Hive Mind,
What's your favorite 2nd-stage (power) IC for headphone drive (to 16 ohms) in a composite circuit? Will likely use the use the OPA1611 as a first-stage in the composite. The power IC should have at least +/-250mA of drive current and at least +/-12V rails. I want a composite design in order to get super low THD and noise.
I've not checked lead-times, but these are the candidates I've found that meet my criteria, so far.
OPA551
OPA564
LME49600 (this one looks great, and I've had good sonic experience with the old LME National parts, and it won't need as much FB compensation)
TPA6120 (ditto)
BUF634
Another approach would be to parallel some high-performance opamps for 250mA performance. The performance of these opamps is so dang good that I wouldn't need a composite solution. I'm looking at these:
OPA1655 (x3 in parallel)
OPA1622 (x2 in parallel)
Appreciate your time.
DD
What's your favorite 2nd-stage (power) IC for headphone drive (to 16 ohms) in a composite circuit? Will likely use the use the OPA1611 as a first-stage in the composite. The power IC should have at least +/-250mA of drive current and at least +/-12V rails. I want a composite design in order to get super low THD and noise.
I've not checked lead-times, but these are the candidates I've found that meet my criteria, so far.
OPA551
OPA564
LME49600 (this one looks great, and I've had good sonic experience with the old LME National parts, and it won't need as much FB compensation)
TPA6120 (ditto)
BUF634
Another approach would be to parallel some high-performance opamps for 250mA performance. The performance of these opamps is so dang good that I wouldn't need a composite solution. I'm looking at these:
OPA1655 (x3 in parallel)
OPA1622 (x2 in parallel)
Appreciate your time.
DD
I think drizdraz is looking for a 24V max chip for VERY high level.
@angchuck Thanks for that. Good find. Sadly, it is obsolete. I wonder if anyone has ever tried a differential composite approach? High-performance diff-amp input stage followed by a true differential power stage, with differential feedback. I see no reason why it wouldn't work. We'll try it.
Also, qstn for mod: why does the most recent post (in this case #6) not have a "Quote" option? Posts 1 thru 5 all have the "Quote" option.
Also, qstn for mod: why does the most recent post (in this case #6) not have a "Quote" option? Posts 1 thru 5 all have the "Quote" option.
BUF634 has been superseded by BUF634A -- but you will find complete PCB's with the older chip available on EBay.
(Had one, but now use the Marsh HPA which is all discrete)
(Had one, but now use the Marsh HPA which is all discrete)
By design because if you are replying to the post above then you shouldn't really be quoting it as standard practice 🙂
https://www.diyaudio.com/community/threads/change-log.380502/post-7243008
I tried lt1280 and lt1115 with less satisfaction than the ad815. U probably could find some ad815 on eBay still.
Ultimately, an amb m3 or whammy would sound nicer than most op amp designs I built point to point. But I am still fond of the Ad815’s unique sonic qualities.
Are you looking for a portable or a desk top rig ?
Ultimately, an amb m3 or whammy would sound nicer than most op amp designs I built point to point. But I am still fond of the Ad815’s unique sonic qualities.
Are you looking for a portable or a desk top rig ?
Yes, and the usual distributors have no stock. I do find it at Futurlec: https://www.futurlec.com/AnalogDevices/AD815AYpr.shtml The guitar-pedal gang uses Futurlec for obscure chips. I forget if they are the ones with slow shipping or the annoying coupon timing. Clearly not ideal for mass production. Could work out for personal builds.
Rochester has them but $300 minimum order.
I would think by now AD815 on eBay is a reckless crap-shoot.
I ran two LME49600 in parallel with an OPA1611/12 controlling opamp in a composite in the HP-1. The rail voltage was ±18 V if I recall correctly, though you could as easily run it on ±12 V if you'd like. I did find that the OPA1611+LME49600 combination tended to oscillate in the 100-150 MHz range if not compensated properly. This was not captured in the simulation models. I was able to get it to behave. Having access to a spectrum analyzer or >100 MHz scope will be handy during prototyping.
The LME49600+LME49720 combination performs almost as well and doesn't have the RF instability issues.
The TPA6120A2 and BUF634A are good candidates for a composite amp as well.
Tom
The LME49600+LME49720 combination performs almost as well and doesn't have the RF instability issues.
The TPA6120A2 and BUF634A are good candidates for a composite amp as well.
Tom
6L6 and I are very, very pleased with the LH0033, which is available as NOS (here) .
Datasheet attached.
I remember that part!! It was waaay ahead of its time. FET input. Love those old TO-5 cans. Nice heat sink 🙂
LOL That's awesome. That's from back when employees of semiconductor companies were allowed to have fun. Same with Bob Widlar's classic ad.
Tom
Tom
Hi Mark,
Was the design publicly available? I have a lot of these parts.
Kindest regards,
M
Was the design publicly available? I have a lot of these parts.
Kindest regards,
M