Would there be any benefit to using a SMPS for 5V, 6.3V or 12.6V filament supply?
Better for IDH and worse for DHT tubes?
Just a thought because sometimes finding transformers with HV 6.3V & 5V can be tricky so putting a 5V SMPS in for the rectifier might be a clever thought.
Better for IDH and worse for DHT tubes?
Just a thought because sometimes finding transformers with HV 6.3V & 5V can be tricky so putting a 5V SMPS in for the rectifier might be a clever thought.
Last edited:
If you think it will be reliable enough, I can't see an issue. I prefer to have a transformer wound specifically for the job.
Especially since an AnTek with the HV & 6.3V is $39 plus the additional 5V 8A (I know) toroid is only another $18.
It's pretty cheap for quite a lot of power.
It's pretty cheap for quite a lot of power.
A transformer would be better as it is self limiting.
The SMPS will be trying to push out a lot of current to the heaters on cold start.
I have used DC and AC heaters and found there to be little difference in hum.
I would also be worried about the SMPS HF getting everywhere in the high impedance valve circuits.
Am LLC SMPS might be better as it is a sine wave into the transformer.
The SMPS will be trying to push out a lot of current to the heaters on cold start.
I have used DC and AC heaters and found there to be little difference in hum.
I would also be worried about the SMPS HF getting everywhere in the high impedance valve circuits.
Am LLC SMPS might be better as it is a sine wave into the transformer.
Last edited:
If you use a SMPSU for heaters you need to take account of inrush current. Most SPMSU have a very low residual current when they go into current limit. So if you use a 5A supply for 5A worth of heaters it will never power up because the heaters never get worm enough residual current to warm the heaters enough to start raising their resistance. As a rough rule, I have found your SMPSU needs to be rated at twice the nominal heater load to guarantee successful operation of heaters. Having said that, some SPMSUs are incredibly cheap. The ones that supply 12V for LED lamps are almost unbelievably cheap. I got a 12V 15A one for about £15.
Cheers
Ian
Cheers
Ian
I use smps for all my big tubes filaments, like 813 and gu81m. Use a thermistor to limit inrush current.
Hi,
I am buying this for my 6.3Vdc heater.
DC DC 4V 32V to 1 2V 32V 12A Step Down Power Apply High Power Good | eBay
I am buying this for my 6.3Vdc heater.
DC DC 4V 32V to 1 2V 32V 12A Step Down Power Apply High Power Good | eBay
Since the tube heaters in a Dynaco ST-35 consume about 25% of the total power draw, I reasoned that an outboard heater supply would allow the power transformer to run cooler and potentially improve regulation. Initially, I built a series regulated 6.3 VDC outboard supply to power the heaters, but was unhappy with the efficiency.
Next I pulled an old 220 watt (rated), computer power supply from the junkbox and found the 12V line is rated well in excess of the heater current draw of the ST-35. It turned out to be rather easy to add an adjustment to the output to bring it up to 12.6 volts.
I was pleased to find that not only is the output voltage very stable, but the noise level is low. It’s been in use, “lighting up” my power amplifier for over 2 years with no issues, and I doubt that I have $5 invested in it.
Next I pulled an old 220 watt (rated), computer power supply from the junkbox and found the 12V line is rated well in excess of the heater current draw of the ST-35. It turned out to be rather easy to add an adjustment to the output to bring it up to 12.6 volts.
I was pleased to find that not only is the output voltage very stable, but the noise level is low. It’s been in use, “lighting up” my power amplifier for over 2 years with no issues, and I doubt that I have $5 invested in it.
Attachments
What would the adjustment be?
I also use Computer PSU for my 12AL8 Headphone amp. I just use the +12VDC as it is. No problem so far.
I've used lm22679 switching regulators to build filament supplies, and was able to get the hum down to a level I cannot hear, with DHT's. They save a lot of space, and power! The 22679 has a soft start, too. Switches at 500kHz, well above audio.
a forum member made boards for similar circuits:
Neurochrome.com : : Audio : Universal Filament Regulator
Computer PSU's are usually pretty noise, but sounds like they're working for some people!
a forum member made boards for similar circuits:
Neurochrome.com : : Audio : Universal Filament Regulator
Computer PSU's are usually pretty noise, but sounds like they're working for some people!
The actual “adjustment” is made by a “trimmer” pot. It’s not easy to explain exactly how to add this, since each SMPS is slightly different, although the basic layout is similar for all. I’ve modified 4 or 5 of them, and each is one unique. Nearly all use a controller chip which monitors the output voltages. The basic idea is to fool the chip into seeing a slightly different voltage than is actually appearing at the output.
From my experience, older, rather than newer computer power supplies are easier to adapt to other voltages, since newer ones use “higher tech” ICs that operate with fewer discreet parts.
There is a great deal of information available on the web about SMPS, and how to modify them for specific purposes. You would do well to study some of this material, and do some experimenting. Always be careful as lethal voltages and currents are present in these supplies.
It depends on the type of SMPS as to how much you can adjust the voltage.
LLC SMPS wont adjust much as the voltage is more due to the transformer winding ratio.
With fly back SMPS you can adjust the voltage more.
LLC SMPS wont adjust much as the voltage is more due to the transformer winding ratio.
With fly back SMPS you can adjust the voltage more.
So it's a matter of changing the voltage divider ratio so that the controller keeps the Vref constant at the output you need?
- Status
- Not open for further replies.