Hi, can you suggest some sources/ audio electronics books on how to design onboard bass EQ? More broad book on preamps (for instruments, microphones, low noise/ discrete) and other audio circuits might be helpful as well.
I am particularly concerned about the hiss noise. The bass I am playing with it is audibly noisier compared to another bass I have.
I've put up some pickup buffers to make an active pickups blend and then the stock EQ follows.
My idea is to make as simple as possible low noise, low current draw onboard electronics instead of what it is now (some flying veroboard with the buffers + the sealed stock EQ)
Preferably discrete, with a few fet/ bjt transistors.
Layout:
- pickup buffers -> blend pot -> 3 band EQ -> vol pot (to keep best signal to noise) -> output
Some crude idea for the EQ..
The EQ bands, topology, type of filter, e.t.c. is important to me mostly for one thing - when I turn the treble to the max, there is the LEAST amount of hiss possible..
I am particularly concerned about the hiss noise. The bass I am playing with it is audibly noisier compared to another bass I have.
I've put up some pickup buffers to make an active pickups blend and then the stock EQ follows.
My idea is to make as simple as possible low noise, low current draw onboard electronics instead of what it is now (some flying veroboard with the buffers + the sealed stock EQ)
Preferably discrete, with a few fet/ bjt transistors.
Layout:
- pickup buffers -> blend pot -> 3 band EQ -> vol pot (to keep best signal to noise) -> output
Some crude idea for the EQ..
The EQ bands, topology, type of filter, e.t.c. is important to me mostly for one thing - when I turn the treble to the max, there is the LEAST amount of hiss possible..
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Does it worth at all to make a simplistic transistor circuit (one transistor for one low noise opamp...) in terms of noise?
F.ex. the following layout:
------
1&2. Individual input buffers per pickup
- blend pot at the buffers output
3. Buffer before the tone stack
- some tone stack
4. Output after the tone stack
------
The opamp version could use quad opamp with an opamp for each active node (1 to 4)
The transistor version using one transistor instead of opamp.
Like the J201 buffers schematic above and the crude tonestack schematic above with one transistor at the input and output.
Would the 'noise analysis' of a simulation software give a realistic picture of the noise density if I simulate both variants?
On a first glance, I remember some guy told me that the large resistors at the J201 gate (the pickup buffers) may insert noise.
Another thing - I suspect the trebble control of the stock EQ is a high shelf.
If it is a fixed band (f.ex. at 5k) I may avoid noise amplification for higher frequencies above 8-10k when turned up.
F.ex. the following layout:
------
1&2. Individual input buffers per pickup
- blend pot at the buffers output
3. Buffer before the tone stack
- some tone stack
4. Output after the tone stack
------
The opamp version could use quad opamp with an opamp for each active node (1 to 4)
The transistor version using one transistor instead of opamp.
Like the J201 buffers schematic above and the crude tonestack schematic above with one transistor at the input and output.
Would the 'noise analysis' of a simulation software give a realistic picture of the noise density if I simulate both variants?
On a first glance, I remember some guy told me that the large resistors at the J201 gate (the pickup buffers) may insert noise.
Another thing - I suspect the trebble control of the stock EQ is a high shelf.
If it is a fixed band (f.ex. at 5k) I may avoid noise amplification for higher frequencies above 8-10k when turned up.