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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Newbie seeking advice
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teddexter



Joined: Feb 27, 2009
Posts: 9
Location: Leicester

PostPosted: Wed Jun 17, 2009 2:39 am    Post subject: Newbie seeking advice
Subject description: preamp for external audio
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Hi,

I am new and have been looking around here at some useful circuits and found it an excellent resource. I want to be able to get my lunetta type synth driven by audio (ie audio source -->preamp ---> gating Cd4093 oscillators) and also want to get a strong signal to my transformer/diode (real ringmod circuit as seen on this forum and elsewhere).

I have seen this topic and the Cd4069 is mentioned as preamp. I wondered if this was a mistype as the Nic Collins book mentioned uses CD4049.

http://electro-music.com/forum/viewtopic.php?highlight=preamp&t=25699

The 4049 as a preamp does the job but in a pretty harsh distorted way which I rather like.

http://books.google.co.uk/books?id=P1yEOTci8DMC&pg=PA151&lpg=PA151&dq=CD4049+preamp&source=bl&ots=-Jvf-5nZYi&sig=g9ZgDrj2-vTsfnuaT1e4eiAbWoU&hl=en&ei=brk4SszyJca7jAeBntmADg&sa=X&oi=book_result&ct=result&resnum=1

Also generally wondered if there are any nice, really simple and effective preamp circuits, that would give me a lot of boost to drive these things. Op amps considered also.

Cheers
Ted

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slacker



Joined: Nov 18, 2007
Posts: 301
Location: England
Audio files: 11
G2 patch files: 1

PostPosted: Wed Jun 17, 2009 10:50 am    Post subject: Reply with quote  Mark this post and the followings unread

Welcome aboard Smile

CD4049s and CD4069s are very similar so most of the time if a design uses one you can substitute the other, especially using them for audio. The chips are physically different, so aren't directly interchangeable, but if you're making your own layouts that's not a problem.

To drive CMOS chips you need to get the signal up to a level where's it's swinging between ground and whatever the supply voltage is. You might be able to do that by sticking a couple of CD4049/4069 stages in series.

A really easy way to do it is to use an LM386 as a preamp that will easily drive CMOS chips. Have a look at the PWM from here as an example.

If you don't mind using opamps, I designed an octave down pedal that used an opamp front end to drive a CMOS divider chip. The schematic and stuff is here. Just use the first 3 opamp stages, the first one gives a nice boost, the second filters the signal to improve tracking and the third stage is a comparator to give a nice solid square wave signal to drive the CMOS.

Hope that helps Smile
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teddexter



Joined: Feb 27, 2009
Posts: 9
Location: Leicester

PostPosted: Thu Jun 18, 2009 12:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Slacker the LM386 circuit looks to be right up my street as its simple. The Nicolas Collins book gives an example of LM386 power amp and I wasn't sure if it would be too powerful as a preamp (somehow) so I'm sure that will give the necessary "oomph" required. I'll give this one a go and report back (like the pwm feature too). Your second link seems to have expired though (have you got another source for that?).
Cheers
Ted
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teddexter



Joined: Feb 27, 2009
Posts: 9
Location: Leicester

PostPosted: Thu Jun 18, 2009 1:11 am    Post subject: Also Reply with quote  Mark this post and the followings unread

Also Nicolas Collins book talks about using CD4040 for octave divisions of a guitar fed into a 4049 for example (his circuits are very lunettarie), which is pretty cool, but was wondering if there is an easy way to divide the frequency to get notes other than an octave apart and even turn notes into chords. I suspect I may be getting into somewhat trickier territory here.
Ted
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teddexter



Joined: Feb 27, 2009
Posts: 9
Location: Leicester

PostPosted: Thu Jun 18, 2009 7:28 am    Post subject: Reply with quote  Mark this post and the followings unread

That post for the octave pedal is working now thanks. Also nice and straightforward. I geuss I could use just the first two stages even and get something that sounds rougher. I kind of like noise sounds. I'll let you know what I go with.
Cheers
Ted
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slacker



Joined: Nov 18, 2007
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PostPosted: Thu Jun 18, 2009 10:33 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't know what was up with the link, it wouldn't work for me earlier either.
Here's a direct link to the schematic in case it goes funny again http://www.eskimo.plus.com/fxstuff/slacktave.png

If you want non octave divisions you can use a CD4017 counter, with that you can get 1 and 2 octaves down and 1 and 2 octaves + a 4th below.
If you want other divisions it gets trickier, you need to multiply up the signal and then divide it.
There's some posts here somewhere about doing it.
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teddexter



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Location: Leicester

PostPosted: Fri Jun 19, 2009 1:10 am    Post subject: Reply with quote  Mark this post and the followings unread

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slacker



Joined: Nov 18, 2007
Posts: 301
Location: England
Audio files: 11
G2 patch files: 1

PostPosted: Fri Jun 19, 2009 1:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah you're right it could Smile

A while ago I tried hooking my guitar up to my Lunetta which has a version of the "multidivide" circuit it in and it does sound a bit like an arpeggiator.
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