1 Watt Single-Ended Output Stage

[Thoriated Tungsten]

Guys,

Try designing a classic output amp while using regular power tubes run at reduced voltages yet regular output impedance. PP 6V6 run at 100V anode/g2 into 8k looks interesting, about 0.5 W output power. Cathodes run at +5.0V via 2x 330 ohm cathode resistors. Resting plate current 15mA per tube. Reduce DC HT supply voltage as much as required if this is still too much power.

Also the perceived loudness of the different frequencies may account for the 'lifelessness' of low power amps. You need increased bass and treble to make music sound natural at low perceived volume, something old tube radios usually take into consideration in the design. This may also explain why the reactive power attenuators are popular, as the designs I have seen precisely enhances bass and treble. Thus low volume may require a completely different tone control circuit, compared to your usual classic tone stack.

Edit: Corrected estimated output power.

[Gnobuddy]

You need increased bass and treble to make music sound natural at low perceived volume, something old tube radios usually take into consideration in the design.

I came to the same conclusion, the Fletcher-Munson effect becomes very significant when the volume is turned down very low.

I think there is also an evolutionary/emotional component at work. If you've ever been near a lion when it roared, you will know how powerful the emotional impact of a loud sound can be. For a second, you stop being a human being, and instead simply become terrified food on the lion's menu. If you recorded that roar and played it back at kitten-miaow SPL levels, it simply would not have the same psychological impact.

I think one of the reasons why millions of people have damaged their hearing by listening to stupid-loud music, is this powerful emotional component that goes with loudness. Loud music draws you in and gets you emotionally involved. Whether good or bad, it cannot be ignored. (This might also explain why so many loud bands had successful careers making really lousy music. )

This may also explain why the reactive power attenuators are popular, as the designs I have seen precisely enhances bass and treble.

Now that is interesting, and may explain the obsession with boosted bass response. As for treble boost, you get that anyway from a high-Z amp driving voice coil inductance - so the question becomes, do the reactive attenuators increase that boost beyond what you'd normally get from a high-Z valve amp output impedance?

The best-sounding DIY attenuators I've come up with, all involve a graphic EQ. The simplest is an 8 ohm resistor dummy load, a voltage divider across it to get the signal down to line level, a graphic EQ to shape the frequency response, and clean, full-range flat-frequency solid state amplification & speaker after that.

I've also used an active DI box, fed by the guitar amp's speaker level signal. The rest of the chain is the same as before, i.e. graphic EQ, followed by flat, clean solid-state amplification and speaker. The DI box provides ground isolation, converts the unbalanced signal to balanced, and also provides signal attenuation via a couple of built-in pads.

In either case, to my ears, the graphic EQ plays a significant role, as it lets you shape the frequency response until it has some life to it, even at low SPL. IMO that's a lot more versatile than fixed L-C-R filtering built into an overpriced reactive speaker attenuator.

-Gnobuddy

[Chuck H]

If you've ever been near a lion when it roared, you will know how powerful the emotional impact of a loud sound can be. For a second, you stop being a human being, and instead simply become terrified food on the lion's menu. If you recorded that roar and played it back at kitten-miaow SPL levels, it simply would not have the same psychological impact.

I'm experiencing analogy envy