Maybe you mean the best high frequencies? My nomination is the Futterman H3aa mono OTL tube amps. So rare that most have never owned or heard them! I have a pair - actually my second pair - after stupidly selling the first pair back in 1992. Used with the Quad 57's.
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Smoothest most detailed amp into a pair of Quad 57’s with Kelly Decca Ribbons tweeters from 12khz up, for me would have been a Nelson Pass Pure Class-A 20w project amp I made called the A20, back in the 80’s https://www.firstwatt.com/pdf/art_classa_20.pdf This amp led me later to make a self contained recirculating water cooled monster, which was >100w of the same thing, and a two man lift. Cheers George |
many tube amps are closed in on top, not airy. so they may be butter smooth, but it’s a circuit artifact overlayed over all the music, and not ’the’ music. what you want is transparent, grain-less and continuous, but still lively and with great textures, timbres and tonal richness. i’d choose darTZeel; both the dart 108 stereo Mk1 and Mk2, and the dart mono blocks. zero global feedback, minimal parts count in the signal path. purity and transparent. no sense of any artifact overlay.....just music. super smooth and amazingly grain-less and extended, airy top end. darTZeel does not sound like tubes, or solid state.....it sounds like music. |
many tube amps are closed in on top, not airy. so they may be butter smooth, but it’s a circuit artifact overlayed over all the music, and not ’the’ music.@mikelavigne The quality of smoothness is a lack of higher ordered harmonics; also a lack of IMD. 'Airy'-ness is arguably a different quality which probably needs more clarity to make sure we're talking about the same thing. In my book, 'airy' has to do with the speed of the amp; many tube amps are not all that fast (15Volts/usec is common). The other thing that this might refer to is phase shift. If there is a roll off in the amp that isn't all that far from the audio band, for example 50KHz, this will introduce phase shift down to 1/10th the cutoff frequency. The ear interprets this sort of thing as a coloration (since it covers a spectrum rather than a single frequency); if the phase shift is due to roll off, it will interpret is as 'dark' or 'slow'. Not all tube amps behave as you describe of course (hence your use of the word 'many' rather than all). If the amp has bandwidth to 100KHz then its going to have minimal phase shift and won't sound dark. How it generates the higher ordered harmonics is a different matter, but there are tube amps that are both smooth (lacking audible higher ordered harmonics) and 'airy' at the same time. |
@atmasphere Ralph, i’m not a spec guy, and have not doubt about what you are saying. for sure i’ve heard tube amps with noticeably open extended top ends; three come to mind and they are all OTL’s; any Atmasphere i’ve heard :-), my Tenor 75 watt OTL’s back in 2001-2003, and the Berning 211/845 during my in-room demo a few years back. a friend has some Found Music ’Blade’ tube amps that are very open on top, not sure the topography. these are the tube amps i’ve heard enough to comment on. i had the Lamm ML3’s and big VAC’s in my room for 3 months back a couple of years. i’d say each are ’better than average’ as far as tube amps top end extension but not in darTZeel territory, or OTL territory either. |
50kHz and 100kHz along with a SuperTweeter to reproduce ultra sonic frequencies is certainly worth considering. Exactly how or why they would introduce phase shift down to 1/10th the cutoff frequency isn't revealed or explained. In any case, why just those frequencies? What about 20kHz cutoff frequency causing a 2kHz phase shift? |
Exactly how or why they would introduce phase shift down to 1/10th the cutoff frequency isn't revealed or explained.A 20Hz cutoff will induce phase shift to 200Hz, robbing the amp of impact (since that is how the ear perceives phase shift in the bass). Its filter theory. When the amp rolls off, it does so on a 6dB/octave slope. A 6dB slope causes phase shift to 10x or 1/10th the cutoff frequency (-3dB point) depending on if the cutoff is the low frequency point or the high frequency point, respectively. So you need 2Hz bandwidth to properly reproduce 20Hz and 100KHz bandwidth to do 10KHz. There is a way around this, by introducing so much feedback that the amp is able to correct phase shift. That amount needs to be at least 35dB, but the caveat is that the 35dB value has to be the same at all frequencies from 20Hz to 20KHz. Most amplifiers made in the last 70 years are not capable of this feat since it requires a lot of gain bandwidth product. |
a tie between a class-A tube amp whose name escapes me [this was back in 2000], and a rega brio 3 which was the most mellow-sounding transistor amp i've ever heard. if i had a big enough space, i'd enjoy listening to music with that amp and a pair of Vandy 1Ci speakers, as i heard in the showroom a few years back. |
When I hear the term smooth I want to scream! I don't understand what smooth even means? Maybe because I'm a winemaker and "smooth" in the wine world is a term used when not being able to evaluate complexity. Like wine when listening it can also be a complex experience. Smooth can be construed as a number of sonic observations. Its non specific. The term Smooth sounds boring. I'm using a Gryphon Mephisto, "smooth" doesn't come to mind. Many other attributes do. |
