Help with this active eq section...Peavey Raxx

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Help with this active eq section...Peavey Raxx

Postby J-fish » 25 Jun 2015, 11:04

Hello, first post here, but I've been reading many, many topics in this forum.
I'm asking if you can help me understanding the active eq section of this old Peavey preamp, the Raxx, version for bass...I thought that it could be interesting for some DIY projects maybe.
There are 3 controls, "bottom", "body" and "edge", which are basically bass, mid and treble....as you can see from the schematic, they are those 3 pots just after the "post-gain" pot (the master volume).
I really don't understand how to calculate the central frequencies of boost/cut for each control of this active eq section...from some readings here and there, they should be shelving type for bass and treble, and notch for the mids control...

http://www.steamingaudio.myzen.co.uk/do ... ircuit.pdf

Can you help me?
Thank you very much in advance, and sorry for my English...!
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Re: Help with this active eq section...Peavey Raxx

Postby phatt » 26 Jun 2015, 12:43

Raxx-Trebcurve.jpg
Raxx-Midcurve.jpg
Raxx-Basscurve.jpg
I'd say you just have 2 tone circuits, the first is passive guitar tone tree the second is some kind of semi active baxandall /James tree in the feedback loop of last triode. Unlike the first tone section this one has gain. (better minds may have more to add)

Good idea to have 2 tone circuits,,,,
Shame you can't split the two tone circuits and insert other stuff between those two.
I've been using 2 tone circuits for years, works a treat. :thumbsup
Hope that helps a bit,,Phil.
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For this message the author phatt has received thanks: 3
deltafred (26 Jun 2015, 16:27), J-fish (28 Jun 2015, 14:18), modman (29 Jun 2015, 10:54)
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Re: Help with this active eq section...Peavey Raxx

Postby J-fish » 28 Jun 2015, 14:18

Thank you A LOT man!!! Very, very helpful!! Perfect job!! :applause: :applause:
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