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Old 16th April 2010, 09:43 PM   #11
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Quote:
Originally Posted by mjf View Post
QUOTE=tiefbassuebertr BTW this amp was my first amplifier project (arround 1976). It was a amp kit from Oppermann electronic include PCB
hello.
found something.........
Exactly - the 20W EDWIN
Unfortunately it was stolen from me during the time in the military (the closed locker, where the amp was stored at the weekend, was screwed from behind). So I cannot make a soundcheck and comparable test with today's amp projects

Apexaudio: this is a normal Class AB amp; R9 can replace with a variable resistor.
Curious is the not presently emitter resistor, so that the cross current through T1 was only the base input current of T2 (only uA aera - hugh design failure and main reason for bad sound !!!).

Last edited by tiefbassuebertr; 16th April 2010 at 09:50 PM.
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Old 16th April 2010, 11:14 PM   #12
wahab is offline wahab  Algeria
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Quote:
Originally Posted by tiefbassuebertr View Post
Exactly - the 20W EDWIN
Unfortunately it was stolen from me during the time in the military (the closed locker, where the amp was stored at the weekend, was screwed from behind). So I cannot make a soundcheck and comparable test with today's amp projects
.
Not a big loss, anyway...
This elektor amp is a complete failure on its own.
Fortunately, they much improved their designs the
following years..
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Old 16th April 2010, 11:31 PM   #13
Bonsai is offline Bonsai  Taiwan
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Very interesting to look at those old designs. Anyone got a copy of the Elektor 'Equa' amplifier. I looked on the web - no luck. Its from about 1975 or 1976.

thanks
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Last edited by Bonsai; 16th April 2010 at 11:34 PM.
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Old 16th April 2010, 11:43 PM   #14
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Quote:
Originally Posted by Bonsai View Post
Very interesting to look at those old designs. Anyone got a copy of the Elektor 'Equa' amplifier. I looked on the web - no luck. Its from about 1975 or 1976.

thanks
I have 'Equa' in JPG format, but not on English (Serbian)
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Old 17th April 2010, 07:49 AM   #15
Elvee is online now Elvee  Belgium
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Quote:
Originally Posted by wahab View Post
Not a big loss, anyway...
This elektor amp is a complete failure on its own.
Fortunately, they much improved their designs the
following years..
Indeed.
This kind of amplifier is basically a square wheel made to (sort of) work.
But when you look into the details, you understand immediately they're hopelessly flawed.
Here is the residue appearing between the inputs of the diff amp:

It says more than a thousand words.
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File Type: gif Edwin.gif (40.9 KB, 805 views)
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Old 17th April 2010, 07:56 AM   #16
mjf is offline mjf  Austria
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hello.
i think this was the equa amp.......(i am not shure)
(could be published in elektor dezember 1972)
Attached Images
File Type: jpg equa1.JPG (193.4 KB, 833 views)

Last edited by mjf; 17th April 2010 at 08:14 AM.
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Old 17th April 2010, 09:15 AM   #17
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Quote:
Originally Posted by Elvee View Post
Indeed. This kind of amplifier is basically a square wheel made to (sort of) work. But when you look into the details, you understand immediately they're hopelessly flawed. Here is the residue appearing between the inputs of the diff amp (see waveform previous post): it says more than a thousand words.
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 ?
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Old 17th April 2010, 09:39 AM   #18
wahab is offline wahab  Algeria
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Originally Posted by steph_tsf View Post
Hello, it is not a flaw, it is a feature ! One may learn something, listening to such "flawed" amp ..
A feature ?...Perhaps for a guitar amp overdrive function...
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File Type: zip ELEKTOR EDWIN 10khz sine.zip (10.4 KB, 161 views)
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Old 17th April 2010, 09:59 AM   #19
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Quote:
Originally Posted by wahab;2156394 from post #12
Not a big loss, anyway...
This elektor amp is a complete failure on its own.
Fortunately, they much improved their designs the
following years..
Bonsai post #13:
Very interesting to look at those old designs. Anyone got a copy of the Elektor 'Equa' amplifier. I looked on the web - no luck. Its from about 1975 or 1976.
From the view of the real value here of course not, but from the view of the sentimental value, since even a lot of work has been invested for the enclosure resp. cabinet (also a FM Stereo Kit (FD1A/uA703/CA3189/MC1310P) was integrated).
From this amp I have win an auction from the concerning elektor magazine last year. I have build this amp, but I get an oscillator. The reason is the topology of the output stage. Also in the Pspice simulaion I observe the same oscillation effect

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.
Until this day I haven't found a satisfy solution to remove the reason for the oscillation (except the use of the normal two stage buffer, i. e. darlington for the pos. half and sziklai darlington for the neg. half
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Old 17th April 2010, 10:12 AM   #20
wahab is offline wahab  Algeria
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Everything is flawed , from the input to the output..
To make it work correctly, here s some mods to implement,
but still, the amp would remain a mediocre one, although
not the worse one either..
Attached Files
File Type: zip ELEKTOR EDWIN modded.zip (5.9 KB, 260 views)

Last edited by wahab; 17th April 2010 at 10:16 AM.
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