Hi-End 50W Push-Amplifier inspired to AudioResearch

[audiodesign]

see on:

PP2010 - Hi-End Push Pull Amplifier

50W 0.3% Thd with only 5dB of global feedback

[radiostar]

Interesting project and nice site!

[audiodesign]

In a direct comparation with my last reference GM70/813 single ended amplifier this push-pull in some case give a better sound.

The bass is more fast and present.

The middle with voice are very clear.

[richwalters]

Nothing new under the sun.
Your'e gonna need global nfb for bass reflex loaded speakers with a Q higher than 1.5 and listening to classics. The article doesn't mention the damping factor value.
The unloaded low end damping will sound much too honky. The split loaded phasesplitter works excellent for a minimal component count. The only slight disadvantage is zero gain.
department of physics
richy

[Tekko]

And i´ve heard from ppl that UL doesent sound as good as triode connected of just tieing the screen grids to the plate supply via a resistor.

[Wavebourn]

Originally Posted by richwalters

Your'e gonna need global nfb for bass reflex loaded speakers with a Q higher than 1.5 and listening to classics. The article doesn't mention the damping factor value.

Did not you see feedback to cathodes from output tranny?

[thoriated]

In a design where introducing a solid state current source to a long tailed differential pair is being looked at, why not consider the high voltage negative supply? It is easily implemented from a preexisting FW rectified positive ground referenced supply with a second bridge rectifier, pair of capacitors and a relatively small CLC or similar filter. Plus you get a fixed bias supply source for free.

I am also curious how much is really gained performance-wise by adding a solid state differential input.

[audiodesign]

Richy,
here you can see the test informations for the damping

PP2010 - Push Pull test

[audiodesign]

Thoriated,
use a resistor in the differential with A 100v ac is impossible.

the min value to get 2 simmetric output is 220K/270k

so we need 2mA * 220K = 440V

[thoriated]

Hi -

Well, I used a long tailed diff pair cathode resistor to -500Vdc for my DC coupled OTL so that is the sole source of coloration for that portion of the circuit. I also added a small neon bulb to ground to keep the off state cathode voltage from going too far negative, but it has worked flawlessly for over 20 years.