5e3- mod aux. speaker jack to line out?

[gsr]

Hello,
The other day I was trolling the interweb and found an excerpt from an amp book by G.W. In his chapter on the Tweed Deluxes he mentions a mod to create a line out from the second speaker jack. Very simple. IIRC he describes placing a 2.2K 1/2 watt resistor between tip of main jack and tip of aux. jack, then a 100R 1/2 watt between tip and shaft of aux. jack. I'm curious if anyone has done it and if it works better than close micing for recording or larger gigs.

[loudthud]

My band tried it on a Harp amp I built. It worked well in a live situation. Somehow, there was no perceivable ground loop noise, but we never really critically evaluated it at rehearsal or in a recording situation.

[Bruce / Mission Amps]

Same thing I do on the Chicago 32-20 harp amp's line out.
I use a 25K "Line Out Level" pot in the circuit so my R values are scaled way up.

[gsr]

Same thing I do on the Chicago 32-20 harp amp's line out.
I use a 25K "Line Out Level" pot in the circuit so my R values are scaled way up.

Should I use the pot in lieu of the 2.2K and leave the 100R in? Also, linear taper? Thanks!

[d95err]

No. The other way around. Leave a fixed series resistor and replace the 100 ohm resistor with a pot connected like an ordinary volume control. Experiment with the values of the resistor and pot to get the desired output level range at all volume levels on the amp. I would try something like a 1.5k-2.2k series resistor and a 100-500 ohm pot. The pot should be logarithmic.

[gsr]

No. The other way around. Leave a fixed series resistor and replace the 100 ohm resistor with a pot connected like an ordinary volume control. Experiment with the values of the resistor and pot to get the desired output level range at all volume levels on the amp. I would try something like a 1.5k-2.2k series resistor and a 100-500 ohm pot. The pot should be logarithmic.

My son is going off to college and may take one of my amps. Will this line out as described be useful for headphones?

[Bruce / Mission Amps]

Kind of... but you must use a high wattage 8 ohm resistor dummy load in place of the 8 ohm speaker.

[gsr]

Kind of... but you must use a high wattage 8 ohm resistor dummy load in place of the 8 ohm speaker.

Thanks Bruce, for helping me see the obvious. Of course, headphones wouldn't really be necessary without silencing the speaker would they?

[d95err]

You could adjust the resistances to get a headphone output. But, it would sound awful because the speaker is a very important part of the sound of a guitar amp. For a decent headphone sound from a line out, you need some kind of speaker simulator.

[martin manning]

Here is the output network in the Marshall Studio 15, a 1980's 2x 6V6 combo amp. The speaker is 8-ohm, so the attenuator resistance values are set up to match. In addition to using it with headphones, the speaker can be plugged into the headphone jack for quiet playing at about 1W. You can just eliminate the line-out divider and jack for your purpose. The amp sounds better without the attenuator, of course, and a speaker emulator is needed for the DI and line-level outputs.

[d95err]

Here is the output network in the Marshall Studio 15, a 1980's 2x 6V6 combo amp. The speaker is 8-ohm, so the attenuator resistance values are set up to match. In addition to using it with headphones, the speaker can be plugged into the headphone jack for quiet playing at about 1W. You can just eliminate the line-out divider and jack for your purpose. The amp sounds better without the attenuator, of course, and a speaker emulator is needed for the DI and line-level outputs.

I really don't see the point of having a headphone jack like this. It is more or less useless, unless your headphones are so crappy their frequency response is close to guitar speaker range...

I guess it would be useful as an attenuator speaker output for the amp though.