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 Forum index » DIY Hardware and Software
DIY Synths General Discussion
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zipzap



Joined: Nov 22, 2005
Posts: 559
Location: germany
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PostPosted: Mon May 08, 2006 8:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Buffering is my next topic for those little things: If i plug my sequencer into the vco and the vcf the pitch drops a little. Did i miss something there? The cv out of the sequencer is a Tl084 going into a 100k Pot voltage divider. The cv ins are Pot voltage dividers (47k or 100k) going to tl084s again. I guess i should buffer the Inputs first, or the seq out (after the pot), or all of them. I just thought an Opamp could handle such a thing. How do you do that?
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piedwagtail



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PostPosted: Mon May 08, 2006 8:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, cv pot then TL084.
But don't expect miracles.....you can see why everyone was so eager to go digital in electronics in the late 70s!
I've got two Oberheim SEMs that when patched behave similiarly,droop....

I spoke with my father about this,he was a radar engineer back then and he was describing how the oscillators for missile tracking radars,had special separate power supplies and were severely isolated to stop such interference.And if you know anything about the Falklands war,they were pretty hopeless anyrate!

Robert
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elektro80
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PostPosted: Mon May 08, 2006 9:07 am    Post subject: Reply with quote  Mark this post and the followings unread

piedwagtail wrote:

I've got two Oberheim SEMs that when patched behave similiarly,droop....


You are quite right. I think this issue has been mentioned several times here way back. Modular synthesis often gives the impression of being a Lego approach to building sounds, which it isn´t. The circuitry will more or less change its properties depending on what you connect or which parameters you are tweaking. It was quite common that certain patches never quite worked like they should. Certain combinations of modules and parameters would often prove to be useless. Patching was often as much about workarounds than simply building a sound.

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zipzap



Joined: Nov 22, 2005
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PostPosted: Mon May 08, 2006 10:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, cv pot then TL084 - that´s talking of the cv out i guess. (the sequencer is in fact the only module that has a "voltage pot". All others only have input attenuators, so then it´s the other way around.
Ok, i don´t want to bring this old subject up again, i just thought i was doing something wrong.
Quote:
The circuitry will more or less change its properties depending on what you connect or which parameters you are tweaking.

Maybe thats what makes analog sounds so great! It´s like a human. If i practise a pice today and play it tomorrow things will sound different too.
The Voltage drop just suprised me, because i don´t really know about electronics, and i always think of the perfect Opamp as being real. Of course, it must be a difference for any opamp if the load changes from 100k to 30k...
But in this case i still expect some kind of miracle from buffering all the ins and outs. I mean thats what buffers are for, right?
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piedwagtail



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PostPosted: Mon May 08, 2006 11:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
But in this case i still expect some kind of miracle from buffering all the ins and outs. I mean thats what buffers are for, right?

except the chip engineers didn't reckon on the stringent appreciation of the ear for pitch when controlled by an embattled CV!

soon we'll be discussing intonation problems with clarinet makers..... Very Happy

you may even have to resort to a s/h in there somewhere,i've given up on voltage divider controlled sequential pitch cv in preference for the sort of d/a used in midi/cv converters.

I understand your frustration ...

Quote:
because i don´t really know about electronics,


i'd say(including this problem's resolving)you are already in the 1% of the population who do know,the 0.00001% who love part of the subject so much it is really second nature are few and far between.And i'd swear they all agree with Uncle K's fine dictum,the wiser you are the more uncertainty you accept.

So pick up your sword,i mean,soldering iron!

Robert
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Uncle Krunkus
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Joined: Jul 11, 2005
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PostPosted: Tue May 09, 2006 1:29 am    Post subject: Reply with quote  Mark this post and the followings unread

BTW, that was a quote from Monkey Magic. Very Zen. Sometimes though Zen gives way to DEVO. Still, I've stayed with the monkey theme! Wink
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