The MCP series are particularly suitable in this application, giving one, two or four op amps in an 8 pin or 14pin DIL package at low cost. A negative supply is easily provided as described below. In general amplifiers of this type require positive and negative supply rails connected to each amplifier (indicated but not fully shown in the diagram). However the gain can be adjusted by trimming R1a & b, and any voltage offset by adjusting R5, VR1. First stage amplification is provided by IC1a (IC1b) while the second stage around IC2a amplifies the difference between V3 and V4.Īccuracy depends on the precision of the resistors used, so pairs of resistors Ra, Rb should be matched. The circuit provides amplification through two stages. Comments are appreciated.The circuit provides two measuring inputs V1, V2 that will be used to make a measurement of the voltage difference between them. It is still under development and may contain lots of errors. DC blocking caps on the output are left out intentionally, the UcD should take care of this.

The values for the stepped attenuator are just thown in for now, I'll adjust them when the thing is built and I can try what works best. A more sophisticated regulator would probably be better, but this is simple and I have zeners handy. Non usable frequencies are R/C-filtered, don't know if this is really needed. The idea of the switched XLR-1/4' combo jack is, that the opamp line driver output is grounded when XLR is used. (If the preamp already has a balaced signal, it will bypass this stage.) I also wanted some kind of attenuator to be able to drive the preamp hard without clipping the Ucd (or blowing the speaker). So I decided to include a small opamp stage that amplifies the signal and has a balanced output. 1, they want a balanced signal, and 2, the line level output voltage from an instrument preamp may vary greatly. Now there's two 'problems' when using a Hypex PA module for instrument use (I've done this once before with a Ucd180ST). The Peavey is far too complicated for me to try and fix, so I decided to ditch it (maybe have it fixed later) and this time build a new one from Hypex modules (namely Ucd2kOEM and PSU SMPS3k). My old one, a Peavey IPR1600 was great for this - until it suddenly stopped working. I play bass through a tube preamp into a class D PA power amp.

Ic1a op amp