While waiting for my Motu M4 interface to arrive from Thomann, I was puzzled by a change in the estimated time delivery for the new orders on this product. As my ETA was estimated initially to about 5 weeks, when I saw that for the new orders the ETA changed to 12-17 weeks, I thought that my order will be affected too, so I told Thomann that I want to cancel my order, then I purchased an used Clarett 2Pre USB instead. However, Thomann told me that my order is on a different batch, so I should be able to receive it in a week or so, so I haven’t cancelled in the end, so now I have both M4 and Clarett 2Pre. 
This Clarett had an issue with analogue #2 input, its gain being exactly 8 dB lower than stated on the specs, so mics like AKG D5 or Shure SM7B could not be used with that input. I sent it in RMA and the authorized seller was able to resolve it (apparently potentiometer or the plug from pot's cables was not perfectly soldered on the board).
However, manufacturer full specs can be found here: https://focusrite.com/en/usb-c-audio-interface/clarett-usb/clarett-2pre-usb and datasheet here https://fael-downloads-prod.focusri...oads/32407/clarett-2preusb-user-guidev1.2.pdf. Below a screenshot from the datasheet with the performance specs:
The Focusrite Control, the actual control panel from where we can choose how to route audio signals between inputs and outputs, is explained in detail here: https://support.focusrite.com/hc/en-gb/articles/115004431669. It is rather hard to understand all the features in few minutes, but after playing around a bit things got easier to catch.
The interface is very well built, the aluminum case is very thick (like 2-2.5mm) and heavy, it could be used as heatsink for power-amp transistors. The look is similar with other Focusrite interfaces, just a bit more shiny-red. Front XLR mic plugs are made by Amphenol and the mics are a bit hard to plug, but the final connection is sturdy and there's no way to unplug a mic without using both hands (actually this is a Pro not a Con, as we don't want mics to have a lose connection with the interface).
Hard to disassemble, but totally worth the challenge and time spent, as the shiny case is hiding three boards with complex electronics inside.
Clarett 2Pre main board, bottom view
Clarett 2Pre main board, top view
USB and TOSLINK/ADAT transport card is build around couple of XMOS chips marked as XFR002C and XFR001C. They’re powered by dedicated power regulators across the same transport board.
USB transport board - top view
The +12 V coming from the external power brick gets lowered to +5 V and to +3.3 V via NCP3170 PWM switching converters. Digital components are using these low-voltage power rails, but also relays too, while the analogue audio chips are expecting a higher voltage.
NCP3170 buck converters
Few M3425 3A boost converters have been seen on the main board. These are boosting existing +5V rail to a higher voltage to power the audio circuitry, so the output power to be higher. This way the built-in headphones amplifier will be able to drive more headphones. For example, the dual opamps from the board (JRC 4556/5532/8065, OPA 2141) are power by +/-9.5 V rails, so a total of about 19 V RMS, even if the audio interface is only powered from the USB + 5 V. However, if the USB port where Clarett is connected is unable to sustain 3 A (a total output power of 15 W), then a LED will blink, making impossible the usage of the interface without the external power adapter.
Main board capacitors
The DAC chip inside is an AKM AK4413EQ 120dB S/N, 24-Bit 192kHz 4ch DAC, a rather obsolete part these days, not to be used for new designs, but still with a respectable THD+N of -104 dB.
The ADC chip is an AKM AK5388AEQ, 120dB S/N, 24-bit 192kHz 4ch ADC, obsolete part as well, but with a very good THD+N of -100 dB.
ADC and DAC chips
ADC inputs seem to be buffered by NJM8065 dual opamps, while DAC outputs seem to be buffered by JRC5532 opamps, probably one dual opamp for each ADC input and for each TRS output as well.
Analogue inputs gain is done by couple of THAT 1583 chip, a Low-Noise Differential Audio Preamplifier, able to deliver a 60 dB gain with only -128.9dBu (1.9 nV/√Hz) EIN of noise. Its THD+N is 0.0006% @ 0 dB gain, 0.001% @ 40 dB gain and 0.006% @ 60 dB gain, respectable figures for an analogue input of a home studio interface.
