04-11-14: Atmasphere'Stable' means that the amp won't oscillate when presented with the load in question. Stable is a given with any amp, you may have missed the rest of the Martin Logan quote for the type of amp they recommend for their speakers. And to get these sort of figures, the amps need low output impedance, to get it. So here it is again. " Be able to deliver NEARLY twice its rated 8 Ohm wattage into 4 Ohms, and should again increase into 2 Ohms." In other words for the uninitiated, what's needed is an amp that can ALMOST double it's 8ohm wattage for each halving of load. EG: 8ohm-100watts 4ohm-200watts 2ohm-400watts Cheers George |
I would like to thank Jan Didden for laying this furfie "NF feedback DOES NOT effect Z=out or damping factor" out in the open, in his usual calm and palpable way. His is a bottomless pit of correct information over at the much more techincal forums, along with the usual others like Nelson Pass, John Curl, and many others, there should be more of them to police bad info on forums. http://www.wordsense.eu/furfie/Cheers George |
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I certainly did not derail the topic Atmasphere, the OP asked for suggestions for tube amps to go with his Martin Logan speakers. I simply mentioned in my first post that they are a difficult load, no mention ever of him getting a SS amp ever, you are seeing things.
It was you Atmasphere that started spruiking on about the Zero from your first post, instead of guiding the OP correctly to a suitable amp.
It was also you Atmasphere that said, "that others said", (never implicating yourself) that the Zero is beneficial to all amps "even good solid state amps" into these kinds of loads.
You call me a troll twice now. Be careful Atmasphere, It almost looks like your shilling for the Zero, because your amps are the ones that need them the most, and visa versa, the Zero's need your amp's the most. as this quote from Paul Speltz from a TNT review of the Zero's
"Paul Speltz, a devotee of OTL amps, decided that he wanted to use his favourite DIY speakers with his OTL amp, but the nominal speaker impedance of 4 ohms wasn't a good match for his amp. With these thoughts in mind, Paul designed the ZERO Autoformer"
And then this quote from the TNT reviewer on the Zero's with amps that don't need them.
" The most important thing to remember about the ZERO Autoformers is: if there is no significant impedance mismatch, then there will be no real benefit to using the ZEROs. For example, when the Autoformers were connected as an impedance multiplier to a pair of B&W DM602 speakers there was little benefit for most tested amplifiers. In fact, the Le Amps and B&W combination sounded a little too bright with a strident sibilance that was distinctly irritating."
As I've always stated the Zero's add their own set of problems that can be clearly heard when the amp/speaker combo does not need them. (as the above reviewer found)
And to suggest they are beneficial for all amps into hard loads is an absolute misguided quote.
They are a bandaid fix for owners that do not want to change their amp or speakers so they are compatible.
Cheers George
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From here Al. At the The Manley website. http://www.manley.com/msn.php Features and Specifications Manley Snapper Damping Factor: 4.7 Cheers George |
03-31-14: Tomcy6
Of course not every amp can handle the job when you've got a speaker that has an impedance of .5 ohms at 20khz. But you don't need a lot of power to reproduce most musical content at 20khz either. True, but if the amp cannot keep constant voltage at 20khz it will result in the treble being shelved down no matter what volume level you are listening to, resulting in a softened treble, some unexperienced might call this smoother, but their having themselves on. (as the sterophile test reports state) Quote Sterophile: " The shape of the impedance trace will result in the Montis's top octaves shelving down when the speaker is driven by a tube amplifier having a high source impedance. This is why Robert Deutsch found that his Audiopax amplifier sounded too soft and lacking in definition." Cheers George |
I used to build many SS Class A amps some water cooled back in the 80's 90's they were along the same lines as the ML ML2's but stereo and not such a "bomb or hydroelectric plant" as you guys put it. But they could almost double as well all the way to 2ohm.
I had a led light on the front that used to flash on transients at I think it was 32v (for my Quad 57 owners) this saved my customers from arcing the panels.
90% of my customers were Quad 57 owners, they had never heard their Quads sound so good.
