And yes, Tom, David Manley had a legacy of having really good output transformers. The original VTL ratio for where to set their ultralinear point on the output transformer was different than the ration specified by Hafler I do believe. David Manley was also a big believer in having beefy power supplies with SS rectifiers so that he could extract the best bass quality he could from his amp designs. As for my monoblocks, are you referring the Dynaco MKIII amps that are laying in a zillion pieces right now?
I used to own some VTL trioded amps. Did a little experiment. I also had a Spectral DMA50. I loaded the VTL with a power resistor, and tapped the output with some divider resistors so the whole thing was exactly unity gain. Fed that into the Spectral. Feeding Quad ESL-63's.
My purpose was to figure out how much was lost in the VTL, which I considered the better amp. It had more space, 3d effects, smoother, more dynamic, more nuanced, more musical. The Spectral was a good sounding SS amp, but not equal to the VTL. The Spectral was subjectively about 2/3 as good as the VTL. I wondered if the VTL let 99% of the music through or 50%. So I thought taking it in and out of circuit I could get a handle on how much better things could get. Or if the VTL left little on the table.
I did not expect to fire that series arrangement up and hear the Spectral sound exactly like the VTL. Which is what happened. The spacious dynamic musical 3D sound issued forth from the Spectral amp. I later reversed position of the amps, and you could put the Spectral in or out and hear no difference. The wonderful sound of the VTL was a euphonic coloration. The Spectral could exactingly reproduce those effects if fed the right signal.
I switched a few times, listened over days. In time I did find the sound with the VTL feeding the Spectral balanced a little different than just the VTL. Bass was a bit less, and treble a touch less. I knew from measurements the output impedance of the tube amp interacted with the Quad's to raise the lower couple octaves a bit, and a resonance in the output transformer at 26 khz raised the top octave some too. Over time those were audible, but not obvious. Otherwise the Spectral could fully mimic the wonderful coloration of the VTL triode amp. So much for tube amp superiority.
esldude-Which VTL triode amp did you have? Hard to believe that an amp that you thought was clearly better than the Spectral ("more space, 3d effects, smoother, more dynamic, more nuanced, more musical") was suddenly regulated to the scrapheap of euphonic colorations due to your bypass test. So how was it that you were fooled and believed in the superiority of the VTL over the Spectral amp?
Sigh... So here is my view of this matter (and do remember - I have an MS in science and worked for 27 years as an engineer and then TAUGHT engineering for 10 years at SMU and UTD). For the record - I have had several different tube amplifiers starting with some Dyna ST-70 amps - which I completely rebuilt and mildly modified - rather successfully (mono-block arrangement). Later I had Quicksilver mono-blocs - but I am hear to tell you - I much prefer the sound of a well built solid state amplifier (Class A or A-B) - no contest to these ears. For I hear a well designed solid state amp as much truer to the recording - while I feel that a tube amp is hardly short of a distortion factory. NO class D is allowed on the premises (another story).
No - I think any reasonable person will agree that tube amplifiers do NOT sound like transistor amplifiers. This is more or less a given.
From the standpoint of our own Roger Sanders (a reasonable and experienced person) the difference between the two approaches is attributable solely to the way the two different amplifiers "clip" (see the whitepaper on same at his "Sanders sound" website). The tube has a "cloud" of electrons around its plate and thus, even when overdriven can respond more gracefully than the transistor approach which, in most cases, effectively "crowbars" and shuts down when overdriven (even if only for micro-seconds).
I do NOT agree with Roger in this matter.
What I believe the clear sound difference can be attributed to is based on the following;
1) A "hollow state" device can switch high voltages 'faster' than a tube can switch high currents. I know this was true in the '90s as I worked on a missile that had a transmitter (active homing) and we originally had a solid state radar frequency amplifier - this tech did not work and we went with tubes. Yes. This missile is called an AMRAAM. Go look it up. Apparently transistors (of some stripe I am not sure if bipolar of FET) have been sufficiently advanced that modern radars use transistors exclusively - but then again most modern military radars are phase-arrays so the power requirements for each transmission element is rather low - or at least much lower than in single aperture radars.
So the increased switching speed available with a tube device may be a contributor to the different sound. Quick - not unlike live music. All that current sloshing around within a bipolar transistor tends to make the device slow (which maybe why our genius solid state guys - like Nelson Pass - do NOT use bipolar silicon but instead work with FETs (much higher voltage across the device).
