Bottlehead Forum

General Category => Technical topics => Topic started by: reglys on April 09, 2022, 03:21:36 PM

Title: Preamp Headphone
Post by: reglys on April 09, 2022, 03:21:36 PM

Hi

If we forget the 6.3 Vac voltage needed for the tube heaters, would it be possible to get enough DC voltage for the output tubes by rectifying 120 Vac powerline without a power transformer in a headphone preamp for instance.

Thank you in advance 

Title: Re: Preamp Headphone
Post by: Paul Joppa on April 09, 2022, 05:09:10 PM

This is universally accepted as an unsafe practice. It's like removing the brakes on a car to save weight.

Title: Re: Preamp Headphone
Post by: Doc B. on April 11, 2022, 08:14:23 AM

They used to make radios like that in the 30s and 40s. They were called widowmakers for reason.

Title: Re: Preamp Headphone
Post by: Thermioniclife on April 11, 2022, 12:06:39 PM

Yeah. also called curtain burners. Many old tube radios have a built in resistance in the power cord that if replaced with a modern cord disaster is sure to happen. Also they were designed for 110 Vac.

Title: Re: Preamp Headphone
Post by: reglys on April 11, 2022, 12:26:04 PM

Yes I understand at that time they had plug with 2 prongs and they didn't care about the polarity and you could have a hot chassis.

However it is amazing when we see what Apple is doing with their tiny IPAD power supply . First time I used it in Paris, France during an oversea trip, I was sure this tiny power supply will blow out at 230 Vac.

Title: Re: Preamp Headphone
Post by: Paul Birkeland on April 11, 2022, 12:31:13 PM

You could certainly use a 6V wall wart to power your heaters.