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Old 6th October 2006, 02:45 PM   #1121
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JH,

I think he meant Rome, Georgia.
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Old 6th October 2006, 02:47 PM   #1122
eLarson is offline eLarson  United States
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"Wow! This is going to take ALL DAY to build."
-- attributed to Remus upon seeing the plans for Rome.
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Old 7th October 2006, 06:23 PM   #1123
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Quote:
Originally posted by jacco vermeulen
JH,

I think he meant Rome, Georgia.

ya mean-Paris,Texas?
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Old 27th November 2006, 09:03 PM   #1124
rgrav is offline rgrav  United States
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Default fet cascoding

Mr. Pass, I found your latest vfet amp in Audio Express interesting. I have some of Sony's older complemetary vfets that I was thinking of cascoding. You used a mosfet to cascode to the vfet. My question is whether a bipolar would work as well as a mosfet for the cascode, especially in not contributing a sonic signature that would mask the vfet. In a complementary pair of outputs, how does the mosfet behave as a cascode in the crossover region where the mosfets are nonlinear but bjts like Toshiba's 1302/3281 are very linear? I'm going to dig out your old Audio Amateur cascode 60W amp to study it's circuit for this project.
Thanks.
Bob
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Old 28th November 2006, 10:46 PM   #1125
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There's not a lot of difference between using a Mosfet
or a bipolar for the cascode transistor in my book. I
used a Mosfet because I have them laying around like
popcorn.

The cascode transistor imparts very little of its own
character into the signal. With a Mosfet, 100% of the
current through it comes through the cascoded gain
transistor, and the only influence it has is the small
variation in voltage on its Source, which in turn has
a small influence on the the gain transistor, mostly
linear.

With a bipolar, some of the current is sent off through
the Base, so you lose maybe 1% or 2%, but even that
is mostly linear, and doesn't have a lot of effect.

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Old 4th January 2007, 12:33 AM   #1126
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Default Mr. Pass

I thought the idea with using an IGBT operated common base was because signal current does not have to pass through any NPN junctions, but rather a continuous slab of "N" material. Is the capacitance (if any) in a bipolar transistor enough to degrade audio frequencies?
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Old 4th January 2007, 12:47 AM   #1127
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All electronic parts have some amount of capacitance. The degree to which it creeps into the audio spectrum depends on the impedance the capacitance sees.

Grey
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Old 18th January 2007, 01:29 PM   #1128
Stefano is offline Stefano  Italy
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Default No more news?

Hi to all!!!
It would be time for something new, when there'll be a new Zen version?
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Old 20th January 2007, 01:39 AM   #1129
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Yes, it's about time.

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Old 20th January 2007, 06:14 AM   #1130
flg is offline flg  United States
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