Focusrite Scarlett 18I20 gen2 impression and mods

Oct 2020.

Purchased a used Focusrite Scarlett 18I20 Generation 2. A budget component that I think, stock for stock, outperforms the MiniDSP 4x10HD at about the same price point.

I don't own the 4x10HD any longer, but compared to my 15 year old Yulong D100, I can tell that the stock 18I20 isn't subjectively as far behind as the stock 4x10HD.

Unlike the MiniDSP with 8 analog channels, the 18I20 has 10 (good for a stereo 5 ways or some basic 5.1 with active front speakers, the extra 2 analog channels are welcome)

A nice feature of the 18I20 is that the unit is silent, unlike the MiniDSP pain in the ass hiss that can only be minimised and never fully eliminated.

The 18i20 also boasts more gain while consuming minimal power. I haven't actually measured it, but I suspect it’s less than 40 Watts.

Close internal inspection revealed that there’s potential for upgrade in the Scarlett, although I don't get overly excited in modifying budget components anymore. Instead, I’ll do the bare minimum with mostly capacitors, some damping… and then call it a day.

No point swapping the stock SMPS to a double regulated linear power supply, or installing 11 new $20 high end opamps ($220 worth of opamp alone here on a $450 component, one have to remain logic)

As expected, the 5 DAC chipsets are budget type, which represents the bottleneck for this type of product.

18i20 on the shelf

front display

level meter used for input only, a toggle switch for input or output would be nice.

mic input

JRC 4565 upgraded to a JRC 2122, wow, lol.

18i20 on the shelf

1/10

Here are a few pictures of the inside on the left.

Some more details below:

Despite using the same budget DAC (CS4272) as the Behringer UMC204HD, the Focusrite does sound better, integration, power supply and opamps choice all matter.

I only use the Behringer as a data acquisition soundcard, and is USB powered. This USB power comes at a big sacrifice in performance compared to the corded 18I20.

Modification time!

As you’d expect, it didn't take long for a few modifications to be done on the 18I20.

Because the Scarlett is a budget component, I didn't go too far sparing undue expenses.

Focusrite… what did you do?

The power switch is reversed!!!

"On" is in the low position and "off" is at the high one. Bummer.

This is so counter-intuitive.

Generic SMPS of the 18i20

Brand: FEREX

Model: FP07M063
Applicable Products: DVB digital TV set
Input voltage range: 100V-240V
The output voltage: + 5, + 15V, -15V, + 51V
Output Power: 10W

Output characteristics
     Output combinations: + 5V, 2A; + 15V, 0.7A; -15V, 0.7A; +51 V, 80mA
      Ripple: 50mV Not great by any mean.
      Efficiency: 70% Min. (220V AC / Max Output Current)
Insulation resistance: 30M Min DC 500V
Mean time between failures: working time 50000H

After the SMPS. The +15 Vdc and -15 Vdc analog power supply rail are passed through the two green power resistors, and attenuated to about +-10.6 VDC.

Then, a few 220uF capacitors filter the voltages (forming a classic, passive RC filter)

Then, the two power rails are regulated to +6.9 Vdc and -6.9Vdc via the LM317 and LM337. (average regulators but good enough for the 18I20)

The +3.3 VDC is obtained from the +5 VDC after two stages of passive LC filter, and an active regulator chip. Not too bad, and no noise measured there.

Not shown on picture. I added extra filtering capacitors. Some leftover Elna Silmic II.

the 3rd regulator is zener regulated mosfet for the +48Vdc phantom power. I haven't touched this area.

2 NJM 4556 are in charge of the 2 headphone output. (only one shown on picture)

I haven't touched that section as I will never use the headphone output on this unit. For monitoring, I urge you to replace them with some LME49600 but one will have to replace resistors as pinout won't be compatible with the stock NJR4556.

Output analog opamp (analog line out 3 to 10)

I've changed the original NJM4556 to the excellent but affordable LM4562.

4 output capacitors have been removed and bypassed

(monitor output, AKA line 1 and 2)

16 output capacitors have been removed and bypassed (line 3 to 10)

CS4392 DAC for monitor output (1 and 2) and its 2 opamp to its right.

I've changed the two opamps to the LM4562, notice the extra cap added on the CS 4392 DAC.

Elna Silmic II bypass capacitor on the opamp power supply rail.

Panasonic FR capacitors used as power supply bypass for the DAC's analog +5VDC

Overall, I'm satisfied with this modified 18I20.

Removal of the electrolytic output capacitor achieved dynamic and extra layer to the sound, which the stock unit didn't do.

The Opamp upgrades, 11 totals for the 10 analog outputs, (not counting the two headphone outputs) achieved clarity and a more transparent sound.

All the extra bypasses on the power supply improved the bass giving more drive to the 18I20.

For the apartment setup (October 2020) , driving the affordable JBL 306P front channel and my quad 12" subwoofers, the Focusrite is the right match.

I would think that the affordable JBL306P are more of a bottleneck that the 18I20 is, I may change my JBL and use some 15" woofer soon, nothing move air like a 15" does... after 3 consecutive houses, going back to living in an apartment, even if planned for less than 1 year, is hard. Sound system sacrifice LOL.

Happy listening.