A10U8R question (mild troll)...???
 

"Dave Plowman (Nutcase Charlatan)

If you swap 1&3 (both channels) the pot will just work in reverse.


** Only linear pots can be so easily reversed - IDIOT !!

Special " reverse log " or " anti-log " pots are needed to do what you
say.




...... Phil

A10U8R question (mild troll)...???
 

On Tue, 10 Nov 2009 22:19:41 +1100, "Phil Allison"
wrote:


"Dave Plowman (Nutcase Charlatan)

If you swap 1&3 (both channels) the pot will just work in reverse.


** Only linear pots can be so easily reversed - IDIOT !!

Special " reverse log " or " anti-log " pots are needed to do what you
say.




..... Phil




A reverse connected pot will do exactly what Dave said it would. No
special pot is needed. The change in level vs rotation won't be the
same, but that is an entirely different and irrelevant matter.

d

A10U8R question (mild troll)...???
 

"Dave Plowman (News)" wrote

Swap 2&3 and you will likely get strange frequency response errors plus
possibly distortion near zero.

Using pots like that: ie. with the signal applied to the slider and
extracted from the non-earthy end of the track, is not unknown. It was faily
common in early "transistorised" radios and record players etc. And it also
has advantages for simple audio mixers which don't use a virtual-earth
summing amp.

David.

A10U8R question (mild troll)...???
 

On Tue, 10 Nov 2009 12:04:43 -0000, "David Looser"
wrote:

"Dave Plowman (News)" wrote

Swap 2&3 and you will likely get strange frequency response errors plus
possibly distortion near zero.

Using pots like that: ie. with the signal applied to the slider and
extracted from the non-earthy end of the track, is not unknown. It was faily
common in early "transistorised" radios and record players etc. And it also
has advantages for simple audio mixers which don't use a virtual-earth
summing amp.

David.


The mixing solution I used before I discovered the virtual earth
amplifier was to connect the pots the usual way, but add a resistor in
series with the slider so it would not impose a short when turned all
the way down.

I've never seen a circuit (except inside some guitars for various odd
tonal reasons) that used a configuration that put the signal into the
slider.

d

A10U8R question (mild troll)...???
 

"Don Pearce" wrote in message
...
On Tue, 10 Nov 2009 12:04:43 -0000, "David Looser"
wrote:

"Dave Plowman (News)" wrote

Swap 2&3 and you will likely get strange frequency response errors plus
possibly distortion near zero.

Using pots like that: ie. with the signal applied to the slider and
extracted from the non-earthy end of the track, is not unknown. It was
faily
common in early "transistorised" radios and record players etc. And it
also
has advantages for simple audio mixers which don't use a virtual-earth
summing amp.

David.


The mixing solution I used before I discovered the virtual earth
amplifier was to connect the pots the usual way, but add a resistor in
series with the slider so it would not impose a short when turned all
the way down.

I've never seen a circuit (except inside some guitars for various odd
tonal reasons) that used a configuration that put the signal into the
slider.


Early semiconductor small-signal amplifier stages often used a single
germanium transistor in a grounded emitter configuration, with a low
resistance bias network connected to the base. Such a stage has a lower
input than output impedance. In those circumstances it makes sense to run
the volume control "backwards", as the control is turned down the pot loads
the relatively high output impedance of the preceding stage. And simple
mixers often work run that way, each input is applied, via a resistor, to
the slider of a pot. And the output is taken from the tracks of all the pots
wired in parallel. It has some advantages compared to the way you did it.

David.

A10U8R question (mild troll)...???
 

On Tue, 10 Nov 2009 12:22:32 -0000, "David Looser"
wrote:

"Don Pearce" wrote in message
...
On Tue, 10 Nov 2009 12:04:43 -0000, "David Looser"
wrote:

"Dave Plowman (News)" wrote

Swap 2&3 and you will likely get strange frequency response errors plus
possibly distortion near zero.

Using pots like that: ie. with the signal applied to the slider and
extracted from the non-earthy end of the track, is not unknown. It was
faily
common in early "transistorised" radios and record players etc. And it
also
has advantages for simple audio mixers which don't use a virtual-earth
summing amp.

David.


The mixing solution I used before I discovered the virtual earth
amplifier was to connect the pots the usual way, but add a resistor in
series with the slider so it would not impose a short when turned all
the way down.

