Xref: utzoo rec.audio:7358 sci.electronics:3366
Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!mailrus!husc6!bloom-beacon!mgm.mit.edu!wolfgang
From: wolfgang@mgm.mit.edu (Wolfgang Rupprecht)
Newsgroups: rec.audio,sci.electronics
Subject: Re: Homebrew audio equipment
Message-ID: <6315@bloom-beacon.MIT.EDU>
Date: 20 Jul 88 04:33:16 GMT
References: <1075@gethen.UUCP>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: wolfgang@mgm.mit.edu.UUCP (Wolfgang Rupprecht)
Organization: Freelance Software Consultant, Boston, Ma.
Lines: 31

In article <1075@gethen.UUCP> abostick@gethen.UUCP (Alan Bostick) writes:
>I am interested in building my own audio equipment.  In particular, I
>am thinking of starting out with a stereo amplifier, capable of
>feeding at least 25 W per channel into 8 ohm speakers.

One good reference of for a excellent "generic" power amp, is:
"Build a low TIM Amplifier" W. Marshall Leach, Feb 1976, Audio
Magazine *and*
"Low TIM Amplifier, Part II" W. Marshall Leach, Feb 1977, Audio
Magazine.

This amplifier is the basic mirrored 2-transistor differential,
driving a pair of common-emmitter transistors on both the + and -
rails, followed by a triple darlington output stage.

The really novel thing about this amplifier is that it is designed to
work well with low amounts of (feedback) loop gain.  All internal
stages have lots of local feedback.  The whole amplifier is
compensated with a single-pole feed-forward circuit, which allows a
relatively large high frequency cut-off.  The intention is that even
modest amounts of high frequency energy at the input won't cause the
front-end differential pairs of this amp to be overloaded.

I built up a pair of these amps using 100v transistors and +/- 50v
supplies.  This is good for > 200 watts into 4 ohms, and probably ~800
watts when bridged.  No, I never bought enough output transistors to
build the bridged version.  (I do have the full power-supply, with 2Kw
of 100vdc ;-)

---
Wolfgang Rupprecht	ARPA:  wolfgang@mgm.mit.edu (IP 18.82.0.114)
TEL: (617) 267-4365	UUCP:  mit-eddie!mgm.mit.edu!wolfgang