SSL-2 audio interface

[Tubetec]

I decided to make a bid on an SSL-2 usb interface secondhand ,
The shock-jock wannbe Covid lockdown sensation fantasy didnt work out in the end,
theres a pile of these units out there for sale for silly money ,

noise ,distortion and bandwidth tests show very good performance ,

I was able to pick up the unit with the intact VST plugin liscence for 50% full rip ,
The Model 2+ incorporates a few extra features like a second heaphone cue and unbalanced in/out on phono ,
Model 2 and 2+ share the same pcb so the base medel provides for some possible hacks like adding an extra set of inputs ,

The 4K button is a farce , it would be better off reconfigured as a channel mute switch ,

 

[capacitor]

It looks like your post ended up somehow with ton of empty space, just fyi (edit: fixed)

It's good to know the SSL-2/+ is a deal, though! I'm interface shopping; currently have a Focusrite gen 2 that works well but I'm looking for something better.

 

[ccaudle]

I decided to make a bid on an SSL-2 usb interface secondhand

Sounds like something worth checking. What part of the world are you in, North America, Europe, elsewhere? I just looked on eBay (North America), and the first used one I found is asking more than I could buy a brand new one at Guitar Center.
Guitar Center currently has the 2 for $180 and the 2+ for $230. When I set the maximum price to $120 on the eBay search there were no used units available under that price. Looks like good used deals got snatched up already.

 

[Tubetec]

Theres a handfull for sale around my direction , usually from around 100-150 euros for the model 2 ,
its worth making sure you can get the licence for the plugins changed over , theres a facillity for the seller of a used interface to relinquish the licence on the SSL website ,that way the new owner is free to reregister , otherwise the licence is lost , so well worth checking that to make sure ,

This interfaces performance , for the money ,is only a hairs breath away from the best ,
theres a review with measurements here on ASR ,
https://www.audiosciencereview.com/forum/index.php?threads/ssl-2-usb-interface-measurements.22241/
How much would two channels of SSL mic/line pre in an API style lunch box cost you , a lot more than the SSL2 thats for sure , and you get the 2ch mixer ,usb interface and the plugins thrown in .
Even if its not connected to a computer it doesn matter it still puts out a proper all analog signal from mic/line in to master bus and cue outputs , theres no function on the device that needs to be accessed in software apart from sample rate and buffer size , every switch and control needed is on the front panel of the device .
Form factor looks like it should lend itself nicely to live or studio situations where you absolutely do not want to be skipping through menus in a panic , instead just reach out and touch instinctively and calmly make the required adjustment .

I just got confirmation on one unit I had a bid in on ,
waiting to hear back on another couple , I should have at least 1 more in the bag soon ,

I think I did see a partial schematic of parts of the SSL2 around somewhere , not sure .


frequency response at the various sample rates upto 192k

 

[soliloqueen]

i just switched from the equivalent audient to this SSL at my workstation and the difference in usability for a professional is huge. i would describe the audient as a high level consumer device and the ssl2+ as a low level professional device. it's cleaner too. the audient seems to pass usb bus noise into phantom power somehow. made my schoeps circuit mics hiss weirdly. no such issue on the SSL.

 

[Tubetec]

Theres a firmware update available for the SSL2 loopback function , the mixer L/R bus appears as input slots 3/4 in the asio driver panel , well worth having .

The handy thing about having a superclean interface is it will take all the harmonic distortion you can throw at it without adding much ,
I'll be interested to see how the SSL fares with transformer coupling in the mix to add a bit of sparkle .

Typically when I use a 58 directly into an interface without any eq the results are unsatisfactory , even the usual rumble filter if you have it is fairly innecfective against proximity effect , you end up having to use the low or low mid eq to scoop out a bunch of mud .
A passive HPF correctly tuned to counteract the proximity effect of the mic and the voice using it often gives me a very usable signal without the need for major channel EQ surgery.

Ive made a simple passive 10 position rotary proximity effect HPF ,
its a pleasure to use , the sweet spot jumps out and grabs you by the ears ,
Its a bit like pulling sonic focus on the source , if the sound changes during the performance its ok , you always have a few gentle steps in either direction on the HPF to compensate , if it changes back again ,you can return to the original setting instantly , with a decent condenser microphone on the right sound source it just works .

A quick question Solliloqueen ,
will the unit pass audio with only power connected , or does the interface need to see a computer before it wakes ?

