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Hi,

 

I am slowly gathering bits and pieces for my Martin Logan HT build.

 

I have a Sanders ESL to power the fronts, 2x Parasound Halo A23 to power the surrounds, but nothing yet to power the center speaker.

The center speaker is a ML Stage X 70-22000Hz, max impedance drop to 4ohm. I am searching for another amp that matches the design quality as the Parasound and Sanders.

Either a mono or stereo/mono with a reasonable price tag used or new. Still chasing and searching for another used A23 but wouldn't mind to hear other options.

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The most important part of a HT setup is the centre channel, you have a very good speaker for this, so you need an amp to suit, it maybe a bit over the top, but there are used single monobock Parasound JC1's that come up now and again, it also has a high bias Class A switch on the back an this would do nicely for centre channel use, and would drive that hard load no problems the Stage represents.

 

Cheers George

 

 

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12 hours ago, Primare Knob said:

Hi,

 

I am slowly gathering bits and pieces for my Martin Logan HT build.

 

I have a Sanders ESL to power the fronts, 2x Parasound Halo A23 to power the surrounds, but nothing yet to power the center speaker.

The center speaker is a ML Stage X 70-22000Hz, max impedance drop to 4ohm. I am searching for another amp that matches the design quality as the Parasound and Sanders.

Either a mono or stereo/mono with a reasonable price tag used or new. Still chasing and searching for another used A23 but wouldn't mind to hear other options.

I have a single Ayre MX-R mono which will do the job nicely......very little use ....was hoping to use it with my Dynaudio Evidence  center in a HT setup but circumstances have changed . PM me if interested.

Edited by Jones99

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That would do him nicely. Uses bi-polar outputs which can give current to that power hungry ML esl centre speaker.

 

Charles Hansen (Ayre)  

"The first is that, in parts of the circuit, bipolar devices sound better than FETs, so that's what we used."
tested
360w -8ohm
640w-4ohm
775w-2ohm would have gone much further, but protection circuit cut in.
 
These tests show this amp can do current.   

 

 

Cheers George

Edited by georgehifi

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2 hours ago, georgehifi said:

The most important part of a HT setup is the centre channel, you have a very good speaker for this, so you need an amp to suit, it maybe a bit over the top, but there are used single monobock Parasound JC1's that come up now and again, it also has a high bias Class A switch on the back an this would do nicely for centre channel use, and would drive that hard load no problems the Stage represents.

 

Cheers George

 

 

JC1 for a center speaker, wow just wow. 

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2 hours ago, georgehifi said:

That would do him nicely. Uses bi-polar outputs which can give current to that power hungry ML esl centre speaker.

 

Charles Hansen (Ayre)  

"The first is that, in parts of the circuit, bipolar devices sound better than FETs, so that's what we used."
tested
360w -8ohm
640w-4ohm
775w-2ohm would have gone much further, but protection circuit cut in.
 
These tests show this amp can do current.   

 

 

Cheers George

Probably won't do well for my wallet.

 

One of the questions at hand is how difficult a load the Stage-X is going to be. I cannot really find much info on it. The ESL panel is only used in the frequency range from 450 -2700 Hz. Above the 2700Hz a transducer tweeter is taking over with an amp friendly impedance of 4 ohm.

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As you can see in the Stage Impedance v negative phase angle graph, they dip to 2.5ohms at 150hz, 800hz and 3.5khz. This is very hard, but that's not the real nasty ones, as the negative phase angle is above -40 degrees.

Where they get really tough is at 100hz @ 4ohms where the -phase angle is also -60 degrees as well, this can seem like 1-2ohms to the amp as this is what called the combined (edpr) equivalent peak dissipation resistance.

martin-logan-stage-x-speaker-impedance-p

All this means you want a monoblock that can do very good current.

 

Cheers George  

Edited by georgehifi

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1 minute ago, georgehifi said:

As you can see in the Stage Impedance v negative phase angle graph, they dip to 2.5ohms at 150hz, 800hz and 3.5khz. This is very hard, but that's not the real nasty ones, as the negative phase angle is above -40 degrees.

