opEIGHT: What we know so far

[808eengr]

opEIGHT: What we know so far


90's throwback TMC High Voltage SE Headphone Amplifier using OPA1656


(mosconi-system.it AS 100.4 little broskies w/op-amp)


0.000004%(0.000000%) @1kHz 1VRMS 32R
0.000210%(0.000206%) @48kHz 1VRMS 32R


needs output Zobel RC+R||L
sub ONSemi BD140/BD139, adjust emitter R
model shows 5mV offset

note:

gain + phase very difficult to model in this configuration
use phase of harmonics for verification and freq distribution
model shows 5mV offset

 

[808eengr]

an AC .700 model is suitable for what purpose?


vintage integrated amplifiers....


740-700=


a few more picos

 

[808eengr]

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[808eengr]

how's your guys OPA1656 freq dists looking 😕

 

[808eengr]

changes to R1/R2


back to the future fast


using 296-OPA1656ID-ND


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[808eengr]

strings, pianos, just brilliant

 

[808eengr]

*normalized phase is the component to look at


1kHz 4VRMS 32R


Total Harmonic Distortion: 0.000018%(0.000000%)

 

[808eengr]

opEIGHT.10

using OPA1642


added bootstrap (current sense)
lowered dissipation Q1/Q2 to ~160mW
total idle current 250mA for output stage


@4VRMS 48kHz

Total Harmonic Distortion: 0.004123%(0.004123%)

needs output Zobel RC+R||L
sub ONSemi BD140/BD139, adjust emitter R
model shows 10mV offset

1.6deg/20dB -3dB(~1.4MHz)


bom ~40euro at one unit (sans PCB)


platform for a discrete opamp?
EUVL??

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Attached Files

 

[808eengr]

improved linearity (THD v W)

 

[808eengr]

opEIGHT.10 v.0 (using OPA1642)


added bootstrap (current sense)
* lowered dissipation further Q1/Q2 to ~120mW
* lowered total idle current further ~230mA total for 1 channel output stage (*balanced configuration - 2x pcb - 1 per channel)
* improved output damping circuit

Simulations are all Single Ended
@4VRMS 48kHz 32R
Total Harmonic Distortion: 0.004579%(0.004579%)

@4VRMS 48kHz 125R
Total Harmonic Distortion: 0.000768%(0.000768%)

* model shows 10mV offset
* ~1.4deg/24dB -3dB(~1.4MHz)

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[808eengr]

free the watts!!!!

 

[808eengr]

@4VRMS 1kHz 32R
Total Harmonic Distortion: 0.000102%(0.000000%)


😱

 

[808eengr]

90 euro (2x L+R channel boards) ??


(no opamps included)


:shrugs:

 

[808eengr]

might I suggest the kaneda jfet preamp >

kaneda quasi push pull discrete opamp >

(in this article)
One Last Attempt at Discrete Opamp in DIP8 Footprint

opEIGHT.10 (lower gain v/i converter)

 

[808eengr]

opEIGHT v1.0

opEIGHT v1.0


updates:


60Hz line filter for input stage
54mA bias output transistor
OPA1642 multiple feedback input stage -> OPA1642 composite gain stage


some 8VRMS numbers....

 

[808eengr]

:avalanche:

 

[808eengr]

I think it was a comparator....

 

[808eengr]

Still waiting for some useful explanation other than misery loves company

 

[808eengr]

Tune up your ZCD

 

[abstract]

What happens if you add a speaker model that reflects delayed energy back into the feedback circuit, adding positive feedback at a range of frequencies depending on the phase shift?