I have scratched out my 'New Headphone Amp" schematic and before I go ahead with the build I would like to simulate it. I have heard of Spice, is there a free version? Is it difficult to simulate? I am after the Bode plots to decide if I have the correct bandwidth and response.
The amp,
option 1, input stage is a Fetzer valve to an op-amp. Total gain to be 8-10 out of op-amp. Next block is the tone stack which is an active bass/treble circuit.
Next block is the channel mixer --> to allow both cancellation of common sounds and mixing left to right - right to left.
Next block is a current doubler to output.
option 2, same as 1 except delete the Fetzer valve portion.
Power will come from one 3.7 V 2200 mAh lithium cell fed to a DC/DC converter-booster with a range of 5-15V. PSU will use a virtual ground chip with the leftover op-amps used to balance the current fed to each +ve and -ve rails. A mini USB port charger with pass through so it can be charged while playing (also need a charge monitor circuit).
Goals:
1) to have an amp that will provide a full range signal to my ER-P4 (altered to S4) phones.
2) to be able to tweak the frequency response to suit the source files and my mood.
3) to be able to expand the soundstage out of my head by creatively mixing left and right signals with some attenuation.
4) to not have to continually pay for 9V batteries and use any USB port to recharge the LiPo cell.
5) th have it fit into a case with a similar foot-print as my iPod.
I'll be spending some time this week in EagleSoft drawing the schematic so I can post it in a few days.
What I am looking for: some help in board design and spice usage, also comments about my op amp choices, OPA4228 and TLE2084 first 2 blocks TLE second 2 OPA.
Cha Gheill!
