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  1. #1
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    Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Looking for recommendations for a client.

    Please - submissions not from hearsay, but from actual user experience - Thanks!
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  2. #2

    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    ah - easy .....

    Audio Flight Strumento 4 or mono Strumento 8's

  3. #3
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Pair of Lumin AMP in bridge mode.
    Peter Lie
    LUMIN Firmware Lead

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    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Luxman M900u. Stable to 1ohm.


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  5. #5
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    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Well my Purifi amp has an output impedance of 67 microOhms and, per specs, is fine with 2 Ohm loads, delivering 450 watts

    Accordingly Damping factor at 2 Ohms = 29,851, which poor if you like flabby bass
    Last edited by Feanor; September 2, 2021 at 08:34 AM. Reason: clarification
    ~ Bill

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  6. #6
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    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Quote Originally Posted by Jim Smith View Post
    Looking for recommendations for a client.

    Please - submissions not from hearsay, but from actual user experience - Thanks!
    Whats the load Jim and desired listening levels ...?
    * An Audiophile is only as old as his tweeters ..!!

  7. #7
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    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Quote Originally Posted by Jim Smith View Post
    Looking for recommendations for a client.

    Please - submissions not from hearsay, but from actual user experience - Thanks!
    Ah ... so client endorsements are not hearsay: I'm informed.
    ~ Bill

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  8. #8
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    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Quote Originally Posted by Feanor View Post
    Well my Purifi amp has an output impedance of 67 microOhms and, per specs, is fine with 2 Ohm loads, delivering 450 watts

    Accordingly Damping factor at 2 Ohms = 29,851, which poor if you like flabby bass
    Doesn't have enuff heatsinks , outputs or PSU to sink current into a 2 ohm or lower loads , most Class D are really designed for 8 ohm loads with a low z of 4 ohm being optimum.


    Regards
    * An Audiophile is only as old as his tweeters ..!!

  9. #9
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    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Quote Originally Posted by a.wayne View Post
    Doesn't have enuff heatsinks , outputs or PSU to sink current into a 2 ohm or lower loads , most Class D are really designed for 8 ohm loads with a low z of 4 ohm being optimum.

    Regards
    In your OP you didn't give examples of speakers with "very" low impedance combined with very low efficiency (sensitivity). In practical terms, what portion of widely available consumer speakers meet these criteria?

    I'd say there aren't very many. Meanwhile class D amps like Purifi, Hypex, and ICEpower typically lead with their 4 Ohm rates and are quite capable of driving such loads in normal consumer practice. Some unusual situation might justify fans for better ventilation but such a resort is not emphasized by the makers.

    If you really want to drive very low impedance to high levels and/or with very insensitivity speaker, you ought to look at professional amps by Crown, QSC, et al.; most of these are designed for these circumstances. E.g. the QSC RMX5050A will deliver 2500 wpc into 2 Ohms and will do so all day.

    Of course, these amps don't have much audiophile cachet, but they do the job. (If you want euphonic distortion, you can can put a tube preamp upstream.)
    ~ Bill

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  10. #10
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Speakers which meet such a low efficiency criteria is for a different debate , the focus right now is on amps which do meet the criteria necessary to drive such transducers..!

    BTW i have tried most of those class D amps you listed at low Z they do not meet ( not speculating as you are ) the criteria , well not if Proper Timbre and natural sound is important they will work but mostly thinking where the Bel canto Black or Merrill’s element Class D approach may do the trick , Pricey and may not handle the thermal load , which is pretty much.


    Regards

    PS: Tried both the high powered QSC and Crown, their fans run on High constantly to handle the thermal load and not high fidelity sounding at all ..!
    * An Audiophile is only as old as his tweeters ..!!

  11. #11
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    l

    Quote Originally Posted by a.wayne View Post
    Speakers which meet such a low efficiency criteria is for a different debate , the focus right now is on amps which do meet the criteria necessary to drive such transducers..!

    BTW i have tried most of those class D amps you listed at low Z they do not meet ( not speculating as you are ) the criteria , well not if Proper Timbre and natural sound is important they will work but mostly thinking where the Bel canto Black or Merrill’s element Class D approach may do the trick , Pricey and may not handle the thermal load , which is pretty much.