Two such THAT 1583 chips are controlling the gain for the two analogue inputs
A similar THAT preamp is also used inside the Motu M4, the THAT 6263. A quick compare of THAT preamps can be found below:
THAT digitally controlled preamps
The built-in headphones amplifier is powerful enough for a studio interface, definitely more powerful than Focusrite Solo Gen3 or Motu M4. It is based on the Japanese operation amplifier NJM4556AL, same as used as output buffer in Objective 2 headamp (just one single opamp, not couple of them, like in Objective 2). Theoretically, according to the datasheet, powered at +/-9.5 V it should be able to push up to 5.3 V RMS into high impedance headphones, approaching it’s 70 mA current limitations when pushed to low impedance cans. I was able to listen comfortable to my 40 Ohms Hifiman HE-560 planar headphones, which was not possible with Motu M4 due to the distortion when pushing up the volume, so there's enough juice on the 6.3 mm jack.
I was using 120 dB 16 Ohms sensitive IEMs and the background noise was there, but very low intensity, about the same as on Motu M4, totally not interfering with the music or audio tracks playing. The power before clipping on headphones would be about:
Clarett headamp - 4.7 V / 600 Ohms (pretty much as advertised by manufacturer: +16 dBu, which means 4.88 V RMS)
Clarett headamp - 2.45 V / 30 Ohms (top half clipping, but dropping voltage to 2.3-2.35 V makes the sine perfect again)
I can spot on the board one OPA2141 dual opamp followed by couple of JRC8065 opamps, but unfortunately I am not sure what they do, although I have a feeling that the two JRC8065 are summing up two balanced channels into two single-ended ones, then the OPA2141 might act as a gain stage for the JRC4556 headphones buffer, but I’m unable to prove that, as the PCB is quite opaque. However, this OPA2141 is the best performer from all opamps from the board, just not sure what is its purpose on the board.
The front panel/board has LEDs and potentiometers. I can spot three HC595AG 8−Bit Serial Shift Register with Latched 3−State Outputs. most likely to control the front lights, based on device state (INST, AIR, 48V etc.). I’ve also seen at least three more such shift registers on the main board.
Frontal board, with potentiometers and controls
The four potentiometers from this board are very similar with ALPHA RD902F-40-00D series, the one from headphone being probably logarithmic, while the other three probably being linear carbon tapers. Some Focusrite users seem to have troubles with such pots, same applies to ASUS Essence One users that are sharing similar APLHA pots, but time will tell how long will resist. One thing’s for sure, replacing them is quite difficult, because it involves a complicated way to dismantle the device, get out the boards and to then to unsolder double-sided soldered pins. Hope I’ll never have issues with these pots.
Frontal board, with potentiometers and controls
L.E.: Worth adding that the only analogue volume control is for the headphones output, while the other three potentiometers (for gain and master volume) are all digitally controlled.
This Clarett had an issue with analogue #2 input, its gain being exactly 8 dB lower than stated on the specs, so mics like AKG D5 or Shure SM7B could not be used with that input. I sent it in RMA and the authorized seller was able to resolve it (apparently potentiometer or the plug from pot's cables was not perfectly soldered on the board).
However, manufacturer full specs can be found here: https://focusrite.com/en/usb-c-audio-interface/clarett-usb/clarett-2pre-usb and datasheet here https://fael-downloads-prod.focusri...oads/32407/clarett-2preusb-user-guidev1.2.pdf. Below a screenshot from the datasheet with the performance specs:
The Focusrite Control, the actual control panel from where we can choose how to route audio signals between inputs and outputs, is explained in detail here: https://support.focusrite.com/hc/en-gb/articles/115004431669. It is rather hard to understand all the features in few minutes, but after playing around a bit things got easier to catch.
The interface is very well built, the aluminum case is very thick (like 2-2.5mm) and heavy, it could be used as heatsink for power-amp transistors. The look is similar with other Focusrite interfaces, just a bit more shiny-red. Front XLR mic plugs are made by Amphenol and the mics are a bit hard to plug, but the final connection is sturdy and there's no way to unplug a mic without using both hands (actually this is a Pro not a Con, as we don't want mics to have a lose connection with the interface).
Hard to disassemble, but totally worth the challenge and time spent, as the shiny case is hiding three boards with complex electronics inside.
Clarett 2Pre main board, bottom view
Clarett 2Pre main board, top view
USB transport board - top view
The +12 V coming from the external power brick gets lowered to +5 V and to +3.3 V via NCP3170 PWM switching converters. Digital components are using these low-voltage power rails, but also relays too, while the analogue audio chips are expecting a higher voltage.
NCP3170 buck converters
Few M3425 3A boost converters have been seen on the main board. These are boosting existing +5V rail to a higher voltage to power the audio circuitry, so the output power to be higher. This way the built-in headphones amplifier will be able to drive more headphones. For example, the dual opamps from the board (JRC 4556/5532/8065, OPA 2141) are power by +/-9.5 V rails, so a total of about 19 V RMS, even if the audio interface is only powered from the USB + 5 V. However, if the USB port where Clarett is connected is unable to sustain 3 A (a total output power of 15 W), then a LED will blink, making impossible the usage of the interface without the external power adapter.