Where they get really tough is at 100hz @ 4ohms where the -phase angle is also -60 degrees as well, this can seem like 1-2ohms to the amp as this is what called the combined (edpr) equivalent peak dissipation resistance.

martin-logan-stage-x-speaker-impedance-p

Cheers George  

 

OUCH! You know what I am going to suggest, so I won't.

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I'll do it for you so you don't get zap'ed

If Zaphod has a rare ME monoblock this would also do as they do current as well.

 

Cheers George

Edited by georgehifi

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I just found that particular review as well and was on my way to post it.

 

Seems like I need to take more into consideration than ML wants me to believe. Thanks.

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Just want to add, do not get rid of that speaker because it's hard to drive, as it's probably the best centre channel speaker you can get. And the center channel speaker is the most important speaker in a HT setup.

 

Cheers George

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With the new price of the Ayre, and being all the way up in Asia and the JC's most likely will only sell in pairs on the second hand market what would I be looking into as a more down to earth alternatives.

 

How would an A23 or A21 do in a mono configuration? Or what other (bridged) stereo amps can be considered to give me more options than trying to chase down a single mono block on the second hand market?

 

Edit.

I am just reading through the manual of the A21, and it states not to connect a speaker with a lower impedance than 8Ohm in ridged mode. Is bridged mode something that I should not consider?

Edited by Primare Knob
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Google "disadvantages of bridging amplifiers" there much to read.

Damping factor takes a hit, distortion goes up, as you found the ability to drive low impedance diminishes ect ect. 

 

Cheers George

.  

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16 minutes ago, georgehifi said:

Google "disadvantages of bridging amplifiers" there much to read.

Damping factor takes a hit, distortion goeIs up, as you found the ability to drive low impedance diminishes ect ect. 

 

Cheers George

.  

I was under the illusion that in bridging the low impedance stability would increase.

 

I'll mention the obvious ones. Let's say you have 8 ohm speakers and 2 x 250w power into 4 ohms or 2 x 160w into 8. You bridge the amp so you then get (probably) 500w into a single 8 ohm load. If your amp is 4 ohm stable, it now sees effectively a 4 ohm load into both of those channels. If your speakers were 4 ohm then the amp would see a 2 ohm effective load and be potentially unstable.

So you get twice the power that is rated into half the impedance. The minimum impedance driven goes up by a factor of 2.

You get extra power, but also limit the impedance it can drive.

By Paul Spencer

Edited by Primare Knob

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No damping factor of the amp goes down and output impedance is higher.

That's why Parasound said to you if you bridge their amp, not to load it down with less than 8ohms

 

Cheers George

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2 minutes ago, Primare Knob said:

I was under the illusion that in bridging the low impedance stability would increase.

 

Nope. George is correct. When you bridge an amp, you are effectively connecting both output stages in SERIES (you should NEVER connect them in parallel, unless the circumstances are very special), thus doubling the available output Voltage. Because there is double the output Voltage available, then the theoretical maximum power output is 4 times a single channel one. This means that the bridged output stage 'sees' half the impedance that it is connected to it. IOW:

 

If the load impedance is 8 Ohms, the bridged output stage 'sees' that load as 4 Ohms.

If the load impedance is 4 Ohms, the bridged output stage 'sees' that load as 2 Ohms.

And so on. 

 

 

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If you definitely want a mono-block for your center with punch and quality, and not to break the bank, go for an Anthem Statement M1.

They retail close to 4K each but Eastwood HIFI in Sydney have them in special for 2.5K.

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7 minutes ago, ufo said:

If you definitely want a mono-block for your center with punch and quality, and not to break the bank, go for an Anthem Statement M1.

They retail close to 4K each but Eastwood HIFI in Sydney have them in special for 2.5K.

 

That is a class D amp. They often struggle with loads at 2ohm and lower. It has been recommended to not use them with electrostatic speakers.

