Re: Bose Acoustic Wave

In article <dcj6s0$ea4$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>, Jem Raid
<jemraid@xxxxxxxxxxxxxxxxxxxxx> wrote:

> "Jim Lesurf" <jcgl@xxxxxxxxxxxxxxxxxx> wrote in message
> news:4d932670abjcgl@xxxxxxxxxxxxxxxxxxxxx

> >
> > Many amplifier designs will provide some amount of rejection of rail
> > (power supply) fluctuations. This is a good to have, however it won't
> > be total, so it is advisible to ensure low ripple if you wish to avoid
> > hum - and also avoid possible distorted crosstalk between channels.


> Dear Jim and Dave,

> The first Gainclone I made with a single transformer in an earthed metal
> box did not hum at all. It was only when I made the wooden box that I
> noticed it, and by the way I have to turn the volume full up and stick
> my ear'ole right next to the speaker to hear it, I suspect that a lot
> more amplifiers do exactly the same.

The problem is not the level of hum apparent when you are not playing
music. It is the rise in levels of hum/buzz when you *are* playing music.
This will add anharmonic components to the music and effectively produce
high levels of 'distortion'. This may also crosstalk of the amps share a
common psu.

> People who are good at metalwork and make their own boxes can make these
> amplifiers completely humless despite the configuration of the power
> supplies.

I doubt that anyone can make an amp that is "completely humless". :-) You
can make ones where the hum isn't audible, though. You can also make them
that show low levels of hum/buzz even at full power.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html
.

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