Bass Boost Circuit
Jul 5, 2008 at 7:43 AM Thread Starter Post #1 of 10

arande2

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I am going to build a CMoy (first amp) soon and once I get it working, I am going to lower the gain and increase the bass at lower frequencies.

The bass boost circuit is going to be a simple RC circuit in the feedback loop. I have used an equalizer on my computer with the headphones I'll be using with this amp (AKG K81DJ) to simulate different bass boost properties and have chosen values for the +3 dB freq to be 54hz (close to it) and the shelving freq to be 8hz with 17dB boost. This will multiply DC offset voltage by 6.8, so I'll have to make sure DC offset is low before I do this.

My question is this: Does it matter if I put the RC Circuit before or after R4? I don't think it does, but I want to make sure before I go altering the circuit.

http://www.tangentsoft.net/audio/cmo...angent-sch.pdf

I also appreciate suggestions and if you have any questions that would help you answer I am ready to answer.
smily_headphones1.gif


Thanks!
 
Jul 9, 2008 at 7:43 PM Post #6 of 10

ruZZ.il

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Take a look at the PPA and M^3's schematics, then concoct something alike, tweak, play, break, play, etc..

I hope you're just doing this for the sake of the experiment, since if you plan on putting effort into things to be used a lot, maybe you should use a more advanced platform? PIMETA?..
 
Jul 16, 2008 at 2:51 AM Post #8 of 10

Random Murderer

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Quote:

Originally Posted by diredesire /img/forum/go_quote.gif
http://www.head-fi.org/forums/f6/bas...73/index2.html


his bass boost didn't work because he implemented wrong, he tried to replace the feedback loop with the bass boost, when it should be in series with r4.
 
Jul 16, 2008 at 5:50 AM Post #9 of 10

diredesire

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Quote:

Originally Posted by Random Murderer /img/forum/go_quote.gif
his bass boost didn't work because he implemented wrong, he tried to replace the feedback loop with the bass boost, when it should be in series with r4.



Yeah, I know. The link i posted discusses this (in passing, though). I probably should have left a note with that, but I was in a hurry
wink.gif
 
Jul 16, 2008 at 3:22 PM Post #10 of 10

arande2

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Hi guys.

I am not doing something more advanced due to monetary reasons.

My question was answered and I ended up changing my values after understanding the boost properties more. The gain without boost will be 4 (3.32k value R3), the corner frequency will be 136.4hz (.1uf), and the shelf/boost will be 20hz/17dB (80.6K bass gain resistor).
 

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