Re: [LAU] Fons could you make us an Hammond ;)

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To: <fons@...>, <linux-audio-user@...>
Date: Wednesday, May 13, 2009 - 9:28 pm

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> Could you tell us more about the VibraChorus ? From what you've

And I did add that my knowledge of the vibrachorus was limited=2C the gearb=
ox itself was more fun.

The vibra had a single rotating armature with multiple stacked horizontal f=
ans that formed plate capacitors with 16 fixed plate segments=2C each fan c=
overs about 20 degrees of arc - would you call these 'plate capacitors'=2C =
no? As the rotating armature moved between the fixed plates/fans=2C whateve=
r=2C they fead more signal into it depending on its position. The 16 fixed =
segments were from an 8 stage delay line (including 0 delay) going up then =
coming back down through a single rotation - each of the 8 stages was a cas=
cade of RC delay lines so the larger delays had a darker/warmer sound. The =
output was roughly a vibrato due to scanning through consequetively larger =
phase shifted delays from the RC filters - the movement from one RC delay t=
o the next was quite smooth since the rotating fans would pick up signal fr=
om adjacent delay sections=2C gradually mixing them as it moved. Chorus was=
generated by mixing this signal back in with the direct signal. I could no=
t find any information on the phase shift per section of the cascaded delay=
line by which I mean the actual RC values did not seem to be documented an=
ywhere online.

The rotation speed was fixed as the arm was connected directly to the main =
gearbox spindle=2C the different speeds/depths that made up V3/V2/V1/0/C1/C=
2/C3 purely depended on which of the rotating fans was tapped to the output=
.

You can find a block diagram on wikipedia and if you search further you can=
find a diagram of the build=2C they are quite enlightening as to how it wo=
rked but lacked detail of the RC circuits and naturally emulating its compl=
exities is left up to you. I have not looked at how Beatrix emulates this. =
A lot of synths implement a more simple multitap chorus which is a reasonab=
le extraction. Bristol uses an 8 stage delay line with a different filter c=
utoff on each delay to emphasise the phase shift and taps off up to 4 diffe=
rent positions depending on the C/V selection - it previously also used a c=
horus circuit which had very different characteristics. The current algorit=
hm is also not optimal=2C only the C3 position sounds half reasonable=2C V1=
/V2/V3 are weak. I think this algorithm=2C even with just C3=2C sounds bett=
er than a multitap chorus but then I would naturally have a preference.

Regards=2C Nick.

_________________________________________________________________
Windows Live=99: Keep your life in sync. Check it out!
http://windowslive.com/explore?ocid=3DTXT_TAGLM_WL_t1_allup_explore_0120...

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&gt=3B Could you tell us more about the VibraChorus ? From what you've&=
gt=3B told already it seems to use 'mechanical' variable capacitors...<=
br>And I did add that my knowledge of the vibrachorus was limited=2C the ge=
arbox itself was more fun.The vibra had a single rotating armature =
with multiple stacked horizontal fans that formed plate capacitors with 16 =
fixed plate segments=2C each fan covers about 20 degrees of arc - would you=
call these 'plate capacitors'=2C no? As the rotating armature moved betwee=
n the fixed plates/fans=2C whatever=2C they fead more signal into it depend=
ing on its position. The 16 fixed segments were from an 8 stage delay line =
(including 0 delay) going up then coming back down through a single rotatio=
n - each of the 8 stages was a cascade of RC delay lines so the larger dela=
ys had a darker/warmer sound. The output was roughly a vibrato due to scann=
ing through consequetively larger phase shifted delays from the RC filters =
- the movement from one RC delay to the next was quite smooth since the rot=
ating fans would pick up signal from adjacent delay sections=2C gradually m=
ixing them as it moved. Chorus was generated by mixing this signal back in =
with the direct signal. I could not find any information on the phase shift=
per section of the cascaded delay line by which I mean the actual RC value=
s did not seem to be documented anywhere online.The rotation speed =
was fixed as the arm was connected directly to the main gearbox spindle=2C =
the different speeds/depths that made up V3/V2/V1/0/C1/C2/C3 purely depende=
d on which of the rotating fans was tapped to the output.You can fi=
nd a block diagram on wikipedia and if you search further you can find a di=
agram of the build=2C they are quite enlightening as to how it worked but l=
acked detail of the RC circuits and naturally emulating its complexities is=
left up to you. I have not looked at how Beatrix emulates this. A lot of s=
ynths implement a more simple multitap chorus which is a reasonable extract=
ion. Bristol uses an 8 stage delay line with a different filter cutoff on e=
ach delay to emphasise the phase shift and taps off up to 4 different posit=
ions depending on the C/V selection - it previously also used a chorus circ=
uit which had very different characteristics. The current algorithm is also=
not optimal=2C only the C3 position sounds half reasonable=2C V1/V2/V3 are=
weak. I think this algorithm=2C even with just C3=2C sounds better than a =
multitap chorus but then I would naturally have a preference.Regard=
s=2C Nick.Windows Live=99: Keep your life in sync. Check it out!
=

