To choke or not to choke

Hello all! After constant enthusing from MO I have decided to join this forum to see what the fuss is all about. MO - in case you hadn't guessed this is Stumblinthrulife, unfortunately I can't use that name on here due to character number limitations.

Anyway, to business. I'm thinking of having a crack at building a mains filter (don't panic - I did a couple of years of electronics at uni, I'm not gonna fry myself). Now the question is 'to choke or not to choke'?

A lot of manufacturers seem to hate chokes and not use them, claiming increased impedance on the mains. Looking from a purely technical stand point though, this is hookum. At 50 Hz the impedance of a choke is minimal, this being the whole point of a choke.

So, anyone got any experience with chokes? Has anyone heard the decrease in dynamics that is claimed by the likes of RA? I really want 'heard it with my own ears' advice, rather than the 'quoted from a website' advice that I have seen elsewhere.

 

A simple listen to any M/F 308/ Nu-vista product will confirm this
Why not construct 2 versions one with a choke the other without, should prove to yourself where it works or not.
I personaly find anything other than totaly passive, removes the dynamics wholeheartly, even mains reconstruction equipment, can have this effect, and at a costly power loss usualy 2:1.
Some audio equipment seems to 'harness' the common mode drive, to 'add' to its charactor, where as M/F decided to remove a lot if not all, by using dual chokes, this may given a big clean, open, smooth sound, but totaly devoid of any life, try removing the DCR from a 308 P/A, almost becauses good.
I think a lot of producers also feel after trying CRPS, it compromises the sound they are looking for, and then maybe cite impedence mismatches as validation for non use (cost/space are other more realistic reasons)
Of all of the mains FILTERS I've tried passive ones have worked the best, but you now have an oppontunity to build your self a pair of indentical filters, less a choke in one.
Good Luck Wm

 

And then again, Border Patrol sell a replacement choke filtered PSU for Valve amps and it is fantastic.

 

Would that be for a valve amp then Lee

 

Hi


The Border Patrol supply is a Choke input supply while most you will come across (like the ones in those MF amps) are capacitor input supplies.

Choke input is when the choke (series inductor) follows the rectifier. This is followed by a capacitor.

The choke input offers better regulation & lower peak ripple currents. Higher DC currents can be drawn from the transformer & rectifier. This input choke offers a high input impedance to ripple currents.

These can be ideal as they can be used in circuits which draw varying current & require a stiff power supply.

There are disadvantages such as they need a critical value of current to be drawn or the output voltage can rise sharply. To help combat this a bleeder resistor can be used. But bleeder resistors can consume power & reduce the power supplies current capabilities.

By using a big inductance high quality choke will help increase the size of the bleeder resistor lowering the wasted current.

Also there can be problems with choke capacitor resonance which is cut down be design.

You don't see these very often due to the cost of quality chokes, careful design needed & also the size of these supplies.

When done right, they are very good. It would be interesting to try these on some solid state gear.


SCIDB

 

Hello Mr Stumblin'

Good to see you round these parts, and I hope you get the answers you're after.

WM, I see, someone mentions my name and thus it's required to put MF down to make your point What effects would chokes have on the blue LEDs?

 

Hmmm, blue LEDs - nice idea. Would match my Silverline kit nicely.

 

Hmmm, blue LEDs - nice idea. Would match my Silverline kit nicely.

 

Ooops - that'll teach me not to use the back button on my browser. Sorry!