Hello there, I'm Mick, I study computer engineering in Rome and I'm working on my final project; the project is a 2 in 2 out digital audio USB interface tailored to guitarists, because I'm a guitarists and I've never really satisfied with the sound of commercially available, mid range digital audio interfaces.
Right now I'm facing some problems with the design of the preamplifier section, which will be probably the key point of the whole thing! The thing is: I got a 2 channel A/D, both channels are single ended, input impedance is 20k, input capacitance is 10pf, and the desired input signal level is 2 Vrms; for a normal line input, I think that connecting the line cable straight to the A/D input will work, but I know that I need some good preamplification and a much higher input impedance to connect a guitar to that input. Now, a simple adjustable gain preamp will suffice for this job, but I'd like to test out a tone controlled preamp desing too; but, all the "classic" designs I've seen around here and through the rest of the web are operating near +-15 V, that is tooooo much for me! I want a circuit that can be easily powered via USB, that means 5V maximum, and I need a single supply design! What should I do?
Note:I've seen the DRV602 from Texas Instruments which is a single supply op amp with internal charge pump that works as a 2-3Vrms line driver from a single 3.3v-5v supply source, and I'm using this as a single ended input filter and line output stage after the D/A conversion... could I possibly do something with the very same chip for the input stage??
Other note: just to clarify, I'm using a Wolfson WM8569 codec chip , and the output stage design is based around (read:copied
) the WM8569 reccomended filter stage design and the DVR602 reccomended external components design, with 3.3v supply for the DVR602.
edit: corrected the topic name, it said "2 Vrms" instead of "1 V rms"
Right now I'm facing some problems with the design of the preamplifier section, which will be probably the key point of the whole thing! The thing is: I got a 2 channel A/D, both channels are single ended, input impedance is 20k, input capacitance is 10pf, and the desired input signal level is 2 Vrms; for a normal line input, I think that connecting the line cable straight to the A/D input will work, but I know that I need some good preamplification and a much higher input impedance to connect a guitar to that input. Now, a simple adjustable gain preamp will suffice for this job, but I'd like to test out a tone controlled preamp desing too; but, all the "classic" designs I've seen around here and through the rest of the web are operating near +-15 V, that is tooooo much for me! I want a circuit that can be easily powered via USB, that means 5V maximum, and I need a single supply design! What should I do?
Note:I've seen the DRV602 from Texas Instruments which is a single supply op amp with internal charge pump that works as a 2-3Vrms line driver from a single 3.3v-5v supply source, and I'm using this as a single ended input filter and line output stage after the D/A conversion... could I possibly do something with the very same chip for the input stage??
Other note: just to clarify, I'm using a Wolfson WM8569 codec chip , and the output stage design is based around (read:copied
) the WM8569 reccomended filter stage design and the DVR602 reccomended external components design, with 3.3v supply for the DVR602.edit: corrected the topic name, it said "2 Vrms" instead of "1 V rms"