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Old 9th January 2006, 03:36 PM   #1
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Default Hot Follower 99

I stumbled across this design by Andrea Ciuffoli . Does this type of design require a good voltage source (BOZ or something else?) like the Power Follower 99c. It looks like a fairly straight forward design, just couldnt find too much info about it. The 2SC3264/2SA1295 seem a little harder to procure.
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Old 9th January 2006, 05:50 PM   #2
marziom is offline marziom  Italy
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if you are interested i build the power follower...

marzio
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Old 9th January 2006, 11:10 PM   #3
anatech is offline anatech  Canada
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Not an original design really. Still fighting with my implementation.

You will have trouble at higher currents in the form of compression. The bias will be stable and high.

-Chris
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Old 10th January 2006, 01:36 AM   #4
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Quote:
The bias will be stable and high.
Isnt this a good thing? The sound becomes compressed in this design as the bias current goes higher or if your driving low impedance loads?
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Old 10th January 2006, 01:48 AM   #5
anatech is offline anatech  Canada
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Hi MEGA-amp,
No, it's not a good thing. IT doesn't sound good. At low volumes, that circuit sounds good, when you start getting peaks or a bass line in the music, the sound deteriorates.

As I said, I am still trying to make this sound good.

Bias, at low volumes the heatsink temperature is much higher than at higher volumes. The bias current has remained constant on my experimental units.

-Chris
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Old 10th January 2006, 01:56 AM   #6
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Well that may explain what he says at the end of the amp description: "WARNING: designing phase so some parts could be change in the next days!" Dont know how long its been posted. What do you have driving it? I'd like to try it with just a bridge/cap supply to see how it sounds, but those Sankens are pretty darn expensive. Some details about the schematic are missing too. This is new territory for me.

Thanks.

John
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Old 10th January 2006, 03:06 AM   #7
anatech is offline anatech  Canada
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Hi John,
One never knows. It's only a diamond buffer using power transistors. Nothing really special. Mine has more parts but suffers the same short comings. It has been a learning experience for me.

A commercial design that is related would be a Marantz 300DC. I own one and it sounds good. But only due to a high amount of feedback.

It's an easy circuit, why no build it and experiment?

-Chris
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Old 10th January 2006, 03:25 AM   #8
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Hi, Chris,

Quote:
No, it's not a good thing. IT doesn't sound good. At low volumes, that circuit sounds good, when you start getting peaks or a bass line in the music, the sound deteriorates.
This is exactly what I'm thinking about when seeing diamond buffer output stage. So, it is happening, the current is kind of "limited"? I think DartZeel also experiencing the same thing.

300DC or LC's discrete End Millenium (the first one) is quite different. They use diamond buffer until the driver, the output stage can have all the current they need, the current restriction only up to the drivers. Am I right about this tought?
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Old 10th January 2006, 03:34 AM   #9
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The current feeding the output transistors came only from the CCS, as the input transistors can't source any current into the outputs..
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Old 10th January 2006, 03:36 AM   #10
anatech is offline anatech  Canada
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Hi lumanauw,
The 300DC is a modified diamond buffer with more components added for current protection and better bias behaviour, since the drivers and pre's are not mounted on the heatsink.

The drivers and outputs are supplied via a resistor to the supply rail. The predriver shunts some of this current away, just as in a diamond buffer stage. This design is very sensitive to the vbe drops in the outputs and drivers. Also in the emitter resistors. The only way to make it sound good when delivering large amounts of current is with high feedback factors.

For low current applications, this circuit is great!

-Chris
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