I had that discussion yesterday with 6L6, as he's ready to start laying out
pcb's, and I noted that I need to check for the possibility of low frequency
motor-boating if the signal source has a capacitor in series. This could be
addressed by using a buffer with a DC output value, but possibly as easily by
adjustment of feedback impedance. No high frequency issues are anticipated.
Anyway, I'll report back after I fire one up and check.
😎
I've come to appreciate the better temperature coefficients and sharper
corner to the LED used in the opto. Otherwise it's no big deal.
😎
For a regulated +60V PS, what would be the minimum recommended capacitance per rail that can keep the 3.2A draw nice and happy? I know many would splurge but I have some potential real estate issues.
Regulated is nice, but not particularly essential. The PSRR is on the order of
40 dB, so if you want 100 uV of noise at the output, the supply needs less
than about 10 mV ripple. A quick sim shows that two 47000 uF separated
by .5 ohms for the RC filter will get you about 7 mV rms.
You can do more capacitance or resistance if you want.
😎
40 dB, so if you want 100 uV of noise at the output, the supply needs less
than about 10 mV ripple. A quick sim shows that two 47000 uF separated
by .5 ohms for the RC filter will get you about 7 mV rms.
You can do more capacitance or resistance if you want.
😎
Thanks, papa. Exactly what I needed. The other parts are on the UPS truck today...;-)
Ahhh yes LFO.........the chance of a capacitor in series with the input is probably pretty high since most sources and preamps will have an output capacitor.
The talk of PCB's being laid out is exciting!!
Thank you for all your work, there are some exciting things in the near future 🙂
Quite a few of us do not have source equipment with the output impedance you mentioned (eg B1 is 1k output impedance), will there be the option for a cascoded jfet buffer at the input on this amp for us poor souls (sought of like F6)?
Last edited:
use F4 , F6 -like buffer
so , JFet complementary one
pretty low output impedance
you can double them , if you wish , for more ooomph
or you can use superduper diamond buffer , but tweaked for nice 2nd
so , JFet complementary one
pretty low output impedance
you can double them , if you wish , for more ooomph
or you can use superduper diamond buffer , but tweaked for nice 2nd
The optocoupler is used for biasing the outputstage.
At the input is the LTP gain stage.
Did I mix something.....?
At the input is the LTP gain stage.
Did I mix something.....?
oh I see my posting #150 was too late It was thought as answer for posting #140.
in context with ZM s posting #149 my words didn't fit any more, sorry....!
in context with ZM s posting #149 my words didn't fit any more, sorry....!
Last edited:
I guess it's time for a small daughterboard of that nice push pull jfet buffer, with that nice distortion adjusting pot in the middle 🙂
It's about time we came up with another Pass inspired preamp.
I'm considering jfet buffer input then volume pot then a 2 parallel pair jfet buffer output.
Last edited:
I did not recollect the optocoupler, probably because I don't recall the J2 or M2 schematics being public knowledge, or being shown on this forum. Let's keep it that way until FW has sold out of these models. 😉
we have a nice example for using the optocoupler for biasing an output stage and even the LTP already here in the Pass Labs forum by Nelson himself
http://www.diyaudio.com/forums/pass-labs/262367-mu-monster.html
The Mu Monster is such a nice idea…… 🙂
http://www.diyaudio.com/forums/pass-labs/262367-mu-monster.html
The Mu Monster is such a nice idea…… 🙂
Attachments
- Status
- Not open for further replies.