So, IMO, the most musical and human sound is from a single ended triode
amp or preamp (SET). Think the SET is the oldest still used audio amp
circuit. Used in the first Bell telephone systems (WE). Funny, SS wants
to sound more like tubes and multiple output tube amps want to sound
more like SETs... sort of.
SETs are known for the warmth they have; that is caused by a predominate
2nd harmonic distortion. The ear assigns tonality to all forms of
distortion; the 2nd is responsible for 'warmth', 'bloom' and the like.
The 3rd and 4th contribute to this as well. A good SS amp might sound very tube-like; as both tube and solid state become more neutral they will sound more and more alike. IMO/IME the issue that plagues SETs is that most people simply don't use them on speakers that are efficient enough. This is because the amp should *never* be driven past about 20% of full power, otherwise the higher ordered harmonics begin to appear. The ear uses these harmonics to sense sound pressure; since music has many transients this distortion initially appears on transients, causing the amp to sound very 'dynamic'. This is why many SETs get comments about how dynamic they are despite their low power. Its distortion masquerading as 'dynamics'. Whenever you see that its because the user was using a speaker of insufficient efficiency! |
I think most of this boils down to system synergy. I'd be careful about that- if you pair a bright preamp with a dull amp, the result will not be neutral. I recommend to all our customers that whatever they buy, each piece in the system should stand on its own merits rather than hopefully being corrected for its faults somewhere down stream; the latter is a recipe for flushing dollars down the loo. The one exception to this is that not all amplifiers drive all speakers. This is true regardless of the amplifier, although there are speakers that are driven equally well by many amps. for more on this: http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php |
Its a simple fact that if the front end of the system doesn't get it right, the best amps and speakers downstream won't win you any of the lost signal.
For this reason I do feel that a good tube preamp is paramount. But tubes bring something to the amplifier department as well. Tube amplifiers generally speaking tend to have greater soundstage width and depth than solid state, and tend to have more detail without brightness (this on account of how both technologies make distortion).
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I go to a hell of a lot of live shows. Most recently Dweezil Zappa
playing all of "Hot Rats". Modern guitar playing involves a lot of
intentional distortion. Every hot guitarist with chops relies on a ton
of effects pedals in addition to the intentional distortion produced by
the tubed stacks. That depends on whether the amp is clipped. Guitar players like tube amps because they have less odd ordered harmonics when they clip, making them easier to sculpt more pleasant tones. But some guitar players don't clip their amps; the guitar players in my band (Thunderbolt Pagoda) are an example; instead they rely on their pedal effects for the sound, but prefer tubes otherwise. One is using a Marshall Major, which is built along high fidelity lines and was often used for for bass or sound re-enforcement- both applications where distortion isn't helpful. Other amps built along high fidelity are the early Sunn amps (highly sought after and using the guts of the Dynaco MkIII) and Ampeg amps like the V4. Guitar players also like to have a good 'clean sound' and good fidelity in the amplifier is crucial for that. An amp with a good clean sound easily reveals differences in pickups, 1/4" connectors and guitar cables- not all that different from what audiophiles experience in that regard. |
How important is it for you to have a tube amp fixable locally rather than having to ship it back to the maker for fixes or upgrades? Repair-ability has always been high on my list. I would consider upgrades to be quite a bit different from repairs though! When I was putting myself through school I worked repairing consumer electronics. I ran into some stuff even way back in the early 1970s that clearly didn’t have service in mind when it was built! That sort of thing can be a nightmare if the equipment develops a fault; ease of servicing has always been high on my agenda- you sleep better at night :) |
Tubes can add some sweet sounding harmonics to recording that need
them. They can also add these harmonics to recordings that do not need
them. It used to be said that James Parker of Audio Research
specifically added 2nd order harmonics to sweeten his design. As a
scientist of sorts, I prefer to add harmonics on an as needed basis. This sort of blanket statement is problematic! The actual psychoacoustic situation is much more complex. Just as tubes 'add harmonics', so do transistors (although to a lesser extent). The problem is that with the vast majority of transistor amps (greater than 99%, due to insufficient gain bandwidth product, which is a discussion for another thread) the harmonics they add are higher orders which are interpreted by the ear as brightness and harshness. The ear has a masking principle, and in addition is relatively insensitive to the lower ordered harmonics (2nd-4th). If the lower orders are present in sufficient quantity, they can mask the presence of the higher orders. This is why tubes sound smoother than solid state despite having higher distortion. On the personal preference side, I enjoy the greater soundstage width and depth, instrument timbres and low level detail that IME that is commonly associated with tube circuits. |
@hilde45 with the Salk SS 6M you will only need about 1/4 the power to do what you were planning before. 30 to 60 watts should be very nice on this speaker provided you are not too far from them in your room.
That speaker seems to be quite tube friendly- a customer of ours has a set and loves them with our M-60 amplifiers. This speaker allows you a lot more options!
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and I was wondering if there are tube pre's that are more suited to SS
amp matching in terms of impedance matching. Do I just go by the 1/10
rule (output impedance for the pre)? Al's comment is correct- look at the 20Hz output impedance if you can find that spec. **That** impedance is the one that you want to be 1/10th that of the input impedance of the amp. In the case of our MP-1 and MP-3, the output impedance is the same as the frequency response curve (which is to say that their output impedance are the same at 20Hz as 1000Hz) but this is as Al pointed out, owing to a balanced direct coupled output (which to my knowledge is the only other way to support the balanced line standard outside of using a line transformer at the output of the preamp). |
@hilde45 The thing you have going for you with the Salk speakers is they have a moderate 8 ohm impedance with no nasty phase angles or dips. This makes the job of the amplifier easier. Jim is pretty conservative about his ratings- I suspect what passes for 83 dB or so for him is 86 or 87dB with some other brands- it depends where on the curve of the speaker you measure its sensitivity!
If I can make a suggestion: When working with **any** amplifier (tube, solid state, class D), its distortion will be lower if it is not asked to work hard! To this end, your amplifier investment dollar will be better served by a loudspeaker that is higher impedance (8 ohms as opposed to 4, and 16 as opposed to 8) because the amplifier will make less distortion. This is both easy to hear (as the distortion is higher ordered harmonics and addition IMD) and easy to see in the specs. When you can hear it and measure it, its real :) In the case of tube amplifiers with output transformers, the higher impedance will allow the output transformer to operate more efficiently. When the OPT (OutPut Transformer) heats up, its converting amplifier power into heat :( When driving lower impedances, not only does the OPT operate less efficiently, it can also lose bandwidth. On the bottom end this can be up to an octave of bandwidth loss between 4 ohms and 8!
On top of this loudspeaker efficiency is also important, particularly in the case of tubes, as tube amplifier power is more expensive (the industry went solid state not due to performance but cost reasons decades ago). This also helps the amp to make less distortion since it doesn't have to make as much power. A 3dB change in efficiency doesn't sound like much to the ear, but that is a difference of twice the power in the amp! So when you go from 83dB to 89dB, to make the same sound pressure the amp need only be 1/4 the power. The $$$$ implications should be obvious.
The less distortion, the more the presentation will sound like real music.
One other thing: lower efficiency loudspeakers are inherently less dynamic. This is due to heating of the voice coil- which in turn reduces its sensitivity. The more power you give it, the worse this becomes. There tends to be less thermal compression in higher efficiency loudspeakers.
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but I'm completely in the dark about what your stuff costs. We make a 6SN7-based preamp that as a line stage is $1900.00. @hilde45 The line stage of my prior comment above is the UV-1. Were you planning to run a balanced preamp or single-ended (the UV-1 is single-ended). |
One parameter is budget. Is this Atma or Ear in the neighborhood of $3k? @hilde45 We make a 6SN7-based preamp that as a line stage is $1900.00. It is single-ended. We also make balanced preamps (and were the first to do so) but they retail for more than you budget. But we've been making them a long time so you might be able to find one used within your budget. We can refurbish and re-warrant any of our older products. |
^^ Similar preamps are handmade using 6SN7s here in the US for similar or less money (shipping is cheaper).
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