No budget was mentioned. As one data point, I have heard the LS50 paired with Prima Luna Premium HP amplifier (the 70wpc model) extensively and I thought the sound was excellent albeit a bit bass shy.
SET v. Pushpull
I did a search and didn't find any threads on this topic. I am a newbie to tubes - I have a Tavish Adagio phono stage, and I am looking to add an integrated tube amp into the analog chain in my system - I have never owned one, so my knowledge level is low. Right now I am running KEF LS50 speakers, but they are a little small for my listening area so possibly looking at larger speakers - I was very impressed by the Joseph Audio Pulsars I recently heard, as one example.
Anyway, most of the integrated tube amps in my price range are seem to be push pull, although the Line Magnetic is SET. At a high level, I understand the push pull design gives higher output power than SET, but also higher potential for distortion.
Any practical experience with the pros and cons of each? And how important is this in the overall scheme, in real world applications? Say, compared to the choice of output tube?
Thanks,
Tom
Anyway, most of the integrated tube amps in my price range are seem to be push pull, although the Line Magnetic is SET. At a high level, I understand the push pull design gives higher output power than SET, but also higher potential for distortion.
Any practical experience with the pros and cons of each? And how important is this in the overall scheme, in real world applications? Say, compared to the choice of output tube?
Thanks,
Tom
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- 21 posts total
Guys, thanks for these responses - to add: My budget is going to be $5K or less, and because of real estate issues I don't have room for tube separates, or monoblocks, - need to go with an integrated. Herb Reichert at Stereophile has paired a SET design, the Line Magnetic 518ia with the KEFs, with good results. 22 Watts, supposedly. |
A number of good points have been made above. An important one that Geek101 mentioned that warrants additional emphasis, IMO, concerns impedance swings. An impedance curve for the LS50 can be seen in Figure 1 of Stereophile’s measurements. It can be seen that the impedance varies from a low of about 4 ohms at 200 Hz to about 13 ohms at about 1.5 kHz, before descending to around 6 ohms in much of the treble region. That impedance characteristic coupled with the small size of the speaker and its woofer (see the next paragraph for the relevance of that), as well as its low sensitivity (84.5 db at 1 meter for an input of 2.83 volts), makes it clear that the speaker was designed with the expectation that it would usually be used with solid state amplification. With a few exceptions, nearly all solid state amplifiers have an output impedance of a tiny fraction of an ohm. The interaction of that very low output impedance with the LS50’s impedance variations over the frequency range will work in the direction of augmenting the mid-bass response, relative to the response at higher frequencies. In contrast, tube amp output impedances differ widely among different amps. Some have low output impedances, in the area of 1 ohm or even less, while some have output impedances of several ohms or even more. And if the LS50 is driven from a high output impedance the interaction of that output impedance with the speaker’s impedance swings will result in a tonal balance that is not what the designer intended, and in particular is likely to be weak in the mid-bass. You indicated that Reichert obtained good results pairing the LS50 with an LM518ia. Undoubtedly a major reason for that was that the LM518ia has a considerably lower output impedance than most SET amps, especially from its 4 ohm tap. Per Stereophile’s measurements of that amp: So I would definitely not extrapolate Reichert’s finding to other SET amps, or for that matter to many push-pull tube amps. Also, regarding power capability, keep in mind that what will **dramatically** affect how much power is required is the dynamic range of the music that is listened to (i.e., the **difference** in volume between the loudest notes and the softest notes). Many and perhaps most pop and rock recordings are dynamically compressed to a dynamic range of less than 10 db, meaning that less than 10 times as much power is required to reproduce the loudest notes as to reproduce the softest notes. While classical symphonic recordings may have dynamic ranges of 30, 40, or (in a few cases I have measured) as much as about 55 db. Those correspond, respectively, to 1000 times, 10000 times, and about 300000 times as much power being required to reproduce the loudest notes as to reproduce the softest notes (and those are not typos). So in those cases if the volume control is turned up high enough to hear the soft notes at reasonable levels vastly more power will be required than would be necessary for recordings having minimal dynamic range, such as most pop and rock recordings. Finally, regarding the Joseph Audio Pulsar, Stereophile’s measurements show it to have impedance characteristics that are more tube-friendly than the LS50’s, but its sensitivity is even lower than the LS50’s, making power capability an even more important consideration. Good luck. Regards, -- Al |
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