Silly question, will I blow it up?

Andy Schick · Post by **Andy Schick** » 14 Apr 2006 6:25 pm

Looking to use head phones for home practice. Will this work?
Guitar to VP to input in my Webb amp. Unplugging rear 1/4" speaker jack and instead going from there to the input on my Lexicon MPX 100. Then output to head phones. Keeping all VOLUME controls off to start will this work.
All responses greatly appreciated.
Thanks
Andy

Cliff Kane · Post by **Cliff Kane** » 14 Apr 2006 7:17 pm

I don't think it's a good idea to go fron the speaker out jack into an audio device. I think you could blow up the Lexicon and possibly hurt your amp. Is there a preamp output jack, or an effects loop send jack? I think you could go into your Lexicon from either of those points.

Curt Langston · Post by **Curt Langston** » 14 Apr 2006 7:25 pm

Ditto what Cliff said. Run your effects through the effects loop on the Webb.

Lee Baucum · Post by **Lee Baucum** » 14 Apr 2006 8:00 pm

Andy - The left channel output on a Lex MPX-100 was designed to drive a pair of headphones. Have you tried that? You don't really need to go through the Webb.

------------------
Lee, from South Texas
Down On The Rio Grande

Mullen U-12, Excel 8-string Frypan, Evans FET-500, Fender Steel King

Andy Schick · Post by **Andy Schick** » 15 Apr 2006 4:38 am

I guess I am looking for the best of both worlds. Thought I might be able to use the eq of the Webb without having to get a pre amp.Thanks
Andy

Michael Garnett · Post by **Michael Garnett** » 15 Apr 2006 6:20 am

That's probably a pretty bad idea. Running an amplified signal that might be in the tens of volts from the poweramp into an input that is made to take at most a volt or two is a recipe for disaster. At the very best, it'll sound horrible. At the very worst, once you plug it in and turn up the volume, you'll completely fry the input side of the Lexicon, and possibly mess up the poweramp's output, because it's looking for a speaker, not a preamp's impedance.

I'd try doing what the other guys said, putting the lexicon in the effects loop of the amp (if there is one) and leaving the master volume of the Webb on zero. You might miss out on the total tone shaping of the EQ if it's a pre-eq loop, but at least you'll have the help of the preamp circuit.

-MG

Greg Cutshaw · Post by **Greg Cutshaw** » 15 Apr 2006 6:50 am

Not sure if your Webb amp is the newer model with the effects loop. Best to keep an 8 ohm load on the output, break the effects loop and feed the Webb FX out to your headphone system. On some amps you can put a shorting plug in the FX Return or just insert a phone plug in it to open up the circuit which will disconnect the Webb preamp from the Webb power section, keeping the amp's output quiet.

Greg

Jim Sliff · Post by **Jim Sliff** » 15 Apr 2006 12:16 pm

It's not probably a bad idea. It's a BAD idea.

To answer - yes, you WILL blow things up.

If you don't have a headphone output one can usually be wired. Search the web - there are articles on the subject on various amp sites.

Andy Schick · Post by **Andy Schick** » 15 Apr 2006 2:13 pm

Thanks to everyone.
All advice well taken.
I will not try this.
Thanks again.
Andy

Matthew Prouty · Post by **Matthew Prouty** » 15 Apr 2006 4:33 pm

Amps and headphones.

The output of your average amp is 4 and 8 ohms. Sometimes the builder will get silly and put on a 16 ohm jack. The rule of thumb is to run as close to the output as possible. You can run a 16 ohm speaker on the 8 ohm jack fine, but not the 8 ohm speaker on the 16 ohm jack without stresing the output transformer.

The average speaker is around 8 ohms.

The average headphone can range form 100 ohms to 600 ohms. This is a big difference. This will not work well and will result in damaged equipment before to long.

There is a solution for this. If you are handy and have a know how you can get a transformer wound to run headphones. You just need to find out what the input to the tranny is and determine the output you want. You would them mount the new tranny, can be in an external unit and install a switch in the line from the output of the amp prior to the original tranny. Flip the switch and the output is rediverted to the new tranny and the headphones.

Important note: Make sure you always have a load (speaker) connected to the output of the amp or you will burn it up fast.

It is actually quite simple to make a headphone amp. I used the 5F1 Fender champ schematic. I simple replaced the output tranny for a 5K to 100 ohm transformer. Tons of clean headroom thru the headphones and incredible tube tone.

M.