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Old 5th October 2009, 09:01 PM   #161
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An ignorant who assumes to be ignorant is actually one step away from being one.

Sorry for off-topic again.

I found the circlotron related posts quite interesting. How about opening a separate thread? Mike?
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Old 5th October 2009, 09:13 PM   #162
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Ejam has a thread open.

We could try there.
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Old 5th October 2009, 09:34 PM   #163
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Thanks for the info!
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Old 5th October 2009, 10:43 PM   #164
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Quote:
Originally Posted by tryonziess View Post
The circlotron is indeed a very nice application of analog electronics, but how good is it at replicating our music. It does fit the simple is better category. Is it particularly effecient?
Pretty much the same efficiency as everything else. The
value of the circlotron in my mind is the ability to get good
direct coupled push-pull operation from matched parts of the
same polarity. After spending more than usual on the extra
supply components, that is.

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Old 6th October 2009, 09:21 AM   #165
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Quote:
Originally Posted by Floyd42Flake View Post
An ignorant who assumes to be ignorant is actually one step away from being one.
I just realize that this could be easily misread. I meant: "...is actually quite far away from being one."
Sorry, the language barrier!
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Old 6th October 2009, 10:16 AM   #166
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Quote:
Originally Posted by Nelson Pass View Post
The
value of the circlotron in my mind is the ability to get good
direct coupled push-pull operation from matched parts of the
same polarity.
This is probably an old hat in solid state push pull circuitry: In my F5 project I selected the IRFP240s and IRFP9240s for low distortion (a friend helped me, he owns a distortion analyzer - lucky fellow!), because I wanted to try out a few dB less feedback in the circuit. The prints of the distortion curves between the two different Fets were not that similar than I had expected.
I wondered, if this inequality might slightly damage the sound. Maybe in a way of a marginally less relaxed presentation.
Don't get me wrong, I don't hear the fleas coughing (as we say in Germany), it's just speculation.
Could this be another advantage of a circlotron?

P.S. I consider a circlotron as a three-dimensional Möbius strip, but maybe I'm just too romantic...
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Old 6th October 2009, 10:24 AM   #167
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Nelson,
Would it be possible to use the Semisouth silicon carbide high voltage jfet in the frontend of the amplifier to allow higher overall rail voltages. Have they got the required specs for the differentials and drive units. If the Semisouth part replaced the Loveltech the amp would be considerable less fragile. You could then dispense with the cascode element and simplifiy the circuit. I need very simple these days. The datasheet states very low initial gate voltage and very high effeciency.
I doubt I will ever figure out how all of this stuff works. However, most of my amps turn out smokeless. That is most not all. I have to check everything a dozen times before I power up. The J2 seems to be a good choice for direct drive on a ribbon.

Tad
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Old 6th October 2009, 10:51 PM   #168
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I think the SemiSouth devices belong in the output stage.
Using them elsewhere would be like using a cannon to shoot
flies.

If you are concerned about the voltage on the front end JFETs,
I suggest you cascode them. It's easy to do, works like glue,
and there are lots of examples to follow.

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Old 6th October 2009, 10:56 PM   #169
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Quote:
Originally Posted by Floyd42Flake View Post
In my F5 project I selected the IRFP240s and IRFP9240s for low distortion
The IR P channel parts have higher distortion. You could use
the Fairchilds, or take a look at Toshiba or Harris (if you can
find them).

The N vs P channel mismatch is a small source of distortion
down around a watt or so, which is why you want to be
able to trim the Mosfet Source resistors values a bit (if you
have the analyzer handy). Also, it is effective to use a
couple hundred ohm pot, wiper grounded, connected across
the Sources of the input JFETs and trim for least distortion at
1 watt.

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Old 8th October 2009, 07:58 AM   #170
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The J2 schematic in the 6moons article used parallel fets ins the current source and the diff. amp. Did you use it to lower the noise floor, or was it due to drive requirement???

What is the advantage compared to this topology:

Single fet diff amp, cascoded with small bipolar devices, diff amp build with led/bippolar current source instead of jfet.

Mosfet source follower, to deliver drive current.

Rest: As is.
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