Output Capacitor Upgrading Questions

[Love Rhino]

This was a great thread and I learned a lot about upgrading the crack!  I was wondering if I were using Sennheiser hd800 headphones, or similar 300+ resistance headphones, what would be the lowest uf I could get away with replacing the output caps?  I would of course like to avoid noticeable roll of in audible sound.  I was looking at a chart that made it seem that 33uf would be ok, and that would open up my options in cap choices quite a bit.  Stick with higher uf around the 100 mark, or....? 

Thank you!

 

[Paul Birkeland]

I would of course like to avoid noticeable roll of in audible sound.

If we assume the HD-800 is a 300 ohm headphone, then I'd stick with 100uF, but the HD-800 is not a resistive device. The HD-800 is ~450 ohms at 20Hz, which would lead me to recommend ~70uF.

If you don't care about 20Hz response but 30Hz is OK, then you could go down around 60uF. 

IMO, 33uF is too small.  You can certainly buy a selection of Dayton film caps in 33uF, 47uF, 68uF, and 100uF values, then do some listening tests.

 

[mcandmar]

These 82uf popped up on eBay recently, might be of interest.  Seller has a whole range of oddball cap sizes which might suit some for speaker crossovers.

https://www.ebay.co.uk/itm/333019020505

https://www.ebay.co.uk/itm/332828562969

 

[Love Rhino]

Thanks!  I like the look of the clarity caps.  I actually am going to try some Russian KZK 100uf white line caps.  I might have to get creative to get them to fit, but luckily I live next door to a woodworker so I can recruit him if I need more space.  They're not as large as many of the Mundorfs, however.

 

[Love Rhino]

Does anyone have a recommendation of some 470uf caps to replace the first couple PS caps?  I've been seeing quite a few 'nichicon' but not a lot else, and i'm looking for something not too expensive that would still be an upgrade.

I was thinking of  changing out the first two 220uf PS caps with 470 caps, and then using a film cap for the last PS (I have a choke installed so I could get away with lower uf). 

 

[Paul Birkeland]

This is a higher capacitance version of what we put in the kits:
https://www.mouser.com/ProductDetail/Nichicon/UCY2E331MHD9?qs=Ajmft%252BTTukE5XdvmYQQqPw%3D%3D

We use about the nicest Nichicon caps we can.

 

[Love Rhino]

Thanks Paul!

Would there be any benefit/loss of going with these instead?  They look to be the same type but at 470uf: https://www.mouser.com/ProductDetail/Nichicon/UPW2E471MRD?qs=sGAEpiMZZMukHu%252BjC5l7YVWxZN7wNrp482P3JGA0oTI%3D

 

[Paul Birkeland]

They don't carry a lifetime rating that is as long as what we provide, so technically I would consider them a downgrade.  They will still live a long life in a Crack though.

 

[Love Rhino]

So a couple months later the kzk 100uf 250v caps have arrived!  (Thanks, russia post, for your incredibly slow shipping!)

I was wondering if there was ever a consensus on the orientation of them?  For example, the input connected to which terminal, or if it really just doesnt matter which way they're facing?

 

[Deke609]

I think the general rule of thumb is connect the cap's "outer foil" to the lowest impedance node. So, for example, since these are output caps and the Crack has (IIRC) an output impedance of approx. 120 ohms and is intended for headphones with 200+ ohms impedance, the headphone jack is the highest impedance node and would connect to the "inner foil", and the "outer foil" would connect to the cathode of the 6080.

But all of this assumes that the cap is marked (correctly) -- e.g., with a line indicating outer foil. 

Apparently, you can attempt to determine which side is the outer foil using a scope. I've never tried this, but it is described here: http://www.aikenamps.com/index.php/where-to-connect-the-outside-foil-on-capacitors

cheers, Derek

 

[cddc]

Good discussion on caps