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Benchmark AHB2 Max Output into 4Ω


Langston
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@Deang Asked about measurements of this amp beyond the standard 1kHz. I was kind of surprised myself when I noticed that wasn't easy to come by, thus a few measurements of my unit that's a few years old and working perfectly. This is also for the crazy Frenchman that goes by @mustang_flht, has a picture of a Mustang for his avatar YET has a German sports car! : )

 

I only have two 4Ω power resistors (4Ω is my life), so I couldn't do two channel 8Ω measurements.

 

10Hz - 20kHz THD

1298947729_AHB2THD.thumb.png.d1bd3b0403b45169409ee23455790b94.png

 

SMPTE IMD

259586884_AHB2SMPTE.thumb.png.ca1bc270a31a1b4606d13d269907bd7a.png

 

Single Tone Max Outputs at 1% THD (into 4Ω)

1351954886_20HzMaxinto4Ohms.png.48710aec3eef21ff76439a65e0d2d6db.png

 

56399030_50HzMaxinto4Ohms.png.5ac65a20a8e2cb540afa608b81c9ae4b.png

 

2039402089_1kHzMaxinto4Ohms.png.4b4ffaddf07f9c4b51e0821d779a452d.png

 

1482251241_5kHzMaxinto4Ohms.png.49d720b49443af4e268fd50c3936f98b.png

 

God bless you and your precious family - Langston

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Posted (edited)

BTW, when measuring amps always measure directly from the amp terminals, not at he end of the cables that connect to the load. If you do the latter, you'll form a voltage divider (attenuator) made up of the amp's output impedance and the impedance of the cables. Not good when your goal is to characterize the amp.

 

1030670995_AHB2Measure.thumb.jpg.d83a418673ce12dcb094343bb2a0d39b.jpg

 

God bless you and your precious family - Langston

Edited by Langston
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Posted (edited)
On 6/13/2021 at 10:52 AM, Godataloss said:

Could you share your system and some listening impressions and comparisons to some other amps you've tried? 

 

I'm hesitant about subjective impressions of stuff because humans are all over the map on this kind of thing depending on background and disposition. On the latter I'm all about Galileo's scientific method - but I also fell in love with Dave Brubeck's Take Five album when my Dad played the record on our living room entertainment system in 1963 when I was four. It stunned me and though my career was mostly in finance, science and teaching - Brubeck haunted me.

 

So just after the year 2k I decided that I had enough loot to do something stupid, so I started a concert production company from scratch with the goal to provide the highest possible sound quality even if I lost money in the process. Unfortunately it succeeded and I kept at it until a couple of years ago. I'd achieved what I wanted - a clientele that would pay for my very best effort. The icing on the cake was the oldest and most talented of Dave Brubeck's kids, Chris, used me when he did stuff in the area I covered. Yes I'm bragging. Chris writes symphonies that are usually thematic, such as an Ansel Adams piece with full orchestra and a huge screen fading in and out of different pictures of that amazing black and white photographer while the music did interpretations. It was breathtaking. Other events were more like his Dad's stuff, but still orchestra was involved - jazz band in the middle of the pit that I'd shield with plexiglass and absorbers that had to stay low so everyone could see the muso's - yet it had to work.

 

So Chris Brubeck and I would sit at a center location a few rows back from the stage and mix the event. I had an iPad that was connected to my CL5 (Yamaha) console that allowed me as much control as I wanted for up to 64 channels. And Chris would say something like "a bit more from the winds", or more often "timpani! more!" and I'd do that and he'd smile to the moon.

 

That four year old inside me actually pulled it off. : )

 

Now what to do? Home audio. Yet I'm still hesitant and my answer may not be very helpful:

 

Amps I have and am familiar with are McIntosh MC275 CE (restored with the best stuff I could find, noise is lower, power higher than specs), Mark Levinson 532H, Benchmark AHB2, and a bunch of professional stuff left over from the business, the only one that sounds really good is a German Camco Vortex 6, second best was the Yamaha TXn series, then all the class D stuff that I've yet to find acceptable from anyone for any other purpose than subs.

 

Well designed solid state rules. You can hear the reverb of the room in good recordings, subtle stuff is all there IF the loudspeakers are up to the task. Tubes are lovely - I could live with them alone quite happily, but they just don't have the "straight wire with gain" thing going on. My hat's off to all you guys that match all this stuff together to get the most euphoric result, but I'm about the math - I want the modifications (technically called distortion) removed to the greatest extent possible.

