I'm flattered to see my early sketch for the 'flea' referenced here... it can be easily improved...
But actually - for what the OP wants - there was an excellent post a decade or more ago: read this thread, and see JohnW's post #23: all you need, simple cheap, and very effective: brute-force filter a regulator, tap teh voltage you need, and buffer that:
Capacitor type for Vref
But actually - for what the OP wants - there was an excellent post a decade or more ago: read this thread, and see JohnW's post #23: all you need, simple cheap, and very effective: brute-force filter a regulator, tap teh voltage you need, and buffer that:
Capacitor type for Vref
I'm not sure but all the noise which exists on OPA+ will be "visible" transparently on OPA out. (and also the Power supply noise is transferred via PSRR).
The useful idea is definitely to put the OPA2 - as close to the IC VREF pin as possible.
(Maybe I missunderstand, so please correct me
)meanwhile I did a modelling. Somehow I can't manage it with LTSpice just in Tina.
Not exactly the same components are found, but I tried to add similarly low noise ones LME47910 (2,5nV versus 0,8)
The capacitor on the LEDs does a nice job
Also on the output (but anyway it is needed)
picture 1: 1uF on LEDs
picture 2: 10uF on LEDs
picture 3: 100uF on output
Not exactly the same components are found, but I tried to add similarly low noise ones LME47910 (2,5nV versus 0,8)
The capacitor on the LEDs does a nice job
Also on the output (but anyway it is needed)
picture 1: 1uF on LEDs
picture 2: 10uF on LEDs
picture 3: 100uF on output
Attachments
Presumably, that is the schematic posted below, which is very similar to the ESS recommended circuit, only they require using an AD797 or LME49720 type opamp, no 5532's.
For the lower current ESS DACs that opamp type supply is probably ideal, and ESS even says so in rather firm language.
However, some of the newer ESS ES9028PRO and ES9038PRO DACs pull more AVCC current than one opamp can supply (per left/right channel). So the need is to up the output current while maintaining the quality of regulation.
Attachments
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babolcs,
If you concern about AD797's stability, you may consider ADA4898-1. It's quite stable at unity gain. I use it on my op-based regulator with good result.
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Yes.
Add a small emitter-follower (with, say 1Kohm to 0v) inside the opamp loop and unload the opamp
ZTX450 or similar is plenty, at low raw supply voltages.
Thanks for that Gerhard, I've been using these for a few applications.
Looking at the data sheet they are happier with 0 ohms than 100 in the FB
at gain +1. Looks like a small cap across FB for some applications might be in
order.
T
Meanwhile I finalized a built on the way I can power the 9038 (doubled OPA2) As I measured it eats roughly 5mA on each channels. I had at home 5532 and 5534 - I know it is not so ideal so demfinitely not final solution.
If I tried to decrease the output R to 0 then the output voltage dropped down. 2v. So I applied the originally used 4,7ohm.
With DC measure it seems ok.
But there must be some stability problem. The voice is not that clear. No audible noise or brumm, nothing like that. Even the stage seems to be ok. Just something is not that clear.
Yes possibly a transistor would be needed to OPA1 as Martin and Jens suggested to be able to deliver more current.
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What is not clear, the DAC sound quality?
If you meant a particular DAC sound quality, was it more clear with another power supply circuit? If not, maybe the clarity issue is not caused by a power supply problem?
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Yes, it can do much better, wideband; and it gives you complete control of how it reacts into your prospective load.
The post a few above calling the NE5534 'noisy' made me giggle! You have to have things really wrong (layout, supply bypassing, surce impedances) to make a 5532 'noisy'. Feed it with a low source impedance and it's about as noisy as, what, a 500ohm resistor, if that. I can't readily think of a situation where it would be the prime noise-source in a circuit.
(and if you can't readily push the limits of a NE553x, you are not likely to benefit from an AD797... nor keep such a thing happy in-circuit)
The post a few above calling the NE5534 'noisy' made me giggle! You have to have things really wrong (layout, supply bypassing, surce impedances) to make a 5532 'noisy'. Feed it with a low source impedance and it's about as noisy as, what, a 500ohm resistor, if that. I can't readily think of a situation where it would be the prime noise-source in a circuit.
(and if you can't readily push the limits of a NE553x, you are not likely to benefit from an AD797... nor keep such a thing happy in-circuit)
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