choke input power supply filter

[MRupp]

I am using a choke input power supply for my ZEN V4 (outboard, with IXYS diodes and RC snubbers a la Hagerman) and my horn speakers have 104dB sensitivity. However, the amp is absolutely dead quiet, no hum, no buzz, no nothing. So maybe your problem is somewhere else?

Note that switching noise can also create RFI and can couple directly into your amplifier circuits. You should try and move the power supply away from the actual circuit, and also minimise the loop sizes in your PS.

Lastly, especially if you intend to optimise the power factor, you should increase the input choke to beyond the critical value, e.g. by swapping the 3mH and 120mH inductors. If L is below this value it is strictly speaking a capacitor input supply. My 5 cents ......

[planet10]

Originally posted by Kashmire
I've used a dozen different diode types, and they all do this.

Did this include trying any Schottky diodes?

dave

[mzzj]

Originally posted by planet10


Did this include trying any Schottky diodes?

dave

I was going to ask the same thing, as Schottky's should be free of reverse recovery problems.

[firestorm]

Hi Audionut,
did you manage to sort out your psu ?
what was the outcome ?

I'm asking because I'm considering trying the same thing.

Regards
fs

[audionut]

Hi Firestorm....

This thread is a bit old...so I reviewed it...

I gather that 2.5mh of inductance is not enough to reach critical inductance with the amount of current being drawn...

but the Aleph 30 Amps have been working...sound very sweet...remember, that I had some large Signal Transformers that were almost free. Their voltage was too high...so I was looking for a way to get to 25 volt rails. Choke input seemed to be a way to cut down the voltage, and seemed to have some other advantages.

So choke input worked for me...

[andyjevans]

I'm just reviving this thread yet again - no doubt it's always of interest. I have some chokes which are 280mH and 2.7A. Could be used singly or in parallel. I've used them for DC filaments for DHT tubes like 300b, but not for a solid state amp. What do I have to worry about with turn-on spikes with larger value chokes like this? Can somebody explain how pure choke input, choke input with small cap in front (like 220uF) etc. works with regard to spikes? I have a multimeter but not a scope, and I don't know if a spike would show on a multimeter.

I note the original Nemesis used a similar size choke. One version has 150mH at 2.5a and another 200mH.

andy

[AndrewT]

Could you point to the choke input PSU?
or modify the schematic to show what you are referring to?

I can see a CLC providing the +39V supply.

[pieter t]

I don't think that Andy suggested the above circuit to have a choke input power supply.
Omitting the 33mF/40V before the choke would make the power supply choke input (clear enough) and drop the final DC supply to about 25 V with the same power supply transformer.
Enough to be found on behavior of choke input supplies with regard to current spikes IMO.

[andyjevans]

Yes - Pieter is right here, I'm basically asking what to do with the 280mh chokes I have. Whether I can use them for pure choke input, or with a small cap or with a large cap depending on what the behaviour is regarding spikes. A friend of mine uses chokes in his power supply for a JLH amp and his opinion what that 280mH is unusable because of the spikes it would cause, so I was including the Nemesis to show a similar size choke being used. In this case the input cap is 33,000uf as stated, so does that mean a smaller cap or pure choke input was rejected as unsuitable?

Andy

[MRupp]

I am using 300 mH (nominal value) chokes in a PS with 2A load and I do not get any turn on spikes at all, or turn-off spikes for that matter, even if there where spikes the heavy load would dampen them.

220uF in front of the choke is not such a good idea I would say. It somewhat defeats the purpose of the choke, can cause ringing and may not be able to manage the ripple current. Try to simulate your PS in PSU designer, I found that it is pretty accurate and should even show you the start-up behaviour.