@nevergetold you are finding a way of reducing excess (unwanted voltage on the cheap. It will put some strain on the choke with the additional ripple that will have to be delt with later in the power supply. small capacitors before the choke will reduce voltage. I have noticed that this has some effect up to about 7.5 mfd.
Remember folks, this is my first time ever looking at tube rectification and also my first time ever looking at a single-ended amplifier. I bought this little kit to learn about both. Well, I am learning a lot, that's for sure.
I started this thread with the intention of changing it to solid state because I feared short life for the rectifier tube. It turns out that tube life can be made reasonable. The reference here to diodes before the rectifier is great. I did stumble across it yesterday in another thread too, although without the documentation for it. I love the idea.
Unfortunately, if I am doing this right in PSUdesigner, it looks like we will be 50 to 100 volts below ideal if using the 5Ц4С, with only about 295 volts using a 6.8uF cap (4uF is specified). I was astonished at this result, and I find it hard to believe this isn't user error on my part. If someone can explain how and why it is so low, please do.
If this is correct, I see two possible solutions to get more voltage out of this power supply, with one being a different rectifier tube, and another less expensive way being solid state. My understanding is that 295 volts might work, but is too low for anything approaching ideal performance for the EL34.
Is 5AR4 the best tube option? 5AR4 looks relatively expensive and more than I want to spend. I don't want to be replacing expensive rectifier tubes, so the least expensive options that will provide more voltage than the 5Ц4С are ideal in my case. Oh, and I love the look of the gigantic Coke bottle rectifier tubes. 5U4G looks even more expensive than 5AR4. Russian tubes that are available are fine with me if they are inexpensive and reliable. Otherwise, I may be back where I started, with solid state replacement.
I started this thread with the intention of changing it to solid state because I feared short life for the rectifier tube. It turns out that tube life can be made reasonable. The reference here to diodes before the rectifier is great. I did stumble across it yesterday in another thread too, although without the documentation for it. I love the idea.
Unfortunately, if I am doing this right in PSUdesigner, it looks like we will be 50 to 100 volts below ideal if using the 5Ц4С, with only about 295 volts using a 6.8uF cap (4uF is specified). I was astonished at this result, and I find it hard to believe this isn't user error on my part. If someone can explain how and why it is so low, please do.
If this is correct, I see two possible solutions to get more voltage out of this power supply, with one being a different rectifier tube, and another less expensive way being solid state. My understanding is that 295 volts might work, but is too low for anything approaching ideal performance for the EL34.
Is 5AR4 the best tube option? 5AR4 looks relatively expensive and more than I want to spend. I don't want to be replacing expensive rectifier tubes, so the least expensive options that will provide more voltage than the 5Ц4С are ideal in my case. Oh, and I love the look of the gigantic Coke bottle rectifier tubes. 5U4G looks even more expensive than 5AR4. Russian tubes that are available are fine with me if they are inexpensive and reliable. Otherwise, I may be back where I started, with solid state replacement.
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Is this my other best option vs. switching to a 5AR4 or some other tube rectifier? I have all of these parts on hand, so zero expense. About 385 volts if I have done it correctly. A CL-90 would shave off another 2-3 volts I suppose.
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When making justifications for 'this or that' then perhaps use the expected total load current for sim - which I thought was more likely to be 125mA, rather than 150mA, or have you changed your target? Also set a 1 sec delay if you want the table of results to show 'steady state' values, otherwise those values can be coloured by the initial startup response.
It is not 'toooo' difficult to add a diode model to your PSUD2 application - there are on-line tutorials/notes I recall. If you are brave enough to have a go then you could add a 2x 5U4C model as a way to simulate the hybrid bridging option. The PSUD2 full wave configuration would then use your new 2x5U4C diode. That may seem a bit strange but should work - note that the ss diodes are not included in the sim as they have no significant affect, and each time half of the secondary winding conducts then it does so through 2x 5U4C in parallel, so the final simulated load voltage should be close to what is expected.
It is not 'toooo' difficult to add a diode model to your PSUD2 application - there are on-line tutorials/notes I recall. If you are brave enough to have a go then you could add a 2x 5U4C model as a way to simulate the hybrid bridging option. The PSUD2 full wave configuration would then use your new 2x5U4C diode. That may seem a bit strange but should work - note that the ss diodes are not included in the sim as they have no significant affect, and each time half of the secondary winding conducts then it does so through 2x 5U4C in parallel, so the final simulated load voltage should be close to what is expected.
I got that current value from a prior post IIRC.
