Google is your friend.
To the circuit above: it is a voltage regulator with a current limiter. It does not regulate the current, because, you can't regulate voltage and current at the same time as they are tied together through ohms' law.
What the above does is regulate the set voltage and then when current exceeds the set limit, limit it, but that then results in the voltage dropping. Either or.
In your case, you could set the voltage at 2.5V. Since the current is expected to be 1.5A, the current limit could be set to 2A so that in case of a failure the output current is limited to 2A. In the extreme case of an output short, obviously Vo would drop to zero but the current would be limited to 2A.
But in your use case the current limiter is not necessary. Look at a simple LM317 voltage regulator, the data sheet has lots of examples. Don't let the many graphs scare you, just ignore them and go to the application examples, like fig 16 & 17. Extremely simple and indestructable.
Jan
To the circuit above: it is a voltage regulator with a current limiter. It does not regulate the current, because, you can't regulate voltage and current at the same time as they are tied together through ohms' law.
What the above does is regulate the set voltage and then when current exceeds the set limit, limit it, but that then results in the voltage dropping. Either or.
In your case, you could set the voltage at 2.5V. Since the current is expected to be 1.5A, the current limit could be set to 2A so that in case of a failure the output current is limited to 2A. In the extreme case of an output short, obviously Vo would drop to zero but the current would be limited to 2A.
But in your use case the current limiter is not necessary. Look at a simple LM317 voltage regulator, the data sheet has lots of examples. Don't let the many graphs scare you, just ignore them and go to the application examples, like fig 16 & 17. Extremely simple and indestructable.
Jan
my 4p1l use 2.1 AC ( little hum) but no current limit. 5 years of usage with no current limit, tube still work fine.
May be AC is best option now trade off with little hum.
Just balance trimpot to get the hum lowest
May be AC is best option now trade off with little hum.
Just balance trimpot to get the hum lowest
1.6A is too tight. Tubes have varying heater currents, the nominal is just that, a nominal.
The tube data sheet normally shows something like +/-10% on the heater.
Jan
The tube data sheet normally shows something like +/-10% on the heater.
Jan
Ok I wait for others to make prototype.
I think 45 is popular. Due to sound good.
Others will make it and show me the filament.
AC is ok the hum is not much when I listen at shop. Worst solution is AC and let current go as my 4p1l. It is prove that tube is durable for 5 years even no current limit.
But I think DC is better. Hope someone build 45SE and share filament schematic
PS when i know something on my expertise, I share information to someone not know. Because it is good practice
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I have built my fair share of heater regulator pcb's
Below a schematic i still want to try. it uses a zener 6.2V reference and a matched BJT to compensate for the VBE drift inherent in these kind of designs.
I will breadboard this schematic and let you know how it performs.
Cheers,
V4lve
Below a schematic i still want to try. it uses a zener 6.2V reference and a matched BJT to compensate for the VBE drift inherent in these kind of designs.
I will breadboard this schematic and let you know how it performs.
Cheers,
V4lve
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I am looking forward to see your filament.
THANK YOU for sharing
If omit Little hum of AC filament, I think it is ok for newbie DIYER.
The hum need to hear near speakers.
However, for many listeners hum might not satisfied
You are so nice. Please let me know when you finish it.
https://drive.google.com/drive/folders/11Ls6KP3z-6TMHV1S1CS4FC0SsM3Dg5iB
this may be good for someone whom has knowlegge to adapt.
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That is a cursed schematic, i doubt it will work nicely.
Offtopic.
Attached the schematics of my 0-300V 0-200mA Lab power supply, the reference section with REF02 should be altered, as under low VIN conditions the IC will latch up, but the primary schematic is tested and working. its just that the reference is sub-optimal.
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If not filament bias, just 2.5V and let current flow then
These 2 boards seem ok. It is commercial and tested.
If do filament bias then Rod coleman and MR enzo are the choice.
But for 45 2 watts not necessary.
I just listen the AC hum at the amp shop again. I confirm 45 with just AC HUM adjust . HUM is low. Seem acceptable to my ears. However if use 45 for headphone amp, AC is not reccommend.
There must be no HUM in headphone because it is very near to ears. Unlike speakers you sit 2-3 meters away
These 2 boards seem ok. It is commercial and tested.
