Tube guy: only tubes sound good
SS guy: jump on the transistors, tubes are the pits.
Where is the truth?
Where it almost always is. Somewhere in the middle.
Myself I choose to shy away from tubes whenever possible. Too many headaches. But I still have some. Go figure. I'd love to ditch them all but at least the ones I have sound good plus of course tube gear is way cooler than not and you can't roll transistors to get the sound you want, but there are many ways to tweak besides twiddling with tubes. |
^It works the same in both directions, and global feedback is not neccesarily a prerequisite. If the output impedance of the amp is low enough then feedback is not required. An example is the Ayre amplifier. An example of a tube amp that acts as a voltage source is a Mac 30 from 55 years ago. |
^I'm not familiar with the Mac 30. If that were the case, why would it have multiple impedance taps?
http://www.roger-russell.com/amplif1.htm#mc30 |
^^ If the impedance of the speaker is too low the output power of the amplifier will be lower and distortion higher. The lower impedance taps are provided to deal with this. It might interested you to know that the voltage rules that we are talking about ( http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php) were initially laid out by Electro Voice and MacIntosh back in the days when tubes were king (late 1950s). |
^Them it would appear that the Mac 30 is not capable of adapting to the variable impedance swings of typical loudspeakers without deviating from linear frequency response? |
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They both sound very close to real music, if done properly. |
It would not be hard to fool most anyone by doing a blind listening test of chosen tube versus solid state gear. The devil is always in the details ie design, build quailty, quality assurance etc. Only audiophiles care about debating tubes versus SS. They are a finicky bunch and each has found their own nirvana no two of which are likely to sound exactly the same. |
And who would the most appropriate subject of an ABX test be? IOW, how many ss guys care about similarity vs how many tube guys care. Ime, the ss guys only want it to sound good while the tube guys want a distinct characteristic sound. Another pertinent question could be, how many tube guys agree to be ABX tested vs how many ss guys agree; strictly for the purpose of distinguishing tube from ss.
I have a great pair of W5-M monos with matching pres and a pair of Electrohome 7189 monos that sound really good. But I also have a GAS500, two pairs of LSR&D Superamp monos, and two Leach 125wpch stereo amps that imo surpass the tubes in sq. Not to mention the huge power differences. But like I mentioned earlier, ime the ss need to be cranked to really perform while the tubes do not. And I truly believe that's where the apples to apples comparison lives. |
Tubes become a more desirable option to me if lower volume listening will be the norm.
It's certainly doable but I would not bother with a tube amp if higher volume listening is the norm. That's just me. Too many special considerations when putting a system designed to go loud and clear together. Some might consider it fun or preferable but I don't see any clear advantage in most cases.
I would also agree that tube lovers might often be motivated by the quest for a certain special kind of sound more so than just good clean sound. |
Bottom line is its more about what one is after than the technology itself. Both at their best sound more similar than different but each also does its thing best differently. That's pretty much what makes the world go around. |
^Them it would appear that the Mac 30 is not capable of adapting to the variable impedance swings of typical loudspeakers without deviating from linear frequency response? No, not at all, unless the amp is set up on the wrong tap. If the speaker is 4 ohms in the bass and 8 or 16 ohms in the highs, you put it on the 4 ohm tap and the bass will be correct as well as the highs. It will be just as flat as a transistor amp on the same speaker. |
^So for example; with a dynamic loudspeaker speaker with a nominal 8 Ohm load with dips to 4 Ohms and peaks to 16 Ohms; the Mac 30 will double it's power output into 4 Ohms and halve it's power output into 16 Ohms? |
^^ The nature of the dips should be examined. If at crossover points which is a common point of a dip, they will be of no consequence.
The amplifier power will be signal dependent of course, and the output into 8 ohms will be 1/2 of its 4 ohm power (30 watts) and 1/4 of that into 16 ohms if the signal is full bandwidth.
IOW, feedback causes an adaptive response in the amplifier. |
^Well that is interesting.
I'd love to see the graphs of the tests on that amp, as I've never seen a graph of a tube amp that could demonstrate that kind of skill. I'm very curious as to what it's distortion levels were like as it went through various impedances. It still seems as though it wouldn't need the various impedance output taps? Why wouldn't the cross-over points matter? Is that how the amp would behave when connected to the 8 Ohm tap (the given speakers nominal impedance). |
Actually there are a good number of tube amps that can do that. Any Mac for example. Ever hear of the Wolcott? Henry made a point of advertising that his amp could operate as a true voltage source.
All amps have higher distortion into lower impedances. As far as that goes, there is no argument for a 4 ohms speaker in the world of high end, not if sound quality is your goal. Why force all amps to have higher distortion??
You still need the impedance taps otherwise you may not be getting the most out of the amp. |
As I read it from their own respective web sites none of the amps from either McIntosh or Wolcott can do that.
http://www.mcintoshlabs.com/us/Products/pages/ProductListingHorizontal.aspx?CatId=amplifiers
http://www.wolcottaudio.com/WA_Pres_specs.htm
I disagree with your assertion that :"...there is no argument for a 4 Ohm speaker in the world of high end,..."
