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Calling all M^3 owners with Bass Boost!

post #1 of 22
7/16/10 at 1:25am
Thread Starter 

 

What do you have R3, R4, Rbb, and Cbb set to? For me, at a gain of 5 I have R3 and R4 set to 2.55KΩ and 10.2KΩ respectively. Rbb is 50KΩ for the Alps RK27. And Cbb is ??

My current headphones is in my sig. I'm just curious that's all. I'm going to tinker with an EQ for a bit, but I want to hear yours.

 

Here's an interesting chart http://www.independentrecording.net/irn/resources/freqchart/main_display.htm


Edited by HeadFi Fanatic - 7/16/10 at 1:49am
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post #2 of 22
7/16/10 at 11:17am

Well, as you use a 50K pot for bass boost, it's adjustable so R3 and R4 values aren't a big deal, just set Cbb to how much of a curve you want.  I generally stick to 0.22uF but as I think the K701 sound thin, perhaps 0.1 - 0.15 would give some more boost.

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post #3 of 22
7/16/10 at 12:44pm
Thread Starter 

 

I can't decide between .1uF and .068uF. I might as well order both and experiment!

Edit: I wonder if it's possible to build a switch that can toggle between .1uF and .068uF for the left and right Cbb


Edited by HeadFi Fanatic - 7/16/10 at 5:15pm
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post #4 of 22
7/16/10 at 7:47pm
Quote:
Originally Posted by HeadFi Fanatic View Post

Edit: I wonder if it's possible to build a switch that can toggle between .1uF and .068uF for the left and right Cbb


It's DIY, everything is possible, :P

 

If I were going got do that, I'd get 2 dpdt switches or one 4pdt switch and wire the center poles to the board and put the capacitors on each side.

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post #5 of 22
7/16/10 at 8:35pm

Why not just use sockets until you've settled on the right mix

 

cheers

FRED

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post #6 of 22
7/17/10 at 7:46pm
Thread Starter 
Quote:
Originally Posted by t0wer View Post




It's DIY, everything is possible, :P

 

If I were going got do that, I'd get 2 dpdt switches or one 4pdt switch and wire the center poles to the board and put the capacitors on each side.


So say I have 0.22, 0.15, 0.1, and 0.068 for both CbbR and CbbL. I want to use a single knob to select different values for CbbR and CbbL instead of two knobs for each Cbb. Can you illustrate it as a diagram? I understand things better visually.

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post #7 of 22
7/17/10 at 7:51pm

I suggest not to switch multiple caps.  It's undesirable to add complicated wiring in the negative feedback loop of the amp.  The bass boost is already variable (pot adjusted), so just choose a good Cbb value, along with R4 and R3, and be done with it.  Use the "Bass boost calculator" at the M³ website to see what the max boost curve would look like.

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post #8 of 22
7/17/10 at 8:58pm
Thread Starter 

 

Really? aw... Just when I was going to label it as "sub-bass," "lower bass," "upper bass," and "bass-head" on a 4-way knob switch (.22uF, .15uF, .1uF, and .068uF respectively) depending on the music. I came to that conclusion using the BB calculator. I'll still order all four for experimentation, but I don't like the idea of putting the other 3 caps to waste.

 

Besides the "complicated wiring," what problems will there be should it be attempted? Will the sound quality degrade?

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post #9 of 22
7/17/10 at 9:02pm

The extra wires to the switch (and offboard parts) could cause the amp to become unstable and/or pick up noise and interference.
 

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post #10 of 22
7/17/10 at 9:56pm
Thread Starter 
Quote:
Originally Posted by amb View Post

The extra wires to the switch (and offboard parts) could cause the amp to become unstable and/or pick up noise and interference.
 

okay. Well I guess I'll have to compromise then. I'm going to remove .22 and .15 off the list since it doesn't help K701's bass punch much. Back to square one, .1 or .068. I used an FFT filter to simulate the frequency graph results I got from the BB calculator. I wish I can swap them easily without hassle...


 

Quote:
Originally Posted by Fred_fred2004 View Post

Why not just use sockets until you've settled on the right mix

 

cheers

FRED



What sockets? There's sockets for caps?


Edited by HeadFi Fanatic - 7/18/10 at 1:17am
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post #11 of 22
7/18/10 at 1:06am

I use these all the time

 

when mucking about with ideas

 

CIMG8551 (Small).JPG

 

off ebay

 

cheers

FRED

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post #12 of 22
7/18/10 at 1:01pm
Thread Starter 

I don't see any caps in your pic. How will those sockets secure caps in its place?

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post #13 of 22
7/18/10 at 1:10pm
Quote:
Originally Posted by HeadFi Fanatic View Post

I don't see any caps in your pic. How will those sockets secure caps in its place?


By friction only.  Of course, it assumes that the cap leads are the correct diameter to work.  You could use these sockets (they're called "break-apart SIP sockets" and available from the usual vendors) to experiment with different caps, but I recommend soldering in the caps afterwards.  You don't want those caps to fall out accidentally.

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post #14 of 22
7/21/10 at 2:27pm
Thread Starter 

 

just wondering, would the amp go haywire if I omit the Cbb pads?

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post #15 of 22
7/21/10 at 3:00pm

You planning on cutting them off the PCB?

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