Hi Preamp,
I think that what you are measuring is the injected current that is flowing through R1 (load) and into the output of the LM3886.
I think that what you are measuring is the injected current that is flowing through R1 (load) and into the output of the LM3886.
Mark W,
you might be right
That tells me there are at least three here that don't know what that plot with unlabelled axes is supposed to be telling us.
you might be right
That tells me there are at least three here that don't know what that plot with unlabelled axes is supposed to be telling us.
I for one unterstand well what Preamp is showing us, and he explained it very well.
If he injects the error current source into point A no much difference, result swamped by speaker wire. But when injecting into point B the wiring of the preamp GND determines whether the voltage drop induced by this current is inside (green) or outside (red) the feedback loop.
If he injects the error current source into point A no much difference, result swamped by speaker wire. But when injecting into point B the wiring of the preamp GND determines whether the voltage drop induced by this current is inside (green) or outside (red) the feedback loop.
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No, that's not the case. Have a look at the attached plot, it shows the current through R1. This current comes out of the LM. Maybe you can try it for yourself, attached the sim file, too.
Attachments
While this current path does exist, its impedance is several orders of magnitude higher than the main path, so it's contribution to the voltage drop accross the load is neglegible. The voltage drop along the main path is important is it is an input signal not corrected by feedback. The amp operates in inverting mode for this error signal.
Thanks for the file.
The injected current is negative and that is why you see a positive output current.
I measure 6.3 mA through R1 leaving 993.7 mA through the ground return.
This is close to what you might expect from paralleled 8.05 and 0.05 Ohm network.
You're right. The currents through the load R1 and the ground return R17 add up to exactly 1A, so they must be coming from the stimulus. Which leads to the conclusion that the simulation is flawed. Any ideas how to circumvent this?
Don't use a load. Then this error current is minimal (reduce to current through feedback network).
That's true. Somehow the voltage "across the load" (across the speaker wire with no load connected in this case) remains unaffected of this and the graphs still look the same. Which in turn would mean that the sim is valid again...? 😕
Did this single side version ever come up ? Does anyone have the Gerbers/eagle or pdf files for this layout?
I believe this is Russ White's final single sided board.
View attachment monobloc_rev_c_copper.pdf
View attachment monobloc_rev_c_silk.pdf
View attachment monobloc_rev_c_copper.pdf
View attachment monobloc_rev_c_silk.pdf
Thanks @Naaling. I went through this entire thread and some others as well. What happened to the double sided PCBs from Russ White? Did he ever publish those ? or only the single sided design is available ?
Is there any better double sided design files available online? while I wrote my previous post, I have found interest in many of my friends to build my_ref rev c. So, I am not looking for Fremen edition but interested in getting PCBs made and do a group buy.
Please let me know of any other good PCB design available for fabrication for my_ref rev C.
I can't answer your question but I can say I built 4 of Brian's kits and they are in use daily and sound terrific!
Ok. I cant find those anywhere. Can you point me to where I can buy them ?
Or is it the chipamp.com kits ? I see that site is already closed.
I think Brian's kits were sold by Twisted Pair using a PCB designed by Russ White.
Russ made his design freely available for DIY use here
My "audiophile" LM3886 approach
(post#3037)
Can you open the files in eagle, and then do a "save as" to a more recent format?
I had a pair of these boards in storage. Put all on site and must shipped out.
But there has been development in this circuit. The Fremen Edition has some fine tuning that gives an big improvement in stability and measurements.
If building for use, try tracking a pair of these. The BOM is listed in Group Buy.
But there has been development in this circuit. The Fremen Edition has some fine tuning that gives an big improvement in stability and measurements.
If building for use, try tracking a pair of these. The BOM is listed in Group Buy.
blackh0le has already stated that he is not interested in the Fremen edition.
By the way, I wasn't aware the Rev C had stability problems!