Commercially available current dumping amps?

[Key]

Commercial?!

Just wondering whats to be had for modding or reverse engineering. Here are the ones I know of.

The obvious Quad 909
http://www.quad-hifi.co.uk/model.php...=3&model_id=12

The much less obvious Wharfedale Pro S Series (I am eyeing the S1000 unless you can point me to something better)
http://wharfedalepro.com/Home/Produc...2/Default.aspx

Linn Chakra and Majik series
http://www.linn.co.uk/music_systems_...hakra_500_twin
http://www.linn.co.uk/music_systems_majik_2100

Overlooked active speakers

Quad L series
http://www.quad-hifi.co.uk/ranges.ph...d=2&range_id=5

Quad Pro (11L)
http://www.quadindustrial.com/Produc...6/Default.aspx

Wharfedale Pro Diamonds (never listed in the specs but the path of least resistence makes me believe they would use a current dumper to make assembly line easier and cut cost of the amps) I use the active 8.2s
http://wharfedalepro.com/Home/Produc...4/Default.aspx

Are the Linn active monitors using current dumping?

Anyway those seem to be all of the easier ones to find. I have seen some of the DIY stuff on this board like the Quasar etc.. But was wondering if there are any other solutions (Kits, premade whatever) that I am overlooking.

One thing I would like to do is try to beat the speakers I am currently using. But it seems like an expensive task considering most every other speaker I will have to gut the passive crossover, either use a digital or active crossover, and buy 4 channels of current dumping (make that 8 since I use a quadraphonic setup) to even match the performance I am getting out of the Diamond 8.2 actives.

[Fanuc]

Originally posted by Key
Commercial?!

Just wondering whats to be had for modding or reverse engineering. Here are the ones I know of.

The obvious Quad 909
http://www.quad-hifi.co.uk/model.php...=3&model_id=12

The much less obvious Wharfedale Pro S Series (I am eyeing the S1000 unless you can point me to something better)
http://wharfedalepro.com/Home/Produc...2/Default.aspx

Linn Chakra and Majik series
http://www.linn.co.uk/music_systems_...hakra_500_twin
http://www.linn.co.uk/music_systems_majik_2100

Overlooked active speakers

Quad L series
http://www.quad-hifi.co.uk/ranges.ph...d=2&range_id=5

Quad Pro (11L)
http://www.quadindustrial.com/Produc...6/Default.aspx

Wharfedale Pro Diamonds (never listed in the specs but the path of least resistence makes me believe they would use a current dumper to make assembly line easier and cut cost of the amps) I use the active 8.2s
http://wharfedalepro.com/Home/Produc...4/Default.aspx

Are the Linn active monitors using current dumping?

Anyway those seem to be all of the easier ones to find. I have seen some of the DIY stuff on this board like the Quasar etc.. But was wondering if there are any other solutions (Kits, premade whatever) that I am overlooking.

One thing I would like to do is try to beat the speakers I am currently using. But it seems like an expensive task considering most every other speaker I will have to gut the passive crossover, either use a digital or active crossover, and buy 4 channels of current dumping (make that 8 since I use a quadraphonic setup) to even match the performance I am getting out of the Diamond 8.2 actives.

A crude way of dealing with the Class B stage output stage. Put a scope on the supply lines and you will still get nasty odd harmonics. Deals with half the problem.

Go Class A - problem solved. Be intelligent.

[Key]

Hehe I am not even sure all of those are CDs when I look at them today. I mean maybe that wharfedale is really just AB.

Anyway I think it's the distortions I might like. I suck at electronics and electronic theory for the most part so all I know is what I think I am hearing. And to my ears these speakers reproduce recorded distortions (guitars, synths etc...) more accurately than any other amp/speaker combo I have heard so far. Most of the other ones seems to take distortions and smooth them over some how.

I could be totally wrong and it is just a way to cut costs but I am just following what I hear.

[Fanuc]

Originally posted by Key
Commercial?!

Just wondering whats to be had for modding or reverse engineering. Here are the ones I know of.