    Regards

    PS: Tried both the high powered QSC and Crown, their fans run on High constantly to handle the thermal load and not high fidelity sounding at all ..!
    So fair enough. Without specifying speakers that meet the criteria the question is ... uhmm ... academic.

    Then too what's "proper timbre and natural sound" is, in my 50 years of hi-fi listening, highly subjective. A majority of audiophiles prefer euphonic to accurate, but not all.
    Last edited by Feanor; September 2, 2021 at 02:14 PM. Reason: Feanor
    ~ Bill

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  12. #12
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Everything in audio is euphonic and to preference, it’s why so many colorful choices ..




    Regards
    * An Audiophile is only as old as his tweeters ..!!

  13. #13

    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    McIntosh amps with autoformers. 8,4,2 ohms, same full power rating.

    Bench testing reveals obvious, superb performance. McIntosh MC501 monoblock power amplifier Measurements | Stereophile.com

  14. #14
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    You should read that report carefully ..
    * An Audiophile is only as old as his tweeters ..!!

  15. #15

    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by a.wayne View Post
    You should read that report carefully ..
    I did and I owned a pair of MC501’s for years. Thermal stability was never an issue. Bench testing at 1/3 rated power continuous makes many amplifiers heat up. McIntosh shuts down to prevent failure of components under thermal stress which is smart.

  16. #16

    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    This thread will also get shut down soon?

  17. #17

    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Quote Originally Posted by kzhtoo View Post
    This thread will also get shut down soon?
    I don’t know, do you have something to complain about to Mike?

  18. #18

    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Quote Originally Posted by TheOctopus View Post
    I don’t know, do you have something to complain about to Mike?
    Do I have to?

  19. #19

    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Quote Originally Posted by kzhtoo View Post
    Do I have to?
    What is the point of your comments on this thread?

  20. #20
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    W
    Quote Originally Posted by TheOctopus View Post
    I did and I owned a pair of MC501’s for years. Thermal stability was never an issue. Bench testing at 1/3 rated power continuous makes many amplifiers heat up. McIntosh shuts down to prevent failure of components under thermal stress which is smart.
    No they dont , you should stop winging it like this Serge, the 501 heatsinks are woefully inadequate and will have thermal issues on low Sensitivity loudspeakers (can use up to 8 times the avg watts for normal listening) and no the 1/3 power level pre conditioning is very rarely ever failed by competently designed amps with proper SOA parameters ..!

    Yes very rare to see a thermal failure like that and worse in such a short order ..



    Regards

    PS: The 1/3 power preconditioning test became order due to the woefully designed High output SS amps of the time , specifically Phase Linear. The very popular power unit by Bob Carver had a pension for failing into a fireball and was woefully heat sinked and no SOA to talk of..


    * An Audiophile is only as old as his tweeters ..!!

  21. #21

    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by a.wayne View Post
    W

    No they dont , you should stop winging it like this Serge, the 501 heatsinks are woefully inadequate and will have thermal issues on low Sensitivity loudspeakers (can use up to 8 times the avg watts for normal listening) and no the 1/3 power level pre conditioning is very rarely ever failed by competently designed amps with proper SOA parameters ..!

    Yes very rare to see a thermal failure like that and worse in such a short order ..



    Regards

    PS: The 1/3 power preconditioning test became order due to the woefully designed High output SS amps of the time , specifically Phase Linear. The very popular power unit by Bob Carver had a pension for failing into a fireball and was woefully heat sinked and no SOA to talk of..


    Besides my own pair of 501s, I have a friend who also owns a pair and uses them with Sonus Faber Stradivari speakers. I was running my pair with Guarneri Homages which were not overly demanding. Not once did our amps shut down in a decade.

    Then there is at least a few dozen more guys over on that other forum and no one has every had any issues....

    McIntosh amps are legendary in their own right and with over 50 years of history and experience under their belt, the company knows what it is doing when it comes to amps. The Autoformers are there to impedance match the load to the amp section closer and you get the 500w of power whether your speakers are 8, 4 or 2 ohms. Try that with your own amp...

    I don't own 501s anymore, I've had all kinds of gear come and go but I would not hesitate to come back to McIntosh if one day I started getting nostalgic about the amps with big blue meters.

