I'm dyslexic and don't read a lot of tests, but the plain ol' resister doesn't sound good. |
Darn good question....and I have NO answer. You'd think if a manufacturer were proud of a top amp, they take the data and Brag.
Considering the cost of electronic test equipment, this would be a drop in the bucket. Stereophile even skips this test. A plain old resistor is good enough for them!
OTOH, Who the heck knows how to interpret this data except for some fringe tehno-geek types?
Than what would happen of some highly regarded amps crapped out in this test?
When testing a tube amp, should you change taps as you change load impedance?
What about tube amps not being happy with capacitive loads? (I think this is right, and it isn't inductive) |
Magfan, looks interesting. Do you know any reviews in which it has been used? |
I don't know about impedance matching, but if you want a high damping factor the idea is to get speaker / amp impedance pretty much as far apart as possible.
4/8 ohm switch or taps on SS? Maybe to limit power into lower impedance loads to make up for an inadequate PS.
The 'best' load for an amp? Probably a resistor. Than it turns into degrees and how well an amp handles reactive loading.
Check out the link to the 'power cube'...not an amp, but a measuring system.
As always, good specs DO NOT guarantee good sound.
http://www.audiograph.se/Downloads/PowerCube_12p_brochure_complete.pdf |
Rrog, An example in ss amps is the Harman Kardon amp(s) in the Citation series years ago when hk abandoned their decent quality American-made amps for the Japanese-made lower quality amps after they bought Levinson. Not that there's anything wrong with Japanese-made per say. I think their 4-8ohm taps were to compensate for a less muscular amp that could not handle a 4 ohm load except at the expense of sound quality. And I think this device in ss is sometimes used to compensate for an anemic amp. I'm always suspicious when I see this device in ss, but I realize it has its place. My predjudice also comes from my dislike of switches which degrade sound quality.
I apparently didn't articulate my initial point very well because I surely don't have anything against using the tap that sounds the best as long as it doesn't cause damage to the amp. That's kinda the whole point of the tap. I don't have a technical background as some of you know, but I do understand in general impedence matching of amp and speakers. There is an optimum load for every amp. That is the point of the taps and the point of autoformers, a device used to find that optimum load. Lynne |
And to complicate matters a little bit with what will likely be a footnote to the discussion, it should be mentioned that output transformerless (OTL) amps actually increase their output power into higher impedance speakers. Atma-sphere amps are the most well-known OTL amps although there are also OTLs from Tenor, Transcendent (incl kits) and others.
This makes Speltz autoformers particularly helpful with these OTL amps, although as the Speltz site testimony makes clear the autoformers can improve sounds with other amps as well. |
What Plato describes regarding the bass is the effect I get when light loading my Music Reference RM-10 MkII. The loss of power is minimal as well, roughly 20%, so it runs at around 28 watts versus 35 watts. That's pretty negligible with my speakers since they are fairly efficient with a very smooth impedance curve.
Now my Music Reference EM-7 v12 amps can be configured for 3 ohm or 12 ohm output and I have tried both. Again, the lower output exhibited tighter bass and less distortion. However, with these amps I prefer the higher output. |
Magfan, I think you read my comment wrong regarding me saying you'd get "looser bass with the 4-ohm taps." Perhaps I didn't make it clear but the 4-ohm taps (compared to the 8-ohm) would increase damping factor for tighter bass. Distortion would also be less using an 8-ohm speaker on the 4-ohm amp taps. I said the bass would be looser using the 8 ohm taps, and that the 8-ohm sound may be sweeter though less focused/precise, but that some folks might still prefer it that way. |
And yet, nobody has said a single word about reactance. This is implied when taking about impedance. Tube amps do not like capactive loads. period. I hope I got that right.
A 'flat' impedance curve? I've never seen one. If their are any crossover components at all, the speaker should 'swing' from capactive to inductive at some point, shouldn't it?
I think damping may be called on for Plato's above comment about 'looser bass' when using 4 ohm taps. With the whole amp OFF, how much resistance would I measure on 4 ohm or 8 ohm taps?
Other than that? Plato makes sense. Use whichever tap you like. I'd add that if the amp runs too hot while using the 4 ohm taps, I'd reconsider either amp or speakers. |
Okay, I see a lot of erroneous info flying around in this thread. A 4-ohm load is a lower impedance and thus a tougher load for an amp to drive (not easier).