 

But I'm human. I cry during Stravinsky's Rite of Spring or Shostakovich's 5th Symphony or Holst's Planets or Yes's Fragile or anything Emerson Lake & Palmer. So the AHB2 is right down my alley but way too small in output for my needs (thus the 532H) until NOW.

 

NOW is a pair of '74 Klipschorns I drove to South FL to purchase and have restored. The bass is equal to concert sound - even close to the drum kit - it's all there. It scared me the first time I heard them. So good I turn it up louder than live - still crystal clear - all with the tiny AHB2. It loafs - doesn't even get warm. I'm going through my 3rd iteration at the moment on the KH tops. Aiming at a two-way system, but I'm not religious about it - thus tomorrow a pair of B&C DCX464's are arriving with those giant horns they designed for them. The funny thing is I already found a solution that brings 99% of the holographic female voice into my living room that my redesigned Martin Logan '83 CLS electrostatics do - and this solution is a...

 

For another post. : )

 

God bless you and your precious family - Langston

Edited by Langston
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The Benchmark has been around for many years with much praise. Great choice I am sure but never heard one. For what they charge for one I am disappointed that they chose a switching PS over a linear one. I am sure it was for larger profits but it works and has shown to be dependable. I was snobbish once only considering class A for myself but after building one of the best design class A/B amplifier circuit it changed my mind over the sound they can produce. As good as the best class A I have heard. Also use to turn my nose up on class D but they are now at audiophile level. One of the newer designed class D amplifiers would be a good choice as well. The TPA 3255 module is the one that changed my mind on class D. All the previous ones, many tried over the years, were thin sounding to me. Not the TPA 3255 board. Ice board amplifiers sound really decent as well. I have 2 amplifiers with the TPA 3255 boards and one amplifier with an ice board. Could live with them if only amp I could have. 

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34 minutes ago, henry4841 said:

The TPA 3255 module is the one that changed my mind on class D.

 

I'm open-minded about that and seriously hope that class D can approach "straight wire with gain" territory, it's just that I haven't heard it do so yet. Class A was off limits to me until the Klipschorn, which is so efficient that anything will do power wise. I have a feeling that John Siau chose switching power supplies for performance reasons vs. economic, but I'm a fan-boy and might be wrong. Here's what he wrote about it.

 

God bless you and your precious family - Langston

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9 hours ago, Langston said:

 

I'm hesitant about subjective impressions of stuff because humans are all over the map on this kind of thing depending on background and disposition. On the latter I'm all about Galileo's scientific method - but I also fell in love with Dave Brubeck's Take Five album when my Dad played the record on our living room entertainment system in 1963 when I was four. It stunned me and though my career was mostly in finance, science and teaching - Brubeck haunted me.

 

So just after the year 2k I decided that I had enough loot to do something stupid, so I started a concert production company from scratch with the goal to provide the highest possible sound quality even if I lost money in the process. Unfortunately it succeeded and I kept at it until a couple of years ago. I'd achieved what I wanted - a clientele that would pay for my very best effort. The icing on the cake was the oldest and most talented of Dave Brubeck's kids, Chris, used me when he did stuff in the area I covered. Yes I'm bragging. Chris writes symphonies that are usually thematic, such as an Ansel Adams piece with full orchestra and a huge screen fading in and out of different pictures of that amazing black and white photographer while the music did interpretations. It was breathtaking. Other events were more like his Dad's stuff, but still orchestra was involved - jazz band in the middle of the pit that I'd shield with plexiglass and absorbers that had to stay low so everyone could see the muso's - yet it had to work.

 

So Chris Brubeck and I would sit at a center location a few rows back from the stage and mix the event. I had an iPad that was connected to my CL5 (Yamaha) console that allowed me as much control as I wanted for up to 64 channels. And Chris would say something like "a bit more from the winds", or more often "timpani! more!" and I'd do that and he'd smile to the moon.

 

That four year old inside me actually pulled it off. : )

 

Now what to do? Home audio. Yet I'm still hesitant and my answer may not be very helpful:

 

Amps I have and am familiar with are McIntosh MC275 CE (restored with the best stuff I could find, noise is lower, power higher than specs), Mark Levinson 532H, Benchmark AHB2, and a bunch of professional stuff left over from the business, the only one that sounds really good is a German Camco Vortex 6, second best was the Yamaha TXn series, then all the class D stuff that I've yet to find acceptable from anyone for any other purpose than subs.

 

Well designed solid state rules. You can hear the reverb of the room in good recordings, subtle stuff is all there IF the loudspeakers are up to the task. Tubes are lovely - I could live with them alone quite happily, but they just don't have the "straight wire with gain" thing going on. My hat's off to all you guys that match all this stuff together to get the most euphoric result, but I'm about the math - I want the modifications (technically called distortion) removed to the greatest extent possible.

