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 Forum index » Instruments and Equipment » Alesis Andromeda
FM out of tune?
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terrytee



Joined: Mar 03, 2010
Posts: 11
Location: UK

PostPosted: Wed Jul 07, 2010 4:56 am    Post subject: FM out of tune? Reply with quote  Mark this post and the followings unread

Is it my imagination or does the FM such as Linear & exponential modulation have difficulty staying in tune when in poly mode? I have tried changing the assign to the lowest as opposed to rotary but still no joy. You can tell the tuning difference on patches such as DX7 BELL. I generally use the A6 with BKTUNE off but it still sounds wrong using FM with BK on or off and the same thing with TMPTUN on or off. Any advise or tips.
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sunny pedaal



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PostPosted: Wed Jul 07, 2010 6:06 am    Post subject: Reply with quote  Mark this post and the followings unread

YES, FOR POLY FM YOU'D BETTER SWITCH TO YAMAHA'S DX SERIES.
NOT ENOUGH IN TUNE I'M AFRAID
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terrytee



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PostPosted: Wed Jul 07, 2010 6:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the info Sunny, is the problem unique to the design of the A6 or is it a issue with all analogue polys, you will have to forgive my lack of knowledge here but am still a novice a programming synths.
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sunny pedaal



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PostPosted: Wed Jul 07, 2010 7:10 am    Post subject: Reply with quote  Mark this post and the followings unread

onthe jp8 it's more stable, but still so incontrollable that it takes a lot of work and luck to make a tuned bell patch. with the a6 the difficulties are even larger due to differences between the chips.
something like that.
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Shreddie



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PostPosted: Tue Jul 13, 2010 12:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

terrytee wrote:
Thanks for the info Sunny, is the problem unique to the design of the A6 or is it a issue with all analogue polys,

It's the nature of analogue synths, especially those with VCOs such as the Andromeda.

In synths such as the Yamaha DX/TX series, the FM is acheived digitally so (to all intents and purposes) is perfect. With analogue synths that use DCOs (the JP8 is DCO isn't it?), the oscillators are digitally controlled, they should be very stable and have (mostly) repeatable results. VCOs are inherently slightly unstable so repeatable results with FM on those kind of synths will be far more difficult.
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sunny pedaal



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PostPosted: Wed Jul 14, 2010 12:09 am    Post subject: Reply with quote  Mark this post and the followings unread

aren't jp8 and a6 both hybride ? (otherwise having memories would be a big thing to achieve ).
think structure of jp8 and a6 are a bit similar ( analog soundchips, but afcourse different types and voltages/currents )
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soundwave106



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PostPosted: Wed Jul 14, 2010 3:34 am    Post subject: Reply with quote  Mark this post and the followings unread

JP8 and A6 are both VCO synths. The JP8 does have some differences -- the envelopes in the JP8 for instance are analog, the A6 ones are digital -- but there obviously is some digital control for patch memory etc.

For A6 FM: One big issue here would be that FM would have to become part of the auto-tune routine. If I recall a code404 list discussion (unfortunately I don't see archives anymore to confirm), this was considered, but this would have added expense / time that was deemed unacceptable, or would've caused problems in manufacturing etc., or both. Whatever it was, it was unfortunately was left off.

Even "in tune" VCOs aren't guaranteed to be phase-locked, so you will not get the precision results you will get out of a digital synth. But if the FM circuits were calibrated you'd at least get "in tune" results, I'd think. Oh, well.
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sunny pedaal



Joined: Nov 16, 2004
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PostPosted: Wed Jul 14, 2010 8:41 am    Post subject: Reply with quote  Mark this post and the followings unread

copy of 404files:
http://electro-music.com/forum/download.php?id=11682
(under "tips and tricks to the a6"topic at this forum )
use "find"function in your textprogramm to get to destignation
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soundwave106



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PostPosted: Wed Jul 14, 2010 9:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Ah, here we go.

My guess is, the project team simply ran out of time and energy to add the FM VCA calibration (possibly even running out of room on the ASIC or another technical reason). It seems hardware related so it'd be a bit involved to fix.

A software "manual FM tune adjustment" workaround seems possible, but Alesis, of course, went bankrupt before implementing nice-to-have features like this.



From dfevans at bbcr.uwaterloo.ca Tue Jan 7 09:08:38 2003
From: dfevans at bbcr.uwaterloo.ca (David Evans)
Date: Fri Jul 14 01:05:04 2006
Subject: [A6] The infamous A6 FM
In-Reply-To: <3E1B0745>;
from jered@future-retro.com on Tue, Jan 07, 2003 at 10:58:45AM -0600
References: <BA4096A2>
<3E1B0745>
Message-ID: <20030107120838>

On Tue, Jan 07, 2003 at 10:58:45AM -0600, Future Retro Synthesizers wrote:
> Hello all,
> I recently started using the A6, and am new to the list. I notice some
> strange things when modulating oscillator A with oscillator B's
> waveform. I play a note and set the FM to create a desired tone. I then
> play the same key repeatedly and the tone varies for each new key press
> (I assume this is due to different voices being used to play the tone).

Yep. This is basically a FAQ. The VCA that controls the FM index is not
calibrated by the CPU, so there's no way to ensure that it is the same for
all voices. I don't know whether the hardware precludes such a calibration
or whether the software simply doesn't do it.