The rest of the post is too complicated for me to figure out in PSUdesigner, and it doesn't look like the 5Ц4С rectifier tube is capable of 350-400V, which is what others have recommended as a target voltage. It looks more like 300 or less.
Seems like my options are 5AR4 or solid state to hit the recommended voltage.
- 5AR4 costs money.
- Solid state as shown above is "free" in that I have all of the parts on hand. I also have 220uF - 220uF - 100uF on hand. A few added volts with those.
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Perhaps review post #12 for why I recommend using 125mA for sims.
Use the PSUD2 calculator to determine the secondary effective resistance - you show 48 ohm, but I get 192 ohm when I use the calculator.
5AR4 may get you close to 350V, but note that the effective resistance of the power transformer is the most influential limiter of your output voltage, as a 5AR4 would be working well within its peak current limits.
Whether an output stage has 300V or 400V for B+, it will still work.
Use the PSUD2 calculator to determine the secondary effective resistance - you show 48 ohm, but I get 192 ohm when I use the calculator.
5AR4 may get you close to 350V, but note that the effective resistance of the power transformer is the most influential limiter of your output voltage, as a 5AR4 would be working well within its peak current limits.
Whether an output stage has 300V or 400V for B+, it will still work.
Then I am doing it wrong and need screenshots.
That seems to be the consensus. Now aiming for 350V to 400V. Solid state seems to get me to 385 volts or so with parts already on hand.
Post #100 shows the calculator - bring that up again and input the same values but use 48 and not 95 for the secondary winding resistance.
And that is where I went wrong. Now I know. Thanks!
With the correct rectifier tube (included with the kit), 125mA draw, and 192 ohm transformer, I get just over 280V. Theoretically we might get the 310V specified on the schematic, but I'm ready to abandon the power supply shown on the schematic. I can do whatever I want since it will be point-to-point wired, and I am discarding all of the parts that came with the kit anyway, keeping chassis and transformers of course. I may still get bigger output transformers form China, especially if an impedence over 3.5k is indicated.
Solid state has the advantage of no out of pocket cost since I have everything on hand. Advantage: solid state. I can do CRCLC or CLCRC, but it seems that the power transformer and choke would be happier with the CRCLC option. The power dissipated by a 100 Ohm resistor looks like about 2.5 watts. I can live with the power dissipation. I could use 50 ohm I guess.
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There are a number of issues here I think.
One is the peak current.
The peak current is much higher that the DC output current. If you look at the simulation results you posted you will see the peak current is in Amps and the DC output is around 150mA. So peak current is 10 times or more over average (DC) current.
Next is total DC series resistance that sees those peak input current pulses. These include primary DC resistance times the turns ratio to each side of the center tap, total secondary DC resistance divided by 2 (for full-wave CT design you show), rectifier loss (get from data sheet) input capacitor series DC resistance.
Power supply voltage drop is based on peak current times this total DC series resistance that sees the peak input current pulses. So if your total DC series resistance is several hundred ohms and you have a peak current of lets say 1Amp there is a surprising and large total voltage drop at the first input capacitor.
Lastly I am not really familiar with this tool you are using (I use Pspice with my power simulations, far more complicated but more complete).
It is not 100% clear to me how the transformer is being modeled for a center-taped transformer from the drop down menu. Is the secondary voltage on the drop down menu the total secondary voltage or for each side of the center tap. Same question to the dc resistance and turns ratio.
As experiment to figure this out I would dumb down the circuit. Have no inductor or second capacitor.
Also use silicon diodes so the tube loss is not in the circuit. Put a very light load on the supply like 1mA. Then look at the resulting voltage is should be about 1.414 (RMS to peak ratio) times the voltage on each side of the center tap. If not figure out why and sort out the drop down menus. Then add your load and see what the voltage drop is. This will tells you the transformer loss alone. Adjust the transformer to a point where the voltage is higher than your target by maybe 30~50 DC volts or so. Then replace the silicon diodes with the tube you want to use. Your voltage will drop (maybe a lot!) and to correct either use a different tube (5AR4 maybe) or increase the transformer secondary voltage to get the voltage back to what you want.
Have fun and good luck...
One is the peak current.
The peak current is much higher that the DC output current. If you look at the simulation results you posted you will see the peak current is in Amps and the DC output is around 150mA. So peak current is 10 times or more over average (DC) current.
Next is total DC series resistance that sees those peak input current pulses. These include primary DC resistance times the turns ratio to each side of the center tap, total secondary DC resistance divided by 2 (for full-wave CT design you show), rectifier loss (get from data sheet) input capacitor series DC resistance.
