TH Custom 3 Band Parametric EQ

zippofan

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Started this build today and realized I got the wrong pots for Q and Frequency, ugh. Thankfully I found a drill template, it's not going to be a blast drilling lol.

Parametric board.jpg

I have built a couple of TH Custom's boards including their version of the ROG Supreaux overdrive, and their mono pedal size amp, both are cool. I didn't realize it initially, but there's an SMD bridge rectifier on the opposite side of the board. I didn't have a lot of trouble soldering it like I thought I would, but it's also a lot larger than an SMD transistor.

I haven't played with a parametric EQ since I was in college and we had a rack mount Ashly in our radio station production studio, it should be fun.
 

Theorage

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Looks like a worthy project! Hopefully you will get a quiet circuit, as it makes for the ultimate tone-shaper after a guitar -- so much versatility! Tell us how it works out for you when completed.
 

zippofan

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Looks like a worthy project! Hopefully you will get a quiet circuit, as it makes for the ultimate tone-shaper after a guitar -- so much versatility! Tell us how it works out for you when completed.
I will for sure! The pots I ordered should be arriving this week, the main challenge then is drilling the enclosure. I think this beats anything else I've built for sheer number of controls (except the Aion Lab Series preamp, I used their pre-drilled enclosure for that).
 

PhredE

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Cool stuff.

Is this link to the source the correct one? https://diy.thcustom.com/shop/product/eq/

Is that passive or does it require external power? (just wondering).

IIRC, the older Yamaha G series (G50-112, G100-112, etc) sported a true 3-way parametric EQ section. I loved that. You could really tweak the tone stack and get a really terrific range of sounds out of those.
 

zippofan

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Cool stuff.

Is this link to the source the correct one? https://diy.thcustom.com/shop/product/eq/

Is that passive or does it require external power? (just wondering).

IIRC, the older Yamaha G series (G50-112, G100-112, etc) sported a true 3-way parametric EQ section. I loved that. You could really tweak the tone stack and get a really terrific range of sounds out of those.

Yes, this is the PCB:
https://diy.thcustom.com/shop/3-band-parametriq-eq-full-control-pcb/

It's a 9V supply, with a charge pump to double the internal voltage. I decided to use different pots for the Q and frequency center controls, the plans call for the type without the threaded collars and I thought there might be more opportunities to cover drilling errors with the same type as the level controls. I'm not that good and don't have a drill press!
The pots should be here this week, if I get a chance today I'll start drilling. But I also got some more Madbean 1590A boards in yesterday, including a Rat, Big Muff and a Fat Boost, and some LM308 cans coming from a fellow member here (thank you very much FL!) I'm very tempted to stuff the Rat board first :)
 

zippofan

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This one has been moving slowly, I wired it up yesterday and went to test today. Nothing, nada, hmmm. I wasn't sure about the one SMD on the board, a bridge rectifier. (I know, why for DC? It is taking the place of a reverse protection diode) I had a 50/50 chance of installing it correctly, and at the time I figured I did. Nope lol.
Now it's working, time for a decal!

EQ assembly.jpg

Here's the flip side, the bridge is right above the red/black DC wiring.

Parametric board top.jpg
 

zippofan

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It seems like I've been building this pedal for months! Hopefully the decal dries properly and then final assembly. Pretty cool circuit, it deserves a lot of messing around time to get the most out of it.
eq decal.jpg
 

zippofan

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Another EQ from TH Custom, this a 5 band using rotary pots instead of sliders. Quick and easy build so far:

eq in progress.jpg eq pcb.jpg
It uses a Rohm Semiconductor BA3812L audio filter chip, two cap values for each of 5 bands so you can change your center frequency. It also can be chained for a 10 band EQ, pretty cool. The chip is obsolete (of course) but I see them online, I just bought the chip when I ordered the board, less than $3.
Here the Datasheet

The drill template is OK, but measure twice! I scratched the enclosure when drilling, but I won't be able to decal it for a few months.
 

zippofan

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Forgot I didn't have 5 white knobs! Ah well, I had to order parts for the next two 1590A's, so some time next week though it won't get a decal until April at the earliest.

EQ guts complete.jpg EQ complete.jpg

I used a two color LED for this, red is off, blue is on. Works just dandy, this was one of the fastest builds I've done, probably 4 hours start to finish including drilling.
 

zippofan

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Did the decal for the five band EQ during a short spell in halfway decent weather. Once the lacquer dries I can reassemble and put it in my chain.

5band Decal.jpg
This was a quick and easy build and it sounds good too. The only drawback is we're used to graphic EQ's like MXR's (which I have on my pedal board), but it does the same thing.
 




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