Sonic Frontiers SFL-2 Preamplifiers

5/5 (6 Reviews) MSRP : $3795.00


Product Description

Tube preamp with external power supply


Review Options:  Sorted by Latest Review | Sort by Best Rating

Reviews 1 - 5 (6 Reviews Total) | Next 15

User Reviews

Overall Rating:5
Value Rating:5
Submitted by MarkSAllen a AudioPhile

Date Reviewed: August 20, 2006

Bottom Line:   
The problem with writing reviews (and especially with allocating 1-5 stars) is that you get to read them years later when you have more experience and you have (hopefully) steadily improved your system. You realize that it's all relative.

I've owned a Musical Fidelity NuVista M3 amp for the last 5 years and gave it a 5/5 rating when I bought it. Make no mistake, this is an outstanding integrated amp and at that stage in my audio journey I fully believed that it deserved that rating. The problem is that I've now heard better... significantly better...

I recently traded in the M3 (along with every spare thing that wasn't being used around the house) and bought a used pair of Wolcott P220m amplifiers. Now one of the problems with upgrading from an integrated is that you have to buy both an amp and a preamp at the same time. Due to the cost of the Wolcotts (about $4500 used) I bought the cheapest good preamp I could at the time - a used Audio Research LS-3 that came with a Creek OBH-10 passive remote volume control (total cost $600). This had the added advantage that I could try out the Wolcotts with both an active (LS-3) and passive (OBH-10) preamp.

Let me unequivocally say that the Wolcotts are the best amplifiers that I have ever heard and, I currently believe, perhaps the best that I will ever hear. I heard 30% more music - it is that simple. Not only that but the sense of 'being there' was so strong that it was simply incomparable to what I had before. And this was with them being fed by a $600 preamp!

I've listened carefully to what it is that is so striking about the new sound and come to the conclusion that it is a combination of things:
1) The first that struck me was that sounds had much more of the accompanying harmonic content than they did before. What was identifiable before as the artist knocking on his guitar, became more... you heard the knock but you also heard the detail that went with that - I can best describe it as hearing the quality of the wood! Without any mistake, you also heard the sound of how the knock resonated in the six associated strings! What was previously just a knock became a superb, captivating, harmonically rich event! Now consider that every sound heard now had that harmonic richness associated with it and you start to get an idea of the impact that this has. Which leads into the next difference...
2) The separation of sounds and instruments into their constituent parts was breathtaking. What was a collection of performers merging into a single performance became individual performers, each uniquely identifiable and yet an integral part of the overall performance. I can only think that the ability to hear all aspects of each sound allowed your brain to easily identify where it came from.
3) As mentioned, the feeling of being there and being part of the performance was far stronger than before and I can only put this down to an increase in the depth of the soundstage and the rock-solid stability of the instrument images.

Which leads me on to the Sonic Frontiers SFL-2 preamp... thought I was never going to get there...

The quality of sound from those Wolcott amps simply demanded the absolute best preamp that there was! The five preamps that very quickly became options were the Lamm LL2, the Sonic Frontiers Line 3, the Conrad Johnson 17LS2, the Joule Electra LA-100MkIII and the Hovland HP100. The problem was that these were all serious money (with the possible exception of the Joule) and I didn't want to wait. Enter the Sonic Frontiers SFL-2 - a no-holds-bared preamp at an unbelievable price for what you get of $1200 (used).

Now when SF say "The goal was to build the best preamplifier available making absolutely no compromises", they seriously, SERIOUSLY mean it! This is a preamp with a separate chassis for the power supply. Not only that, but this is a dual mono power supply - nothing shared between the two channels, including the transformers! No electrolytic capacitors are used in this power supply - they are metalized polypropylene capacitors, which are considerably more expensive but they sound better. There are FIFTEEN regulators in this power supply!!! Most preamps have two or three. Most preamps use a winding from the mains transformer of 6.3V A/C to supply the tube heaters - not only does the SFL-2 use DC for this purposes (to avoid any possibility of hum transfer), but it is regulated DC!
Moving on to the preamp itself, all wire and RCA sockets used are from Kimber Kable. Only the best resistors available are used, incuding Caddock and Vishay resistors. The volume control is not the usual high-end Alps potentiometer but a switch with a resistor ladder on it (the time taken to actually make this component must be measured in hours). There is ero loop feedback. The digital circuits are completely separated from the main circuit board by a physical metal partition in the preamp, and so it goes...
So let’s look at one or two aspects of the measured performance. 2Hz (yes, two) to 100 KHz at 0.5 dB down (350 KHz at 3dB down!) - no question at all that any harmonics are going to be attenuated. Most amps require an input drive voltage of 1.5V RMS - the SFL-2 has a maximum drive voltage of 30V RMS! Certainly no concern about ANY music peaks being limited by the preamp!

So how does it SOUND?
Well first of all, it is as quiet as the grave. I could not detect ANY noise with my ear next to the mid-range/tweeter ribbon of my Apogee Duetta Signature, with the volume wide open.
The bass performance of this preamp is something to behold. I don't know if it is due to the 2Hz frequency response spec (I know that the human limit to hearing is 20Hz…), but any thought I had of buying a subwoofer disappeared in an instant! If it wasn't for that ruler straight frequency response line I'd swear that they boosted the low bass in the preamp. It was considerably better than the bass from the Wolcotts with both the LS-3 and the OBH-10. Firm, clear, deep. Startling is the right word!
The all-important midrange was perfect and very similar to that produced by the passive OBH-10. The richness of harmonic content that made the Wolcotts so attractive was not affected and, if anything, the solidity of the instruments in the soundstage improved slightly, although this was by just a smidgen. When compared to the LS-3, the LS-3 seemed to give a bit more of a prominence to the sound, which I found to be attractive but this became almost too much of a good thing after a while. Unless you can hear the real performance being compared to the music being played back, this all comes down to preferences and any judgment becomes relative. I have the good fortune to have been married to a professional opera singer for 25 years and after this amount of time and having attended a very large number of her performances, I have a good feel for the quality of sound of her voice. Playing back some of her recent recordings made as part of her Master’s dissertation, I definitely preferred the sound of the SFL-2 and felt it was closer to hearing her singing live. The feeling of “being there” and being a participant in the performance was very strong indeed and highly addictive.
The performance of the SFL-2 in the treble range was impeccable. Once again, the harmonics associated with cymbals and high bells were freely produced, giving a sense of “air” and dimensionality to the sound. Not only was that air there but the tinkling of wind chimes made you almost imagine you felt the breeze. Amazing stuff! To give you a sense of the realism, two quick knocks on wood in the performance had my wife getting up to answer the front door! I had to replay the piece to convince her that it was the music she was hearing!
All in all, this preamp fully compliments the considerable strength of the Wolcotts and Apogee Duetta Signatures. It truly pushes the sonic frontiers and is HIGHLY recommended.

Expand full review >>

Used product for:   1 to 3 months

Duration Product Used:   AudioPhile

Product model year:   Pre 1995

Price Paid:    $1250.00

Purchased At:   Audiogon



Overall Rating:5
Value Rating:5
Submitted by Mike a AudioPhile

Date Reviewed: December 7, 2003

Bottom Line:   
I went from a lower end Audio Research tube preamp to the SFL-2. I brought it home and listened for two hours straight. I could not believe how well the SFL-2 defines the sound stage. The highs are detailed and relaxing. The midranges are rich and have great depth. Low's are extended and tight. Dynamic range is is this preamps greatest strength. I can't believed how much head room it brings to the table.

Expand full review >>

Used product for:   More than 1 year

Duration Product Used:   AudioPhile

Product model year:   1996

Price Paid:    $1000.00

Purchased At:   Local hifi shop



Overall Rating:5
Value Rating:4
Submitted by drramsey a AudioPhile

Date Reviewed: June 12, 2002

Bottom Line:   
Well, after many years of continual changes and tweaks, I have found the pre amp that will keep its place in my system. The SFL-2 is simply the best match for my system and room.

