Filtering Between Gain Stages - BSIAB and other Q's

[aziltz]

Would anyone take a shot at explaining the filtering/gain control between the two mu-amp stages of the BSIAB to me?  I can simulate the frequency response and understand that, but I'm trying to figure out the reason behind putting in this kind of filtering.  Seems like it cuts bass mostly.  I'm just a little puzzled when I compare it to the filtering in a TS that really only concentrates from the mids on up...

http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=39075&g2_serialNumber=2

I'm referring to the 22nF --> 470K/470pF --> A500k/150pF  network.

I came across this because I was trying to create a simple op-amp clipping circuit by chaining two op-amp stages together, and I was getting very low gain sounds that would buzz.  Drive was adjusted in one of the feedback loops.  I rewired it, inserting the filter/gain section from between the mu-amp stages of the BSIAB and I got a nice, low to mid-gain sound with a lot of highs.  It needs to be edited a little bit but I'm basically trying to figure out the reasoning behind this sort of filtering.

From what I gather we have 4 things creating the clipping/gain here,

Gain stage -->> Filters -->> Gain Pot -->> Gain Stage.

Is it two much bass that causes buzzy clipping?  Are we attenuating bass because those notes get the most boost from a gain stage?  Any thought's here would really help me understand these cascaded gain stages.

[aron]

Read this page, especially the "secret of stacked stages"

http://www.diystompboxes.com/wiki/index.php?title=Simplemods#Simple.2C_Easy_Mods.2FTips_.26_Techniques

[aziltz]

Read this page, especially the "secret of stacked stages"

http://www.diystompboxes.com/wiki/index.php?title=Simplemods#Simple.2C_Easy_Mods.2FTips_.26_Techniques

thanks aron, i forgot about that page... i have a bookmark somewhere.

[John Lyons]

The 470p/470k is a treble boost as used in marshall amps etc.
The 500K/150p is is a teble bypass cap, so when you turn down
the gain the tone does not get as dark. It says similar to the tone with the
gain up. The 150p cap passes treble (byapsses the gain
pot) when the pot is turned down. With the pot turned up
beyond halfway the cap has no effect.

John