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what's 4-channel technology?

post #1 of 15
10/8/09 at 12:24pm
Thread Starter 
From Xin's fixup.net:


Quote:
You can see all the specs, tonal balance, S/N, dynamic range, THD, IMD and channel separation, are all at the extreme edge, unseen in the past. 4-channel technology does make huge differences!
what's 4-channel?
how can it make these shocking specifications?

this is the 4-ch schematic i guess from some information on the website:


compare to common 3-ch :



the main advantage of my "4-ch sch" is "not only isolate signal ground from the varying output ground as 3-ch do,but also isolate the latter from the former",but can this make that extremely high specifications?
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post #2 of 15
10/8/09 at 12:56pm
4 channel technology is sorta 3-channel with an added twist using fine literature and semantics.
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post #3 of 15
10/8/09 at 1:02pm
Not sure.

And he's not terribly forthcoming. Someone tried to press him for details and he responded with this silly comment:

Moxwell, forgive me that I cannot post on public the technical details. It is not very complicated to understand, but it did took me 4 years to figure it out. The Earth turns around Sun, how simple was that; but human used to believe it the other way, not long ago.

But he gives something more of a clue in his original post where he says this:

With my 4-channel technology, not only are the left and right channels separated like the dual-mono structure found in high-end home amps, so are the front and end stages, like the pre-power amps found in top-end home systems.

It seems what he's saying is that he has two channels used as a "preamp" and two channels used as the "power amp." Though I don't know how he gets that the left and right channels are separated like dual mono amps in high end home amps when the thing's built on a single circuit board and powered by the same power supply.

And when someone bills themself as a "former rocket scientist," my charlatan meter starts twitching.

se

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post #4 of 15
10/8/09 at 3:04pm
once again I'll point out that the crosstalk # is BS - to get to this level the measurement has to have been made on the pcb and/or without a headphone load - not at the headphone drivers, outside the amp where it counts

3-pin TRS common gnd connection to even 300 Ohm cans will not exceed ~80-90 dB separation due to the 10 mOhm common L/R gnd contact resistance

Neutrik 1/4" TRS Ag contact:
"
Electrical
Contact resistance < 6 mΩ (initial)
Dielectric strength 1 kVdc
Insulation resistance ≥ 1 GΩ @ 500 V dc
Rated current per contact 10 A
"
I have measured >10 mOhm common gnd + contact R with the Neutrik and <2" of wire to the panel

with 32 Ohm cans the the crosstalk wouldn't be better than ~70 dB
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post #5 of 15
10/8/09 at 3:22pm
Quote:
Originally Posted by dg3f View Post
the main advantage of my "4-ch sch" is "not only isolate signal ground from the varying output ground as 3-ch do,but also isolate the latter from the former",but can this make that extremely high specifications?
I see no more ground isolation in his circuit than I see in a three channel circuit. Which is none.

se

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post #6 of 15
10/8/09 at 5:14pm
Quote:
Originally Posted by Koyaan I. Sqatsi View Post
I see no more ground isolation in his circuit than I see in a three channel circuit. Which is none.

se
Oh lets not start that again
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post #7 of 15
10/8/09 at 5:25pm
Quote:
Originally Posted by FallenAngel View Post
Oh lets not start that again
Why not? Why are you such a big fan of people being misled?

se

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post #8 of 15
10/8/09 at 8:57pm
Quote:
Originally Posted by Koyaan I. Sqatsi View Post
Why not? Why are you such a big fan of people being misled?

se

for one, try explaining how TLE2426 sink all the ground current from the return load? (present in m3's schematic)
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post #9 of 15
10/8/09 at 9:30pm
Quote:
Originally Posted by TzeYang View Post
for one, try explaining how TLE2426 sink all the ground current from the return load? (present in m3's schematic)
The TLE2426 isn't the active "ground channel" that's been erroneously claimed to isolate load currents from ground.