  22. #22
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    D'Agostino S250 - small form factor - will drive anything and looks perty
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  23. #23

    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by XV-1 View Post
    D'Agostino S250 - small form factor - will drive anything and looks perty
    D'Agostino amps will definitely deliver. I also enjoyed the Momentum Monos with 1600w into 2 ohms. Talk about excelling with low impedance. I had them driving the Wilson Alexia and while that speaker did see some dips below 2 ohms if I recall, the amps never broke a sweat or got hot. Of course the price for the pair... well, we know how that goes in audio. Let's just say I paid less for a BMW 540i back in the day.... Nuts.

  24. #24
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Jim, you haven't said what specific speaker you're trying to drive here. If I'm reading between the lines, or taking it to the extreme of your stated requirements, I'd be tempted to think you're working with Apogee Scintillas with their infamous 0.6-1.0 ohm resistance... Back in the day the big Krells were the amp of choice for those. Today I'd be thinking of something like a Pass X600.8.

    Now, I've never tried to drive anything with that low of impedance and low sensitivity in real life - even my Focals don't drop below 2 ohms, and they're reasonably efficient too - so my thoughts here fall firmly in your forbidden "hearsay" category. But the engineering physics suggest that the key for driving really low impedance is 1) hoping you have a mostly stable resistive speaker load rather than inductive/capacitive, 2) plenty of cooling capacity on the amp, and 3) don't want to listen too terribly loud.
    Jeff

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  25. #25
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by TheOctopus View Post
    Besides my own pair of 501s, I have a friend who also owns a pair and uses them with Sonus Faber Stradivari speakers. I was running my pair with Guarneri Homages which were not overly demanding. Not once did our amps shut down in a decade.

    Then there is at least a few dozen more guys over on that other forum and no one has every had any issues....

    McIntosh amps are legendary in their own right and with over 50 years of history and experience under their belt, the company knows what it is doing when it comes to amps. The Autoformers are there to impedance match the load to the amp section closer and you get the 500w of power whether your speakers are 8, 4 or 2 ohms. Try that with your own amp...

    I don't own 501s anymore, I've had all kinds of gear come and go but I would not hesitate to come back to McIntosh if one day I started getting nostalgic about the amps with big blue meters.
    Owned many myself as far back as 1977 , pretty well informed on the brand and i don't doubt your claims on reliability etc , still doesn't cover for the very poor showing as tested by JA ..!

    That was pretty disappointing for such an expensive amplifier ..!


    Regards
    * An Audiophile is only as old as his tweeters ..!!

  26. #26
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Thanks for all of your replies!

    The speakers are a fairly new brand, from outside the USA.

    While my client doesn't want to be involved with pointing out publicly an issue about which he is concerned, and perhaps causing a bad outcome for the new manufacturer, I can say that this is the bass driver in a multi-way high end speaker.

    The driver's impedance is 1.4 ohms.

    He has been thinking of using direct access to only that driver with an appropriate amplifier. The remainder of the sound (maybe 80%) from that speaker is quite nice, it's only problematic with the inefficient/low impedance bass driver in action.
    DPT4ME - Dynamics, Presence & Tone for Musical Engagement; MBP (3) - stripped down for music only; Shunyata Omega & Sigma USBs; ISO REGEN w/short Curious USB links; Berkeley Alpha USB; Aqua La Scala II Optologic DAC; Schiit Yggdrasil - fully updated; Ayre Codex dac - updated; Pass Labs INT-60 integrated amp; Wyred 4 Sound STP-SE-2 preamp, Quicksilver Mono 120 amps w/Tung-Sol KT150s; Quicksilver Mid Mono amps w/Gold Lion KT77s; Fyne Audio 703s; Symposium Svelte Plus & Ultra Platforms; REL S-812 subwoofers; Duelund DCA12GA speaker cables; AV Room Service EVPs, Stein Music Harmonizers, Duelund DCA16GA & 20GA ICs; Shunyata Denali 6000S/V2; Tripp Lite PCs; Wyred 4 Sound power cords; AudioDharma cable cooker; dedicated custom room; various GIK & ASC room treatments; etc.

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  27. #27
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by a.wayne View Post
    Owned many myself as far back as 1977 , pretty well informed on the brand and i don't doubt your claims on reliability etc , still doesn't cover for the very poor showing {of the Mac MC501} as tested by JA ..!

