[sdiy] Tempco 5.1 k 3000 PPM/K (Was: low-k ceramic capacitor?)

[Seb Francis]

Hi  Drew,

Regarding the 5.1K tempcos ... the 3000ppm/k is not critical (in fact 
3300ppm/k is the 'ideal' value).  This is not a VCO, so you're really 
not going to notice a huge difference if you just use a normal 5.1K 
resistor.  Here's what I wrote previously on this ...

"You could probably get away with not using them.  The gain-control 
input of the VCA varies +0.33%/C, and equally the gain-control output of 
the RMS level detector varies the same amount.

So it sort of cancels out, except the make up gain & threshold control 
settings then will vary by 0.33%/C.  This means that on a hot day your 
compressor could have slightly different settings as on a cold day.  
Also as it warms up the settings will change.

e.g. For a 10deg temperature change that's a 3.3% change in gain & 
threshold voltage.  What this means in terms of dB depends on the actual 
settings since for unity gain the control voltage is 0mV and thus is 
unaffected by the temperature.  If you do the maths it works out as for 
every 10dB away from unity gain there is a 1/3dB error per 10deg.  For 
example, a make up gain setting of +10dB would change 1/3dB for 10deg 
change in temperature, and a threshold setting of -20dB would change 
2/3dB for 10deg change in temperature.

So as you can see the error from using normal resistors is not very 
significant unless the temperature in your studio varies a lot."

Seb



drew meyer wrote:
> yes i realized that the creator of the pcb/kit i'm using linked to 
> it.  now if only i can get some shipping costs to the u.s. out of 
> them.  their site expects you to order without knowing what you'll 
> pay.  i put in an inquiry.
>
> thanks for all the help people.
>
> drew
>
> Jeff Farr wrote:
>> Farnell in the UK is the only place I know of that carries the 5.1k 
>> tempco's
>>
>> On 2/8/07, Andre Majorel <aym-htnys at teaser.fr> wrote:
>>> On 2007-02-08 16:26 -0600, drew meyer wrote:
>>>
>>> > one more thing,  what should i look for if i want a 3300ppm/c
>>> > resistor at 5k1?  i searched 3300 ppm at mouser and i didn't
>>> > come up with anything.
>>>
>>> All the links I've gathered on the subject :
>>>
>>>   http://www.teaser.fr/~amajorel/sourcing/
>>>
>>> IIRC, Digi-Key have other values. They may have the 5.1 k you're
>>> looking for.
>>>
>>> -- 
>>> André Majorel <URL:http://www.teaser.fr/~amajorel/>
>>> Do not use this account for regular correspondence.
>>> See the URL above for contact information.
>>>
>>
>
>