Author Topic: Total Recall Resistor value  (Read 629 times)

PhiloB

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Total Recall Resistor value
« on: July 07, 2017, 09:41:45 PM »
I'm preparing to build the Total Recall.  The BOM calls for a 24k3 and 33k2.  I thought I had ordered carbon film resistors (5%) of the values 24k and 33k and planned on finding values close.  Apparently I didn't do a good job of ordering.  Looking at the schematic though, R23 and R24 don't look too critical if I use a 24k and 33k (1% Metal Film) Resistor.  Looks like they are responsible for setting gain and rc filter for IC3.  I only ask because those values are so specific.  Want to make sure I'm not missing something!
Thanks,
Phillip


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bsoncini

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Re: Total Recall Resistor value
« Reply #1 on: July 08, 2017, 12:14:35 AM »
Out of a batch of 20 1% resistors each I found the right value. Just use your multimeter to find the right ones

PhiloB

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Re: Total Recall Resistor value
« Reply #2 on: July 08, 2017, 07:00:11 PM »
Out of a batch of 20 1% resistors each I found the right value. Just use your multimeter to find the right ones
You had better luck than I did.  All my 24k resistors were right at 24.0x.  My 33k resistors were at 32.8-33.1.
I plugged the values in the non inverting op amp gain calculator and it doesn't seem to be a huge deal.  Was hoping someone would confirm my suspicions or rebuke me before I started soldering;)


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bsoncini

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Scruffie

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Re: Total Recall Resistor value
« Reply #4 on: July 09, 2017, 05:26:21 AM »
I think i've posted this before but my theory which i'm fairly sure is right is in vintage EHX pedals, when an oddly specific value such as that is used it was to be sure that a tighter tolerance resistor was used because the gain or whatever function was important enough that a badly off 5 or 10% resistor wouldn't cut it.
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PhiloB

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Re: Total Recall Resistor value
« Reply #5 on: July 09, 2017, 05:53:06 AM »
http://www.madbeanpedals.com/forum/index.php?topic=24627.0
I swear I did a search before I asked!  I'm going to blame it on the Tapatalk app rather than user error;)

Scruffier that seems like a logical theory. 


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