    That was pretty disappointing for such an expensive amplifier ..!
    I don't see where that's coming from: JA's measurements for the MC501 see excellent and he said as much.

    Specifically JA said ...

    "The McIntosh's maximum output power depended on the output tap chosen and the load, but when the tap was matched to the load, the amplifier easily exceeded its specified 500W at our 1% THD definition of clipping. ..."
    Last edited by Feanor; September 3, 2021 at 10:05 AM. Reason: expansion
    ~ Bill

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  28. #28
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by Jim Smith View Post
    Thanks for all of your replies!

    The speakers are a fairly new brand, from outside the USA.

    While my client doesn't want to be involved with pointing out publicly an issue about which he is concerned, and perhaps causing a bad outcome for the new manufacturer, I can say that this is the bass driver in a multi-way high end speaker.

    The driver's impedance is 1.4 ohms.

    He has been thinking of using direct access to only that driver with an appropriate amplifier. The remainder of the sound (maybe 80%) from that speaker is quite nice, it's only problematic with the inefficient/low impedance bass driver in action.
    Since the offending impedance pertains only the bass driver, then I'd wonder and it be driven by a separate amp, (bi-amped). In that case perhaps a "pro" amp could used, (as suggested earlier). A more euphonic amp can be used to the higher frequency drivers.
    ~ Bill

    Win10/Foobar2000 => Topping D90 DAC => Sonic Frontiers Line 1 SE+ preamp => VTV Purifi 1ET400A stereo amp with Sparkos SS3602 op amps => Zaph Audio ZRT speakers (DIY) + PSB Subsonic 5 subwoofer

  29. #29
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by Feanor View Post
    I don't see where that's coming from: JA's measurements for the MC501 see excellent and he said as much.

    Specifically JA said ...

    "The McIntosh's maximum output power depended on the output tap chosen and the load, but when the tap was matched to the load, the amplifier easily exceeded its specified 500W at our 1% THD definition of clipping. ..."
    Read thru again its there and glaring ...! As discussed by both Serge and myself ..



    Regards
    * An Audiophile is only as old as his tweeters ..!!

  30. #30
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by Feanor View Post
    Since the offending impedance pertains only the bass driver, then I'd wonder and it be driven by a separate amp, (bi-amped). In that case perhaps a "pro" amp could used, (as suggested earlier). A more euphonic amp can be used to the higher frequency drivers.
    Euphonic ..!


    So you are suggesting biamping with two class D amps for Proper Euphonics ..!
    * An Audiophile is only as old as his tweeters ..!!

  31. #31
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by Jim Smith View Post
    Thanks for all of your replies!

    The speakers are a fairly new brand, from outside the USA.

    While my client doesn't want to be involved with pointing out publicly an issue about which he is concerned, and perhaps causing a bad outcome for the new manufacturer, I can say that this is the bass driver in a multi-way high end speaker.

    The driver's impedance is 1.4 ohms.

    He has been thinking of using direct access to only that driver with an appropriate amplifier. The remainder of the sound (maybe 80%) from that speaker is quite nice, it's only problematic with the inefficient/low impedance bass driver in action.
    Is his main amps tubes or SS , does he want one amp for everything or active Bi amping..?


    Regards
    * An Audiophile is only as old as his tweeters ..!!

  32. #32
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by Jim Smith View Post

    He has been thinking of using direct access to only that driver with an appropriate amplifier. The remainder of the sound (maybe 80%) from that speaker is quite nice, it's only problematic with the inefficient/low impedance bass driver in action.
    too much of a concept, skip it!
    even in the rare case of a harmonic outcome, it would be very inefficient cashwise.
    again, skip it!!

  33. #33
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by a.wayne View Post
    Read thru again its and glaring ...! As discussed by both Serge and myself ..
    Well yes, sure: the amp shuts down after only 5 minutes at 1/3 power which isn't ideal. As Atkinson says, the heatsinks are small for an amp of that power so maybe that's the reason, (or maybe the temperature sensors are miscalibrated).

    But as Atkinson implies, continuous running with sinewaves isn't going to happen in a home environment, or any environment relevant to audiophile listening. Some applications might need you to run continuously at very high power but that's what "professional" amps are for.

    Ought a $8200+/pair amp to have larger heatsinks? That's a consumer call; McIntosh's judgement that is that their target buyer would rather have somewhat small, lighter amp that is nonetheless able to produce rate power under realistic listening conditions.
    ~ Bill

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  34. #34
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Bill ,,

    SOA and temperature drift ( lack of temp stability) is very important to the sound of an amplifier bias stabilization. This amp will be in full class B mode as it gets hot and this will increase distortion and reduce sonics , not because some don't or cant hear it , doesn't mean it’s not there , some of us do require some class A bias to enjoy our music ..!



    Its this reason for the preconditioning to get the amp up to operating temp then measure , this was not possible with this Mac , so JA was being political and disingenuous with his comments , understandable in todays zeitgeist ..!

    Stereophile 25+yrs ago under Archibald would have canned them on the spot and out the door..


    Regards
    * An Audiophile is only as old as his tweeters ..!!

  35. #35
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by u-sound View Post
    too much of a concept, skip it!
    even in the rare case of a harmonic outcome, it would be very inefficient cashwise.
    again, skip it!!
    So get a boring speaker like most ....
    * An Audiophile is only as old as his tweeters ..!!

  36. #36
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by a.wayne View Post
    Euphonic ..!

    So you are suggesting biamping with two class D amps for Proper Euphonics ..!
    Not at all. My choice might be class D amps, somebody else's might be a Atma-Shere MA-1's

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  37. #37
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Thanks again for all of your replies. It looks to be an exceedingly difficult issue for him to overcome, but at least there have been some interesting suggestions.
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  38. #38

    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by a.wayne View Post
    Read thru again its there and glaring ...! As discussed by both Serge and myself ..



    Regards
    Wasn’t a problem with listening to music then, with the 501 and McIntosh did not address that which is not a problem for real world applications in the future generations.

    Here is a more recent review of a McIntosh stereo amp with auto formers.Read the review and notice how many times the word “superb” comes up…

    “Before doing any testing, I preconditioned the MC462 by running its 8 ohm output at one-third power for 30 minutes into 8 ohms—thermally the worst case for an amplifier with a class-AB or class-B output stage. At the end of that time the heatsinks were very hot, at 158.6°F (70.3°C). I usually precondition amplifiers for an hour, but I was concerned that the MC462 would get even hotter.”

    “McIntosh specifies the MC462 as being able to deliver 450Wpc (26.5dBW) into a load matched to the nominal output Autoformer tap. With clipping defined as being when the THD+noise reaches 1%, fig.6 indicates that the MC462 exceeded its specification even with both channels driven, its 8 ohm output clipping at 516Wpc into 8 ohms (27.1dBW). The trace in this graph stops at 1%, as that is when the amplifier's protection was triggered. Into 4 ohms (fig.7), the McIntosh's 8 ohm output clipped at 720Wpc (25.6dBW). It's fair to note that I don't hold the wall voltage constant for this test; with both channels clipping into 4 ohms, the wall voltage had dropped from 121 to 115.4V. The MC462's 2 ohm output delivered 190Wpc (22.8dBW) with both channels driven into 8 ohms at 1% THD+N, 298Wpc with both channels driven into 4 ohms (21.7dBW, fig.8), and 536W (21.3dBW) with one channel driven into 2 ohms (fig.9).”


    Summing up the McIntosh MC462's measured performance is easy: It is an extraordinarily well-engineered, exceptionally powerful amplifier.—John Atkinson




    McIntosh Laboratory MC462 power amplifier Measurements | Stereophile.com

  39. #39
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Serge you don't even pretend to understand or care , hahaha ..


    Im now beginning to understand how such a stalwart company is laughed upon in the modern hi-end era and considered junk by many..



    Regards
    * An Audiophile is only as old as his tweeters ..!!

  40. #40
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by Jim Smith View Post
    Thanks again for all of your replies. It looks to be an exceedingly difficult issue for him to overcome, but at least there have been some interesting suggestions.
    I don't think its remotely difficult Jim , but you already know that ..
    * An Audiophile is only as old as his tweeters ..!!

  41. #41

    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by a.wayne View Post
    Serge you don't even pretend to understand or care , hahaha ..


    Im now beginning to understand how such a stalwart company is laughed upon in the modern hi-end era and considered junk by many..