The obvious Quad 909
http://www.quad-hifi.co.uk/model.php...=3&model_id=12

The much less obvious Wharfedale Pro S Series (I am eyeing the S1000 unless you can point me to something better)
http://wharfedalepro.com/Home/Produc...2/Default.aspx

Linn Chakra and Majik series
http://www.linn.co.uk/music_systems_...hakra_500_twin
http://www.linn.co.uk/music_systems_majik_2100

Overlooked active speakers

Quad L series
http://www.quad-hifi.co.uk/ranges.ph...d=2&range_id=5

Quad Pro (11L)
http://www.quadindustrial.com/Produc...6/Default.aspx

Wharfedale Pro Diamonds (never listed in the specs but the path of least resistence makes me believe they would use a current dumper to make assembly line easier and cut cost of the amps) I use the active 8.2s
http://wharfedalepro.com/Home/Produc...4/Default.aspx

Are the Linn active monitors using current dumping?

Anyway those seem to be all of the easier ones to find. I have seen some of the DIY stuff on this board like the Quasar etc.. But was wondering if there are any other solutions (Kits, premade whatever) that I am overlooking.

One thing I would like to do is try to beat the speakers I am currently using. But it seems like an expensive task considering most every other speaker I will have to gut the passive crossover, either use a digital or active crossover, and buy 4 channels of current dumping (make that 8 since I use a quadraphonic setup) to even match the performance I am getting out of the Diamond 8.2 actives.

PS. You heard a excellent quality binaural recording on directly driven electrostatic headphones. ? Fulll 360 degress spatial information. 5.1 or 7.1 is no competition

OK Regarding speakers. I have bought Kef reference Model 4's. First upgrage will be the Uni Q drivers. The latest ones from the newest models are titanium (might need some Xover circuitry) and have a flat response to 60Khz. (no supertweeter reg'd)

Apparently they can give me electrostatics a run for there money. Jazz and red wine will determine that. But I am a cynic.

[Key]

Sure have. And to tell you the truth the quad decoder kicks the headphones **** all over the place. With binaural decoding, realism as well as surreal mixing.

Yeah I think these speakers resemble the Quad 10L 11L 12L except for the monopole design. They give a decent midband frequency response that sounds similar to a planar. With the right source I bet you would have to A/B to hear the difference really.

[Wavebourn]

Originally posted by Key


Anyway I think it's the distortions I might like.

[...]

I could be totally wrong and it is just a way to cut costs but I am just following what I hear.

There are no "good" distortions!

Some of them are more audible, some are less. For example, vintage class A tube amps had the more distortions the higher the power, that's why they were measured for percent of distortions per power, or for higher power with less percent of distortions.
It was a comparison of apples to apples.

When push-pull amps were made they allowed to jump to the next step in the game: being more efficient they produced more power per the same percentage of distortions.
It was a comparison of apples to oranges, since push-pull amps had less of even-order distortions, so measurements were better even when they sounded the same or worse.

Transistor amps could not work without deep negative feedbacks that linearized transistor stages. As the result of feedback overall percentage of distortions on higher power was very low. It was easy for them to generate less of harmonic distortions' percentage on higher power!

It was a comparison of apples to shrimps... Transistor amps were optimized for higher output per consumed from outlet power, in order to achieve this criterion they were made such a way, the lower is power, the higher is level of distortions, the wider is specter...

But the higher is sound pressure level, the more forgiving is our perception to non-linear distortions. Reason: all physical media distort, including one of which our ears are made. "Natural" distortions add perception of higher volume, it is hard to tell what distorts, the amp or the air (or the ear!). But however the less of them is added by electronics, the more are allowed for an air and ears.

When oscillating physical media distort sounds the higher is it's deformation the higher is pitch of distortions. When you kick a piano string by it's hammer hard you hear higher harmonics, if to speak language of Fourier transforms. If you play soft you hear lower order of harmonics. When the natural sound decay higher harmonics decay faster. So, when an amp generates higher harmonics on higher power our perception forgives that. But when on lower power percentage of distortions goes up and specter goes wider it is unnatural, contrary to expectations, and such an amp sounds less natural.

So, the right amp have to distort the less the less is the power. But how many of them are forgivable on higher power? As less as possible.

