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Sonic Frontiers SFS-80 Review (Vintage Tube Amplifier)

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Curious, why, with good packing, would such be difficult to transport or do they at some point in aging simply become unreliable in that respect?
It's heavy and fragile. You can expect items to be abused in shipping, not handled with care.
 
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GXAlan

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So basically a good amp as long as you don't expect it to amplify speakers. Maybe it would be OK for headphones?
It still pushes out 80 watts per channel. But tubes aren't about maximum SPLs

As you see from the chart above you, 5 watts gets you 86 dB for a Focal Aria 806 if you're nearfield (5 ft away) or 81 dB with a Revel F328Be at 15 ft away. That's still pretty loud for the type of music. At 50 watts, you are well above limits of safe hearing for long-term hearing.

Curious, why, with good packing, would such be difficult to transport or do they at some point in aging simply become unreliable in that respect?
It's heavy and fragile. You can expect items to be abused in shipping, not handled with care.

Good packaging is very critical and hard to do unless you have a vacuum foam machine that lets you really keep an amp from shifting around with a very customized fit. Today's delivery crews are overworked. Technically 50 lbs should require 2-person lift. But I believe drivers are required to carry 75 lbs. There is also a higher risk that a box, with today's automated sorting systems falls off a conveyor belt or gets crushed by another box as opposed to the shipping volumes that occurred in the 1990’s when this was made and sold.
 

MattHooper

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It still pushes out 80 watts per channel. But tubes aren't about maximum SPLs

As you see from the chart above you, 5 watts gets you 86 dB for a Focal Aria 806 if you're nearfield (5 ft away) or 81 dB with a Revel F328Be at 15 ft away. That's still pretty loud for the type of music. At 50 watts, you are well above limits of safe hearing for long-term hearing.

I even sometimes used an Eico HF81, 14W/side tube amp, with my very low sensitivity MBL (82dB IIRC) speakers. I enjoyed the sound, and it could certainly go louder than I care to listen in my relatively small room, even with those few watts.
 
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GXAlan

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I even sometimes used an Eico HF81, 14W/side tube amp, with my very low sensitivity MBL (82dB IIRC) speakers. I enjoyed the sound, and it could certainly go louder than I care to listen in my relatively small room, even with those few watts.

Nice, and I bet those MBL’s benefit a lot from room reflections!

@oscar_dziki. Think about an audiophile master recording made by a “singer songwriter”. The human voice and maybe a guitar is all you have. At 82 dB, 2 watts per channel into a stereo pair of speakers with a little bit of back wall reflection gets you to more than 85 dB. THX reference level is 85 dB with 105 dB peaks (and 115 dB for the sub).

No one ever says their tube amps are awesome for Taiko drums (although the low damping factor can alter bass). Tube amp coloration is probably strongest in the vocal range.

It’s easy to overestimate the power requirements for music at casual listening and the exponential power requirements needed to hit those dynamic peaks in a large orchestral piece.
 

restorer-john

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That's a bit like asking 'would you ride an elevator powered by a Benchmark AHB2 power amp'? Obviously not. Wrong use case.

I’d ride an elevator powered by a big Krell or a vintage Perreaux. At least they wouldn’t shut down or go into protection if 10 fat people got in…
 

Labjr

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Nice review! I've always thought Sonic Frontiers was nice looking equipment and appeared to be well made. I'm happy to see it measures reasonably well too.

I auditioned some of their gear back in the day when dealers would ship demo units for you to listen in your system.

I don't understand why some people join the discussion just to criticize vacuum tubes. You don't like it then don't buy it.
 

restorer-john

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I don't understand why some people join the discussion just to criticize vacuum tubes. You don't like it then don't buy it.

Jealousy. They've never basked in the warm glow of a vacuum tube amp in the dead of winter.
 

DMill

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Stellar review and thank you from all who still dabble in tubes once in awhile. I suspect there are other decent measuring tube amps out there. The biggest hurdle in uncovering them seems to be shipping. I’m not qualified or motivated to perform this type of testing, so cost and damage is a major concern.
 
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GXAlan

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Stellar review and thank you from all who still dabble in tubes once in awhile. I suspect there are other decent measuring tube amps out there. The biggest hurdle in uncovering them seems to be shipping. I’m not qualified or motivated to perform this type of testing, so cost and damage is a major concern.

I am a hobbyist too. I went from never having tested an amplifier myself to testing nearly my entire collection in a few days. As long as you have some basic high school physics recollection of wiring things in series versus parallel, it’s pretty easy.

The tools that exist it today make it simple.

Damage is a real concern though — nothing crazy, just electrical shorts being the risk in my opinion or blowing the E1DA by having the volume too high.
 

fpitas

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Damage is a real concern though — nothing crazy, just electrical shorts being the risk in my opinion or blowing the E1DA by having the volume too high.
I'll add, shorting an SS amp is bad, but an open on the output of a tube amp is nearly as lethal.
 

Chr1

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I have two amplifiers with valves in my collection which I love. Both power amps. A Lazarus H-1A valve/mosfet hybrid and a VTL ST-85. I have sensitive speakers and they work well. I will start using them again when I require additional warmth in my living room.
I have gone "eco" and use a Technics SE-A1000M2 in the summer as it uses less power...
(Plus it's got a pair of killer VU meters.)
 

Labjr

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I have one system with set of Wavelength 300B mono blocks and tube preamp from thirty years ago. I know they don't measure like a push-pull amp but they sure sound good. I don't use them much these days but I wouldn't sell them because they were built with parts that are mostly no longer available. I also have an early 60's Fisher 500C receiver. It sounds great too but needs restoration work. And it's all made in USA.
 

Murray A

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This AP System One + DSP was used during development of the SFS-80. It was later relegated to final test position for tube selection and final adjustment of all Sonic power amps, after purchase of an AP System Two.
L1010636.JPG
 
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GXAlan

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This AP System One + DSP was used during development of the SFS-80. It was later relegated to final test position for tube selection and final adjustment of all Sonic power amps, after purchase of an AP System Two.

wow!! We have the former director of design and product develpment for Sonic Frontiers?

tagging @amirm

Can you share any war or engineering stories of this tube design? We have seen how the VTA-70 does much worse than a plain Dynaco but this SFS-80 with presumably good tubes really knocks it out of the ball park and beats even expensive high end AVRs :)
 

Murray A

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For grins, here is the performance of the Mac MC3500 at 10 watts with some signal averaging...

MI350 10 watts 8 ohms.png


and at 350 watts, no averaging.
MI350 350 watts 8 ohms.png
 
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GXAlan

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Imterestingly, even though it was a sighted comparison, Paul from PS Audio admitted that his fancy amp in development at the time lost to Arnie Nudell’s Sonic Frontiers amp!

That MC3500 is incredible. What tubes are being used?
 

Murray A

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Imterestingly, even though it was a sighted comparison, Paul from PS Audio admitted that his fancy amp in development at the time lost to Arnie Nudell’s Sonic Frontiers amp!

That MC3500 is incredible. What tubes are being used?
8 x 6LQ6. The performance of the Mac could be world class with DC on the filaments in the driver stage, lowering of the power transformers high leakage current into the signal ground and a mod to fully balance the input stage. The rather poor SNR is actually the amplfier's leakage current appearing and mixing at the signal output of the APX555.
 

pseudoid

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I don’t know if this actually measures better than a MC275/MC2102. From what I understand the 12ax7/12at7 combo is even better than the 6DJ8.
Then the question is how good something like an Audio Research, current production amp can perform.
Then the next question is 'would it be worth testing SFS-80 shod with KT88s'?
ThanX, @GXAlan.
 
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