2) The biggest difference is that huge chunk of iron sitting on the output of your tube amplifier - that transformer which translates those high voltages into high currents for use by the speaker motors. Transformers, like it or not, ring like a bell. That is to say when a transformer is hit with a change in applied voltage it actually works to induce a voltage of the opposite polarity - di/dt - fact of life folks. Transformers resist, in a very active and known sense AC changes.
Not only does the transformer create a very non-linear response to changing voltages a transformer is NOT linear in its time response to a changing voltage. To tune a transformer "up" (increase voltage) proceeds much more quickly than to tune a transformer "down" (lower the voltage). I would estimate by a factor of 3 dB (double the time).
This non-linear response of a transformer, coupled with the massive EMF "kickback" associated with large speaker motor means that most tube amps produce a very pleasant distortion that closely resembles the sound of "slap echo" that is heard in any large concert hall (particularly in my local concert hall - the Meyerson in Dallas - very pronounced slap echo, i.e. you can hear the echo from the walls of the hall - slight, and very close in time to the incident signal but nevertheless very real as it is outside the Haas effect window). The EMF kickback - as it crosses the coils of the transformer AND the non-linear response of the output transformer to a changing voltage means that the sound tends to be more than a bit "ringy" - which is EXACTLY the sound of a real un-amplified instrument played in a real concert size hall.
Hence the "tube heads" think they are getting "better" sound - but what they are actually getting is a "ring" that is nothing more than a distortion. Is this ringy sound pleasant? Of course, especially if you are playing symphonic music through some high quality speakers. More so if your speakers are somewhat "lean and thin" sounding - particularly like a Martin-Logan electrostat (or ANY electrostat save a big SoundLab). The tubes "put some flesh" on the sound - but what those precious tubes are doing is ringing like a church bell at a drunken wedding.
So we are back at the fact that the attraction of a tube amplifier is about its woeful non-linearity and the complete inability of a coupling transformer to respond in a linear matter to changing AC voltages.
Sorry guys - if you like tubes, their heat, their lack of power, their utter lack of reliability - then I say knock yourself out. But don't come around here and try to tell me that "tubes" are better.
If you want a pleasant distortion - go get one of those QoL thingies.
Proceed to nuke me.
And how do you then explain OTLs have the same tube characteristics? And even the best SS amps today, retrieve spatial information like tubes. So is that a distortion? It's there on the master tapes and hard discs, be they analog or digital.
Reliability. You simply don't know what you're talking about. Maybe tubes 20 years ago, but not modern gear. For the record, I've used cj tube amps since the mid-80s and had one problem - a resistor blowing- in a 7 yo MV-75A1. Even 7yo Krells developed issues (and solid-state - contrary to your assertations - is far from problem free.)So no, your sweeping generalization is dead wrong. It's not the genre, it's the execution.
Last edited by MylesBAstor; 02-02-2014 at 04:29 PM.
I have read the Vacuum Tube Logic book in the early 90's and after some one borrowed it from me and forgot to return it, I got the second edition. I still read it occasionally in my free time when I am not reading the the famous Toole book ...
It happens that your starting post is severely distorting the points expressed by David Manley in his book, mainly by omission, but unfortunately to a point they can become impossible to support in a debate. The key formula for this explanation is energy of a power supply (E=CxVxV/2) in Joules and its voltage regulation versus frequency. Unfortunately I do not have the time to summarize it, and as the book is copyright of VTL, we can not post a scan of it - this subject starts at page 51 of the second edition.
The thread should be read remembering that VTL tube amplifiers use very high voltage in their power amplifiers - around 600V and purpose built capacitors. And yes, off the record, my old VTL MB750 sounded great and powerful.
You may be right Micro. It has been quite some time since I have read David's book. I remember the talk about joules, but I thought that was to show how much energy his power supplies were storing and why VTL amps had very good bass in their day. I will have to look up the comment he made about tube watts to see how far off the mark I am. He may have been referring to his amps and not tube amps in general. It doesn't change the fact that tube watts are high voltage/low current watts until after the output transformer.
Given that I've hear both tubes and solid state sound both harsh and smooth, flat and spacious, sloppy and controlled, I'm inclined to believe that it is the combination of these two things:
1. design and execution
2. how a particular amplifier will perform matched with any specific speaker
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