Amps stable down to 1ohm or below...

[Mike]

For difficult impedance dip speakers like Martin Logan and some other electrostatic speakers, what are some amps that are stable down to 1ohm (or below)?

I would assume amps with a Bipolar output stage are going to have the edge over MOSFET/JFET output stages.

I’m guessing a few are:

* Gryphon
* Luxman
* Accuphase
* Soulution
* CH
* Bryston
* D’Ag
* SimAudio??

Any others come to mind?

Class D and Tube amps need not apply?

[Dizzie]

Possibly the Sanders Sound Systems ESL and Magtech amps? Designed for, but not limited to, electrostatic speakers.

http://www.sanderssoundsystems.com/p...k-ii-amplifier

http://www.sanderssoundsystems.com/p...rs/magtech-amp

[Mike]

Possibly the Sanders Sound Systems ESL and Magtech amps? Designed for, but not limited to, electrostatic speakers.

http://www.sanderssoundsystems.com/p...k-ii-amplifier

http://www.sanderssoundsystems.com/p...rs/magtech-amp

Thanks. I forgot about those.

[Jack]

Coda as they appear to be the OEM for Sanders.

[Mike]

Coda as they appear to be the OEM for Sanders.

Interesting. Thanks.

[Oly]

Does Pass belong in that group?

[Mike]

Does Pass belong in that group?

I don’t believe so.


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[bart]

Hegel?

[Alpinist]

I don’t believe so.


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I think they might.

Ken

[Mike]

Hegel?

Definitely!

[Dizzie]

Coda as they appear to be the OEM for Sanders.

Coda is not the OEM for Sanders. Roger told me they manufacture their own amplifiers. From the website:

"Speakers and Electronics are manufactured in Conifer, Colorado."

[audio.bill]

Coda does act as an OEM designer and/or manufacturer for several brands of high end electronics. The products they design for other brands are often customized in specific ways and differ from Coda branded products in order to best meet the needs of the other company. If you look at the design and construction of Coda amps and preamps and compare them to those from Sanders and Legacy for example there are many obvious similarities which are beyond coincidental. So Sanders claim to manufacture their own amps may indeed be true, but their design is apparently at some level associated with Coda. It's possible that Coda could be hired as a design consultant by Sanders for their amplifiers and that would still allow them to be manufactured by Sanders in Colorado.

[kiwi_1282001]

Coda does act as an OEM designer and/or manufacturer for several brands of high end electronics. The products they design for other brands are often customized in specific ways and differ from Coda branded products in order to best meet the needs of the other company. If you look at the design and construction of Coda amps and preamps and compare them to those from Sanders and Legacy for example there are many obvious similarities which are beyond coincidental. So Sanders claim to manufacture their own amps may indeed be true, but their design is apparently at some level associated with Coda. It's possible that Coda could be hired as a design consultant by Sanders for their amplifiers and that would still allow them to be manufactured by Sanders in Colorado.

+1. I also believe this.

For its part, Sanders modifies the Coda design to suit its philosophy and goals - the fully regulated PSU being one example.

[audio.bill]

+1. I also believe this.

For its part, Sanders modifies the Coda design to suit its philosophy and goals - the fully regulated PSU being one example.

Absolutely, there are unique and brand specific changes made to the designs Coda assists with. I didn't mean to imply that any of the other branded amps were identical and simply re-branded Coda amps.

[GSOphile]

Coda makes excellent products at relative bargain prices. Principals worked with Nelson Pass at Threshold back in the day. My understanding is that they sell more overseas than here in the U.S. and that they like to develop and build more than market.

[Mike]

Ok, OTHER than Coda?

Luxman is looking like a good option.


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[Anatta]

Pass XA series
the large Chords
the large Vitus
Boulder

[Mr Peabody]

I would have thought Pass since he began building amps with the intent to drive his own speaker.

I don't know about Krell of today but definitely Krell of the earlier. I knew of a guy who used them to drive Apogees.

What about ATI. Those amps are beasts, even requiring two power cords with 20 amp ends.

I know tubes typically need not apply but the guy with the Apogees went to some tube amp called NAT he said drove them, anyone know of them?

[Kuoppis]

NAT is a manufacturer from Serbia.

They are well lauded for tube amps, e.g. the NAT Symmetrical preamp an the NAT Transmitter power amp.


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[matt_zak]

A couple more for your list: Electrocompaniet & Lamm (Hybrid)

[tube-vds]

fm acoustics 115:

operating with music or continuous toneburst:
550 Wpeak into 8 Ohm
1000 Wpeak into 4 Ohm
1800 Wpeak into 2 Ohm

275 WRMS into 8 Ohm
500 WRMS into 4 Ohm
900 WRMS into 2 Ohm

Max. Output Current:
Unlimited repetitive peak output current. More than 35 A continuous. No output or DC fuses, absolutely no form of current-, voltage- or any other kind of limiting.

Load Impedance:
No minimum impedance.
The amplifier is designed for 1 Ohm to 10’000 Ohm systems.
It can drive any speaker impedance (even below 1 Ohm) with dynamic (music) signals without any limiting, compression or other negative effects on the audio signal.
Despite this, the amplifier is fully protected against short circuits, open circuits and all other adverse conditions via unique onboard circuitry that continuously surveys all important parameters.

https://www.audiolimits.com/Helix-tu...acoustics.html

[Skanda]

symphonic line kraft and for a taste of greatness at budget amp pricing: odyssey audio amps. though klaus has been taking them a bit of a different direction than their symphonic line big brothers, he is very upfront about his amps being quality but the SL being _that_ much better

[kiwi_1282001]

There are some less known - or a least talked about - products which are likely to perform into low impedance loads. Two examples are:

1. Karan Acoustics power amplifiers, for example the KA M 900 and KA S 600
2. Plinius Audio, for example the Reference A-300

[W9TR]

Any of the McIntosh autoformer amps will be stable into really low impedance complex loads. It's not just less than 1 ohm, its also the fact that some of these speakers present highly reactive loads. Electrostats are almost entirely capacitive at high frequencies.

I would really like to see what a 1 kHz or 10 kHz squarewave looks like when any of these amplifiers drive a capacitive load < 1 ohm. That will separate the posers from the real deal.

Tom

[Mike]

Any of the McIntosh autoformer amps will be stable into really low impedance complex loads. It's not just less than 1 ohm, its also the fact that some of these speakers present highly reactive loads. Electrostats are almost entirely capacitive at high frequencies.

I would really like to see what a 1 kHz or 10 kHz squarewave looks like when any of these amplifiers drive a capacitive load < 1 ohm. That will separate the posers from the real deal.

Tom

I’m not sure the Mc amps are stable down to 1ohm. 2ohm, yes.


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[W9TR]

On the 2 ohm tap modern McIntosh amps are stable to way less than 1 ohm. The autoformers help isolate difficult loads and present a reasonable load line to the amplifier circuitry.

When I was looking at electrostats, I tested my MC 602 into a 0.5 ohm resistive load and also a 10 uF film cap with 10 kHz square waves at 100 Watts. No overshoot or ringing on the 0.5 ohm load and some minor ringing into the 10 uF cap. Superb stability.

Tom

[knghifi]

Audio Flight #4 and #8? Myles Astor reviewed #4 several years ago.

In market for SS amp so visiting local Audia Flight dealer next week. Should be fun!

[atmasphere]

fm acoustics 115:

operating with music or continuous toneburst:
550 Wpeak into 8 Ohm
1000 Wpeak into 4 Ohm
1800 Wpeak into 2 Ohm

275 WRMS into 8 Ohm
500 WRMS into 4 Ohm
900 WRMS into 2 Ohm

Max. Output Current:
Unlimited repetitive peak output current. More than 35 A continuous. No output or DC fuses, absolutely no form of current-, voltage- or any other kind of limiting.

Load Impedance:
No minimum impedance.
The amplifier is designed for 1 Ohm to 10’000 Ohm systems.
It can drive any speaker impedance (even below 1 Ohm) with dynamic (music) signals without any limiting, compression or other negative effects on the audio signal.
Despite this, the amplifier is fully protected against short circuits, open circuits and all other adverse conditions via unique onboard circuitry that continuously surveys all important parameters.

https://www.audiolimits.com/Helix-tu...acoustics.html

Obviously this is some kind of marketing. The math doesn't work out, unless this amp is more powerful than advertised. If it really can support 35amps then it can make 2450 watts into 2 ohms but we see from the above specs it does not. So I suspect the 35 amp figure is really what happens for 10mS when the power supply is shorted and does not represent the actual current present in the output section. math: Power=current(squared) x resistance. so 2450 = 35(squared) x 2. By that measure we make an OTL that does 50 amps...