Some confusion creeping in here involves the typical solid-state vs tubes. Typically, solid-state amps have more power driving into lower impedance loads, in fact, many of them double power into 4-ohms (this does not mean they sound better driving 4-ohms). Tubes, on the other hand (which is what we're talking about here) are typically optimised to drive 8-ohm loads, with some optimised for closer to 4 ohms.
This means that many tube amps will deliver a bit more power into 8-ohms than they will into 4-ohms. In most cases, the actual power difference is small, unlike solid-state.
That said, if you use a tube amp's 4-ohm taps to drive 8-ohm speakers it does increase damping factor and decrease distortion. In some cases, this can sound "better" to the listener, and in other cases it can sound "dryer" and more like solid-state. Sometimes the little extra distortion and looser bass is preferable to some listeners, because it usually gives a sweeter, though less focused, sound.
In this particular case, the results probably have to do with the tube amp being optimised to drive closer to a 4-ohm impedance coupled with this particular listener's personal bias. And of course interaction with the impedance curve of the particular speaker will come into play. This is why amplifiers can sound different when driving different speakers. |
Arnettpartners,
"I have a problem with manufacturer's using taps for reasons other than sound quality (in SS. Have no experience with tubes). Skip the taps and design it to perform well under varying conditions for about 20 years. That's just me and yet another issue not related to the question."
Can you give an example? |
The manufacturer's claims of the Nightingale speakers and the difference in quality between the 4-ohm/8ohm settings on amps so equipped are separate issues since these taps affect the sound quality driving any speaker. As a user, sound quality is the whole point for me.
I have a problem with manufacturer's using taps for reasons other than sound quality (in SS. Have no experience with tubes). Skip the taps and design it to perform well under varying conditions for about 20 years. That's just me and yet another issue not related to the question. |
A linear impedance is not necessarily a constant impedance. For instance, a speaker having an impedance of 2 ohms at 20Hz, and 20 ohms at 20kHz, could still be described as having a linear impedance, if a plot of that variation approximated a straight line.
Without a detailed impedance plot, which doesn't seem to be available as far as I can tell via a Google search, their statement about maintaining a linear impedance tells us essentially nothing.
I agree with the suggestions to just go with what sounds best.
Regards,
-- Al |
The output tubes or transistors will see less of a load using the 4 ohm tap, perhaps maybe half of what it would using the 8 ohm tap. That is the purpose of output transformers (impedance matching), and autoformers.
Hifihvn (Answers | This Thread) I agree with this. As I agree with Hifihvn. Another good explanation is offered by Roger Modjeski who recommends trying "light loading"his the RM-10 MkII amps. There is a pretty clear explanation as to why in the owners manual. Lower distortion and longer tube life being a couple benefits, at least where the RM-10 MkII is concerned. |
The 4 ohm tap was recommended, the 4 ohm tap sounds better, I use the 4 ohm tap, case closed.
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Which relates to damping factor. Yes? |
VTL/Manley have always set their amps at 5.5 ohms. |
A lot of amps like to see a higher impedance on their outputs, and do sound better this way. One tube amp company was using only a 4 ohm tap at their outputs for this reason. |
The output tubes or transistors will see less of a load using the 4 ohm tap, perhaps maybe half of what it would using the 8 ohm tap. That is the purpose of output transformers (impedance matching), and autoformers. |
Clear. I will not bother with the theory any more and will listen to what seems best. |
I am not sure it is possible to construct a speaker with a constant impedance, I have never seen one tested that did not have some variation. Their statement sounds like typical hype to me. |
I have experienced this too. I believe it comes down to personal preference. |
Plato, then what is the purpose of a 4 ohm-8 ohm option on an amplifier? Lynne |
This doesn't make sense to me and what Arnettpartners said doesn't make sense either. So just accept it as one of those weird audio interaction anomalies that works for some unexplained reason. Perhaps the maker of your amp or the maker of the speakers could shed some light on this.
Personally I wouldn't lose sleep over it. I'd just use the amp on whichever speaker taps sound best with your speakers. Surely it won't hurt anything.
If you find out the actual reason down the road shoot me an e-mail and let me know. |
A 4 ohm setting increases the impedence that the amplifier sees relative to an 8 ohm setting. Therefore, fewer demands are placed on the amplifier and therefore if the 8 ohm setting is too demanding for the amp it will sound better on a 4 ohm setting. The principle is the one that applies to Paul Speltz's automformers which increase the impedence that the amp sees and will improve the amp's performance up to the point where the impedence is great enough so that it limits the potential of the amp. It's a matter of matching amp to speakers. A more muscular amp than the ones you have auditioned might reach its potential better on the 8 ohm setting. It's an interesting and instructive excercise. |