None went back to tubes or SS that couldn't drive the Quad's with a constant near linear voltage across the audio band. Which means for those, an amp that can "almost" double it's wattage for each halving of load impeadnce from 8ohm down to 1ohm
PS Exactly doubling wattage for each halving of impedance is impossible, the ML2's stretch the truth a little with those specs above, but they come close.
Cheers George |
03-28-14: Mapman
My understanding is low impedance in treble region does not present nearly as much of a challenge as same in bass in that exponentially less power is needed for flat treble response. I think that is the main reason why tube amps can do well with those. It will work into that load, but will be "as JA put it" "shelved down in the treble in this instance". This "could" give you the initial impression of a sweeter treble. In otherwords it will do the classic thing that can happen with low current or high output impedance tube amps "behave like a fixed tone control" instead of being flat into all loads. This is where the Zero can be a bandaid fix, but I always believe it's better to fix the problem, by changing the amp or speakers to something that are compatible with each other, than to mask the problem by introdcing a pseudo fix that has it's own set of problems. Cheers George |
I do not manufacture amps that may or may not need the Zero in circuit, so there are no ulterior motives for me to hide or protect. I just don't like to see blanket statements like the Zero will improve all amplifiers regardless of topology. They have their place in that they make an amp that has trouble to drive certain loads with relative ease, able to do so. But it is not the definitive answer, it is a bandaid fix, changing the amp/s or speakers is the way to go in these cases. Here is another point made from Dick Osher's review of the Zero Autoformer that was conveniently left out of the link to the excerpt of the review. "T-Rex 300B SET, a DIY design project in the works (still unpublished) using Plitron output transformers with only 8-ohm taps, and the Lowther DX4 BassZilla - a 97dB.
At his point, it became clear that although bass lines still benefited from the ZERO, overall the T-Rex - BassZilla interface sounded better with the ZERO out of the way."
"Small, but noticeable errors of commission crept in. Soundstage transparency diminished, which reduced the music's intimacy. Microdynamics now sounded slightly over damped, releasing some of the music's tension. The midrange, which for me paints a window onto the music's soul, became slightly cloudier. On balance, I would rather give up 20% of bass definition for a 10% increase in midrange clarity.": As you can read the 300B set amp (and others eg OTL's) not known for good drive current, was improved in the bass area with the Zero, but the midrange diminished by 10% The same 10% detriment will happen to the midrange using a Zero with a good solid state amp or powerful tube amp that have no problem in delivering good bass without the Zero. The word Dick Olsher used "cloudy" in reference to the midrange is also what I heard in my system with the Zero's attached to a good SS amp that could drive the speakers with no problems, and as well as the bass tightness and drive diminished just as much with it in. Cheers George |
03-26-14: Atmasphere
This can be so significant that the use of an autoformer to raise the load impedance to an otherwise very capable solid state amplifier can result in improved sound. Were this not the case, the insertion of the autoformer would have adverse effects.
OMG, it does, if the listener had ears. I've tried them on a very capable ss amp, and the sound took a bad turn for the worse. Quotes: from the Dick Olsher review that was convienently left out of the excerpts of the reveiw of the link you provided on the Zero website, read between the lines, we all know that reviewers don't like to rock the boat too much. "It is not a panacea, and as you can see from my experience, it does not always pan out. However, if you're the proud owner of an OTL or a low-power tube amplifier and presently driving a 4-ohm loudspeaker load, you owe it to yourself to give the ZERO a try." Cheers George |
03-21-14: Atmasphere:George, you are a troll. Your comments are unwarranted, without merit and uncalled for.
