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Old 2nd February 2008, 10:02 PM   #461
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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?
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Old 2nd February 2008, 10:14 PM   #462
AJT is offline AJT  Philippines
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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....
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Old 4th February 2008, 02:27 PM   #463
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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
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Old 4th February 2008, 04:18 PM   #464
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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)
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Old 7th February 2008, 05:39 PM   #465
rob3262 is offline rob3262  United States
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Quote:
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
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Old 7th February 2008, 06:10 PM   #466
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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.
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Old 7th February 2008, 07:13 PM   #467
Cobra2 is offline Cobra2  Norway
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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
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Old 7th February 2008, 08:03 PM   #468
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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.
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Old 8th February 2008, 05:54 AM   #469
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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
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Old 8th February 2008, 11:08 AM   #470
loek is offline loek  Netherlands
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Default output devices

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
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