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In Reply to: RE: Easier said than done -nt posted by Feanor on June 05, 2022 at 10:50:14
Same .002 THD+N @ 1kHz (using zero feedback) per Stereophile review:
Follow Ups:
To be sure, the SP20 adds a phono preamp, etc.I'm not sure what Reina means, though, when he says, "The result is the SP20 ($9000), a fully balanced, pure class-A preamplifier that uses no overall loop negative feedback."
Is "no overall" feedback the same as Zero feedback?
Meanwhile the Athena claims THD+noise an order of magnitude lower than the SP20, i.e. 0.00012% vs. 0.002%. Per 6Moons they claim "Low", not zero, feedback. But I'll wait for Amir to the measurements to confirm the Denafrips' claims, (I might have a long wait).
Anyway, I don't suffer from 'feedbackphobia' to the extent you do.
Dmitri Shostakovich
Edits: 06/06/22 06/06/22 06/06/22 06/06/22 06/06/22
I use measured specs [from ASR, Stereophile, etc] mainly as a starting point to weed out obviously defective products. I don't suffer from op-amp or feedbackphobia but I do look at the overall design to see where the designer's head is, but in the end its the sound that counts most to me.All three ARC "tube" preamps that I once owned suffered from solid-state-itis. To be expected I guess from what were essentially JFET solid-state preamps with a tube buffer bolted on the output. Additionally these all used $2.00 IC chip volume controls. You have to move into the large five figure price range before ARC gives you a better volume control. I'd much prefer a good ALPS pot or better yet, discrete resistor volume control. Many preamp manufacturers do too, including all of the 'high-end' established brands I listed below. As they say, the volume control makes or breaks the preamp.
If these ARC "tube" preamps sounded like tubes to me, I wouldn't be so critical of them. But they didn't. To me a REAL tube preamp doesn't just bolt a couple tube buffers onto the output stage as ARC does. BAT doesn't do this. CJ doesn't do this. Aesthetix doesn't do this. Manley doesn't do this. VTL doesn't do this. VAC doesn't do this. Cary doesn't do this. Etc. Again, you have to move into the large five figure price range before ARC gives you a REAL tube preamp with hopefully a better volume control. And I would hope that these five figure ARC tube preamps sound like tubes.
Edits: 06/06/22
That is Sonic Frontiers Line 1 SE+ which has no s/s stages. But, OPPS !! , it does have PGA2311 volume control chips that have op amps, and very robust S/S power supply.
It's very transparent and very neutral but not very tube-like. I'm sure morricab would hate it.
Dmitri Shostakovich
BAT makes a very good preamp. Aesthetix too. Not as big a fan of CJ or VAC pres.
Check these out though for something different:
https://aries-cerat.com/incito-product-page/
https://aries-cerat.com/incito-s-product-page/
Very low distortion, tube rectified, transformer coupled output triode preamps.
Incito has resistor ladder volume control Incito S has transformer volume control
Most preamps have multiple stages with a unity gain output buffer being the final one. The objective is lowering output impedance and the 6H30 is well suited to that function. Different companies choose tube or SS for either gain or buffer.VTL and PS Audio take the opposite approach of the SP20 by *bolting* a MOSFET buffer to the 12AX7 or 12AU7 based gain stage for the 7.5 or BHK Signature .
And I would hope that these five figure ARC tube preamps sound like tubes.
My goal is for components to sound neither *like* tubes nor SS.
Edits: 06/06/22
(at 4X the cost)Completely hand assembled in Minnesota vs automated assembly in China.
Is "no overall" feedback the same as Zero feedback?
Local, aka "degeneration" vs loop feedback between multiple stages. Explained by Nelson Pass
Anyway, I don't suffer from 'feedbackphobia' to the extent you do.
Avoidable with small signal circuits and useful in low values (15 db) with power amps for overall stability and lowered output Z.
Edits: 06/06/22
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