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destroyer X 7th November 2008 10:01 PM

A forum friend has sent me this Class A created in 1967
2 Attachment(s)

I have just simulated, not happy with the 1 Kilohertz square wave.

What do you think about this amplifier?

Have suggestions to improve?..... if positive post them here.

Would you make it different?..... how?



destroyer X 7th November 2008 10:08 PM

Another image...more complete.
2 Attachment(s)

The amplifier uses three supplies...all them common ground.

First supply is a low power one.... 40 volts and ground.

More two supplies, with NO common ground... each one of them with 28 volts or something around that.

You have off set adjustment and iddle current adjustment.

Observe the speaker goes to both 28 volts supply, it is connected into the negative side of those supplies.

Off course, the output power depends the current you adjust...with 800 miliamperes plus 800 miliamperes you may have more than 10 watts...but you can increase to 2 amperes or a little bit more and will have around 30 watts or more. (if your transistor survive to more than 56 watts each one ( i have my doubts a single transistor can do this job)

Seems it goes flat from 1 hertz to more than 100 kilohertz... sinus was fine..but low power and low frequencies square wave was strange.

destroyer X 7th November 2008 10:09 PM

Yes, i have simulated..but have not assembled
2 Attachment(s)

Will be more happy listening your evaluations.



destroyer X 7th November 2008 10:10 PM

Here is the 1 Kilohertz square wave...power was low...not more than 3 watts RMS
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darkfenriz 8th November 2008 06:32 AM

This is circlotron output amp designed for germanium transistors.
I would build something more up to date, with mosfets output if you want circlotron.

Just my opinion


destroyer X 8th November 2008 08:59 AM

Yes.... i have tried Circlotron using Fets... i have assembled
2 Attachment(s)

And was interesting, at least different.... mine had not a very good sound... only good, was strange... seems something was missed into the wave shape.... i had not observed into scope..but it seems to me strange things should appear there, alike positive half cicle bigger than negative half cicle.... you know, sounded strange.

Sounded as something stucked.... a plumbing blocked to watter flow...the audio did not gone outside the speaker... sounded not very good... bass was poor, weak and not tigth... treble was reasonable but had not high end... was not clear the higher frequencies.... played loud... too much loud... a screaming thing.

This one was not assembled... already thinking about, and as the thread is going almost empty, seems the circuit is not something to have great hopes.... no one suggested modifications, no one said has assembled, no testimony of superior performance... the circuit seems weak into our community evaluation.

I have build the one attached.



revintage 8th November 2008 09:14 AM

Hi Carlos,
Do you have the complete article?

destroyer X 8th November 2008 09:22 AM

No!... i have not i would be happy to have it

I have made the Circlotron.... finally i was not happy with it...but sounded fine.... strange but fine....not very good.... maximum i could say is good..... sligtly better than average amplifiers.... had something a little bit better related presence.... related reality into mid ranges.

I just cannot resist.... i was pisted with class A...but curiosity is the hell of my life... down here some Circlotron small movies uploaded to youtube:

My E mail adress is:

Send me the complete article.... i have problems to read in German... English, Spanish, Italian and French are not problem to me... and Portuguese is my native mother no problem also with portuguese too.


destroyer X 8th November 2008 09:36 AM

The one have sent me was Pierre Robertson

seems to me he may be Canadien....internet provider is "doglet".

I have answered his mail in French and he said despite his name is Pierre, his language is English (Anglais should be better to someone named Pierre).

Well...names sometimes are portuguese we have names we do not know if they are male or female (Jocelyn)

This remembers me.... always..... Johnny Cash, with the music he say:

- "My name is sue! do you do!"

Now people is using Emily here.... Emilia in portuguese... strange to use Emily here..... seems alike Pierre beeing used in Germany...there we spect, Hans, Klaus, Herbert, Frank, Egon, Schultz, Hermann...never Pierre!


Mooly 8th November 2008 10:20 AM

It's great looking at old circuits.
Maybe the original transistors are part of "what makes this beastie tick". Some of those old Germaniums cut off at 500 Khz or so. It may rely on those characteristics ft vbe etc.

Once had circuit from 1967 for Class D discrete amp -- amazing what went on back then.
There's nothing new :)

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