Focusrite Saffire Pro 40 re-cap

[Khron]

I got this lovely and versatile audio interface a couple years back, for some multitrack recording with my (former) band, and as a "foundation" for my (future?) home-studio.

A while back, i decided to "pop the hood" and check out the insides. The PSU made me cringe - C(r)apXon It puts out 5v for the digital/logic stuff, +/-15v for the analog stages, and 51v for the phantom-power. I haven't yet replaced the mains filter cap (since i figured it's not under THAT much strain, plus i don't have a suitably-sized one in stock... for now ).

Re-cap stage one:
- the 5v line received a 1200uF/10v Chemicon LXV before the inductor, and an 1800uF/6.3v KZJ after it. This is the rail where the feedback is taken from.
- the +/-15v rails got a pair of 470uF/35v Panasonic FR each
- i left the two 100uF/100v CapXon GS in place, since i didn't have such high-voltage caps (for now), and the phantom power isn't that power-hungry anyway

While i had the psu out, i decided to upgrade the switching FET and the 5v rectifier. FQPF8N60C got replaced by a 2SK2761, and i slipped in an STPS2045CT instead of the MBR10100CT.

Throughout the rest of the inside (ie. the main board), Jamicon SK (85c general purpose) as coupling and power filtering caps, and five Samxon GF 220u/50v on the 5v / 3.3v / +/-6.9v outputs. The +/-6.9v and the 48v phantom-power have LM317/337 voltage regulators on them, and they had SK's right at the output, then an inductor, and then the Samxons.

The attached pic is a "before" shot of the mainboard

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

Re-cap stage two:
- analog input caps = 47uF/63v Panasonic M (i still have 24 of them to change, out of 32, 4 per input - two for the mic in, and two for the line in)
- analog output caps = 220u/16v Rubycon YK (100u/25v originals), 20pcs
- preamp gain control DC blocking caps = 1000uF/6.3v Rubycon YXG (470uF/16v originals), these are the 8mm dia. caps on the left half of the board
- ADC input buffer coupling caps = 47uF/16v Chemicon SMG (10uF/16v originals), the 8 tiiiiiiiny caps in the middle of the board, each near an SOIC8 opamp
- Filt+ filter caps for the codecs = 330uF/6.3v Sanyo ME-SWG (10uF/16v originals)
- Vcom filter caps for the codecs = 510uF/4v Sanyo OsCon (470uF/16v originals)
- headphone amp input caps = 22uF/50v Panasonic FC (10uF/16v originals), between the three white 5-pin headers in the middle-bottom of the board
- heaphone amp +/-6.9v filter caps = 470uF/10v Chemicon SMG (47uF/63v originals)
- 3.3v filter caps = 2x 2200uF/6.3v Rubycon MBZ (green Samxon originals, 220u/50v)
- 5v "out" cap (post-inductor, near the 5-pin J22A) = 2200uF/6.3v Rubycon MBZ (ditto)
- +/-6.9v post-inductor caps = 2x 1200uF/16v Rubycon ZL
- 5v in filter cap = 1000uF/16v Panasonic FL (8mm cap in the bottom-right, near the white power-in header)
- +/- 15v in = 2x 100uF/25v Chemicon KMF
- +/-6.9v out (at the LM317/337 outputs) = 2x 470uF/10v Chemicon SMG

Once i'm done with the remaining 24 input caps, i'll add an "after" snapshot as well

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

Haven't replaced the phantom-power filter cap on the mainboard either, for the reasons mentioned in the first post, regarding that section of the PSU

All in all, a pretty well-designed piece of gear, if i may say so myself.

Preamps are NJM2122's (noise rated at 1.5nV/sqrt(Hz)), with a pair of TL072's for the high-impedance instrument inputs.

There are several HEF4053 multiplexers/analog switches in the input section. I haven't bothered trying to trace what they do (it's a 4-layer PCB), but i've got a hunch that the 1/4" jacks in the Neutrik combo connectors might be switched, and the 4053's switch between the high-gain (for mics) and low-gain signal paths.

The rest of the opamps are NJM4565's, and the headphone amps are a pair of NJM4556's in SIP8 packages.

There's a Cirrus Logic CS4392 DAC chip (for the "monitor out"), and four CS4272 codec's for the 8 analog ins / other 8 analog outs. Both part numbers rated for 24bit/192kHz, by the way, but "restricted" to 96kHz by design

[budm]

Re: Focusrite Saffire Pro 40 re-cap

As you can see, there is no mechanical switch that the audio signals flow through for selecting the input or for routing the signals, they are done through electronic switches such as 4053 MOSFET switcher, a lot of people do not like this method since it is active components instead of using passive components for switching signals. Most companies are doing this way since it is a lot cheaper than using multi-gang mechanical switches.

