Simplest or easyest dc filament supply for 300B

[soulmerchant]

How many parts are in an SMPS?
Maybe you did not build it, but somebody did (or a pick and place machine did).
Transistor, diode, coil, PCB, resistor, capacitor, connector, . . . .
Some are quiet, and some are noisy.
Take a CD player that has super-audio spurs (not a problem by itself), and beat those with switcher spurs, then intermodulate the two, and you have spurs folded back into the audio band.

5V batteries are hard to come by.
A 6V lantern battery and a resistor will only take 2 parts to get 5V, and then 3 parts, and then 4 parts, and then . . . every time you replace the lantern cell.
And just try and find a place that will recycle all those lantern batteries for you.
environmentally responsible?

The above are 'Simply' my opinion.

6A3sUMMER - I dare you to try a 99cent SMPS board. They're dirt cheap. I just mount them on top my own board since they are so small.

I've been running them on cheap china tubes now for a while, plus my 'cheap and dirty' phono, which sounds pretty darn good.

These things have not blown-out or anything for me and have performed far better than I could have ever expected. Voltages are rock-solid stable. A drop of Loctite glue seems to work fine on the cheep smp potentiometer.

Of course you should add a rectifier.. and an input cap... Hmmm still crazy cheap. And this idea wasn't my own, it had been suggested to me by another member here. My initial response was that it was also heresy... but after fixing my daughter's 5V SMPS phone chargers, I thought.. hey.. why not try it?

 

[soulmerchant]

hate it when this double post thing happens..

 

[soulmerchant]

5v 2a switching power supply , are a good option for each filament of 300B ?

In my experience, you need to look at the specifications quite closely. look at the parts used on the SMPS... look up their specs sheets too.

Some have switching frequency at 180kHz... this is waaaay above what you will ever hear, but you can find ones that switch at even higher frequencies (up to around 1MHz). Also make sure that they can deliver enough power, especially at turn-on.

Some of the best I found are also the cheapest..

 

[juanitox]

spec says 30mv of ripple , not very good for me with Hf signal tubes around ..

 

[soulmerchant]

spec says 30mv of ripple , not very good for me with Hf signal tubes around ..

at 1MHz... sure you can hear that? I use HF signal tubes for input but still have dead silent output.

Better to have this ripple at 1MHz than use CRC or CLC and have it at 100Hz.

I understand if you feel stubborn not to try it. I was the same way until I experimented with my daughter's 'broken' cell phone charger...

 

[juanitox]

10mv of 100hz ripple is what you usually get before the Regulator or CCS feeding the filament not after .. or you have made a bad filter

I understand if you feel stubborn not to try it. I was the same way until I experimented with my daughter's 'broken' cell phone charger...

if i'm still alive after these sad event , i will try your cheap trick ..

 

[soulmerchant]

10mv of 100hz ripple is what you usually get before the Regulator or CCS feeding the filament not after .. or you have made a bad filter

compared to no ripple anywhere near audible spectrum using smps.... And it is incredibly cheap/easy, which is what the OP has requested.

I still have CLC in my "expensive" amplifier's filaments, which is in the living room... still have not got the nerve to try these things on rare WWII tubes/valves....

 

[6A3sUMMER]

MP1584EN 3A DC-DC Buck Step Down Converter Regulator Power Supply Module LM2596 | eBay

It would be nice if it did a lot more current. The start-up current on a 2A3 is very large.
Need a much different SMPS.

How much voltage of the switcher frequency is reflected back to the DC supply that powers the SMPS?

And how much DC voltage will make it run (what are the optimum DC voltage and current, to get various output voltages and currents)?
I might consider using a SMPS to run a 45 filament (1.5A run current).

Once you have set the pot, if the DC voltage that runs it varies, how much does the output voltage vary. For example, a mains power line that varies +/- 2.5%, will make the DC voltage to the SMPS vary +/- 2.5%.

 

[ChrisABC]

different voltage but some hints, precautions

Unique Tube Heater Supply

 

[6A3sUMMER]

ChrisABC,

Thanks!
Good article.

But that convinces me that Brute Force DC is for me.
Schottky Bridge, C, R, C is what I will use again.
A resistor is the simplest soft start circuit I know of (intrinsic)
I am not worried about the 1mV or 2mV of ripple on the DC for a 300B.
I have already done that. Next, I will do the same for a 2A3.

 

[SpreadSpectrum]

I've had pretty good luck lately buying AC-DC switching modules and adding additional passive LC filtering on the output. This was for some op-amp supplies, but it really cleaned up the output.

I just got some inductors and caps to do the same on my 841 filament switching supply (7.5V, 1.25A buck converter) and I hope to have the same success. I was able to find inductors with acceptable DCRs and good SRF, so we'll see how it all works out.

 

[6A3sUMMER]

Low pass filters can be a pain sometimes:

Inductors that have distributed capacitance (all that have turns do; a straight wire in free space does not have much), Capacitors that have series inductance (all do).

One time an engineer built a CLCLCLC low pass filter on a copper clad board using all SMT parts. It had 60 dB of out of band rejection.
When the circuit board was laid out, all the SMT 'solenoid' style inductors were lined up, and close together. Couple, Couple, Couple, was the name of the game.
The out of band rejection was 20 dB . . . time for another board layout!
All it took was to turn the middle L sideways (90 degrees reducing the coupling, and also intrinsically opened up the spacing). Success, 60 dB out of band rejection.

A little attention to details goes a long ways.
Amazing: A little Medicine Makes the Sugar Go Down (A slight Modification of "Mary Poppins").