Cgs synth

> Now this is wrong. Tested the second VCO (had the correct TL0__
> device in place!) and get the same result as the first. VCO core

> fine - actually works very well! The sawtooth from the core
> completely goes away at the pin 1 of the TL072 for the saw

> I checked for a simple short to ground, but no such luck. Cap
> polarity is correct and the TL072 has correct voltage at pins 4

> 8.
>
> Another oddity - the sub input and output work as expected. But

> I plug my square wave audio into the square wave out jack, which

> connected to the sub input when no plug is in the sub in,

> is halved!
>
> This is really odd. How can such a simple stage as the saw and
> square output amplifier be causing me so much grief? Has anyone
> else built the rev .3 pcb? When I get a chance, I'm going to

> the traces. In the meantime, I'm going to try to calm down.
>
> Any ideas?
>
> Chub

>Now I'm getting someplace!
>
>I've got a perfect sawtooth up to the pin 2 of the saw output
>opamp. 15 volts DC at pin 1. I disconnected the 330R resistor,
>expecting to see zero vdc at pin 7. Measured about 10vdc instead!
>+15 vdc at pin 8 and -15vdc at pin 4.
>
>Also, If I plug into the shape CV input I can hear (and see) the
>same signal somewhat "shaped" That means everything is doing what
>I'd expect *except* the TL072 (which has been replaced twice now
>from different stock) for the saw and square ouput. I've put the
>600K/200K ohm resistors (600K in the feedback/200K to ground from
>the input) on the saw stage for +-5 volt swing.
>
>Everything seems okay in the traces. What am I doing wrong? Is the
>47mfd cap to be removed? Has anyone else built a rev 3 pcb?
>
>Ken?
>
>Gee, don't tell my employer about this!
>
>Chub
>
>--- In cgs_synth@yahoogroups.com, "charlesosthelder"
><osthelder@n...> wrote:
>> Now this is wrong. Tested the second VCO (had the correct TL0__
>> device in place!) and get the same result as the first. VCO core
>is
>> fine - actually works very well! The sawtooth from the core
>> completely goes away at the pin 1 of the TL072 for the saw
>output.
>> I checked for a simple short to ground, but no such luck. Cap
>> polarity is correct and the TL072 has correct voltage at pins 4
>and
>> 8.
>>
>> Another oddity - the sub input and output work as expected. But
>if
>> I plug my square wave audio into the square wave out jack, which
>is
>> connected to the sub input when no plug is in the sub in,
>frequency
>> is halved!
>>
>> This is really odd. How can such a simple stage as the saw and
>> square output amplifier be causing me so much grief? Has anyone
>> else built the rev .3 pcb? When I get a chance, I'm going to
>follow
>> the traces. In the meantime, I'm going to try to calm down.
>>
>> Any ideas?
>>
>> Chub
>
>
>
>
>
>See the following URLS for the CGS Modular Synth home page:
>Main: http://www.cgs.synth.net/
>Secondary: http://otherunicorn.0catch.com/synth/
>Yahoo! Groups Links
>
>
>
>
>
>
>