It paints a clear image of the respective data. I have upgraded tubes and wiring (a little mit silker than stock), but only as a tweak. The SFL-2 has great sound right out of the box (after 30-35 hours of break in. It is awsome with analog master disc. I do think that the use of a good tube phono stage is a must! Do this pre justice and step up to the plate, don't skimp on the phono stage! If you get the chance to grab one of these don't miss it. You will be happy!

Expand full review >>

Used product for:   3 Months to 1 year

Duration Product Used:   AudioPhile

Product model year:   1995

Price Paid:    $2300.00

Purchased At:   Audiogon



Overall Rating:5
Value Rating:4
Submitted by Jeff a Audio Enthusiast

Date Reviewed: May 25, 2002

Bottom Line:   
What can I say about this unit. I was lucky to " find " one owned by a wealthy audio nut who had twiced move onto another preamp. He was more interested in freeing up some space than he was about getting a good price for this unit. His loss is my gain. I can't believe how open my system is now. My previous Pre was a hybrid tube/MOSFET design and so the SFL-2 was my 1st major step towards committing to an all-tube system. I'll never go back. The beauty of the tube sound must be heard to be believed!! And the great thing about tube gear is that you can change the tubes to modify the sound. The SFL-2 is built very, very, very solid. It's a little much when you first take the unit out of the box. But once you get settled and setup....you'll appreciate why the unit is built so solid. I have built the rest of my system around my SFL-2. I have never heard such clarity and I never thought that could happen by just changing out my preamp. If you can find an SFL-2 in good condition from a solid buyer, get it! I can't recommend this unit enough.

Expand full review >>

Used product for:   3 Months to 1 year

Duration Product Used:   Audio Enthusiast

Product model year:   1996

Price Paid:    $2500.00

Purchased At:   Audiogon



Overall Rating:5
Value Rating:5
Submitted by Larry a Audiophile

Date Reviewed: January 18, 2002

Bottom Line:   
I was lucky enough to come across a perfectly stunning used SFL-2 at a local dealer. The prior owner had moved into an entire system of VAC gear and no longer wanted his SF gears. He was " one of those " audiophiles who had more money than sense and was giving up perfectly good gear for reasons which were only clear to him. He'd upgraded my SFL-2 with better tubes and had some direct source wiring done which basically resulted in about $1500.00 worth of upgrades. All of which benefit me in the end. This unit new with upgrades would have cost well over $5000.00 and I was able to acquire it for about half that amount. Why? Because that's all the guy wanted. Again, his loss is my gain. I've never been happier. The SFL-2 is built like a Sherman tank. I swear you could drop it off the side of a 10 story building and it would walk away clean and still sounding sweet. What impressed me most about this unit was the clarity and " clean sound " it produces. Most Sonic Frontiers gear come with standard NOS tubes, usually Sovtek. Nothing wrong with that but I was looking for something more. The previous owner has spent some money and had matched sets of 4 pairs of Amperex tubes put in. They sounded sweet. I went a step further and found a series of matched Mullards and the system went even a step further. The bass is deep and tight, the highs are clean and sweet, and the mids are rock-solid. Also, I have several inputs (SACD/CD, CDR, Tuner, Phono, Tape) and the SFL-2 has more than enough input sources to handle what I've got. Most high-end gear only have 1-3 input sources and I would say that having several is another plus for the SFL-2. I highly recommend this unit and consider it to be one of the greatest pre amps out there.

Expand full review >>

Used product for:   More than 1 year

Duration Product Used:   Audiophile

Product model year:   1996

Price Paid:    $2200.00

Purchased At:   Sonic Frontiers dealer




Reviews 1 - 5 (6 Reviews Total) | Next 15

Review Options:  Sorted by Latest Review | Sort by Best Rating



Axiom Audio:



SFLAT: