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Old 17th September 2008, 02:25 PM   #1
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Default Fusion Hybrid 300B

http://www.diyhifisupply.com/?q=cata...brid_amplifier

a little too good to be "true"?

Anyone in HK able to have a listen?

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Old 17th September 2008, 03:41 PM   #2
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I'd be interested in seeing a schematic. And I'd be interested in hearing. Knowing how MOSFETs work, the idea that high driving impedances cause significant changes in character of the output sounds like total bollocks.

All of my experience has told me that MOSFETs are much happier with large voltage swings at their gates than low impedance drivers. The gate oxide leakage in a sanely-constructed transistor ought to be in the vicinity of a few nA.

My two cents is that this is probably a ploy to sell 300Bs with outlandish power ratings. Then again, I haven't heard it.
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Old 17th September 2008, 04:07 PM   #3
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Quote:
Originally posted by koolatron
I'd be interested in seeing a schematic. And I'd be interested in hearing. Knowing how MOSFETs work, the idea that high driving impedances cause significant changes in character of the output sounds like total bollocks.

All of my experience has told me that MOSFETs are much happier with large voltage swings at their gates than low impedance drivers. The gate oxide leakage in a sanely-constructed transistor ought to be in the vicinity of a few nA.

My two cents is that this is probably a ploy to sell 300Bs with outlandish power ratings. Then again, I haven't heard it.
Most mosfet power amplifiers I've worked on were driven by relatively low source impedance driver circuitry, this becomes important with high gate to source capacitance and miller capacitance particularly in transconductance type output stages (common source connection) and even in the case of source followers there is substantial current drawn charging and discharging the gate-source capacitance so this idea while unusual might not be as technically outlandish as it sounds. (We are talking up to nF of capacitance per gate incidentally.) The company selling this kit has a good reputation and I have run into a few of their products over the years - it certainly isn't on the expensive side either for a 300B kit amplifier. I can't really say how it would sound as I have not heard one, but the vendor is not fly by night.
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Old 17th September 2008, 09:38 PM   #4
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From the description it sounds much like the idea of using an SE 45/2A3/300B to drive a firstwatt F4 or Musical Fidelity SuperCharger.... i'm borrowing an F4 to see how well that works.

dave
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Old 18th September 2008, 02:57 AM   #5
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I know diyhifisupply is a good company (I’ve heard a couple of their amps).

While its labeled “50 Watts x 2”, THD is stated as “< 2% (36W@1Khz)”, so with reasonable distortion its more like 30 Watts x 2.

Not that the base model is only US $895 fully assembled. DHFS’s normal 300B amps, with better parts and monoblocks , but in kit form, start with the LD Signature at US $1350.

So there must be “compromises” in parts quality

It’d be good if there was a LD Signature with the mosfet option . .
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Old 24th October 2008, 03:39 AM   #6
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what are the schematics to this amp?
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