Sonic Frontiers SFL-2 Preamp

braxus said:
Well I've been in contact with the seller and also some techs. The seller had no clue there was internal issues with the pre he sold me. Of course he is going to say that, but he claims he wasn't dumping the unit. I'll let it go. Can't cry over it now that its in my hands. I just find it hard no one noticed the Solen caps issues while it was in his hands. But he may have not been very tech savvy either, other then the fact he did swap the tubes in this thing when he owned it.

The two techs stated Solen caps don't like heat, and I've been told this preamp looked like it was not in a well ventilated area, causing heat damage with the internal parts. I've been told to expect $300-400 to fix these issues and replace needed parts. Then it should be in the state I was expecting it to be sold to me to.

When I finally complete building my main system, I may at some point get a new rack made up. My current rack isn't making the best space available for the components I'm using. Shame to get rid of the rack I have now, because its well built (custom made) and cost a lot to have made up. Any new rack will most likely be between $700-1000 to get a new one made up.
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Have you looked up the temperature rating on Solen caps? Recommend you check that out. Usually caps have decently high temperature ratings, like 85C which is mighty hot. I would doubt that your unit saw that kind of heat.

I checked data sheet. -55C to +85C

Pretty forgiving. Those caps are in the PS Unit which does not see the internal heat that the tube section does.
 
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Stu I did eventually contact him previously. Didn't feel the need to ask him about this though.

Both techs I talked to state the Solen caps in the tube section have heat damage and that those caps don't like any sort of heat like even a soldering iron.
 
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braxus said:
Stu I did eventually contact him previously. Didn't feel the need to ask him about this though.

Both techs I talked to state the Solen caps in the tube section have heat damage and that those caps don't like any sort of heat like even a soldering iron.
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Bump
 
I gave this preamp some more listening while it waits to be taken in for repairs. It sounds good, but it didn't retain the sound my Rotel did with the music sounding like it fills the room, not coming from the speakers. Since this is the second unit I've had that retained this quality, I'm blaming that on the design of this unit. I'll wait till I get it repaired before making final judgement on it. I still plan on getting that YBA preamp because of this sound fault with the SF pre. I'll just keep the SFL-2 and use it in my secondary system if the YBA sounds more like what I like. I thought for sure tubes would be noticeable in the sound I get, but I haven't noticed anything yet that makes me say- yes this was a worthy buy.
 
braxus said:
I gave this preamp some more listening while it waits to be taken in for repairs. It sounds good, but it didn't retain the sound my Rotel did with the music sounding like it fills the room, not coming from the speakers. Since this is the second unit I've had that retained this quality, I'm blaming that on the design of this unit. I'll wait till I get it repaired before making final judgement on it. I still plan on getting that YBA preamp because of this sound fault with the SF pre. I'll just keep the SFL-2 and use it in my secondary system if the YBA sounds more like what I like. I thought for sure tubes would be noticeable in the sound I get, but I haven't noticed anything yet that makes me say- yes this was a worthy buy.
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What amp are you driving with the SF preamp? What is that amps input impedance and what is the output impedance of the SF preamp? Was the Rotel a SS preamp?
 
Amp being used with this pre is a YBA 2 HCDT. I have heard comments about YBA have mismatches, but I wonder how that would cause a sound depth problem? That said my Rotel did very well with the YBA and yes the Rotel is solid state.

Here are the specs of the SFL-2 Pre: (YBA 2 pre is at bottom line of this selection)


[TD="class: speci_left"]Frequency response :
[/TD]
[TD="class: speci_right"]20Hz...100Khz (± 0,5dB ; 100kOhm load)
[/TD]

[TD="class: speci_right speci_marg_bottom"]> 350 Khz (-3dB)
[/TD]

[TD="class: speci_left"]THD :
[/TD]
[TD="class: speci_right"]< 0,1% (20Hz...20Khz ; 1V output)
[/TD]

[TD="class: speci_right speci_marg_bottom"]< 0,03% (typical ; 1Khz)
[/TD]

[TD="class: speci_left"]Gain :
[/TD]
[TD="class: speci_right"]22dB @ 1Khz (single-ended)
[/TD]

[TD="class: speci_right speci_marg_bottom"]28dB @ 1Khz (balanced)
[/TD]

[TD="class: speci_left"]Residual noise :
[/TD]
[TD="class: speci_right"]120µV unweighted (balanced out ; volume @ 12 o'clock)
[/TD]

[TD="class: speci_right speci_marg_bottom"]-85dB @ 2V RMS output
[/TD]

[TD="class: speci_left"]IMD :
[/TD]
[TD="class: speci_right"]< 0,05% @ 2V output
[/TD]

