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Old 22nd June 2007, 06:28 AM   #1
S Chew is offline S Chew  United States
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Talking Gb150d

Mark, a 12 year old neighbor wandered into my garage while I was testing the GB150 and made an unsolicited comment: "That really sounds good, better that anything I've ever heard." Big deal! A 12 year old is hardly a credible audio critic..., but he probably possess two things most of us lack: untainted objectivity, and a flat auditory frequency response, i.e., normal hearing.

First impressions aside, the honeymoon period was over 8 weeks ago, but what still amazes me is that the fun and excitement has not warn out. I still leave the listening room with a smile and a insatiable appetite for more.

This amp has special qualities which I will attempt to characterize. It's different from the dozens of amps I've owned and built over the years, including tubes. The GB150's speed, attack, and ability to follow dynamics are incredible. I have never heard a tube amp even come close in this regard (incuding the BAT 100W tube monoblocks). Consequently, crescendos remain articulate, impacting, and realistic contrast to the clamor of lessor amps that typically forces me to turn down the volume or eventually suffer from listening fatigue. The speed brings out other nuances. The sudden explosion from dead silence of a clarinet or a vocalist attacking a bar is startling. You will literally jump from your seat.

The tonal quality of the GB150 is natural; it's tonal balance is neutral. There is no mosfet mist reminiscent of the old B&Ks or solid state blear present even in some of today's high priced amps. Here's a simple way to test the tonal quality of your amp. Listen to the recording of a snap ( i.e. Livingston Taylor's Grandma's Hands ). On many amps, the snap will sound more like a clap, as the amp ignores the decay resonance that emanates through the channel created by the palm and last two fingers; that gives the snap it's characteristic sound. The GB150 is able to capture this and other subtleties that provide a sense of realism.

The ultimate test for any amp, of course, is to recreate the grandeur of orchestral music in the space of your living room. (Jazz is much less challenging. ) This is a duanting task, where many amps fall short, because either it lacks a wide sound stage, depth, air, low level detail retrieval, or harmonic balance. In this respect, Greg Ball's SKA has not failed. I have even found opera captivating ( Renee Flemming, Bel Canto ), whereas, not too long ago, I would never sit through any operatic performance.

So, with all the superlatives, what are the negatives? The design is sensitive to layout, and hum can be a problem, if the documentation is not carefully followed. With the proper grounding scheme, however, the GB150 is dead quiet. The bias is sensitive to temperature, as is usually the case, and with the SKA there is an inverse relationship. With a cold heat sink, the start up bias can be quite high and it may take 15 or more minutes to equilibrate, depending on the mass of the heat sink and the ambient room temperature. Thus the need for a warmup period. I constructed a pair of four channel amps to drive the Orions. Experimenting with a number of mods, I finally built the 8 modules with soft recovery fast diodes along with extensive bypassing in the power supply as well as C6 and C7, the zener mod, DC coupling, and input impedance matching. It is hard to say what improvement was gained with these changes as compared to the stock GB150, but I am totally satisfied with the final product. It sounds damn good, so no need to add more tweaks or to look elsewhere.

With all said and done, I would have to agree with my little neighbor, Mark, the GB150D is "better than any (amp) I've ever heard".

Stan
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Old 22nd June 2007, 10:03 AM   #2
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Old 22nd June 2007, 10:12 AM   #3
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