And of course it will limit current when its abilities are exceeded. It also has a minimum impedance, else the short protection for the amplifier would not function.

*****************

There is the question of what is meant by 'stability'. Normally that means the amp won't oscillate. So I don't think the term 'stable' is being used correctly in this thread. Further, the speaker in question has a 1 ohm impedance above 15KHz being an electrostatic. Its impedance will be higher at frequencies less than 15KHz. Because there is so little energy at this frequency, far more amplifiers will work with this speaker than are listed in this thread- including many tube amps that don't have taps below 4 ohms!

Many of the better-built Japanese receivers made in the late 1970s will work fine (IOW no oscillation) on this speaker. Seriously the power that the amp makes is likely the bigger issue- how much power does the amp need to fill the room? That is less clear but IIRC Sanders made some pretty big amps. Any 100 solid state amp made today will otherwise work fine. The ability to double power as impedance is cut in half is not required here either- again, the energy at 15KHz and above is slight. In addition, there is the question of whether that is a desirable trait, since ESLs generally speaking have an impedance curve based on a capacitor rather than a speaker in a box. On that account, the impedance curve of an ESL is not also a map of its efficiency like it is with most box speakers. Many ESLs work better if the amp can make the same power in to 4 ohms as it does into 8; otherwise what can happen is the amp will be too bright on top!

[Colekat]

Emm MTRX mono blocks ... stable under 1ohm and sound great !

[johndoe21ro]

Balanced Audio Technology should do the trick! At least the big solid state amps...

[Audioseduction]

YES! Pass Labs does belong in the group. Top 3 I say from many years of listening and owning both Pass Labs and Martin Logans for years. My XA160.5 never runs out of steam no matter how loud I play them!

[Mike]

YES! Pass Labs does belong in the group. Top 3 I say from many years of listening and owning both Pass Labs and Martin Logans for years. My XA160.5 never runs out of steam no matter how loud I play them!

Pass amps are awesome, but I’ve talked to them and they are stable down to the rated wattage (4 ohms).

[Audioseduction]

Pass amps are awesome, but I’ve talked to them and they are stable down to the rated wattage (4 ohms).

Never experience any issues at all over the years. In fact many Martin Logan owners own Pass Labs amps to accommodate their Speakers.

[audio.bill]

Never experience any issues at all over the years. In fact many Martin Logan owners own Pass Labs amps to accommodate their Speakers.

Martin Logans only exhibit an impedance of 1 ohm over a relatively narrow bandwidth, so they don't present an overall load anywhere near that low to the power amp. Their nominal impedance rating is more realistic in evaluating the load they present to an amp instead of just focusing on the lowest point of their impedance curve.

[atmasphere]

Heck, most tube amps of 100 watts or more can do the job assisted by a set of ZEROs (www.zeroimpedance.com). That's what we suggest when someone wants to use our amps on Martin Logans.

[a.wayne]

For difficult impedance dip speakers like Martin Logan and some other electrostatic speakers, what are some amps that are stable down to 1ohm (or below)?

I would assume amps with a Bipolar output stage are going to have the edge over MOSFET/JFET output stages.

I’m guessing a few are:

* Gryphon
* Luxman
* Accuphase
* Soulution
* CH
* Bryston
* D’Ag
* SimAudio??

Any others come to mind?

Class D and Tube amps need not apply?

Takes alot of heatsink to handle 1 ohm loads , you can drop the small heatsink ones to begin with, Gryphon for sure can ....

[a.wayne]

Possibly the Sanders Sound Systems ESL and Magtech amps? Designed for, but not limited to, electrostatic speakers.

http://www.sanderssoundsystems.com/p...k-ii-amplifier

http://www.sanderssoundsystems.com/p...rs/magtech-amp

Not enuff heatsink area or PSU

[a.wayne]

Does Pass belong in that group?

Historically NP amps will handle 1 ohm as they are way over built on output stage and heat sink area, they are PSU limited thou ....

[a.wayne]

+1. I also believe this.

For its part, Sanders modifies the Coda design to suit its philosophy and goals - the fully regulated PSU being one example.

Sanders magtech amplifiers are way too small to have a "fully" regulated PSU ......