If do filament bias then Rod coleman and MR enzo are the choice.
But for 45 2 watts not necessary.
I just listen the AC hum at the amp shop again. I confirm 45 with just AC HUM adjust . HUM is low. Seem acceptable to my ears. However if use 45 for headphone amp, AC is not reccommend.
There must be no HUM in headphone because it is very near to ears. Unlike speakers you sit 2-3 meters away
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For maximum tube life you want to current limit the tube filaments on turn on, when they are much lower resistance. And you want to hold off on cathode current/plate voltage until the heaters are up to temperature. (I learned this designing supplies for CRT's for high volume computer applications). Cathode current before the cathode is at operating temperature can "strip" the cathode of active surface and degrade the tube. Anyone designing tube circuits should read this book: https://worldradiohistory.com/BOOKS...ost Out Of Vacuum Tubes - Robert B. Tomer.pdf If you were GE or RCA in the 1950's and 1960's designing table radios you did not care about reliability BUT designing navigation for submarines or undersea repeaters you cared a LOT.
Local shop sell 45 with AC filament, there is a little HUM.
If omit longevity of tube, my major requirement is NO HUM or lesser HUM than AC
My question is if not concern about CURRENT LIMIT, using DC to lit. Are there less hum?
Then using only diode bridge + capacitor filter to get clean DC is suffice?
If omit longevity of tube, my major requirement is NO HUM or lesser HUM than AC
My question is if not concern about CURRENT LIMIT, using DC to lit. Are there less hum?
Then using only diode bridge + capacitor filter to get clean DC is suffice?
This is how I limit the heater inrush current.
The NTC is in the heater return line and limits the current to a bit more than nominal.
After some time the FET gate rises and turns on the FET hard which shorts the NTC.
The FET is a small smd device that has 40A rating and just 8milliOhms Rds(on).
The top of the R goes to the 6.3VDC heater line.
Except for the disc NTC it's all smd and find space within the tube socket area on the board underside.
Works like a charm.
Jan
The NTC is in the heater return line and limits the current to a bit more than nominal.
After some time the FET gate rises and turns on the FET hard which shorts the NTC.
The FET is a small smd device that has 40A rating and just 8milliOhms Rds(on).
The top of the R goes to the 6.3VDC heater line.
Except for the disc NTC it's all smd and find space within the tube socket area on the board underside.
Works like a charm.
Jan
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AC filament can induce hum. In the distant past a pot was used across the AC filament with the wiper to ground to minimize hum. DC can be better IF it doesn't have AC leakage. A 3 terminal regulator set up for both current and voltage limits should be perfectly adequate. The filament is ultimately just a resistor. Biasing the filament positive wrt the cathode helps ensure its not influencing the signal.
All this tweaking to get good performance from tubes made the transition to semiconductors really attractive back in the 1960's.
All this tweaking to get good performance from tubes made the transition to semiconductors really attractive back in the 1960's.
I forgot to sharing end result
1. For 45SE CLCRC 10Henry with simple HV reg modify from preamp PV12 using zener diodes
2 AC filament to 45
Result is ok from speaker no hum no buzz
From headphone can hear very small hum
Va is 300VDC FIXED bias around 58-62v both tubes not equal run at 34ma. Both
It is a hint for someone who want to make 45 but lack of knowledge of CCS DC filament or good quality HV REG as T-reg as me
I think the result is acceptable with easy primitive method
But of course rod coleman DC AND T-Reg must be better.
I just give alternative for someone has few knowledge in tube amp such 45SE
PS 45 SE sound better than my old 4p1l PP
1. For 45SE CLCRC 10Henry with simple HV reg modify from preamp PV12 using zener diodes
2 AC filament to 45
Result is ok from speaker no hum no buzz
From headphone can hear very small hum
Va is 300VDC FIXED bias around 58-62v both tubes not equal run at 34ma. Both
It is a hint for someone who want to make 45 but lack of knowledge of CCS DC filament or good quality HV REG as T-reg as me
I think the result is acceptable with easy primitive method
But of course rod coleman DC AND T-Reg must be better.
I just give alternative for someone has few knowledge in tube amp such 45SE
PS 45 SE sound better than my old 4p1l PP