- All Things Yaesu
- Wien Bridge Based Parametric Equaliser
- Parametric Equalizer Design
- Parametric EQ
- Parametric Audio Equalizer
All Things YaesuThis project is based on the parametric equalizer proposed by Elektor in the s and later published in the book "Creations electroniques" in Publisher: Publitronic. Their design involved three stereo potentiometers per channel, which means a lot of cables from the front panel to the circuit board. It's quite tiedous to build and IMHO prone to noise from within the enclosure. To solve these problems and make the unit more compact I have put everything on a single board, potentiometers included. No more cables! A graphic equaliser has only one control per band: the gain. A parametric equaliser has 3 controls: gain, frequency and bandwidth. While a graphic equalizer requires a lot of bands, a parametric equaliser is more acurate and usually only two or three filters are enough. Several modifications were made to allow these improvements. First, it's an all-SMD board: easier and cheaper to build. This is necessary because clearance is limited with the front pannel. More importantly, it is important to realize that several PCBs will be stacked next to each other for the different filtering stages and therefore we have no space to extend the PCB without spacing the potentiometers too. Other modifications were necessary for the values of several components. This was prompted by the decision to use off-the-shelf ALPS stereo potentiometers. This way we only have to buy 10K lin and 10K log pots. The formulas are in the schematic. That means the audio circuit is only ground-referenced, and you should simply choose the supply voltage depending on which op-amp you selected. It can fit comfortably in a 1U unit horizontally or in a 2U unit vertically. PCB interconnection is straightforward: the connections for power and signal are aligned when you place the filters next to each other, hence very short wires or jumpers will suffice. Gerber files are available for those who just want the damn thing ASAP :- External links Bernard Odant used this page to put a parametric equalizer in a standard guitar pedal. Last update: All rights reserved.
Wien Bridge Based Parametric Equaliser
I've written in these pages before about the sometimes-maligned, always-underestimated EQ pedal. Often ignored or written off by guitarists as a mundane utility item, or a sonic Band-Aid of sorts for a fundamentally flawed tonal foundation, the lowly EQ pedal is a powerful, yet frequently overlooked generator of great tones. In addition to sprucing up a less-than-stellar base sound or compensating for unexpected stage or monitoring anomalies at gig time, a good equalizer can help a solo cut through the mix, breathe new life into an old drive or distortion pedal, and help create rich textures that would otherwise not be possible. These are just a few examples that illustrate the great creative potential of the EQ pedal. Most EQs for guitar are of the simple graphic variety, with tiny sliders that boost or cut specific, pre-set frequencies. These can be excellent, and are all that's needed for many players, but for guitarists who really want to get into deep, surgical tone shaping, a parametric EQ is ideal. Parametric EQs are familiar to anyone who knows their way around a recording studio, and are the primary sonic carving knife of most professional recording engineers. The advantages of a parametric or semi-parametric EQ are significant, as they offer much more precise control over amplitude, bandwidth, and center frequency than other varieties. Here is a grip of our favorite parametric-style EQ's for guitarists who want to bring the power of these potent tone shapers to their pedalboards. This sadly discontinued gem from Boss is an excellent early example of a semi-parametric EQ circuit designed for the pedalboard. Manufactured from '91—'97, the PQ-4 was not a huge hit during its production run, likely being overshadowed by Boss's stalwart GE-7 graphic EQ. Since then it has gained something of a reputation for versatility, quiet operation, and the very musical way in which it pairs with dirt pedals. It offers broader shelving equalization for low frequencies and high presence, while mid frequencies are variable between Hz and 1. The selected frequency range can be boost or cut a hefty 18dB, and overall level can also be boost or cut by the same amount, giving the PQ-4 a lot of power to slice and dice a guitar sound. The best thing about the PQ-4 is its smooth, quiet, musical personality, which avoids the harsh artificiality of lesser EQs, and makes this pedal ideal for getting the most out of overdrive and distortion boxes. The Boss PQ-4 is not uncommon to find on the used market for between 80 and dollars. The Para Driver is an incredibly useful tone-shaping device, combining elements of guitar pedal, preamp, DI, and equalizer into a versatile tool that is as at home on a pedalboard as it is in a recording studio. It features lots of options for warming up, dirtying up, and routing a guitar sound, whether it's going to a tube amp or direct into a console, but the best feature is the EQ section. Treble and bass frequencies are fixed, but the midrange is a sweepable, semi-parametric circuit that can hone in on frequencies ranging from Hz up to 3kHz, covering most of the crucial frequencies for electric guitar. The SansAmp Para Driver is invaluable for recording, in particular, but I've found it just as useful as a regular component of my pedalboard, and it works beautifully after dirt pedals for adding extra bite, oomph, honk, sparkle, or whatever kind of enhancement might be desired. The DPE is a rare bird, and a weird bird as well, but it's guitar sculpting powers are a thing of legend. Reportedly used by The Edge, David Gilmour, and Adrian Legg, this discontinued box of vintage Danish sonic wizardry boasts a huge range and precision carving capabilities. Bandwidth knobs for each allow you to adjust how broad a frequency range it effects, from a wide one-octave band to a super narrow one-tenth octave. The selected ranges can be cut or boosted 16dB. It also features a fixed high treble control for boosting or taming overall brilliance, and an overall output gain knob. The DPE is so powerful that it's nearly overkill for electric guitar, and its learning curve is fairly steep, but it's a spectacular sounding equalizer for the truly dedicated tone tweaker.
