Posting again about my modular gyrator-EQ project. This project not tested yet, but I made 5 channel EQ with gyrators and 10 channel active filters EQ formerly. Look at older pictures:
EQ with gyrator filter is noiseless, simple, and cheap. Because the first version made for guitars or instruments, the adjustment was too fine for me, the "Q" of separated bands was not permanent, one of the EQ band adjusted another frequencies too. Therefore this method is better for home stereo hi-fi instead of instrument amplifications.
After my first gyrator EQ project I made 10 band active filter EQ by RANE. This EQ have permanent Q, the result is much better for instrument amplification. But 10 channel was too much for me, very hard to set the best sound, because I got too much possibilities. Otherwise the noise of this method is much higher than simplest EQ with gyrator filter, but for instruments was much better for me.
Now I have new (untested at this time) equalizer-projects, with 3 different versions. The first is the modular EQ with gyrator, maybe just for home hi-fi. The second is an
UREI545 clone parametric EQ, the 3rd is the new modular
RANE based permanent Q equalizer. Now I posting about the first type of EQ with noiseless gyrator filers. With current version, I have
module with adjustable gyrator circuit only. I made two versions of PCB: the first
mounted with one stereo adjustable resistor for home stereo systems, the second is
mounted with two mono adjustable resistors for instrument amplification systems to separate left and right channels.
Images:
Stereo gyrator module:
Dual mono gyrator module, the channels (Left, Right) can be adjust separately:
One of the upper modules have to be insert to one of the mainboards.
For 10 bands:
For 5 bands:
To the upper mainboards required one of the gyrator module (stereo or double mono), and module called "power filter" for less noise, and certainly power supply. I have three versions of "
power filer" PCB,
portrait,
landscape, and
something between fat and thin :).
Look at all pictures about modules.
In this project, very important to able to count out the values of capacitors and resistors. Look at examples, links, and expressions:
5 band EQ:
- 100Hz - 330nF
- 300Hz - 100nF
- 1kHz - 33nF
- 3kHz - 10nF
- 10kHz - 3.3nF
The upper values are valid for all of the C(a) capacitors in this schematic:
For 10 band EQ:
- All of the 50k adjustable resistors must be changed to 25k.
- For capacitors and resistors look at the table below:
| Hz | C3 and C1 | C4 and C2 | R3 and R1 | R4 and R2 |
| 31 | 6.8 uF | 100 nF | 470 Ohm | 100 kOhm |
| 63 | 3.3 uF | 47 nF | 390 Ohm | 100 kOhm |
| 125 | 1.5 uF | 33 nF | 390 Ohm | 100 kOhm |
| 250 | 680 nF | 22 nF | 330 Ohm | 82 kOhm |
| 500 | 330 nF | 10 nF | 330 Ohm | 100 kOhm |
| 1k | 150 nF | 4.7 nF | 330 Ohm | 100 kOhm |
| 2k | 100 nF | 2.2 nF | 330 Ohm | 82 kOhm |
| 4k | 56 nF | 1 nF | 390 Ohm | 82 kOhm |
| 8k | 22 nF | 470 pF | 390 Ohm | 82 kOhm |
| 16k | 10 nF | 220 pF | 390 Ohm | 100 kOhm |
Here is the online gyrator calculator:
http://awasteofsalt.com/gyrator/A little math:
Links for several method to get values of parts:
I think its enough if you want simple but very good quality gyrator EQ circuits.
See also:
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