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 Post subject: Sonic Frontiers SFL-2
PostPosted: Wed Jan 19, 2011 11:04 am 
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Location: Campbell River, BC, CA
First a bit of back story.
Been thinking of one of these for about the last decade , not wanting to spend money rather barter for.
I came into a Thorens 124 that put on CAM while back , that was willing to trade for preamp , few replies to the barter.
But as nothing ever goes away on line few months later bartered & cash changed hands & I got a SFL2....& guy got a great collection of Thorens gear....so thanks CAM !!

First when got ran on bench , did freq sweep , set up balanced outputs (adjustable gain on one output).
What was good the preamp has rather flat responce over used area , little drift from perfect around mids but strong output even at 20 HZ , this should sound good....
The construction of the unit is first rate as well , this always appealed to me.

The tubes are Valvo , something I'm not sure about so included pictures , installed the pearl coolers as why not.

Been doing some serious listening at home AB vinyl with server , trying many albums.
It certainly sounds differant , the main thing seems to offer a wider & deeper soundstage.
But Sub is not in use as well as DEQ bypassed , so bit of problems there.
I think will take few weeks to really decide if want to run dual preamps , the Preamp I use in my main system is a Anthem AVM20 , which is only supposed to be good for stereo but not great.
So far not enough time into to really decide.
But as a popular unit at one time wondered about what people used for tubes in this thing , as no doubt have to try some !
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PostPosted: Wed Jan 19, 2011 7:52 pm 
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Location: Courtice, ON, CA
Image, Brian.

And the proper faceplate colour too :wink:

This is a very good preamp which excels at allowing the music to shine through relatively unscathed. It's not your typical tube pre which imparts a ton of lushness onto the scene however. Even with lush sounding tubes.

As you have seen, there is no shortage of high quality componetry and design work inside. The proverbial "built like a brick $hithouse" certainly describes the SFL-2 to a T.

Try your hand at different tubes and experiment. My favourite combo is Gold Aero's in the back 2 spots and Siemens in the next 2. EH's in the front 4, non signal path spots. Never tried the Valvos.

Enjoy, buddy!

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PostPosted: Thu Jan 20, 2011 2:24 am 
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Posts: 1380
Location: duncan, BC, CA
Hey Krazy I'd remove the coolers and give a listen for a while...
The S.F. gear tends to be very neutral and the coolers may take
a little of air out of the sound. I would really try to find the Amprex
7308 or the e188cc phillips mini watt to use in the critical positions.
Then maybe some less expensive varietys of 6922 in the same
brands...
This is a pre-amp that is good enough to deserve these tubes.
Remember that if you don't like them they are all easy to
resell.
Watch nick72 his adds or contact him for pricing for said tubes.
I've found him to be very fair and reasonably priced...


All the best Les


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PostPosted: Thu Jan 20, 2011 4:48 am 
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Location: St.Thomas, ON, CA
My buddy uses mullards in his sfl-2

I agree with Les, you can experiment with several and sell what your not happy with

You might want to drop Chris a line at parts connexion, he was part of the SF team


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PostPosted: Thu Jan 20, 2011 6:41 am 
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Location: Nepean, ON, CA
Wow you got a great (legendary) unit and with Valvos!! Most sellers would have sold those tubes on eBay for a fortune and retubed the amp with stock Sovteks or something before selling it.

If there is no noise and the gains measure well I would leave well alone the Valvos. You could be in for a lot of labor and anguish for little gain if you start rolling tubes. A lot of NOS are noisy if not used carefully. You might want to upgrade the capacitors instead. The stock ones are nothing special and this is less risk, more of a certain upgrade.

I upgraded my SF Line 3 with Hovland caps and never looked back (changed a few resistors too). Tubes on the other hand are always problematic as the pre drives SOME of them very hard.

The SFL-2 is very close and in the opinion of some possibly the best thing SF ever made. Enjoy!

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PostPosted: Thu Jan 20, 2011 8:46 am 
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Location: Waterdown, ON, CA
Hey Krazyclocks. Nice preamp. As DR3 mentioned above, the Valvo's are one of the better sounding tubes in the ecc88 family and if they are infact authentic Valvos and low in noise, you would be hard pressed trying to better them. Authentic nos Valvo's will have a date code starting with the letter D etched near the bottom of the tube.
Re: Multicap capacitors. It's rather difficult to ascertain from your photos which type Multicaps where used for the coupling positions.
However, if they are the ppmfx versions....yeeeech, a wretched sounding film cap thats about as dry and two dimensional as they come.


