rocket powertubes cath. bypass cap rating

General discussion area for tube amps.

Moderators: pompeiisneaks, Colossal

Post Reply
arjepsen
Posts: 208
Joined: Tue May 20, 2008 10:30 am

rocket powertubes cath. bypass cap rating

Post by arjepsen »

Hey.
A bit of a sanity check:
Usually I tend to go a bit overboard with the voltage rating on caps, but unfortunately my layout of a rocket give me a bit of space constraint on the bypass cap for the 4xel84 cathodes.
In the schematic it's listed as a 220µF/100V.
The voltage chart only shows a bit under 10 volts on the cathodes....
So I presume a 63V cap would be safe enough?

/Anders
User avatar
Malcolm Irving
Posts: 139
Joined: Wed Jan 14, 2015 12:06 am
Location: Derbyshire, UK

Re: rocket powertubes cath. bypass cap rating

Post by Malcolm Irving »

Yes, a 63V cap will be fine. The voltage there can rise a bit if the output stage is overdriven, but only up to 15V or thereabouts.
Stevem
Posts: 4551
Joined: Fri Jan 24, 2014 3:01 pm
Location: 1/3rd the way out one of the arms of the Milkyway.

Re: rocket powertubes cath. bypass cap rating

Post by Stevem »

You should really decide on the that caps uf value by auditioning the amp at the most used volume levels you play at!

In Hi Fi amp use for example even 250 uf just starts to get it done when you need to go down to 20hz, which of course we do not with 6 string gtr , but you for example may find a 100 uf fills your average playing needs better.

You might even find that having 2 different value caps on a switch better fills your needs for low volume and normal volume playing.
In general using caps with a voltage rating of some 20 to 50 volts more than needed will extend there life greatly!

Another important concideration with caps in tube amp use is there temp rating if you do not want the caps to drift in value and have your tone shift as a result .

Caps rated for 85c used near the output stage and its greater heat level is the way to go!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Post Reply