livingnote

BPEQ - Barry Porter's NetEQ
« on: June 20, 2010, 03:43:50 PM »
[finally BP with positive news attached]

Hi guys,

so it's not the first time I'm getting asked to do the BPEQ, Barry Porter's NetEQ, and
now that I'm ahead of all my etchery stuff I have a whole week to get it nailed right.

History so far has been that I did a complete redraw of the board Barry made from his
Gerbers, as it stood he had basically had the design and then just did "a board", stating
that it was just a quick "get it so that it works" and "if anybody wants to improve it..."

So here I am and now that rerouting is done, solder pads are bigger, no hairline traces
etc., it's getting to nitty gritty details like - certain caps are 0.1 when they could be 0.1
and 0.2 footprints...yada...yada "generally make it highly DIY-able".

Now to get myself warmed up, at the same time I've been thinking of making a guitar
EQ to just "have one", so what better to test it on than captain Solo.

I went and reduced the schematic down to two bands and simple I/O and of course now
it gets tossed into the lab to get torn asunder (I mean, commented).

Interesting things I've noticed:

All caps are bipolar and the signal path ones are often huge (1000µ) - sense in that?

Input and output circuit are serious weaponry it would seem, if I read this right it's
the hunt for the last bit of CM at the input and at the output making it rock-solid
every which way, which is a principle that seems to go through the entire design.

Yeah...so now I'm off doing all the research and reading up, this thing just doesn't
stop fascinating me. I never knew him but wish I could have spoken to him when he
was still alive. I guess the best thing he could do was leave his work like this, in a
manner that is accessible for this here little DIY rat.

It's giving me a whole new mindset about putting serious design documents online
myself - like, you know - the Little Beast? What if I get hit by a car tomorrow?

Who will have anything from all the work I put into it since my first little tin-can
SSL compressor? Maybe I should post that thing as a complete build document
when I'm done. It came from the forum, after all...it should go back to the forum.

Or is the lurking sharktank just what it is and better be sane+careful?

Anyway, </digression>

Here is the schematic I did for the simplified unbal "guitar" version (values just blind for now):

Foolin' Around
« Last Edit: June 20, 2010, 03:53:27 PM by livingnote »
Quote from: emrr
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Matthew Jacobs

Re: BPEQ - Barry Porter's NetEQ
« Reply #1 on: June 20, 2010, 04:14:45 PM »
Hi Livingnote.

Funny thing I was looking into this EQ over the last couple of days. I think it would make a killer EQ for mastering and I was going to try and build one as well using DOAs and stepped rotary switches.

Have you thought about providing the pinout option for 2025 type op-amps on you board?

I was thinking of a supper DIY PCB with both DOA and IC option, Input / Output transformer option, even switchable IC / Iron input/output, true bypass, lead spacing for various caps, etc....

While studying the schematic I was was fascinated at how Barry Porter engineered the relay switching. I have never seen it done like this before. Could you maybe explain to me why it is done this way and what are the benefits?

I wish you all the best with this project and I hope it can bring honor to its creator... RIP Barry Porter.

J

Harpo

Re: BPEQ - Barry Porter's NetEQ
« Reply #2 on: June 20, 2010, 04:21:32 PM »
For a high impedance guitar input, the 1st stage non inverting and leaving out the last inverting buffer might do better than the assumed high value resistors for R1 and R2.
A +/-6V supply with your 7812 and ground at half supply looks a little on the low side with non rail2rail NE5532s. As always YMMV.
A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.  -Douglas Adams

livingnote

Re: BPEQ - Barry Porter's NetEQ
« Reply #3 on: June 20, 2010, 04:37:28 PM »
Aha - yeah, I had seen the whole DOA thing going on in the other threads about it...here's
where I am (got to that point and then came "stuff"):

Quote from: emrr
F-in' hook some Sh*t up and see if it catches on fire

My Stuff: Livingnote's META

livingnote

Re: BPEQ - Barry Porter's NetEQ
« Reply #4 on: June 20, 2010, 04:47:36 PM »
>>I was thinking of a supper DIY PCB with both DOA and IC option, Input / Output transformer option, even switchable IC / Iron input/output, true bypass, lead spacing for various caps, etc....

Well there certainly is more room in a 19" than that board is big ;) Like Doc said..."If you put your mind to it..."

Check one for sure true relay bypass, lead spacing for various caps - iron isn't the issue either, and DOA...but hey, like...DOA's on everything or just input/output, or what was the general idea there?

Me - same here...no end to my fascination. I've seen relay driver transistors before but apart from digital interfacing am a little stumped myself what why here this one?