--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
> All I can say is you have me stumped! I've not heard anythng like
this
> before, and I've sold dozens of these.
>
> Ken
>
> >Now I'm getting someplace!
> >
> >I've got a perfect sawtooth up to the pin 2 of the saw output
> >opamp. 15 volts DC at pin 1. I disconnected the 330R resistor,
> >expecting to see zero vdc at pin 7. Measured about 10vdc
instead!
> >+15 vdc at pin 8 and -15vdc at pin 4.
> >
> >Also, If I plug into the shape CV input I can hear (and see) the
> >same signal somewhat "shaped" That means everything is doing
what
> >I'd expect *except* the TL072 (which has been replaced twice now
> >from different stock) for the saw and square ouput. I've put the
> >600K/200K ohm resistors (600K in the feedback/200K to ground from
> >the input) on the saw stage for +-5 volt swing.
> >
> >Everything seems okay in the traces. What am I doing wrong? Is
the
> >47mfd cap to be removed? Has anyone else built a rev 3 pcb?
> >
> >Ken?
> >
> >Gee, don't tell my employer about this!
> >
> >Chub
> >
> >--- In cgs_synth@yahoogroups.com, "charlesosthelder"
> ><osthelder@n...> wrote:
> >> Now this is wrong. Tested the second VCO (had the correct
TL0__
> >> device in place!) and get the same result as the first. VCO
core
> >is
> >> fine - actually works very well! The sawtooth from the core
> >> completely goes away at the pin 1 of the TL072 for the saw
> >output.
> >> I checked for a simple short to ground, but no such luck. Cap
> >> polarity is correct and the TL072 has correct voltage at pins 4
> >and
> >> 8.
> >>
> >> Another oddity - the sub input and output work as expected.
But
> >if
> >> I plug my square wave audio into the square wave out jack,
which
> >is
> >> connected to the sub input when no plug is in the sub in,
> >frequency
> >> is halved!
> >>
> >> This is really odd. How can such a simple stage as the saw and
> >> square output amplifier be causing me so much grief? Has
anyone
> >> else built the rev .3 pcb? When I get a chance, I'm going to
> >follow
> >> the traces. In the meantime, I'm going to try to calm down.
> >>
> >> Any ideas?
> >>
> >> Chub
> >
> >
> >
> >
> >
> >See the following URLS for the CGS Modular Synth home page:
> >Main: http://www.cgs.synth.net/
> >Secondary: http://otherunicorn.0catch.com/synth/
> >Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
>
_____________________________________________________________________
__
> Ken Stone sasami@h... or sasami@c...
> Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/>
> Australian Miniature Horses & Ponies
<http://www.blaze.net.au/~sasami/>

> -----Original Message-----
> From: charlesosthelder [mailto:osthelder@...]
> Sent: Monday, June 06, 2005 8:05 PM
> To: cgs_synth@yahoogroups.com
> Subject: [cgs_synth] Re: VCO weirdness
>
> Now I'm getting someplace!
>
> I've got a perfect sawtooth up to the pin 2 of the saw output
> opamp. 15 volts DC at pin 1. I disconnected the 330R resistor,
> expecting to see zero vdc at pin 7. Measured about 10vdc instead!
> +15 vdc at pin 8 and -15vdc at pin 4.
>
> Also, If I plug into the shape CV input I can hear (and see) the
> same signal somewhat "shaped" That means everything is doing what
> I'd expect *except* the TL072 (which has been replaced twice now
> from different stock) for the saw and square ouput. I've put the
> 600K/200K ohm resistors (600K in the feedback/200K to ground from
> the input) on the saw stage for +-5 volt swing.
>
> Everything seems okay in the traces. What am I doing wrong? Is the
> 47mfd cap to be removed? Has anyone else built a rev 3 pcb?
>
> Ken?
>
> Gee, don't tell my employer about this!
>
> Chub
>
> --- In cgs_synth@yahoogroups.com, "charlesosthelder"
> <osthelder@n...> wrote:
> > Now this is wrong. Tested the second VCO (had the correct TL0__
> > device in place!) and get the same result as the first. VCO core
> is
> > fine - actually works very well! The sawtooth from the core
> > completely goes away at the pin 1 of the TL072 for the saw
> output.
> > I checked for a simple short to ground, but no such luck. Cap
> > polarity is correct and the TL072 has correct voltage at pins 4
> and
> > 8.
> >
> > Another oddity - the sub input and output work as expected. But
> if
> > I plug my square wave audio into the square wave out jack, which
> is
> > connected to the sub input when no plug is in the sub in,
> frequency
> > is halved!
> >
> > This is really odd. How can such a simple stage as the saw and
> > square output amplifier be causing me so much grief? Has anyone
> > else built the rev .3 pcb? When I get a chance, I'm going to
> follow
> > the traces. In the meantime, I'm going to try to calm down.
> >
> > Any ideas?
> >
> > Chub
>
>
>
>
>
> See the following URLS for the CGS Modular Synth home page:
> Main: http://www.cgs.synth.net/
> Secondary: http://otherunicorn.0catch.com/synth/
> Yahoo! Groups Links
>
>
>
>
>
>
>