[a.wayne]

fm acoustics 115:

operating with music or continuous toneburst:
550 Wpeak into 8 Ohm
1000 Wpeak into 4 Ohm
1800 Wpeak into 2 Ohm

275 WRMS into 8 Ohm
500 WRMS into 4 Ohm
900 WRMS into 2 Ohm

Max. Output Current:
Unlimited repetitive peak output current. More than 35 A continuous. No output or DC fuses, absolutely no form of current-, voltage- or any other kind of limiting.

Load Impedance:
No minimum impedance.
The amplifier is designed for 1 Ohm to 10’000 Ohm systems.
It can drive any speaker impedance (even below 1 Ohm) with dynamic (music) signals without any limiting, compression or other negative effects on the audio signal.
Despite this, the amplifier is fully protected against short circuits, open circuits and all other adverse conditions via unique onboard circuitry that continuously surveys all important parameters.

https://www.audiolimits.com/Helix-tu...acoustics.html

Manny Huber amps are not 1 ohm rated TMK ....

[a.wayne]

symphonic line kraft and for a taste of greatness at budget amp pricing: odyssey audio amps. though klaus has been taking them a bit of a different direction than their symphonic line big brothers, he is very upfront about his amps being quality but the SL being _that_ much better

Again both way too small for a 1 ohm load ...........

[a.wayne]

Any of the McIntosh autoformer amps will be stable into really low impedance complex loads. It's not just less than 1 ohm, its also the fact that some of these speakers present highly reactive loads. Electrostats are almost entirely capacitive at high frequencies.

I would really like to see what a 1 kHz or 10 kHz squarewave looks like when any of these amplifiers drive a capacitive load < 1 ohm. That will separate the posers from the real deal.

Tom

Agree,

Mcintosh been making amps to drive 1 ohm load from the 60's , fan cooling was a necessity too ...

[a.wayne]

Balanced Audio Technology should do the trick! At least the big solid state amps...

4 Ohm only , weak amplifiers IMO.....

[a.wayne]

Pass amps are awesome, but I’ve talked to them and they are stable down to the rated wattage (4 ohms).

Nelson has always taken this approach , even from his threshold days. Big thresholds will drive 1 ohm loads on music content all day , will require a fuse change, same for the big Pass amps .....


Regards

[a.wayne]

Never experience any issues at all over the years. In fact many Martin Logan owners own Pass Labs amps to accommodate their Speakers.

I dont recall Martin logan making a 1 ohm load speaker ....



regards

[audio.bill]

Sanders magtech amplifiers are way too small to have a "fully" regulated PSU ......

Here is their claim taken directly from their website:

Sanders has solved these problems by developing a voltage regulator that is essentially 100% efficient. There is no heat dissipated by the regulator system. There is no high-power/high-voltage switching that causes heat generation or RF problems.
The regulator in the Magtech amplifier maintains a stable voltage regardless of load or reasonable changes in the line voltage feeding the amplifier. It runs stone cold, produces zero RF energy, and is simple and reliable.
Unlike other amplifiers, the distortion in the Magtech amplifier is virtually unchanged regardless of power level. The bias is stable regardless of load.

[audio.bill]

I dont recall Martin logan making a 1 ohm load speaker ....
regards

Not a nominal 1 ohm load, but some ML models present a 1 ohm load across a limited bandwidth in the high frequencies.

[Mike]

I wasn’t speaking about ML.


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[a.wayne]

Here is their claim taken directly from their website:

Sanders has solved these problems by developing a voltage regulator that is essentially 100% efficient. There is no heat dissipated by the regulator system. There is no high-power/high-voltage switching that causes heat generation or RF problems.
The regulator in the Magtech amplifier maintains a stable voltage regardless of load or reasonable changes in the line voltage feeding the amplifier. It runs stone cold, produces zero RF energy, and is simple and reliable.
Unlike other amplifiers, the distortion in the Magtech amplifier is virtually unchanged regardless of power level. The bias is stable regardless of load.

Yes i have seen that before , its a good amp at 4 ohm on maggies, its not a 1 ohm load amp for sure.

As to the web site claims, i haven't seen any bench testing to confirm , maybe he is running quantum nanotech technology beyond the norm ..




Sanders uses like NP, a very large output stage , 10pr's i think so it will drive a 1 ohm load but sinks are pretty small for any continuous usage at that load ..


Regards

[a.wayne]

Not a nominal 1 ohm load, but some ML models present a 1 ohm load across a limited bandwidth in the high frequencies.

Yes, correct, demand is very small , stability is whats important here due to phase angles ..