ruffrecords said:
Now that quite a few people have Universal EQ PCBs in their hands ...
I really want to do this awesome project justice by building an EQ with it!
The Uni-EQ is crazy flexible, so to make it possible to answer my questions my project is to take a few sections and combine them to create an EQ that has various controls for various bands and functions attempting to minimize the interaction between the bands and functions.
I now understand that the PCB has 6 unconnected building blocks (plus a pad for constructing a bypass switch). ( and rereading the posts with that knowledge some of the posts make much more sense to me). I think I can make an EQ from it but I have some questions (please forgive the names I have given things, and that some questions are more conceptual than implementation specific):
1) It seems like each section can be an attenuator EQ by itself (with the possible addition of a 10K load to ground at it's start, like is done in the "In-A" section), is that right?
2) It seems like when combining sections there are three types to consider: The "In-A" section, the "B-C" sections and D sections. Does that make sense?
3) Regarding choosing parallel or series to combine sections: I see why the In-A can't be parallel to any other section because it passes all frequencies unattenuated and selectively attenuates so it would function as a bypass. But I am curious as to whether it matters if it is the first stage in the EQ? (it has the 10K input load resistor so clearly it is most convenient for it to be first but as a concept could it be anywhere in series?)
4) I understand from your post that all the B-C sections can be paralleled, is that correct? And that to avoid interactions they should operate in different bands, but I am interested in the interaction we are avoiding. Is it that they might partially bypass each other if they shared frequency bands?
5) The D sections seem sort of special. If I use Both D sections, I should connect E1 to E2 to create a combined section, but either D section can also stand alone. And in all cases, the D section is connected in series with the rest of the EQ? Is that right?
6) Conceptually again could the D section be anywhere in the series of stages in an EQ?
7) (reupdated) Is there any guidance as to how much resistance or attenuation occurs in each series sections? I understand from the Inductance calculations document that some of these form a voltage divider with an output load resistor, but where is that load resistor? I assume that a standalone shunting section would also act as a voltage divider?
Eight) Practically, if I connect:
A, B1, B2, and B3 together.
C1, C2, C3, D1 and D2 together.
E1 to E2 together.
And I populate everything with reasonable values keeping the B-C sections in different bands. And I connect in the bypass and pad sections somehow. And I add some sort of makeup gain, connectors, power, pots and parts. Would then I have an EQ that would do Hi Shelf, Lo Shelf, Low Cut, Lo Boost, Hi, Low and Mid boost? Would this have so much attenuation that noise would be a problem, or is the problem just a place to put all the knobs and switches?
Pultec kept the MEQ separate from the EQP-1, I always assumed it was a noise issue... but maybe it was marketing or space issue.
