Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: knotscott on November 08, 2010, 07:18:58 am

Title: Choke Value for an 18 Watt Stout
Post by: knotscott on November 08, 2010, 07:18:58 am

How critical is the exact value of the 4H choke in the 18 Watt Stout power supply?  I've got an 3H choke that's available and free, so I'd hate to spend more money if the one I've got will work well enough.

TIA.

Title: Re: Choke Value for an 18 Watt Stout
Post by: FYL on November 08, 2010, 08:02:19 am

There's an empirical formula for a CLC supply (C1 + C2) * L > 200, with C in µF and L in H.

The stout use 40 and 20µF for C1 and C2, sum and product is 180 with a 3 H choke, below the recommended 200 but good enough as it's only a 10 % diff and because the formula applies to a global supply (plates + screens + small signal) - you only feed screens + small signal in a Stout.

 

Title: Re: Choke Value for an 18 Watt Stout
Post by: Fresh_Start on November 08, 2010, 08:41:06 am

Just make sure that the current rating of your choke is adequate for two EL-84 screen grids and your preamp.

Cheers,

Chip

Title: Re: Choke Value for an 18 Watt Stout
Post by: knotscott on November 08, 2010, 09:17:40 am

Thanks to both of you for the replies.  The choke actually came out of an amp chassis that had two EL84 output tubes, so I'm assuming its fine.  What will I ever do with the $20 I saved?  :wink: