Re: Please clarify European resistor value notation for me

Eeyore wrote:


Joerg wrote:


Eeyore wrote:

Joerg wrote:

Eeyore wrote:

Joerg wrote:


Graham, seriously, imagine an audio amp of the >$100 class. Maybe a nice
tube amp if you will.

Anything but that ! <makes the sign of the cross>

I was blown away when I listened to one of those at a friend's house.
Definitely less background noise than his previous transistor amp which
was quite high-end. Disconnect the audio source and crank yours up to
the max, at night or so when there is no other noise. Then go close to
the speakers and listen for the faint hiss. No hiss with the tube amp.


Must have been a very poor transistor amp in that case. My amps typically have ~ >100dB s/n ratio

( unweighted ) - that would be > 110dB 'A weighted'.

Maybe yours was more expensive ;-)


Possibly, in fact very likely since I don't do anything under about 200W / channel but getting the
noise down isn't inherently difficult.



That contains, among other things, bass and treble adjusting.

Ah yes. Tone controls. I've heard of these things. :~)


In there you'll find caps that go to ground or to the output
of a younger stage. In order to prevent as much buzz as possible from
getting into the audio signal it is customary to connect the outer foil
to the lower impedance node.

It's not customary where I live and besides where's the buzz going to come from in > > > well

designed kit ?

E-fields. Not just 50Hz but harmonics from dimmers and what not.

Inside a screened enclosure ?

A lot of audio gear doesn't really have that.


None that I know ! Like what ?


I had a Kenwood amp that was quite expensive. Metal bottom, rock solid, but the whole top was made of wood. Really nice wood, actually. Same with lots of other lower end stuff like the Rio stereo in our living room.



IOW to ground or for a series cap to the
output of the previous stage. For that you'd have to know which one of
the capacitor's wires connects to that outer foil.

I follow the principle for sure. It's not unlike having a guard.

Yep.


This may not matter much when listening to "Stairway to Heaven" but on a
Mozart concerto it does matter.

Not here it doesn't. No buzz in my tone controls. Actually, just avoiding hi-Z >>>circuitry is a

good idea too.

Not so easy to do with a hi-Z source. Mikes, record players (those
things that play the large black CDs ...)

Crikey ! Those things all get amplified / buffered before they hit any controls.

But guess what's inside those preamps?


You mean a power supply ?

It's very easy to deal with that. The H field's another matter when everything's in close proximity
but I reckon I could probably make your hair stand on end if you saw some of the compact mixers I've
designed that didn't audibly pick up 50/60 Hz ( and harmonics thereof ) when you look at the
proximiity of the PSU to the electronics. It was an E-I transformer in the example I have in mind too
!


Fields generated outside them amp. It's just the smart thing to connect the outer foil to the lower impedance node because that makes it less sensitive. Plus it costs nothing extra. You just have to know what side the outer foil is...

--
Regards, Joerg

http://www.analogconsultants.com
.

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