Doepfer

No, I was talking about adding VC without the A101-9. My suitcase is full!

Peter, thank you VERY much for the detailed info. I really appreciate it.

Funny I was just about to start breadboarding a driver circuit for the Vactrol solution... but like Peter said, "...It would be more prudent just to buy a VCLFO..."

Been spending more time Building Sound lately, and I'd like to keep it that way!

Thanx again to all who replied,

Tony



----------------------------------------
> To: Doepfer_a100@yahoogroups.com
> From: synth_freak_2000@yahoo.com
> Date: Sat, 5 Jan 2008 02:23:08 -0800
> Subject: Re: [Doepfer_a100] Re: adding CV to A-145 LFO
> 
> hello Peter,
> thank you for the usefull info!
> but,
> i think, by using vactrols, he means by adding the
> universal vactrol module A101-9. this should make the
> vactrol mod much easier, i guess.
> but it would probably require on more 4HP faceplate to
> add the vactrol input. or not?
> best regards,
> Bakis.
> 
> 
> --- "(i think you can figure that out)"
>  wrote:
> 
>> You shouldn't need a vactrol at all.  There is a
>> current limiting 100K
>> resistor coming from the wiper (center pin) of the
>> Freq pot.  That's
>> the only place the wiper goes, this 100K resistor
>> should be easy to
>> locate. One end of that resistor goes to the wiper,
>> the other end goes
>> to one of the negative inputs of the two opamps. 
>> That means either
>> pins 2, 6, 9 or 13.  That's the first thing you have
>> to find. So you
>> buzz out and find the 100K resistor that goes to the
>> center pin of the
>> Freq pot, go across the other side of that resistor
>> and buzz out which
>> IC and which pin (2, 6, 9 or 13) that side shorts
>> to.
>> 
>> Once you find  point where the other side of the
>> 100K goes to either
>> of the two op amp ICs at either pins 2, 6, 9, or
>> 13...then stop
>> looking.  That's the one you need.
>> 
>> Add your VC Input jack to the faceplate, run it's
>> output to another
>> resitor you'll need to add (another current limiter,
>> start at 100K and
>> work down until you're happy with the response, but
>> try not to go
>> lower than 47K), and connect the output of that
>> added resistor to the
>> node of the PCB mentioned above. So you run the
>> output of your
>> resistor to the other end of the resistor on the
>> Dopefer PCB which
>> comes from the wiper of their Freq pot.
>> 
>> That should do it.
>> 
>> You can add a attenuation pot if you wish as well
>> (if there's room for
>> both the jack and the added pot on the faceplate,
>> not sure if there is): 
>> 
>> In that case, the output of the jack you add goes to
>> one of the end
>> pins of the added pot the other end pin of that pot
>> is connected to
>> ground. The wiper of the added pot (the center
>> pin)is connected to the
>> current limiter resistor you just added which I
>> explained in the last
>> paragraph.
>> 
>> If you attenuator works in inverse (less FM when
>> turning the pot CW),
>> then reverse the wires coming from it's two end
>> pins.
>> 
>> Not sure how the expo converter works on this
>> particular LFO, so you
>> may not get linear VC response, and most definately
>> not 1v/oct, but
>> this mod should work OK.
>> 
>> Yes you could do it by added a vactrol, but that
>> would require cuts
>> traces on the LFO PCB, a bunch of discrete
>> components to drive the
>> vactrol LED, and the VAC itself.  Basically another
>> board will be
>> required. It would be more prudent just to buy a
>> Doepfer VC LFO in my
>> opinion.
>> 
>> It's worth a skipping all that and trying this
>> first.  
>> 
>> - P
>> 
>> 
>> --- In Doepfer_a100@yahoogroups.com, Anthony Rolando
>> 
>> wrote:
>>>
>>> 
>>> I would like to add Voltage control to my A-145
>> LFO. I would like to
>> do so with a Vactrol. Would anybody be willing to
>> point me in the
>> right direction? 
>>> 
>>> Would it be possible that I could look at a
>> portion of the schematic
>> so that I could add this?
>>> 
>>> Thanx,
>>> 
>>> Tony
>>>
>>
> _________________________________________________________________
>>> Share life as it happens with the new Windows
>> Live.
>>>
>>
> http://www.windowslive.com/share.html?ocid=TXT_TAGHM_Wave2_sharelife_122007
>>>
>> 
>> 
>> 
> 
> 
> Bakis Sirros - Parallel Worlds / Interconnected / Memory Geist
> [Doepfer_a100] group owner
> http://www.parallel-worlds-music.com
> http://www.myspace.com/parallelworldsmusic
> http://www.myspace.com/interconnectedmusic
> http://www.myspace.com/memorygeist
> http://www.DiN.org.uk
> http://www.musicamaximamagnetica.com
> http://www.shimarecords.co.uk
> http://www.rubber.gr
> Athens-Greece
> 
> 
>       ____________________________________________________________________________________
> Looking for last minute shopping deals?  
> Find them fast with Yahoo! Search.  http://tools.search.yahoo.com/newsearch/category.php?category=shopping
> 
> 
>  
> Yahoo! Groups Links
> 
>  To visit your group on the web, go to:
>     http://groups.yahoo.com/group/Doepfer_a100/
> 
>  Your email settings:
>     Individual Email | Traditional
> 
>  To change settings online go to:
>     http://groups.yahoo.com/group/Doepfer_a100/join
>     (Yahoo! ID required)
> 
>  To change settings via email:
>     mailto:Doepfer_a100-digest@yahoogroups.com 
>     mailto:Doepfer_a100-fullfeatured@yahoogroups.com
> 
>  To unsubscribe from this group, send an email to:
>     Doepfer_a100-unsubscribe@yahoogroups.com
> 
>  Your use of Yahoo! Groups is subject to:
>     http://docs.yahoo.com/info/terms/
>  

_________________________________________________________________
Get the power of Windows + Web with the new Windows Live.
http://www.windowslive.com?ocid=TXT_TAGHM_Wave2_powerofwindows_012008