diytube.com

Is it better than a traditional long tailed pair? I've been doing tronola's from http://www.tronola.com/html/st-70_mods.html
And he's talking about adding a AC balance pot, R61A, inbetween the anode resistors of the LTP to decrease distortion. Would a LM334Z not need a AC balance pot? and would it have as much distorion as a traditional LTP?

The LM334Z works well in an AC-coupled long tail, i.e. I've measure a great improvement in THD. Most of the performance increase in the AC-coupled LM334Z solo config comes from the extra B+ voltage (and larger plate resistors) more than balance improvements.

You can also cascode it with a DN2540 or 10M45S and just replace the 18K long tail resistor and continue with DC coupling. Google "CCS and long tail". As to the improvements with a LM334Z/DN2540 dropped in to replace the 18K resistor, I cannot say. I'll experiment with this shortly as I'm building up a 100W KT120 Eiclone.

Shannon

It appears that the "preamp" stage must be capacitor coupled to the LTP. DC coupling and the voltage will be too high on the cathodes of the LTP and overvoltage the LM334Z, correct?

I've got one side wired up like in the Eico ST-70 mod, and the other I'm going to use a LM334Z and compare.

tomlang wrote:It appears that the "preamp" stage must be capacitor coupled to the LTP. DC coupling and the voltage will be too high on the cathodes of the LTP and overvoltage the LM334Z, correct?

Yep. Taj at diyaudio uses a 10M45S as a ccs with a 1K on the grid?, and a 330 ohm and a 500 ohm pot on the cathode. The 10M45S is 450 volts 10ma and 40 watts.

Look at post 420

Also this thread.