Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jeff on August 01, 2015, 01:12:13 pm

Title: Cliff Jack wiring diagram(please check for errors)
Post by: jeff on August 01, 2015, 01:12:13 pm

There are a couple posts about how to wire output jacks so I thought I'd draw some diagrams. Please post if you see an error or if these look good to you.(don't use these until they are comfirmed good)
 
1) Simple non shorting jack
2) Shorting jack
3) 2 jacks one MAIN(shorts if not used) and one EXT.(use if needed but does not short)
4) Seperate 4/8 ohm jacks(non shorting~does not short if nothing is plugged in)
5) Seperate 4/8ohm jacks(shorts 4 ohm tap if nothing is plugged in) I have it so 4ohm tap shorts when nothing is plugged in, Is it better to have the 8 ohm tap short rather than the 4 ohm?
6) Two "output" jacks(use either one~only shorts when niether is used)
 
Last pic is just an alternate wiring for 5 and 6. Dunno know which, if either, is better. Probally 1st one: less moving parts.
 
Also on another post someone wrote that only Cathode Biased amps should have shorting jacks and Fixed Bias amps should not.
What's your opinion?
I always thought ALL tube amps should have shorting jacks and most schematics(I.E. Twin Reverb) have them???
Having a speaker load is the right thing to do, but, which is the worse condition for a cranked fixed bias amp: having the OT open or the OT shorted? I'm sure having the OT shorted is not good but is having the OT open better or worse?

Title: Re: Cliff Jack wiring diagram(please check for errors)
Post by: jojokeo on August 05, 2015, 03:26:47 pm

Hi Jeff, your switching looks okay but remember simpler is better and more reliable usually, besides figuring things out down the road when you may have forgotten what you used to do back in the day?  :laugh:

I haven't heard that OT info on whether to use shorting jacks or not, but my opinion is shorting. It's safer and/or the lesser of two evils for the OT to be shorted than open / infinity ohms on the tranny. Also, if cathode biased AND single ended both, SE trannies can be more expensive to replace when/if they are higher wattage units.

If a speaker is not plugged into the output jack, you are better off just plugging the speaker in rather than rushing to turn it off. More damage can be caused by this because of flyback voltage spikes and arcing caused to the windings.

I normally buy cheap power resistors and solder them into the switching side of Cliff jacks. It doesn't need to handle full power and won't just burn up instantly like a fuse and gives you plenty of time to find your speaker's wire & plug. See photo: