[sdiy] panning vca

Tue Mar 1 00:35:54 CET 2016

Also, if your lead with the cap soldered to the end you're using as a probe
is only grounded at the connector end, this could erroneously be telling
you that there is noise present when in fact there actually isn't. I'd
recommend using a cheap scope probe instead, and grounding the probe end
with the flying lead as close as possible to the signal you're actually
probing. Years ago when I did a lot of audio design, I modded a hifi
amplifier by adding a BNC socket to its front panel so I could plug a scope
probe (or any other bit of my usual BNC plumbing) right into the amplifier
so I could listen to what was going on rather than just see it on a scope.

On the subject of the power supply, it should work pretty well. It doesn't
have any RF interference filtering, however, so that *could* be an issue if
you're close to something that radiates significantly.

Sarah

On Mon, Feb 29, 2016 at 3:08 PM, Tom Bugs <admin at bugbrand.co.uk> wrote:

> 10u to 220u between V+ and 0V and between 0V and V- where power comes in
> (filter caps) - watch polarity, of course.
> 100n between V+ and 0V and between 0V and V- as close to the power pins of
> each IC.
>
>
> On 29/02/2016 22:03, Joe wrote:
>
>> Tom, No. As I stated I am strictly monkey see, monkey do. Trying to
>> change that. I am going to get a book, now.  Ray Wilson's "Make: Analog
>> Synthesizers" was recommended.
>>   Can you tell me what to add where? Thanks.
>> Joe.
>>
>>
>>
>>
>>
>> On Mon, 2016-02-29 at 21:34 +0000, Tom Bugs wrote:
>>
>>> Question - do you have filter & bypass caps on the circuits? They're not
>>> shown in the original schematic.
>>>
>>>
>>> On 29/02/2016 17:06, Joe wrote:
>>>
>>>> Hello and thanks. My power supply is the bipolar power supply circuit
>>>> provided by General Guitar Gadgets found here
>>>>
>>>> http://www.generalguitargadgets.com/wp-content/uploads/ggg_bipolar_ps.pdf
>>>> I have used it before but for other circuits that generate cv. There
>>>> never seemed to be noticeable downstream noise in the audio in those
>>>> circuits. Those circuits were the EFM pv-1 and an envelope circuit Harry
>>>> Bissell sent me, also EFM I bet. I used 3080s in those, too. I find the
>>>> same noise where the ground is connected from the bipolar power supply
>>>> board to the panning vca board, by the way.
>>>>    My audio probe is a 0.1uf cap on the tip of an audio cable with the
>>>> audio cable shield connected to ground.
>>>>    So, before I try to use a LM13700, is there some procedure I can use
>>>> to
>>>> determine the noise source. Removing ICs and powering up or something
>>>> like that?
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Mon, 2016-02-29 at 15:06 +0100, Rutger Vlek wrote:
>>>>
>>>>> The CA3080 is known to be a bit noisy, but if you find it everywhere
>>>>> (even in the ground) I'd do a more fundamental check on your power supply
>>>>> and measurement setup.
>>>>>
>>>>> How do you supply the board with power? How do you do the audio trace
>>>>> exactly? Just to be sure that the noise is actually in the board, not in
>>>>> the measurement method :).
>>>>>
>>>>> Rutger
>>>>>
>>>>>
>>>>>
>>>>> On 29 feb 2016, at 03:46, Joe wrote:
>>>>>
>>>>> Hello there, I built this panning VCA and I am happy with how it sounds
>>>>>> except there is a lot of background noise. I tried to audio trace the
>>>>>> noise but I find it everywhere, even in the ground plane. Is there
>>>>>> some
>>>>>> advice that someone can give me about how to isolate it. Thanks.
>>>>>>
>>>>>> On Sat, 2016-01-23 at 12:58 -0500, Joe wrote:
>>>>>>
>>>>>>> Thanks to all! You guys are the awsomest ever! Joe.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Fri, 2016-01-22 at 16:13 -0500, Joe wrote:
>>>>>>>
>>>>>>>> I am planning on building this single as a panning VCA by Richard
>>>>>>>> Curcio.
>>>>>>>>
>>>>>>>> http://www.sdiy.org/richardc64/mmvca/index.html
>>>>>>>>
>>>>>>>> I can source a CA3080 and since I am only building one I am not
>>>>>>>> worried
>>>>>>>> about expense. Here's the thing, I don't know what pot values to
>>>>>>>> use for
>>>>>>>> the trimmers and I am definitely thrown by the current controlling
>>>>>>>> DC
>>>>>>>> trimmer, though I understand how to wire it. Can anyone take a
>>>>>>>> minute(or
>>>>>>>> few) to help me figure them out? Thanks, Joe.
>>>>>>>>
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>>
>>
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