DIY tube amp with passive throughput option?
Sep 16, 2009 at 7:59 PM Thread Starter Post #1 of 8

revolink24

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Has anyone ever tried to take an amp and incorporate a switch or other means of alternating between a simple line option that bypasses the amplification circuit, so that if I powered one through a dap or computer output I could use their integrated amplifier so as not to wear our the components in the amplifier (ie tubes) when just listening to background music or gaming? If anyone has, I would like to know their methods and their results.
 
Sep 16, 2009 at 9:02 PM Post #2 of 8

UglyJoe

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??? Just use the comp output when you need it. Bypassing the "amplification" portion of the amp won't matter much as far as tube life. Quiescent dissipation is typically much higher than signal dissipation... just because the amp isn't being fed a signal doesn't mean that it's not working... hard!
 
Sep 16, 2009 at 9:04 PM Post #3 of 8

revolink24

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You missed the point of my question, I wanted to incorporate a switched that bypassed the amp entirely, so I wouldnt have to stand up and mess around with the back end of my case to switch to not using the amp, just flicking a switch on the amp....
 
Sep 16, 2009 at 9:48 PM Post #4 of 8

jnewman

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I don't recall seeing anything like that in stereo equipment, but most guitar effect boxes do that (i.e., the power switch has an on/active position and an off/bypassed position). It could be as simple as a power switch with enough extra poles to pass the inputs to the outputs in the off position or as complicated as a relay board that operates off of the "power switch" (would would operate the relays, one of which would be the actual power on/off bit) or even a microcontroller something or other.

You'd want to be careful about things though because amps continue to run for a while after you flip the power switch. You wouldn't want to dump power directly from the output of your amplifier before the capacitors ran down into the output of your source/input of amp. That could have some nasty side effects. You'd want to use something break-before-make and disconnect the amp output from the headphone jack before you connect the input to the headphone jack. This has its own problems because some tube amps self-destruct if you operate them into an open circuit. For a tube amp, you might have to switch the output to a resistive load with a make-before-break before you switch the input directly to the output.

There may be problems I'm not thinking of so you use my advice at your own risk and would be wise to listen to someone more experienced than I am.
smily_headphones1.gif
 
Sep 16, 2009 at 10:10 PM Post #5 of 8

DKJones96

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What tubes are you using?

The reason I ask is some tubes this is more of an issue than others. For example, the 6922 tube from Electro Harmonix is supposed to be good for at least 15,000 hours. That's almost 2 years of 24/7 use.

The only thing I'd worry about having a switch like that is you'll be turning off and on the tube a lot more than normal if you decide to listen to music then play a game and go back to it and that's where most tubes die.
 
Sep 17, 2009 at 3:42 AM Post #6 of 8

Uncle Erik

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I would build a switch box separate from the amp. Run your inputs into that and include a headphone jack. Give it an output for a headphone amp, so you won't have to run the amp unless you're specifically listening to it.

If you wanted to integrate everything into one box, I suppose you could. The easiest solution would be to have two headphone jacks on the box. One for the amp and one for everything else. You'd have to unplug your cans, but that's not too bad.
 
Sep 17, 2009 at 3:49 AM Post #7 of 8

Iniamyen

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If I'm understanding your question correctly, what you want is a loop out. Just connect the amp's inputs to some outputs in the same box. Then you can hookup whatever you want, whether or not the amp is powered.
 
Sep 17, 2009 at 6:07 AM Post #8 of 8

rshuck

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Quote:

Originally Posted by Iniamyen /img/forum/go_quote.gif
If I'm understanding your question correctly, what you want is a loop out. Just connect the amp's inputs to some outputs in the same box. Then you can hookup whatever you want, whether or not the amp is powered.


X2 on this

You'd literally just put the input and loop out RCAs next to each other and connect them together.

Right RCA Input Center pin would go to both your right channel tube amp signal input AND to the Right RCA Loop Out Center pin.

Left RCA Input Center pin would go to both your left channel tube amp signal input AND to the Left RCA Loop Out Center pin.

The ground for all four RCAs can be directly connected and would also be connected to the tube amp's signal ground input.



Can't seem to find an image right now, but if you're going to buy a new amp, look for one with a loop out. If you're self-building, just add another set of RCAs.
 

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