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I don't always do this, but I tried it once the other day and it worked then, I just want to fully verify that I'm not going to screw up my beloved tube amp. The wiring is sort of complex so I'll try to be descriptive...

The amp is a Peavey 5150 120w tube head, it's got an FX loop, and a preamp out. I had my guitar going to the high gain input on the amp. Then I had a cable going from the FX send to my DI box and into my interface to be recorded. I had the speaker out of the amp connected at all times to my 4x12 cabinet to hopefully show the head the correct impedance through the venture. Then (I forgot why I did this to be honest, but it was either because there was no sound at my DAW, or because the sound at the cabinet was too loud. I struggled with both of those issues yesterday and this rig solved both those problems) there was a cable plugged into the amp's FX Return but it wasn't connected to anything else. The amp was on and the standby switch was in play mode, there was a TV volume sound coming from the cabinet that did not (by my memory) change with the amp's Master volume knob. There was no load box present.

Safe? Smart?

JakeAC5253 wrote:I don't always do this, but I tried it once the other day and it worked then, I just want to fully verify that I'm not going to screw up my beloved tube amp. The wiring is sort of complex so I'll try to be descriptive...

The amp is a Peavey 5150 120w tube head, it's got an FX loop, and a preamp out. I had my guitar going to the high gain input on the amp. Then I had a cable going from the FX send to my DI box and into my interface to be recorded. I had the speaker out of the amp connected at all times to my 4x12 cabinet to hopefully show the head the correct impedance through the venture. Then (I forgot why I did this to be honest, but it was either because there was no sound at my DAW, or because the sound at the cabinet was too loud. I struggled with both of those issues yesterday and this rig solved both those problems) there was a cable plugged into the amp's FX Return but it wasn't connected to anything else. The amp was on and the standby switch was in play mode, there was a TV volume sound coming from the cabinet that did not (by my memory) change with the amp's Master volume knob. There was no load box present.

Safe? Smart?

I reckon that as long as you've got the speaker cab connected up to the speaker out socket on your amp, and that you've got your master volume set to zero, you should be okay with sending a signal from the FX out socket to a DI box and then to your Audio Interface, that is, you shouldn't do any damage to your amp, you may need to use some kind of speaker cab simulation plugin on the DAW track you're recording onto, also check to see if you've got any pad switches set correctly as they may be attenuating the signal too much, with nothing plugged into the FX in socket, you should get nothing coming through the amp's speaker cab....

Usually the way the FX in/out are wired up in amps is that when nothing is plugged into the FX out socket, a switching system in the socket connects to the tip connection so that the signal from the preamp passes to the FX in socket and then onto the power amplifier section, when you plug a lead into the FX out socket, this opens the switch so that the signal-path to the power amp section is broken, removing the lead from the FX out socket re-establishes the signal-path connection....

Basically you have your output out of the pre, and the power amp disconnected by inserting the "not connected to anything" cable into it. Just to be safe I'll use a shorted cable (shorted as in short-circuit, tip connected to ground) to be sure that the power amp will not get any signal while you're playing/recording.

Regards,
Juanro