From dfevans at bbcr.uwaterloo.ca Tue Nov 26 12:28:28 2002
From: dfevans at bbcr.uwaterloo.ca (David Evans)
Date: Fri Jul 14 01:04:40 2006
Subject: [A6] fm instability
In-Reply-To:
<1C97CD80D442DE49996AAEA0B9417C304F7D4C>; from
cgraef@nyc.rr.com on Tue, Nov 26, 2002 at 03:13:19PM -0500
References:
<1C97CD80D442DE49996AAEA0B9417C303BE54B>
<1C97CD80D442DE49996AAEA0B9417C304F7D4C>
Message-ID: <20021126152828>

On Tue, Nov 26, 2002 at 03:13:19PM -0500, charles graef wrote:
> Fair enough. This sounded like an application where accurate tracking
> was paramount, which most people's analog equipment isn't really
> designed to deliver.

I don't think that the issue is tracking but rather lack of precise control
over FM index, caused by the inability to calibrate the relevant VCA. In a
way this may be a harder problem to solve than tracking, since it's pretty
easy to adjust VCO frequency offsets under CPU control. My guess is that the
ASIC designers just ran out of space and had to stop somewhere.


From peake at pacificnet.net Wed Nov 27 09:24:50 2002
From: peake at pacificnet.net (Mike Peake)
Date: Fri Jul 14 01:04:42 2006
Subject: [A6] fm instability
In-Reply-To: <200211270918>
References: <200211270918>
Message-ID: <f05100302ba0aaea1b547>

I'm the reason, if I may be bold, that the
FM paths are there. It's one of my contributions
and the team were quite understanding in fulfilling
my requests for them (as well as not laughing
at the signal path chart; when you see the
nest of paths that exist, your first instinct
is to reduce the clutter). Not everything on
the synth is what was intended from
the beginning, as is the case in many projects,
yet it is there for what it's worth. FM is
very important to me, even if it's uncalibrated.
The VCAs, for some reason, were not looped back
into the feedback path which allows the computer
to calibrate things. I don't remember if this
was due to an impossibility (chip layout) or
not.

We saw the forest, but did not have the time
nor the resources to shape it into Bonzai.

I know. It would be nice. It was an enormous
project as it was. If one day it were possible
to hand-tune the FM VCAs, it would rock.

Easier,

-Mike
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Peake



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PostPosted: Wed Aug 11, 2010 12:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

Correct. They're not computer-calibrated, and most importantly that is not mentioned here AFIAK, is that the =depth= of the exponential FM is modular-range, not that displayed on synths such as the Xpander or MKS-80, etc. If you keep the FM depth down very low, you'll be in the range of those polysynths, and may have luck getting "tuned"-sounding exponential FM. The A6 FM paths are "fully open" and allow the maximum possible depth, instead of being limited.

Quite honestly, exponential FM of modular depth, is fairly useless unless you've got triangle core VCOs, such as the Buchla 100/200. Sawtooth core VCOs start extremely bright and simply get brighter. Triangle core FM starts shaped to sine waves, if you wish, and then goes out to pitched noise and further. The Andromeda oscillators are sawtooth core.

This track uses only Buchla oscillators and there's lots of exponential FM going on, all sine-to-sine (and often back again) waveforms. Saw-to-saw FM just isn't like this:

http://www.soundclick.com/bands/default.cfm?bandID=114997

"Impart/Tangent_Buchla200"

Try subtle linear FM on the A6 and see what you can get...

_________________
We are selling emotions, there are no emotions in a grid. -mwagener

"IC 741. Sometimes you don't want fidelity." -Small Bear Electronics Catalog
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Peake



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PostPosted: Wed Aug 11, 2010 12:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Peake wrote:
Correct. They're not computer-calibrated, and most importantly that is not mentioned here AFIAK, is that the =depth= of the exponential FM is modular-range, not that displayed on synths such as the Xpander or MKS-80, etc. If you keep the FM depth down very low, you'll be in the range of those polysynths, and may have luck getting "tuned"-sounding exponential FM. The A6 FM paths are "fully open" and allow the maximum possible depth, instead of being limited.

Quite honestly, exponential FM of modular depth, is fairly useless unless you've got triangle core VCOs, such as the Buchla 100/200. Sawtooth core VCOs become too uncontrolled. Triangle core FM starts shaped to sine waves, if you wish, and then goes out to pitched noise and further. The Andromeda oscillators are sawtooth core.

This track uses only Buchla oscillators and there's lots of exponential FM going on, all sine-to-sine (and often back again) waveforms. Saw-to-saw FM just isn't like this:

http://www.soundclick.com/bands/default.cfm?bandID=114997

"Impart/Tangent_Buchla200"

Try subtle linear FM on the A6 and see what you can get...

_________________
We are selling emotions, there are no emotions in a grid. -mwagener

"IC 741. Sometimes you don't want fidelity." -Small Bear Electronics Catalog
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sunny pedaal



Joined: Nov 16, 2004
Posts: 687
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PostPosted: Wed Aug 11, 2010 1:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Peake wrote:
Peake wrote:
Correct. They're not computer-calibrated, and most importantly that is not mentioned here AFIAK, is that the =depth= of the exponential FM is modular-range, not that displayed on synths such as the Xpander or MKS-80, etc. If you keep the FM depth down very low, you'll be in the range of those polysynths, and may have luck getting "tuned"-sounding exponential FM. The A6 FM paths are "fully open" and allow the maximum possible depth, instead of being limited.

Quite honestly, exponential FM of modular depth, is fairly useless unless you've got triangle core VCOs, such as the Buchla 100/200. Sawtooth core VCOs become too uncontrolled. Triangle core FM starts shaped to sine waves, if you wish, and then goes out to pitched noise and further. The Andromeda oscillators are sawtooth core.

This track uses only Buchla oscillators and there's lots of exponential FM going on, all sine-to-sine (and often back again) waveforms. Saw-to-saw FM just isn't like this:

http://www.soundclick.com/bands/default.cfm?bandID=114997

"Impart/Tangent_Buchla200"

Try subtle linear FM on the A6 and see what you can get...

interesting, thanks
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