Jens Rasmussen Leach clone group buy

[BobEllis]

OK, Tony you missed me. I see the connections of which you speak and that if you cascode the VAS, you must also cascode the predriver as it sets the operating point of the VAS cascode.

Perhaps Professor Leach was referring to the predriver, driver and power stage collectively as the output stage (all three stages of the triple Darlington).

What Jens's circuit allows is connecting just a standard Low TIM style output stage to the cascoded predriver/driver stage. As in low TIM, you take the drive from either side of R51 (J1J5 and J1J8), feedback connects to J1J6//J1J7. Is there any reason that would not work?

[Tony]

Bob, no reason for that not to work......as i said, you can get rid of T12A and T22A and jumper their ce and you are go....

[lesherons]

Bob - Just to confirm what is on the wiki site: Is the 8 device cascode output listed meant to be the same as the original Leach Amp (8 transistors total per channel)? I have seen Jens' schematic using 8 pairs (16 outputs). Regards, ---HK

[BobEllis]

nope - I meant to say 8 complimentary pairs. I'll fix that. anything cascoded is a super leach.

The original Leach output Jens is offering is 10 devices (5 pairs)

[rob3262]

Originally posted by BobEllis

I've also edited the Leach WIKI to reflect the options that Jens proposed.

- bump -
Bob, it appears that the wiki still hasn't been updated by many of those who had likely signed up for the 10 transistor PCB prior to the edit. Safe to assume that the quantity should be the same as that of the Front End boards?

- Rob

[BobEllis]

I figured with new front end options folks would choose the output stage they preferred. Doesn't seem like too many have bothered.

Please update the wiki to reflect YOUR choice of output board style

Of course we're not in a terrible rush as design isn't finished and we haven't tested a prototype yet.

[Cobra2]

We just have to read thru 10 pages to find the difference...
-or you could make a small summary at the wiki-page?

Arne K

[BobEllis]

Sure Arne, I'll do a blurb.

I thought the headers were fairly descriptive Standard Leach 10 O/P device, 16 device cascoded Super leach style or (possibly) a 4 device cascoded low power stage.

[Carl_Huff]

Please humor me, but I can be thick ...

When I looked at the WIKI it was obvious to me to what the output columns meant. I signed up (I hope!) for 2 plus 4 boards. However the 'Front End' column made no sense to me. What is that first column about?

Best Regards,
Carl Huff

[loek]

The header in the wiki suggest FETS as output device:
"The options are:

Standard Leach - just like a detached version of the last buy. Positions for 5 N channel and 5 P channel devices

Super Leach - Jens' version of the super leach output with 4 complimentary pairs of cascoded devices - 8 n channel and 8 P chanel, 16 total devices."
Maybe simply NPN and PNP will clear this.
Regards, Loek