You probably can't hear distortions of some vintage class A amp on higher power on a saxophone, or a human voice solo; it will be perceived like harmonics of the same instrument, but an ensemble or a chord of one instrument have more than one note playing simultaneously, so inter-modulating they will produce harsh sounds that did not present originally.

There are no such devices that don't distort. The ideal device should have a transfer function Y=X*K where X - input signal, K - amplification coefficient.
We can imagine an exponential transfer function as a sum of functions of different orders, like Y=K1*X + K2*X^2 + K3*X^3 +K4*X^4, and so on. Very short part of this function may be seen as a linear one; the finer are chunks, the closer each one seems to be to a linear function. That means, we have to take a real device with higher gain than needed, but use a small part of it's characteristic. No other ways exist.

Another problem is, each device need time to react. What is worse, speed of reaction is modulated by the signal itself. Theoretically is seems simple:

1. Take an amp with fewer tubes, enormous power capabilities with less power losses from stage to stage, but use a little bit of it's power amplification capabilities. It is a very expensive way, and it has a limit: the more of power is dissipated, the heavier are parts, the more reactive they are, the more noises and frequency dependencies your get.

2. Take an amp with enormous gain, add feedback, and it's curve is straightened. The problem is, a first, low order function multiplied by itself gives higher order. Lowering distortions that our perception can forgive we are adding what it forgives less. Second, because of the time needed for reaction for each amplification stage phase shifts are accumulated from stage to stage, and on some high frequency where phase shift is 180 degrees a negative feedback becomes a positive one forcing an amp to oscillate, if the overall gain through the loop on this frequency is slightly higher than one. Now, we need to compensate the amp to stop oscillations, for example adding higher losses on that frequency, but the same time slowing down it's reaction!

There is the 3'rd way: linearization. For example, assisting a device with more devices that stretch it's transfer function. For example, a triode may be loaded on a constant current source. Or a source follower bootstrapped.

And, finally, the 4'th way: use optimal combination of all 3, optimizing such a way that most audible distortions will be mostly minimized. No amps with no distortions can be made. Add here speakers that are driven by amps, so the system containing an amp and speakers have to be optimized together, otherwise a perfect by itself amp with a perfect by itself speaker in combination produce worse sound than less expensive combination that had been optimized all together.

So called "Current Dumping" is the way to combine low distortions on low power (fair class A stage) and low distortions on high power (class C). Transition from class A to class C is smooth because of properly adjusted feedbacks, so really "Current Dumping" amps are cleaner than the majority of class AB amps.

I designed similar amps (I mean approximation of transfer function similar to what Current Dumping does), and results always were excellent.

[Key]

I would disagree that distortions are always bad. I think they can add realism when used for that purpose.

Anyway I am not talking about introducing distortions that shouldn't be there. I am talking about *reproducing* distortions as they were originally recorded. This is something you can not put on a spec sheet. That characteristic and a strong stereo image are right up at the top with frequency response for what I look for in a playback chain.

[Fanuc]

Originally posted by Key
Sure have. And to tell you the truth the quad decoder kicks the headphones **** all over the place. With binaural decoding, realism as well as surreal mixing.

Yeah I think these speakers resemble the Quad 10L 11L 12L except for the monopole design. They give a decent midband frequency response that sounds similar to a planar. With the right source I bet you would have to A/B to hear the difference really.

Never underestimate headphones. Recordings are mastered for speakers not 'phones. They do not suffer from room acoustics etc (a serious problem with speakers). Performance can be stunning from some types I heard.

[Key]

Oh no doubt. I love me some stereo and some binaural. Variety keeps things interesting.

And I'm not so sure about the acoustics thing. I have an easier time blocking out acoustics, if I get rid of any early reflections, than I do with in head localization. I always start playing illusion tricks on myself with headphones like inverting the imaging etc... Or making clockwise panning go the other way (I suspect this has to do with our relation to the equator)

[Professor smith]

''We can imagine an exponential transfer function as a sum of functions of different orders, like Y=K1*X + K2*X^2 + K3*X^3 +K4*X^4, and so on. Very short part of this function may be seen as a linear one; the finer are chunks, the closer each one seems to be to a linear function''

How can we make this statement more rigorous?