@jakesnak I'm with you. I also understand your example of wine as analogous. I don't get what the term "smooth" means when applied to an amplifier. My expectation / goal is for the recording to be expressed as 'intact' / as 'intended' as is possible. Anathema comes to mind. Both English definitions are apropos. In Spanish, even more so. : ) 1. something or someone that one vehemently dislikes. As in: I would dislike an amp that smoothes what isn't smooth and I would reject an amp that does so. Perhaps others who have posted above can help me with my (lack of) understanding? |
I comprehend the sentence and premise. Its a very good technical explanation. However, the point I was attempting to make was, from a sonic perspective "smooth" doesn't present itself as something I am attempting to ascertain, or looking for in a amp? I have listened to many amps, I never recall saying "that amp is so smooth". I'm not trying to sound disrespectful. I think its a useless adjective when evaluating sonics of a component. Do you think a sound engineer says "we have to do it again, not smooth enough" IMO, Its a pointless term. |
A very nice amp and definitely the smoothest amp I have ever owned was the Luxman M800A. I've owned 36 amps since 2006 (which does not make me any kind of expert, but it does make me psycho!). Certainly the Pass amps I have owned were very smooth as well. And then I've had some some fingernails on chalkboard amps as well. eewww |
The best high frequencies I have ever had I have now with my Linear Tube Audio Z40. It is a David Berning ZOTL design with 6Hz-60kHz (+0 -0.5dB) and no traditional output transformers. So the roll-off (if there is some) entirely depends on what tubes you are using. It is one of the least ’tubey’ sounding valve amps I have ever heard, yet you can instantly tell it must be tubes )). ZOTL doesn’t sound exactly like OTL amps, but matches them in resolution and speed. The perceived "airyness" is a double-edged sword: often it is just lack of weight in high freq. which is a trademark of so many SS amps, even good ones. Also, if you go for a "smooth", high-resolution, detailed, "realistic" high freq. you would need to start with your mains supply and vibration control, otherwise you will never get there. Smoothness is often associated with a liquid, free-flowing midrange/presence region devoid of any edginess. When you start looking for it, you will inevitably end up with tubes. Sone NOS Mullards probably )) |
from a sonic perspective "smooth" doesn't present itself as something I am attempting to ascertain, or looking for in a amp? I have listened to many amps, I never recall saying "that amp is so smooth". I'm not trying to sound disrespectful. I think its a useless adjective when evaluating sonics of a component. Do you think a sound engineer says "we have to do it again, not smooth enough" IMO, Its a pointless term.@jakesnak Its not. In fact, if the amp isn't sounding nice and smooth, to me its an indication of higher ordered harmonics and I will be looking for a reason to work on the circuit 'till I have it right. It sounds to me like you've not experienced an amp that is actually smooth. My recommendation is to listen to the difference between a solid state amp and a tube amp (one in good condition of good design; not something hauled from a 1960s console...). If you've only heard solid state, you might have heard hundreds of them and not heard anything to justify the term. There are smooth sounding solid state amps but they IMO/IME are quite rare. One qualifier: When/if you are interested enough to do this as an audition, make sure both amps are happy with the loudspeaker used. If that is the case, you won't have any problem hearing this difference- its literally why tube amps are still around after tubes were declared 'obsolete' back in the 1960s. Normally when the prior art is succeeded, it goes away. But tubes are still in production; they have been 'obsolete' now for longer than they were the only game in town! That's happening for a reason and that reason is literally 'smoothness'. |
The Luxman m900u SS amp is very smooth as posted above. I never owned it but I thought it was the smoothest SS I have ever heard. I own an very smooth amp myself in the KRELL K-300i. Most comments I have read on old KRELL do not use smooth as a descriptor. However, this new KRELL with the XD feature on the amps are buttery smooth. A very enjoyable listen. I use them on some bright headphones than are uber revealing, a great match. The Luxman is warmer than the KRELL. |
At prices I consider reasonable (something not costing tens of thousands of $$$) there always seems to be a trade off of dull and muddy to get smooth, or harsh and edgy to achieve detail and punch. In the 80s I had a little 80/155 W. PSE Studio II power amp paired with a Audible Illusions pre. that, to me, was a beautiful combination of smooth, yet unveiled and detailed and dynamic without being harsh and edgy. At only about $500.00 it put to shame amps costing much more. A couple that I can think of (somewhat reasonable in the used market) that fit the bill of smooth, yet dynamic, clear and detailed and with enough grunt to drive a larger set of Maggies - an Ayre V-5xe or a Bryston 4Bsst2 or cubed......Jim |
