Just finished a lockdown project

[Mottlefeeder]

 

Four jack sockets, three switches, three opamps, two pots and one 9V battery in a box not much bigger than a tv remote.

It's a: Hi-Z buffer with switched gain + 18dB/octave fixed frequency HPF + headphone driver + passive headphone monitor mixer with volume limiter, and I don't think all that would fit in the title box.

The circuit evolved as I built it, so I have not got an accurate copy yet. If there's any interest, I can sort one out.

David

[merello]

Well done.

[EBS_freak]

Nice work. Is this mono or stereo?

[fleabag]

Mottle - what is it  ?

If its a headphone amp, why all the jack sockets and op amp switches ?

I'm a bit green on these sort of things

 

Edited May 5, 2020 by fleabag

[Mottlefeeder]

OK, A bit more information. It's two almost separate circuits -

Firstly, I use a passive bass and long cables/not hi-z inputs, so it is a simple bass preamp, giving a hi-z input, an HPF, and an output to FOH or backline amp. That's two jack sockets on one side, (one in and one out) and a gain selector: 0dB or 10dB.

Secondly, I usually create a headphone monitor mix with a small mixer on top of the back-line amp. I take a feed from the main PA, and a feed from my bass amp, and an ambience mic, and feed them back to me in stereo (acually two channel mono since I put me on the left and everything else on the right). With this box, I can select left only, right only or both and I mix them down to mono and feed them to the headphones. That's the other two jack sockets, (stereo in and headphones out) and the selector switch.

Since I have the bass signal in the same box as the headphone mix, I added the switch in the battery compartment which gives me the option of substituting my live bass sound for the left monitor channel, so I can take a mono feed from the FOH mixer, or a stereo feed from a Zoom or Tascam recorder, and still control 'me or them' at my end of the cable.

I use a 'figure of eight' twin microphone cable to connect my bass/IEM to my bass amp/monitor mixer. It's reasonably discrete and keeps the two sets of signals apart. The compromise is that it isn't an instrument cable, so I need the hi-z buffer - that was the starting point.

David

[fleabag]

Blimey.  I nearly understood all that