[sdiy] converting a 10v p to p to a 0-5 volt signal

[Tom Wiltshire]

That's basically the same circuit I posted. The second part is the  
active rectifier, the first part (inverting mixer) has the addition  
of a zener for overvoltage protection.

T.

On 21 May 2009, at 01:14, Dan Snazelle wrote:

>
> Ok
>
> i noticed tonight in the OMDAC (from Cloned Analog Gear) that there  
> is a an analog input going into a ADC
>
> http://rubidium.dyndns.org/cag/pdf/omdac.pdf
>
> i might try this solution out. it uses two opamps with diodes in  
> their feedback loops both powered off of 5volts.
>
> really enjoying this thread
>
> thanks
>
>
>
>
>
> --------------------------------------------
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> ----------------------------------------
>> From: gsn10 at hotmail.com
>> To: synth-diy at dropmix.xs4all.nl
>> Subject: RE: [sdiy] converting a 10v p to p to a 0-5 volt signal
>> Date: Wed, 20 May 2009 19:56:46 -0400
>>
>>
>> Yeah, you'll never reach 5V, but won't you also never use all of  
>> the ADC's resolution. If 0v is 00000000 and 5v is 11111111 (I'm  
>> assuming it's unsigned, obviously), then 1.5v will be 01001101 and  
>> 3.5 v will be 10110010 (or something like that), which limits the  
>> range to about 102 steps rather than the full 256. This is less  
>> than 7 bits of resolution. And if the original goal was to have  
>> the LSB correspond to one quarter tone, it now only works over a  
>> little more than 4 octaves.
>>
>> Am I missing something?
>>
>> ----------------------------------------
>>> Date: Wed, 20 May 2009 16:41:02 -0700
>>> From: dixon at interchange.ubc.ca
>>> Subject: RE: [sdiy] converting a 10v p to p to a 0-5 volt signal
>>> To: gsn10 at hotmail.com; synth-diy at dropmix.xs4all.nl
>>>
>>>> You can't limit the instantaneous amplitude of a real-time input  
>>>> without
>>>> risking some form of distortion. You could use some sort of  
>>>> companding
>>>> circuit, but it's still going to clip on extreme transients,  
>>>> plus it will
>>>> mess up your scaling for CVs.
>>>
>>>
>>>>> this is why maybe David's method of going 1vptop is a good idea.
>>>>>
>>>>> however i think i would need some heavier boosting on the way out
>>>> because when i have tried such a small to PtoP i have gotten  
>>>> nill on the
>>>> output.
>>>
>>>
>>> Just for clarity, because I sent it personally to Dan and not to  
>>> the list,
>>> my idea was to reduce the signal to about 1V peak to peak and use  
>>> that as
>>> the input to the ADC. I don't think it matters to the ADC what  
>>> the input
>>> voltage range is; the accuracy is still just a function of bit  
>>> resolution,
>>> is it not? Plus, if the incoming signal is only limited to about  
>>> the range
>>> of safety of the ADC, then that precludes adding signals  
>>> together. However,
>>> if the division is more severe (like 1/10 or 1/20) then several  
>>> signals
>>> could be added together and it would still never reach the 5V limit.
>>>
>>
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