in-ear monitor for bass guitar

[Milothicus]

I'm hoping to build an in-ear monitor and need some help. i basically want to build a small box with a 1/4 input, a 1/4 output to go to my amp, and a mono 1/8 output with volume control to go to an earpiece.

Now, i've only built one pedal (orange squeezer) so i just want some confirmation of my plans....

If i use the splitter from http://www.runoffgroove.com/splitter-blend.html and put one output to the 1/4 output jack, the other signal can be used to the input of a headphone amp?

what's the simplest amp i can build for this? i don't even really care if the sound is terrible, i just want to be able to hear the notes i'm playing.

any recommendations? or will any opamp-based amp work?

[spongebob]

For an opamp-based amp, you could build something around the famous 'cmoy' headphone amp over at headwize, it uses the TI OPA134 opamp which can deliver up to 35mA output current and works well with headphones.

I think you could build the whole thing with one dual opamp, one half for buffering the input signal (high input impedance), and the other half for the headphone amp. The output of the first one feeds the headphone amp and also passes the signal on to the output.

Hope this helps!

[David]

There's another headphone amp over at HeadWize that's a whole lot easier.  Check out the article by Alan Campbell about his LM386 headphone amp.  I built this back around Christmas to use with my breadboard.  There's a build report I filed that might be useful too.  Only thing is, I haven't tried it with bass, but at worst you might need to tweak a cap or two.  So far, the response seems pretty transparent.

[Mike Burgundy]

Be mindful of a couple of things:
in-ear monitoring works well, but only if combined with proper hearing protection. The pro stuff has an earplug (at leat 10dB of protection, often more) with the headphone integrated. This allows you to hear well and protect your ears at the same time. If you use a regular headphone to cut through stage noise, you'll need to set it louder. A lot. This means the headphone needs to be louder than the 110dB drummer youre standing next to, and the 114dB guitar amp, and.. Unless you have (real) earplugs with speakers in, or one of those military tank-driver headphones (which don't do bass, though), don't expect to use this at stage volumes without risking your ears.
Also, bass frequencies tend to mud up whatever you're hearing without cutting through - this is why a lot of bassists like to feel their bass, it increases psychological feedback.
It helps onstage to actually *cut down* on bass on your amp and focus on the mid area, aim the speakers across the stage and don't stand too close to the amp.
Bass frequencies need some yards to "develop" from the speaker. If you stand too close, you can't hear yourself, but the rest of the stage (and room) is swamped. I like to actually stand on the opposite side of the stage on smaller venues.
That said, a small simple booster/preamp (to get up to line level) and one of the headwize amps will do. preamps and boosters (perhaps with a baxandall tone stage and volume control) are in the schematics sections.
hih

[Milothicus]

well, i do have some of the koss "the plug" earphones. i may just use one of them. i do boost the mids on my amp, but i find that i either can't hear myself, or i can, and no one can hear anything but me..... i'm usually not too close to my amp, either.....well, i think i'll try that 386-based amp (i know i can get them easily nearby) and see what happens.

[Ansil]

there is another version of the lm386 type that can be used, that has better input z.

and is a dual poweramp  not quite as loud as the 386 but under teh right conditions it can work just the same and be as powerful ie voltage and such,

personally  would try it as it will giv you operating v down to 1.8v and still work good  accordign to the datasheet,

and u get the benifit of having a preamp buffer and a speaker driver

also using it at lowervoltages will still give you plenty of juice, but won't fry your ears like a 386 at 9v


http://www.ben.cz/download/121098/tda2822m.pdf also its 8 pin dip too.. ymmy

[Milothicus]

i'm not worried much about input impedence. i've got EMG active pickups running at 18V, so i'd just build that one at the line level and see if that works. if not, i'll add the extra components.