Hello everybody.
This is a 6X4 tube power supply for Audio Note M7Kit11 preamplifier.
I have built more than 10 tube preamplifiers since 2010 trying to copy designs from big brands like Marantz, Audio Note, Audio Research etc.
I have tried many different tube power supplies using 5U4, 5Y3 and a couple of others. Hum has been always present. Little but it was there making me nervous.
A couple of months ago I found a schematic from the M7Kit11 preamplifier and I decided to give it a try. I drew the pcb with sprint layout 6.0 adding a second 6X4 tube replacing the original 6X5 of the AN design.
The result was brilliant. Excellent sound and NO hum at all.
This is my design and I want to share it with all of you. The gerbers of the tube power supply and the preamplifier are available to everyone who would like to build it. Your comments are more than welcome
Cheers
This is a 6X4 tube power supply for Audio Note M7Kit11 preamplifier.
I have built more than 10 tube preamplifiers since 2010 trying to copy designs from big brands like Marantz, Audio Note, Audio Research etc.
I have tried many different tube power supplies using 5U4, 5Y3 and a couple of others. Hum has been always present. Little but it was there making me nervous.
A couple of months ago I found a schematic from the M7Kit11 preamplifier and I decided to give it a try. I drew the pcb with sprint layout 6.0 adding a second 6X4 tube replacing the original 6X5 of the AN design.
The result was brilliant. Excellent sound and NO hum at all.
This is my design and I want to share it with all of you. The gerbers of the tube power supply and the preamplifier are available to everyone who would like to build it. Your comments are more than welcome
Cheers
Be sure that the current that flows though choque input filter is suffient to make it not to run dry. Say, that current flows in it during the 360 electrical degrees of the line frequency. Otherwise, voltage will not be completely filtered and will go to an unpredictable value between 0.9xACV to 1.4xACV being ACV the ac voltage RMS available at each 6X4's plate.
I hardly like choque input mainly with tube rectifiers, but be careful with it. And still more warning when one or more or all tubes being the PSU's load are removed from the zockets or disconnected completely from PSU.
I hardly like choque input mainly with tube rectifiers, but be careful with it. And still more warning when one or more or all tubes being the PSU's load are removed from the zockets or disconnected completely from PSU.
6X4 requires a 10h choke. i have built many tube power supplies based on 6X4 using the same 10H choke and they work fine with 2 t0 5 mV ripple.
I think that the designer has placed the choke after rectification for using a bigger filter capacitor. ( 100uF instead of 10 ).Indeed the current that flows in most of the tube preamps is not more than 30mA according to the Tubecad.
The above schematic is a very simple tube PS and works perfectly. The choke values are 150 Ohm, 200mA, 10H.
The transformer is a 300-0-300 120mA and the tubes JAN6X4. Can you be more specific?
Thanks a lot
https://electronicscoach.com/choke-filter.html
Here you will found a well explained web page. It's difficult to explain with few words. Ovbiously there are lots of them.
Over it, keep in mind that an inductor can saturate by the presence of DC current flowing in it (This is the case) and by tha AC voltage across it. Thus, an inductor usually is designed for a specific work and no necesarily will do its job properly out of this conditions. Thus, the brand and model of choke are irrelevant.
I learned lots about chokes and I designed mines several times. So what I say is from my experience and my read knowledge. It's not my objective to criticize your job.
Here you will found a well explained web page. It's difficult to explain with few words. Ovbiously there are lots of them.
Over it, keep in mind that an inductor can saturate by the presence of DC current flowing in it (This is the case) and by tha AC voltage across it. Thus, an inductor usually is designed for a specific work and no necesarily will do its job properly out of this conditions. Thus, the brand and model of choke are irrelevant.
I learned lots about chokes and I designed mines several times. So what I say is from my experience and my read knowledge. It's not my objective to criticize your job.
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Cap multiplier and choke filter are different things. They can coexist in a circuit but one doesn't replace the other.
I have read carefully the article from that site and I am aware of all those terms in using a chole. My design is taken from an Audio Note design (which I trust) and it would be identical whether I didn't want to use 6X4( I have plenty of them in stock) in place of 6X5 changing just the choke value from 20H to 10H due to the tube data sheet. My previous power supplies were not so different. This is what I mean
That very simple power supply below has worked in 3 of my preamps for many years. It's an RCLC but it would work as an LCRC too. Its only disadvantage is the little hum. I believe that any comment on a design or a schematic is very creative and welcome. This is the purpose of publishing our designs. By the way, your handmade chokes are superb.
Cheers
It would be interesting if you have an oscilloscope or a VOM frequency-meter to determine if hum is 50/60Hz or 100/120Hz or if your ears are able to discriminate between them. This may be the starting point to see if hum provides from PSU or from heaters or coupled from wiring into the amplifier chain.
Regarding the inductor value, again: its value depend on load characteristics and not regard the rectifier kind. Data sheets only publishes certain values as a mode to show us the tube capabilities or characteristics, but don't mean you must use those value.
Here is a photo from one big lord of the electronics. Look at the formula rounded in blue. What this formula said is that the inductance of the choke and the load resistance (including transformer winding resistance if it isn't negligible) are realted toguether by a constant rounding 1000. Note the independence of this statement upon rectifier means (tube vacuum or mercury vapor, silicon, copper oxide, selenium or even mechanical). Only depends on load resistance. So for proper choke input filter job, it must be evaluated in circuit.
Regarding the inductor value, again: its value depend on load characteristics and not regard the rectifier kind. Data sheets only publishes certain values as a mode to show us the tube capabilities or characteristics, but don't mean you must use those value.
Here is a photo from one big lord of the electronics. Look at the formula rounded in blue. What this formula said is that the inductance of the choke and the load resistance (including transformer winding resistance if it isn't negligible) are realted toguether by a constant rounding 1000. Note the independence of this statement upon rectifier means (tube vacuum or mercury vapor, silicon, copper oxide, selenium or even mechanical). Only depends on load resistance. So for proper choke input filter job, it must be evaluated in circuit.
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You are correct chokes and cap multipliers are different and usually not interchangeable.
This is a case where they are.
A cap multiplier will remove more noise, generate zero magnetics and protect the rectifier from high inrush current of subsequent capacitance. The rectifier will see only the first filter capacitance.
A cap multiplier can reject 70 dB or more ripple at 120 hz.
If you're making a crossover there is no replacement for the inductors there.
This is a case where they are.
A cap multiplier will remove more noise, generate zero magnetics and protect the rectifier from high inrush current of subsequent capacitance. The rectifier will see only the first filter capacitance.
A cap multiplier can reject 70 dB or more ripple at 120 hz.
If you're making a crossover there is no replacement for the inductors there.
But cap multiplier needs sufficien voltage drop as to cause series pass element to not saturate, otherwise its effect is lost temporarily. ITOH inductor integrates AC voltage into a DC current with smaller loss of voltage. Certainly they are heavy, bulky and expensive. But as I make my own chokes from burned or discarded 220/110V traffos nowadays not necessary, it is a question of taking a time to wind the coil only and adjust gap to minimum output ripple in circuit.
Thanks a lot for your analysis.
I have both an oscilloscope and an HP frequency counter. I think that the hum comes from the heaters because I have supplied them with floating DC.
The AN power supply connects the minus 12 volts to a voltage divider and a capacitor referenced to the ground. The chassis ground goes through a 10R resistor I always use star grounding.
So where can I measure the load resistance for applying it to the formula?
@metanastis : please note rhat what I wrote refers mainly to the schematic at post #1 where a choke input filter is showed. This doesn't apply to the schematic at post #13 where capacitor input is shown.
National Instruments simulator 12.0 says that AN preamp draws 4,66mA at 380 VDC.