LTPZen, Zen with long tailed pair input stage

[Allen Newby]

Inspired by the Zen series of A class amplifiers designed by Nelson Pass, LTPZen substitutes the source follower of Zen Variations 4 for a long tailed pair. LTPZen is an amplifier with a bit more open loop gain, a bit more feedback, an extended frequency response and reduced distortion. At first sight, the circuit looks more complicated, but the component count is similar and it is still only a two stage design. The additional complexities lie outside the signal paths. A balanced supply eliminates the loudspeaker decoupling capacitors and the number of remaining signal path capacitors have been reduced to a minimum.


For further details visit www.pmeweb.co.uk/audio

Details are available as a pdf download LTPZen.pdf

Anyone else tried anything like this?

[Blues]

It looks like the mini-Aleph without the output CCS feedback (also called Aleph CCS).

[Nelson Pass]

Of course what that closely resembles is an Aleph J.

[juma]

Hi Allen,
nice contribution to Zen/Aleph story !

Please check the -20V and GND labels on schematic.
Labeled as it is, there is substantial DC voltage present on the speaker.

[Allen Newby]

Thanks Juma,

I will correct the circuit diagram on the web page.

[Allen Newby]

I have corrected the web page. The schematic shown at the start of the thread is now correct.

[Zen Mod]

nice:
I like variations you made ,especially with current sources here and there;

regarding output CCS modulation,I always think that Papa's way of modulating it from output sense have also something with back EMF and all this stuff............
I already talked several months ago with my handy SS consigliero Oly about that.......and seems that he take my ramblings (about EMF) seriously......

Papa,care to put one liner in answer?

[Nelson Pass]

Actually I missed the fact that the current source was constant
on the schematic.

I think the effect of modulating the current source (using output
current to the load as the factor) is not particularly aimed at
back emf, but is intended to reduce the work of the Common-
Source gain stage. To this end it reduces distortion and/or the
bias current requirements in general.

[Zen Mod]

Tnx ,as always ......

[Blues]

That Aleph CCS is really something special...it's what makes an Aleph sound dynamic and reach the peaks without prematurely clipping. It's what makes it sound bigger than a 30W amp, in the case of the A3/30...it helps out when your speakers dip below your normal 8R impedance.