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$500 amplifiers to test and review?

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The crown xls1502 would be a good replacement, slightly better than the a500 especially at low frequencys. The a800 is cheaper and has more power than the crown so it would be interesting to see how the 2 compare.
They have different applications: Crown it's a PA amplifier, A500 and A800 are both "studio reference" amps.
 
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Hello from France,
To have just the fusion amp module for testing, Hypex is the way to go....
I think that Audiophonics preference is to send a complete amplifier, not just a component from Hypex.

But your link to the fusion amp is interesting...
Sincerely yours

Habu
 

amirm

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What ?
Do you BUY amps for your tests ?!?
I buy a lot of gear for my tests. Unfortunately some test poorly and then I get stuck with them.
 
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About the new Behringher A800, an italian owner claims that:
It's an extraordinary amp. Power not exaggerated. Transparent, sweet, with a huge soundstage. Outclass all the class D that I've tried so far ... Tested with Magneplanar 1.4 and Audio Pro 2-25.

...of course an objective measurement would be better !
 

tired_guru

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Would be great to finally measure some of current mode headphone amplifier (patented by questyle). I know this is more about speaker amps but the idea is quite interesting and wasn't mention much here (btw it's not only for headphones, also there are amps for speakers too). There is quite of a story behind it and seems to be something completely different than common approach.

Birth of the current mode audio amplification technology:

Six years ago, when we were studying the high speed current mode communication circuit in our lab, accidentally we found out this circuit couldn’t process the communication signal but it had the excellent audio performance. Then we started to made researches on current mode technology to see whether it could be used for audio amplification. After two years of unremitting efforts, the first current mode audio amplifier was born, which was designed with the entirely new ideas and topological structure. This current mode audio amplifier has the amazing frequency band of 1MHz at 2*100w output, the IMD is too low to be tested.

Patent on current mode amplification
Global PCT No.:PCT/CN2014/075775

In 1970, Dr. Otalc proposed the theory of transient inter modulation distortion (TIMD), which pointed that the traditional transistor amplifier, when processing the high frequency signals of great dynamic, would cause the TIMD. The TIMD can be measured and the unpleasant sound caused by it can be clearly heard. There is no simple and effective way found to solve this problem up to now. Many Hi-end manufacturers like using non-feedback technology to avoid TIMD, which not only costs dear, but also can’t ensure the system to be stable enough.

In 1989, English scholar D.C Wadsworth firstly put forward an idea of applying the current mode circuit into audio system at the 87 session of AES meetings. He pointed that current mode circuit could lower the TIMD significantly and it was the only way near to perfect analog amplification. In 2006, we applied for the invention patent of current mode amplifier. Through 5 years’ continuous study and 22 different experiments and tests, till the year 2011, the first current mode headphone amplifier CMA800 was born. Current mode amplifier achieves the ultra-high speed and ultra-low distortion; it perfectly catches the dynamics and transparency of the music; it precisely uncovers the details buried deep in the audio track. It is almost a perfect analog amplifier.

Current Mode Amplification , referring to a Current Mode Audio Amplifier, is a patented technology of Questyle Audio. It is a state-of-the-art technology of audio amplification different from the traditional audio amplifier. As the "engine" of audio system, Current Mode Amplification, featuring a fully discrete and topological structure, achieves ultra-high sound performance close to recording scene that makes audience truly moved. Meanwhile, based on Current Mode Amplification technology, users can get much better listening experience than common devices even they match with their own headphones or speakers rather than the original collocation.

Current Mode Amplification features the use of transistors to amplify and a fully discrete structure, to wit: voltage input and output, while the core amplification takes place in the current domain operating in a pure Class A state. It is completely different from the traditional voltage mode amplifier in the structure of the amplification circuit. Current-mode audio amplifiers affect the speed and bandwidth of the transistor-level capacitance between the low impedance nodes, not only completely eliminates the transient intermodulation distortion (TIMD), but can easily attain ultra-high bandwidth (full power bandwidth of 500kHz ) and ultra-low distortion (lower than 0.0002% THD+N, challenging the physical limits of audio testing). The Current Mode Amplification technology can be used for amplifiers of any power level (10mW-2000W) and of any size (thousands of square centimeters for some professorial amplifiers).