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PostPosted: Thu Jan 20, 2011 10:06 am 
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Location: Thornhill, ON, CA
DR3 wrote:
I upgraded my SF Line 3 with Hovland caps and never looked back (changed a few resistors too). Tubes on the other hand are always problematic as the pre drives SOME of them very hard.


dr3, would you have some insight into which tubes make the biggest difference in the line 3? with 12 tubes total, i find that retubing that line stage could be an expensive proposition. i like RCA black plates 6U8A in those spots (but i also have a pair of tung-sol 6U8A black plates waiting in the wings...). if you have some ideas on which 6922 spots are critical that would be awesome.

i did get a cost chart from chris @ partsconnexion as to an upgrade path. the caps and resistor changes look pretty sweet.


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PostPosted: Thu Jan 20, 2011 11:53 am 
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Location: Campbell River, BC, CA
Thanks for replies !

Spent another evening listening to music , various stuff Swing Music was mainly focus.
It really is like differant stereo , the differance is quite great.
However missed the Sub , used the AVR to fill the sub bass , not really hear just fill in lowest octave.
Listened to some heavy bass tracks it still follows the music well , still something about the mids , reminds me of vinyl , only problem is shows best on better recordings.
Will not do anything for a few weeks to get feel for it , no mods yet or ...
Probally eventually roll some tubes as otherwise never know.

Any info on 6922 tubes be welcome.

Kerry a mix of tubes seems like good idea , the last 2 positions seem to be most important as they deal with load of preamp.
FYI the unit has only caps in output stage 4 - 3ufd bypassed with 4 - 0.022 ufd not sure exact what they are.
This unit I think was last version made version 3 , so should have been latest version from around 95.

At any rate it is one heck of a unit , a shame that did not continue the same way , something actually made in Canada !!!
PS : Feel like the picture Yaaa Baby !!

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PostPosted: Thu Jan 20, 2011 1:27 pm 
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Congratulations, I loved my SFL-2.

Do you have the service manual for it? There is an adjustment procedure that should be followed each time the tubes are changed; I believe it's to compensate for tube variances since the unit is fully balanced. I was fortunate to have a friend who was familiar with the procedure help me each time I changed tubes.

I did a fair bit of research on tubes when I bought my SFL-2 as it arrived with Matsushita tubes that were past their prime. Siemens 7308's seem to be the most recommended choice with these units, but they aren't easy to come by or inexpensive when you do. I spoke with Kevin Deal @ Upscale Audio, he said EH select grade were the only thing he could recommend at the time. I also spoke to Andy @ Vintage Tube Services; he advised this model is hard on tubes, and recommended only using ones known to be robust with matched sections. Mine sounded great with EH in the four forward most positions, and Siemens at the back, which is how I sold it.


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PostPosted: Thu Jan 20, 2011 7:06 pm 
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vinylkid wrote:
dr3, would you have some insight into which tubes make the biggest difference in the line 3? with 12 tubes total, i find that retubing that line stage could be an expensive proposition. i like RCA black plates 6U8A in those spots (but i also have a pair of tung-sol 6U8A black plates waiting in the wings...). if you have some ideas on which 6922 spots are critical that would be awesome.


LV1 & V2 - which are the two right next to the 6U8A. These tubes are doing all the real work so put your money here. They need to be low noise, matched pair and matched internally.

The remaining 10 tubes are just doing grunt work and much less critical. In fact as long as they are capable of driving good current you probably won't hear them. You want inexpensive but healthy (strong emission) tubes here.

-- 21 Jan 2011 03:23 --

krazyclocks wrote:
FYI the unit has only caps in output stage 4 - 3ufd bypassed with 4 - 0.022 ufd not sure exact what they are.


The large output caps are probably PPFX or PPMFX bypassed with RTX (supposed to be better).

When I upgraded mine we replaced the whole affair with single good Hovlands (no bypassers). It sounded much more organic and removed the "mechanical" sound.


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PostPosted: Fri Jan 21, 2011 5:44 am 
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DR3
What really does the other 10 tubes do ?
Does the signal only pass through LV1 and V2 ?
I have tubed roll the other 10 but without any change that I can hear and yes, LV1 and V2 really changes the music.

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PostPosted: Sun Mar 13, 2011 3:42 am 
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does anyone have the procedure for biasing this unit,


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PostPosted: Sun Mar 13, 2011 4:58 am 
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Location: Mississauga, ON, CA
-I once worked for SFI. Please... don't ask me to even try to explain all of the insanity that was going on there in the '90s. No... you REALLY don't wanna know what Jensen & Johnson were doing inside of that company; nor the events that transpired to cause its financial collapse. Why? Well... truth is often stranger than fiction. And hey... neither I nor my lawyers need the lawsuits for slander and/or libel.

-Anyhoo... for your SFL-2 or any of the line series pre-amps, try Siemens-Halske 7308 gold pins. Watch for fake tubes though. The real 1960's S-Hs are VERY expensive and only about 50% of them survive longer than a month in SFI units.

