EAR 825 EQ-Dont quite understand......?

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V

valvusmusicus

Active member
Joined
Jan 24, 2011
Messages
41
Hi all
I understand the EQ part of the circuit-but not sure how it is implemented into the circuit-this is basically a pultec network is it not? Why are the transformers neccessary? are the middle 3 triodes and associated components a discrete op-amp? Ive been trying to work out how it works (with my limited knowledgfe) but....alas!!

anyone help-I would love to build this-as from reading posts, it seems to be very different to other topolies about ???
 
Without a schematic no one will likely have a clue as to how to answer your questions . . .
 
lassoharp said:
Without a schematic no one will likely have a clue as to how to answer your questions . . .
Click to expand...

here ya go

Ear_825_EQ.GIF
 
Not at all pultec-like or passive - it's a simple boost/cut L/C gyrator circuit halfway inside the feedback loop of an amplifier.

More or less like a standard 1980's car-radio graphic eq, but with a tube amplifier.

parmet1.gif


http://4.bp.blogspot.com/_FdGFE8NBDgc/TCb9RaaqLRI/AAAAAAAADm8/Z8fWHTxw6gA/s1600/Ten-Band_Equalizer_Circuit_Diagram.GIF
http://farm6.static.flickr.com/5206/5278034584_9a51733691_b.jpg

Jakob E.
 
Aaaah!!.the mists are clearing!! I see now what you mean-just confused by the complexity of the EAR schematic.
hanks to all who replied :)
 
Thansk Lassohar et al-sorted now-will go ahead and build my own version, and hopwfully post pics when done-
 
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Any ideas on suitable iron for this?

I'm guessing step down on the input and a similar step up on the output.

Looks like there's feedback taps on the interstage and output transformers.

Mark
 
Hi All,

I'm trying to reduce the gain range on an 825Q from 12dB to +/- 6dB boost and cut. Looking at the circuit, would I just double the 620ohm summing resistors R1, R8, R5, R7, R9 in that circuit?
 

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