![]() ![]() the other leg must feed a 'circuit' that combines this leg with 5 others of the same type. One leg of the signal is to feed a device that must receive this signal in isolation. What I'm trying to achieve is 'Y' off (split) the signal. The ? above is becuase I don't know what to use! > Output B (to be summed with 5 others of the same characteristic) I'd now like to split the signal (actually there'll be six indidiual signals but for the purpose of simplicity, I'll just refer to one). I've built/tested the board - it seems to work fine. Many thanks - all points were duly noted. Since you have already defined what it has to be in the previous statement, you don't really have much choice. Ideally you want to use as low of values thats practical to keep noise low. Will just have to do the math to find what values you need. R2 will be a bit more than 1meg and R3 will be 8 times higher. Treat R3 as if it were going to ground as well, which it is basically for dc analysis. In other words is it better to use higher resistances in the feedback loop (eg 800k & 100k to get the gain of 8) or smaller resitances (eg 8k & 1k).or does it matter not? I'm not understanding what they mean by "the parallel combination of R2 and R3" (I understand what parallel resistance is & how to calculate it!).but in their diagram the resistors R2 & R3 in series?!Īlso I'd need R1 to be at least 1M ohms (so as not to load the piezo pickups).where does that leave me wrt their statement for the values of R2 & R3 (& bearing in mind I need a gain of 8)įinally does it matter how I achieve a gain of say 8. For lowest input-offset currents using bipolar op amps, R1 is usually set equal to the parallel combination of R2 and R3" "In this circuit, a resistor is connected between the op-amp input and ground, to allow the input bias currents to flow. ![]() See section one "Common problems " 1) Failure to provide a DC bias-current return path when using AC couplingīelow the diagram in that section is this statement. If I do need AC coupling, then this article suggests my final circuit will need a bias resistor. Now bearing in mind my input will a guitar piezo pickup.I'm not sure if I need a design with AC coupling ? Whereas on that same page further down the AC coupling circuit obviously has. The basic circuit has no AC coupling capacitor If you look at these two simple circuit diagrams here. which will need a gain of upto 8 (I intend using a variable resistor to set the exact gain required & then replace with a standard resistor.this will make the circuit more compact). I now intend using a non inverting opamp circuit (dual supply as the rails can easily be sourced from the the unit I'm interfacing guitar with). Rather than spam the board with new threads, I though it'd be best to tack my latest questions on the bottom of my original thread! I've thrown the Roland board away (too much hassle!) & started making my own board. Therefore probably reasonable to assume that each circuit should have a reasobanle flat eq curve for all stringsĭoes a pcb layout/designs quad opamp exist that I can modify with 'tweaked' components as necessary? therefore, the preamp should have a wide enough frequency response (I'm guessing) to allow not amplify the fundamental frequency but also the harmonics that plucking a guitar string yields. This identifies the pitch of a note based on the characteristics of the picking transient, which in turn allows the correct MIDI note to be sent with minimal delay" ![]() "the software uses Early Transient Recognition, which is based on neural net technology. The axon midi interface apparently determines the note being played by analysing transients. A design based around a dual rail supply is fine as the 13 way midi cable from the Axon unti supplies t+ve & -ve rails.įor development, I'll initally need a cct that allows variable variable gain (ie while I interface it with the aforementioned guitar-midi interface & experiment to establish what signal evel the unit likes as an input best). Must be very small as I want to put it inside a guitar! (As much as I'd love it to be based on SMT, I don't have the facilities to make, so there I guess it's out).Ĥ. Each opamp amp circuit to amplify a single guitar string (therefore six opamps needed, thinking of a quad opamp chip such as the TL074CN - leaving two redundant opamps on the second chip))Ģ. I seek a cct based around a quad opamp (14 DIL), which can amplify six guitar strings (sensed via a piezo pickup in each string's bridge saddle) in order to drive a guitar->midi converter Such as this ġ. ![]()
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