Re: Battery bias directly to grid



bruce seifried wrote:

> In article <4353775E.5B755A29@xxxxxxxxxxxxxxxxxx>,
> Patrick Turner <info@xxxxxxxxxxxxxxxxxx> wrote:
>
> > But the transients you speak of don't occur any more than with any other
> > biasing method.
> >
> > Patrick Turner.
> >
>
> With the Dact 20K input attenuator, and a +2.4 volt dc source connected
> to its wiper, you will see something on the order of a few tens of
> millivolts being generated when changing the gain setting at the low end
> of the attenuator. Feeding this to the input of a dc-coupled power amp
> will give you low level, audible transients. Not a deal breaker, but not
> good design practice.
>
> Switching the attenuator from its lowest gain setting to off, or vice
> versa, will give you a 2.4 volt step signal into your input. I would
> call this a rather large transient, and not especially good for the
> health of any speaker attached.
>
> -bruce seifried

I don't understand how switching gain settings changes the tube bias;
there is always -2.4V at the grid regardless of the gain setting.
The only chance of transients being generated by gain level change is if the
input
grid draws dc current and a small dc voltage exists across the resistances
of the DACT, so that when switching, you hear the switch steps.
I have heard this in amps with a DACT. But its a tiny effect compared to
music transients.

Patrick Turner.


.

Relevant Pages

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  • Re: Battery bias directly to grid
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