How dose Current Mode Amplification work?


It is basically made up of voltage-controlled current source (VCCS), current mode amplification unit(A(i)), I/V converter, output stage(OPT)and negative feedback. In the science of electronics, voltage and current exist side by side, power (Watts) is the product of the two, so you can amplify either current or voltage. In the current amplification stage, signals are amplified in current to achieve higher performance, while the input and output stages remain voltage. This kind of design is easily compatible with other advanced sources and loads. It is an open system for the demanding user who likes high-end products.


As shown by the diagram, the input signal goes into VCCS first and the VCCS converts input voltage to current which goes into Ai for current amplification, then it is converted to voltage by I/V converter to drive load through OPT.

Negative feedback is applied to guarantee stability. Because of the low impedance of the negative feedback and the high-speed performance of the amplifier, the processing speed of the feedback loop is hundreds of times faster than that of voltage mode amplifiers. So the issue of TIMD as produced in conventional amplifiers doesn't exist here.

What do you think about it Amir ?
 
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And Conclusions are:
The Behringer A500 is an amazing phenomenon at the price. There is nothing else like it. I’ll tell you what. If you need a new power amplifier, or maybe just a spare amplifier, throw caution to the wind. Be the last of the big-time spenders. Buy the A500 at the lowest price you can find (maybe $180?) and take a chance on it. After all, it comes with a one-year warranty.

I pleasurably use it in this chain:
PC -> Zoom R16 -> balanced connection -> Behringer A500 -> solid core cables -> ESB 7/09
 
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In 1970, Dr. Otalc proposed the theory of transient inter modulation distortion (TIMD), which pointed that the traditional transistor amplifier, when processing the high frequency signals of great dynamic, would cause the TIMD. The TIMD can be measured and the unpleasant sound caused by it can be clearly heard. There is no simple and effective way found to solve this problem up to now. Many Hi-end manufacturers like using non-feedback technology to avoid TIMD, which not only costs dear, but also can’t ensure the system to be stable enough.
Anything that starts the sales pitch with a throwback to Otala and TIM distortion pushes my BS-O-Meter so high that I immediately avoid the rest of the author's nonsense (particularly when they come up with a gem like there being "no simple and effective way to solve this problem until now"). Uhm, yeah, there is. TIM hasn't been a problem for nearly four decades, in any nominally competent design. Whatever they are selling, I am not impressed that they started the pitch with technobabble snake oil.
 
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amirm

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Negative feedback is applied to guarantee stability.
??? Negative feedback is used to improve performance. It can actually cause instability which is often a problem with wide-band current mode amplifiers.

But thanks for posting that. We should get one to measure. :)
 

tired_guru

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??? Negative feedback is used to improve performance. It can actually cause instability which is often a problem with wide-band current mode amplifiers.

But thanks for posting that. We should get one to measure. :)
Maybe in current mode drive and in this application it is used to boost stability. It's a bit reversed topology.

I got CMA400i once and it sounded completely different than any other headamp I had in the past. Extremely full, punchy, with great sense of depth, very high output power without hint of distortion even on very hard to drive headphones. Very interested in how it measures.

CMA400i is the cheapest one, I can get now one locally for only 500$ on sale.

The problem is this is DAC with AK4490 + current mode drive headamp (with both SE & BALANCED outputs), changeable gain but no direct access to the amp's input :(.

There are higher models with such possibility or just plain amps but cost much more unforturnately.

Just wanted to have your attention to this company Amir for the future testing - might be something different than anything around.
 
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Nate T

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Might be worth seeing if you could get your hands on an ICEPower-based DIY amp like this one:

Looks like an extremely simple DIY, and significantly cheaper than the Hypex.

Edit: I'd also be interested in hearing impressions on the build in that video from someone who knows what they're doing!
 

amirm

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I thought I recently reviewed an amp with the same modules. @Matey may remember.

Construction video is not half bad. Wiring harnesses with duplicate color wires is a disaster though. I am amazed no sells all the bits with proper color coding ready to go.
 

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