Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: rosenfeld88 on October 25, 2011, 09:37:02 am

Title: Extension Cabinet
Post by: rosenfeld88 on October 25, 2011, 09:37:02 am

Hi, I'm building an extension cabinet for my amp and I have a quick question about input jacks. I was looking on this website, and I noticed that there are two switchcraft input jacks for sale and I wasn't sure which one I would need. Since I'm only building an extension cabinet and my guitar would not plug in directly to the extension cabinet I think that I need the Switchcraft 11 jack, but I wasn't sure. Which of the two input jacks listed do I need?
http://www.hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=JacksPlugs&ORDER_ID=450148010 (http://www.hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=JacksPlugs&ORDER_ID=450148010)

Thanks

Title: Re: Extension Cabinet
Post by: PRR on October 25, 2011, 11:32:15 am

It's not really about guitar, it is the switch.

You can use the 11 for guitar input but if the amp is on with nothing plugged-in it will pick up all the hum/buzz/radio in the air. We use the 12A so that when there is no plug, the input is shorted to ground.

We also use the 12A on low-medium power tube amp speaker outputs. If there is no load on a tube amp and you put large signal through, high-voltage kicks can damage the OT. It is usually best to short the amp output to ground. (Tube amps over 100W and all transistor amps usually should NOT be shorted.)

For the remote cabinet there is no reason to short anything. Hum/buzz/radio "does" get in, but a speaker won't make audible sound even with its wires laying on a neon beer-light.

For one jack for speaker, use the 11.