Audio Research GS150 Musings


Good day my fellow ARC Agaricus Bisporus.

In light of the relative ambivalence that seems to have descended upon ARC's latest, and Should we to believe the "word' on the street, greatest stereo amplifier, I thought that I would initiate this thread for the most part as a vehicle whereby any early adopters of this particular model might comment upon their considerations of the amplifier thus far, and hopefully utilize the same, as a place where they may log their considerations as they journey through the Roller Coaster ride that is ARC break in.

I hope that I will be excused for the somewhat laxidaisic cut n pasting that follows, however I plead the 'Humungous Hangover' defence!

" For my part I have listened to the same GS150 at 60 hours, then with 166 hours on the clock, and whilst there were signs of an opening up in the midrange, I felt the amplifier to to be rather 'Tight', and still a Tad constrained in some areas of tonality, texture and harmonics, particularly on acoustic strings.

Whilst considering comment made thus far in respect of the KT150, I was expecting to be impressed with the lower registers, even at this point in what can be something of a roller coaster ride where break in of ARC is concerned, however this particular GS is still quite some way off, in reproducing the gravitas evident in for example, Der Ring des Nibelungen, as imparted by my Ref150 even at 300 hours on the clock.

However! Even at this early juncture, It is in the upper mid-range, ascending, where the GS has ,for me, impressed the most. The retrieval of filagre micro detail is quite excellent, the GS seeming to impart additional 'air' and light with an effortless extension to the very upper registers. Smooth, clean and accurate, whilst remaining quite organic and utterly convincing in nature.

Jasper."
tsushima1

Showing 8 responses by bifwynne

Pulled the HI FI News review and clipped some pertinent comments:

"The GS duo not only looks much better
it also sounds way better than the ARC REF 5E/150 combination with **KT120 valves installed** (which
are congested and closed-in by
comparison). The GSPre/GS150 won
hands down, I must say. As well it
should, considering that it costs
almost double the price."

***

"Audio Research says its Galileo Series
is not intended as a replacement for
the existing REFs, and will coexist
with the rest of the ARC product
range to provide an alternative
aesthetic as well as a platform for
new ideas. **So, before REF owners
feel tempted to upgrade lock, stock
and barrel, I’d urge them to first
audition an ARC REF150 with KT150s
in place of the stock KT120s.**"

Warren Gehl comments:

"So is the GS150 really just a
REF150 with new looks? ‘As with
many designs from Audio Research,
the GS150 is an evolutionary step
from the REF150’, explained
Warren. ‘For while the two amplifiers
share many common aspects, **there
have been numerous parts and
layout changes which affect the
sound.**"

("**" denotes my emphasis.)

Not to bore all with the HI FI lab report, I am very familiar with the Ref 150 specs and lab tests. The two amps test almost identically. Warren Gehls states that "numerous part ... changes" affect the sound. I can count at least 5 changes. Four (4) KT-150 tubes and a slightly different output tranny (minus 1 tap). What other parts were changed ... better coupling caps?? Better resisters? Better front end power supply?

The authors encourage current Ref 150 amp owners to try the KT-150s. ARC says we can't do that yet. But I wonder what the authors would say if they compared the Ref 150 with KT-150 tubes and the GS-150?

I smell a marketing trick: a Ref 150 with a pretty new skin and much better power tubes. I have a funny feeling that loading my Ref 150 with KT-150 tubes will yield a MAJOR improvement. Maybe almost as good as the GS-150. But ARC says NOT YET!

P.S. Not much said about the GS-Pre other than the phono stage was not as good as the Ref Phono 2 SE.

Given where I hold with my system, I am looking for tweaks and changes that have a high benefit to cost yield factor. The DEQX PreMATE is one such change. I think KT-150s will be a another. Next on the list is AC power distribution. And so forth.

If there are any brave souls who have slipped KT-150s into their Ref 150s, please share your comments.
Jasper ... why are you using the 16 ohm taps? What type of speakers are you driving?
Gpgr4blu ... couldn't agree more. We may be recycling the same inside news from the same person that the GS line is targeted for the Chinese/Asian market, but I heard that bit of information too. I still find it hard to understand ARC's pricing/value proposition for the GS line. Short of a major "Ref 10" type redo, which is based on the 40th Anniversary linestage on steroids, I just don't get it.

IMO, I would not part with the kinda cash ARC is asking for the GS line, even if it could levitate spoons and bend them in mid-air.
Thanks Gpgr4blu .... then why the huge price increase in the GS-150? Where's the value? Is ARC asking its loyal customers to pay for just aesthetic and silly meters?

If so, William Z Johnson is rolling.

I hope that ARC publishes a tech explanation on its web site that explains the tech differences between the Ref 150 and the GS-150 that justifies the huge price increase. I would expect a wholly new everything.

If this is just about aesthetic, ARC's good rep takes a big hit IMHO. And I am a fan. Just sayin'.
Jasper,

What does the impedance curve of the ML CLX look like, especially in the critical power range (50 to 750 Hz)?

The 16 ohm tap has the highest output impedance of the 3 taps. As a result, if there is an impedance "bump" at a certain frequency range, the Ref 150 will produce more power at the "bump" and the SPL will be correlatively augmented. By contrast, the 4 ohm tap has the lowest output impedance of the 3 taps (approx .6 ohms I believe) and will produce the smallest power variance as a function of frequency.

My speakers have an impedance curve that looks like a roller coaster ... but significantly, the impedance curve in the critical range of 60 to 500 Hz ranges between 4 and 6 ohms. I happen to use the 4 ohm tap. That's a good match for the amp because the bulk of the power demand is in that frequency range. Also, the 4 ohm tap has the highest damping factor .... therefore better control of the woofers

But look ... use whatever tap you think sounds best. You won't hurt the amp. Having said that, the amp's capacity to deliver clean power in the "power range" (i.e., 50 to 750 Hz) may be somewhat compromised if the impedance match between the speakers and the amp (via it's primary windings) is not be optimal, i.e., much lower than 16 ohms.

I'm sure Al (Almarg) can chime in and clean up my attempt at a technical explanation.
P.S. Correction to my post to Jasper. What I should have said is that the output voltage variation (not power) is tightest off the 4 ohm tap and therefore the amp performs more solid state like ... that is like a constant voltage source. This corresponds to the fact that the output impedance (about .6 ohms) of the 4 ohm tap is the lowest of the 3 taps.

So, if the ML speakers were voiced to be driven by a low output impedance SS amp, the 4 ohm tap might (??) produce the flattest frequency response, assuming the MLs spec flat as a threshold matter.

But having said that, as Al said, the ultimate output may sound better at a higher ohm tap based on listener preferences (i.e., preferred acoustic coloration) and/or the impedance match (or maybe better said, mismatch) of the amp and speakers especially if the amp is called upon to produce large amounts of power.

As Al said, generally, most amps are not called on to deliver huge amounts of power in the treble frequencies.

In the end, go with what ever sounds best.

BIF
Jasper, I'd appreciate Al's thoughts, but looking at the impedance graph of the ML's, they look like a giant capacitor. Notably, in the all critical power region (50 to 750Hz), impedance is quite high.

The graph is hard to read, but it looks like impedance is between 10 to 15 ohms in the frequency spectrum where the amp is called on to deliver power. It wouldn't surprise me that you like the sonics off the 16 ohm taps. As suggested, you might want to try the other taps to see which taps sound best.

For example, you might find bass to be tighter and punchier if you use the 8 ohm taps ... I expect a high DF. The 4 ohm taps might give you the tightest bass and the high end might be less bright

Al, any comments?