6V6 line preamp

[merlin el mago]

Thank you Salas and Merlin!
Yes, perhaps I should cover the interior walls even further, maybe I will do it little by little by removing some individual parts attached there... Of course yes, I will put the Al tape linked to ground at the end.

The schematic used is this, Merlin...

If you don't need the gain try the NFB version sounds far better. Tried both...

 

[indaco]

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,

 

[merlin el mago]

For NFB attached Salas original schematic.

Buon lavoro, Enjoy it.

 

[Bas Horneman]

Years ago I took apart my Salas 6V6 to rebuild it. The time has come. And now that the forum is speedy again...I can post pics again.

Rectifier tube will go in the center slot.

Think I'll build the G3X version.

 

[merlin el mago]

You will not be disappointed, I tried G3X version with and without NFB and sound far better with NFB.

 

[grovergardner]

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. ;-)

 

[merlin el mago]

Yes NFB version is very very good.

 

[Salas]

Its a well tuned shunt NFB version for the 6V6. It uses just 6dB of feedback and almost only shows second harmonic at 0dBV output level. Easy to convert an existing common cathode build into it too.

 

[Bas Horneman]

Drilling and cutting almost done. After which comes the fun part for me. Soldering. (Would you rather I start a seperate thread Salas?)

 

[merlin el mago]

Well done Bas, I hate drilling & cutting so you aren't alone.

 

[Salas]

Drilling and cutting almost done. After which comes the fun part for me. Soldering. (Would you rather I start a seperate thread Salas?)

Good work in progress. No, this thread is also perfect for 6V6 line preamp individual builds details.

 

[grovergardner]

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. ;-)

 

[Bas Horneman]

50k pot or less for the feedback version right Salas? I have the choice of a noble 50k or dact 10k in my spares.

 

[grovergardner]

Same question here! Those are 20K Penny & Giles on the breadboard (fancy for a breadboard!). I also have some 50K DACTs.

 

[merlin el mago]

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?

 

[merlin el mago]

50k pot or less for the feedback version right Salas? I have the choice of a noble 50k or dact 10k in my spares.

I owned a Noble, good stuff and if it's 50K perfect because it's the value recommend by Salas.

 

[Salas]

Up to 50k says the schematic note, not strictly 50k recommended. Means 10-50k whatever you got in quality you like and your sources are at ease with.

 

[merlin el mago]

Ok good to know, thanks Salas.

 

[Bas Horneman]

Putting it together.

 

[merlin el mago]

Wow what a beauty, congrats Bas.