Bricolo said:
If Vcc=12V
Vds=1.27V
V4 (voltage on R4) must be 12-1.27=10.73V
I through R4 is 200mA
->R4=10.73/0.2=54R
Is this correct? (have I understood everything correctly?)
B]
This is absolutely correct!
And that is the only thing you need to do (or worry about)
to get 200mA operation.
If you take 56 ohm resistor, will be a few % less than 200mA
If you take 47 ohm will be some % more.
But that doesn't matter, if it is exactly 0.200 A
Watt specification for resistor:
10.8 Volt x 0.200 Ampere = more than 2.16 Watt
Take 5 Watt resistor (better to use double as high Watt Resistors)
To get 50 ohm, you can use two 100 Ohm resistors, in parallell
then each resistor takes 0.100 Ampere, so they can be 2 Watt resistors
2x 2 Watt= 4 watt, so they can take more than 2.16 Watt
Another fun thing about Headphones Amps, is to put one 16 ohm Loudpeaker. (Or you could use two 8 ohms loudpeakers, in Series)
You then can listen on lower volumes to your Amp.
The Amplifier doesn't really know, that he is a Headphone amp.
He will drive even Loudspeakers.
So silly he is!
halojoy said:
NO! I just realized I made a mistake
I said, "l'et's put Id=200mA"
so Vgs=3V, and Vds=1.27V
This is correct (excepting that Vgs>Vds looks strange to me)
the mistake I made, is to say thar Vgs=3V so G must be at a potential of 3V
The correct thing is: G must be at a potential 3 volts higher than G's potential
so Vg=3+R4*I4
->Vg=3+R4*0.2
with Vcc=12V
Vcc=Vgs+R4*0.2
R4*0.2=12-1.27=10.73V
So R4 must be 53.65R
that matcher with my last post
but my error was to say Vg=3V
but it is 3+0.2*53.65
->Vg=13.73V
IMPOSSIBLE with Vcc=12V
what's the problem?
Hi all
I've built my szekeres now, sounds good
the psu isn't finished yet, I'm using a 12V car battery
I'll go for a regulated (lm317) power supply
will a single lm317 (1.5A max) be enough to drive both channels? (they are biased to 250mA, so the whole thing draws 0.5A at iddle)
or have I to go with one psu per channel?
I've built my szekeres now, sounds good
the psu isn't finished yet, I'm using a 12V car battery
I'll go for a regulated (lm317) power supply
will a single lm317 (1.5A max) be enough to drive both channels? (they are biased to 250mA, so the whole thing draws 0.5A at iddle)
or have I to go with one psu per channel?
Best is - for stereo music
Best is for stereo,
to use two LM317. Will not cost much.
Good if trafo is 12V 1A = 12VA
or 2x12 2x0.5 for double secondary windings.
This can then be used with 2 separate rectifying bridges
for two LM317.
I assume yo use single ended supply, 12 V regulated.
and the MOSFET's Source at 6 volt
Best is for stereo,
to use two LM317. Will not cost much.
Good if trafo is 12V 1A = 12VA
or 2x12 2x0.5 for double secondary windings.
This can then be used with 2 separate rectifying bridges
for two LM317.
I assume yo use single ended supply, 12 V regulated.
and the MOSFET's Source at 6 volt
I already have a 50Va transformer, single secondary
it is 12V rms, i've mesured 13.36V with no load
at 12V rms, it should output 17V dc after a rectifier bridge and some caps, and something I'll set between 12 and 15 after the lm317
The second 317 will not cost much, as you said. But the caps will
So I was wondering if it's really worth it
it is 12V rms, i've mesured 13.36V with no load
at 12V rms, it should output 17V dc after a rectifier bridge and some caps, and something I'll set between 12 and 15 after the lm317
The second 317 will not cost much, as you said. But the caps will
So I was wondering if it's really worth it
Perfect trafo
Perfect trafo!
Use one bridge. Big cap(s) after that.
Two separate wires to two LM317.
One smaller Elyt cap and one little polyester cap
at input of each LM317.
Do not put LM317 too far from the MOSFET.
And trafo not too near to amplifier's Input.
As you already have said, the voltage drop
of the big trafo output might be rather low
giving even 20 VDC after rectifier.
(remember that this can be 19, if 230VAC goes down to 210VAC, some days)
This would allow more than 12.0 volt
maybe even 15.0 volt, at output of LM317.
LM317 need something like 3-4 volts to operate well.
Always design for worst case.
A mains 230(220) drop of 5%
is some 5% drop over the rectifiying bridge.
Perfect trafo!
Use one bridge. Big cap(s) after that.
Two separate wires to two LM317.
One smaller Elyt cap and one little polyester cap
at input of each LM317.
Do not put LM317 too far from the MOSFET.
And trafo not too near to amplifier's Input.
As you already have said, the voltage drop
of the big trafo output might be rather low
giving even 20 VDC after rectifier.
(remember that this can be 19, if 230VAC goes down to 210VAC, some days)
This would allow more than 12.0 volt
maybe even 15.0 volt, at output of LM317.
LM317 need something like 3-4 volts to operate well.
Always design for worst case.
A mains 230(220) drop of 5%
is some 5% drop over the rectifiying bridge.
Bricolo said:
I would rather buy another LM317 and some small elyt caps for it,
than buy a LM350.
As the power (volt x ampere) is so low over LM317
there is no need for LM350.
And if you can buy another LM350,
I do not understand why you can not use two LM317.
It can not be a money issue, I imagine.
I would buy ten(10) LM317.
And some LM337, for negative voltages.
They are useful in so many ways.
Circuits will always need power supplies.
Need help with PSU design
Hello,
I did not want to pollute the forum with another thread for this old buffer design. But, I need help with your opinion and part selection. I have searched the forum but many design pictures are not available anymore and information within description without schematic does not help me. I have already built classic Szekeres buffer. Going through found search results some users opt for non-regulated PSU when majority suggests regulated one including Rod Elliot's Death of Zen Capacitance multiplier. I would like to build one but I have a problem to re-design it for my transformer. I have r-core 38VA transformer (19V / 2A). I would like to scale down PSU output voltage to 15V. I do not know how to calculate resistor values to obtain 15V output. I also have question about non-regulated PSU schematic on the same ESP page. I have two r-core transformers. Are my transformer power is enough to try to use non-regulated PSU? I think about using two separate PSUs for each channel.
I am sorry to bringing back this thread, but I could not find direct answers for my questions.
This is link to DOZ amplifier:
Death of Zen - A new Class-A power amp
Hello,
I did not want to pollute the forum with another thread for this old buffer design. But, I need help with your opinion and part selection. I have searched the forum but many design pictures are not available anymore and information within description without schematic does not help me. I have already built classic Szekeres buffer. Going through found search results some users opt for non-regulated PSU when majority suggests regulated one including Rod Elliot's Death of Zen Capacitance multiplier. I would like to build one but I have a problem to re-design it for my transformer. I have r-core 38VA transformer (19V / 2A). I would like to scale down PSU output voltage to 15V. I do not know how to calculate resistor values to obtain 15V output. I also have question about non-regulated PSU schematic on the same ESP page. I have two r-core transformers. Are my transformer power is enough to try to use non-regulated PSU? I think about using two separate PSUs for each channel.
I am sorry to bringing back this thread, but I could not find direct answers for my questions.
This is link to DOZ amplifier:
Death of Zen - A new Class-A power amp
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