Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Ed_Chambley on April 12, 2016, 12:27:08 pm
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I am restoring a newer radio, a zenith console from 1949. Since this one's cabinet was beyond repair and refinish, I have reworked it and added some nice veneers and it will have a contemporary look when finished.
I want to add a 3.5mm female adapter for using a Bluetooth device or headphone out on a lot of the devices we have today. I would prefer to use the phono stage of the circuit since the amp is on and is isolated from the Radio. I just do not know if it will distort. The Dual Cobramatic Turntable has an on off switch and that is why I was considering using the phono stage.
The schematic attached is slightly different as in 49 they changed the output tube to 6V6, but all the preamp is the same. I have recapped and changed the resistors to metal film. Now she is very quiet and sounds nice.
Probably a much simpler way and I am open to suggestions.
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Top side of the volume control is a good place to start. Use a coupling cap.
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Top side of the volume control is a good place to start. Use a coupling cap.
+1; Sluckey posted while I typed. Top of the Volume control is the only place to go.
The Phono socket has other stuff attached to assist operation of the record player originally intended for connection.
The 6T8 triode is the only audio gain stage prior to the output tube. But it's grid-leak biased, and you probably need the volume control anyway to turn-down the headphone output of another device.
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Thanks guys, already tried it and it is working. Now to install it correctly. I have been in radio land for a few months, but I have a new guitar amp I am planning.