Edwin 20 watt (Elektor 1970 - May)

[mjf]

[QUOTE=tiefbassuebertr;
The output stage should be an improved topology (with respect to the symmetry between the positive and half negative half) compared with those from the Quad 303.

hello.
the elektor equin amp uses an outputstage similar to the quad 303
(published dez.75 and jan.76)............
transl.:
der equin amp hat eine leicht verbesserte version der quad 303 ausgangstufe

 

[tiefbassuebertr]

hello, the elektor equin amp uses an outputstage similar to the quad 303
(published dez.75 and jan.76)............
transl.:
der equin amp hat eine leicht verbesserte version der quad 303 ausgangstufe

ckeck out post 21 about
http://www.diyaudio.com/forums/solid-state/113943-quad-303-triple-cascade.html
in the attachement the EQIUN output buffer

Basic idea of the Edwin topology is actually, the choice of a high idle current through the first stage of the darlington buffer (emitter resistor therefore only 5-10 ohms). Thus the bias voltage spread can be have larger acceptable tolerances. Consequently I don't need a variable resistor for idle current adjust.
Some guys think now (even today), because the first stage of the darlington buffer runs in class A, the not present idle current through the output stage pair (Class-B) have no audible effects.

 

[Elvee]

Hello, it is not a flaw, it is a feature ! By the way, I am now including the test you've done (voltage on the diff amp), as routine health check. Thanks ! I agree with you that if music is supposed to be delivered by such an amplifier, the tiny variations around the zero may be ignored, masked, erased while the amp is so heavily busy, eliminating the crossover distorsion. Kind of window opening and closing at each crossing. One may learn something, listening to such "flawed" amp ... Don't you think ?

Even tiny amounts of this kind of distortion is definitely unpleasant.
Note that the amplitude of the residue is 1/20th of its actual value at the output.

Adding a fourth diode in the string (MURS120) brings the Iq to ~25mA, and the residue looks like this:

What remains is a pure signal, resulting from the finite OL gain of the amplifier

 

[tiefbassuebertr]

here the english Elektor version:
"EQUIN" Elektor Vol. 2, No. 4, pp.448-453, April 1976
found about the publication ref. by
Stabilized rail-to-rail speaker driver circuit

and here a pic of the orig. EDWIN (see attachement) and a supplier of an EDWIN-II kit + publication of article:
Walter Elektronik - Fachgeschft fr Elektronik und Hifi in Mannheim
http://www.eveliensnel.nl/blog/index.php/2008/11/audio-2.html

 

[Bonsai]

hello.
i think this was the equa amp.......(i am not shure)
(could be published in elektor dezember 1972)

Yes that's it. I etched and built mine on the PCB design Elektor published around 1975 or 1976. I sprayed the PCB black. But, my skills were not too good in those days and the thing hummed like hell.

About 2 or 3 years later I built an ETI amp and replaced the TIP output devices with MJ802 and MJ14 (? can not remember). I had that amp right up until about 2003 - I got the wiring right in that one - it was really quiet.

Thanks for posting BTW - appreciate it.

 

[steph_tsf]

hello,

attached you will find genuine info about the early Edwin implementations in Elektor DE (german edition) :

- 20 Watt in May 1970, with the addendum published in Sept Oct 1970
- 100 Watt in January 1971
- 40 Watt in Mai 1971

My preference goes to the 20 Watt and the 100 Watt versions. If you own one, please keep it ! The 40 watt schematic lacks spirit. Personal opinion.

Cheers,
Steph

 

[tiefbassuebertr]

Which amplifier topologies similar to this are to find in the other world's electronic magazines at those days
(outside the English/German/Dutch speaking area) ??
Check out in this case this thread:
http://www.diyaudio.com/forums/soli...ble-electr-audio-magazines-2.html#post2671316

 

[tiefbassuebertr]

an similar topology, also without adjusting elements for output buffer's idle current:
Audio 300W Power Amplifier OCL Circuit | Audio Circuits

 

[lineup]

Nice thread.

 

[tiefbassuebertr]

Who want to have German's Elektor Magazine from 1971 until 2009 nearly complete

I'm going to sell my collection of the magazine "Elektor" in German language.

Go therefore to ebay item No 321071826152

Here some informations in english:

Follow issues I miss (not available):
1) 1970: all issues
2) 1971: all issues except No. 13 (december 1971)
3) 1972: issue No. 15, 17, 18 and 24 (2/72, 4/72, 5/72 und 11/72)

because of the weight no shipping, only pick up.
phone for additional questions:
+49-6765-949734
+49-177-7282258

 

[tiefbassuebertr]

an similar topology, also without adjusting elements for output buffer's idle current:
Audio 300W Power Amplifier OCL Circuit | Audio Circuits

The URL is death. Currently URL is follow:
300W Power Amplifier OCL Circuit |AUDIO AMPLIFIER SCHEMATIC CIRCUITS PICTURE