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Old 7th April 2013, 09:19 AM   #1
Elvee is offline Elvee  Belgium
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Default Good old technology?

Hi

I have exhumed this unusual amplifier based on a patented idea: "constant power amplifier" by Nguyen Tan Tai:
Electronic power amplifier for delivering a constant power into a load impedance - United States Patent 4095189

Claims are no global feedback, load invariant output power, unexpected reproduction quality, and tube-like sound.
It is claimed that fifteen(!) 8Ω series-connected speakers do not alter the acoustic power.

I leave you to judge.....

Have fun!
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File Type: png NGTT.png (184.9 KB, 584 views)
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Old 8th April 2013, 06:57 AM   #2
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Quote:
Originally Posted by Elvee View Post
Hi

I have exhumed this unusual amplifier based on a patented idea: "constant power amplifier" by Nguyen Tan Tai:
Electronic power amplifier for delivering a constant power into a load impedance - United States Patent 4095189

Claims are no global feedback, load invariant output power, unexpected reproduction quality, and tube-like sound.
It is claimed that fifteen(!) 8Ω series-connected speakers do not alter the acoustic power.

I leave you to judge.....

Have fun!
great!
do you think it will work with modern output transistors without tweaking?
regards
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Old 8th April 2013, 07:18 AM   #3
Mooly is offline Mooly  United Kingdom
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Class B (do we allow it a few milliamps for good measure)... 2N3055/2955... no gfb... sounds tube like.

Have you run a sim Elvee ?
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Old 8th April 2013, 08:07 AM   #4
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by Mooly View Post
sounds tube like.

Have you run a sim Elvee ?
Yeah, I have run a sim, but I haven't disclosed the results yet, as I wanted to hear unbiased opinions first
The THD figure shows that it definitely sounds tube-like, and even overdoes it by quite a bit
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Old 8th April 2013, 08:59 AM   #5
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Originally Posted by Elvee View Post
The THD figure shows that it definitely sounds tube-like, and even overdoes it by quite a bit
so bad?
I like this circuit
could you pickup asc file?
thank you in advance
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Old 8th April 2013, 09:30 AM   #6
JMFahey is offline JMFahey  Argentina
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Quote:
It is claimed that fifteen(!) 8Ω series-connected speakers do not alter the acoustic power.
That's impossible.

EDIT: To be more precise: what's shown is a reasonable conventional poweramp.

Let's not forget that an amplifier can be seen as an audio modulated "valve" between the PSU and the speaker.

The amplifier will not create power which was not available at the PSU first.

Won't supply voltage higher than the rail(s) so when you rise load impedance you soon hit the rails, and can't supply current higher than what's available, so that quickly limits power into lower impedances, besides increasing losses in a horrible way.

That's why amplifiers have a rated "optimum" impedance; as an example 8 ohms, and can deliver reasonable power into 2X and 1/2X that (16 or 4 ohms) but to claim you can raise impedance 15X and keep power *constant* is ludicrous.

To be even more precise: that can be done, of course, with a multitapped output transformer .... but none such is to be seen at that schematic

Last edited by JMFahey; 8th April 2013 at 09:43 AM.
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Old 8th April 2013, 10:08 AM   #7
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by padamiecki View Post
so bad?
I like this circuit
could you pickup asc file?
thank you in advance
You asked for it, here it is, but be warned: it is a real stinker!
First, maximum output before clipping (sort of), and THD
Second the clipping (sort of) behavior (yes, it happens as soon as ~14Vpp, and I have corrected some resistor values otherwise it is still worse)
Third the temperature stability (or instability rather) of the Iq and output offset.

I forgot to mention: the -3dB small signal frequency response is .... 14KHz! Really tube-like!
Attached Images
File Type: png NguyenTT.png (201.8 KB, 444 views)
File Type: png NguyenTT2.png (164.3 KB, 395 views)
File Type: png NguyenTT3.png (162.8 KB, 384 views)
Attached Files
File Type: asc NguyenTT.asc (7.6 KB, 9 views)
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Old 8th April 2013, 10:26 AM   #8
Bonsai is offline Bonsai  Taiwan
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I have exhumed this unusual amplifier based on a patented idea: "constant power amplifier" by Nguyen Tan Tai:
Electronic power amplifier for delivering a constant power into a load impedance - United States Patent 4095189""

OK - you can bury it again!
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Old 8th April 2013, 10:45 AM   #9
Mooly is offline Mooly  United Kingdom
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Thanks Elvee.

So there's wiggle room for slight improvement then
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Old 8th April 2013, 11:28 AM   #10
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Quote:
Originally Posted by Elvee View Post
You asked for it, here it is, but be warned: it is a real stinker!
First, maximum output before clipping (sort of), and THD
Second the clipping (sort of) behavior (yes, it happens as soon as ~14Vpp, and I have corrected some resistor values otherwise it is still worse)
Third the temperature stability (or instability rather) of the Iq and output offset.

I forgot to mention: the -3dB small signal frequency response is .... 14KHz! Really tube-like!
Thank you Elvee!
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