Re: [Harp-L] SF Champ run at 2ohm?

[MARK BURNESS <markwjburness@xxxxxxxxxxxxxx>]

Champs want to see a 4 ohm speaker load, not 3.2 ohms. 3.2 ohms is roughly the 
dc resistance of a 4 ohm speaker's voice coil ("impedances" are AC rated).

Running the champ into a 2ohm load with a 6V6 power tube will increase AC 
currents accross the OT primary because the OT primary impedance will drop, 
reflecting the new speaker load ( to about 3.5K & I would be reluctant to run a 
6V6 into much less than 5K)... I wouldn't do it. 


What you could do however, is increase the power tube cathode resistor to 
680-800ohms (<50mA plate current) @ 5W and increase the power tube cathode 
bypass cap rating to 100v (same "uf" rating) & now you can run a 6L6/5881 tube. 
These will provide a good match for the Champ OT into a 2ohm load.




________________________________
From: joe hagins <joe_hagins@xxxxxxxxx>
To: Harp L <harp-l@xxxxxxxxxx>
Sent: Wednesday, 14 September, 2011 23:02:57
Subject: [Harp-L] SF Champ run at 2ohm?

So I have been planning out all the mods for my '74 Champ and I want to run two 
8" speakers (I will have a new 2x8 combo cabinet made) I know that amp wants a 
3.2ohm load. I already have one of the speakers that I like the tone of (4ohm) 
8A125 and want to add a (4ohm) 8F150. Is it safe to run a SF Champ at 2ohms? I 
really want to get around having to buy two new 8ohm speakers (and rebuy another 
8A125) to get a 4ohm load which I know is a lot closer to 3.2. Any info would be 
tons of help with my planning this. The reason I want two 8" is that I can run 
two different sounding speakers to help get a more complex range of tones
Cheers,

Joey Anchors



http://joeyanchors.wordpress.com/