• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

6V6 line preamp

Thanks 👍

Can you tell me the right value for Rf used? And if there is the Cbyp too...
In the final mod I inserted a hum breaker resistor of a few OHMs between the cathode local ground and the main (power) ground tight to the biggest capacitor of the filter,
 
For NFB attached Salas original schematic.

Buon lavoro, Enjoy it.
 

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  • 6V6 Salas G3X schematic NFB X10.jpg
    6V6 Salas G3X schematic NFB X10.jpg
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I'm currently experimenting with a 6V6 preamp. I'm using the Neurochrome Maida regulator board, pricey but I can't build my own and it sounds great. I also just tried the feedback version above and wow, what a difference. It kicks the sound up several notches and takes it from an okay DIY preamp to a very competitive preamp. ;-)
 
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In that case, here's what I'm working on! ;-) Breadboarded right now. The Salas feedback version. Power supply is 275-0-275 > UF4007 > 100uF > Neurochrome Maida board > 10uF. Simple DC filament supply. That big toroid will either have to be shielded or moved to a separate box. Thinking of switching to an EI tranny which doesn't interfere so much with the circuit. Otherwise, with the Maida regulator, it's dead quiet, and at 40mA it will be enough to use the chassis as a heat sink. I'm not experienced with low-level signal designs like preamps or phono amps so I'm learning as I go, but it sounds fantastic. So far I like it better than my octal Aikido, and I like my octal Aikido a lot. ;-)

1E66580C-E52F-4F35-B13B-DE12A8946732.jpeg
 
In that case, here's what I'm working on! ;-) Breadboarded right now. The Salas feedback version. Power supply is 275-0-275 > UF4007 > 100uF > Neurochrome Maida board > 10uF. Simple DC filament supply. That big toroid will either have to be shielded or moved to a separate box. Thinking of switching to an EI tranny which doesn't interfere so much with the circuit. Otherwise, with the Maida regulator, it's dead quiet, and at 40mA it will be enough to use the chassis as a heat sink. I'm not experienced with low-level signal designs like preamps or phono amps so I'm learning as I go, but it sounds fantastic. So far I like it better than my octal Aikido, and I like my octal Aikido a lot. ;-)

View attachment 1153136
Congrats for the build. What about the SQ of the Fostex output coupling caps?