Maybe a Noob question...Resistor values sunking

[small fish]

Hi,
I just wondered where I get the 422k and 392k resistors for the sunking 

A 390k is no prob, a 420k neither. Does it make any difference?
I measured some of my 390k and got values from 387k to 390k, of course there´s some differences due to the 1% rate / tolerance. I would also put some values in series to match the 392k. Does it make sense?

Any advice will be taken...tia

carsten

[Haberdasher]

An example of how to nail it would be- the 420K in series with a 2k2, and double check with your dmm.  solder them together where they meet and stand them up like a tepee on your pcb, with the unsoldered leg from each resistor going through either hole.  Make sense?

[small fish]

Actually that was clear.
I tried different values to match the right value.
the question is: is it necessary? or will a 390k resistor do the same (audible) job as a 392k?
Of course, there´s 2k difference.... but is it worth it?

Somehow it make sense to solder the legs to the holes..... 
so, it wasn´t the question, how to wire / solder them in series - but thx for the fast "educational unit" 

[madbean]

It's only necessary if you think it is. If you have a 390k and 420k that measure close to the dot, then you are already within 1% tolerance of the actual value indicated.

[jkokura]

You could in theory get a 392k resistor an have it measure 390k. Tolerance is what we are talking about here. I would get a bunch of 390k resistors and then measure them until you found one at 392k. Shouldn't be hard.

Jacob

[small fish]

Aehmm, ok,....so why is this value chosen? 

I once built a TS clone with carbon comp resistors (the fat, old ones) and used the dmm to measure every single resistor to the value which was given in the schematic. So, maybe there´s a lot of mojo in it, but it sounded quite audible different to my TS 10 / TS-5 (which were actually modded to the TS-9 specs).

Why do you use these values? Is it math? Sorry for these questions, but I´d like to understand...

thx for your answers, anyway 

[madbean]

You'd have to ask Bill F. why those values were chosen. Or, the engineer that helped devise the filtering portion of the Klon. Most likely he was try to hit a specific frequency range and that's just how the values worked out.


Here's some science

Here's one of the most important formulas you can ever know in stompbox design:

f = 1/[2*pi*R*C], where f = frequency in Hertz, R = resistance in M-Ohms and C = capacitance in micro Farads.

f is the corner frequency at which the peak of the curve starts to drop (-6db/Octave for 1st Order). The formula is the same for both low pass and high pass filters.

You can use this to understand how a filter is behaving at a certain point in a circuit. For example, in the Tube Screamer, you have an active tone control on the second part of the op-amp. Just before that, there is a 1k resistor in series with the signal path and a 220n (.22uF) cap to ground. This creates a low pass filter. Following the math,

f = 1/[2*pi*R*C] = 1/[6.28*.001*.22] = 723 Hz

So, that filter starts attenuating the high end at 723 Hz at that point in the circuit. After that, the tone control can be used to add that rolled off frequency right back in!

Point being, you can break some of these filters down from the Klon or anywhere else to get a better understanding of what's happening at a particular point. I actually have this formula in a spreadsheet so I can type in various values for resistors and caps and see what the result is instantly.

More reading:
http://www.geofex.com/Article_Folders/TStech/tsxtech.htm
http://en.wikipedia.org/wiki/Low-pass_filter

[CaptainVictory]

There's this too:  www.muzique.com/schem/filter.htm

[small fish]

so, this will be when the Duncan Tone Stack Calculator hits the scene?

think it´s time so spend some weekends to give it a try...
...sweetheart...anything to do on sundays???       

[rhcp311]

You'd have to ask Bill F. why those values were chosen. Or, the engineer that helped devise the filtering portion of the Klon. Most likely he was try to hit a specific frequency range and that's just how the values worked out.


Here's some science

Here's one of the most important formulas you can ever know in stompbox design:

f = 1/[2*pi*R*C], where f = frequency in Hertz, R = resistance in M-Ohms and C = capacitance in micro Farads.

f is the corner frequency at which the peak of the curve starts to drop (-6db/Octave for 1st Order). The formula is the same for both low pass and high pass filters.

You can use this to understand how a filter is behaving at a certain point in a circuit. For example, in the Tube Screamer, you have an active tone control on the second part of the op-amp. Just before that, there is a 1k resistor in series with the signal path and a 220n (.22uF) cap to ground. This creates a low pass filter. Following the math,

f = 1/[2*pi*R*C] = 1/[6.28*.001*.22] = 723 Hz

So, that filter starts attenuating the high end at 723 Hz at that point in the circuit. After that, the tone control can be used to add that rolled off frequency right back in!

Point being, you can break some of these filters down from the Klon or anywhere else to get a better understanding of what's happening at a particular point. I actually have this formula in a spreadsheet so I can type in various values for resistors and caps and see what the result is instantly.

More reading:
http://www.geofex.com/Article_Folders/TStech/tsxtech.htm
http://en.wikipedia.org/wiki/Low-pass_filter

That was insanely helpful. Thanks a lot. It's always nice to get a bit more knowledge about WHY exactly I'm doing something instead of what I'm supposed to be doing.