Power supply voltage drop is based on peak current times this total DC series resistance that sees the peak input current pulses. So if your total DC series resistance is several hundred ohms and you have a peak current of lets say 1Amp there is a surprising and large total voltage drop at the first input capacitor.
Lastly I am not really familiar with this tool you are using (I use Pspice with my power simulations, far more complicated but more complete).
It is not 100% clear to me how the transformer is being modeled for a center-taped transformer from the drop down menu. Is the secondary voltage on the drop down menu the total secondary voltage or for each side of the center tap. Same question to the dc resistance and turns ratio.
As experiment to figure this out I would dumb down the circuit. Have no inductor or second capacitor.
Also use silicon diodes so the tube loss is not in the circuit. Put a very light load on the supply like 1mA. Then look at the resulting voltage is should be about 1.414 (RMS to peak ratio) times the voltage on each side of the center tap. If not figure out why and sort out the drop down menus. Then add your load and see what the voltage drop is. This will tells you the transformer loss alone. Adjust the transformer to a point where the voltage is higher than your target by maybe 30~50 DC volts or so. Then replace the silicon diodes with the tube you want to use. Your voltage will drop (maybe a lot!) and to correct either use a different tube (5AR4 maybe) or increase the transformer secondary voltage to get the voltage back to what you want.
Have fun and good luck...
I don't think I am going to use tube rectification. I went in that direction in the middle of this thread, but when I went down that path, I didn't like the voltage drop. Thus, the solid state circuit option instead. Somebody told me to put the L in front of the R to make it CLCRC. I have no idea why. I have larger diodes on hand, 3 amps I think, and the caps on hand as well as the choke. I need to power a stereo single-ended amplifier, so one EL34 per channel at dissipation up to 90% if possible, plus the 6H8C driver tubes, one per channel. The transformer winding for the rectifier tube would go unused, which should make a relatively weak Chinese power transformer happier. It's large, but who knows how efficient it is.
I think earlier someone said that anywhere between 300 and 400 volts should be fine, with 350 a nice number. This one should be roughly 335 volts, so within that range. If it's a little more or a little less when built, still within range.
Compared to:
I think earlier someone said that anywhere between 300 and 400 volts should be fine, with 350 a nice number. This one should be roughly 335 volts, so within that range. If it's a little more or a little less when built, still within range.
Compared to:
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The choke 'works' better with some ripple voltage across it (ie. after the first filter cap), rather than further along where the ripple voltage would be lower.
I'd recommend not using 'larger' diodes than necessary, as they may let through more noise (related to larger junction capacitance and larger reverse recovery junction charge). In your situation, UF4007 would appear to be an ok choice.
I'd recommend not using 'larger' diodes than necessary, as they may let through more noise (related to larger junction capacitance and larger reverse recovery junction charge). In your situation, UF4007 would appear to be an ok choice.
I can put two in my shopping cart for my next order. I just happened to have some 3A Chinese models on hand. I can try UF4007 for very little cost since I'm already paying for shipping on two shopping carts.
Thanks. As a novice, the concept makes no sense to me right now, but I'm learning. Thanks! 👍
I think what I meant to do was RCLC, since I thought the transformer "seeing" a resistor might be easier on a transformer that may not be very strong and/or will be running hot. I think not using the rectifier tube winding on the transformer will help, but I'm not sure by how much. At a certain point, there is only one way to find out. Some time in January, I'll build a temporary power supply on a board and then ask for additional help with the rest of the amplifier schematic.
It's highly unlikely you would notice any difference between using the 3A diodes or UF4007 diodes - it is just a recommendation based on low level noise.
Chokes provide more 'inductance' when they have more ripple voltage across them, so you get 'more bang for your buck' in that first location. Another subtlety is that a choke lets through high frequency content differently to say a 4k7 resistor - as it presents a small shunt capacitance above 10khz, whose impedance is likely similar to 4k7 resistor at 100kHz.
Chokes provide more 'inductance' when they have more ripple voltage across them, so you get 'more bang for your buck' in that first location. Another subtlety is that a choke lets through high frequency content differently to say a 4k7 resistor - as it presents a small shunt capacitance above 10khz, whose impedance is likely similar to 4k7 resistor at 100kHz.
Perfect explanation. I can understand that. This is why I had to hire a tutor weekly to survive physics in college!
I think I read something about this while researching CLCRC vs. CRCLC. The effect is a reduction in the noise that appears in the power from our AC outlets, right?