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Old 29th January 2012, 10:28 AM   #1
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Smile Would like to build super simple mini transistor amplifier

Hello!

I want to build a tiny transistor amplifier, using very few, cheap and commonly available parts (no opamps or ICs). Basically something with regular TO-92 style transistors, or similar. Powered by a simple 9-12 volt wall wart. Just a power switch and a passive volume control. Sound quality is not important, but a bonus. Basically I want to build something like the amp found in cheap computer speakers.

I've been looking around and cannot really find what I need... Does anyone know where I can find a pre-made schematic for something like this?

Thanks!
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Old 29th January 2012, 01:44 PM   #2
DF96 is offline DF96  England
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Look at late 1960s/early 70s radio/electronics magazines. They were full of this sort of thing.
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Old 29th January 2012, 02:58 PM   #3
Wakh is offline Wakh  Russian Federation
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Old 29th January 2012, 04:07 PM   #4
qusp is offline qusp  Australia
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Quote:
Originally Posted by Coconuts 500 View Post
Basically I want to build something like the amp found in cheap computer speakers.
but that would be an opamp/IC
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Old 30th January 2012, 06:17 AM   #5
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Do a search on the net for Sinclair Z30. Remember to add emitter resistors.
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Old 30th January 2012, 06:31 AM   #6
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You might consider the circuits on this page.
With a name like Fun With Tubes the site can't be all bad.
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Old 6th February 2012, 11:17 PM   #7
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Here's a simple output stage I used for a tranny radio. Works well.
John
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Old 7th February 2012, 12:06 AM   #8
sreten is online now sreten  United Kingdom
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Quote:
Originally Posted by Coconuts 500 View Post
Hello!

I want to build a tiny transistor amplifier, using very few, cheap and commonly available parts (no opamps or ICs). Basically something with regular TO-92 style transistors, or similar. Powered by a simple 9-12 volt wall wart. Just a power switch and a passive volume control. Sound quality is not important, but a bonus. Basically I want to build something like the amp found in cheap computer speakers.

I've been looking around and cannot really find what I need... Does anyone know where I can find a pre-made schematic for something like this?

Thanks!
Hi,

Your misguided. You can't build an amplifier just using small signal transistors.
Its stops being simple very quickly when you realise just how rubbish your
simple amplifier is compared to simple IC circuits that have been around
for years, and for good reason, they are simple, and they work well.

No computer speakers use an amplifier of your description. The latest use
mini class d driven from the 5V supply of USB ports. Older ones almost
exclusively use chip-amps. With a 12V supply your talking car audio
and there is simply loads of options, around 5W / 4 ohms for a
simple circuit and up to 20W for bridged into 4 ohms.

IMO just buy a cheap kit off e-pray.

rgds, sreten.
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Last edited by sreten; 7th February 2012 at 12:24 AM.
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Old 7th February 2012, 01:11 AM   #9
Bigun is offline Bigun  Canada
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- this is DIY, no kits! There's a truck load of web sites with simple amps. And power devices may not be so critical if listening to small speakers at low volume - when I listen to my computer speakers I'm guessing they're playing at 1/8 W. But it is a stretch when a couple of power transistors can be had cheaply these days - even a pair of old 2N3055's from an old power supply or something.

http://www.electro-tech-online.com/d...datasheet.html

http://musicouch.com/instruments/str...mple-receiver/
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Last edited by Bigun; 7th February 2012 at 01:14 AM.
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Old 7th February 2012, 07:54 AM   #10
Elvee is online now Elvee  Belgium
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Here is an original proposition.
Despite its simplicity, it even manages to include an auto-bias circuit:
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Last edited by Elvee; 7th February 2012 at 07:57 AM.
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