    Regards
    Over the decades of reading Stereophile, I've seen plenty of comments of cooking and blazing hot amps that were too hot to touch, etc.. etc. while being bench tested/tortured. What's there to not understand? Music is not a continuous sinewave at 1/3 rated power....

    Music flows, it has ebbs, quiet passages, music had my MC501s, D'Agostino Momentums, ARC, amps that actually offered a "visual" reference to what is going on with the power output, they were all cruising at fractional power output. Mostly somewhere in the 3-40w range with peaks of perhaps 100w when really rocking out on occasion. I don't listen to music at simulated rock concert levels... Never have.

    So McIntosh has both thermal and clipping protection. No fried tweeters, no melted transistors that were outside the SOA. It is true that McIntosh operates at class A for the first few watts and sounds great doing it but no amount of heat sinks would keep it within that range if the loud knob is cranked over on the preamp... It leaves class A and will keep on huffing and puffing, delivering, typically way more than the advertised power with the autoformer. What's there not to understand? The thermal circuit is there to protect your investment from your own stupidity.

    Don't like McIntosh? Fine, that's your personal bias. I see nothing wrong with the design that has never let me down personally and everyone else I know that owns McIntosh amps.

  42. #42
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    * An Audiophile is only as old as his tweeters ..!!

  43. #43

    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    This is how most folks listen in real world applications... Long way to go to clipping and thermal protection circuits activating LOL...


  44. #44

    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Then there are the MC1.25KWs for the bigger scale/room/speaker applications.


  45. #45
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Burmester 909 mk5! Or 911mk3 mono. But 909 mk5 better for that load

  46. #46
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Anthem P2 stable down to short circuit 0 ohms

  47. #47
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    Re: Power amplifiers that excel with VERY low impedance - and low efficiency - loads

    Quote Originally Posted by Jim Smith View Post
    Looking for recommendations for a client.

    Please - submissions not from hearsay, but from actual user experience - Thanks!
    Jim - I bought a pair of low efficient, low impedence Martin Logan electrostatic 13A speakers a couple of years ago, but after using Avantgarde for 15 years, I had no suitable amplifier. Looking at sources such as Martin Logan Owners forum, I went for the Sanders Magtech amplifier. Sanders build electrostatic speakers and found a dearth of suitable amps, so he designed his own with those particular features. It was a good amp for this type of speaker, but sadly the speakers never sounded good in my difficult room. Both the ML and Sanders were sold and I'm back with Avantgarde. My GamuT D200 also did well with the MLs. Peter
    Sources - NAD M50.2 (streamer, CD player, CD ripper, hard drive music store)
    Amplification - NAD M33, NAD M12, Consonance Cyber 845 monoblocs (now sold)
    Speakers - Avantgarde Duo XD, Avantgarde Duo (2006) - both aesthetically modified, Martin Logan Expression 13A (now sold)

  48. #48
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    I heard the Sanders amps were built by either ATI or Coda, I can't remember which. I personally wouldn't use Coda for a bass amp but ATI are beasts. I'm sure Sanders were built to their spec though. The Coda use no feedback, they are high current but don't have the definition I like in the low end. I wish I had more time with the ATI in my system, I have never heard an amp with that much low end power at any price. A friend brought his over for a quick listen back when I had Revel F52's.
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  49. #49
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Quote Originally Posted by Mr Peabody View Post
    I heard the Sanders amps were built by either ATI or Coda, I can't remember which. I personally wouldn't use Coda for a bass amp but ATI are beasts. I'm sure Sanders were built to their spec though. The Coda use no feedback, they are high current but don't have the definition I like in the low end. I wish I had more time with the ATI in my system, I have never heard an amp with that much low end power at any price. A friend brought his over for a quick listen back when I had Revel F52's.
    Sanders amps are built by CODA but are OEM to Sanders design, not the same as any Coda model. ATI also builds OEM amps for several other companies.

  50. #50
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    Re: Power amplifiers that excel with very low impedance - and low efficiency loads

    Like I stated earlier you should try the Anthem P2 power amp 325WPC @8ohms,500WPC @4ohms,675WPC @2ohms, and stable all the way down to 0 ohm impedance.
    Just go to the Anthem website and under products go to P2 power amps

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Power amplifiers that excel with very low impedance - and low efficiency loads

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