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Just now, Primare Knob said:

 

That is a class D amp. They often struggle with loads at 2ohm and lower. It has been recommended to not use them with electrostatic speakers.

 

Correct. Not a good choice for ESLs.

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Quote

As you can see in the Stage Impedance v negative phase angle graph, they dip to 2.5ohms at 150hz, 800hz and 3.5khz. This is very hard, but that's not the real nasty ones, as the negative phase angle is above -40 degrees.

Where they get really tough is at 100hz @ 4ohms where the -phase angle is also -60 degrees as well, this can seem like 1-2ohms to the amp as this is what called the combined (edpr) equivalent peak dissipation resistance.

 

If you want the very best from this speaker.

This sort of load is not for "Class D" which the Anthem is, or for tube or Mosfet output.

 

Cheers George

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Looking into specs and stability in 2ohm or less loads, you often see a double of wattage from 8ohm to 4ohm, but not very often from 4 to 2 ohm. Guessing here that this has to do with the max output of the transistors. Does the output of the trafo come more into play here to determine if it is stable enough to drive loads less than 4ohm?

 

What should I keep in mind when driving the Stage-X?

The difficult loads at 100Hz and 150Hz are with the conventional cone speakers driven.

The difficult load at 800Hz is with the ESL panel driven

The difficult load at 3.5kHz is with the transducer tweeter driven.

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8 minutes ago, georgehifi said:

 

If you want the very best from this speaker.

This sort of load is not for "Class D" which the Anthem is, or for tube or Mosfet output.

 

Cheers George

That would rule out the Parasounds as well, would it not. (Probably a whole lot of others to)

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8 minutes ago, Primare Knob said:

Looking into specs and stability in 2ohm or less loads, you often see a double of wattage from 8ohm to 4ohm, but not very often from 4 to 2 ohm. Guessing here that this has to do with the max output of the transistors. Does the output of the trafo come more into play here to determine if it is stable enough to drive loads less than 4ohm?

 

What should I keep in mind when driving the Stage-X?

The difficult loads at 100Hz and 150Hz are with the conventional cone speakers driven.

The difficult load at 800Hz is with the ESL panel driven

The difficult load at 3.5kHz is with the transducer tweeter driven.

 

First off:

 

NO amplifier can double it's output into successively lower impedances. It is an impossibility in our universe. The reason is due to saturation Voltages in output devices (MUCH higher in MOSFETs than in BJTs), power supply losses, etc.  Below are the specs on an amplifier, which employs one of the largest power supplies ever fitted to a commercially available amplifier. The amplifier also employs very high current limit figures (100 Amps). Note that power outputs do not double, as load impedance halves. 

 

In VERY general terms, the power transformer and capacitance figures (along with current limit points in the ouput stages) dominate how an amplifier copes with low impedance, low frequency loads. At mid frequencies, the power transformer becomes less important and capacitance (speed AND amount) and current limit points dominate. At HF, capacitance amount becomes less important, whilst capacitance placed VERY close to the output devices assumes greater importance, along with current limit points. 

ME_1500_data_2.jpg

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11 minutes ago, Zaphod Beeblebrox said:

 

First off:

 

NO amplifier can double it's output into successively lower impedances. It is an impossibility in our universe. The reason is due to saturation Voltages in output devices (MUCH higher in MOSFETs than in BJTs), power supply losses, etc.  Below are the specs on an amplifier, which employs one of the largest power supplies ever fitted to a commercially available amplifier. The amplifier also employs very high current limit figures (100 Amps). Note that power outputs do not double, as load impedance halves. 

 

In VERY general terms, the power transformer and capacitance figures (along with current limit points in the ouput stages) dominate how an amplifier copes with low impedance, low frequency loads. At mid frequencies, the power transformer becomes less important and capacitance (speed AND amount) and current limit points dominate. At HF, capacitance amount becomes less important, whilst capacitance placed VERY close to the output devices assumes greater importance, along with current limit points. 

ME_1500_data_2.jpg

 

This amp has been rumoured to cure cancer!  *drool*

Edited by Jakeyb77

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