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amp 'line out' question


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Depends on with what amp you're planning on doing this with, with some you still need to have a speaker connected and with some you don't.

 

 

i'm using a vht ultra-lead. there's no mention of it in the manual. maybe i'll contact fryette just to be sure.

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Yes I would do that to be safe.

 

The reason why this is different between different amps is because with some amps the line out is basically just the same as using a DI box, with some it is like using a load box, with some it is like the power amp/output is completely switched off and only the pre-amp is active, and so on...

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It does not have to be connected to a speaker...It will bring the signal to any device you plug it into. One one of my rigs, I run the line out to a tuner. On another one, I run the line out to another amp that has built in effects and use that amp to drive the speaker.

 

 

This is a really bad answer. There are some tube amps that will let you run the line out without a cabinet, but as a generalization, this is wrong, dangerous and potentially expensive.

 

I don't know about the VHT. Try it with the amp on standby and see if you get signal from the line out. If you do, you're safe to run it without a cabinet as long as you leave standby on.

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I agree with your 'really bad answer' answer, but disagree with your 'standby' answer....all it takes is one slip of the flipswitch and an output section could arc-n-spark. It'd probably be TOG who'd do it...the guy who doesn't understand what's going on electrically.

 

EVEN if the amp in question has an internal dummyload for the OT, it would rely on internal switching, and I've personally seen some pretty crappy make-before-break switches fail in ways that'd produce section-killing flyback transients. Even if correctly designed, it'd typically be one of the most poorly tested aspects of an amp before it left the production line... We've all seen failed input jacks, right?

 

I despise this part of amp design....how to dummyproof the dummyload.

So many ways to do it wrong.

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I agree with your 'really bad answer' answer, but disagree with your 'standby' answer....all it takes is one slip of the flipswitch and an output section could arc-n-spark. It'd probably be TOG who'd do it...the guy who doesn't understand what's going on electrically.


EVEN if the amp in question has an internal dummyload for the OT, it would rely on internal switching, and I've personally seen some pretty crappy make-before-break switches fail in ways that'd produce section-killing flyback transients. Even if correctly designed, it'd typically be one of the most poorly tested aspects of an amp before it left the production line... We've all seen failed input jacks, right?


I despise this part of amp design....how to dummyproof the dummyload.

So many ways to do it wrong.

 

 

Although I have done it, I don't feel comfortable doing it myself, but there are amps designed that way so that you can record without a speaker connected. Traynor YCS and Marshall JVM come to mind. A little safer perhaps, Mesa F series let you turn the speaker off, and Egnater Rebel 30's has a three-way standby switch. You need to make sure you don't mess up.

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a line out simply is simply an output (tap) from the preamp before it hits the amps power amp section. you can run it to a power amp to power some extra speakers or run it to a mixing board etc. as mentioned, tube amps need a dummy load to run speakerless. the speaker completes the circuit, without a load the ot transformer can fry. a good amp tech can build a dummy load for about $100.00.

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cool, that's unusual, what kind of amp is it?

 

 

It's one a friend of mine (my amp tech) made for me. Basically it's a super-compact 22-watt JCM800. We used an old solid state marshall combo chassis that already had a line out jack on it so he just decided to incorporate that into the new amp.

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thanks for all the input. i've contacted fryette about the question. on the back of the amp there is a power amp mute allowing only the preamp active. would this be used along with the line out function?


hi res pic of back panel:


http://www.sfdamp.com/images/product/UltraLead_OB_Detail.jpg

 

There you go - just hit the power amp mute switch and use the line output as you originally wanted to. The "mute" switch will just shut off the power amp and shouldn't have any effect on the line output. :)

 

And for the record, I agree that in most cases, it's a very BAD idea to run a tube amp without a load connected. Unless there is some sort of switching onboard (as in the case of this VHT), you should generally assume that the amp NEEDS a load connected, and that running it without a load is just asking for your amp to need an expensive repair job.

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I found out that I would need to have a dummyload in order to use the line out without having the sound come from the speakers. Oh well, no big deal... I was just curious and really did not want to damage my amp. Thanks for the advice everyone.

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