Enclosure not stated · 4 knobs
2, 4 & 8 Band Gyrator EQVerified
Based on the 2, 4 & 8 Band Gyrator EQ
- Category
- EQ / Filter
- Controls
- Band A · Band B · Band C · Band D
- Build
- Vero· 16×17· 21 cuts, 11 links
- Layout
- Verified · Tagboard Effects marks it as built and working
- Tags
- EQ
From the post
Moving on from the HM2 which obviously has quite a powerful EQ, I thought I could use the circuit to make a handy standalone EQ. I was going to just use a quad opamp and make this 2 band with 2 of the channels being used as the input buffer and output gain stage, but thought it would still be pretty compact using a dual opamp for the input and output and so settled on 4 bands.
I have included a table showing the example frequencies you can achieve using common component values for R1, C1 and C2, and just altering the value of the R2 resistor. Another option would be using 4 x 10K multi-turn trimmers instead of the R2 resistors so you could vary the frequency for every band and really fine tune it to the gear you're using.
You can use the Excel calculator I posted here to select your own components and get the frequency and Q you want if you prefer to fine tune the bandwidth. I also included a trimmer so you can set to unity precisely, or give a slight boost if you like.
And now everything is modular of course, there's no problem in adding another opamp to give you a further 4 bands.
And the baby of the family
Schematic
This is a board layout, a drawing of where each part goes, and the post may link the schematic it was drawn from. Open the layout at Tagboard Effects. No KiCad fragment has been drawn for this circuit yet.
Parts list 29 rows
Report a wrong parseGot parts in a drawer? See what you can build with them.
Check before you build · 1 value the reader of this layout was not sure of
- R1, C1 and C2 of each band carry no value on the board; the values entered are the ones the example table gives for every row
| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 11 | ||||
| ×2 | 10K | 10k | read from the layout by eye | |
| ×2 | 1M | 1M | read from the layout by eye | |
| ×1 | 3K3 | 3.3k | read from the layout by eye | |
| R1 A | 100K | 100k | from the example component table; read from the layout by eye | |
| R1 B | 100K | 100k | from the example component table; read from the layout by eye | |
| R1 C | 100K | 100k | from the example component table; read from the layout by eye | |
| R1 D | 100K | 100k | from the example component table; read from the layout by eye | |
| R2 A | ? | ? | value not given; sets the band frequency, example table lists 22 ohms to 10K; read from the layout by eye | |
| R2 B | ? | ? | value not given; sets the band frequency, example table lists 22 ohms to 10K; read from the layout by eye | |
| R2 C | ? | ? | value not given; sets the band frequency, example table lists 22 ohms to 10K; read from the layout by eye | |
| R2 D | ? | ? | value not given; sets the band frequency, example table lists 22 ohms to 10K; read from the layout by eye | |
| Capacitors 11 | ||||
| ×1 | 1u | 1u | read from the layout by eye | |
| ×2 | 47u | 47u | electrolytic; read from the layout by eye | |
| ×1 | 10u | 10u | electrolytic; read from the layout by eye | |
| C1 A | 0.1uF | 100n | from the example component table; read from the layout by eye | |
| C1 B | 0.1uF | 100n | from the example component table; read from the layout by eye | |
| C1 C | 0.1uF | 100n | from the example component table; read from the layout by eye | |
| C1 D | 0.1uF | 100n | from the example component table; read from the layout by eye | |
| C2 A | 0.01uF | 10n | from the example component table; read from the layout by eye | |
| C2 B | 0.01uF | 10n | from the example component table; read from the layout by eye | |
| C2 C | 0.01uF | 10n | from the example component table; read from the layout by eye | |
| C2 D | 0.01uF | 10n | from the example component table; read from the layout by eye | |
| ICs 2 | ||||
| IC1 | TL072 | TL072 | TL072 or similar; read from the layout by eye | |
| IC2 | TL074 | TL074 | TL074 or similar; rotated 180 degrees; read from the layout by eye | |
| Potentiometers 4 | ||||
| Band A | B100K | B100k | Potentiometer | read from the layout by eye |
| Band B | B100K | B100k | Potentiometer | read from the layout by eye |
| Band C | B100K | B100k | Potentiometer | read from the layout by eye |
| Band D | B100K | B100k | Potentiometer | read from the layout by eye |
| Trimmers 1 | ||||
| ×1 | 10K | 10k | read from the layout by eye | |