How do i remove noise on homemade powersupply?

[tempus fugit]

Couldn't you just use an IC regulator like LM 317?

 

[James Sweet]

I recently build my first valve preamp but the powersupply i threw together
creates quite a bit of noise on the output. I needed a cheap regulated 66v
supply so i put 2 33v zenners across the Cap on one of those cheap
disposable camera boards (probably not the best choice) The setup works fine
except for the 10khz squeal, i've tried adding extra caps in parallel but
there is no noticable difference. There is less than 1ma being drawn from
the powersupply.

Any ideas?

Having 10KHz anywhere inside that amp will give you noise, this is why AC
mains powered supplies are normally used.

 

[Art]

Correct: you may want to use a scope and determine exactly where the
offending signal is being produced. Even if it means temporairly using a
different power supply to make absolutely sure it is not developed within
the existing item currently being implimented. Addition of L/C circuits may
suffice to degrade the level of the offendign signal. Also proper decoupling
and filtering within the amplifier design may be required.

 

[Sam Goldwasser]

Couldn't you just use an IC regulator like LM 317?

Let met get this straight. You're going to all the trouble of building
a preamp based on vacuum tubes (that many will question as a waste of
time anyhow!) but are trying to use a solid state power supply for it?

You'll never get rid of the 10 kHz as it's probably coupling in not
only via the DC line but possibly via the magnetic field of the transformer.

Build a proper power supply or if you insist, try locating it remotely
and see if that helps.

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[Jeff]

I recently build my first valve preamp but the powersupply i threw together
creates quite a bit of noise on the output. I needed a cheap regulated 66v
supply so i put 2 33v zenners across the Cap on one of those cheap
disposable camera boards (probably not the best choice) The setup works fine
except for the 10khz squeal, i've tried adding extra caps in parallel but
there is no noticable difference. There is less than 1ma being drawn from
the powersupply.

Any ideas?

No, not the best choice. You want a well filtered power supply.
Carefully chosen small capacitors to ground, larger
capacitors and a couple of inductors in line may
be able to get the switching noise out depending on
how it is induced. Ground paths may also present problems
Some kind of sheilding may also be required.
I like the fact you said "threw together" I got a laugh
from that.
You might get some better answers on sci elect design
or from one of the tube audio groups with some more info.
Jeff

 

[Don]

rec.audio.tubes

 

[Guest]

Are you saying that you have some sort of battery source derived switching
supply that switches at 10khz? If so, I think you will have to scratch that
and find a better supply - switching supply's are generally not too popular
in audio circuits though they are creeping up here & there. If you are bent
for the switching supply topology then I would recommend that you find a
circuit that oscillates at >80khz so that you can more easily filter
remnants of it out of the audio. does it have to be 66v? what kind of
tube(s) are you runnung?

 

[Creamed_emu]

I recently build my first valve preamp but the powersupply i threw together
creates quite a bit of noise on the output. I needed a cheap regulated 66v
supply so i put 2 33v zenners across the Cap on one of those cheap
disposable camera boards (probably not the best choice) The setup works fine
except for the 10khz squeal, i've tried adding extra caps in parallel but
there is no noticable difference. There is less than 1ma being drawn from
the powersupply.

Any ideas?

 

[Guest]

Theoretically the higher the freq = the easier to filter but I am no expert
on the design & application of switching supply's. I do know that you want
to keep it's switching freq well above the audio range. You should be able
to get a quiet supply from your Voltage tripler circuit though. Are you sure
the hum isn't a result of grounding issues or filament balance?

 

[Sam Goldwasser]

Put a larger filter capacitor on the tripler. If you're drawing very little
current, it should produce a clean supply.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the Feedback Form at repairfaq.org. Thanks.

 

[Creamed_emu]

Its using 2 6J6's, I tried a voltage trippler from 20vac but there was still
noise, only this time 50hz. Im driving the camera board with 5v through 5
1n4004 diodes, which works fine. If i was to get it oscillating at around
25 - 30khz it should be out of the audible range, im assuming there would be
lower harmonics but they would be easier to remove, wouldnt they? I dont
care what powersupply i use, as long as its relatively cheap.

The Amp that it is attached to has no volume control, so 1vpp on the input
gives a full output so even the slightest ripple becomes quite noticeable.

Thanks,
Ben