[TD="class: speci_right speci_marg_bottom"]< 0,03% @ 2V output (balanced)
[/TD]

[TD="class: speci_left"]Input impedance :
[/TD]
[TD="class: speci_right"]50kOhm (single-ended)
[/TD]

[TD="class: speci_right"]100kOhm (balanced)
[/TD]

[TD="class: speci_left"]Output impedance :
[/TD]
[TD="class: speci_right"]160 Ohm @ 1Khz (single-ended)
[/TD]

[TD="class: speci_right"]320 Ohm @ 1Khz (balanced)
[/TD]

[TD="class: speci_left speci_marg_bottom"]Minimum recommended load :
[/TD]
[TD="class: speci_right speci_marg_bottom"]10kOhm
[/TD]

[TD="class: speci_left"]Output voltage :
[/TD]
[TD="class: speci_right"]30V RMS max. (s-e ; 100kOhm / 100pF load)
[/TD]

[TD="class: speci_right speci_marg_bottom"]60V RMS max. (bal ; 10kOhm / 1000pF load)
[/TD]

[TD="class: speci_left speci_marg_bottom"]Maximum input :
[/TD]
[TD="class: speci_right speci_marg_bottom"]2,5V RMS (volume fully clockwise)
[/TD]

[TD="class: speci_left"]Stereo separation :
[/TD]
[TD="class: speci_right"]70dB @ 1Khz (single-ended)
[/TD]

[TD="class: speci_right speci_marg_bottom"]75dB @ 1Khz (balanced)
[/TD]

[TD="class: speci_left speci_marg_bottom"]Tubes :
[/TD]
[TD="class: speci_right speci_marg_bottom"]8x 6922 (6DJ8 type)
[/TD]

[TD="class: speci_left"]PC :
[/TD]
[TD="class: speci_right"]75VA (standby)
[/TD]

[TD="class: speci_right"]135VA (max.)
[/TD]

[TD="class: speci_left"]Dimensions :
[/TD]
[TD="class: speci_right"]48 x 11,5 x 33cm (each chassis)
[/TD]

[TD="class: speci_left"]YBA 2 Preamp:

[/TD]
[TD="class: speci_right"] Description: Solid-state, full-function stereo preamplifier with five line inputs, one phono input, and one tape loop. Frequency responses: 5Hz-400kHz, -0.2dB, line; 5Hz-60kHz, -0.2dB, phono. Input sensitivity: 2mV RMS (MM phono); 150mV RMS, line, both for 1V output. Input impedance: 47k ohms, MM phono; 100k ohms line. Output impedance: ±20 ohms. Maximum output: 8V RMS. RIAA overload: 2.2V RMS (frequency not specified). S/N ratio (ref. 1V output at 1kHz): 100dB, line; 90dB, MM phono. Absolute polarity: inverting.


[/TD]
 
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And here is the YBA 2 HC amp specs:

Description: Dual-mono solid-state power amplifier. Maximum power output: 70W into 8 ohms (18.5dBW), 140W into 4 ohms (18.5dBW). Frequency response: 5Hz-80kHz, -3dB. Input sensitivity: 120mV RMS for 1W/8 ohms, 1.1V RMS for rated output. Input impedance: 27k ohms. Output impedance: 0.02 ohms (damping factor quoted as 400 at 100Hz). Risetime: 3µs at 10kHz. S/N Ratio: 100dB (reference and conditions not stated). Power consumption: 100VA idling, 1000VA at full power.

Here are some specs on my Rotel Pre:

Input impedance/sensitivity -Line 18 kOhms/150mV, Output impedance- 100 Ohms, output voltage 1V
 
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braxus said:
Gepetto- anything in the above specs stand out or is it pretty standard stuff?
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Pretty standard stuff, the YBA amp input impedance looks a little lower than typical (most in the 47K input impedance range) and the output of the SF preamp is much higher than SS preamps typically are (< 10 ohms) but 130 ohms is not bad for a tube rig. Expected it to be much higher than that.

Nothing stands out from a spec perspective.
 
I got an email from my tech here today (and later talked to him in person). The repair on my SFL-2 is cheaper then we had expected. Around $270 with my estimate fee taken off that price. What he is doing is replacing some caps in both power supply and the preamp itself, some resistors, the tube sockets, the one broken switch, plus he will resolder a lot of joints, etc. He said replacing those Elna caps with Panasonic polypropylene units will improve the sound and return the lost dynamics currently with the unit. Tubes are in good shape. So I should be picking the unit back up in a months time.

Thing is it currently doesn't have a system to get used in at the moment. I relegated to main system to the YBA pre, plus the secondary system is using my Rotel. I have enough components to get a third system going, but don't have anywhere to put it. Will have to wait till I move.
 
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