2. amps-preamps
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Pass Labs versus Jeff Rowland, Audio Research

As I am considering replacing my trusty pair of Jeff Rowland 7M monoblocks, feeding a pair of MagnePan IIIAs, I am looking at both the current Jeff Rowland lineup, as well as at the latest incarnation of the Pass Labs X series, dubbed the X.5 series, and some Audio Research models.

In the Rowland lineup I am considering the 501 monoblocks, or the 302 stereo amp, while I have already determined first hand that the smaller 201 monoblocks do not drive the MagnePan IIIA pair adequately.

In the Pass Labs lineup I will consider the X-250.5 (already released), the X-350.5 (just out of engineering), and the upcoming X-600.5.

From Audio Research I already discarded the otherwise extremely lovely VT100 as just slightly underpowered for the Maggies, but will consider the VT200 stereo, the new VSM220 monoblocks, as well as the VTM200 monoblocks.

The rest of my system consists of EAD T1000 CD transport and EAD DSP7000 Mk3 (these likely to be replaced by Esoteric X-01, and an Audio Research LS2B.
I most listen to classical, and within it more to solos and small ensambles than to large orchestra.

I'd value all opinions! In particular any comments concerning the relative merits of the newest Pass amps vs the other brands would be very appreciated.
According to Pass and to those dealers that have already the new X.5 models, these new boxes have a more refined and detailed sound than the old X models, and a fuller fleshed-out midrange. But, how do they truly stack up to Rowland and Audio Research?
guidocorona
didactically
142 posts
 
YOu must be fickle, or suffering the audio 7 month itch. Get some new recordings, or buy a new shirt. Or better get something nice for your wife :-) That can be even more rewarding :-)
sogood51
2,157 posts
 
Did they upgrade the power supply in the new Pass amps? If not and you go with the Pass...get the biggest model you can swing ($$$).

We have a member of the Apogee speaker forum who had the Pass-600 mono's with his Apogees and they were somewhat light in slam but over-all very good sounding in every other department.

Dave
guidocorona OP
4,298 posts
 
Thanks Dave, the info on the X.5 internal changes are still scant. The best info I have found so far seems to suggest changes in the power supply have been included. Here is an extract from an ad for the x-250.5 on audiogon: ". . . addition of single-ended Class A bias, high speed fast recovery rectifiers in the power supply, and some changes to the front end circuitry have been made."
But we won't really know until someone posts a detailed report. have reasons to believe that such changes will be migrated upwards in the product family. I can only guess that the high speed rectifiers may yield improved performance on transient envelope.
And yes, I am tentatively oriented towards the future x-600.5 monoblocks as the MagnePan IIIAs are 4 Ohm bipolars with a low 83Db efficiency.

But transient response is not all that my admittedly fickle self is seeking in this--not just 7-month but long 7-year itch--but also detail, sweetness, delicacy, microdynamics, and overall glow.
In other words, the new am must be the one I want to marry, not the one which I would date once, to yield raving excitement for a hot and stormy one-night-stand.
sogood51
2,157 posts
 
Sweetness, delicacy and overall glow were all there, Pass is of the highest order in SS amps...dynamics were limited with the older model with his very hard to drive Apogees. He moved on to an digital amp..first a 250 watt (I think) eAR and is now using H20 mono-block digital amps. I guess these are also 250 watts per and are very tube-like with SS power quality for the bass.

I am still using my old Krell Ksa-250 to drive my Apogee Duetta Signatures so take my input for what I read...I have tried none of these amps with my speakers.

My understanding is that Jeff Rowland also has a digital amp out which also uses this same B&O ICE technology in it's design.

Dave
muralman1
1,527 posts
 
That's me sogood is talking about. I like what I have now, H2O Signature monos, so much more, it ain't funny.
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