Anyone ever toy with choke input PSUs in solid state circuits? I know they are often used in tube circuits (I use one in my tube preamp). But when redesigning my psu for my class-a house heaters I was wondering what the benefits of using a choke input psu would be. I was considering a LCLC filter. Would it be that much better than say a stardard pi filter with just CLC filtering?
I was planning on using 68000uF caps and didn't know what the ideal choke values would be, bigger is almost always better, but what values should I be looking at? BTW it's for an 8A load...
I know its much less efficient, but my transformer is more than capable of pumping out the current at the voltage required. Just wondering if there were any huge drawbacks.
Thanks again for any help...
I was planning on using 68000uF caps and didn't know what the ideal choke values would be, bigger is almost always better, but what values should I be looking at? BTW it's for an 8A load...
I know its much less efficient, but my transformer is more than capable of pumping out the current at the voltage required. Just wondering if there were any huge drawbacks.
Thanks again for any help...
There's a software tool at a site devited to vacuum tubes that might be able to help you choose the value of a power supply choke:
http://www.duncanamps.com/software.html
http://www.duncanamps.com/psud2/index.html
Since chokes that carry DC have to be designed not to saturate, make sure you take this into consideration when selecting the part, in addition to the inductance value.
-- mirlo
http://www.duncanamps.com/software.html
http://www.duncanamps.com/psud2/index.html
Since chokes that carry DC have to be designed not to saturate, make sure you take this into consideration when selecting the part, in addition to the inductance value.
-- mirlo
all new musical fidelity stuff uses choke regulated supplies, and the rep told me that is their hot new technology this year. if i could find a way to add choke regulation, that would be sweet 🙂
Well Peter, I seem to recall you buying a case of those BG Micro 68000uF caps, and those are the caps I was planning on using, so maybe you could help me out here. In order to simulate the psu well in PSU Designer I'd need to know the "resistance" of the capacitors. Since you have them, maybe you could give me a rough idea of what their resistance would be...
JoeBob said:
I use a choke input PSU on an Aleph 4 Amp that runs beautiful.
Originally I had no Pi filter with 240K uf but that produced hum so I added some reistors between caps, that cured the problem but then decided to do a LCRC type of filter which I used for some time with very good results.
Later I decided to test only LC with the whole lot of capacitance at the end and the amp clicked in very nicely and no hum whatsoever, very clean and quiet.
What called my attention was the excellent votage regulation I now get at the PSU, very stable.
The only penalty I pay is a lower Rail voltage that falled from 50V to 31V but dindn't care much up to the moment since I have more than enough power for the speakers I use and I'm running the output stage at a lower current I guess since did not change resistors. Soundwise is very good though.
BTW the chokes are gapped home made, 15mH.
Attachments
if you go SMPS
with a low noise switcher chip (LT1533 slew controlled switcher) -- you should use something like a 100uH choke prior to the filter caps.
with a low noise switcher chip (LT1533 slew controlled switcher) -- you should use something like a 100uH choke prior to the filter caps.
Joe, when you say you steal toroids from computer PSUs do you mean for choked linear power suplies, or do you mean for switching PSUs? If you use them for linear suplies, don't they saturate from the DC curent? I never considered toroidal chokes for this aplication, maybe you could tell me how it worked for you?
As for apassgear, those look amazing. If you wouldn't mind me asking, how did you go about constructing them? I'd absolutely LOVE to build my own chokes, I know they wouldn't look as good as yours but I'd care only about functionality. One thing that I don't know is where to obtain a core and how best to wind it, also, where do you place tha "air gap"?
Thanks for all the input. I'm really thinking I'll go for it. I think I'll try an LCLC filter, but I'll try just an LC filter as well, seeing how apassgear got such good results from it...
As for apassgear, those look amazing. If you wouldn't mind me asking, how did you go about constructing them? I'd absolutely LOVE to build my own chokes, I know they wouldn't look as good as yours but I'd care only about functionality. One thing that I don't know is where to obtain a core and how best to wind it, also, where do you place tha "air gap"?
Thanks for all the input. I'm really thinking I'll go for it. I think I'll try an LCLC filter, but I'll try just an LC filter as well, seeing how apassgear got such good results from it...
JoeBob said:
I have posted some information and pics at "E/I Transformer Laminations; Why?" on Pass Forum that you may want to read.
As for lamination you may ask Carpenter for the source. I don't think you would want to buy from my sources in Mexico.
Once you get started is very easy and you get full control over what you want... Let me know if you decide to roll your own.
I use a choke-input supply on my line stage which is based on Nelson Pass's Bride of the Son of Zen. (BOSOZ)
It is nice and quiet as can be.
Using an LCLC would conceivably give you a steeper roll off for the noise.
If the parasitic resistance of your chokes isn't sufficient to damp a resonant peek, add a little series resistance to the mix.
A quick and dirty formula for picking an inductance that is high enough to act as a choke-input filter is:
L = V / I, where V is the desired voltage and I is the continuous draw from the filter in mA. L will then end up in henries.
(For the 36V rails of my preamp I used 1.5H chokes from Hammond.)
So long as your choke ends up >= L above the voltage will be limited to approximately the average value of the transformer secondary voltage.
It should make for a less peaky waveform, which is perhaps why I perceive it to be quieter. (I don't have a scope at home so I can't offer any direct measurements.)
(Check out older editions of the Radio Amateur's Handbook. The 1970 edition I have has a pretty good discussion of the choke-input supply vs. the cap-input supply; that's where I cribbed the L(crit.) formula seen above and elsewhere on these forums.)
Best,
Erik
It is nice and quiet as can be.
Using an LCLC would conceivably give you a steeper roll off for the noise.
If the parasitic resistance of your chokes isn't sufficient to damp a resonant peek, add a little series resistance to the mix.
A quick and dirty formula for picking an inductance that is high enough to act as a choke-input filter is:
L = V / I, where V is the desired voltage and I is the continuous draw from the filter in mA. L will then end up in henries.
(For the 36V rails of my preamp I used 1.5H chokes from Hammond.)
So long as your choke ends up >= L above the voltage will be limited to approximately the average value of the transformer secondary voltage.
It should make for a less peaky waveform, which is perhaps why I perceive it to be quieter. (I don't have a scope at home so I can't offer any direct measurements.)
(Check out older editions of the Radio Amateur's Handbook. The 1970 edition I have has a pretty good discussion of the choke-input supply vs. the cap-input supply; that's where I cribbed the L(crit.) formula seen above and elsewhere on these forums.)
Best,
Erik
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