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Old 11th February 2011, 04:57 AM   #1
931410 is offline 931410  United States
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Default Tubes are beautifully colored....right?

Okay, soliciting opinions.

A few years back, I had Quad ESL-63 speakers, driven by VTL 75/75 amps. I had converted the amps to triode, upgraded coupling caps to some exotic brands, put all Vishay resistors in the circuit. Bypassed the power supply caps with some exotics. Used very expensive tubes in the KT-88 configuration. I thought it the most musical amp ever, and several experienced audiophiles concurred.

Best SS amps I had ever had were Spectrals. Had a DMA-50 on hand. Not the equal of the VTL, but quite nice, enjoyable SS amp.

I began wondering what more could be done to improve things. All options left were complex and expensive. I wondered.....am I close to perfection or far away. Is the VTL with mods etc. 95% of possible or only something like 50%? I considered the Spectral to be subjectively about two thirds as good as the VTL.

Decided I could figure it out with inserting a device in series and seeing how much degradation occurred. The VTL was much more musical, natural, spacious, 3D, more resolving etc. etc. So would it be close to perfection (straight wire with gain vs. the source) or far from it. Decided I would series devices to find out.

Loaded the VTL down with power resistors and then tapped the result with a voltage divider network so the overall result was unity gain (or as close as possible with the Fluke multimeter to 3 decimal places). Had this unity gain VTL feed the Spectral DMA-50 input driving ESL-63's. I expected to find out how much the VTL colored the signal vs. a direct connection to the Spectral. My expectation was the VTL was doing little wrong as it was so spacious, detailed, and enveloping when driving the speakers directly.

So imagine my surprise when feeding a CD out to the VTL, and then to Spectral amps that I heard the VTL sound or at least 99% of it. Spacious, detailed, musical, enjoyable, and dynamic. What was going on here? How could the musically inferior, lower rez Spectral manage this? Well reversing the amps, having the Spectral loaded with power resistors, then feeding the VTL at unity gain, I heard no difference. I mean, Spectral in vs Spectral out, I simply could hear nothing. The Spectral should have been true to source. It had exemplary signal to noise, more than 1 megahertz bandwidth, high slew rate, low distortion etc. I simply couldn't hear it in or out of circuit.

Left me with one conclusion: Yes, tubes were subjectively much more enjoyable, more resolving, more musical.....and it was all due to a coloration. Delicious, seductive, but not at all transparent. The Spectral was very transparent. Tubes were a delicious coloration.

I tried the same experiment with a few other SS amps. Not many could equal the Spectral. Some large Muse amps, sounded 85% like the VTL, but overlaid it with a bit of MOSFET mist, and noise. A Electron Kinetics overlaid it with a bit of edgy quality, though only in the treble and most sounded 75% subjectively like the VTL's.

So what other conclusion could one make other than tubes were a coloration, delightful and nice, but a coloration all the same. I think the belief that tubes are truer to source have mislead much of the audio world. I don't have a problem with those who say if it sounds better it is, but do realize it is a coloration, and not true to source. Don't then base your design theories on a mistaken notion.

Oh well, just wondering what comments folks would have on this.

FYI, I currently use a digital amp, which seems even more true to source, and fully transparent than the Spectral of yore. I think we have an unacknowledged golden age of audio now. But people are pursuing an illusion instead.
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Old 11th February 2011, 08:12 AM   #2
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Quote:
I began wondering what more could be done to improve things. All options left were complex and expensive. I wondered.....am I close to perfection or far away. Is the VTL with mods etc. 95% of possible or only something like 50%? I considered the Spectral to be subjectively about two thirds as good as the VTL.
I'd say your setup is about 99.5%, but some folks will argue that the 0-99% range is either void or irrelevant and therefore your current setup is only 50%.

There's two three things to keep in mind in (DIY) audio:
1. Performance is subjective.
2. The law of diminishing returns applies here like in no other field.
3. As a synthesis of 2 & 3: the larger the investment in time & money you make in achieving a marginal improvement, the larger your own, subjective gain in quality is likely to be.

From the above follows a simple rule I live by as a DIY-er: "tinker, and be happy".
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Old 11th February 2011, 10:56 AM   #3
DF96 is offline DF96  England
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So what other conclusion could one make other than tubes were a coloration, delightful and nice, but a coloration all the same. I think the belief that tubes are truer to source have mislead much of the audio world.
Valve amps don't have to colour the sound. It just happens to be the case that people who prefer coloured sound also prefer valve amps. This is probably because for a given level of electronic expertise it is easier to build a reasonably good valve amp than a reasonably good solid-state amp. Both will be coloured, but the valve colour will be more pleasant to listen to than the SS colour. Most valve lovers deny this vehemently. I don't.

Having built their reasonably good valve amp, which sounds better than a reasonably good SS amp, they then believe that the colour (whose presence they usually deny) is 'better' than accuracy. They get used to this coloured sound, so when they hear uncoloured sound (perhaps from a much better SS amp) they don't like it. This has been known for decades, yet is still routinely denied. You can build a valve amp which does not noticeably colour the sound, but they would reject this as sounding too 'solid-state' or 'clinical'.

