circlotron revisted

For the three and more legged things
SimonC
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#16

Post by SimonC »

Mike H wrote:What I find particular interesting about this is that it appears to be basically the old push-pull transistor amp type of thing, where the supply is centre-tapped and the speaker negative goes to that. The main difference being this version seems to run at high current all the time, or is that not right?
The high current is to get the fets up into their linear operating region, its been a shift in thinking to work in terms of current rather than voltage bias.

I don't think its quite the same as the push-pull in that both the supplies are floating and there's no common 'negative' return path, its more 2 floating bridges pushing against each other. Michael's info on Nelson's website gives a really nice explanation of how it all works (much better than I can).

I'd be interested in seeing a couple of the push-pull circuits as they may be the same idea in a different package, always something new (or old) to learn.

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Mike H
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#17

Post by Mike H »

Yes okay, it's kind of like two power supply regulators using the speaker as load.

I was trying to find an example circuit of a transistor push-pull amp but can't ~ anyway the method I was thinking of is two positive and negative supplies connected to a 0V rail, then each o/p transistors puts each polarity across the load as necessary.
 
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SimonC
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#18

Post by SimonC »

Got it 90% rebuilt last night as the 'antimatter' version with my shiny new LSK389's. Should be finished, along with hacking the DAC to get balanced outputs, at the weekend. Only thing stopping me now is that is damm cold working in the cellar at the mo...

Will post some photo's etc if I get chance.

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Dave the bass
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#19

Post by Dave the bass »

Valve amp in the cellar to keep you warm?

Top tip that :wink: :lol:

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#20

Post by SimonC »

Dave the bass wrote:Valve amp in the cellar to keep you warm?

Top tip that :wink: :lol:

DTB
That was the plan with the 6c33, but this one should be a pretty good room heater once it gets going. I've even fitted a fan to the heatsink ready :wink:
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Mike H
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#21

Post by Mike H »

How about a fan heater in the interim? Pretty good them
 
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#22

Post by SimonC »

It lives :)

Bias adjustment now does what it says on the tin, almost...

Still got some small stabilty problems to iron out before I hook it up to a set of speakers. The bias drifts around more than I'd like, but its cyclic and affects both bridges almost equally. Seems to be temperature related, its got the 'feel' of something heating and cooling (20-30 seconds per cycle and affecting both bridges).

Might try some heat shielding on the bias circuits, gut feeeling is that the new LSK's are very sensitive to their surroundings...onwards

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Mike H
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#23

Post by Mike H »

Is 'circlotron' right, or should it be 'cyclotron'? Image
 
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#24

Post by IslandPink »

I don't think most of us have the space or funds to run a cyclotron .

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Nick
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#25

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Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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#26

Post by IslandPink »

Somehow I knew , just as I posted that message, that I was leaving myself exposed .....

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Mike H
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#27

Post by Mike H »

Oh-kay...

A quote from Elektor's projects book:

"Fig. 1-46. The Cyclotron amplifier designed by Zechendorff is one of the many variants of the PPP amplifier, well-known in Europe in the mid 1950s. Note the cross-wise coupled input stage which makes the amplifier truly symmetrical."

Image

Either they're talking cobblers, or it is mis-translated from actual 'circlotron' or it's a 'project name'

Edit
Or Zechendorff liked the sound of 'cyclotron' and wanted it for his amp design.
 
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Dave the bass
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#28

Post by Dave the bass »

I'm posting on this thread as I think the Circlotron discussion on MrI's OTL thread belongs here, hope thats OK with Ed and MrI.

Following from a link Ed posted I found and read throgh this, it's made things a bit clearer -> http://www.angelfire.com/electronic/fun ... otron.html

The author implies that the 'amp' actually isn't an amp! It's like a very big CF in that it doesn't have any gain as such, if I've read it correctly the final stage itself in his amp requires a massive phase-split driving signal voltage.

That got me thinking (which is a good thing), has anyone tried a interstage TX to drive a Circlotron? that could provide signals 180 degree's apart at high voltage couldn't it?

Also of note is that this particular circlotron cct uses an op tx.

Interesting stuff all this.

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Nick
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#29

Post by Nick »

Yes, the early designs used output transformers. Its only the interest in OTL's that have brought it back. I also think a interstage would be the obvious way of driving itr, but sort of goes against the "transformers bad" idea :-).

The large voltage swing isnt that much of a problem for a OTL, you just need the driver to swing as much voltage as you want to appear across your speakers. If the idea of a stage without gain makes you question its a amplifier, think of it as a impedance converter instead.
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Mike H
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#30

Post by Mike H »

Dave the bass wrote:That got me thinking (which is a good thing), has anyone tried a interstage TX to drive a Circlotron?

Not that I know of but I want to. Also and as well as, although as you say the o/p's are basically CF, with current gain only, using a interstage will mean it will do Voltage gain as well 'cause all the valve will know about is what is put across its cathode and grid, if you think about it that means the driver Voltage is not the same as the final Voltage to the load, it's only the grid Voltage!

Cunning no? :lol:

Somewhere got an Elektor circuit, it's got a complicated driver cos it has to do the whole primary Voltage for the o/p transformer. It's got EL34's but they just work as big CF's, all the Voltage swing has got to come from the driver.


 
 
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