OpAmp as Low Noise filament power supply

[thebadtall]

Hello, recently i built a ne5532 headphone preamplifier, wich gave a very nice sound through very accurate headphones, even with common components.

What surprised me was the absence of hum,hiss,noise and stuff, wich are common in unregulated power supplies. It was like running from battery.
I supplied the preamp directly 12vdc unregulated.
If i run any other of my preamps from this power supply you should try hard to understand what you listen to !!!!

I was in a search last days for a really simple way to remove those parasites from the power rail of filament supply of a tube preamp. and when i woke up today i thought to use a single opamp to feed the tube filament, but didnt try it.

however, Imax of 5532 if 60ma, but 60ma at +-15v ? that means 60ma at 30v (1.8W)? If so it can run the tube filaments (1.4W)
tube filament is I 120mA @ 12v

Can I use in a couple of 5532 in parallel to get that current ? Is that a sollution ? What do you think ?
Thank you

 

[barry]

Why do you need an opamp? Why not just drive the filament from a DC supply?

 

[not-a-moderator]

Why do you need an opamp? Why not just drive the filament from a DC supply?

Surely you meant to say REGULATED DC supply?

Because the OP said:

.....I supplied the preamp directly 12vdc unregulated.....I was in a search last days for a really simple way to remove those parasites from the power rail of filament supply of a tube preamp.....

 

[thebadtall]

i have tried LM317 regulators with improved ripple rejection, and another regulator after the regulator, totally 4 regulators, in order to receive a pure 10.5v and it worked fine, but i wanted to try another way !

I Want to feed the filament from the output of opamp , because I experienced Zero noise from a noisy power supply.

this is my question

You may not know what is the μV noise in high fi audio system. Even not audiable with typical speakers, it becomes audioable in sonus faber speakers !, i try since long time to ABSOLUTELY eliminate any parasites in hifi sound

if i supply filament with unregulated dc, at around 10 watts audio output with no signal input, it will sound like drilling the wall

 

[FvM]

if i supply filament with unregulated dc, at around 10 watts audio output with no signal input, it will sound like drilling the wall

Sounds like you wanted to give a kind of gain specification here, but 10 watts audio output with no signal input is just nonsense. To give a reasonable gain specification, the nominal input voltage of the respective amplifier stage for 10 W output must be told.

Even a brief literature of NE5532 data datasheet should clarify that it's not suited as filament supply without an additional output stage, e.g. a power transistor. Furthermore an amplifier (e.g. OP) can only work as a buffer but doesn't involve a stable output voltage without a voltage regulator respectively voltage reference. Apparently there's an error in reasoning.

You can of course design different DC stabilizing methods, but in a short, LM317 regulation performance should be more than suffcient for a low noise tube amplifier filament supply. Tube amplifier noise is a different point.

 

[barry]

This thread is all over the place. First, the OP is talking about using an opamp as a headphone amp, and then wants a low noise filament supply from an opamp. If you want a stable, low noise filament supply, then just use a regulator and some filtering. An opamp does not make your voltage any more stable than its input: garbage in, garbage out.

The reason you " experienced Zero noise from a noisy power supply" with the opamp is because the input to your opamp was not noisy, and the power supply noise is diminished by the power supply rejection of the opamp.