-The big problem with SFI's pre-amps is that they burn through exotic NOS tubes with an obscene frequency. The main reason for using what Johnson claimed were NOS Valvos in the Special Edition (S.E.) versions of SFI's pre-amps was that they're a hearty tube. The "Valvos" you've photographed have lightning fast transients, great highs, a semi-warm mid-range, and neutral mid-bass and low-bass. Not exactly the last word in warmth, but they're fast; lightning fast.

-I've also had some success with NOS Tesla E88CCs. They're an early 1970's tube, fairly robust, and deliver about 90% of what the S-H gold pin 7308s provide in the mid-range.

-As several other posters have suggested, look into upgrading the caps, the internal wiring, and even the o/p connectors on the back of the unit (i.e. try Nex-Gen RCAs). If you're thinking about using Johnson at PCx for these upgrades... well... think long & hard before dropping any coin. You'll might find that you get more mileage (sound & money wise) out of a parts upgrade that you install yourself (or have installed by a qualified bench tech).

Cheers... and best of luck with the upgrades.


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PostPosted: Sun Mar 13, 2011 5:28 am 
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Location: Ottawa, ON, CA
SSM DSB wrote:
... For your SFL-2 or any of the line series pre-amps, try Siemens-Halske 7308 gold pins. Watch for fake tubes though. The real 1960's S-Hs are VERY expensive and only about 50% of them survive longer than a month in SFI units.

-The big problem with SFI's pre-amps is that they burn through exotic NOS tubes with an obscene frequency. The main reason for using what Johnson claimed were NOS Valvos in the Special Edition (S.E.) versions of SFI's pre-amps was that they're a hearty tube. The "Valvos" you've photographed have lightning fast transients, great highs, a semi-warm mid-range, and neutral mid-bass and low-bass. Not exactly the last word in warmth, but they're fast; lightning fast.

-I've also had some success with NOS Tesla E88CCs. They're an early 1970's tube, fairly robust, and deliver about 90% of what the S-H gold pin 7308s provide in the mid-range.

-As several other posters have suggested, look into upgrading the caps, the internal wiring, and even the o/p connectors on the back of the unit (i.e. try Nex-Gen RCAs). If you're thinking about using Johnson at PCx for these upgrades... well... think long & hard before dropping any coin. You'll might find that you get more mileage (sound & money wise) out of a parts upgrade that you install yourself (or have installed by a qualified bench tech).


I'm humbled by the wealth of knowledge from people here.

Does the preamp go through 6922's because of cathode stripping or because of excessively high plate voltage ?

Were they voiced with S-H e188cc o getter, or A frame solid disk getter ?


On line, I bought a Sonic Frontiers DAC I, that had been modded by a former person from SF.
Not sure who the modder was - but it sounded terrible.


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PostPosted: Sun Mar 13, 2011 6:36 am 
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Does the preamp go through 6922's because of cathode stripping or because of excessively high plate voltage ?

Were they voiced with S-H e188cc o getter, or A frame solid disk getter ?


On line, I bought a Sonic Frontiers DAC I, that had been modded by a former person from SF.
Not sure who the modder was - but it sounded terrible.

Uunderhill
----------------------------------------------------------------------------------------------------------------

-I can't really get into discussing (i.e. dissecting) the designs of some of SFI's 1990's pre-amps. Let's just say that the designs were "works in progress."

-"Voiced"...? You're kidding... right(?). I'm sorry, but I laughed for 10 minutes when I first read your query. Do you really think anyone at SFI in the 1990's was "voicing" anything? C'mon bro... you know how "volume oriented" tube audio businesses work, right? Nail the unit together, burn the tubes for a day or two, bench test it to verify that it measures within acceptable levels, box it up, and ship it out; ASAP.

-We used to receive H/T shipments from Paradigm for the Anthem lines that no one had done even preliminary bench-tests on. A couple of the rocket scientists within SFI decided it was more "cost effective" to just send the gear out the door, wait for things to go wrong, (which they often did), and then issue RA#s and service it later.

-Again, the business model is fairly simple: if a projected 2% or 3% of the units are gonna fail, why waste precious time trying to locate those units? As long as the failure rates are under 5%, who cares? Well... boutique hi-end audio dealers and well-heeled audiophiles care. But... you know... it's always easier to NOT do something. It was this kind of leading-edge thinking which, in part, led the original SF into insolvency. By the late '90s... well... I'd better not get into all of the amazing things that were happening at SFI in the late '90s.

-Sorry if your DAC-1 sounded "terrible." Back in the day, there were some phenomenally talented design engineers and bench techs at SFI. The good ones, of course, left and moved on to bigger and brighter things. Some of them are still working within the high-end audio industry to this day. Sadly, there were also a few less than stellar "modders" working at SF. If the unit had been hot-rodded, I can readily think of numerous "geniuses" who might've done the modding.

Cheers... and enjoy the music.


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