Tube amp for my car

[wa2ise]

As mentioned above, another approach for getting some tube sound in the car would be to use a tube buffer stage ahead of a SS amp. And the tube buffer built using say subminiature tubes intended for fighter jets or guided missile service. Say a pair of triodes in cathode follower connections. And you may be able to take apart an inverter to get at the high voltage DC before it's chopped into square wave AC, to get the B+ for the tubes.

[ctc17]

Originally Posted by wa2ise

As mentioned above, another approach for getting some tube sound in the car would be to use a tube buffer stage ahead of a SS amp. And the tube buffer built using say subminiature tubes intended for fighter jets or guided missile service. Say a pair of triodes in cathode follower connections. And you may be able to take apart an inverter to get at the high voltage DC before it's chopped into square wave AC, to get the B+ for the tubes.

I was thinking of that but with a 12AX7 type tube. I had not though of opening the inverter and removing the chopper fets. Brilliant!
All you need to do is ad the 2nd and 4th order harmonics to give it the tube sound.
I saw an ipod docking station with a 12AX7 preamp with the same intention.

[wa2ise]

Originally Posted by ctc17

I was thinking of that but with a 12AX7 type tube.

There's the 6112 twin triode submini tube, somewhat similar to a 12AX7. With a reasonable mu around 70 IIRC. It's a 6.3V heater tube, but use a pair and build an SRPP circuit, and the heaters in series to run them off the 12V car power. With wire leads you could just solder into the circuit, so no tube getting loose issues, and it's designed for mobile work.

I had not though of opening the inverter and removing the chopper fets. Brilliant!

thanks.

All you need to do is ad the 2nd and 4th order harmonics to give it the tube sound.

That's the ticket.

[N2IXK]

Originally Posted by wa2ise

And you may be able to take apart an inverter to get at the high voltage DC before it's chopped into square wave AC, to get the B+ for the tubes.

Are you thinking of a switchmode AC-DC power supply? Every 12V-120VAC inverter I have seen does the primary side switching at 12V, and the AC voltage is just stepped up using a transformer. No high voltage DC available.

[wa2ise]

Originally Posted by N2IXK

Are you thinking of a switchmode AC-DC power supply?

More modern, and smaller ones, look to be switchmode DC to DC converters running somewhere around 30KHz or higher, with subsequent choppers to make it look like 60Hz AC squarewave. Assuming that the DC-DC conversion has no DC path between its primary and secondary, or if the negative end of the secondary side is tied to the input 12VDC, you can use it for B+ ahead of the 60Hz chopper ckts. You may need additional filtering to get rid of switching crud off this B+.

If you have an inverter that runs at 60Hz 12V to a 60Hz transformer, and the secondary is isolated, just feed it into a bridge rectifier and filter caps to get the B+.