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

Yeah, i kinda thought that was the only explanation (that made sense) Not to mention it's quite space-efficient...

And i'm 99,5% POSITIVE it's just self-suggestion and stuff, and not that i have uber-"critical" gear and room treatment, but i could almost swear the mid-highs are a wee bit "clearer", and the lows a tiny bit more "balls-y"... but don't quote me on that :P

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

Okaaaaay, re-cap 100% completed, at long last

I've already got "phase two" in my sights: replacing all the op-amps with NJM2068's (lower noise, slightly higher GBW, open-loop gain and slew-rate).

Anyway, as promised, here are a few "after" snapshots

[rapido]

Re: Focusrite Saffire Pro 40 re-cap

Looks nice.
I been looking at modding my interface too.
So was all the work worth it, or are the difference not big enough to make a real impact?

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

Well, getting those C(r)apXon's out of the power supply was at least for "peace of mind", because CapXons WILL fail, sooner rather than later.

Regarding the rest... See the second post before yours

[rapido]

Re: Focusrite Saffire Pro 40 re-cap

Been looking to swap in some of the good audio graded nichicon/muse caps in there.

Haven't done much recapping so are still learning.
Why did you choose to use capacities so much larger than the original?
And for some using lower voltage rated ones?

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

I've personally never bought into that whole audiophile-mojo "magic" cap malarkey, but... To each his own, i suppose

I'm guessing the "so much larger" part refers to the power supply caps. Well, basically, to try to lower the ripple and noise as much as possible. Caps and the trace / wire resistances, basically, form RC and/or LC low-pass filters, and you want the corner frequency as low as possible, preferably far below the audio range (so there's as much attenuation at the SMPS frequencies).

[PhilippHoeger]

Re: Focusrite Saffire Pro 40 re-cap

I'm also into modding my saffire 56. started my recap with some panasonics.

But: What would be the best opamp replacements?
The originals seem to be the same as you listed for the saffire pro 40.

Thank you for this thread!

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

As far as i know, the 40 and 56 are virtually the same unit, sans the extra ADAT in and the Liquid DSP

As i mentioned in my last post with pics attached, i've set my sights on some NJM2068's.

I haven't ordered any yet, and i'm (still) thinking if i should replace the NJM2122's as well. Too bad some of the datasheet measurements weren't made with the same parameters. But judging by the "equivalent circuit", the appear to have class A outputs.

Still, the 2068 specs look (even) better - lower THD at a greater load (5V into 2kohm vs 1V into 2.5kohm), and even lower(?) noise, MUCH better PSRR...

I'm just glad someone (else than me) found some value in this

[PhilippHoeger]

Re: Focusrite Saffire Pro 40 re-cap

Did you compare these to other opamps like the OPA2134 ? They're being used for many mods.

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

I based my decision on this batch of measurements:

http://nwavguy.blogspot.fi/2011/08/o...surements.html

That, and being able to find NJM2068's pretty cheap on fleaBay Or at least a lot cheaper than the "boutique" models

[PhilippHoeger]

Re: Focusrite Saffire Pro 40 re-cap

thank you

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

You're welcome And happy modding

[PhilippHoeger]

Re: Focusrite Saffire Pro 40 re-cap

so let me know about your opamp replacement results. It's hard to decide what to chose, because there's much differing talk on opamps on the net.

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

Well, i've still got some way to go before i can say i've got "critical listening equipment", so i'll go with what real-world measurements say If NJM2068's are cheap AND quiet... why not?

But don't hold your breath - i've got a whole bunch of other things of waaaaaay higher priority, at least for now, and replacing 20-40 opamps is not exactly "a walk in the park", so... It might be a while until i actually get around to trying that out

[PhilippHoeger]

Re: Focusrite Saffire Pro 40 re-cap

I'm not in a hurry tuning this box
Yes! I've got 48 opamps in the Saffire 56... and still didn't get all my caps either.
will take some time, but I think I'm gonna check some different opamps on this and let my ears decide since I'm not really into measuring these little beasts.

happy soldering ! :P

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

There's one thing to keep in mind, though: these NJM opamps are in a "wide SOIC" package. The legs of the normal SOIC8 opamps might not reach the solder pads of the originals.

SOIC8 "narrow" is ~6mm tip-to-tip, while SOIC8 "wide" is 8mm.