Parametric Equalizer Design
If you're into playing with tone controls and notch filters to see how they change the sound out of your effects, you will undoubtedly have built several glops of R's, C's and pots, maybe some L's to make up the tone networks. While this is fun, it's not very flexible. Sooner or later you might wonder if there is a more general solution to messing with tone controls. Everyone is familiar with the sound of a wah pedal. This is a resonant peak in the signal that can get moved around. Not so familiar is a notch, or a sudden reduction in level at one frequency. Sometimes a notch can be very useful in getting a specific sound. Even better would be if you could get either a peak or a notch, depending on how you set the controls - something like the frequency response diagram. What's Q? The techie explanation is that Q is the energy stored divided by the energy dissipated per cycle in a network. Let me translate that into something more useful. A guitar string will vibrate a long time if plucked. The initial pluck that sets it into motion stores a chunk of energy in the string that is saved by the interchange of motion for string stretch on every vibration. It dissipates very little of its energy per cycle, so it stays in motion a long time - it's a high Q mechanical filter. If you put your finger on the string, it stops ringing very quickly because your finger damps it, removing a lot of energy as the string moves. Your finger has lowered the Q of the vibrating string, removing a lot of energy from it each vibration, so it stops vibrating quickly. Q is also a measurement of bandwidth. Q is kind of a measurement of resonance, then. A moderately resonant filter is like a wah pedal - There is a peak of frequency response at the resonant frequency of the wah. To give you an idea about how Q relates to sound, most wahs have a Q of about Q is also related to selectivity. A high Q filter, like a guitar string, vibrates primarily at one frequency. As Q gets lower, the resonance gets wider in frequency. A high Q notch is just like the reverse of a high Q peaking filter. A notch filter has a kind of a dead zone where there is very little or no response to signal - very much like a guitar string with a dead or muffled note on one fret. The higher the Q of a notch filter, the more the response is cut at the notch frequency and the narrower the band of frequencies that are cut. Low Q notches cut a broader band of frequencies by a lesser amount. The circuit is a simplified version of a hifi graphic EQ. There are a number of series L-C filters which are connected to the wipers of a pot, one per L-C filter. It is a characteristic of a series LC filter that it has a high impedance except at its resonant frequency. At that frequency, the series impedance drops to a minimum, which is zero if the components are perfect.
I combined parts of the graphic equalizer I did previously with information on how to make gyrators from R. Keen at Geofex. Updates to come soon. Update This is my second take at using a transparent film for artwork and labeling, and it came out a lot nicer now. Only thing missing is a few many! Awesome site, thank you for all your hard work. Can this be used as outboard gear, for mixing through interface? If so does anything need to be altered? Thank you. Many mistakes on the vero. Hey, thank you for the layout, it works like a charm!! I just ordered a few NEs they might be a bit quieter as the circuit is a bit noisy, especially if you boost the high frequencies… But anyway, great Equalizer nonetheless! Best regards, Lennart from Germany. Hi, thanks very much for this layout. It would mean that moving one would affect the other? Thanks again Nico. Hallo, the controls for Q and Freq are independant? R1 will affect both Q anf freq thanks. Hi Dennis, I did that one several years ago, and I can no longer remember why I did it the way I did. It would probably look a bit different if I did it today. Try the n caps. They may help. Nice design but why arent there any decoupling caps for the opamps? I will be building this the next few days with the decoupliong caps of N in the minus and plus voltages lines and i will report back.