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Messages in current thread:
[LAU] Fons could you make us an Hammond ;), Grammostola Rosea, (Mon May 11, 9:04 pm)
Re: [LAU] Fons could you make us an Hammond ;), Fons Adriaensen, (Mon May 11, 10:06 pm)
Re: [LAU] Fons could you make us an Hammond ;), Julien Claassen, (Tue May 12, 8:07 am)
Re: [LAU] Fons could you make us an Hammond ;), Natanael Olaiz, (Mon May 11, 11:10 pm)
Re: [LAU] Fons could you make us an Hammond ;), Julien Claassen, (Mon May 11, 10:09 pm)
Re: [LAU] Fons could you make us an Hammond ;), Darren Landrum, (Mon May 11, 11:03 pm)
Re: [LAU] Fons could you make us an Hammond ;), Fons Adriaensen, (Tue May 12, 8:29 pm)
Re: [LAU] Fons could you make us an Hammond ;), Nick Copeland, (Tue May 12, 10:54 pm)
Re: [LAU] Fons could you make us an Hammond ;), philicorda, (Wed May 13, 9:59 pm)
Re: [LAU] Fons could you make us an Hammond ;), Nick Copeland, (Wed May 13, 10:40 pm)
[LAU] Bristol B3 and stuck notes, Nick Copeland, (Thu May 21, 9:42 pm)
Re: [LAU] Bristol B3 and stuck notes, Damon Chaplin, (Fri May 22, 9:41 am)
Re: [LAU] Bristol B3 and stuck notes, Nick Copeland, (Mon May 25, 8:45 pm)
Re: [LAU] Bristol B3 and stuck notes, Paul Davis, (Thu May 21, 10:20 pm)
Re: [LAU] Bristol B3 and stuck notes, Nick Copeland, (Fri May 22, 9:11 am)
Re: [LAU] Bristol B3 and stuck notes, Ken Restivo, (Sat May 30, 2:42 am)
Re: [LAU] Fons could you make us an Hammond ;), Jörn Nettingsmeier, (Wed May 13, 10:08 pm)
Re: [LAU] Fons could you make us an Hammond ;), Grammostola Rosea, (Thu May 14, 9:05 am)
Re: [LAU] Fons could you make us an Hammond ;), Fons Adriaensen, (Wed May 13, 8:23 pm)
Re: [LAU] Fons could you make us an Hammond ;), Grammostola Rosea, (Tue May 19, 8:22 pm)
Re: [LAU] Fons could you make us an Hammond ;), drew Roberts, (Tue May 19, 9:14 pm)
Re: [LAU] Fons could you make us an Hammond ;), Matt Henley, (Tue May 19, 9:23 pm)
Re: [LAU] Fons could you make us an Hammond ;), Joel Roth, (Tue May 19, 9:10 pm)
Re: [LAU] Fons could you make us an Hammond ;), Fons Adriaensen, (Tue May 19, 9:54 pm)
Re: [LAU] Fons could you make us an Hammond ;), Joel Roth, (Wed May 20, 2:59 am)
Re: [LAU] Fons could you make us an Hammond ;), Nick Copeland, (Wed May 13, 9:28 pm)
Re: [LAU] Fons could you make us an Hammond ;), Reuben Martin, (Wed May 13, 3:58 am)
Re: [LAU] Fons could you make us an Hammond ;), Julien Claassen, (Wed May 13, 8:22 am)
Re: [LAU] Fons could you make us an Hammond ;), Folderol, (Tue May 12, 11:09 pm)
Re: [LAU] Fons could you make us an Hammond ;), Darren Landrum, (Tue May 12, 8:52 pm)
Re: [LAU] Fons could you make us an Hammond ;), Fons Adriaensen, (Tue May 12, 9:22 pm)
Re: [LAU] Fons could you make us an Hammond ;), Darren Landrum, (Tue May 12, 9:46 pm)
Re: [LAU] Fons could you make us an Hammond ;), MarcO'Chapeau, (Tue May 12, 7:15 am)
Re: [LAU] Fons could you make us an Hammond ;), Darren Landrum, (Tue May 12, 7:22 pm)
Re: [LAU] Fons could you make us an Hammond ;), Julien Claassen, (Tue May 12, 8:29 am)
Re: [LAU] Fons could you make us an Hammond ;), Josh Lawrence, (Mon May 11, 10:15 pm)
Re: [LAU] Beatrix. Was: Re: Fons could you make us an Hammon..., Grammostola Rosea, (Tue May 12, 1:15 pm)
Re: [LAU] Beatrix. Was: Re: Fons could you make us an Hammon..., Grammostola Rosea, (Tue May 12, 6:07 pm)
Re: [LAU] Beatrix. Was: Re: Fons could you make us an Hammon..., Grammostola Rosea, (Wed May 13, 8:45 am)
Re: [LAU] Fons could you make us an Hammond ;), David Adler, (Mon May 11, 11:29 pm)
Re: [LAU] Fons could you make us an Hammond ;), Gordon JC Pearce, (Mon Jun 15, 11:54 am)
Re: [LAU] Fons could you make us an Hammond ;), Ken Restivo, (Tue May 12, 6:41 am)
Re: [LAU] Fons could you make us an Hammond ;), Julien Claassen, (Tue May 12, 8:11 am)
Re: [LAU] Fons could you make us an Hammond ;), Ken Restivo, (Tue May 12, 8:34 am)
Re: [LAU] Fons could you make us an Hammond ;), Grammostola Rosea, (Tue May 12, 8:16 am)
Re: [LAU] Fons could you make us an Hammond ;), Julien Claassen, (Mon May 11, 10:19 pm)
Re: [LAU] Fons could you make us an Hammond ;), Garry Ogle, (Mon May 11, 11:07 pm)
Re: [LAU] Fons could you make us an Hammond ;), Julien Claassen, (Tue May 12, 8:23 am)
Re: [LAU] Fons could you make us an Hammond ;), Robin Gareus, (Tue May 12, 5:24 pm)
Re: [LAU] Fons could you make us an Hammond ;), Grammostola Rosea, (Tue May 12, 8:31 am)
Re: [LAU] Fons could you make us an Hammond ;), Grammostola Rosea, (Tue May 12, 8:04 am)