Re: [EVGRAY] Re: ZOTL audio amplifier

Body

Hi Ole,

   What class would you specify this amplifier?     How would you deal
with the DC offset at the speaker load?   Do you know of any off the
shelf H bridges that would work for this circuit?  I don't think most
bridges are transformer decoupled with the galvanic isolation of this
design.

Thanks for the breakdown!

On 3/7/2019 4:22 AM, [email protected] [EVGRAY] wrote:
>  
>
> Hi Mick,
>
> The H-bridge formed by the transistors (20, 22, 24 and 26) are put in
> series with the voltage supply and the load. The input of the H-bridge
> is modulated by transformer 60 to generate the carrier wave. What is
> the normal AC output of the H-bridge is then loaded or modulated by
> the tube transformer 50. The tube transformer delivers voltage to the
> tube. When the tube loads the tube transformer there is an increase in
> the current through the H-Bridge and the load in series with the
> H-bridge. The result is modulation of the current through the voltage
> supply. The carrier frequency is then amplitude modulated.
>
> Figure 1 has symmetric output by using the circuit of figure 2 in
> push-pull mode where figure 2 is just the positive half of the circuit
> of figure 1.
>
> Regards
> Ole
>
>
>
> ---In [email protected], <mkjekyll@...> wrote :
>
> Ole,
>
> Not sure if you are aware of these but the concept is really great.  I
> just ran across this yesterday so still don't grock the full bandwidth
> of the concept but it seems to have many things going for it as far as
> being able to run a vacuum tube to it's full potential as an amplifier
> and retaining all the transfer characteristics.
>
> It looks as if the output of the tube is converted to DC though so I
> don't get how the design does not incorporate the transfer function of
> the rectifier.
>
> It appears a tube is rectified and the DC control voltage is used to
> modulate a carrier of 250kHz across a switching supply in order to
> impedance match the output of the tube to a speaker allowing the
> inductor to be designed for  single frequency rather than the whole
> audio range.
>