MP3425 boost converter
Electrolytic capacitors used on the board are mostly CapXon KM series series, Jamicon SS and Jamicon SK series, but also few Nichicon PM series too. Temperature inside the Clarett is not high at all, the outer case is barely warm after hours of continuous operation, so caps temperature rating should not matter here.
Main board capacitors
The DAC chip inside is an AKM AK4413EQ 120dB S/N, 24-Bit 192kHz 4ch DAC, a rather obsolete part these days, not to be used for new designs, but still with a respectable THD+N of -104 dB.
The ADC chip is an AKM AK5388AEQ, 120dB S/N, 24-bit 192kHz 4ch ADC, obsolete part as well, but with a very good THD+N of -100 dB.
ADC and DAC chips
ADC inputs seem to be buffered by NJM8065 dual opamps, while DAC outputs seem to be buffered by JRC5532 opamps, probably one dual opamp for each ADC input and for each TRS output as well.
Analogue inputs gain is done by couple of THAT 1583 chip, a Low-Noise Differential Audio Preamplifier, able to deliver a 60 dB gain with only -128.9dBu (1.9 nV/√Hz) EIN of noise. Its THD+N is 0.0006% @ 0 dB gain, 0.001% @ 40 dB gain and 0.006% @ 60 dB gain, respectable figures for an analogue input of a home studio interface.
Two such THAT 1583 chips are controlling the gain for the two analogue inputs
A similar THAT preamp is also used inside the Motu M4, the THAT 6263. A quick compare of THAT preamps can be found below:
THAT digitally controlled preamps
The built-in headphones amplifier is powerful enough for a studio interface, definitely more powerful than Focusrite Solo Gen3 or Motu M4. It is based on the Japanese operation amplifier NJM4556AL, same as used as output buffer in Objective 2 headamp (just one single opamp, not couple of them, like in Objective 2). Theoretically, according to the datasheet, powered at +/-9.5 V it should be able to push up to 5.3 V RMS into high impedance headphones, approaching it’s 70 mA current limitations when pushed to low impedance cans. I was able to listen comfortable to my 40 Ohms Hifiman HE-560 planar headphones, which was not possible with Motu M4 due to the distortion when pushing up the volume, so there's enough juice on the 6.3 mm jack.
I was using 120 dB 16 Ohms sensitive IEMs and the background noise was there, but very low intensity, about the same as on Motu M4, totally not interfering with the music or audio tracks playing. The power before clipping on headphones would be about:
- 180 mW / 30 Ohms (about 7 times higher than the M4)
- 210 mW / 40 Ohms
- 200 mW / 100 Ohms
- 75 mW / 300 Ohms
- 38 mW / 600 Ohms.
Clarett headamp - 4.7 V / 600 Ohms (pretty much as advertised by manufacturer: +16 dBu, which means 4.88 V RMS)
Clarett headamp - 2.45 V / 30 Ohms (top half clipping, but dropping voltage to 2.3-2.35 V makes the sine perfect again)
I can spot on the board one OPA2141 dual opamp followed by couple of JRC8065 opamps, but unfortunately I am not sure what they do, although I have a feeling that the two JRC8065 are summing up two balanced channels into two single-ended ones, then the OPA2141 might act as a gain stage for the JRC4556 headphones buffer, but I’m unable to prove that, as the PCB is quite opaque. However, this OPA2141 is the best performer from all opamps from the board, just not sure what is its purpose on the board.
The front panel/board has LEDs and potentiometers. I can spot three HC595AG 8−Bit Serial Shift Register with Latched 3−State Outputs. most likely to control the front lights, based on device state (INST, AIR, 48V etc.). I’ve also seen at least three more such shift registers on the main board.
Frontal board, with potentiometers and controls
The four potentiometers from this board are very similar with ALPHA RD902F-40-00D series, the one from headphone being probably logarithmic, while the other three probably being linear carbon tapers. Some Focusrite users seem to have troubles with such pots, same applies to ASUS Essence One users that are sharing similar APLHA pots, but time will tell how long will resist. One thing’s for sure, replacing them is quite difficult, because it involves a complicated way to dismantle the device, get out the boards and to then to unsolder double-sided soldered pins. Hope I’ll never have issues with these pots.
Frontal board, with potentiometers and controls
Last edited:
