I need some help to design a PSU for my future amp. I need 400V. At first everything seemed so easy. 400V / 1,41 = 283... so i figured 285V from the tranny would do the trick. But then i got the Duncan PSU-designer, and my whole (simple) world was FUBAR.
I've managed to design a very simple psu wich gives me 400,5V with 5-10mV ripple. Everything is just fine, until i change the sec. resistance of the transformer. The voltage goes berserk. Since my mains-xfmr hasn't been made yet i have NO idea what the winding-resistance will be, so how am i supposed to make a working design in theory with any kind of software or even pen and paper???
I just wan't a simple psu-design with a solid-state bridge-rectifier and a few caps and resistors. No chokes. I haven't built that much before but in my previous projects i have used pretty big lytic caps (80 000uF or so) but from what i've learned here, big caps aren't allways prefered.
When i searched this forum, all I came up with was choked psus. Does averyone build WITH chokes??
I've managed to design a very simple psu wich gives me 400,5V with 5-10mV ripple. Everything is just fine, until i change the sec. resistance of the transformer. The voltage goes berserk. Since my mains-xfmr hasn't been made yet i have NO idea what the winding-resistance will be, so how am i supposed to make a working design in theory with any kind of software or even pen and paper???
I just wan't a simple psu-design with a solid-state bridge-rectifier and a few caps and resistors. No chokes. I haven't built that much before but in my previous projects i have used pretty big lytic caps (80 000uF or so) but from what i've learned here, big caps aren't allways prefered.
When i searched this forum, all I came up with was choked psus. Does averyone build WITH chokes??
Hi Mikael,Mikael Abdellah said:
When you go into PSUD2, and edit the power trans' specification, there is a small box there marked [....]. Click on that and it will allow you to adjust in more detail. Set the voltage to about where you want it, then the current you need and the regulation. I normally use 10% for EI core transformers and 5% for torroids. It'll then calculate the secondary resistance for you.
The peak voltage = 1.414 x the RMS only ever applies in theory, with no load on the circuit, and *ideal* components, but transformers and wiring have resistances, diodes have voltage drops etc. About 1.2-1.3 is closer in reality.
I assume you're having your power trans made. When you ring for a quote, tell them the figure for regulation and max secondary resistance as well as the voltage and current of the secondaries. If you're buying a trans from a catalogue pre-made, email them for the regulation if in doubt, but the numbers I use are pretty close. Besides, there is no need for it to be exact. A couple of volts here and there isn't critical <i>provided</i> the voltage is stable and clean. My last design came out at 440V when I measured it instead or 450V, a 2% error. Who cares, when my mains voltage from the wall varies more than that?
If you give us the current requirements of your amp, and maybe a description of what it is, I'm sure someone will help you design something for your specific circuit.
Why no chokes? They make it a heck of a lot easier to get a clean supply, especially if you're not using some form of regulation.
{I can't wait to see who jumps on that one.}
All an amplifier does is modulate the power supply. If your PSU is no good, you stand little chance of having a good amplifier. Or put another way, the better your PSU, the better your amplifier can be.
Tube amps generally use smaller caps, esp in conjunction with chokes. The amount of energy stored in a cap is 1/2 x C x V^2
I do, always. I prefer LC if I'm using a shunt reg, and LCLC when I'm not, and LCLC->shuntreg for phono and mic preamp stages.
first of all.. thank you for you replies...
the amp for the psu is a SE KT88-amp which I have designed from svetlana's specs for the 6n1p and a couple of SE 6550-amps i've found on the net.
http://213.67.45.70/se_kt88.gif
The reason i don't wan't a choke is that i can't afford it and i have'nt got enough room. The amp is allready beginning to be quite big.. physically... At least in my computer-model of it
I will have all trannys made by sowter, but i have allready asked brian 100000 stupid questions, so i don't wan't to bother him anymore.
the amp for the psu is a SE KT88-amp which I have designed from svetlana's specs for the 6n1p and a couple of SE 6550-amps i've found on the net.
http://213.67.45.70/se_kt88.gif
The reason i don't wan't a choke is that i can't afford it and i have'nt got enough room. The amp is allready beginning to be quite big.. physically... At least in my computer-model of it
I will have all trannys made by sowter, but i have allready asked brian 100000 stupid questions, so i don't wan't to bother him anymore.
hmm... chokes i think.... i'm not very good at this yet...
I connected a 47uF cap directly to the rectifier, then i put one 20H choke and after that a HUGE cap (2200uF). It gave me incredible results on paper (screen) but I wonder how it would perform in real life. The only problem is that i see the cost for my amp shooting trough the roof.. but what the heck.. you only live once, right?
I connected a 47uF cap directly to the rectifier, then i put one 20H choke and after that a HUGE cap (2200uF). It gave me incredible results on paper (screen) but I wonder how it would perform in real life. The only problem is that i see the cost for my amp shooting trough the roof.. but what the heck.. you only live once, right?
Basically you have a psu that would be similar to what would drive a 300b imho..you might want a little more juice.. looking at quite a few 300b or el34 designs leads you to a transformer of around 400v! Don't forget your output transformers drops 30-40v of the b+ as well before you get the plate voltage.
The tranformer being from sowter you can specify several taps! Is that not a grand idea ;-).. Get taps at 300, 350, 400, 450 won't be that much more work for the tranniebuilders...they just have to pause add a tap and continue winding...(450 might actually be to much)
If you are going to use one transformer which would be the best value for money seeing that money is tight and you might want chokes..get one nice fat tranny for both channels that can supply say 400/500mA. Use one big choke and so you have clc for both channels then split into rc for each channel.
Hope this helps..
The tranformer being from sowter you can specify several taps! Is that not a grand idea ;-).. Get taps at 300, 350, 400, 450 won't be that much more work for the tranniebuilders...they just have to pause add a tap and continue winding...(450 might actually be to much)
If you are going to use one transformer which would be the best value for money seeing that money is tight and you might want chokes..get one nice fat tranny for both channels that can supply say 400/500mA. Use one big choke and so you have clc for both channels then split into rc for each channel.
Hope this helps..
Space is at a premium?
Mount the choke underneath the chassis directly under the power transformer. Make sure you get one with "Frame" construction, then you can mount it with it's field at 90 degrees with respect to the mains transformer AND to the output transformer(s).
Cost:
You've already explained why you want to use Sowter for your mains and output transformers. But the choke could be obtained cheaper locally. When mounted underneath, appearance is less important.
Cheers,
Mount the choke underneath the chassis directly under the power transformer. Make sure you get one with "Frame" construction, then you can mount it with it's field at 90 degrees with respect to the mains transformer AND to the output transformer(s).
Cost:
You've already explained why you want to use Sowter for your mains and output transformers. But the choke could be obtained cheaper locally. When mounted underneath, appearance is less important.
Cheers,
sorry
Choke and inductor are just different terminology for the same thing then, when refer to it in a speaker crossover it is called coil, when refer to it in a Pi filter it is called inductor, when it is on its own it is called choke, when it is connect to the mains it is call transformer, when connects to a speaker it is call output choke?
Am I correct with these assumptions?
Thanks
Chris
Choke and inductor are just different terminology for the same thing then, when refer to it in a speaker crossover it is called coil, when refer to it in a Pi filter it is called inductor, when it is on its own it is called choke, when it is connect to the mains it is call transformer, when connects to a speaker it is call output choke?
Am I correct with these assumptions?
Thanks
Chris
CHOKING
Hi,
Well I think the name "choke" referes to the function (service) it was used for namely, as Jan stated to choke/strangle ripple from the PSU.
Although it has nice side effects such as isolating the PSU from its' circuit as well providing an almost infinite impedance.
It also tends to regulate the PSU.
When I hear" inductor" I automatically think about x-over designs for LS use (air-core inductors).
Terminology can be confusing,
Hi,
Well I think the name "choke" referes to the function (service) it was used for namely, as Jan stated to choke/strangle ripple from the PSU.
Although it has nice side effects such as isolating the PSU from its' circuit as well providing an almost infinite impedance.
It also tends to regulate the PSU.
When I hear" inductor" I automatically think about x-over designs for LS use (air-core inductors).
Terminology can be confusing,
I would like to thank everyone that answered to my question! You guys are great. 
Right now I'm checking my finances to see if there is room for a choked PSU, and I must say... It looks promising. I think i will go for a mains transformer with two sec. for B+ (one winding for each channel). So I will probably get two 20H 150mA chokes from sowter. I think the amp will draw 110-120mA per channel so 150mA should be enough.
Ohh... btw... Does anyone have any bias-suggestions for the KT88? When I studied the spec-sheets from svetlana they seem to recommend 105mA, thats why i thought 120mA would be enough for the whole circuit.
Bas... the reason I placed a 10W plate-resistor on the 6n1p is simple. The place I order all my components from (Elfa) only had 47k at 10W. Is it bad to have 10W instead of 1W?
Right now I'm checking my finances to see if there is room for a choked PSU, and I must say... It looks promising. I think i will go for a mains transformer with two sec. for B+ (one winding for each channel). So I will probably get two 20H 150mA chokes from sowter. I think the amp will draw 110-120mA per channel so 150mA should be enough.
Ohh... btw... Does anyone have any bias-suggestions for the KT88? When I studied the spec-sheets from svetlana they seem to recommend 105mA, thats why i thought 120mA would be enough for the whole circuit.
Bas... the reason I placed a 10W plate-resistor on the 6n1p is simple. The place I order all my components from (Elfa) only had 47k at 10W. Is it bad to have 10W instead of 1W?
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