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[zmix]

24-96 Mastering wrote on Wed, 21 January 2009 15:44

I'm getting a TFPro P9 for testing in a couple of days. Reading this thread, I'm starting to think I'll be dancing to yesteryear's groove. To anyone who was used both designs, how are they related, sound-wise? How do they differ?

Very different.  The "Barry Porter EQ" is based on a common "State Variable Filter", which is  a textbook 'multimode'  filter designed around 4 opamp stages per filter capable of simultanous HP, LP, BP and notch outputs.  If the notch output is not required, it can be built with 3 opamp stages per filter.   The filter is a second order design (12dB/oct).  

The TF Pro P9 is an RLC EQ based on Barry Porter's original Trident A-Range design.  Each midrange filter is comprised of a capacitor / inductor combination and a discrete amplifier stage. The High and Low sheving bands have a gentle first order (6dB/oct) response.


The difference in use between the "Barry Porter EQ" and the TFPro P9  is the difference between "thinking" and "feeling"... respectively  (EDIT for Terry -see below).


YMMV

[compasspnt]

Which is which?

Manual?

[yeloocproducer]

Anyone in LA build one?  I'd love to hear one as well...

[livingstone]

hi !
i'm curious to know what kind of ICs have you choosed to build your BP eq ?

[Greg Reierson]

livingstone wrote on Sun, 25 January 2009 12:29

hi ! i'm curious to know what kind of ICs have you choosed to build your BP eq ?

I can't speak for Brad, though I think I'm using the same opamps that Frank used in his EQ.

The master cut/boost are LME49710s, the output is an ADA 797, the integrators and shelf buffers are OPA 134s and the rest are 5534s.

GR

[compasspnt]

They are not balanced I/O, by the way.

[Viitalahde]

I feel like going towards discrete I/O, especially when a bunch of Forssell JFET992's will be freed from my old EQ when the BPEQ is done.

Unfortunately, they really need higher voltage rails to operate at their best. I'm currently loving them @ +/-24v, but I'm thinking I could try +/-22v for the BPEQ. This would keep a few doors open for nice IC's to use for the filters - such as 5534, LME49870 and some others. AD797 I couldn't try, which is a pity.

Of course I could power up the I/O at +/-24v and the rest at +/-15v, but it seems like a little bit of a hassle.