 

[Tubetec]

I was able to take a closer look at the pcb here ,
https://www.ifixit.com/Teardown/Solid+State+Logic+SSL+2+Teardown/135354Its seems like the unit is entirely balanced from input to output , only switching in the 4K mode unbalances and adds distortion and noise to the signal , the dual op amp in the right hand bottom corner along with the dpdt switch on each channel add the 4K mode into the circuit ,
The handy thing here is it might be only a matter of desolding that op amp and the 4K button becomes an illuminated channel mute switch .
The other thing is theres plenty of real estate available on the back panel , it might be possible to add a direct out/send/return on TRS jacks , that opens up a lot of options as far as eq and compression is concerned ,
I cant really tell much more until my unit arrives , and I start poking around with the meter .

 

[Tubetec]

SSL2+and 2 backpanel ,
The headphone socket on the model2 occupies the space where the midi out goes on the other unit , theres already an unpopulated space on the pcb for two TRS jacks A and B , so hacking a balanced direct out from the mic amp looks easy , a normaled TRS send/return per channel looks entirely possible .
Be a cool way to get some iron into the SSL mix bus, a plugin module with a PCB mounted transformer inside and a couple of jacks that bridge the sockets ,
Unit should arrive by post tomorrow ,so a chance to take a closer look finally .

 

[john12ax7]

Seems a lot of bang for the buck. Wonder how it compares to studio staples like avid hd, apogee, lynx aurora, etc.

 

[Tubetec]

The mic pre's themselves achieve -130.5db noise , which isnt far off the theoretical limits
The mixer manages around -111db noise , thats very good by anyones standards .
In to out frequency response extends to around 90khz with a 192khz sample rate , slightly better than the other popular budget interface from Focusrite that many use for REW measurements .
I like the sloped console style enclosure a lot , its sure to make a it a pleasure to use where old style hands on control is what you want .
I can do a few comparative listening tests later and let you know my impressions .

 

[Newmarket]

The mic pre's themselves achieve -130.5db noise , which isnt far off the theoretical limits

Source Impedance for that ? 150R ? 200R ?
Is the consensus that 4K mode is a waste of time ?

 

[Tubetec]

They use the usual 150 ohm termination for the noise measurements .
The 4K mode adds a broad lift in the upper mids and highs , problem is many condenser microphones have a similar boost in that range ,so it may end up sounding sibilant or unatural on some sources.

 

[Newmarket]

They use the usual 150 ohm termination for the noise measurements .
The 4K mode adds a broad lift in the upper mids and highs , problem is many condenser microphones have a similar boost in that range ,so it may end up sounding sibilant or unatural on some sources.
View attachment 109081

Thanks for that spec.
Have to say I prefer to see unweighted figures wrt the A Weighting on Dynamic Range and EIN.
Mic Input Z looks curiously low to me. Not saying that's a problem - just used to seeing eg 2K2.

 

[Tubetec]

Package arrived safe and sound , unit is in brand new condition .

First impressions pots have a smooth precise feel ,
48v /line and Hi-z switches arent too bad ,
but the 4K switches feel cheap nasty and wobbly , the latching on channel 1 feels a bit ratchety already but it works fine ,for now ....

The unit powers up and passes analog signal with only USB power applied , so it doesnt rely on having a computer connected to give basic preamp/2ch mixer and headphone functionality . It will be easy to arrange a dedicated clean 5v battery supply to keep this thing well away from computer PSU noise , if that issue arrises .

The 5 segment led metering 0.-10,-20,-30,-40db are a usefull advantage over the standard red/green blinker found on units of a similar price range .

Another small source of anoyance is it doesnt sit 100% level on the four rubber feet underneath , Im sure thats easily remedied in any case .

Xlr/combo inputs are Neutrik , jack sockets are the usual insulated from chassis black plastic type ,
My few little gripes aside it feels good and solid overall , top panel is in an attractive gun metal grey brushed/anodise aluminium, end plate and backpanel are steel , the other part of the enclosure is plastic but its rock solid . Its torx screws all around so I'll have to have a dig around in the tool box before I take a look inside , more to follow .

 

[Newmarket]

It will be easy to arrange a dedicated clean 5v battery supply to keep this thing well away from computer PSU noise , if that issue arrises .

But be aware that even a battery supply doesn't necessarily get rid of all USB ? Computer noise related issues - depending on how the USB and Interface 0Vs are connected / isolated.

 

[Tubetec]

Of course yes even if the device is battery powered it still needs to share ground with the computer for the USB to work , thats a potential source of noise .

It will be interesting to look at the noise floor in the analog path through this device ,both on usb bus power and as a stand alone unit from a dedicated battery with no shared 0v .

 

[Newmarket]

Of course yes even if the device is battery powered it still needs to share ground with the computer for the USB to work , thats a potential source of noise .

It will be interesting to look at the noise floor in the analog path through this device ,both on usb bus power and as a stand alone unit from a dedicated battery with no shared 0v .

