OPA-Earth & OPA-Sun, Discrete Opamp diy kits

[lineup]

What do you people think of
OPA-Earth & OPA-Sun discrete opamps
by member audio-gd

The test results published looks alright.
Are they anything to consider, in place of Audio IC Opamps.
For example OPA2134, AD797, LM4562, AD827 and LME49710, LME49870.
Schematics, Info & Prices. Link.
http://www.audio-gd.com/enweb/pro/diy/OPA.htm

We have some very good alternative Discrete Op-Amps suggestions
by The Master Nelson Pass here:
http://www.passdiy.com/pdf/diyopamp.pdf

I have too, published a number of similar discrete Class A OpAmps.
For voltages between +-15 to +-50 Volt ( 30-100 Volt total Supply).


Lineup - Discrete Op-Amp projects

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[KSTR]

What I don't like about them (Sun & Earth) is that one of them seems to be 1:1 copy of another commercial discrete opamp replacement, the Burson amp (or vice versa, which appears to be rather unlikely, but I just don't know). There is a thread about the Burson amp here where schematics are shown (and some measurement), from a french forum.
Voltage Differential Amplification
(see first dozen of replies).

- Klaus

[scott wurcer]

Op-amps don't have a ground pin .

At least one of those schematics has a "ground" connection that is definately not optional.

[Franz Gysi]

Hello

Last weekend, another diyaudio member told me the first time about this opamps.

I was really impressed.

But now, knowing this are some copies, makes me unhappy

Next weekend, the diyaudio member will visit me, bringing in some of this opamps.

And some of the mysterious DY2000 (AD823 in another package? Really an Analog Device Product?).

I have the opportunity, to use a professional audio analyzer, the PrismSound DScope III http://www.prismsound.com/test_measu...scope_home.php

And I have the intention, to do some tests, in comparison with another good opamps.

I am really open for every suggestion, what measurement in wich configuration (gain, input impedance, inverting/noninverting) would be of interest.

Please post your suggestions/wishlist here.

And I will post the results.

Kind regards
Franz

[analog_sa]

Originally posted by Franz Gysi
I am really open for every suggestion, what measurement in wich configuration (gain, input impedance, inverting/noninverting) would be of interest.

How 'bout just listening? None of the known measurable parameters bear any relation to perceived sound. Which you probably know anyway.

[syn08]

Originally posted by analog_sa
None of the known measurable parameters bear any relation to perceived sound.

Yeah, right
The grapes are sour anyway!

[KSTR]

Originally posted by analog_sa
None of the known measurable parameters bear any relation to perceived sound.

Probably you should make yourself familiar with the work of Earl Geddes in this field, and especially make sure to read this paper by de Santis / Henin to update your position:
http://projekter.aau.dk/projekter/fb...061_Thesis.pdf

- Klaus

[KSTR]

Originally posted by Franz Gysi
I am really open for every suggestion, what measurement in wich configuration (gain, input impedance, inverting/noninverting) would be of interest.

Maybe the recent excellent work of your fellow countryman Samuel Groner is worth to look at in this context:
http://www.sg-acoustics.ch/analogue_...distortion.pdf
Local thread here:
Amazing opamp measurement shoot-out

- Klaus

[analog_sa]

Originally posted by KSTR
Probably you should make yourself familiar with the [/url]

Dear Klaus

Having been interested in audio for a very long time i am certainly aware of your references. And of other similarly bold claims. Pardon my scepticism but none of this is very conclusive. Opamps are relatively easy to test in a bypass test by ear. These specific products may be very nice but their execution and specifically wiring harness is very suspect.

[Gordy]

Originally posted by Franz Gysi

I am really open for every suggestion, what measurement in wich configuration (gain, input impedance, inverting/noninverting) would be of interest.

Please post your suggestions/wishlist here.

And I will post the results.

Kind regards
Franz

My suggestion:

Driving impedance 1... 600 Ohms (to represent typical output Z of a previous stage)

Driving impedance 2... 5000 Ohms (to represent typical output Z of a volume potentiometer)

Load impedance... 10000 Ohms in parallel with 300 pF (to represent typical input Z of an amplifier, plus cable capacitance)

Input level... variable amplitude sine, from 775 mV to 2000 mV (RMS)

Test for...
...harmonic distortion spectrum at 20 Hz, 100 Hz, 1000 Hz and 10000 Hz
...how the distortion spectrum changes with changes in input amplitude
...intermodulation of twin tones (but I am not sure of the frequencies? Many use 19 and 20 kHz)
...phase response (especially of the higher frequencies)
...noise (I think it is best to test this with the input shorted?)
...cross-over distortion (because even just a little seems to make a difference to the sound quality)

Good luck.