Pooge,
I just reread the original webpage - it turns out that you are right.... It seems that the resistors are there to isolate the VAS from any cap to gnd on the long wires.
I have however not had problems with stability on the amps I have build. I know I have only made and tested 6 channels, but I think I would have seen oscillations if anything was present.
\Jens
I just reread the original webpage - it turns out that you are right.... It seems that the resistors are there to isolate the VAS from any cap to gnd on the long wires.
I have however not had problems with stability on the amps I have build. I know I have only made and tested 6 channels, but I think I would have seen oscillations if anything was present.
\Jens
Would you care to teach us mere mortals the ways of the force ?
I can "barely" calculate some values only using Ohm's and Kirchoff's laws but advices from experienced people would be mostly welcomed.
I know a universal formula is not practical but something rather empirical may be usefull.
Best wishes,
Jonny
I can "barely" calculate some values only using Ohm's and Kirchoff's laws but advices from experienced people would be mostly welcomed.
I know a universal formula is not practical but something rather empirical may be usefull.
Best wishes,
Jonny
Re: I doubt Leach would have specified a resistor where a jumper
Not necessary here. If used, it could be used as a lead to the diode board, and the other resistor reduced.
Another possible problem capacitance could be paracitic capacitance to the ground plane. I think I read somewher about pulling the ground plane back from the VAS transistor to avoid this. Hopefully, that is not a problem, or if it is, one that is easily correctable by adjustment of the compensation cap.
loek said:
Not necessary here. If used, it could be used as a lead to the diode board, and the other resistor reduced.
Another possible problem capacitance could be paracitic capacitance to the ground plane. I think I read somewher about pulling the ground plane back from the VAS transistor to avoid this. Hopefully, that is not a problem, or if it is, one that is easily correctable by adjustment of the compensation cap.
Re: Zener & R3 (R22) dissipation
the board has component #'s right? Why not use them instead of "LTP tail current" (what's this??) why not identify the R and say "current through R__" or bias through R__
Also, zener??? what about ZD1 or whatever it is in the appropriate spots?
Nice spreadsheet though.
(I get Vrail)
AndrewT said:
the board has component #'s right? Why not use them instead of "LTP tail current" (what's this??) why not identify the R and say "current through R__" or bias through R__
Also, zener??? what about ZD1 or whatever it is in the appropriate spots?
Nice spreadsheet though.
(I get Vrail)
If everybody is going to mess around with different parts, how much documentation is needed for this project. I’d hate to spend a lot of time getting parts lists and a webpage together if most of the builders are going to experiment with alternative parts from day one. Is a schematic and placement plan enough to get people going, or should I take the time at put together a webpage with building information for this PCB?
\Jens
\Jens
Actually there are too many opinions in this case
Personally I believe that anybody could do whatever he want himself. Mr Leach is very clear in his webpage, and always anyone can be helped by this forum. However, with much respect
and appreciation to Jens's time and work, a webpage with building information would be valuable, mostly for the members that they are not professional ee or similar. As for the "experimentation panic" maybe we can leave it for later, at least nobody have a working pcb until now
except Jens of course
Spiros
Personally I believe that anybody could do whatever he want himself. Mr Leach is very clear in his webpage, and always anyone can be helped by this forum. However, with much respectand appreciation to Jens's time and work, a webpage with building information would be valuable, mostly for the members that they are not professional ee or similar. As for the "experimentation panic" maybe we can leave it for later, at least nobody have a working pcb until now
except Jens of course Spiros
I agree. I will build mine on spec first, then play with upgrades and tweaks later.
If the parts list is the same of very similar to the original (with obvious exceptions of output devices), then most of the parts have DigiKey part numbers in Dr Leach's building guide. That might save at least some time in putting together the BOM.
If the parts list is the same of very similar to the original (with obvious exceptions of output devices), then most of the parts have DigiKey part numbers in Dr Leach's building guide. That might save at least some time in putting together the BOM.
Hi Lgreen,
I pulled the component numbers straight off the PDF dated 12-05-2005. Or have I misunderstood the point you are making?
Recently some contributors have asked what power of Zener (D1 & D2) they should use and what power and/or value of feed resistor (R3 & R22). This allows them to check for themselves without having to generate the maths. It is not intended to divert anyone away from the main aim - to build a Leach Clone.
But a justification for it's being would be a change in transformer secondary voltage (recent requests for info this past week) leading to a change in conditions around the Zener controlled bias current and power dissipation in associated components.
Jens,
A recipe would be excellent & I second the thought of right first time.
I pulled the component numbers straight off the PDF dated 12-05-2005. Or have I misunderstood the point you are making?
Recently some contributors have asked what power of Zener (D1 & D2) they should use and what power and/or value of feed resistor (R3 & R22). This allows them to check for themselves without having to generate the maths. It is not intended to divert anyone away from the main aim - to build a Leach Clone.
But a justification for it's being would be a change in transformer secondary voltage (recent requests for info this past week) leading to a change in conditions around the Zener controlled bias current and power dissipation in associated components.
Jens,
A recipe would be excellent & I second the thought of right first time.
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