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The AMNESIS amp: a good amplifier, like a gentleman, has no memory.
The AMNESIS amp: a good amplifier, like a gentleman, has no memory.
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Old 14th May 2018, 12:11 PM   #71
maxlorenz is online now maxlorenz  Chile
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Ah! The joy of having a stable circuit!

Doesn't come that often...

Adding C9 -C11 (1uF) to the real 32V amp made it very unstable: just tapping the FB trace induced 0,5V oscillation about 800Kz, SVPT-like waveform...
With just resistors shall be then.

Returning the common-base bias to ground or to output does not seem to alter sound...pity, I was hopping for some magical effect, like Shade.

Cheers,
M.
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Old 14th May 2018, 06:17 PM   #72
maxlorenz is online now maxlorenz  Chile
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Quote:
Originally Posted by maxlorenz View Post
I always wanted to try this crazy thing: a common-base buffer for the output of the input section.
This mod accentuates a ringing that I discovered at the output of the differential amplifier. I reduced one of the R of the CFP from 1k to 600 as this shares better the current for both the BJTs and the ringing disappeared.

BTW, I modded the output section to a, IMHO, more technically correct configuration, with a small degeneration R for the driver of the output CFP and the collector of the driven directly connected to output.

As it is, it makes nice curves.
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Old 16th May 2018, 12:43 PM   #73
maxlorenz is online now maxlorenz  Chile
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I forgot to post pictures of the actual amp. These are of a previous iteration, sans emitter's R for the cascodying CFP BJTs and with original input filter.
Note my tweak for speaker binding posts.

Also, the power supply is a "charge-transfer supply", from -ECdesigns.

I just can't build something without introducing my mods...Aquarius rising

Cheers,
M.
Attached Images
File Type: png AMNESIS CFPCFP.png (897.0 KB, 153 views)
File Type: png AMNESIS CFPCFP2.png (738.1 KB, 148 views)
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Old 16th May 2018, 01:21 PM   #74
jameshillj is offline jameshillj  Australia
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Hi Max, It's been awhile - you doing okay?

I see you're having some fun with this one - nothing like keeping busy, eh!

How have you implemented the "charge-transfer supply" - I've forgotten about this one of John's - is it an improvement?
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Old 16th May 2018, 04:08 PM   #75
maxlorenz is online now maxlorenz  Chile
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Hi dear,

How sunny is down there in this season?

Here we had 2°Celsius today and I have my Amnesis in the patio where my "shop" is relegated by a superior power, hehe.

My Amnesis is a joy to listen to (when stable) with instant relaxation and musical bliss. I know I put myself between the horses legs with this output configuration but it is worth every effort. I did not found yet this one descibed...maybe I will get the authorship

The charge transfer does improve sound. It still has ground connection in common. I increase values of active and passive elements for a High Power circuit, since the original is for low power.

I'll permit myself to re-post the explanation -EC- posted on his "TDA1541A" thread:
Quote:
> First the primary smoothing cap (Cp) is charged with the polluted rectified voltage through D1 ... D3. R1 puts a positive voltage on P-FET T1, switching it OFF, and disconnecting the load during this charge cycle.

All interference surges through the primary smoothing cap -not the connected load- The severety of the pollution really doesn't matter at this point, main purpose is to get the primary smoothing cap Cp charged.

> Next the rectified voltage drops below the voltage across the smoothing cap Cp plus voltage drop across the rectifier diodes D1 & D3 or D2 & D3, now the rectifier diode no longer conducts, and interrupts the noisy charge current. All that remains after this interference attack is a charged capacitor. The P-MOSFET is not yet switched-on as -Vgs is still too low to make it conduct.

Now we have a floating charged cap (Cp), it's basically similar to a battery connected to GND with the minus terminal. Needless to say that all the interference signals during charging are not "remembered" by capacitor Cp.

> As the sinewave voltage drops, P-channel MOSFET -Vgs gets high enough, and T1 switches-ON. T1 now connects charged cap Cp to both Cs and load, the charge of the primary smoothing cap supplies clean energy to both Cs and load.

> After the sinewave voltage rises again, -Vgs drops and T1 is switched OFF. Now the secondary smoothing cap Cs continues to supply clean electrical energy to the load.

The cycle is repeated 50/60 times a second with half-wave rectifiers, and 100/120 times a second with full-wave rectifiers.

Both D4 and D5 (Zener diode and Schottky diode) are added for protecting the gate of T1.

D3 was added to create the required switching signal for T1. T1 is switched-on by pulling the gate to GND through both R1 and R2, the protection diodes D4 and D5 will limit -Vgs. T1 is switched off by pulling the gate to plus through R1.

The peak charge transfer current through Cs is limited by the P-MOSFET RdsON, but can be further manipulated by adding an extra series resistor in the drain lead.
I hope you like it.

Take care and have fun, my friend.
M.

PS: the regulator part T2 is optional...I don't use it.
Attached Images
File Type: jpg charge transfer PS N y P.jpg (75.2 KB, 144 views)

Last edited by maxlorenz; 16th May 2018 at 04:11 PM.
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Old 16th May 2018, 04:32 PM   #76
padamiecki is offline padamiecki  Poland
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Hi Max!
I am watching your efforts with the interest,
but the power supply for dac is interesting too, please provide a link to 1541 thread,
thank you in advance!
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regards, Pawel
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Old 16th May 2018, 04:43 PM   #77
maxlorenz is online now maxlorenz  Chile
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Quote:
Originally Posted by padamiecki View Post
Hi Max!
I am watching your efforts with the interest,
but the power supply for dac is interesting too, please provide a link to 1541 thread,
thank you in advance!
OK. Thank you.
So we are two interested people in this revolutionary amp .

Building the ultimate NOS DAC using TDA1541A

John just posted a novel DAC with simultaneous mode input configuration. A great contribution to DIY, since he is also commited to his great Mosaic DAC invention.

Search for "charge transfer supply" in the above configuration and in "floating" configuration, which doubles output V. I usually put some good quality ferrites in the ground leads of DACs.

My main system n°1 and n°2 are connected to balanced power.

Cheers,
M.
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File Type: jpg floating CHARGE TRANSFER.jpg (46.6 KB, 102 views)

Last edited by maxlorenz; 16th May 2018 at 04:48 PM.
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Old 16th May 2018, 05:02 PM   #78
maxlorenz is online now maxlorenz  Chile
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This one is good. I tried until 590mV/-560mv bias from base to ground of output elements.
It is very enlighting to see the wave forms on the cascodying CFPs...maybe over-damped.

I have also cascoded VAS and CCS which I will try to convert to Hawksford...
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Old 16th May 2018, 06:08 PM   #79
maxlorenz is online now maxlorenz  Chile
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Revisiting the diff out buffer idea with, what I suppose to be, Hawksford Cascoded VAS, produced no oscillation of the diff output, though slight distortion may be seen. In -ECdesigns-' diffamp harmonic distortion can be reduced with trimmer pot in degeneration resistors for the emmiter input pair...

I reached the best sine for the output node of the cascodyingCFP. The black arrows shows the tester point. I may have something here...

I was looking for oscillation to test Bimo's idea of stopper R in gates of the input JFETs (cascodying)...

PS: bias may be too high. Increase R24 to 1K1.

Last edited by maxlorenz; 16th May 2018 at 06:22 PM.
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Old 19th May 2018, 03:18 PM   #80
maxlorenz is online now maxlorenz  Chile
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Hi.

Lots of new insight since I learned the FTT function from LTspice (BTW LTspice freezes 9/10 times and it is a pain to use...or maybe the PC is to blame) and by reading newly found articles by "Le Feu Seigneur de Lavardin, Hephaïstos", one of my heroes The guy, which was a French EE (BTW, mchambin) and more intelligent than I am, used a cascode INSIDE the output Siklay pair in one of his amps, while I use it OUTSIDE the CFP. Very clever indeed. I suppose that would make the amp more stable or less temperamental. He cascoded only the driver BJT but you know me by now, I will also cascode the complementary BJT (CFP inside CFP), somehow...I will find the way.

L'étage de sortie de l'ampli -1- réflexions théoriques (Héphaïtos)

I now feel that the CFP, while driven as an emitter follower, behaves more like a common-emitter, soundwise and from a (un)stability PoV... and, the pre-drivers probably must be connected to the output also...

Wish me luck.
M.
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