 

But I'm human. I cry during Stravinsky's Rite of Spring or Shostakovich's 5th Symphony or Holst's Planets or Yes's Fragile or anything Emerson Lake & Palmer. So the AHB2 is right down my alley but way too small in output for my needs (thus the 532H) until NOW.

 

NOW is a pair of '74 Klipschorns I drove to South FL to purchase and have restored. The bass is equal to concert sound - even close to the drum kit - it's all there. It scared me the first time I heard them. So good I turn it up louder than live - still crystal clear - all with the tiny AHB2. It loafs - doesn't even get warm. I'm going through my 3rd iteration at the moment on the KH tops. Aiming at a two-way system, but I'm not religious about it - thus tomorrow a pair of B&C DCX464's are arriving with those giant horns they designed for them. The funny thing is I already found a solution that brings 99% of the holographic female voice into my living room that my redesigned Martin Logan '83 CLS electrostatics do - and this solution is a...

 

For another post. : )

 

God bless you and your precious family - Langston

I cannot thank you enough for your thoughtful post.  I will take a sentimental journey over mindless hyperbole any day- with a cliffhanger thrown in at the end no less.  I share your adoration of Brubeck- Concord on a Summer Night is a go to mind trip for me.    It seems we are on somewhat the same approach and I was thrilled to see you mention that the Bench Mark is a good match with Khorns.   I have a pair of '79 Ramblin' Rose that I've also bastardized in my own fashion-  Volti horns with the BMS 4592nd and Fostex t500a MK3 tweeters.  I have done the tube amp shuffle and agree wholeheartedly that while they have their charm, a system based on efficiency and uber low distortion should not be wrapped in a wool rug so while I started to cast eyes at the various  Pass designs, I came across the Benchmark and can't seem to get it out of my mind.  Of course the wife agrees that I'm indeed out of my mind, but that is a different matter entirely.

 

I look forward to seeing what you've come up with.

 

My best to you and yours as well! 

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7 hours ago, Langston said:

 

I'm open-minded about that and seriously hope that class D can approach "straight wire with gain" territory, it's just that I haven't heard it do so yet. Class A was off limits to me until the Klipschorn, which is so efficient that anything will do power wise. I have a feeling that John Siau chose switching power supplies for performance reasons vs. economic, but I'm a fan-boy and might be wrong. Here's what he wrote about it.

 

God bless you and your precious family - Langston

John Siau, I did not know who he was, is pitching his product and of course he is going to sing praises of using a cheaper alternative to the more expensive linear PS that is superior in many more ways technically. Those with an electronic background understand this statement purely from a technical understanding of components and circuitry. But hey, it works and has a reputation of dependability. The latest diy product of Nelson Pass, of which I have but not completed because to health issues, uses a switching power supply and the ones that have completed this product, a SE V-fet amplifier, say how quiet the noise level is. Many though that have completed the project have made the comment that they are going to build a linear supply for the project at some time in the future because they know the benefits of a linear supply. Face it a big expensive transformer  with expensive capacitors is required for a linear supply vs the light weight switching supply used in the project and also in the Benchmark. Most all I have said on this subject, linear vs switching doesn't really matter if both work as intended and are dependable. 

 

I use to also be one of them that was searching for straight wire with gain in an amplifier but now that I am old my attitude has changed to the camp of Passlabs and First Watt. The designer of the company is Nelson Pass and he has stated that for years he built amplifiers with the goal of straight wire with gain with low distortion numbers. But now he designs amplifiers that sound great to him and hopes others hear the difference and buys enough of his products for his companies to survive. From all appearances he has achieved his goal in that he has a loyal following that purchases his products. In case you do not know much about Nelson he is considered a legend in audio amplification in a class all his own. There was a designer many years ago, his name escapes me right now, that said the best sounding amplification had a certain amount of 2nd harmonics and a touch of 3rd. Nelson has intentionally introduced some 2nd harmonics in his amplifiers along with designing amplifiers that naturally have a touch of 2nd harmonics. As Nelson has stated many times he is in the entertainment business and not scientific products. 