There is only one reason for you calling me a troll, that is you have to stick up for the Zero Transformers, because they are the only way your OTL's will drive many semi difficult speaker loads that are out there. And I stand by my comments about them, they are a bandaid fix for amps that cannot drive difficult loads, and the owner is better off getting the right amp, or an easier load impedance speaker. I have actually praised your OTL amps, when they are mated to the right speaker, but to put a Zero Transformer on them is just defeating the fact they are OTL in the first place. http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1304533364&openfrom&23&4#23 Then your suggestion of putting a Zero on a tube amp that already has an output transformer is just plain stupid, instead of getting the right amp or speakers. And then to infer to putting them on a good quality solid state amp is just **************** Cheers George |
That's because the McIntosh 275 has quite a low output impedance for a tube P/P amp at .57ohms from the 8ohm tap.(probably has a fare amount of negative feedback)
But the Montis would still be a hard load for many amps as John Alexander's measurements state
" The shape of the impedance trace will result in the Montis's top octaves shelving down when the speaker is driven by a tube amplifier having a high source impedance. This is why Robert Deutsch found that his Audiopax amplifier sounded too soft and lacking in definition."
Cheers George |
03-17-14: Unsound: Once again I disagree with Atmasphere's oft-repeated assertion Agreed, I have yet to listen to a Zero Autoformer that has worked without causing other problems. A simple way to hear what they do wrong, is to put one between an amp that has no problem driving the speakers/load with out it. Then you will hear what they do wrong with it in. In my view they are a bandaid fix to allow an amp that has no chance of driving the speaker by it's self, to make it usable with that speaker. And I use the word usable lightly. Far better off getting the right amp for the said speaker to start with. Cheers George |
Atmasphere: George, take a take a look at the links on this page: I have Ralph, and I stand by what I said, I have even put them on my system which definitely doesn't need them, and the sound took a big step backward. They are sometimes a "recommendation" for OTL's as they allow them to drive speaker that would not otherwise be a good match for. Best off changing the amps or the speakers. ""They are a bandaid fix to allow an amp that has no chance of driving the speaker by it's self, to make it usable with that speaker." Cheers George |
A simple way to hear what negative effects they have, is to put them on an amp that has no problem driving a speaker.
Then you will hear what negative effects they have when they are in.
In my view they are interim fix, to allow an amp that has problems driving the speaker, to make it usable with that speaker. And I use the word "usable" lightly.
A owner is far better off getting the right amp for the speaker, or the right speaker for that amp to start with.
Cheers George
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I've had a pair of Zero's given to me, to me they are a band aid fix for an amp that not right for the speaker it's being use on, and the disadvantages far outweigh the advantages.
Your far better off getting the right amp for that speaker.
PS: I gave the Zero's away as well.
Cheers George
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Yes Al and that why I say a Quad 57 is voiced around a low power low current tube amp, but with Martin Logan's statement:
"Quote:
However, it is important that the amplifier be stable operating into varying impedance loads: an ideally stable amplifier will typically be able to deliver nearly twice its rated 8 Ohm wattage into 4 Ohms, and should again increase into 2 Ohms." Quote:
This is why my ML Monoliths have very subdued/rolled off character in the uppermid/highs and dynamics when driven from my tube Rogue 120 monoblocks.
Yet they sound perfect and well extended when driven by my big current pushing solid state monoblock amps.
Cheers George
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Here is an Audio Research Reference 150 considered by many to be a tube amp with better drive than most. It's only being asked to drive 2.83v hardly taxing. Look at the black trace in the link, this is Sterophile's simulated (rather easy speaker load), the 150 is having a hard time staying flat.(I can show you an impedance graph of their simulated speaker load, I have it somewhere it's not as nasty as the ML's) Then look what happens to it when it has to drive a straight 2ohm load (green trace) it's really starting to take a dive in the upper mids/highs. What do you think will happen to the highs into a 1ohm capacitive load of the ML's http://www.stereophile.com/content/audio-research-reference-150-power-amplifier-measurements#dgk5iym3Akuwqg5H.97Cheers George |
An amp like say a Krell or similar, will remain almost flat in it's response across the frequency spectrum.
All you need to do is look at the simulated speaker load graphs of amps at 1/3 power on Stereophile to see what happens to them if they have, high'ish output impedance or can't deliver current, many tube amps exhibit this, and even many Mosfets, they are far from the ideal flat.
And the simulated speaker load that Stereophile uses is not as savage as what we're talking about here with the ML's, and things like Wilson Watt/puppy, Alexandria etc.
