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Old 28th July 2008, 06:29 PM   #1
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Default Mosfet amp or Transistor amp?

which one is good..? in terms of transparency? I think Mosfet amps are good enough but I would like to know why Brystons use Transistors?
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Old 28th July 2008, 09:24 PM   #2
Stee is offline Stee  Italy
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Default better way toghether

ciao

my idea is swap the standard hybrid
with transistor in input/VAS + mosfet as final

using

2SK170 AND 2SJ74 for input/VAS
MJE15030 AND MJE15031 (8A-50W) AS FINAL STAGE
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Old 28th July 2008, 09:30 PM   #3
kalmara is offline kalmara  Bulgaria
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You know ... mosfets are also transistors...
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Old 28th July 2008, 09:53 PM   #4
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I think the terms you are looking for are:

Unipolar transistors (field effect devices)

Bipolar transistors (junction devices)

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Old 28th July 2008, 10:46 PM   #5
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Default Re: Mosfet amp or Transistor amp?

Quote:
Originally posted by rhythmdiy
which one is good..? in terms of transparency? I think Mosfet amps are good enough but I would like to know why Brystons use Transistors?

Both are good for amplifiers.
I have built my own using both and had very good results.

Personally I would stick to a tried and tested design.
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Old 29th July 2008, 12:35 PM   #6
AndrewT is online now AndrewT  Scotland
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Default Re: Re: Mosfet amp or Transistor amp?

Quote:
Originally posted by nigelwright7557
Both are good for amplifiers.
I have built my own using both and had very good results.

Personally I would stick to a tried and tested design.
Yes, both BJTs and FETs can give very good results in a good design, but both are capable of very poor results in a bad design.
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Old 29th July 2008, 05:56 PM   #7
Stee is offline Stee  Italy
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Default fet mosfet and bipolar

start with fet on input 2SK170/2SJ74 are very good

then for voltage gain stage better use 2 big mosfet like 2SK1058/2SJ56

For final stage are better bipolar 2SC5200/2SA1943

Complementary configuration is essential for ideal results

the architecture is traditional but without second current stage



sorry don't have good picture
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Old 29th July 2008, 06:01 PM   #8
AndrewT is online now AndrewT  Scotland
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Stee,
the second stage (VAS) uses jFETs in your posted schematic, not big mosFETs.

The capacitance of a 1058 would kill the mid and treble response of the LTP stage.
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Old 29th July 2008, 06:48 PM   #9
Stee is offline Stee  Italy
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Default see now

thanks

may be is better using a little mosfet like IRF610
or IRFD110?

another idea is a paralleling of 2SK170/2SJ74 (3/4 times)
as VAS...
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Old 29th July 2008, 11:03 PM   #10
Stee is offline Stee  Italy
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Default also this is intresting

but need a reverse configuration... to be modern

fet are good for input
mosfet for tension
bipolar for current



(may be)
really final stage have voltage gain too (Drain in common)
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