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wintermute303
Joined: Sep 08, 2009 Posts: 3 Location: Germany
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Posted: Tue Sep 08, 2009 5:46 am Post subject:
ARP 2600 VCO |
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Hi there,
I am new to this board but have been reading posts for a while.
I started a small ARP 2600 project inspired by Andy and his great dual odyssey VCO clone. Now I have some questions regarding the ARP 2600 VCOs since they seem to be different from the Odyssey ones.
As far as I understand the odyssey uses 0 to 6 Volts for the saw wave and 0 to 5 Volts for the square while the 2600 has 10 Volts peak to peak. I simulated the ARP 2600 circuit and found the Voltage of the saw to be 0 to 10 Volts. Can anyone verify this to be correct? After doing some research I thought the 2600 VCO centers around 0 with +5 to -5 Volts. I am confussed ...please help. |
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Broadwave
Joined: Feb 16, 2007 Posts: 347 Location: Manchester UK
Audio files: 6
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Posted: Tue Sep 08, 2009 9:54 am Post subject:
Re: ARP 2600 VCO |
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wintermute303 wrote: | I simulated the ARP 2600 circuit and found the Voltage of the saw to be 0 to 10 Volts. Can anyone verify this to be correct? After doing some research I thought the 2600 VCO centers around 0 with +5 to -5 Volts. I am confussed ...please help. |
The saw output from the 2600 VCO module is 0-10v. For VCO 1 & 3 this signal is sent to the Square/Pulse converters which also output 0-10v.
The saw output from VCO 2 goes to the wave shapers which gives you Square/PWM 0-10v, Triangle +/-5v and sine +/- 5v.
But basically the core VCO's for the 2600 and MKII/III Odysseys are the same, except for a few resistor value changes.
I've just completed an Odyssey VCO using discrete transistors (I have loads of spare 3904/06's hanging around), and works just as well as using the CA3086, and takes up less room! _________________ Kronos 2-88, Kronos 61, Studiologic Sledge V2/SL, Broadwave ARP 2600EX, Broadwave 18U ARP based Eurorack Modular, Broadwave Minimoog Clone, GEM S2 Turbo.
Synth DIY Projects
Musical Doodlings |
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wintermute303
Joined: Sep 08, 2009 Posts: 3 Location: Germany
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Posted: Tue Sep 08, 2009 12:22 pm Post subject:
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Hi Andy,
thanks for your reply. So what I tried today was to get the saw-wave to 0-10Volts using the level shifter you posted in another thread. I was able to raise the wave but when I use is as input for the wave shaper board of the 2600 I have no chance to get a -5 to +5 Volts Sine or Triangle. If I use a 5 Volts saw signal I am able to get 10Vpp for the sine but only about 5Vpp for the triangle. The sine also does not sound like a clean sine wave and the triangle has a little spike on top. Is there something wrong circuitwise or is it the input signal? Do you know which resistors I should change to convert the odyssey VCO to a 2600 one? Thanks for your advise.
(By the way I am able to get a clean sine wave but only when ignoring tuning to 10Vpp...its more like -7.5V and and 2.5V) |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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steffensen
Joined: Jul 11, 2012 Posts: 103 Location: Sweden
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Posted: Thu Jun 12, 2014 1:56 am Post subject:
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The Tri is suppose to look like that. Also, the Sine is pretty much a Tri with rounded corners if you use the 2N3954.
However, if you match up 2x 2N5459's instead, it can be made in to a pretty decent Sine. |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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Posted: Thu Jun 12, 2014 3:24 am Post subject:
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hi steffensen.
i have a perfect sine wave.
what bothers me is the tri top spike going inside the tri.
have you seen the pics?
this is before trimming:
this is after trimming:
you say the top spike of the tri suppose to look like that?
i dont mind if it look like that but i can hear it, thats annoying!
its not a pure Tri sound, the small spike is hearble. _________________ http://www.myspace.com/mgmtrance |
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steffensen
Joined: Jul 11, 2012 Posts: 103 Location: Sweden
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Posted: Thu Jun 12, 2014 3:26 am Post subject:
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Hi there Isak
Yes, thats how the 2600 Tri looks like indeed. Part of its sound, which i love! |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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Posted: Thu Jun 12, 2014 3:36 am Post subject:
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thanks man
BTW the THeff design is like the original 2600 VCO schematics.
i followed the scheme and his PCB design.
he he only replaced the single opamp LM301 with dual opamp for the wave shapes as well as the transistors like Andy did in his design.
and your right, amazing sound!
_________________ http://www.myspace.com/mgmtrance |
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