I've built 8 channels of this classic circuit, it was modified by a friend and me for linear gain control and RF rejection. The first stage gain is 10 and the diff. amp stage max. gain is 100 so the total gain of the circuit is 1000 or 60 dB.
Im looking for the lowest possible noise (without adding a parallel transistor input stage) and the best possible performance out of one of those chips. Currently it is working with NE5532.
I know there are better op amps, but they are not available here, so these are my only 2 options:
LM833 or NE5532...
Based on data sheet info LM833 has 4.5 nV/sqrt(Hz) of input noise VS 5 nV/sqrt(Hz) of NE5532 (NE5534 is quieter but I need a dual chip). So LM833 is quieter.
What do you think?
Thanks in advance.
- Marc Fricke Baptiste
Im looking for the lowest possible noise (without adding a parallel transistor input stage) and the best possible performance out of one of those chips. Currently it is working with NE5532.
I know there are better op amps, but they are not available here, so these are my only 2 options:
LM833 or NE5532...
Based on data sheet info LM833 has 4.5 nV/sqrt(Hz) of input noise VS 5 nV/sqrt(Hz) of NE5532 (NE5534 is quieter but I need a dual chip). So LM833 is quieter.
What do you think?
Thanks in advance.
- Marc Fricke Baptiste
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I agree absolutely with richie00boy in what writes. The same i have ascertained also me in professional mixing desks. One chip that i have seen until now which replaces the NE5532 or the NE5534 it is from the newer versions SSM2015 or SSM2220 of Analog Devices. The reason for the NE5532 of course is that which very rightly reports jurgenk.
Regards
Fotios
Regards
Fotios
NE5532 or LM833
Hi Fotios
I bow to your experience in this matter. I was just wondering about the effects of much lower residual distortion in the overall scheme of things. SSM2220 front end is certainly the way to go. They are very low noise duals.I have used them in preamps.
Even better if you parallel a few devices.
You haven't been posting much recently ?
Regards
SandyK
Hi Fotios
I bow to your experience in this matter. I was just wondering about the effects of much lower residual distortion in the overall scheme of things. SSM2220 front end is certainly the way to go. They are very low noise duals.I have used them in preamps.
Even better if you parallel a few devices.
You haven't been posting much recently ?
Regards
SandyK
Thanks to all for your kind replies.
As I wrote Im currently using NE5532's but Im having stability problems and intermitent operation. I dont know why it happens but when the circuit works ok it is dead quiet.
Probably because the original circuit was designed for a PNP bipolar input op amp like the lm833, yesterday I was testing the circuit with some old NJM4560's (Made by JRC I think) which have PNP inputs too and I noticed that the circuit was stable and not randomly working but working every time I energized it. Obviously it was a bit more noisy at max gain but it behaved well.
What do you think is happening?
As I wrote Im currently using NE5532's but Im having stability problems and intermitent operation. I dont know why it happens but when the circuit works ok it is dead quiet.
Probably because the original circuit was designed for a PNP bipolar input op amp like the lm833, yesterday I was testing the circuit with some old NJM4560's (Made by JRC I think) which have PNP inputs too and I noticed that the circuit was stable and not randomly working but working every time I energized it. Obviously it was a bit more noisy at max gain but it behaved well.
What do you think is happening?
Thanks Richie00boy that is certainly a possibility, I'll have to check each channel extensively...
There is another issue, since there are 8 channels having 16 dual op amps drawing current permanently, do you guys think it may need an special power supply? (highly regulated, with lots of capacitors and all that stuff) I want to keep the noise floor down as possible and IC regulators are really noisy, what is the most quiet solution if I will be using all those channels at the same time?
I built the micpre using a PCB to mount all the components, except for the PSU. I have been testing channels individually with a pair of 9 volt batteries and an expensive lab power supply unit (which is too heavy and bulky to fit inside the chassis
).
Each channel has its own power supply bypass caps and op amps are not shared between channels.
There is another issue, since there are 8 channels having 16 dual op amps drawing current permanently, do you guys think it may need an special power supply? (highly regulated, with lots of capacitors and all that stuff) I want to keep the noise floor down as possible and IC regulators are really noisy, what is the most quiet solution if I will be using all those channels at the same time?
I built the micpre using a PCB to mount all the components, except for the PSU. I have been testing channels individually with a pair of 9 volt batteries and an expensive lab power supply unit (which is too heavy and bulky to fit inside the chassis
).Each channel has its own power supply bypass caps and op amps are not shared between channels.
No, almost all channels work perfect with batteries and with the lab PSU, while others have some kind of low frequency noise (even when energized with batteries).
When I connect an unregulated power supply (cap-resistor-cap) to energize ANY channel a LOUD low frequency hum is heard sometimes the mic's signal is heard barely and sometimes just this hum.
Yes it has got a lot of meters including those you mentioned, I dont know why but if I energize V- first, the current limiter switches on, this doesnt happen when I energize V+ first.
I've set the current limiter at 200 mA. since Im just energizing 2 dual op amp IC's at a time, 100 mA is the lowest setting for this nice piece of equipment.
I'm not very experienced designing pro power supplies and I dont know if this application needs it.
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