Cheers George
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Sorry guys amp that can't keep it's end up at those 1ohms loads, will not have a flat frequency response from 20hz to 20khz no matter what level it's being played at. It becomes a tone control, end of story.
Cheers George
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"important to know whether the ESL was voiced to be driven by a SS or tube amp."
I own myself a pair of ML Monoliths III's with quite new fresh panels.
If I drive them with a my pair of Rogue 120 tube amps, they have highs but they are very distant and too polite, if I drive them with my solid state amps (similar to big Krells) low output impedance and gobs of current the high are where they should be and you know all about cymbal crashes.
And this thread is about the right amp for ML's not Quad 57, which I agree were most probably voiced with low power tube amps.
For Martin Logan to mention an amp should double into 4 from 8 and then increase again into 2ohm, this means current. And they also want one that's stable into capacitive loads like ESL's.
And lets face it a stable amp can be a 5 watter and have no current ability, so long as it doesn't ring or oscillate it's stable, current ability has nothing to do with stability into capacitive loads as ESL present.
Cheers George
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The fact is they want an amp that are stable and also that can double it's wattage from 8ohms down to 4 ohms and yet still increase even to 2ohms, (which means an amp that can do good current)
This means that if an amp cannot do this, then at the low 1ohms or 2ohms that their (ML) speakers present to an amp, then that amp will then start to behave like a tone control, and not stay flat in frequency response over the entire impedance range of speaker it's driving.
As simulated speaker load graphs will show you of amps that cannot deliver current at those low loads, therefore their frequency response will not be flat.
All you have to do is look at Stereophile speaker simulated load graphs of tube amps especially to see that they cannot give a flat frequency response into those types of loads, especially ones that dip down to 1ohms.
If you need proof I will post links for you to see what happens, but I think you should go and look for yourself.
Cheers George
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Once again from the Martin Logan website. They should know their own speakers.
"Quote:
However, it is important that the amplifier be stable operating into varying impedance loads: an ideally stable amplifier will typically be able to deliver nearly twice its rated 8 Ohm wattage into 4 Ohms, and should again increase into 2 Ohms." Quote:
Cheers George
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From the Marin Logan website:
Quote:
However, it is important that the amplifier be stable operating into varying impedance loads: an ideally stable amplifier will typically be able to deliver nearly twice its rated 8 Ohm wattage into 4 Ohms, and should again increase into 2 Ohms. Quote:
Cheers George
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Almarg/Unsound/Bifwyne: Looking at these figures again the Snapper's speaker termianls are a 7ohm tap to be pedantic about it.
Cheers George |
Unsound: I just looked at the Snapper owners manual, and it states the output impedance is 1.5ohm, so the tap is less than 8ohms but more than true 4ohms.
This 1.5ohms output impedance was also measured and verified by Sound and Vision review of the Snapper.
Cheers George |
Bifwynne, the Manley Snapper from the website looks as though it has 1 set of 8ohm speaker terminals?.
It states in the specs that it's damping factor is 4.7 (into 8ohms?) which would mean it's output impedance is around 1.7ohms. If it's a 4ohm tap which I doubt, then the output impedance is .85ohm.
Cheers George |
You'd be far better off saving the $1140us for the Zero's and putting towards the right amp or speakers, instead of masking the problem with the Zero's, which itself has it's own set of problems.
Cheers George |
OK Almarg, I'll split hairs with you.
With a measured damping factor of 4.7 and an output impedance of 1.5ohms it's closer to an 8ohm tap than a 4ohm tap.
But all this can change with a bit more global feed back to raise the damping factor and lower the output impedance.
But then Audiophiles don't like the idea of too much feedback, so throw a Zero on it for difficult loads like these speakers the OP has and maybe be happy???