Yes. And (especially if using external / battery power) You can look at reducing influence from USB 0V by impedance in the 0V line that keeps the data lines within the common mode range. Basically a "ground lift" for data 0V rather than an audio 0V / Screen. This was discussed more fully somewhere here recently.

 

[Tubetec]

I was able to take a look inside the box ,
Theres no point in detaching the bottom panel , its the 8 screws on the top panel that count .
The bottom section has studded bolt built into it very much like the chassis safety earth connection found on gear , it looks like it was intended to be attatched to the pcb , this connection was left out so the bottom plate has no connection to 0V ,

Once I got in there I gave the areas where solder residue was left behind a clean , it made it a bit easier to see whats going on ,
The 4K circuit runs in parralel with the signal and is recombined with the clean by pressing the button , hacking a balanced direct out from the mic amps looks feasible alright ,

I had a listen with a small Peavey condenser mic and a set of phones , very low noise on mic and line input ,
Hi-Z input doesnt short to ground when nothings plugged in, it starts to buzz and oscillate at or around full gain on both channels , if you short the input it goes back to more or less the same noise as the mic input . I did an extra round of swabbing with iso just to make sure there wasnt any contamination left in the high z areas , it made no difference .

Something occured to me over night , when we either use hi-z input or engage the 4K button we introduce an unbalanced element into the signal chain , this means any noise on the supply isnt canceled nearly as effectively with either of those two modes engaged .
I tried a few different powerbank style battery back ups , they all seem to add a slightly different whine ,laptop on mains the same .
I understand its a bit unrealistic to take an open 1M resistor at the input, apply 62db gain and expect it to be quiet , not only that as you get to the last few db at the top of the pot , some other sqeal kicks in like a feedback loop gone bad ,its the power supply whine getting modulated as far as I can tell .

Anyway first job was to properly connect the baseplate to to rest of the metal work on the backpanel and top plate , I used the provided M3 thread on the baseplate ,I made up a short section of cable with faston terminals male and female in the middle and M3 eyelets on either end , I filed out the kensington lock slot to take a short M3 bolt , cleaned off the paint in the vicinity , and torqued it down .......
guess what ,
made no difference to the noise at all ,
By coincidence earlier I happened to have a mobile broadband modem in the vicinity while doing the first round of listening tests , channel 2 on H-z input was more prone to interference from the modem at high gain settings than channel one ,
Now that I had a chance to have a good look at the case , there are gaps that might allow garbage in , I think I'll do a layer of foil tape inside the plastic section of the case .

As I said I tried several powerbloc usb power sources , they run a noisy switchmode off a lithium ion battery to make 5v , each one had its own variation of earsplitting tones , like a set of broken bag pipes ,
I'm going to make a simple 5V battery supply which I know is very quiet to get a benchmark on what these SMPS switchers inject into the audio noise floor at extreme gain settings on usb power .

 

[Tubetec]

I was thinking about it over my afternoon coffee ,
I'm starting to take a serious dislike to this USB bus power , even the usb C connector and its accompanying socket are flimsy and waiting to get broken ,
I might have to install a dedicated 5v input socket on this unit , lift the leg on USB the socket that brings in bus power . Effectively ban USB as a power source on the unit fullstop ,


I did a trawl over people having issues with the SSL2 interface and sure enough many were relating to unbalanced input and noise , no co-incidence many who quoted specs of 1000W desktop PSU's supplying their bus power were having the worst time of it .

The other point I made about the 4K switch un latching roughly might need to be addressed ,
the feel of it doesnt inspire confidence at all , so I might have to reach out to SSL for spares , its not worth the cost shipping it back to England for them to take a look at ,
Is it just a case of put it in the bin and get a new one ? that wont be happening in this case .

Ive yet to do more real world tests on the interface ,results on mic input with phantom power were excellent though . I injected a 440hz balanced test signal from the iphone , everything is great until you hit a little above the 0db segment on the meters then very abruptly over the space of a few db it generates a range of audible harmonics , its nasty stuff , defiantely a place you dont want to be going levelwise .
All the garbage from the psu modulates on top of the clipped audio waveform ,

I was looking over the spec of the SSL 12 interface , it quotes a standalone powersupply to prevent the shortcommings of bus power , and 120db s/n , its also has +18.5dbu output capabillity , its supplied with an external 15v single rail switcher .

And by the way yes ,even though I was able to keep the headphone volume very low , my ears are ringing from listening to wideband SMPS garbage while doing the tests .

 

[john12ax7]

Interesting info so far. A lot of digital units will have the option of a dedicated wall wort supply if you don't want to power from usb. Seems a shame they didn't include that, would be well worth the few bucks more.