[aluren]

As an experiment to put my vcap dock to good use, I'm connecting my pico via its usb dac from my laptop, then connecting a mini cable from the pico phone out to my vcap dock. Then I plugged in my UE-10 through the vcap's output. What I noticed is that there is no bass. The music is extremely crisp and detailed with plenty of soundstage. This leads me to wonder why such connection would eliminate the bass altogether. Is the signal path somehow distorted through this weird connection method? I was still able to adjust the volume with the pico or the laptop. Thanks for your help!

 

[justin w.]

Why would you want to do this? If I understand correctly, you're just putting capacitors in series with the output of the Pico -- which are probably 1/100th the size you'd need to prevent bass roll-off with UE10.

 

[aluren]

hmm... i don't know what that means, but yeah, i was just experimenting... there's nothing wrong with my pico...

 

[TheMarchingMule]

This thread has confused me.

 

[jade0203]

I just got my V-Cap.
And I hoop it up like this:
MP3 LO -> V-CAP -> AMP -> My cans
I am really dont know will it help or improve the SQ.
But I try to do a little A/B test, I found out it is a bit batter, sound more clear.

I am also wondering will it any differences when the V-CAP in after source position and after AMP position.

Lee

 

[FallenAngel]

Uhm... you don't put output caps on the Pico, there is no reason to. You do need output caps on an iMod/diyMod, they go between it and the amp. You do NOT put output caps where they are not needed like other MP3 players (or unmodified iPods).

 

[warrior05]

Hey, Ken-

Odd experiment and one that didn't yield very good results, ay?

I cannot explain why your bass got so affected. Resistance can affect it but I didn't think caps would. I'm assuming you are using one of the ICs I built you? Did you try both sets?

BTW - as a general piece of info - it is okay to use caps in the signal path regardless if you have an iMod or not. It won't hurt anything. It is the other way around that can cause damage (signal path from iMod without caps).

 

[justin w.]

Quote:

Originally Posted by warrior05 /img/forum/go_quote.gif Hey, Ken- Odd experiment and one that didn't yield very good results, ay? I cannot explain why your bass got so affected. Resistance can affect it but I didn't think caps would. I'm assuming you are using one of the ICs I built you? Did you try both sets? BTW - as a general piece of info - it is okay to use caps in the signal path regardless if you have an iMod or not. It won't hurt anything. It is the other way around that can cause damage (signal path from iMod without caps).

The capacitors in the Vcap dock are not large enough for connecting a headphone directly, only for connecting to another amplifier or something with a much higher impedance

 

[warrior05]

Quote:

Originally Posted by justin w. /img/forum/go_quote.gif The capacitors in the Vcap dock are not large enough for connecting a headphone directly, only for connecting to another amplifier or something with a much higher impedance

Good point. Thanks, Justin!

 

[n_maher]

Quote:

Originally Posted by warrior05 /img/forum/go_quote.gif Good point. Thanks, Justin!

If I understand things correctly the addition of the Vcap dock on the output of the pico will form a high-pass filter with the headphones used. Assuming that the Vcap dock uses the same 2.2uF value that the Auricap dock does and that the OP was using UE10s (13.3ohm impedance according to UE) the -3db cutoff frequency would be around 5000Hz.

So in addition to no bass there'd be a whole lot more missing or at least seriously attenuated.

 

[Pars]

To add to what Nate said, the formula for the cutoff (-3dB) frequency is:

1/2 * Pi * R * C

where R is the resistance to ground (in this case, the impedance of the headphones), and C is the capacitance in the VCap dock, in farads

So, in Nate's example, you have 1/2 * 3.14159 * 13.3 * 0.0000022 = 5,439 Hz.

Result: no bass; midrange seriously mucked with

The VCap dock, when used as intended, would be going into an amp, which probably has an input impedance of at least 10K ohms, and probably higher. As you can see when you replace the 13.3 with 10,000 or higher, the cutoff frequency goes way down (under 10Hz).

Result: no messing with the midrange, bass response below 20Hz if present.

 

[Kabeer]

Ken's V-caps are 6.8microF I think. Still wouldnt make thaat much a difference in your calculation.

 

[n_maher]

Quote:

Originally Posted by Kabeer /img/forum/go_quote.gif Ken's V-caps are 6.8microF I think. Still wouldn't make that much a difference in your calculation.

It's a direct correlation between cap size and cutoff frequency. Substituting that value cap yields a cutoff frequency of ~1800Hz, still basically destroying the audio signal. So the fact remains that adding a coupling capacitor is completely useless in this case and is clearly doing way more harm than possible good.

 

[Pars]

And backing up further... the ONLY reason to put a coupling cap in is to block DC offset, which is their function following an iMod (which has had its coupling caps removed.)

There is absolutely NO reason to use this between the amp and the phones. I don't care how expensive VCAPs are... the best cap is no cap.

That said, sure, its OK to play around and see what happens if... just don't post using titles that could be misconstrued as being an equipment problem for something that is clearly playing around, or "pilot error"

 

[aluren]

after reading everyone's explanations, it makes sense now. i'm no engineer, so i had to ask. i also know that this is NOT the proper way to be using a vcap dock, and when connecting to another amp, the bass roll off is gone and everything is normal again. thanks everyone!