Cheers George |
03-30-14: Tomcy6
Someone should tell Martin Logan about all this. Those idiots are telling people that their speakers can be used with a wide variety of tube and solid state amps. Some tubes can drive them without becomming too much of a "fixed tone control" (ie: not flat from 20hz to 20khz), but they need low output impedance to do it, below say 1ohm from 20hz-20khz) like ones I metioned earier, which usually have a fare amount of negative feedback on them to keep them below 1ohm output impedance. They also need to back it up with a bit of watts also. Cheers George |
03-29-14: Tomcy6
I think that ML designed their current line to be used with either tube or ss amps, the choice being the user's. Yet if you Google images for previous big HiFi shows, and look at specific Martin Logan rooms demo's, as far as I saw nearly evey demo by ML was done with big SS amps like Krell and such. The only ones I saw driven by tubes were not in a Martin Logan rooms, but were in an tube amp manufacturers rooms, who were using ML powered bass hybrids for their speakers. Cheers George |
Like a pair of these classic, Class A Mark Levinson ML2's 25w monoblocks. http://www.wtconcept.com/levinsonml2/ 25w into 8ohm 50w into 4ohm 100w into 2ohm 200w into 1ohm 400w into .5ohm There's 20watts and then there's 20watts, "no tone control behaviour with these", dead flat frequency response drive to any speaker from .5ohm to 100ohm loading. Cheers George |
Mapman, I just noticed that you have class D amps as powerful as they are don't think they are out of the woods when it comes to driving ESL's Their achilees heel is driving low impedances in high frequencies, they behave in a similar fashion. Just look at the black trace that is the frequency response of the Belcanto Ref1000 driving a simulated speaker load, see how it goes all wonky, it should be flat, and that load is no where near as severe as an ESL load in the HF. http://www.stereophile.com/content/bel-canto-ref1000m-monoblock-power-amplifier-measurementsCheers George |
All depends on which way you look at it Al.
Saying it's "optimised" for a 5ohm speaker does not mean it's a 5ohm tap.
But giving figures as exact as in 1/10th's, 4.7 for damping and 1.5ohm for output to me is far more exacting.
And from these two figures the tap is closer to an 8ohm tap than 4ohms.
Whatever the case, the way your seeing it, or me, it's not the ideal amp for what the OP has.
Cheers George |
03-27-14: Atmasphere: do so despite George's remonstrations Are you kidding, far from pleading with you Ralph. I agree that an Autoformer is a great (pseudo) bandaid fix for whatever amp that cannot drive a speaker that is not a good match, because of it's inability to deliver current/wattage or is working out of it's SOA (safe operating area) A FAR BETTER FIX IS TO CHANGE THE AMP/S OR SPEAKERS! You state that even a good solid state amp will measure less distortion on it's output from using a Zero Autoformer into a 4ohm load compared to 8ohm. Yes I agree that with the Autoformer even a good solid state amp will measure slightly less distortion at it's output terminals at 4ohms (this is not to say it's out of it's SOA) But it's what happens after the Autoformer (things like phase shifts, damping factor etc) that is far more detrimental to the sound than the slight increase in distortion before it without the Autoformer. EG: What one would basically do to a good amp say like a Pass Labs, Krell, Gryphone or similar amp by sticking an Autoformer on it, is to turn it into the solid state series MacIntosh's that also use a type of Autoformer on their outputs, but without the benifits of using them within the amps feedback loop, to keep the (damping factor, phase shifts, etc) in check. Cheers George |
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Ralph: why not just put some output transformers on your OTL's so they can drive these types of loads then, instead of this band aid fix of the Zero's
Or the owner can do one of two things to fix the problem.
1: Is to get the right amp to drive said speaker load.
2: Is to get the right speaker with a load so amp can drive it.
And the suggestion to put this Zero transformer on a tube amp that already has an output transformer is one of the worst ways of fixing/masking the problem.
Cheers George |
The ML Arias dip to between 3ohm and below 2ohm between 10khz and 20khz with a not so easy phase angle of -35degrees.
This says to me you'll need an amp that is happy driving a moderately hard load.
If the amp cannot handle that load happily, it may start to sound a little rolled off in the top end as power droops off, compared to what it's doing down lower in the frequency.
eg: it will act like a bit of a fixed tone control, instead of being flat from 20hz to 20khz.
http://www.stereophile.com/images/archivesart/IIMPfig7.jpg
Cheers George |
