a little, somewhat larger than I'd like. Although massive nitpicking (it's ~125dB down!).

And for what it's worth, RMAA:

View attachment 43811

View attachment 43812

View attachment 43813

Very happy with the results! Not quite the rock-bottom distortion figures seen elsewhere in the Clarett range (I've seen -116dB noise figures), but an absolutely razor sharp frequency response. Lovely.

If anyone has any tips about how best to perform loopback tests, software choices, setup (particularly the godawful Focusrite Control software) I'd appreciate it!

i am thinking of this as dac
does the spdif work with normal stereo spdif inputs?
if i set spdif and usb inputs to be permenantly mixed so that whichever source connected runs would it keep doing mixing even if pc is not connected?

 

[dfuller]

Looks like Julian Krause got his hands on one. Headphone out is nothing amazing (quite decent at 300R overall though not SOTA or anything), but the distortion performance and crosstalk is kinda crap at low impedance.

His measurements circled.

 

[waterproofbeanie]

Looks like Julian Krause got his hands on one. Headphone out is nothing amazing (quite decent at 300R overall though not SOTA or anything), but the distortion performance and crosstalk is kinda crap at low impedance.

His measurements circled.

Glad I didn't buy one as a standalone dac/amp then! I like being able to drive any headphone, not just my high impedance ones.

 

[paulraphael]

Hi, this is my first post. I have the Clarett 2pre and recently got some unpublished specs from Focusrite (after some tooth-pulling):


Mic input (AIR off) = 6.2KΩ

Mic Input (AIR on) = 2kΩ

Line input (balanced tip-ring) = 66kΩ

Line input (unbalanced tip-screen) = 33kΩ

Instrument DI inputs = 2.3MΩ

All line outs = 136R balanced (68Ω each phase)

All headphone outs = 10Ω total (5Ω per side)

Output Voltage: +16 dBu


I have a few takeaways and and some questions.

1. The engineers' shorthand for unites is confusing (2k2 vs. 2k0??). I wrote back for clarification, but maybe this makes sense to everyone here.
(I edited the units after clarification from Focsrite )
2. It looks like the AIR feature (which I've never used) is more than EQ. It also changes the input impedance. It's a failure of their marketing that they don't tell us this.
3. They give headphone output impedance per-side and and a combined. I don't see anyone else doing this, so it's unclear which number to compare to everyone else's. I'm hoping it's the per-side number.

I do like the way this thing sounds. Transparent as far as I can tell. I use it for casual recording and for serious listening, lately mostly with headphones. I use easy-to-drive Philips X2HR headphones (32 ohm).

The Clarett had a harder time than expected driving 250 ohm Beyerdynamic 1170 pro headphones. Focusrite says the amp is good to 600 ohms, and 16dbu sounds like a lot of juice, but I really had to crank the volume nearly all the way for acceptable output levels with these cans, even on some commercial recordings. Fortunately I didn't like these headphones for other reasons.

 

[Blumlein 88]

2k0 and 2k2 would be 2000 ohms and 2200 ohms.

I'd seen somewhere the Air setting changes impedance as well as EQ's the upper mids and treble.

I'm puzzled on the headphone out.

 

[trl]

The Clarett had a harder time than expected driving 250 ohm Beyerdynamic 1170 pro headphones. Focusrite says the amp is good to 600 ohms, and 16dbu sounds like a lot of juice, but I really had to crank the volume nearly all the way for acceptable output levels with these cans, even on some commercial recordings. Fortunately I didn't like these headphones for other reasons.

Come on, almost 5 V RMS @ 600 Ohms is quite a decent value for an audio interface headamp. Motu M4 has a 7 times lower value. After all, these are studio interface, so headamp should be used, mostly, with monitor cans, not with high impedance or planars.

Clarett 2Pre - 4.8V RMS driving 600 Ohms resistive load, so about 38 mW​

 

[trl]

Looks like Julian Krause got his hands on one. Headphone out is nothing amazing (quite decent at 300R overall though not SOTA or anything), but the distortion performance and crosstalk is kinda crap at low impedance.

His measurements circled.

Motu M4 driving 40 Ohms Hifiman HE-560 at 1 V RMS

Motu M4 driving 40 Ohms Hifiman HE-560 at 2 V RMS
​

Clarett 2Pre driving 40 Ohms Hifiman HE-560 at 1 V RMS​

Clarett 2Pre driving 40 Ohms Hifiman HE-560 at 2 V RMS​

​

It's way better than the Motu M4 with these HE560 planars, even if at 2 V RMS distortions are clearly visible.

Not sure how Julien did those measurements, but RMAA tells us something different. However, at 1 V RMS the headamp really shines, so nothing to worry about, not even up to 4 V RMS if driving 300 Ohms load.

Later Edit: Without intention, I uploaded the Motu M4 headamp pics; now I've added the ones for Clarett 2Pre. I will not delete the M4 pics, in case someone might care to watch and compare.