Mottlefeeder Posted May 2, 2020 Share Posted May 2, 2020 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 4 Quote Link to comment Share on other sites More sharing options...
merello Posted May 3, 2020 Share Posted May 3, 2020 Well done. Quote Link to comment Share on other sites More sharing options...
EBS_freak Posted May 5, 2020 Share Posted May 5, 2020 Nice work. Is this mono or stereo? Quote Link to comment Share on other sites More sharing options...
fleabag Posted May 5, 2020 Share Posted May 5, 2020 (edited) 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 Quote Link to comment Share on other sites More sharing options...
Mottlefeeder Posted May 5, 2020 Author Share Posted May 5, 2020 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 1 Quote Link to comment Share on other sites More sharing options...
fleabag Posted May 6, 2020 Share Posted May 6, 2020 Blimey. I nearly understood all that Quote Link to comment Share on other sites More sharing options...
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