--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
> All I can say is you have me stumped! I've not heard anythng like
this
> before, and I've sold dozens of these.
>
> Ken
>
> >Now I'm getting someplace!
> >
> >I've got a perfect sawtooth up to the pin 2 of the saw output
> >opamp. 15 volts DC at pin 1. I disconnected the 330R resistor,
> >expecting to see zero vdc at pin 7. Measured about 10vdc
instead!
> >+15 vdc at pin 8 and -15vdc at pin 4.
> >
> >Also, If I plug into the shape CV input I can hear (and see) the
> >same signal somewhat "shaped" That means everything is doing
what
> >I'd expect *except* the TL072 (which has been replaced twice now
> >from different stock) for the saw and square ouput. I've put the
> >600K/200K ohm resistors (600K in the feedback/200K to ground from
> >the input) on the saw stage for +-5 volt swing.
> >
> >Everything seems okay in the traces. What am I doing wrong? Is
the
> >47mfd cap to be removed? Has anyone else built a rev 3 pcb?
> >
> >Ken?
> >
> >Gee, don't tell my employer about this!
> >
> >Chub
> >
> >--- In cgs_synth@yahoogroups.com, "charlesosthelder"
> ><osthelder@n...> wrote:
> >> Now this is wrong. Tested the second VCO (had the correct
TL0__
> >> device in place!) and get the same result as the first. VCO
core
> >is
> >> fine - actually works very well! The sawtooth from the core
> >> completely goes away at the pin 1 of the TL072 for the saw
> >output.
> >> I checked for a simple short to ground, but no such luck. Cap
> >> polarity is correct and the TL072 has correct voltage at pins 4
> >and
> >> 8.
> >>
> >> Another oddity - the sub input and output work as expected.
But
> >if
> >> I plug my square wave audio into the square wave out jack,
which
> >is
> >> connected to the sub input when no plug is in the sub in,
> >frequency
> >> is halved!
> >>
> >> This is really odd. How can such a simple stage as the saw and
> >> square output amplifier be causing me so much grief? Has
anyone
> >> else built the rev .3 pcb? When I get a chance, I'm going to
> >follow
> >> the traces. In the meantime, I'm going to try to calm down.
> >>
> >> Any ideas?
> >>
> >> Chub
> >
> >
> >
> >
> >
> >See the following URLS for the CGS Modular Synth home page:
> >Main: http://www.cgs.synth.net/
> >Secondary: http://otherunicorn.0catch.com/synth/
> >Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
>
_____________________________________________________________________
__
> Ken Stone sasami@h... or sasami@c...
> Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/>
> Australian Miniature Horses & Ponies
<http://www.blaze.net.au/~sasami/>

>
>> The 200k is providing an offset while the 600k is providing the
>gain -
>> supposedly. These aren't the values I specify.
>>
>
>That's precisely what I'm going to look at tonight. With a solid 2
>1/2 volt saw from the core, I don't need a gain of 6. Also, as I'm
>seeing the positive rail at the output of an inverting amp, that must
>mean the offset resistor is too low. Perhaps these two resistors
>were to be the other way around!
>
>By the way, Ken, I've been playing with the core of this VCO. When I
>get this sorted out, these VCO's will see some heavy usage! A very
>nice design, in my opinion. Easy to set up, lot's of modulation
>possibilities, the sub oscillator and the VC saw/sine shaper which is
>really the icing on the cake.
>
>To everyone on the list- this is really MY error, not the pcb or the
>design. And it may seem like I've been working on this for a long
>time, but that's because I don't really get enough time to work on
>it - a few minutes here and there. Thanks for your suggestions and
>ideas! Buy lots of Ken's VCO's, too.
>
>Chub
>
>
>
>
>
>See the following URLS for the CGS Modular Synth home page:
>Main: http://www.cgs.synth.net/
>Secondary: http://otherunicorn.0catch.com/synth/
>Yahoo! Groups Links
>
>
>
>
>
>
>