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Old 11th April 2004, 06:15 PM   #1
millwood is offline millwood  United States
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Default simple pre amps

Can we start a thread for simple pre amps? here is my entry.

I used to have a php850 as a pre amp on my workbench. It is too big and takes way too much space so I put this together.

It is essentially an se pre amp, with a little bit of feedback. It has proven to be very adpat at different rail voltage (from 18v all the way to 100v, with zero changes to the compoenents). performance was decent but not exactly great (for a 1 transistor, 6 resistos and two caps preamp).

the selection of the transistor is not critical (I used irf510, 540, and some fairfield mosfets / bjts). when you use a bjt (I tried tip41, mje15030 and 2n5551), double r3 to 47k. from simulations, the performance seems to be better for BJTS or MOSFETS with small input capacitance.

mine is decoupled from the rail with a RC network (10ohm resistor + 470uf cap). it sounds great to my ears. not bad for a couple hours of work.
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Old 12th April 2004, 06:54 AM   #2
planet10 is online now planet10  Canada
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simple pre amps
this one is pretty simple

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community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
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Old 12th April 2004, 05:59 PM   #3
samod is offline samod  Ukraine
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simple pre amps
Greet all radio-community!
I ask you are voiced on my scheme.
I am a recent user MS7...
Can will say their own reviews?
The Full version of the schemes here:


Is Not got while attach the picture...
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Old 25th April 2004, 11:09 PM   #4
millwood is offline millwood  United States
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to just follow up on my own thread, here is one channel of my simple pre-amp.

the only changes are: 1) R3 is 47k, 2) emitter/ source resistor is 220ohm to provide additional gain and 3) a little trimmer upfront.

the transistor in this particular picture is a 2sc4793 mounted on one side of a dip14 socket. the goal is to use an adapter so that it runs off 2n5551 and then build another channel on the other side of the same socket.

performance according to simulation (on 2n5551) is thd 0.009% throughout (mostly 2nd and 3rd harmonics). Sound? good to my ears. It is mated to my mosfet jlh1969.

The module can also run off mosfets without any modification (tried 510, 540 and a few fairfield small to medium power mosfets)
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