[sdiy] help getting VCO levels down to MN32XX BBD size

Tom Wiltshire tom at electricdruid.net
Wed Sep 16 00:38:21 CEST 2009 

Dan,

The MN3207 datasheet gives a distortion figure of 0.4% with  
(presumably typical) input level of 250mV, and gives an input signal  
swing of 360mV. This is roughly a quarter or a third of a volt, which  
means that something is fishy somewhere. You're sticking in +/-10V,  
which is a 20V range, so a reduction of 60-80 to 1 ought to do it.

Did you just stick the attenuator in front of the input amp? That's  
got some gain, and would account for the discrepancy.

I'd think that cutting the level down with an active op-amp stage  
would be preferable, since you could put some capacitors in it and  
make it into an active filter to help trim the high frequencies going  
into the delay line (an anti-aliasing filter).

HTH,
T.

On 13 Sep 2009, at 06:20, Dan Snazelle wrote:

>
>
> well
>
> after looking at ken stones circuits and a few others and trying  
> them unsuccessfully, I decided i had only myself to blame.
>
> kens circuit is great and
>
> normally a 20 to 1 reduction would be great and works fine for  
> interfacing stompboxes.
>
> but i am trying to interface with specific chip.
>
> SO i thought about it and tried changing the ratio to something  
> radical.
>
> i found that i needed a 200 to 1 reduction!!
>
> all is well now
>
> thanks so much
>
>
>
> --------------------------------------------
> check out various dan music at:
>
> http://www.myspace.com/lossnyc
>
> (updated monthly)
>
> http://www.soundclick.com/lossnyc.htm
>
>
>
> http://www.indie911.com/dan-snazelle
>
> (or for techno) http://www.myspace.com/snazelle
>
> ALSO check out Dan synth/Fx projects:
>
> AUDIO ARK:
>
> www.youtube.com/watch?v=TJRpvaOcUic
>
> www.youtube.com/watch?v=BqIa_lXQNTA&feature=channel_page
>
> www.youtube.com/watch?v=V4nJPjGgOcU&feature=channel_page
>
> and soundtrack/design work:
>
> NEW: check out Dan's sound design from the 1998 award winning film  
> SAFARI by catherine chalmers
>
> http://www.catherinechalmers.com/videos.cfm
>
>
>
>
>
>
> ----------------------------------------
>> Date: Sat, 12 Sep 2009 21:29:49 -0700
>> From: dixon at interchange.ubc.ca
>> Subject: RE: [sdiy] help getting VCO levels down to MN32XX BBD size
>> To: subjectivity at hotmail.com; guitaricon at verizon.net; synth- 
>> diy at dropmix.xs4all.nl
>>
>> OK, Dan, I don't profess to understand this circuit (I haven't  
>> tried using
>> BBDs or PLLs yet), but I think I can offer some advice about your  
>> finicky
>> bias:
>>
>> Don't try to set a bias by putting a trimmer between two rails.  
>> Pretend you
>> can get the exact voltage you want with a divider (i.e., two specific
>> resistors), build that divider, and then put a small-value trimmer in
>> between. Then the trimmer won't be too touchy.
>>
>> For example, if you need 5.2V and your rails are 9V and 0V, then  
>> you need
>> two resistors in a ratio of 3.8/5.2. 22k/30k would work nicely.  
>> Then, put
>> a 2k trimmer in between and take your bias from the tap. The  
>> trimmer will
>> now have a range of 5V to 5.33V. If it's a multi-turn trimmer,  
>> then you
>> should be able to find your magic bias point easily.
>>
>>
>>> for further refrence you could look at the MN3207 zombie chorus
>>>
>>>
>>> http://www.synthdiy.com/files/2007/zombie_chorus_mn3207_based.jpg
>>> --------------------------------------------
>>> check out various dan music at:
>>>
>>> http://www.myspace.com/lossnyc
>>>
>>> (updated monthly)
>>>
>>> http://www.soundclick.com/lossnyc.htm
>>>
>>>
>>>
>>> http://www.indie911.com/dan-snazelle
>>>
>>> (or for techno) http://www.myspace.com/snazelle
>>>
>>> ALSO check out Dan synth/Fx projects:
>>>
>>> AUDIO ARK:
>>>
>>> www.youtube.com/watch?v=TJRpvaOcUic
>>>
>>> www.youtube.com/watch?v=BqIa_lXQNTA&feature=channel_page
>>>
>>> www.youtube.com/watch?v=V4nJPjGgOcU&feature=channel_page
>>>
>>> and soundtrack/design work:
>>>
>>> NEW: check out Dan's sound design from the 1998 award winning  
>>> film SAFARI
>>> by catherine chalmers
>>>
>>> http://www.catherinechalmers.com/videos.cfm
>>>
>>>
>>>
>>>
>>>
>>>
>>> ----------------------------------------
>>>> Date: Sat, 12 Sep 2009 18:00:22 -0700
>>>> From: dixon at interchange.ubc.ca
>>>> Subject: RE: [sdiy] help getting VCO levels down to MN32XX BBD size
>>>> To: subjectivity at hotmail.com; guitaricon at verizon.net; synth-
>>> diy at dropmix.xs4all.nl
>>>>
>>>> All Ken Stone's module does to the synth level output is  
>>>> attenuate it by
>>> a
>>>> factor of 22 across a divider and send it to the effect, and  
>>>> then re-
>>> amplify
>>>> the signal from the effect by the same factor in a non-inverting  
>>>> opamp
>>> and
>>>> send it back into the synth. There are some ac coupling  
>>>> capacitors and a
>>>> few other bells and whistles, but basically its pretty simple. I  
>>>> don't
>>> know
>>>> why this wouldn't work for what you want to do.
>>>>
>>>> Also, I don't understand what you mean by "adding the proper  
>>>> bias". What
>>> is
>>>> this bias, and why do you need to add it? Does the flanger  
>>>> output have a
>>> dc
>>>> component (i.e., is it not centred about 0V)? Granted, I  
>>>> couldn't make
>>>> heads or tails out of your "back o' the napkin" schematic, so  
>>>> there's
>>>> probably something I'm missing.
>>>>
>>>>
>>>>> not sure if that will work stock as that is for using LINE with an
>>> effects
>>>>> chain. (i think that is why there is a 1m to ground)
>>>>>
>>>>> that is not my intention.
>>>>>
>>>>> i want to solder this up as a module for my modular
>>>>>
>>>>>
>>>>> also, I am interested in how I need to modify any filtering for  
>>>>> a line
>>>>> level.
>>>>>
>>>>> the main issues i have had so far with trying to use a simple  
>>>>> neg gain
>>> and
>>>>> offset opamp is that unless I add the proper Bias, it does not  
>>>>> seem to
>>>>> work with the rest of the circuit.
>>>>>
>>>>> maybe I need to just keep trying things!
>>>>>
>>>>> thanks
>>>>>
>>>>>
>>>>>
>>>>> ----------------------------------------
>>>>>> From: guitaricon at verizon.net
>>>>>> To: synth-diy at dropmix.xs4all.nl
>>>>>> Subject: Re: [sdiy] help getting VCO levels down to MN32XX BBD  
>>>>>> size
>>>>>> Date: Sat, 12 Sep 2009 19:41:24 -0400
>>>>>>
>>>>>> Ken Stone's Stomp Box Adapter?
>>>>>>
>>>>>> http://www.cgs.synth.net/modules/cgs60_sba.html
>>>>>>
>>>>>>
>>>>>>
>>>>>> ----- Original Message -----
>>>>>> From: "Dan Snazelle"
>>>>>> To:
>>>>>> Sent: Saturday, September 12, 2009 7:19 PM
>>>>>> Subject: [sdiy] help getting VCO levels down to MN32XX BBD size
>>>>>>
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> i got a very basic flanger working
>>>>>>>
>>>>>>> http://electro-music.com/forum/phpbb-
>>>>> files/snazzy_simple_test_flanger_162.jpg
>>>>>>>
>>>>>>> however it only works with Guitar signals
>>>>>>>
>>>>>>> In order to get it to work with +/- 10 volts and +/- 5volt  
>>>>>>> signals,
>>>>> what
>>>>>>> can I add to the front end??
>>>>>>>
>>>>>>> in most cases I would just level shift, etc But this signal  
>>>>>>> needs to
>>> be
>>>>>>> TINY (lets say .50 volts peak to peak)
>>>>>>>
>>>>>>> so far I cant find anyone that does this without a compander.
>>>>>>>
>>>>>>> any ideas, schematics or links appreciated
>>>>>>>
>>>>>>>
>>>>>>> thanks so much
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --------------------------------------------
>>>>>>> check out various dan music at:
>>>>>>>
>>>>>>> http://www.myspace.com/lossnyc
>>>>>>>
>>>>>>> (updated monthly)
>>>>>>>
>>>>>>> http://www.soundclick.com/lossnyc.htm
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> http://www.indie911.com/dan-snazelle
>>>>>>>
>>>>>>> (or for techno) http://www.myspace.com/snazelle
>>>>>>>
>>>>>>> ALSO check out Dan synth/Fx projects:
>>>>>>>
>>>>>>> AUDIO ARK:
>>>>>>>
>>>>>>> www.youtube.com/watch?v=TJRpvaOcUic
>>>>>>>
>>>>>>> www.youtube.com/watch?v=BqIa_lXQNTA&feature=channel_page
>>>>>>>
>>>>>>> www.youtube.com/watch?v=V4nJPjGgOcU&feature=channel_page
>>>>>>>
>>>>>>> and soundtrack/design work:
>>>>>>>
>>>>>>> NEW: check out Dan's sound design from the 1998 award winning  
>>>>>>> film
>>>>> SAFARI
>>>>>>> by catherine chalmers
>>>>>>>
>>>>>>> http://www.catherinechalmers.com/videos.cfm
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Synth-diy mailing list
>>>>>>> Synth-diy at dropmix.xs4all.nl
>>>>>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>>>>>
>>>>>> _______________________________________________
>>>>>> Synth-diy mailing list
>>>>>> Synth-diy at dropmix.xs4all.nl
>>>>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>>>>
>>>>> _______________________________________________
>>>>> Synth-diy mailing list
>>>>> Synth-diy at dropmix.xs4all.nl
>>>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>>>
>>
>
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