 

All this talk of straight wire with gain is for the young audiophiles trying to say do not chase numbers as I once did 40 years ago. I bought an expensive pre amplifier years ago in my youth with numbers lower than the equipment used to test it. It is now considered by most as not that great sounding and I can agree. Lasted 30 years without a problem as did the same brand amplifier so they were well made but not the best sounding. If I had it to do over again I would have bought a tube McIntosh which was about the same price and is now worth more than the cost back then. To me a SET tube amplifier is what I listen with most of time with plenty of the sweet 2nd harmonics many of use just love. It is like magic to my ears. Holographic is how many describe the sound. As if a singer is in the room with you. 

 

PS:

Jean Hiraga is who is quoted as saying some 2nd harmonics with a touch of 3rd sound best to him. A legend also in sound. Had to do some googling to remember his name. I have got way off the OP topic of Benchmark amplifiers. I am almost positive, because of it's loyal following that praises it's sound, that it was not designed to be straight wire with gain. From all that I have heard over the years it has to be an excellent sounding amplifier worthy of consideration. There are many members on this site that have had many different amplifiers that consider it their choice in amplification There is no one amplifier that fits all. 

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Not to beat a dead horse but this quote is from a thread on Nelson Pass' SE V-fet project on the SMPS included in the kit build of the SE V-fet amplifier. For those that are not familiar with a V-fet (SIT) transistor it has the curves of a triode amplifier. In other words a triode tube like SS device. Makes one wonder how much if any better the Benchmark amplifier would sound with a linear PS. 

 

"I have viewed this as an exercise in revealing the full potential of the amplifier. The SMPS that is part of the kit does a good job and will make some (or most) amp builders very happy. It is a cost effective solution. It does not let the amp perform at its very best. The only way to find this out is to build an alternative PSU and listen carefully to the results.

The discussion of alternate linear PSU designs is a way of exploring different ways of letting this VFET amp sound its very best."

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On 6/16/2021 at 2:05 PM, henry4841 said:

John Siau, I did not know who he was, is pitching his product and of course he is going to sing praises of using a cheaper alternative to the more expensive linear PS that is superior in many more ways technically. Those with an electronic background understand this statement purely from a technical understanding of components and circuitry. But hey, it works and has a reputation of dependability. The latest diy product of Nelson Pass, of which I have but not completed because to health issues, uses a switching power supply and the ones that have completed this product, a SE V-fet amplifier, say how quiet the noise level is. Many though that have completed the project have made the comment that they are going to build a linear supply for the project at some time in the future because they know the benefits of a linear supply. Face it a big expensive transformer  with expensive capacitors is required for a linear supply vs the light weight switching supply used in the project and also in the Benchmark. Most all I have said on this subject, linear vs switching doesn't really matter if both work as intended and are dependable. 

 

I use to also be one of them that was searching for straight wire with gain in an amplifier but now that I am old my attitude has changed to the camp of Passlabs and First Watt. The designer of the company is Nelson Pass and he has stated that for years he built amplifiers with the goal of straight wire with gain with low distortion numbers. But now he designs amplifiers that sound great to him and hopes others hear the difference and buys enough of his products for his companies to survive. From all appearances he has achieved his goal in that he has a loyal following that purchases his products. In case you do not know much about Nelson he is considered a legend in audio amplification in a class all his own. There was a designer many years ago, his name escapes me right now, that said the best sounding amplification had a certain amount of 2nd harmonics and a touch of 3rd. Nelson has intentionally introduced some 2nd harmonics in his amplifiers along with designing amplifiers that naturally have a touch of 2nd harmonics. As Nelson has stated many times he is in the entertainment business and not scientific products. 

 

All this talk of straight wire with gain is for the young audiophiles trying to say do not chase numbers as I once did 40 years ago. I bought an expensive pre amplifier years ago in my youth with numbers lower than the equipment used to test it. It is now considered by most as not that great sounding and I can agree. Lasted 30 years without a problem as did the same brand amplifier so they were well made but not the best sounding. If I had it to do over again I would have bought a tube McIntosh which was about the same price and is now worth more than the cost back then. To me a SET tube amplifier is what I listen with most of time with plenty of the sweet 2nd harmonics many of use just love. It is like magic to my ears. Holographic is how many describe the sound. As if a singer is in the room with you. 

 

PS:

Jean Hiraga is who is quoted as saying some 2nd harmonics with a touch of 3rd sound best to him. A legend also in sound. Had to do some googling to remember his name. I have got way off the OP topic of Benchmark amplifiers. I am almost positive, because of it's loyal following that praises it's sound, that it was not designed to be straight wire with gain. From all that I have heard over the years it has to be an excellent sounding amplifier worthy of consideration. There are many members on this site that have had many different amplifiers that consider it their choice in amplification There is no one amplifier that fits all. 

 

Apparently it's trickling down-  

 

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