Arny Krueger wrote:

Here's the key Keith. It is obviously a device that has an audible effect.


No **** Sherlock. You must be a ****ing Harvard graduate.


--
Bill Coombes

Keith G wrote:

http://www.moirac.adsl24.co.uk/showntell/MicPreAmp.jpg

I've always ignored it and used it 'Flat' but what does it
do? What's actually happening/being done to the signal
when it is turned through the various 'instruments'? (I'll
have to have a fiddle with it sometime!)

Assuming Arny's right and the two triodes are only used for
FX, then you have two inverting valve gain stages in series.
So if you set both triodes up for high even harmonic
distortion, you can get a lot of odd harmonics from the
pair. Basically, it allows you to stretch the signal in one
direction, turn it over, and stretch it the other way.
Perhaps your circuit varies the proportion of signal applied
to each valve stage, as well as varying the proportion
applied to the pair. That then gives you some control over
both the level and the type of distortion.

AFAIR there's a company called "Pax" that offers some kind
of "colour control" on its valve amps.

I wonder what it is about instruments that determines
whether they prefer one kind of distortion rather than
another? Maybe it depends on the harmonic signature of the
instrument. Even for flute, odd for sax, maybe.

Ian

In article ,
Ian Iveson wrote:
I wonder what it is about instruments that determines
whether they prefer one kind of distortion rather than
another? Maybe it depends on the harmonic signature of the
instrument. Even for flute, odd for sax, maybe.

Think so. Hence some instruments sounding more 'exciting' on vinyl than
digital. Introducing distortion to an acoustic instrument via the
electronics in whatever way is called adding 'edge' by some.

--
*It's a thankless job, but I've got a lot of Karma to burn off

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

In article , Dave Plowman (News)
wrote:
In article , Ian Iveson
wrote:
I wonder what it is about instruments that determines whether they
prefer one kind of distortion rather than another? Maybe it depends
on the harmonic signature of the instrument. Even for flute, odd for
sax, maybe.

Think so. Hence some instruments sounding more 'exciting' on vinyl than
digital. Introducing distortion to an acoustic instrument via the
electronics in whatever way is called adding 'edge' by some.

Which all seems an innocuous idea... until you encounter intermodulation
distortion from chords and/or combination of instruments playing together.

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

"Ian Iveson" wrote in message
...
Keith G wrote:

http://www.moirac.adsl24.co.uk/showntell/MicPreAmp.jpg

I've always ignored it and used it 'Flat' but what does it do? What's
actually happening/being done to the signal when it is turned through the
various 'instruments'? (I'll have to have a fiddle with it sometime!)

Assuming Arny's right



Are you serious....??



and the two triodes are only used for
FX, then you have two inverting valve gain stages in series. So if you set
both triodes up for high even harmonic distortion, you can get a lot of
odd harmonics from the pair. Basically, it allows you to stretch the
signal in one direction, turn it over, and stretch it the other way.
Perhaps your circuit varies the proportion of signal applied to each valve
stage, as well as varying the proportion applied to the pair. That then
gives you some control over both the level and the type of distortion.

AFAIR there's a company called "Pax" that offers some kind of "colour
control" on its valve amps.

I wonder what it is about instruments that determines whether they prefer
one kind of distortion rather than another? Maybe it depends on the
harmonic signature of the instrument. Even for flute, odd for sax, maybe.


It's all very curious. I've just recorded a range of test tones by means of
a mic over the speaker and clicked the 'Voicing' knob round clockwise at
approximately one click per second (with a few 'double click' cock-ups):

http://www.moirac.adsl24.co.uk/showntell/MicPreAmp.jpg


It most definitely has an audible effect on the sound, as well as a visible
effect on the waveform - looks like this:

http://www.moirac.adsl24.co.uk/shown...tWaveForms.jpg


Sounds like this:

http://www.moirac.adsl24.co.uk/shown...sted-100Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-250Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-440Hz.wav

http://www.moirac.adsl24.co.uk/shown...usted-1kHz.wav

http://www.moirac.adsl24.co.uk/shown...sted-10kHz.wav


(Note reduced levels in the 'second half', as it passes through the OPL
section.)

Anyway, all very quick and dirty - it would take a solid week to do it
'scientifically' and I'm not sure any of the 'voices' are appropriate for
the instruments I'm recording! I might try a comparison between 'Flat' and a
couple of the settings some time in the future and possibly post them for
crits, in the usual manner!!

