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diyMod and Corner Frequency - Page 2

post #16 of 20
Thread Starter 
DiyMod is the name used in the original thread for the diy version of the iMod, so I just went with that To clarify: I'm planning to diymod my iPod, and trying to choose the caps to go with it. At first I plan to use it with a mini3, so need to plan for a 10K pot.

Qusp, I didn't know about phase distortion, thank you. Is the level at which it stops being significant given by just 10*f?

As for the pot, I understand that aiming for a 10% max change in resistance should more than cover me? I wish I could take an ohmmeter to one and see for myself, but I don't happen to have any pots lying around just now.

The question about the amp's output caps is mainly theoretical, I'm not planning to build any such amp. Although doesn't the CMoy have output caps?
So talking about iMod caps and, for argument's sake, a CMoy, it will then become a second-order filter? If the effect is simply additive, it seems the corner frequency should change, and possibly audibly affect performance, but how to calculate this?

Methinks an electronics text is in order for the winter holidays
post #17 of 20
like tomb says, you calculate the output caps in circuit as if it were a separate problem. well at least thats what I do, I have never had to take this into account when making docks before. this should already be taken care of by the amp design.

and yes 10 x f (or actually just below) is the point any meaningful phase distortions occur in the band. all the math is in the equation I posted above. this is pasted from a calc I use for calculating exactly this problem in excel. so was kinda surprised when you seemingly passed right over it
post #18 of 20
The corner frequency has to be calculated separately, but I still think two filters must have an additive effect. Two first order filters should have the effect of a second order filter. Not? If eg the corner frequency is 20 Hz for both input and output filter with 6 dB/oct attenuation, shouldn't they together attenuate the signal 12 dB/oct? My intuitions says so and so does simulation.
post #19 of 20
Thread Starter 
Quote:
Originally Posted by qusp View Post
so was kinda surprised when you seemingly passed right over it
I was typing my response while you posted yours, so I didn't see it until later, sorry about that, and thanks for your help!

I see your point, diditmyself. As far as I know, filters do add, unless there's circuitry between them to prevent that. I guess what I don't understand is how an amp's design can compensate for frequency attenuation caused by a separate device.
post #20 of 20
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