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Old 18th October 2013, 04:29 PM   #1
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Default Benchmark has a NEW power amp.The best ?

Benchmark appears to have a new power amp. The blurb claims it to be better than all present day power amplifiers.
AHB2 - Power Amplifier | Benchmark Media

So did anyone get to hear it at RMAF ? How was it ?
Cheers.
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Old 18th October 2013, 10:01 PM   #2
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Quote:
Originally Posted by ashok View Post
Benchmark appears to have a new power amp. The blurb claims it to be better than all present day power amplifiers.
AHB2 - Power Amplifier | Benchmark Media

So did anyone get to hear it at RMAF ? How was it ?
Cheers.
No, but it is always handy and fun to lookup the company address on Google Street Maps. These guys occupy Suite 2 in this building. They don't even display their company name. Makes you wonder.
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Old 19th October 2013, 03:01 AM   #3
RNMarsh is offline RNMarsh  United States
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All we need to do now is find out more about the licensed circuit design/topology from THX. Maybe a patent we can look up and find out what the new idea is and does. There is always another way once you have the Idea.

Thx-RNMarsh
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Old 19th October 2013, 05:38 AM   #4
fas42 is offline fas42  Australia
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Here are THX'es patents, https://www.google.com/search?tbo=p&...ltd%22&num=100 - Most likely are the Low Dissipation Amplifier, and Power Supply ...
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Old 19th October 2013, 08:17 AM   #5
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Very nice concept. Can give you an implementation if you like
Have two ouput stages ie combine Dougs XD with another XD on the opposite rail
Then invite the puppies for a race with SYMEF
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Old 19th October 2013, 08:43 AM   #6
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For class XD, D stands for switching and X stands for modified thus class XD translates to modified switching point.
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Old 19th October 2013, 09:23 AM   #7
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The efficient power amplifier was described as a summer project in Elector of 1982 and was also used by several Japanese amplifier companies at the time, so nothing new here. The distortion reducing schemes correlate with publications from Sigfried Linkwitz also from the eighties.

Why not simply patent electronic engineering and nobody can do nothing without paying everyone something.
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Old 27th October 2013, 01:52 AM   #8
jsiau is offline jsiau  United States
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Originally Posted by fas42 View Post
Here are THX'es patents, https://www.google.com/search?tbo=p&...ltd%22&num=100 - Most likely are the Low Dissipation Amplifier, and Power Supply ...
This is John Siau, VP and chief engineer at Benchmark

The THX patents are:

8,004,355
8,421,531

The patented topology uses feed-forward error correction to virtually eliminate crossover distortion. The technique is so effective that the output stage can be run in class-B operation while achieving very low distortion. This also allows class-H or class-G tracking rails without the usual distortion problems associated with these designs. THX has demonstrated a design that rivals the efficiency of class D amplifiers.

The THX topology was interesting to Benchmark for an entirely different reason:

The same feed forward error correction can be used to remove crossover distortion from a class-B amplifier can be used with class AB biasing to create an amplifier with extraordinarily low distortion.

Our goal was to achieve very low distortion, with a focus on low crossover distortion. We were willing to increase the power dissipation as much as necessary to optimize the distortion performance. The optimum solution uses some bias current, but much less than a traditional class AB. Distortion of the AHB2 is at the measurement limits of our AP 2722 and 2522 test stations.

The THX topology also allowed us to utilize two power supply rails in a class-H (or G) configuration without any measureable distortion penalty.

The AHB2 is significantly more efficient than a traditional class AB, and has much lower distortion. Power consumption is only 20W idle. A traditional class-AB of equivalent power would consume 100 to 120 W idle. For example, the similarly sized Bryston 3B consumes 120W idle.

Benchmark chose to build the amplifier with very low gain. Gain is only 9 dB instead of the more typical 20 to 30 dB gain found in most power amplifiers. This means that the AHB2 clips with a 22 dBu input instead of an 8.2 dBu (2 V RMS) input. The AHB2 is designed to accept studio-level input levels and this can significantly improve noise performance between connected devices. In my opinion, most power amplifiers have far too much gain.

Our design goals included a 130 dB SNR relative to maximum output. To achieve this performance we used very low impedances, and some very unique PCB layout techniques. We also chose to use a switching power supply so that we could eliminate 60 Hz magnetic components. The magnetic fields produced by a high frequency switching supply are much lower and are out-of-band.

We also chose a tightly regulated power supply. Most power amps use unregulated supplies because this is the most efficient use of resources if switching supplies are not used. Given switching supplies, tight regulation comes almost for free. Better yet, the power supply control loop can be made fast enough to react to all audio frequencies. The AHB2 does not rely on secondary capacitive storage.

We will be posting performance plots and measurements on our website soon.
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Old 27th October 2013, 02:33 AM   #9
Bigun is offline Bigun  Canada
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Very interesting. From the description I suspect that Vanderkoy and Lipshitz would recognize some of this (i.e. it reminds me of their paper on how a low power small amplifier drives current-dumping Class B amplifier). Or is this something more akin to Graham Maynards GEM amplifier.

Well John, your new amp sounds like it will be very nice; it would be interesting to see a DIY version, perhaps if the patents are adequate protection you'd be willing to volunteer a simplified schematic for us to think about ?
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Last edited by Bigun; 27th October 2013 at 02:43 AM.
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Old 27th October 2013, 02:50 AM   #10
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Finally a manufacturer who is acknowledging the ridiculous gain levels of audio systems and recordings these days!
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