Vacuum Tube Logic Stereo 120/50: A rare breed and sound
I first saw the Vacuum Tube Logic (VTL) 120/50 at Sound Goods in Sunnyvale, California. The store had one of those gigantic sales events that people camp out for. (Yes, this lapse of sanity happens.) It was one of those rare experiences. I lined up for three hours to purchase a pair of Mono 100. Through some mishap, I also got to try the VTL 45/45 for about a month while the store ordered my Mono 100. With my previous ownership of a 50/50, you could say I have had a handful of VTL amps.
Anyhow, the 120/50 is a sight to behold with those curvaceous 807's and wires attached to the top of tubes. The words "unusual, esoteric, and adventure" come into mind. I was so intrigued that I pondered the possibility of purchasing one just for the pleasure of owning an unusual component. I banished that thought with the refrain that I will find it one day at a much lower price in the classifieds.
Brief history
Vacuum Tube Logic of America (VTL) is a manufacturer of tube components that has made a number of contributions to the industry in its short tenure. David Manley was the Designer and Head of the company for many years. He was mainly responsible for the design of favorably reviewed and classic amps such as the VTL 75/75, 90/90, Mono 100, 225, and 300. David Manley has since formed another company, Manley Laboratories. VTL is presently managed by his son, Luke Manley, and principals from the Sound Goods audio store.
Technical description
The 120/50 tube stereo amplifier employs four 807 tubes in parallel push-pull and four 12AT7WA/6201 input-driver tubes to deliver 120 watts per channel in AB1 tetrode mode. It can be instantly switched into pure Class A triode which yields an output of 50 watts per channel.
VTL used to come in one of two sizes-compact or deluxe. Both have two protection bars, not to be mistakenly used as handles. The deluxe is larger in size. Its dimensions are 19"W by 8 1/8"D by 10"H. The 120/50 comes in the deluxe size, and weighs 50 lbs.
The protection bars and transformer covers are chrome plated, a nice contrast from the predominantly black metal package.
A new musical adventure
As you will note, we recently moved. So, I took some time to familiarize myself with the sound of my reference system in our new listening room. I felt this necessary to be able to fairly assess and evaluate other equipment. In fact, this delayed the publication of this issue BUT I felt the learning well worth the wait.
The following equipment were used to evaluate the VTL 120/50: Audible Illusions Modulus 3 preamplifier, Pink Triangle Turntable with Sumiko MMT and Promethean Green cartridge, JVC XL-Z1050 compact disk player all connected through an Inouye power conditioner, Sound Dynamics 300Ti Speakers with Target stands, Kimber 8TC speaker cables and MIT interconnects.
In the tetrode mode
Listening in tetrode mode was a disappointment, especially after my ears had become accustomed to the Quicksilvers. The 120/50 provided extended and more detailed highs. Bass was delivered with a wallop, and one could appreciate the strong base lines.
The amp let the music flow with the dynamics approaching the Classe DR-9. But it lacked the midrange magic portrayed by the Quicksilvers. There seemed to be more emphasis on the highs and lows, and I believe this made the music sound both bland and tiresome.
The metamorphosis
Switching to triode made a dramatic difference. The highs became sweeter. The midrange blossomed. There was more vividness-one could see through the layers and place the source of the instruments more distinctly. The 120/50 metamorphosed into an artful and airy musical instrument.
From the start, it established its virtuosity. Otis Redding (Warner 9-27608) started rocking instead of simply rolling along. You could get into the rhythm of his songs. The amp also illuminated more of the details and nuances without calling attention to them. It let more music flow through than I have been accustomed to. I know because for the first time I started to really enjoy this CD.
J.S.Bach Cello Sonaten (DG 415 471-2) also became more involving. Maybe its because there was more body, dimensionality, if you will. Van Morrrison's Moondance CD (Warner 3103-3) recaptured a hint of the emotion portrayed in the LP version.
Weaknesses
While the 50 of the 120 deserves lavish praise, it also has a number of weaknesses. The amp should be partnered with fairly efficient speakers. Otherwise, it will run out of juice. Operated within its power rating, it is simply enchanting.
It falls short in dynamic contrast when compared to the Classe DR-9. It does not have the nonchalance and control portrayed by this wonderful transistor amp. It also lacks the heft and bass attack exhibited by its more powerful counterparts.
Conclusion
The VTL 120/50 in its triode mode deserves unequivocal recommendation. It is engineered for durability. It does not require frequent bias adjustment and tube replacement. The transformers run cool and parts are said to operate below their rating.
To an individual with a predilection to tube equipment to recognize the superiority of the 120/50 says it loud and clear that this amp is indeed something special. This amp deserves a rating of 4 (out of a maximum of 5) clefs.
These pieces are not often offered in the used market. I have seen a few advertised for around $1200. (There was a monoblock version and I have seen those selling for around $1900.) I'm so glad I have a 120/50--this makes looking for one unnecessary!
by Rome Castellanes
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