Can a 5687 drive four 813's in triode mode ?

[Fanuc]

Hello,

I was wondering if a 5687 can drive four 813's in triode mode ? I have seen each half section of a 5687 drive a 211 triode, in a paralel 211 SE design. Have heard the 813 is easier to drive.

Or does anyone know of a higher power dual valve like a 5687 where each half section can drive two 813s ?

Crazy project huh? Heater supply's will need a switch mode PSU I reckon!

Help appreciatted

[Fanuc]

On a different note.

Can a high quality NOS 211/VT4C from GE or United outperform a 813 in triode mode easily ?

Advice/Views welcome!

[danFrank]

>Or does anyone know of a higher power dual valve like a 5687 >where each half section can drive two 813s ?

Higher powered dual triodes include: 6BL7, 6BX7, 6SN7, 6CG7.
Most of these are octal based tubes. They ALL sound better than the 5687! The main reason the 5687 is such an "in style" tube is that the Japanese go crazy for it and use it in a lot of their amps.

If you are going spend lots of money to make a triode amp, use actual triodes like the 211. There are also better tubes than the 211 for a triode amp though; like the 845, GM70, etc. The better (more linear) the triode for an amp, the harder it is to drive though. It's always a give and take, like everything else.

>Crazy project huh? Heater supply's will need a switch mode PSU >I reckon!

Stay away from Switching supplies. They make lots of noise that will carry over into the audio path.

99.5 % of commercial tube amps cut MAJOR corners in order to get the cost down of their product. Like using switching supplies, triode connected pentodes, etc.

Ultimately, it depends what you want to do... If you want to make your ultimate dream amp, do it right: Use actual triodes, buy the best Transformers that you can afford, use linear supplies with lots of filter capacity (no electrolytics! Oil or poly caps), AC on the filaments (I will get flamed for that one!), Regulated B+ supplies, etc. There's lot's of things you can do.
If you want to make a good amp that's a whole lot easier to build and get working, make a triode connected 813 amp. Basically it comes down to how much time and money you want to spend before you want to start listening to your amp. Either way you will have a great sounding amp. Tubes are great for audio, period.

>Can a high quality NOS 211/VT4C from GE or United outperform >a 813 in triode mode easily ?

Everything else being equal, the 211 will sound better (better bass response, lower distortion, etc) than the triode connected 813, but it will give you less power. Max power a 211 will give you at 1250 volts B+ will be around 20 watts, and that's with a very beefy driver for the 211. The 813 will give you considerably more power and it can be done with much saner voltages, like 600-750 for B+ and an easier built driver.

And don't listen to the hype of NOS tubes. The 211 and 845 tubes that the Chinese make are good and cost a WHOLE LOT LESS than NOS. They just don't have the long life of NOS.

Have fun and be careful... Daniel