The solution is simple. People should say "I prefer the sound of X amp", rather than "X amp is better".
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Old 11th February 2011, 12:39 PM   #4
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most of my tube-o-holic friends like a certain amount of coloration in the sound. Not "Dynaco PAS" levels, but a touch of "bloom and life" as they call it. I'm more in the transparent/detailed camp which leads to never-ending arguments of what is more 'realistic'.

I've heard some extremely colored systems - like a pair of 300B PP amps running Altec VOTTs - and there was this big golden hue to everything we played, no matter what the recording quality was like. To me that is coloration. To my friend, it was pure heaven. He enjoyed it and more power to him.
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Old 11th February 2011, 01:09 PM   #5
Alkis is offline Alkis  Greece
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Quote:
Originally Posted by DF96 View Post
Valve amps don't have to colour the sound.
I have to agree with this statement. Although valves-mainly triodes, produce 2nd harmonic,semiconductors produce 3nd and this could be a fundamental diference. But again a triode could be far more linear than a pentode and someone doesn't have to use FB at all.This perhaps gives a more naturall sound.
It's been very surprising to hear to my 845 amplifiers and find to be neutral,except a more liquid,tube-like bass,which is very pleasant.
The same occurs with the amplifiers of a friend of mine,using 845s too.
In generall, I believe that this matter has to do a lot with the approach of the designers and someone could be lead to different results in any case.
And of course,tubes have become a fashion in today's market,so many companies are into that, producing devices with profit in mind.
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Old 11th February 2011, 01:27 PM   #6
DF96 is offline DF96  England
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Triodes roughly follow a 3/2 power law. This contains all harmonics, although the 2nd dominates. With a sufficiently high anode load, local feedback (also 3/2 power) cancels the grid distortion so you get reasonable linearity. Most circuits do not have a sufficiently high anode load. Pentodes also have a 3/2 law, but no anode feedback to correct it. (Adding external feedback using resistors does not solve this problem - you can't turn a pentode into a triode that way).

BJT follow an exponential law quite closely. This contains all harmonics, although the 2nd dominates. Alternatively, if used as current amplifiers they can be reasonably linear over a limited range but beta is so poorly controlled that you can't easily design this way.

FET are roughly square-law, so mainly 2nd.

The net result is that if you want to build an amp without feedback then you are more or less forced to use triodes, rely on their internal feedback, and get used to hearing colouration. Any other technology requires the careful application of the right amount of feedback. Using the wrong amount of feedback, or applying it badly, creates problems. Getting it wrong is surprisingly common!
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Old 11th February 2011, 01:46 PM   #7
Alkis is offline Alkis  Greece
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Maybe this is the case of overloading.

Why Tube Amplifiers : Ayon Audio

Regarding the FETs, I agree since they are voltage controlled just like the tubes.
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Old 11th February 2011, 02:09 PM   #8
DF96 is offline DF96  England
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That Ayon Audio page contains a lot of misleading woffle. It is stuff like that which gets valves a bad name among real engineers. They assume we are all that ignorant.

For example:

Quote:
When transistors overload (in a discrete circuit or in an OP amp), the dominant distortion product is the third harmonic.
When anything does symmetric clipping, the dominate distortion product is the third. That is a matter of mathematics, not technology. It includes valves.

Quote:
Tubes are voltage amplifiers as opposed to transistors which are current amplification devices.
Not true. Both can be characterised as either - Norton and Thevenin say so. Almost all precision use of transistors (including the input LTP in a SS amp) relies on their transconductance characteristics, not current amplification.
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Old 11th February 2011, 02:12 PM   #9
Loren42 is offline Loren42  United States
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Quote:
Originally Posted by DF96 View Post
Valve amps don't have to colour the sound. It just happens to be the case that people who prefer coloured sound also prefer valve amps. This is probably because for a given level of electronic expertise it is easier to build a reasonably good valve amp than a reasonably good solid-state amp. Both will be coloured, but the valve colour will be more pleasant to listen to than the SS colour. Most valve lovers deny this vehemently. I don't.

Having built their reasonably good valve amp, which sounds better than a reasonably good SS amp, they then believe that the colour (whose presence they usually deny) is 'better' than accuracy. They get used to this coloured sound, so when they hear uncoloured sound (perhaps from a much better SS amp) they don't like it. This has been known for decades, yet is still routinely denied. You can build a valve amp which does not noticeably colour the sound, but they would reject this as sounding too 'solid-state' or 'clinical'.

The solution is simple. People should say "I prefer the sound of X amp", rather than "X amp is better".
I agree. The theoretical ideal amp is a straight wire with gain. Everything else just has some degree of distortion.

So, it boils down to what type of distortion you prefer or if you prefer no distortion.

However, those that enjoy distortion in their amps rather call it colorization or musical or some other subjective unmeasurable term.

In the end, build/buy what you like and enjoy it .
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Old 11th February 2011, 02:38 PM   #10
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Convert it to triode, throw in a bunch of "exotic" caps ... I wonder how far you diverged from Mr. Manley's design goals.
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