Hot Rodding with Film Caps

A popular Bottlehead Crack mod is changing the electrolytic output capacitors with huge film capacitors. The Crack is born with a pretty decent pair of output caps, so why do change them at all? Because it looks darn cool! Nuff said, let get going.

Bottlehead Crack overview:


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Bottlehead Crack + Speedball

The two 100uF caps is located just above the octal socket, beneath the Speedball upgrade. They look pretty small and compared to the film caps, they are tiny. Time to get them out and these babies in there.


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Mundorf Film 100uf 400v capacitor

I have choosen a pair of Mundorf M Cap Audiophiler 100uF 400 volt MKP film caps.  I made a pair of acrylic standoffs I am going to mount on the chassis with epoxy glue. Both the aluminium surface and the acrylics are sanded and rinsed with alcohol before applying the epoxy glue.


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Film cap standoffs installed

The standoffs/brackets fits just fine, but it’s going to be a very tight fit with the caps are installed. I wonder if I should have choosen the 250 volt version which is a tad smaller.

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They are absolutely huge. The Crack looks so much more potent with these in it.

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Film capacitors in a Bottlehead Crack + Speedball



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1 uF MCap Supreme bypass caps.

Oh. I forgot I bought a pair of 1 uF Mundorf MCap Supreme for bypassing the 100 uF MCaps. The Supremes is well known for their highly detailed sound. Why not just over do it then. I had a listening test in between installing the 100 uF film caps and them after bypassing, and I’m almost certain I could hear a difference. Seemed to have a more detailed treble and more 3d-ish soundstage. Well I could be imagining the difference.


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Bypassing the film caps

Just the bypass shown from the other side.


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Close-up of the bypass caps.

Bottlehead Crack

It is definitely a tight fit. I had to squeeze in all down to fit in the cabinet.  But wait, there is something missing.


WIMA 2.2 uF MKS4 film capacitor

Let’s just bypass the last electrolytic capacitor in the PSU too. This WIMA 2.2 uF MKS4 film cap should make it faster. Or at least theoretically it should… I have extended the legs with some solid core wire.


 Then it’s just fitted on each legs of the 220uF capacitor and soldered. Looks nice

Maybe I am fooling myself into believing there is a audible difference with these film caps. I definitely think there is more detail and a wider more 3d like sound stage. But it’s not the big difference of the Speedball upgrade, if any, it’s a subtle difference in comparison.