That is true, but the problem is that i have +-30Vdc after the rectifiers because of 240Vac here in France and 22Vac at the output of the Transformer for 18Vac with the AMGIS L01-6364.
Carl what do you thing? do you know an equivalent to the NE5534 for 30Vdc and Plus or you do you have an other option?
Yea, that voltage is much too high. I had thought France had 220v mains. 240v is a surprise to me! Your simplest path would be to swap out the transformer for a lower voltage equivalent. The AMGIS L01-6363 at 15v secondaries or better yet the AMGIS L01-6362 at 12v secondaries would drop in and drop your voltage to the proper levels.
I agree with Carl. You can swap the opamp with a higher voltage one but performance will suffer.
Jan
Hi!
I'm on France too, and was faced with the same issue.
Plus the fact that AC is sometimes very unstable and can jigg from 220 to 260 V in an instant.
Just build another power supply and shoot for 15V.
I also have it in a separate enclosure. and much lower ground noise by the way....
No issue for 4 years, wonderful music.
JM
Last edited:
I really look forward to building this preamp. I'll deviate slightly from the BOM and use NP green UES electrolytics only at C2/4 and C45/46. Everywhere else will get Silmic-II. Dale RN55 resistors throughout, my usual go-to part. I've had a bunch of productive email exchanges with Carl. Any builder recommendations and tips appreciated!
BK
BK
Thanks, with everything connected i have 21.5VAC at secondary and 27.3VCC after the rectifiers for 241VAC at primary
If i do the math with a 12VAC transformer, i should have 20VCC after the rectifiers.
I am surprise that anybody else have this problem..because with a 18Vac at secondary you should have around 23/24VCC after rectifiers, that is to much for the NE5534 !!!!!
I find this conversation puzzling. Surely the voltage after the rectifiers is being applied to the voltage regulators, not the opamps.
You are using a regulated supply, I assume?
I think he's referring to the op amps in Carl's series regulator supply.
I think the op amps are powered rail to ground. NE5534 is rated for maximum 44V V+ to V-.
Doug this is for the opamps of Carl's regulated power supply for your preamp Sorry for the confusion..
The opamps voltage is the voltage after the rectifiers see attached..
Attachments
The opamp is used single ended supplied and can easily take up to 40V. No problem with 24V.
Jan
Note NE5534A's will need 22pF or so between pins 5 and 8 to be stable. I would suggest also adding 22pF between pins 2 and 6 to ensure stable feedback. And of course the standard 100nF ceramic decoupling capacitor between pins 4 and 7.
I suspect that circuit was not designed with the NE5534A in mind at all!
I suspect that circuit was not designed with the NE5534A in mind at all!
You wonder why people use such sub-optimal circuits with superreg boards available in the diyaudio store ...
Jan
So I have one of these NE5534 boards ready to be built up. I think the attraction is that it's all inclusive with the transformer, etc. and presumably a good fit for the project. But if the circuit is not optimal for this application I would happily use it elsewhere where it might matter less. Is the super-reg superior here, or just add the indicated caps under the NE5534 board?
BK
BK
Ah, light dawns. Thanks for the info.
My policy is never to operate 5534/2s above +/-17V for the sake of reliability.
However, as has been pointed out, the opamps in the PSU are working from rail to 0V, not rail-to-rail.
In my experience opamp-n-transistor PSUs can be very tricky to stabilise and I avoid them when possible.
Looking back, I never even mentioned the power supply in the original article. +/-17V from IC regulators was tacitly assumed.
All the development work was done using a bench PSU which must be some 30 years old now. No PSU issues at all.
Not to disrespect Carl's PSU, but the preamp does not need ultra-quiet supply rails. 78/79 series IC regulators should be fine.
I am assuming here the rail decoupling is done properly so that it does not feed rail noise into the signal ground.
Last edited:
Thank Doug, i am assuming too..
My origin problem is that the BD139/140 overheat (60ºC) with the load (200mA) and who is that is not normal.
I will try with an 12V-0-12V transformator, i am waiting for one 70052K from Talema. Whith 240V i should have 20Vcc after rectifiers.
bk856er: i will let you know after i changed the transformer..
Last edited: