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Sonic Frontiers SFL-1 tube choice

B

bribaby

New Member
I have a Sonic Frontiers SFL-2 tube/hybrid preamp (that I love) that plays music really loud no matter what amp I use. I've used 75-watt mono blocks and I've used a solid state amp putting out more than 300 watts. When I get everything going, whether the source is CD or iPod or tuner I barely get the volume knob off the bottom before things get really loud. Could it be an issue with the 6201 tube I'm using? The 6201 seems (according to the all-knowing Internet) to be an equivalent to the recommended 12AT7. Any thoughts?
 
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RCA black plate 6201's, GE 6201's, or Sylvania 6201's would probably be a good choice.
What are you using now?
 
I thought SFL-2 used 6922.

As well, presuming correct tube type installed, SFL-2 has 22dB gain. That's fair bit of gain in a preamp, and likely explains why it's "loud".

Still question on the tube type though.
 
Oops... Just noticed my typo. I have an SFL-1, not SFL-2. Also, the logo on my tube is pretty unrecognizable but from the color and general shape I think it's a JJ.
 
SFL-1 has 20dB gain. Won't require turning much on the volume to get loud, particularly if the source tends to be on the hot side, as CD players often are.

Likely nothing technically wrong, just what happens with that much gain.
 
What speakers are you using? Speaker sensitivity has a huge effect on how loud they play at a given volume setting.
 
Of course, but with 20dB gain it's going to require very little rotation of the knob to increase volume. That's the crux of the problem.

Some relief could be had by using attenuators on the inputs.
 
I might put them on the output side of the preamp, may be quieter.

Either way changing tubes isn't going to make an appreciable difference in the gain
 
I use a Mullard M8162. Out of a number of tubes I have used that is the one I liked the best. Cheers
 
I loved that preamp. The nicest tube I used according to my ears was a Dutch Amperex 6201 with the pinched glass waist. It was wonderful in that SFL-1
 
I just picked up a NOS Mullard at7 from Upscale. Sounds excellent in my SFL-1. Was considering moving the jumper to try a 6922 but I think this is the best tube I've used in it.
 
I have an Assemblage L1 that is supposed to basically be the SFL1 with a couple upgrade changes. Made by the same designers as the SFL1 I believe..Parts Connexion guys. They offered this as a kit & pre built..with a "Signature" upgrade path listing all the signal resistors to improve & power supply upgrades.

I just pulled mine out to do a couple changes internally. I bought a nice relay volume control & I'm thinking of making this unit remote volume controlled, change some signal resistors, & a pair of the only Multicap PPFX's in it. Lack of remote is really the only reason I don't use it as often as other preamps. But I do love the sound of this old 90's unit.

I have used the usual suspects of good 12at7's in it & I'm actually a fan of that tube type. But I normally keep it switched to the 6922 types. A '63 Phillips Miniwatt SQ E88cc gives me a very resolving presentation with beautiful vocals. Bass isn't the strongest but there are compromises with everything.

12at7's I've tried seem to have a smidge more "warmth" than the 6922 types. I like the NOS Mullards as well..but then I lose a little more inner detail vs the Miniwatts. IMG_20251216_211755657_HDR.jpg
 
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