Does an amp have to have a speaker load?

Rich Gibson · Post by **Rich Gibson** » 10 Jul 2001 11:28 am

I've found a great recording tone by simply running a line from the head phone jack of my mpx-100 into a Tascam 4 track.I'm going into my Matchless head with the mpx-100 in the effects loop.Does it hurt the amp not to be driving a speaker? I know there's other options but I have everything set up this way to play live, plus it seems to work...Thanks for any and all input and advice.
Rich Gibson

Jeff A. Smith · Post by **Jeff A. Smith** » 10 Jul 2001 12:01 pm

Rich-

If your Matchless is a tube amp, like I think it is, get a speaker or a dummy load on that thing right away! You will blow the output transformer quick.

Only a solid state amp can be run without a load.

Maybe you can go to an electronics store and get one or two big resistors to use as a dummy load, if you don't want the noise of a speaker. Ask someone knowledgeable what you need to serve in the place of a speaker with the ohm and wattage values of what's in your Matchless.

Come to think of it, I'm not sure how wise it is to use a dummy load for an extended period of time. It's okay for workbench purposes. Power attenuators that allow amps to be played at full power at a fraction of the volume are variable resistors, and they are said to shorten the life of the output transformer also. [This message was edited by Jeff A. Smith on 10 July 2001 at 01:04 PM.][This message was edited by Jeff A. Smith on 10 July 2001 at 01:11 PM.]

Michael Holland · Post by **Michael Holland** » 10 Jul 2001 12:14 pm

I'll give ya $150 for the Matchless when it blows up.

------------------

Emmons Push Pull S10 | Peavey Session 400 | '52 Fender Lap Steel | Goodrich L120 & Matchbox

Rich Gibson · Post by **Rich Gibson** » 10 Jul 2001 1:20 pm

Well,I guess that answers that.Jeff,thank you for your timely response.You saved me some serious dough,of course there's always humanitarians like Micheal to pick over the carnage(humour)
How about this-preamp send to tape-mpx in tape effects loop.The Mathchless manual says to put a shorted 1/4" plug(old 1/4'& bend the hot and ground together?) in the return jack to bypass the power amp.This would circumvent the need for a speaker load?
I'm a tech spaz,what can I say.
Thanks
Rich

Michael Holland · Post by **Michael Holland** » 10 Jul 2001 2:32 pm

Seriously Rich,

There must be a load on the output of your amp. Without a load, your output tranformer thinks it's a transducer and will not last long. And, in the event that you mistakenly turn on the amp without a load on it, you should plug in a speaker instead of turning the amp off. Some of my Mesa amps feature a 'silent record' feature that mutes the output, but there must be a speaker plugged in even when the silent record is used.

But my offer still stands.

------------------

Emmons Push Pull S10 | Peavey Session 400 | '52 Fender Lap Steel | Goodrich L120 & Matchbox

ajm · Post by **ajm** » 10 Jul 2001 4:34 pm

What the other guys said: NEVER run a tube amp without a load plugged in (if you care about the amp, that is).

There are two other possible scenarios that I can think of to give you what you want, but I'm not too familiar with the Matchless so someone else may have to chime in.

1) If it has an effects loop in/out, run the preamp output to the MPX, and run that into the mixer. Instead of running the MPX output back into the power amp input of the Matchless, insert a plug only (with no cable attached) into the power amp in. This may connect the loop but basically feed the power amp with no signal so you can turn the (pre)amp up as loud as you want and have nothing coming out of the speakers. But leave the speakers connected.

2) Feed the MPX with the preamp out, then go to the mixer. To kill the speakers, just pull out the output tubes.

Once again, I don't think that either of these will hurt anything, but I'd feel better getting a second opinion from a couple of other members who post here often that seem to know their amp stuff.

Donny Hinson · Post by **Donny Hinson** » 10 Jul 2001 8:43 pm

Dan Tyack · Post by **Dan Tyack** » 12 Jul 2001 7:56 pm

I've got one comment: THD Hotplate.

http://www.thdelectronics.com/

------------------
www.tyacktunes.com

Rich Gibson · Post by **Rich Gibson** » 13 Jul 2001 12:43 pm

Thank you all for taking the time to respond.Yesterday I just waited till the neigbors left & miked the amp & ran a line from the mpx.
It does say in the manuel that you can just run the preamp by using a shorted plug in the return jack,but it wasn't quite the same.Plus I'll probably screw that up and Micheal would get his burned out Matchless.Although the way the prices are going on these things I think I'd hold out for...I don't even want to think about it.
Dan the THD looks interesting I may look into one

Thanks again
Rich

Hamilton Barnard · Post by **Hamilton Barnard** » 18 Jul 2001 7:38 am

Hotplates are great. Mine takes a serious pounding up against my Marshalls and has never batted an eye.

They also have an adjustable 'line out' so you can send the speaker signal right to the board. They can be bought for around $280.