Dear All.
I'm working around the power supply of a tube preamp i build.
I started using one transformer i had un my hands,with a 0-125 secondary...so everything was calculated considering it.
The PSU had a CLCLC filter.
So far i realized that the transformer was undersized...after some hours became very hot.
So i'm using now a 185 0 185 transformer.
To avoid to change the working point of the tubes i was obliged to add an RC cell.
What's the best configuration in your opinion?
CRC L C L C..
Or..
CLC RC LC
Many thanks in advance.
Maurizio
I'm working around the power supply of a tube preamp i build.
I started using one transformer i had un my hands,with a 0-125 secondary...so everything was calculated considering it.
The PSU had a CLCLC filter.
So far i realized that the transformer was undersized...after some hours became very hot.
So i'm using now a 185 0 185 transformer.
To avoid to change the working point of the tubes i was obliged to add an RC cell.
What's the best configuration in your opinion?
CRC L C L C..
Or..
CLC RC LC
Many thanks in advance.
Maurizio
I would recommend using the 180-0-180 transformer with 6X5 rectifier tube. Then go through the CLC PI filter. Feed it to Resistor/0D3 voltage regulator tube. A small 0.1uF capacitor can be used at the output.
The 0D3 requires minimum of 5mA to operate.
Hope you like it.
Johnny
The 0D3 requires minimum of 5mA to operate.
Hope you like it.
Johnny
Hi Johnny.
I would prefer to use the silicon diodes as i'm already doing.
I do not have any 6x5 and OD3 at the moment.
In this case..which combination wuold you recommend?
Start with the RC filter just at the beginning...or with the CLC ?
Thanks
I would prefer to use the silicon diodes as i'm already doing.
I do not have any 6x5 and OD3 at the moment.
In this case..which combination wuold you recommend?
Start with the RC filter just at the beginning...or with the CLC ?
Thanks
Hi. yes i know PSUD .
I was just wondering if in terms of results helps to have first the inductance..or the resistor..
Thanks
I was just wondering if in terms of results helps to have first the inductance..or the resistor..
Thanks
If you know the most important parameters of PT and choke, the simulation is easy.
It's LTSpice, but PSUD also good.
sample:
If you want lower hum than 12mVpp, another R-C stage can be used.
It's LTSpice, but PSUD also good.
sample:
If you want lower hum than 12mVpp, another R-C stage can be used.
You could use a zener diode string instead of the 0D3. Bypass the zener string with 4.7uF (or so) film cap. Make sure the zener string draws at least 5mA of current in operation. Each individual zener should be rated to take the entire load current (just in case).
For B+ of about 165V DC, you could use twenty-seven 6.2V zeners in series, or eleven 15V zeners, or nineteen 9V zeners. Higher voltage zeners will need to be rated for more watts, while lower voltage zeners should be quieter and won't need as high a power rating, but you'll need to use more of them to get to your target voltage.
15V * 0.035A = 0.525 watts (use at least 2W rated parts)
9V * 0.035A = 0.315 watts (at least 1W rated)
6.2V * 0.035A = 0.217 watts (at least 0.5W rated)
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....So starting with a 350VCT power transformer you could:
1) Use your choice of tube or silicon rectification,
2) Then CLC, or CRC if you prefer, then
3) RC after that, or DN2540 CCS to 165VDC zener string
For 2) above, CLC would give you lower ripple but the choke will cause a subsonic resonance (they always do), while CRC would not filter out as much ripple but there would be no subsonic resonance.
The thing is, if you use the CCS+zener string stabilizer, that will scrub away practically all the ripple, so it won't matter much whether you use CLC or CRC.
1) Use your choice of tube or silicon rectification,
2) Then CLC, or CRC if you prefer, then
3) RC after that, or DN2540 CCS to 165VDC zener string
For 2) above, CLC would give you lower ripple but the choke will cause a subsonic resonance (they always do), while CRC would not filter out as much ripple but there would be no subsonic resonance.
The thing is, if you use the CCS+zener string stabilizer, that will scrub away practically all the ripple, so it won't matter much whether you use CLC or CRC.
Hi Guys.
I'm sure i'm placing a stupd question.
Because i need anyhow an RC cell to recuce the voltage..make sense to start with an a CLC filter first..or the CRC..which is the best combination in your opinion?
About CCS is very interesting..i would like to test it..
I'm sure i'm placing a stupd question.
Because i need anyhow an RC cell to recuce the voltage..make sense to start with an a CLC filter first..or the CRC..which is the best combination in your opinion?
About CCS is very interesting..i would like to test it..
I guess the answer depends on what raw B+ voltage you're starting with.
370VCT ? (That's 185V-0-185V).
The raw DC voltage will probably be something like 185(1.3) = 240V DC.
To get down to 165V DC you'll need to drop 75V.
75V voltage drop with 0.035A current draw would require a series resistance of 2,143 ohms.
What is the DC resistance of your power supply choke?
Will you be using a tube rectifier? If so, a which one? 5Y3GT? 6X4/EZ90? Each different type will have a different voltage drop.
A 5Y3GT will probably drop about 30V, so you'd need to drop another 45V across the LC and RC sections.
Remember, you can't put too large a value of reservoir capacitor after a tube rectifier without the rectifier burning out prematurely from large current spikes at power-on. Typically, only a 22uF cap is used after a 5Y3GT. Going with a higher value capacitor will overstress the rectifier tube.
Silicon rectifiers can withstand much larger current surges, so you can use larger value capacitors with silicon.
My first instinct would be to use the CLC first (right after the rectifier), then add RC sections to drop the voltage and filter out ripple.
Multiple RC sections will be more effective at reducing ripple than one big resistor and capacitor (RC, so CLCRC).
So perhaps CLCRCRC, or something like that.
The smaller the values of resistance and the larger the values of capacitance, the better (for lower PSU output impedance).
Of course the best solution would be a regulated B+ supply.
370VCT ? (That's 185V-0-185V).
The raw DC voltage will probably be something like 185(1.3) = 240V DC.
To get down to 165V DC you'll need to drop 75V.
75V voltage drop with 0.035A current draw would require a series resistance of 2,143 ohms.
What is the DC resistance of your power supply choke?
Will you be using a tube rectifier? If so, a which one? 5Y3GT? 6X4/EZ90? Each different type will have a different voltage drop.
A 5Y3GT will probably drop about 30V, so you'd need to drop another 45V across the LC and RC sections.
Remember, you can't put too large a value of reservoir capacitor after a tube rectifier without the rectifier burning out prematurely from large current spikes at power-on. Typically, only a 22uF cap is used after a 5Y3GT. Going with a higher value capacitor will overstress the rectifier tube.
Silicon rectifiers can withstand much larger current surges, so you can use larger value capacitors with silicon.
My first instinct would be to use the CLC first (right after the rectifier), then add RC sections to drop the voltage and filter out ripple.
Multiple RC sections will be more effective at reducing ripple than one big resistor and capacitor (RC, so CLCRC).
So perhaps CLCRCRC, or something like that.
The smaller the values of resistance and the larger the values of capacitance, the better (for lower PSU output impedance).
Of course the best solution would be a regulated B+ supply.
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Ciao.
I've two 5H inductances with a dc resistace of 70 ohm..and one 6H with a resistance of 220 ohm.
I will not use tube rectifiers but two silion dioded.
First idea i tested on PSUD is based on 47Uf..2.4k resistor..220Uf...6H..220Uf..plus 10uf and 1F pp caps .
I could try a CLCL at the beginning and several RC to reduce voltage and ripple...what do you think?
I've two 5H inductances with a dc resistace of 70 ohm..and one 6H with a resistance of 220 ohm.
I will not use tube rectifiers but two silion dioded.
First idea i tested on PSUD is based on 47Uf..2.4k resistor..220Uf...6H..220Uf..plus 10uf and 1F pp caps .
I could try a CLCL at the beginning and several RC to reduce voltage and ripple...what do you think?
By the way, Any literature about Psu design to suggest?
I woulld like to learn more about...ripple calculation...impedance and so on...
Many thanks for your support.
Maurizio
I woulld like to learn more about...ripple calculation...impedance and so on...
Many thanks for your support.
Maurizio
As an introduction, I think this is really good, clearly written and easy to understand, yet thorough:
Designing Power Supplies for Tube Amplifiers, 2nd Edition - Merlin Blencowe
I've gotten a lot out of this book as well:
Designing High-Fidelity Tube Preamps - Merlin Blencowe
This book is also very worth reading, and is highly regarded:
Valve Amplifiers, 4th Edition - Morgan Jones
This is one of the essential original texts from the days before transistors were available:
Radiotron Designers Handbook, 4th Edition - Langford-Smith
There are others that are worth reading as well...
Designing Power Supplies for Tube Amplifiers, 2nd Edition - Merlin Blencowe
I've gotten a lot out of this book as well:
Designing High-Fidelity Tube Preamps - Merlin Blencowe
This book is also very worth reading, and is highly regarded:
Valve Amplifiers, 4th Edition - Morgan Jones
This is one of the essential original texts from the days before transistors were available:
Radiotron Designers Handbook, 4th Edition - Langford-Smith
There are others that are worth reading as well...
Good Morning .
I made some test by my own.
I tested one PSU with a CLCLC stage followed by two RC stages to reduce the voltage. I realized that one small hum issue i'd already on the right channer became worst..not that bad..but just increased..
Because the Main transformer doesn't have any electrostatic shield..i assumed that on of inductance was influenced by some magnetic fied.
As second step..i used a CRCLCRC filter...and the hum on the right channel decreased...
The inductance i used is different as well..is a new one with a 6H value.
The others have 5H...and some years...i do not know if they have some problems caused by the storage.
Rongon i ordered the Design Power supplies..book from Amazon.
Have a good day.!!!
I made some test by my own.
I tested one PSU with a CLCLC stage followed by two RC stages to reduce the voltage. I realized that one small hum issue i'd already on the right channer became worst..not that bad..but just increased..
Because the Main transformer doesn't have any electrostatic shield..i assumed that on of inductance was influenced by some magnetic fied.
As second step..i used a CRCLCRC filter...and the hum on the right channel decreased...
The inductance i used is different as well..is a new one with a 6H value.
The others have 5H...and some years...i do not know if they have some problems caused by the storage.
Rongon i ordered the Design Power supplies..book from Amazon.
Have a good day.!!!
