I'm reading DC coupling in tube based guitar amplifiers and how avoiding capacitors in the signal chain reduces signal loss, phase distortion, and noise introduction from the resistors that also have to be brought in.

The topic is fascinating, but there's an upper limitation on how many times one can DC Couple gain stages, mainly to due to the maximum cathode-heater voltage. Most tubes are 100v, others are 180v.

The heaters on tubes don't care if they're ran by DC or AC (AC is probably better if the filaments are in series).

If my initial power source is 24vdc, is there a prebuilt module that can kick out 12.6vac/vdc, or 6.3vac/vdc at high amperage? Everything I'm finding is like $100+. It seems like if you have a sine wave generator drive a transformer, one could make a simple DC-AC isolated converter. It seems like an idea so simple, but I cannot find anything like this, so I'm wondering if there's a specific term I need to be searching for, or if there's a design I could use to build my own.


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    \$\begingroup\$ You're looking for an "inverter", but usually they're used to generate much higher voltages. \$\endgroup\$ – Ignacio Vazquez-Abrams Sep 3 '16 at 22:27

It will probably be easier to find a suitable isolated DC-DC converter than a DC-AC type if you want to supply tube heaters.

An isolated DC-DC converter has no electrical connection between the input and output sides, so you can bias each heater supply to suit the tube's cathode voltage.

A non-isolated converter has a direct connection between the input and output grounds so would not be suitable for this application.

  • \$\begingroup\$ I found a few, but nothing affordable (aka cheaper than a big piece of iron). If you have any leads or knowledge on DC-DC converters, it would need to be 6.3v and be able to supply 300ma for the preamp tubes and 1.5amps for the output tubes \$\endgroup\$ – Jonathan S. Fisher Sep 6 '16 at 14:12

Since you need to come up with the plate voltages anyway, maybe it would be easier to turn the 24VDC into 120VAC or 240VAC via a small inverter and use a conventional transformer to get the filament voltages.

If you have trouble finding an inverter that works from 24VDC, it's easy to find modules that convert 24VDC to 12VDC.


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