X100 backengineered here - Page 33

GRollins · 29th August 2005, 12:57 AM

Warmed up. You'll find that they drift a fair amount when the amp is just turned on, but after twenty or thirty minutes or so, you'll get pretty stable values.
The absolute value isn't really all that important unless you intend to run the amp near full power. The relative offset is the one to watch out for. Parts matching is your first line of defense. Then the circuit embellishments to fine tune things.
Around this point, someone frequently pops up asking about using a servo. Yes, it can be done. No, it's not necessary to go to those lengths.

Grey

mastertech · 29th August 2005, 01:58 AM

GRollins
"The relative offset is the one to watch out for. Parts matching is your first line of defense. Then the circuit embellishments to fine tune things"

thats what ive said, if you aim for high precision match! and use
high precision components, high quality is the number 1 factor
here

if you cant attain these matches in components just follow
the 5 ways mr Pass has talked about

Mr pass thank you for the links

GRollins · 29th August 2005, 03:27 AM

The other things are in addition to matched components, not instead of.

Grey

mastertech · 30th August 2005, 01:19 AM

in addition?well i guess mr pass is on to something big
good luck

Villaw · 6th September 2005, 01:36 PM

Petter

I would be very much interested to have a look at your last design of the x100 since Nelson doesn't mind about it.
Another thing though, using 12 pairs of fets for 100w per channel is indeed an overkill unless you plan to go up to 600w with the same circuit?

B.L. · 8th September 2005, 08:01 AM

Nelson wrote: "...so on the X350 we used a current mirror for a level shifter."

Could anyone explain how to do it on X100?

Nelson Pass · 9th September 2005, 07:04 PM

Quote:

Originally posted by B.L.
Nelson wrote: "...so on the X350 we used a current mirror for a level shifter."

Could anyone explain how to do it on X100?

Well, you know what a current mirror is - there are plenty of
examples on this site. You source a certain amount of current
into it and you get a certain proportional amount out. The
ratio between input and output are arbitrary, and when the
ratio is unity, it's a level shifter.

zinsula · 9th September 2005, 07:57 PM

Uhmm, could be something like this?

The frontend in this thread is single ended, so I drew it this way. Could also be complementary I guess.

Not sure if it would work.
But it's more a conceptual schematic anyway. All this resistor values guessing...

Ciao, Tino

Nelson Pass · 9th September 2005, 08:17 PM

Yes, that would be an example.

Brian Donaldson · 9th September 2005, 09:43 PM

Now that's a cool use of the current mirror.

6th September 2005, 01:36 PM	#325
Villaw diyAudio Member Join Date: Feb 2005 Location: Ni	Petter I would be very much interested to have a look at your last design of the x100 since Nelson doesn't mind about it. Another thing though, using 12 pairs of fets for 100w per channel is indeed an overkill unless you plan to go up to 600w with the same circuit? __________________ Nick

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29th August 2005, 12:57 AM	#321
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	Warmed up. You'll find that they drift a fair amount when the amp is just turned on, but after twenty or thirty minutes or so, you'll get pretty stable values. The absolute value isn't really all that important unless you intend to run the amp near full power. The relative offset is the one to watch out for. Parts matching is your first line of defense. Then the circuit embellishments to fine tune things. Around this point, someone frequently pops up asking about using a servo. Yes, it can be done. No, it's not necessary to go to those lengths. Grey

29th August 2005, 01:58 AM	#322
mastertech Banned Join Date: Mar 2005 Location: Australia	GRollins "The relative offset is the one to watch out for. Parts matching is your first line of defense. Then the circuit embellishments to fine tune things" thats what ive said, if you aim for high precision match! and use high precision components, high quality is the number 1 factor here if you cant attain these matches in components just follow the 5 ways mr Pass has talked about Mr pass thank you for the links

29th August 2005, 03:27 AM	#323
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	The other things are in addition to matched components, not instead of. Grey

30th August 2005, 01:19 AM	#324
mastertech Banned Join Date: Mar 2005 Location: Australia	in addition?well i guess mr pass is on to something big good luck

8th September 2005, 08:01 AM	#326
B.L. diyAudio Member Join Date: Apr 2003 Location: Nysa-Poland	Nelson wrote: "...so on the X350 we used a current mirror for a level shifter." Could anyone explain how to do it on X100?

9th September 2005, 08:17 PM	#329
Nelson Pass The one and only Join Date: Mar 2001	Yes, that would be an example.

9th September 2005, 09:43 PM	#330
Brian Donaldson diyAudio Member Join Date: Jan 2003 Location: Texas, Love it or leave it	Now that's a cool use of the current mirror.