[sdiy] preamps for piezos (slightly OT?)

[rsdio at audiobanshee.com]

Unless the second stage is an EQ, you're not going to regain any lost bass.

The problem is that the first stage is acting as a high pass because of the passive components ahead of the first op-amp, and the input characteristics of the op-amp. Changing the loading and op-amp type should fix this.

The Mikrophonie preamp already has two stages.

Brian


On Feb 14, 2016, at 2:35 PM, Busby Bergson <busby.bergson at gmail.com> wrote:
> a second pre-amp stage might recover some of the lost bass frequency? 
> 
> On Sun, Feb 14, 2016 at 4:47 PM, jarno.verhoeven at ziggo.nl <jarno.verhoeven at ziggo.nl> wrote:
>> Yes, I saw this in the schematic, maybe mine was an older version. But that schematic is a fine starting point.
>> 
>> ------ Origineel bericht------
>> Van: Busby Bergson
>> Datum: zo, 14 feb. 2016 21:08
>> 
>> Hi there -
>> 
>> The "Mikrophonie" preamp looks very similar to what I'm building: http://musicthing.co.uk/modular/wp-content/uploads/2014/06/Mikrophonie-2-2-Schematic.pdf
>> 
>> Though I'm not using any sort of input cap (nor does the schematic) - that would potentially serve as something of a high-pass, wouldn't it? 
>> 
>> I am also using a TL084, which does have JFET inputs, correct? 
>> 
>> Perhaps it is a matter of experimenting with other ICs. 
>> 
>> On Sun, Feb 14, 2016 at 2:22 PM, Olivier Gillet <ol.gillet at gmail.com> wrote:
>>> The choice of op-amp matters. Bipolar op-amps have a low input
>>> impedance (a few hundred k) which could have an impact on bass
>>> response. An op-amp with JFET inputs would be a better choice here.
>>> 
>>> On Sun, Feb 14, 2016 at 7:20 PM, Busby Bergson <busby.bergson at gmail.com> wrote:
>>> > hi synthdiys,
>>> >
>>> > i'm currently experimenting with contact mics. they sound pretty good going
>>> > into a guitar amplifier, directly - but if i want to send them through my
>>> > other circuitry, it seems that they require a specialized preamplifier, to
>>> > compensate for their impedance.
>>> >
>>> > i've been using something along these lines:
>>> > http://music-electronics-forum.com/attachments/4228d1232615609-non-invert.buffer.gif
>>> >
>>> > however, i'm noticing that there is still a significant high-passing -
>>> > compared to the bassier direct-to-guitar-amplifier arrangement.
>>> >
>>> > any thoughts?
>>> >
>>> > -  b.b.
>>>