Pro's and Cons to DC regulated Filiment Heaters

[boldaslove6789]

I now this has been discussed here before but as I'm getting ready to build a ((Stereo)) D-lator I was forum browsing and noticed that a few pro's round here have used DC regulated Heater supplies.

I had just planned on using a 12v trafo into a voltage divider with 7805 regulator to get what I needed voltage wise.

Who's done this and other than the obvious reducing signal to noise ratio, what are your experiences with this method and is it worth doing?

[ayan]

Greg, I retrofitted this in a couple of my D-lator clones -- cause I had the parts, the time, and was bored. I found no benefit whatsoever. I would say adding a choke, if you don't have one, is time better spent.

Cheers,

Gil

I now this has been discussed here before but as I'm getting ready to build a ((Stereo)) D-lator I was forum browsing and noticed that a few pro's round here have used DC regulated Heater supplies.

I had just planned on using a 12v trafo into a voltage divider with 7805 regulator to get what I needed voltage wise.

Who's done this and other than the obvious reducing signal to noise ratio, what are your experiences with this method and is it worth doing?

[ecisthebest]

i have 6vDC heaters on my dumblator. the transformer came with 6.3vAC filament taps, and I had them wired to the heaters in AC before, elevated by about 30v. I didn't have messy wiring or anything, but it hummed pretty bad. changed it a little, now using DC heaters and it is very quiet. I also do not have to worry about twisting the wires anymore (i still do).

if you have 12v taps on your transformer, you should definitely use an LM7812 and wire it in 12vDC. that is, nothing on pin9, and 12v on pin4, 0v on pin5. you can use a bridge rectifier for that and a 1000~4700uF cap on the input of the regulator, then a smaller cap (it could be as big) at the output going to the tube. you should be able to find a decent sized 16v one for this. if you want a smaller cap or have only a 6.3v heater tap on your transformer, use a schottky diode, 1N5817 to drop less voltage and use a LM7806. this way you can use a smaller 10v capacitor to fit in tight spots, and 1N5817 keeps the voltage drop low so the LM7806 has a workable input voltage.

if something is getting heater hum, and just elevating the heaters isn't helping, then using DC heaters wouldnt be a bad idea.

[bluesfendermanblues]

I have only used DC heating in higher gain amps (like soldano preamp designs etc) and it really help reducing hum levels in those designs, but I never found it to be nessisary in a D-amps nor D-lators.

So if you have hum issues using a d'lator, maybe you should track down ground loops, prior to installing DC heating.

FWIW, Modern Highend HIFI tube power amps, use DC heating throughout. Have recently converted a friends Dynavox (Dynaco ST70 knockoff) from PCB to hardwiring with better components and from reading Hifi mags and looking at HiFI schemos, we realised that all the serious amp designs like e.g. Audio Research and Mcintosh, use DC heating - also on powertubes!. So we also used DC heating and now its silent and humfree, even when you put your ear close to his efficient speakers.

[Structo]

Yes, in my limited experience, humming in the Dumbleator is usually because of ground loops.

I recently re-housed my D'lator and I used isolated jacks this time.

When I had originally built it, I had a bad ground loop and had to cut the shield on one of the shielded cable runs.

This time with the isolated jacks it was dead quiet.

I also used a choke in my build.

[ayan]

Ditto to everything that was said here. Hum in a Dumbleator was, in my case, caused by following Dumble's practice of using non isolated jacks. Switching to Cliffs, back in 1999, solved the problem and I never looked back. I have used 12V with the filaments in series, 6 V with the filaments in parallel, AC and DC (regulated), etc. None of that seemed to make any difference. Added a choke later and I think that bought me a pinch more quietness. One other thing that could make a difference in a Dumbleator is the coupling cap orientation.

Gil

Yes, in my limited experience, humming in the Dumbleator is usually because of ground loops.

I recently re-housed my D'lator and I used isolated jacks this time.

When I had originally built it, I had a bad ground loop and had to cut the shield on one of the shielded cable runs.

This time with the isolated jacks it was dead quiet.

I also used a choke in my build.

[boldaslove6789]

Thanks guys!

Well the only reason I was considering this method is because the flatpak trafo's I'm using don't have 6.3v taps for heater so I'm forced to use a seprate heater supply.

This is what I ended up with:

230v flat Pak wired in Parallel will give Approx. 117v, into a Voltage doubler with 2 paralleled string for each board for B+.

Using the 24v trafo wired in Parallel will give me the 12v into the Regulator to get the 6.3 DCv

Using a circuit I lifted from the Valve Wizard page.

(The Diodes in the DC supply are 1N4148, the rest are 1N4007)

The 7805 Regulator has to be in a Heat Sink also.

The MJ2500 is optional

[ayan]

Just curious: if you want to operate at 6V, why not use a 6V regulator?

Cheers,

Gil

Thanks guys!

Well the only reason I was considering this method is because the flatpak trafo's I'm using don't have 6.3v taps for heater so I'm forced to use a seprate heater supply.

This is what I ended up with:

(The Diodes in the DC supply are 1N4148, the rest are 1N4007)

The 7812 Regulator has to be in a Heat Sink also.

[boldaslove6789]

Sorry mislabeled, its a 7805.

[ayan]

Sorry mislabeled, its a 7805.

[bluesfendermanblues]

Just curious about why you want stereo in/stereo out in the first place?

Are you going to use (a switch into) Two preamps => stereo dlator=>two poweramps?

[boldaslove6789]

Just curious about why you want stereo in/stereo out in the first place?

Are you going to use (a switch into) Two preamps => stereo dlator=>two poweramps?

Yes its for a friend that needs to buffer two loops for two Seperate amps.

[vibratoking]

Ah, so it's not really stereo. Stereo generally means a sound reproduction system that surrounds the listener and gives the effect that different sources are in different locations.

It's really just a dual Dumbleator, correct?

[husky]

Just curious about why you want stereo in/stereo out in the first place?

Are you going to use (a switch into) Two preamps => stereo dlator=>two poweramps?

Yes its for a friend that needs to buffer two loops for two Seperate amps.

Might want to think about iso transformers to avoid ground loops, looks like you will have a lot of mixing of grounds using two amps.
Or separate all the grounds for each section.

[tictac]

Also if your PT is rated for AC current a DC supply will draw more current. You'll need to up the current capacity about 50% above the AC current draw.

Example: if you have a 1A current load at 6V you can use a PT rated at 6V/1A AC or 6V/1.5A for a DC supply...

just a thought...

TT