Please take another look at the M3's schematic and note what is referenced as "Ground Channel."

se

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post #10 of 15
10/9/09 at 12:51am
Thread Starter 
Quote:
Originally Posted by Koyaan I. Sqatsi View Post
I see no more ground isolation in his circuit than I see in a three channel circuit. Which is none.

se
i found that all Xin's 4ch design has at least 3 bufs and 4 op,i am sure 2 OPs and 2 BUFs are for the common Left and Right channel.Then the rest one bufs must be cooperate with an OP because of the combination's low output impedance and powerful output capacity,which i guest must for a large need of current .What's most likely is a power output ground just like that in 3-ch topology.What's the rest one opamp used for confused me for a long time,it must be not a high current situation and can help more channel separation,then fews ago i think up the schematic above.i know 3-ch designs also use some caps in the output of tle2426 to reduce ripple to the input of the ground buffer,but my way seems a little bit more isolating.
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post #11 of 15
10/9/09 at 1:10am
Quote:
Originally Posted by dg3f View Post
i found that all Xin's 4ch design has at least 3 bufs and 4 op,i am sure 2 OPs and 2 BUFs are for the common Left and Right channel.Then the rest one bufs must be cooperate with an OP because of the combination's low output impedance and powerful output capacity,which i guest must for a large need of current .What's most likely is a power output ground just like that in 3-ch topology.What's the rest one opamp used for confused me for a long time,it must be not a high current situation and can help more channel separation,then fews ago i think up the schematic above.i know 3-ch designs also use some caps in the output of tle2426 to reduce ripple to the input of the ground buffer,but my way seems a little bit more isolating.
I'm still not seeing any ground isolation in either scenario.

Yeah, the TLE2426 will help with power supply rejection but that's a different issue from ground isolation.

se

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post #12 of 15
10/9/09 at 2:21am
Quote:
Originally Posted by Koyaan I. Sqatsi View Post
The TLE2426 isn't the active "ground channel" that's been erroneously claimed to isolate load currents from ground.

Please take another look at the M3's schematic and note what is referenced as "Ground Channel."

se
if it is not meant to isolate return currents, then why the TLE2426 is not sinking the high return currents from the headphones?

The TLE2426 can only maintain around 20mA until it breaks down. But it did not break down even if you drive 5V across 32 Ohms.
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post #13 of 15
10/9/09 at 2:35am
Quote:
Originally Posted by TzeYang View Post
if it is not meant to isolate return currents, then why the TLE2426 is not sinking the high return currents from the headphones?
Because it's the GROUND CHANNEL that's sinking the load currents. NOT the TLE2426.

Please read what I wrote.

The CLAIM is that the GROUND CHANNEL bypasses ground. That claim is incorrect. It does not bypass ground. The load currents flow through the ground node in either case.

Quote:
The TLE2426 can only maintain around 20mA until it breaks down. But it did not break down even if you drive 5V across 32 Ohms.
The TLE2426 has nothing to do with the output. Nor does it have anything to do with the claim that the GROUND CHANNEL bypasses ground. So why do you keep talking about the TLE2426?

se

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post #14 of 15
10/9/09 at 4:37am
Quote:
Originally Posted by Koyaan I. Sqatsi View Post
Because it's the GROUND CHANNEL that's sinking the load currents. NOT the TLE2426.
yes, and that is the reason behind the benefits of the three channel topology no? The ground reference plus the caps no longer see a dynamic return current.

Quote:
The CLAIM is that the GROUND CHANNEL bypasses ground. That claim is incorrect. It does not bypass ground. The load currents flow through the ground node in either case.
I agree. It does not bypass the ground, my understanding is that the load no longer sees a frequency dependent impedance (your caps) but sees a much stiffer, lower impedance across a larger spread of frequency.

Quote:
The TLE2426 has nothing to do with the output. Nor does it have anything to do with the claim that the GROUND CHANNEL bypasses ground. So why do you keep talking about the TLE2426?
because i think the three channel topology offers benefits, and i'd like to see if my understanding is correct.

Afterall, you think the ground channel does nothing for the return current.
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post #15 of 15
10/9/09 at 2:53pm
3/4 channel "active gnd" schemes are not going to beat a good implementation of star gnd - any buffer op amp will introduce noise from its input stage and distortion from the nonlinear operation of its AB output stage and frequency dependant output impedance from the buffer internal feedback

properly layed out Cu trace and wiring to the output TRS connector as star gnd point doesn't introduce extra active device noise, can be orders of magnitude lower in Z at high audio frequencies and can avoid "gnd contamination" by virtue of separating the pwr_gnd branch of the star gnd so that load current doesn't flow in the sig_ref or fdbk_ref gnd branches



pwr_gnd could be (preferably) the center of a symmetric battery stack or dual ps instead of the "active gnd" battery splitter shown

but the star gnd scheme is still superior with the "active gnd" as imperfections in the supply splitter op amp oputput become common mode ps terms and the channel amplifier op amp's cm psrr is usually higher than its feedback loop gain and always at least equal to the internal loop gain
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