Tube amplifier dummy load - Page 1
Forum section: electronics / projects

author: Anks
author_rank: Frequent Contributor
timestamp: December 17, 2013, 02:09:05 pm
content: I'm wondering If I could wind some resistors my self to use as a dummy load. I understand that these will act like inductors but most of the resistors used as high wattage amp loads are generally wire wound so I assume there is no harm in doing so. Also the field could be cancelled out by making two winding out of phase.This is really just to get me out of a rut and im hoping that it will work as a make shift load until I can get some new resistors as I would really like to get on with a repair that is for a friend for Christmas.Any input is much appreciated.

author: Mr Smiley
author_rank: Frequent Contributor
timestamp: December 17, 2013, 03:36:05 pm
content: You can make a wire-wound resistor in such a way that it is not inductive

author: Anks
author_rank: Frequent Contributor
timestamp: December 17, 2013, 03:37:53 pm
content: Quote from: Mr Smiley on December 17, 2013, 03:36:05 pmyou mean ayrton-perry winding or just using the method I mentioned before.

author: Mr Smiley
author_rank: Frequent Contributor
timestamp: December 17, 2013, 03:50:22 pm
content: Yep, and i believe there are other winding methods also

author: Rerouter
author_rank: Super Contributor
timestamp: December 17, 2013, 07:47:37 pm
content: Or a bifiliar winding, which i prefer as its simpler to to multiple layers,

author: free_electron
author_rank: Super Contributor
timestamp: December 17, 2013, 08:05:14 pm
content: i hear anvils make good dummy, and other, loads for tube amplifiers.Added bonus : if the amplifer is unstable and you are fed up with it you can drop the anvil on said tubes to solve the problem

author: redwire
author_rank: Newbie
timestamp: December 17, 2013, 09:44:01 pm
content: I use 8 ohm 50W wire-wound resistor as a dummy load for my tube amps, with no problems. They have small inductance in the uH.You can also use a stove heating element, clothes iron etc. as they around 10 ohms at 1,000-1,500W.

author: calexanian
author_rank: Super Contributor
timestamp: December 18, 2013, 04:51:50 am
content: What kind of wattage are you after?

author: oldway
author_rank: Super Contributor
timestamp: December 18, 2013, 08:43:29 am
content: Loudspeakers have also a R +L impedance.Why worry about a dummy load with a (weak) inductance?

author: Anks
author_rank: Frequent Contributor
timestamp: December 18, 2013, 01:55:37 pm
content: Ive got a ampeg svt to repair for a friend and my dummy resistors are over 200 miles away so I tried using the ones I had here without pushing the amp to hard but it just eats them for dust. Ive got my make shift winding lathe and thought that it cant be too hard to make some.What would be best to use as a former.

author: calexanian
author_rank: Super Contributor
timestamp: December 18, 2013, 02:56:12 pm
content: Umm... No. You can't work on an SVT without a good load. I forbid it.Dangerous Shoals there be ahead. Well, let me qualify that. If its a new one go right ahead. They are junk anyways. If its an old one (Pre St Louis Music) then I will have to call the Engineering Practices police on you.

author: SeanB
author_rank: Super Contributor
timestamp: December 18, 2013, 03:54:17 pm
content: Wooden plank and MIG welding wire, wind for the correct resistance by placing panel pins on the board and zig zag the wire between the pins.