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How can I disable FiiO E3's bass boost by taking it apart?

post #1 of 8
12/12/10 at 11:03pm
Thread Starter 

Sombody named Magman wrote the schematics for FiiO E3 amp back in June 2009, but the all pdf files are not working any more unfortunitely.

 

I'm interested to know which elements to short in order to disable the FiiO E3's bass boost. I didn't think there might be a way until I saw this page, it says "To disable bass boost, short the CB_L and CB_R terminals" for the cMoyBB amp.

 

I haven't opened up my E3 yet, and won't until I know there is a way to achieve this. I hope someone here can point me to the right direction or give me a solution, if you have seen the inner workings/circuit of the E3 and know enough about which part contributes to the bass boosting function.

 

Thanks.


Edited by kingpage - 12/12/10 at 11:07pm
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post #2 of 8
12/13/10 at 2:52am
Thread Starter 

I have just found these two photos somewhere else on this forum, both the front and the back. Any electrical engineer? or someone who understands amp circuitry? Could you have a look at these and tell me whether you can see anything there that resembles a bass boost element? If needed, I could disassemble it and take detailed pictures of the circuit board for you to analyse.

 

I am willing to sacrifice my E3, given you know what you are talking about. I hate the bass boost anyway and rarely use it as a result; my CAL (Creative Aurvana Live) has enough bass quantity already, so a little experiment to get a flat frequency response out of E3 would be nice. It's really only experimenting with a $5 toy.

 

Cheers. (I know you may think it is child's play, please at least let me know whether this little project would be possible if you can)

 

 

fiio1.jpgfiio2.jpg


Edited by kingpage - 12/13/10 at 3:02am
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post #3 of 8
12/13/10 at 3:48am
Thread Starter 

People pointed out that LM4917 is likely to be used in E3. http://www.national.com/ds/LM/LM4917.pdf

From the pdf, it states that output coupling capacitors are eliminated to improves low frequency response, so I suppose the bass boost is due to a lack of something rather than an addition of something which would make it impossible to remove it (the extra bass). Am I correct?

 


Edited by kingpage - 12/13/10 at 4:10am
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post #4 of 8
12/14/10 at 1:09am
Thread Starter 

Anyone kind enough to give me a straight yes or no answer?

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post #5 of 8
12/14/10 at 1:21am
I can't confirm this, but I remember there isn't any coupling caps on E3, and the opamp is from a Chinese brand.
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post #6 of 8
12/14/10 at 7:31pm
Thread Starter 



So, would you say this is a lost cause?

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post #7 of 8
12/14/10 at 11:49pm

coupling caps are not usually responsible for bass boost, normally it is achieved by an RC (resistor, capacitor) filter placed inside the feedback loop of the opamp, whether its DC coupled or not does not mean anything, the filter will be part of that cluster of parts surrounding the chip, but being it looks like a 4 layer board, its a bit difficult to tell which ones from the pics. a schematic and i'd be able to tell you. 

 

one thing though, I was under the impression that the E3 was all about the bass boost, it does not provide much anything by way of amplification or added clarity, so without it what do you have?

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post #8 of 8
1/15/11 at 1:14pm

I just tested the E3's frequency response, and here is the result:

e3-2.PNG

The frequency sweeps from 20Hz to 30KHz on a log scale over two minutes, and the frequency response is the amplitude envelope of the waveform, on a linear scale. I could make it look like a real frequency response plot in Matlab or something, but that would be way too much work.  500Hz is somewhere around 40-50 seconds, and 20KHz is somewhere around 1:50.  Anything over 20KHz can be ignored- my test system doesn't have a flat response in that region.

 

Removing the bass boost might make the low end weak.  The frequency response of the op-amp is shown in the datasheet:

Screen shot 2011-01-15 at 4.07.07 PM.png

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