DC heaters-The good, the bad and the ugly

[Ed_Chambley]

I was wondering why DC heaters are not used often in Guitar amps, but is common practice in HiFi?  I converted one of my amps and the only noticeable difference is there is less noise all around.  What are the drawbacks, if any, other than the additional parts needed?  Why is this not a common practice in guitar amp builds?

[sluckey]

IMO it's 95% about money and a 5% benefit. And the hifi crowd does not mind giving it up for purity sake. But who wants to waste all that money on a lo-fi guitar amp? I can think of a few!

[stratele52]

I build some guitar amps from scratch and from my desing , not kit . My amps are always very quiet. I try for fun DC heater and this don't bring less noise . So I keep heater in AC.

[HotBluePlates]

I was wondering why DC heaters are not used often in Guitar amps, but is common practice in HiFi?

Hi-Fi also includes phono preamps, which can have signal levels that are only 20% as big as a guitar signal. D.C. heaters in those are probably a very good idea.

[Ed_Chambley]

IMO it's 95% about money and a 5% benefit. And the hifi crowd does not mind giving it up for purity sake. But who wants to waste all that money on a lo-fi guitar amp? I can think of a few!

I must have not done it correctly because it did not cost much at all.
I used the original Hoffman amp schematic, which was DC.  I must be missing something, but I do have proper voltage and the amp is running fine.  I have heard that there is really no benefit in a guitar amp, but there is.  It really cleans up the lead dress on the heater wires.

I can think of a few who will "waste all that money" as well as I resemble that remark.

[sluckey]

There is a benefit to high gain amps that are prone to high noise, buzz, hum, etc. But an amp such as a Fender AB763 will have very little real world benefit compared to proper AC filament wiring. You could probably measure the improvement. Hearing an improvement may be more difficult. I know I could not hear a difference.

I've chased a couple hum problems before and actually ran the filaments from a battery to help isolate the hum source. The battery test did not eliminate my particular hum.

[phsyconoodler]

I built a really high gain 5 watt amp and it was quite hummy so I was considering DC heaters but then after  bit of investigation I found that I needed a better pi filtering system.It's very quiet now,no DC heaters in sight.
  At extreme gain settings there is some hiss but I used carbon film plate resistors and that is likely the source or at least part of it.
  I have worked on many amps that have DC preamp heaters and they aren't dead quiet either,so it's debateable whether they are the bees knees or not.

[Ed_Chambley]

I built a really high gain 5 watt amp and it was quite hummy so I was considering DC heaters but then after  bit of investigation I found that I needed a better pi filtering system.It's very quiet now,no DC heaters in sight.
  At extreme gain settings there is some hiss but I used carbon film plate resistors and that is likely the source or at least part of it.
  I have worked on many amps that have DC preamp heaters and they aren't dead quiet either,so it's debateable whether they are the bees knees or not.

I agree, it is just something I wanted to do.  I did it to my 18 watt TMB with cathode bias pair of EL34's.  This amp is very high gain and doesn't do anything clean.  I noticed a significant reduction in floor noise and even more when using OD pedals.  The amp will never be quiet like an AB763.

[tubeswell]

If you're using octal pre-amp tubes or tubes that are single triodes (where the tubes don't have the hum-cancelling arrangement going on with the filament that noval dual-triodes have), then a DC heater supply can be of some benefit.

[John]

I'm using 6SL7 for preamp (mostly to be different) and so far I found that using a humdinger along with elevating the ground works pretty well too. At some point I'd like to try the DC just to see, though.

[stratele52]

I'm using 6SL7 for preamp (mostly to be different) and so far I found that using a humdinger along with elevating the ground works pretty well too. At some point I'd like to try the DC just to see, though.

Yes, it is very good to see by yourself .