Hello!
I have been working on a 200V power supply for a tube amplifier design.
Would any of you offer feedback on this design?
Image of circuit on dropbox
Link to LTSpice file
200V Tube Amp Supply.asc
I have been working on a 200V power supply for a tube amplifier design.
Would any of you offer feedback on this design?
Image of circuit on dropbox
An externally hosted image should be here but it was not working when we last tested it.
Link to LTSpice file
200V Tube Amp Supply.asc
Welcome to diyAudio 
Why not try attaching your images and .asc file directly to the forum. You stand a far better chance of replies if you do:
How to attach images to your posts.
Why not try attaching your images and .asc file directly to the forum. You stand a far better chance of replies if you do:
How to attach images to your posts.
I can get a cap that big.
EDIT: Yes, this is my first.
Let me link you to the basic design of the amp.
It is based on a PCB from AliExpress. A 3-tube, 3x 12AU7 design.
I'm expecting the load to be 65mA.
Two of the tubes have a 51k resistor in front of each, so their plates will be at about 24V, and the third tube, I suppose, the output stage will get a full 200v
And on average the plate to cathode resistance is about 7000Ohm
AliExpress Ground Grid Tube Preamplifier
The version I'm getting has no parts, just the PCB.
EDIT: Yes, this is my first.
Let me link you to the basic design of the amp.
It is based on a PCB from AliExpress. A 3-tube, 3x 12AU7 design.
I'm expecting the load to be 65mA.
Two of the tubes have a 51k resistor in front of each, so their plates will be at about 24V, and the third tube, I suppose, the output stage will get a full 200v
And on average the plate to cathode resistance is about 7000Ohm
AliExpress Ground Grid Tube Preamplifier
The version I'm getting has no parts, just the PCB.
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It seems noise free as a simulation, certainly by looking at the load current and/or voltage.
Is it practical though ? (I don't dabble with those hot glass bottles) For example how big and bulky is the inductor ?
I would tend to approach a problem like this by setting out the design goals... such as what level of ripple/regulation/tolerance are you aiming for... and then try and design a circuit to meet those goals with the focus being on economy of scale and efficiency.
As to your circuit though, yes, for the (steady) load current you want to be able to draw, it is near perfect as clean voltage source.
Is it practical though ? (I don't dabble with those hot glass bottles
) For example how big and bulky is the inductor ?I would tend to approach a problem like this by setting out the design goals... such as what level of ripple/regulation/tolerance are you aiming for... and then try and design a circuit to meet those goals with the focus being on economy of scale and efficiency.
As to your circuit though, yes, for the (steady) load current you want to be able to draw, it is near perfect as clean voltage source.
Attachments
The inductor is about 2in x 2in x 3.25in
Transformer, 2.5in, 3.6in, 3in
I'm not happy about the transformer, because this design calls for 200V
This one gets me closest to that ballpark. I don't need the excessive milliamps it can supply.
I don't like having to use a 500Ohm power resistor to act as a divider.
I don't know how the input ripple translates to output noise. So I'm not surprised if I'm going overkill in trying to kill it.
I also don't know how any feedback from the tubes will affect the power supply, or if that will talk to the other tubes.
I'm thinking of just getting the parts and trying stuff out. Maybe blow something up. YOLO.
Transformer, 2.5in, 3.6in, 3in
I'm not happy about the transformer, because this design calls for 200V
This one gets me closest to that ballpark. I don't need the excessive milliamps it can supply.
I don't like having to use a 500Ohm power resistor to act as a divider.
I don't know how the input ripple translates to output noise. So I'm not surprised if I'm going overkill in trying to kill it.
I also don't know how any feedback from the tubes will affect the power supply, or if that will talk to the other tubes.
I'm thinking of just getting the parts and trying stuff out. Maybe blow something up. YOLO.
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I don't understand the arithmetic in post 6.
I use a reservoir cap of 250uF to run a power amp, so 4700uF seems a bit excessive. Such a big cap may require a soft start circuit. It may also require safety interlocks as it will be storing a lot of energy.
On the other hand, 47uF may be a bit small. It will resonate at about 7Hz with the choke and so could cause subsonic problems.
PSU simulations can be misleading, as in real life grounding issues can override the near-perfect results obtained from huge caps in Spiceworld.
I use a reservoir cap of 250uF to run a power amp, so 4700uF seems a bit excessive. Such a big cap may require a soft start circuit. It may also require safety interlocks as it will be storing a lot of energy.
On the other hand, 47uF may be a bit small. It will resonate at about 7Hz with the choke and so could cause subsonic problems.
PSU simulations can be misleading, as in real life grounding issues can override the near-perfect results obtained from huge caps in Spiceworld.
Be that as it may, isn't every LC filter resonant? Bigger cap, lower frequency. Is there a resonant frequency to target?
Where does the 7k resistor come from?
Ideally, PSU resonances (which usually cause an increase in PSU output impedance) need to come well below the audio band, well below the LF rolloff of the audio circuit, but also above the typical envelope frequencies of music (although this last criterion is less of a problem with a Class A circuit such as a preamp). What is the LF rolloff of the preamp?
Ideally, PSU resonances (which usually cause an increase in PSU output impedance) need to come well below the audio band, well below the LF rolloff of the audio circuit, but also above the typical envelope frequencies of music (although this last criterion is less of a problem with a Class A circuit such as a preamp). What is the LF rolloff of the preamp?
The ’12AU7′ Tube | Effectrode
This website, and another datasheet I looked at seemed to suggest that the resistance of the plate is about 7k to 7.7k ohms.
Supposing that is true for all three tubes, and each tube has two plates, then they are pairs of 7k resistors in parallel.
How would you model them?
This website, and another datasheet I looked at seemed to suggest that the resistance of the plate is about 7k to 7.7k ohms.
Supposing that is true for all three tubes, and each tube has two plates, then they are pairs of 7k resistors in parallel.
How would you model them?
Oh gosh, I thought it was a plus! I was going to run them in parallel! Back to the drawing board
The 7.7k anode impedance quoted for the 12AU7/ECC82 is a dynamic/AC/slope impedance, not a DC resistance. The effective DC resistance (Va/Ia) is likely to be bigger than this, maybe 2 or 3 times bigger. It depends on bias.
The data you linked shows this. Dynamic anode impedance 7.7k, at that particular bias. DC resistance is 250V/10.5mA = 23.8k.
The data you linked shows this. Dynamic anode impedance 7.7k, at that particular bias. DC resistance is 250V/10.5mA = 23.8k.
Just the sum of the idle current, which for each 12AX7 section is likely to be less than 1mA, if you have three stages, then 3mA per channel, or 6mA for stereo. For simple PS, it's much easier to use PSUD2 instead of LTSpice...
To get an idea of what this is all about i tryed to reverse engineer from the photos of the preamp the schematic.
Must say, not too happy with what i found
The ground doesn't carry dc-current, makes the power supply easy (+and- 200V/8mA).
So, here it is
Mona
Must say, not too happy with what i found
The ground doesn't carry dc-current, makes the power supply easy (+and- 200V/8mA).
So, here it is
Mona
Attachments
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