APEMAN said:Yes there are changes in the schematic, I think there is at least one big change in CH3 preamp.
The very early amps sound different!
APEMAN said:Bankim said:So....... Which one should be there n which one shouldnt?
Hey Bankim, please be cool and let your soldering iron cold until we know more Could be the case, that further revisions of the schematic between the two known from 2009 and 2010 exist - the tone stack update could have been done earlier than you think. What we know is that there have been at least two updates to the power supply, mute and switching in the <#12XX range. Mesa put out a service manual for technicans to procede some updates to those amps to garantee stable performance.
To your question, the standard version should contain the 82k Restistor R218.
Cheers
IronSean said:Weird, part of this change also seems to be maybe running counter to what they said about the internal volume control:
In the top circuit there's 386 KOhm in the top and 570 KOhm on the bottom, which reads like 7.5-7.75ish on the Volume knob on an audio taper pot (which I'm assuming volume was?)
In the update, it's 550 KOhm over 430 KOhm, or like 6.9-7ish on the internal Volume. Which doesn't sound like much, but on a log taper pot between 6 and 9 is the range of 30-90% of the resistance.
So when the manual reads that the internal volume is set to 7.75, it looks like after this tweak it's actually more like 7 on the dot. Because so much range of resistance exists between 7 and 8 as well, that's probably why the originals were so sensitive in that "magic range".
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