Yeah, hear ya, Harpo - non Rail2Rail is kinda crummy in 2010. You know of any good ones that don't cost an arm and a leg, and possibly have survived as a PDIP?
« Last Edit: June 20, 2010, 05:03:39 PM by livingnote »
Quote from: emrr
F-in' hook some Sh*t up and see if it catches on fire

My Stuff: Livingnote's META

boji

Re: BPEQ - Barry Porter's NetEQ
« Reply #5 on: June 20, 2010, 08:48:12 PM »
If Living note was ever asked to design a scene in the new TRON movie it would totally be pornographic. Curves baby. Curves.

http://www.youtube.com/watch?v=1AwvuirSEAA&feature=related

« Last Edit: June 20, 2010, 09:07:53 PM by boji »

Matthew Jacobs

Re: BPEQ - Barry Porter's NetEQ
« Reply #6 on: June 20, 2010, 09:01:25 PM »
If Living note was ever asked to design a scene in the new TRON movie it would totally be pornographic. Curves baby. Curves.

http://www.youtube.com/watch?v=1AwvuirSEAA&feature=related


Ha ha ha... it's funny cause it's so true......  ;D

boji

Re: BPEQ - Barry Porter's NetEQ
« Reply #7 on: June 20, 2010, 09:16:19 PM »
I couldn't resist.

Re: BPEQ - Barry Porter's NetEQ
« Reply #8 on: June 20, 2010, 09:20:32 PM »
New Tron movie!!??  :o Jesus, where have i been?

Hey livingnote, can you do up one of these too? Say after the eq is done?  ;D

http://www.imdb.com/media/rm88641024/tt1104001
« Last Edit: June 20, 2010, 09:27:58 PM by desol »

Denyle Guitars

Re: BPEQ - Barry Porter's NetEQ
« Reply #9 on: June 20, 2010, 09:38:10 PM »
I couldn't resist.


I wanted to say something about how it could never compare to the original but now I just want to bump that. ;)

I like her as a blond in Bickford Shmeckler's Cool Ideas
« Last Edit: June 20, 2010, 09:46:59 PM by Denyle Guitars »


livingnote

Re: BPEQ - Barry Porter's NetEQ
« Reply #10 on: June 21, 2010, 08:03:28 AM »
Funny, I used to be way into 3d and building cities and stuff...like:



Quote from: emrr
F-in' hook some Sh*t up and see if it catches on fire

My Stuff: Livingnote's META

Harpo

Re: BPEQ - Barry Porter's NetEQ
« Reply #11 on: June 21, 2010, 08:27:11 AM »
Yeah, hear ya, Harpo - non Rail2Rail is kinda crummy in 2010. You know of any good ones that don't cost an arm and a leg, and possibly have survived as a PDIP?
Sorry no, and I probably wouldn't design around a part not common availiable. Probably only my personal thing of disliking any potentially showstoppers, for whatever reason only breaking at night/weekends/soundcheck.
This EQ can be boosted to 10dB per band. With a hot pickup (active bass maybe 1.4Vpk) you'd need a voltage swing of at least +/-4.5Vpk. Easiest approach seems to me, upping the supply voltage from 12V to a more common 18V or 2x9V batteries in series, or even higher. For a low impedance source and at this cost, a 5532 is hard to beat. For higher impedance of a passive pickup I'd go for a maybe single OPA132 or dual OPA2132 if you want to keep your actual layout, coming with FET input, higher slew rate, enough GBW, asking a little less/comparable quiescent current. I see no obvious need for it to drive less than 2k load in the 1st stage. If anything goes wrong, a TL07x could keep you going. Clamping the input between rails might make it a bit safer.
Do you plan to use these unobtainable center tapped pots for boost/cut or a toggleswitch for boost/off/cut with standard halve value pots ?
A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.  -Douglas Adams

livingnote

Re: BPEQ - Barry Porter's NetEQ
« Reply #12 on: June 21, 2010, 11:39:17 AM »
Well I was thinking for the guitar version here might as well just go with switching
for simplicity, but if there's a studio something then obtaining the unobtainable
might be possible...but certainly not on some standardized layout that only accepts
one type, more like pin headers for that one...

Yeah - bumping it up to higher V from supply would be a good thing in general,
I was basically only going for gadget anyway and designed with just standard dual
opamp footprints - but yeah, same experience here, the less obtainable, the less
fun in general...
Quote from: emrr
F-in' hook some Sh*t up and see if it catches on fire

My Stuff: Livingnote's META

livingnote

Re: BPEQ - Barry Porter's NetEQ
« Reply #13 on: June 25, 2010, 04:26:18 AM »
As goes for the pots with middle tap: Not really worth it considering the low obtainability,
makes more sense in general to do a relay switched Cut/Boost switch, and also to disconnect
the shelving filters from the bell curve pots so that it becomes feasible to do a stereo unit
with quad pots.
Quote from: emrr
F-in' hook some Sh*t up and see if it catches on fire

My Stuff: Livingnote's META


 

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