A year or two into my audio journey, I was in college when an friend replaced his heavily modified McIntosh 240 amplifier with a set of VTL Compact 100 Monoblocks. Our little audio community were a little disappointed since this change also meant the removal of his Quad ESL-63s. These electrostatics were replaced by a big ol' pair of UREI 813 dynamic speakers, using the Alnico version of the Altec 604. But, to be fair, the Quads - without a subwoofer, weren't the best for rocking out. Understandable to us 20-somethings.
Along with the amplifiers came the VTL book, something that he loaned to me. At the time I didn't know too much about circuits so I read David Manley's words with much interest. I was a poor college student at the time and was firmly stuck in the (then) more affordable world of vintage gear. Dynaco was more my speed with the PAS-3X and the Mark IVs being in my system at the time. Owning new tube gear was just out of my means.
I'll hit the fast forward button on my life. So many years later my interest in modifying or building my own tube or solid-state gear has declined. Some of it is cost, why make a tube amp when there are so many reasonably priced units out there? And a lot of it is patience and my close up vision isn't what it used to be. The idea of staring at a circuit board or a snake pit of wires hour after hour no longer holds the same interest. It is so much easier to buy something, and at such a reasonable price, this used VTL Stereo Deluxe 90/90 power amplifier was a must buy when I saw it on Audiogon,
Okay, what is the VTL 90/90? It is a 90WPC - their claim, not mine - tube amplifier using a pair of 6550s (or KT88s or KT90s) and a pair of 12AT7s per channel. No tube rectification, no B+ regulation, and no power supply choke. Instead they use a large amount of capacitance to get the B+ ripple down. The output tubes are also connected in Ultralinear, which means the screen grids of the output tubes are connected to taps on the output transformer primary. Bias is relatively low, only 35mA per tube, meaning heavy class B operation. The output iron is of note - being made by Mercury Magnetics - which are known for high quality.
This is not really the way I would build an amplifier. I prefer, at least philosophically, pentode output stage and some type of regulation for the screens and the input stage.
Physically speaking the VTL is not as imposing as my Sonic Frontiers SFS-50. The SFS just looks better built with the meter, larger chassis, and bigger output transformers. It also has a trick cascoded differential 6922 input stage, and well, lots of regulation going on. The VTL, on the other hand, has a Mullard 5-20 type circuit with a parallel 12AT7 input tube and a long-tail phase splitter (with no current sink) afterwards.
So, you are already asking after that long introduction, how does the VTL sound? I'll try to keep this short. I will be comparing directly against the Sonic Frontiers SFS-50.
A quick note on tubes: I used vintage three-hole Tung Sol 6550s and GE labeled (made by Lansdale) 12AT7s for the VTL. Not the pictured tubes which came with the amplifier. The SFS-50 amplifier used the same output tubes and Tungsram ECC88s.
The VTL has a big bold and dynamic sound. This is a fun amp to listen to! Bass, something the company was known for, has a deftness that a lot of solid-state amplifiers could only dream about. How is this possible? I don't know given the lower output impedance of silicon based amplification. The Sonic Frontiers, however, seems to best the VTL in the very lowest bass notes. I suppose that makes sense with the bigger output iron and all that regulation.
What surprised me the most about the VTL 90/90 is how natural it sounds. The character of the amplifier is the same from top-to-bottom. It's just an easy amplifier to listen to. The SFS-50, on the other hand, is more neutral. When it comes to detail the Sonic Frontiers is the clear winner, but that, as I will mention later, this comes at a cost.
Soundstaging? The VTL is w-i-d-e and deep. Vocals, like in The Ubiquitous Mr. Lovegrove by The Dead Can Dance has real presence and body. This is a real treat, as was my American copy of Pink Floyd's Dark Side of the Moon.
So where does this amplifier fail? This is a thorny question and one that drives into the pros and cons of this hobby.. It is a matter of detail. I love detail but I can also be actively annoyed by excessive amounts of it because lesser recordings sound, well, bad.
The Sonic Frontiers, with its 6922 front end, has so more detail. Like the sound of the hands striking the aforementioned Dead Can Dance song. It really breaks down the recording into more component parts that the VTL amplifier. The VTL blurs this detail - only by a bit - but is also a touch more engaging.
What amplifier do I prefer? It's a matter of taste. The VTL is just enjoyable, sounding more like a powerful Dynaco amplifier. The Sonic Frontiers is better for those days I want to eek out more detail and hear the best that my system can do in a purely audio geek sense.
System:
Rega P8 turntable with Rega Ania Pro MC cartridge
to a Denon AU-S1 step-up transformer
to Cardas Neutral Reference interconnects
to an Audio Research SP-8 (with a mix of vintage Mullurd and Amperex tubes)
to Cardas Iridium interconnects
to the amplifier(s) being tested here
to Cardas Iridium speaker cables
to KEF R500 loudspeakers