I've never seen a circuit (except inside some guitars for various odd
tonal reasons) that used a configuration that put the signal into the
slider.


Early semiconductor small-signal amplifier stages often used a single
germanium transistor in a grounded emitter configuration, with a low
resistance bias network connected to the base. Such a stage has a lower
input than output impedance. In those circumstances it makes sense to run
the volume control "backwards", as the control is turned down the pot loads
the relatively high output impedance of the preceding stage. And simple
mixers often work run that way, each input is applied, via a resistor, to
the slider of a pot. And the output is taken from the tracks of all the pots
wired in parallel. It has some advantages compared to the way you did it.

David.


Still a strange topology. What normally happens when you load down a
transistor stage with too low an impedance is massive distortion
because of the asymmetric sink/source current drive capacity.

d

A10U8R question (mild troll)...???
 

In article , Don Pearce
wrote:
On Tue, 10 Nov 2009 12:22:32 -0000, "David Looser"
wrote:

Early semiconductor small-signal amplifier stages often used a single
germanium transistor in a grounded emitter configuration, with a low
resistance bias network connected to the base. Such a stage has a lower
input than output impedance. In those circumstances it makes sense to
run the volume control "backwards", as the control is turned down the
pot loads the relatively high output impedance of the preceding stage.
And simple mixers often work run that way, each input is applied, via
a resistor, to the slider of a pot. And the output is taken from the
tracks of all the pots wired in parallel. It has some advantages
compared to the way you did it.

Still a strange topology. What normally happens when you load down a
transistor stage with too low an impedance is massive distortion because
of the asymmetric sink/source current drive capacity.

IIUC What david was referring to was situations where the transistor was
essentially acting as a signal *current* source. In those terms the
arrangement has its logic I guess. But I can't recall using it or seeing
any domestic kit that did for audio.

Since c1980 I've tended to assume any decent pre amp or source can drive
10k//1000pF since that was the IHFA707 requirement I think. So allowing to
parallel connection to something like a recorder, I'd be happy with pots of
around 20k to 50k, and suspect 10k would be fine. Although as exposed in a
much earlier thread some sources can be caught out by this. Example being
the small o/p cap of a Quad FM tuner so that a low load tends to roll away
the LF.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

A10U8R question (mild troll)...???
 

In article ,
Phil Allison wrote:

"Dave Plowman (Nutcase Charlatan)

If you swap 1&3 (both channels) the pot will just work in reverse.


** Only linear pots can be so easily reversed - IDIOT !!


Really? What makes *any* pot special so it can't be soldered
incorrectly? And did I state it would work 'normally' but in reverse?
I rest my case, M'lud...

Special " reverse log " or " anti-log " pots are needed to do what
you say.

If you'd gone to the bother of sourcing an anti-log pot I'd assume
you knew what it would do.

Oh - and if you gave the matter some thought, it's possible wiring the pot
in reverse might make setting the *required* level *easier*, since it's
being used as a preset. But thinking never was your strong point.




..... Phil

--
*Why is it called tourist season if we can't shoot at them?

Dave Plowman London SW
To e-mail, change noise into sound.

A10U8R question (mild troll)...???
 

"Jim Lesurf" wrote

IIUC What david was referring to was situations where the transistor was
essentially acting as a signal *current* source.

Yup. The sort of amplifier stage I was talking about has no NFB, so the
ouput impedance is just that of the (naturally high) collector impedance in
parallel with the collector load resistor.

In those terms the
arrangement has its logic I guess. But I can't recall using it or seeing
any domestic kit that did for audio.

I've met a number of examples of it, mostly in "first generation"
transistorised audio equipment made between the mid '50s and the mid '60s.

David.

A10U8R question (mild troll)...???
 

"Dave Plowman (Nutcase Charlatan)

If you swap 1&3 (both channels) the pot will just work in reverse.


** Only linear pots can be so easily reversed - IDIOT !!


And did I state it would work 'normally' but in reverse?


** What you said is right here to be seen.

And is 100% WRONG !!



Special " reverse log " or " anti-log " pots are needed to do what
you say.

If you'd gone to the bother of sourcing an anti-log pot I'd assume
you knew what it would do.

** Total red herring.

Rest of this lying charlatan's insane drivel delivered to the sewer.



... Phil