5-Band Fully Parametric EQ

[jkokura]

That's great! I hope your builds go well too. I look forward to the build report and I'll watch for the board mounted version in the new year (hopefully).

I release you from all pressure here too. When you get to it, get to it. Don't feel anxious about it.

[aziltz]

That's great! I hope your builds go well too. I look forward to the build report and I'll watch for the board mounted version in the new year (hopefully).

I release you from all pressure here too. When you get to it, get to it. Don't feel anxious about it.

Thanks.  I'd do it now but I already bought the regular 16mm pots for two builds, which I have to concentrate on building.

[aziltz]

This was a difficult transfer to make.  I made 4 attempts, hoping to get 2 that were worth salvaging with the pen.  I got one great one.  I think I just need to take my time more.

Are there any tips to minimize air bubbles?  I follow the small bear tutorial for my transfer method.

[gigimarga]

Very nice work! Thanks for it
Can you post a PnP for it?

[aziltz]

I'll post it tonight.  Still don't have capacitor values for all the bands yet.

[aziltz]

Here's the transfer I used.



Layout Names/Values and Schematic are in this Album - http://s132.photobucket.com/albums/q18/aziltz/Parametric%20EQ/

[gigimarga]

Thx a lot man!

[aziltz]

Ok, I've successfully etched a second PCB, and simulated all the bands.

Here are the bands I've chosen, and the upper/lower capacitor values for the gyrators for BASS Guitar.

30-135Hz  .33u/.22u  (C11/C22)

100-450Hz  .1u/.047u  (C3/C4)

250 Hz - 1.125kHz  .047u/.022u   (C5/C6)

710 Hz - 3.2kHz  .01u/.01u  (C9/C10)

2.2kHz - 10 kHz  .0047u/.0022uf  (C13/C14)

Here's a link showing the range at maximum Q and Boost.  I'm planning to change the 2.7k resistors (R3 & R4) to about 10k and limit the maximum Q to 75% of the controls range.

http://s132.photobucket.com/albums/q18/aziltz/Parametric%20EQ/

here's a sample showing lowest, middle and highest frequency range.  remember frequency is heard non-linearly so the response is logarithmic.

[aziltz]

Mockups of the two versions I'm building.

[jkokura]

What size boxes are those, and how have you got them arranged as far as which knob does what? I'm also curious what the second stomp switch, loner knob and hole on the lower picture is?

[aziltz]

What size boxes are those, and how have you got them arranged as far as which knob does what? I'm also curious what the second stomp switch, loner knob and hole on the lower picture is?

These are 1790NS, made by New Sensor/EHX.  I got them drilled from Pedal Parts Plus.  They are a little taller than the 1590BB, and obviously a lot wider.

The Bands and their controls are arranged in columns.

The Top Row, left to Right is Boost/Cut for Bass, Low Mid, Mid, High Mid, and Treble.  I'm using Center Detent Pots here.

The next row down is Frequency Center.  All 5 knobs for the Black one, 3 knobs for the Chrome/Sparkle One.

The bottom row on the Black one is Q.  The Bass/Treble Q controls are internal.  All Q controls on the Chrome/Sparkle are internal.

Input/Outputs trims are on the back.  DC Jack on the Back.  The Black input/output jacks are on the back.  The Chrome/Sparkle input/output jacks are on the side, with the send/return on the back.

I'll take some gut-less shots later tonight to show the layout and clearance.

The extra stomp switch, lone knob and a toggle (not shown) are for a feedback/bypass looper on the Chrome/Sparkle Box.

[jkokura]

freaking fantastic. I can't wait for the final project file to build my own!

[aziltz]

Success!  Built up the first EQ circuit and tweaked a bit to taste.  I'll post a full review of the circuit after I finish both projects.

[aziltz]

[ragtime8922]

This is an awesome project. I take my hat off to you. I love parametric stuff. The only thing that scares me is Q. The general rule is that the higher the Q the shittier the audio. If it were me I'd have the pots set so that minimum Q is ultra low and max Q is a little higher than ultra low.

[aziltz]

This is an awesome project. I take my hat off to you. I love parametric stuff. The only thing that scares me is Q. The general rule is that the higher the Q the sh*ttier the audio. If it were me I'd have the pots set so that minimum Q is ultra low and max Q is a little higher than ultra low.

Well you need a high Q if you want to get manual/stuck wah sounds out of it, and I left that in. (apparently "%^&*ed" wah is no no word)  The Q Trimmers and Pots are 10k, and the useable range is about half.  It can get ultra low, but then you don't get as much boost, unfortunately.

However, you can easily tweak this to give you a smaller and lower range of Q, but with more boosting power per band.  I'll try to outline that when I finish these projects.

[ragtime8922]

This is an awesome project. I take my hat off to you. I love parametric stuff. The only thing that scares me is Q. The general rule is that the higher the Q the sh*ttier the audio. If it were me I'd have the pots set so that minimum Q is ultra low and max Q is a little higher than ultra low.

Well you need a high Q if you want to get manual/stuck wah sounds out of it, and I left that in. (apparently "%^&*ed" wah is no no word)  The Q Trimmers and Pots are 10k, and the useable range is about half.  It can get ultra low, but then you don't get as much boost, unfortunately.

However, you can easily tweak this to give you a smaller and lower range of Q, but with more boosting power per band.  I'll try to outline that when I finish these projects.

True, the wah sounds are a nice option. 10k pots should give a good range. Can't wait for clips!

[jkokura]

I was curious. How big does the board need to be for a three band version? I was thinking about building a 3 band parametric EQ in a 125 box (6 knobs, internal trim pots for Q). Can this schem/board be altered for that use? I'd use it with an acoustic guitar, low, mid, high with boost/cut and Freq controls. I was thinking about using 12mm pots, and in that case I might be able to get the Q controls surface mounted too... 9 knobs and a switch on the top of a 125B? Ambitious maybe.

Anyway. Tell me if you think it's a dumb idea and doable. I've been reading RG's stuff on parametric EQ and trying to understand it. I'm not sure how to go from the reading I've done to the schem to the PCB though.

Jacob

[aziltz]

I was curious. How big does the board need to be for a three band version? I was thinking about building a 3 band parametric EQ in a 125 box (6 knobs, internal trim pots for Q). Can this schem/board be altered for that use? I'd use it with an acoustic guitar, low, mid, high with boost/cut and Freq controls. I was thinking about using 12mm pots, and in that case I might be able to get the Q controls surface mounted too... 9 knobs and a switch on the top of a 125B? Ambitious maybe.

Anyway. Tell me if you think it's a dumb idea and doable. I've been reading RG's stuff on parametric EQ and trying to understand it. I'm not sure how to go from the reading I've done to the schem to the PCB though.

Jacob

To use just 3 Bands of the 5, don't populate the stuff in circled in red.  However, I don't think the board will fit in a 125B.  Over Christmas Break I was planning on redoing it with board mounted pots to hopefully fit the whole thing in a 1590BB sideways.  I can try and make a 3 Band version at the same time that is smaller.

[aziltz]

Here's one.  Gotta finish the other before I leave on break Friday!