Some of the most accurate loudspeakers ever made journey into and below that impedance. ...But that is probably a more appropriate discussion for another thread. |
You didn't look deep enough. From the Wolcott site: http://www.wolcottaudio.com/WA_presence.htm: What if we told you that our very different tube amplifier had highly accurate autobiasing, a nearly infinite damping factor, acted as a pure voltage source into almost any real world speaker load, |
Well, I would respond to the Wolcott statement that the specs on their own web site contradicts that. |
I don't see anything that supports your statement- perhaps you could point it out? |
Look deeper, or at least to the first Wolcott link showing specs that I provided on 04-03-15:
http://www.wolcottaudio.com/WA_Pres_specs.htm |
To cut to the chase here, I think that what is contributing to the disagreements in the recent posts is that the protagonists are focusing on two different things. Unsound is focusing, I believe, on the how the MAXIMUM power ratings of the McIntosh and Wolcott amplifiers vary as a function of load impedance. Ralph is focusing, I believe, on how the power outputs of those amplifiers will vary as a function of load impedance when those amplifiers are operated WITHIN their maximum limits.
If those amplifiers are operated within the limits of their output voltage, output current, output power, and thermal capabilities, their high damping factors (made possible by the use of feedback) will cause them to behave as if they have the very low output impedances which by definition characterize a voltage source. Especially in the case of the Wolcott (damping factor >500), and to a lesser but still reasonably close approximation in the case of the MC's (MC30 damping factor 12; recent version MC75 damping factor 18; recent version MC275 damping factor 22).
Provided that the amp is operated within its limits, a damping factor of 22 will cause the 4 ohm tap of the MC275 to behave as if its output impedance is 4/22 = 0.18 ohms. To a close approximation that is negligible in comparison with most speaker impedances, which will therefore result in essentially negligible variation of output voltage as a function of load impedance. Which in turn will result in output power increasing in proportion to decreasing load impedance. Provided, again, that the amp is operated within its limits.
The fact that the amplifier's MAXIMUM rated power does not increase substantially (or at all) into decreasing load impedances, as would be the case for a solid state amp (up to a point), is unrelated to that but I believe underlies the disconnects in the discussion.
Regards,
-- Al
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Al, thank you for clearing that up.
I will say that there I still have some misgivings about power rating and the ability to adapt to lower impedances of the above mentioned tube amps, as the sensitivity varies in a constant ratio to the impedance of typical loudspeakers.
To put in this context (using Al's reference to MAXIMUM power output), the more robust of the amps under discussion (and perhaps of all tube amps?); the somewhat unique Wolcott's standard 8 Ohm power rating of 180 Watts when outputting into a 2 Ohm load would be the equivalent of a 60 Watts standard 8 Ohm power rating of a high quality solid state power amp. |
Hi Unsound,
Yes, it's true that some robustly designed solid state amps rated at 60 watts into 8 ohms will be able to supply 240 watts into 2 ohms, while the Wolcott's 180 watt rating into 8 ohms increases only slightly into 2 ohms, to that 240 watt value.
As I said earlier, though, as long as the amps are operated within their maximum capabilities, those maximum ratings will not be relevant to how their output power varies as a function of load impedance. What that variation will depend on is their effective output impedance ("effective" referring to the fact that feedback is taken into account), which btw equals speaker impedance divided by the amplifier's damping factor. If that output impedance is negligibly small in relation to speaker impedance, corresponding to a high damping factor, there will be essentially no variation of output power as load impedance varies, within the limits of the amp's maximum voltage, current, power, and thermal capabilities.
The extremely high damping factor of the Wolcott puts it firmly in solid state territory in that respect. And the highish damping factors of the MC's (relative to most tube amps) will have a similar effect, although to a somewhat looser approximation.
In saying all of this, btw, I'm ignoring the fact that the max power ratings of different amplifiers may not be precisely comparable, as a result of having been measured based on different standards, with different pre-conditioning warmups, different distortion levels, etc. But those are separate issues, not specifically related to tube vs. solid state.
Best regards,
-- Al
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04-11-15: Almarg
If that output impedance is negligibly small in relation to speaker impedance, corresponding to a high damping factor, there will be essentially no variation of output power as load impedance varies, within the limits of the amp's maximum voltage, current, power, and thermal capabilities. Sorry. That sentence was of course completely misstated. I meant to say that there will be essentially no difference between the tube and solid state amps in their variation of output power as a function of load impedance, as long as the amps are operated within their maximum capabilities. Best regards, -- Al |
That maximum power output is not to be considered lightly. That uniquely(!) robust Wolcott's maximum power rating is for full stereo output. As a typical speakers sensitivity will be reduced at a greater rate than power output is increased by such an amp. At up to over $9K for the equivalent of a well designed 30 Watt per channel ss amp is cause for pause and serious thought, at least for me :-). |
A correction is in orde. After looking at the Wolcott specsheet again it appears as though both stereo and mono amps are available, with different maximum power outputs. |
