Little dot MK2 coupling caps

[Datun Walnut]

Hi All,
I fancy a dig around in my little dot MK2 headphone amp. I'm pretty new to this but think the obvious place to start a bit of modding may be the coupling caps.
According this schematic I found, it seems to be a 220ufd bypassed by a 0.68ufd - both electrolytics.
What type of caps would be suitable as a replacement do you think? Space is at a premium in there so massive Russian cans aren't an option.

Thanks in advance

 

[DF96]

You could try removing the 0.68uF bypass cap. It might make no difference, or it might improve things a little. As a general rule, cap bypassing is not needed in analogue audio.

You could try increasing the value of the 220uF, maybe to 470uF. Again it may make no difference, or it may improve things a little.

 

[Datun Walnut]

Thank for that. I wonder why the bypass is there then?

 

[DF96]

Possibly to impress audio journalists, who usually know more about audio trends than audio electronics.

 

[starkeyg]

Hello,

Another thing you could try is replacing the 220uf cap with a bipolar. That should reduce what little distortion there is. Going with a larger value and larger voltage rating should help a little as well. If the change is enough to hear is a real question.

 

[Red Brown]

Hello,

Another thing you could try is replacing the 220uf cap with a bipolar. That should reduce what little distortion there is. Going with a larger value and larger voltage rating should help a little as well. If the change is enough to hear is a real question.

Hi, I'm a little confused by the schematic. I thought the coupling caps are the .22uf between the tube stages? The large electrolytics are just before the output to the jack and are bypassed by the .68ufs. Can you help me understand this?

 

[Red Brown]

Hi, I'm a little confused by the schematic. I thought the coupling caps are the .22uf between the tube stages? The large electrolytics are just before the output to the jack and are bypassed by the .68ufs. Can you help me understand this?

 

[chrisng]

The large electrolytics are just before the output to the jack and are bypassed by the .68ufs.

Yes, you get it right.
BTW, it is an OTL headphone amp, those electrolytic caps are output coupling caps.

 

[Mark Tillotson]

My take on that circuit is that its capable of delivering a substantial shock to the user. The output cap and 10k bleeder have a time constant of over 2 seconds, so the switch-on spike could be nasty - headphone jacks aren't noted for their careful design w.r.t. high voltage.

 

[rayma]

This is a duplicate thread, and should be merged with
"Bypass Caps in Tube Headphone Amp"