But I hafta say the main temptation is to get a mic pre without any FX and
compare the two! If nothing else, the 'effects' are going to be almost
infinitely variable given different instruments, different mics and varying
recording environments (rooms or positioning in the room) - way too damn
complicated!!

"Keith G" wrote


Sounds like this:

http://www.moirac.adsl24.co.uk/shown...sted-100Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-250Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-440Hz.wav

http://www.moirac.adsl24.co.uk/shown...usted-1kHz.wav

http://www.moirac.adsl24.co.uk/shown...sted-10kHz.wav



Watch the sound levels on the 1 kHz and 10 kHz samples - they are plenty
loud if you are listening on earphones!!

Keith G wrote:

It most definitely has an audible effect on the sound, as well as a
visible effect on the waveform - looks like this:

http://www.moirac.adsl24.co.uk/shown...tWaveForms.jpg


Sounds like this:

http://www.moirac.adsl24.co.uk/shown...sted-100Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-250Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-440Hz.wav

http://www.moirac.adsl24.co.uk/shown...usted-1kHz.wav

http://www.moirac.adsl24.co.uk/shown...sted-10kHz.wav


That's not distortion that's clipping.

Cheers

Ian

"Ian Bell" wrote in message
...
Keith G wrote:

It most definitely has an audible effect on the sound, as well as a
visible effect on the waveform - looks like this:

http://www.moirac.adsl24.co.uk/shown...tWaveForms.jpg


Sounds like this:

http://www.moirac.adsl24.co.uk/shown...sted-100Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-250Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-440Hz.wav

http://www.moirac.adsl24.co.uk/shown...usted-1kHz.wav

http://www.moirac.adsl24.co.uk/shown...sted-10kHz.wav


That's not distortion that's clipping.

Cheers

Ian



You're right - too much haste!

(Wish I knew what caused the -6 dB 'ceiling' when recording mono in this
software!!)

I've trimmed them back (I was only going to post the 440 Hz sample
originally!)

Now looks like this:

http://www.moirac.adsl24.co.uk/shown...tWaveForms.jpg


Which now sounds like this:

http://www.moirac.adsl24.co.uk/shown...sted-100Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-440Hz.wav


And better shows the 'steps' as the knob was clicked round.

Keith G wrote:

"Ian Bell" wrote in message
...
Keith G wrote:

It most definitely has an audible effect on the sound, as well as a
visible effect on the waveform - looks like this:

http://www.moirac.adsl24.co.uk/shown...tWaveForms.jpg


Sounds like this:

http://www.moirac.adsl24.co.uk/shown...sted-100Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-250Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-440Hz.wav

http://www.moirac.adsl24.co.uk/shown...usted-1kHz.wav

http://www.moirac.adsl24.co.uk/shown...sted-10kHz.wav


That's not distortion that's clipping.

Cheers

Ian



You're right - too much haste!

(Wish I knew what caused the -6 dB 'ceiling' when recording mono in this
software!!)

I've trimmed them back (I was only going to post the 440 Hz sample
originally!)

Now looks like this:

http://www.moirac.adsl24.co.uk/shown...tWaveForms.jpg


Which now sounds like this:

http://www.moirac.adsl24.co.uk/shown...sted-100Hz.wav

http://www.moirac.adsl24.co.uk/shown...sted-440Hz.wav


And better shows the 'steps' as the knob was clicked round.





That's more like it. The first section has a typical poor tube
overdrive spectrum, 2nd harmonic -44dB down, 3rd -37dB, 4th -62dB and
fifth -49dB and so on. This is typical odd harmonic dominated and in my
view detracts from the sound rather than adding to it. Looking at the
quietest section, the spectra are exactly the same which is a little
odd. It implies the tube is being driven at a constant level.

Cheers

Ian

In article ,
Keith G wrote:
(Wish I knew what caused the -6 dB 'ceiling' when recording mono in this
software!!)

When you add two mono signals - like say left and right of a stereo signal
which are identical, you get an increase of 6 dB. You can get near this if
a genuine stereo signal contains the loudest part in effectively mono. So
to avoid any chance of over modulation many simple progs will attenuate
things by 6 dB when you switch to mono.

--
*Geeks shall inherit the earth *

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