Directly Heat Triode Filament Supply Issues

In a DHT the cathode is also the filament so both heating current and signal voltages are present. Common perceptions : AC=good but noisy, DC=quiet but cold sounding and has glare

What is needed :

    1. low noise heating current (ie low ripple and no high frequency hash)
    2. no intermodulation between signal and heating current
    3. no audio signal loss through heating current device

The solution is DIYHS filament modules. Read on...