2. tech-talk
  3. 151852-2248

Capacitors for HP filters in tube amps recommendations?

I’ll soon be installing a capacitor on each of the input jacks of two tube power amps, to create passive 1st-order high-pass filters. Cap values are 19.9uF (20uF will do) and 30.33uF (let’s say 30uF). I’ll need two of the former and four of the latter (balanced/XLR input jacks), and I don’t want to spend more on the caps than the amps cost me ;-) .

I’m all ears for nominees. I don’t need or want any flavoring, "just" neutral transparency. The amps are powering fairly transparent loudspeakers (ESL’s, and Magnetic-Planars with Ribbon tweeters), which will pretty well reveal the character of the caps. In spite of that fact, "most-bang-for-the-buck" nominees are of particular interest, not cost-no-object ones. Thanks y’all.

128x128bdp24
erik_squires
16,057 posts
 
BDP24 - You know, you can easily make yourself an interconnect cable with a cap in line, no reason to mod your existing pre. :)


But good for you for catching the size problem with those! :) I forgot to mention it.
bdp24's avatar
bdp24 OP
9,788 posts
 
Actually Erik, the caps are going into the two power amps rather than the output jacks of the pre, as each amp is used with a specific loudspeaker. But I take your point---the caps could be incorporated into the interconnect going to each amp. Not soldered onto the outside of each cable’s RCA or XLR plugs, of course, and they won’t fit inside them. Modjeski lays out his amps (RM-10 Mk.2 and RM-200 Mk.2) pretty sparsely, so there should be plenty of room inside for caps.
erik_squires
16,057 posts
 
I'd do it this way just for the sake of ease of changing things. It's far easier to swap out interconnects than to get into an amp/pre and solder a cap, regardless of the size of the cap. 

However, it's your money and effort, so do it however it feels right to you. :)

Best,
Erik
bdp24's avatar
bdp24 OP
9,788 posts
 
So Erik, how do you incorporate the caps into an interconnect? Now that I think about it, since each amp is fed via un-switchable cables (one amp is balanced/XLR, the other se/RCA)---my pre has multiple balanced and se output jacks, caps on the cables sounds like a good idea. I wouldn’t know how to put caps into a balanced connection (a cap on each leg) other than inside the amp.
imhififan's avatar
imhififan
2,181 posts
 
Just an idea:

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcT15rxshQZAWRLRnpGMMHNyBQYLj7uRM2cUGI-hid-oJ8yY...

More to discover