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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
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.   
   
guidocorona
4,114 posts
 

Hi @paulburnett, several years ago, I had the original Rowland Capri in my system for about 15 months -- a truly excellent preamplifier, which was a significant upgrade from the ARC Ref3 that I used before. The original capri was audibly superior to Ref3 on most all parameters: staging and imaging, authority and macro/micro dynamics, resolution and extension, harmonic complexity, as well as sweetness and control of treble intermodulation. The only marginal flaw I could detect is a certain shyness of fundamental frequencies in the deep bass... Although Capri had tremendous authority, deep bass notes were a little shy of fundamental harmonics. But at less than 1/3 the list price of Ref3, I could not complain... By contrast, Ref3 bass sounded somewhat muddled.

　

The original Capri was indeed based on the OPA1632, and like all Rowland preamplifiers, runs balanced in class A, with transformer coupled inputs and outputs implemented with Lundahl transformers. I call Capri a preamplifier in stead of a pure linestage, because you can add to it a phono card.... and in more recent times a DAC card instead of the phono.

　

The newer Capri S2 is outwardly almost identical, except for a new display and remote control... However, the circuit has been redesigned, and the OPA1632 has been replaced. I have heard Capri S2 at length at RMAF, and it is sonically significantly enhanced over the original.... The first thing I noticed is that the deep bass shortcoming is totally gone.... Deep bass is, well... Deep, without ever becoming bloated.... And overall Capri S2 is even more musical than the original.

　

You will find more information on Capri S2 at:

　

http://jeffrowlandgroup.com/kb/categories.php?categoryid=210

　

You can download the manual from my Dropbox at:

　

https://www.dropbox.com/s/89p3g48zgh6cava/JRDG%20CAPRI%20S2%20MANUAL%20REVA1.3.pdf?dl=0

　

Feel free to drop me a PM if you like any other info on Capri S2.

　

Regards, Guido


　

Enter your text ...
audioconnection
1,015 posts
 
Guido
Let's  get real
anyone who is running a tube PRE amp into a low input impedance amp should be alert that they won't achieve bliss.
For you to claim op amp Pre amps
out perform a ref tube unit without stating the conditions is misleading 
and wanted to point this out.

Best
JohnnyR




guidocorona
4,114 posts
 

Woops, you are right Johnny, I should have given the context of my repeated comparisons.


I had both Rowland Capri and Ref 3 in my system using the following amplifiers:


Rowland M312: 40K Ohms inpput impedance.

Rowland M625: 10K Ohms

Rowland M725: 40K Ohms

Rowland M925: 40K Ohms.


I have never used Ref3 on lower impedance amps.


The source was the Esoteric X-01 Limited CD/SACD player in all cases.

 

My results were consistent for all linestage / amp combinations. I much prefered the original Rowland Capri over Ref3 in all cases.


Saluti, Guido


guidocorona
4,114 posts
 

One more clarification.... Both Ref 3 and Capri were fully broken in.... REF 3 had a few thousand hours on it, and had fresh but broken in tubes for the SET Winged 6550 in the power supply and the 6H30s... Particularly important in the 6550... It takes this tube about 500 hours to reach full performance, and by 1000 total hours, it starts to sag.


Capri takes about 800 hours to reach maturity... Fresh out of the box, Capri is somewhat flat and blanched, and is easily outperformed by a well broken in Ref3.


After a quick initial comparison with Capri fresh out of the box, in which Ref3 was clearly superior, I did not apply Ref 3 again until completion of Capri break-in, so not to wear tubes down.


G.


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