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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
bifwynne
2,206 posts
 
Jasper ... why are you using the 16 ohm taps? What type of speakers are you driving?
gpgr4blu
1,088 posts
 
Bifwynne:
I was in your camp as of the spring. ARC had been life testing for a very long time, but I had 2,000 hours on my tubes and wanted ARC's blessings for the KT150s in my Ref 150. I called Kal who indicated that life testing was not complete and that ARC had not passed on the combo yet. So I, being the conservative type, ordered a new set of KT120s from ARC. Then after reading all of the plaudits on Agon, I pulled out my KT120s after only 500 hours and installed matching KT150s sourced from Upscale Audio. It is a worthwhile upgrade. I am convinced for reasons that I am sworn not to tell, that the KT150s will not harm my amp now or ever. If I could do it again, I would have purchased the KT150s in the spring. The difference between the KT150s and the KT120s are similar to the upgrade from 6550s to KT 120s. A little better all around, especially in the low end.
I too suspect that the difference between the Ref 150 and GS 150 is purely a matter of form. In fact, ARC engineers were told to, in essence, fit the Ref 150 into the GS 150 chassis. In the interim, the KT150 tube was released so the GS 150 was modeled around it. My intuition tells me that the layout for the circuit in the Ref 150 is the preferred layout and the layout for the GS 150 is driven more by the new chassis configuration than anything else. Is it possible something was learned and gained along the way in the new design? Absolutely. It is also possible that, with a truncated circuit path, we may have lost something as well.
bifwynne
2,206 posts
 
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'.
tsushima1 OP
1,165 posts
 
Bifwynne... ML CLX anniversary, flying in the face of received wisdom I know! However, with certain Genre viz.Girl n Guitar, Jazz, etc.etc, I trade off a smidgen of control in return for the effects that I mention in my previous post.

My own Ref150 is now ready for return, therefore my time with the loaner GS will shortly come to an end with approximately 130 hours on the clock.

Whilst my sonic impressions of the GS are unlikely to evolve much, if any, further that my considerations at the 100 hours mark, I would state tho, having now become accustomed to its 'Retro' look , that I will quite miss its 'easy on the eye' aesthetic styling, precision of diction, and the subtle yet perceivable additional head room it has brought to the system.

Jasper.
bifwynne
2,206 posts
 
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.
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