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PREAMP technology shift? - Class A/ balanced/ dual-mono/ zero feedback vs. op-amp preamps

Hi all,

Even ten years ago, it seemed that the gold standard for solid-state pre's was some combination of the following: Class A/ balanced/ dual-mono/ zero feedback or local feedback. Recently, I'm seeing a range of well-reviewed preamps, from Schiit to Rowland, that use new, high-quality op-amps in their circuitry, to the extent that I wonder if op-amp technology, and chip manufacture in general, has gotten so good that some of the tried and true markers of quality (MOSFETs, Class A circuits) are not in the market except at the highest end, and even then, see also Jeff Rowland. Or is it that manufacturers are looking to less power hungry designs (I know that Rowland was concerned with meeting EU efficiency requirements in its latest designs) and so avoid Class A, for example? Does balanced/ dual mono seem less popular because separates are now less popular than integrateds? Have we reached a tipping point with op amps?

Here's a more focused question. I have invested in a 90s era Aragon 8008BB dual mono balanced amp, but i have an early 90s B&K PRO10-MC that I want to upgrade. Is a Schiit Freya a significant step up, or should I save my pennies for a used, more recent example of the old school: Classe CP500, Pass Labs Aleph or X2.5, or a good example of a newer approach, the Rowland Capri. Speakers are Vandersteen 2CE Sigs. Input impedance of the Aragon is 44 kOhms. 

The tube route is always possible, but I like the idea of a no-fuss, very clean ss, valuing sound stage and detail over warmth, which makes me think I'd be wasting my time with the Freya (any shoutouts for its JFET stage?)

Thanks for letting me wonder aloud!

Paul


paulburnett
georgehifi's avatar
georgehifi
10,312 posts
 
The Freya uses discrete J-fets as it's output stage, the opamps you see are most probably for dc servo duties because it's dc coupled, which even the $$$$$$K discrete preamps have.

From Schiit:
"JFET Buffer
Gain: 1
Frequency Response: 20Hz-20Khz, -0.2db, 3Hz-500KHz, -3dB
THD: <0.001%, 20Hz-20KHz, at 2V RMS
IMD: <0.0015%, CCIR
SNR: >110db, A-weighted, referenced to 1V RMS
Output Impedance: 75 ohms SE, 600 ohms balanced
Topology: Single pair JFET per phase with passive distortion cancellation, DC coupled"

Cheers George
soix
8,995 posts
 
"I like the idea of a no-fuss, very clean ss, valuing sound stage and detail over warmth"

There's a Bryston BP26 for sale here now that nails this in spades.

audioman58's avatar
audioman58
3,952 posts
 
There are many different types . I have had many in my day .Currently I have which is considered the purest preamp type, Single ended . Which has several unique features . It is a Direct Heated Triode type completely Lundahl Transformer coupled 5 transformers,and 3 chokes and the little known 4P1L Vacuum tube 
which is very Linear, plenty of gain to eliminate the need of another tube for additional gain stage like many indirect Heated tubes. A very detailed and 
well balanced tube .it can be a bit microphonic in vibration if the builder does not 
isolate the tubes and isolate and damp the power from the Audio output section properly .modern technologies like relay remote and 63 step Shunt attenuated- Khozmo type. just another  twist for another Audiophile dilemma.

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loungeaudio's avatar
loungeaudio
12 posts
 
You are right that opamps have become very good in this new millennium. 

None of the aspects of circuit design/topology are mutually exclusive.
There are some opamps that run class A natively. Any op-amp can be biased into class A
Tube amps can run class B or Class A/B
Almost any circuit can be designed to run with balanced I/O's or even better yet designed full balanced.
It is also possible to design a circuit in one chassis yet make it run as a dual-mono unit.   
   
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