Micro power amplifier for line recording ver. 2

This version has output power about 250mW allowing to use it with cabinet for "night" playing.

Frequency response

sim15 - micro PA->speaker equivalent->speaker simulator

v30_s1 - PA->cabinet->microphone

Schematics (pdf)

Ready to transfer PCB (pdf)

Upper side assembly (pdf)

Bottom side assembly (pdf)

Assembled board

Some comments to the schematics:

For coils L1, L2 are used Epcos RM8-N87 cores. C13 non-polarized electrolytic capacitor. Potentiometer RV1 is used to set quiescent current (with no signal) of 3-4 mA for each output transistor.

J1 - for connection Volume control potentiometer, J3 - feedback connector (possible use of "Presence" and "Depth" controls), J5 - speakersimulator input level control, J7 - power input 12V.

J2 - input, J4 - cabinet output, J6 - speakersimulator input to record from "big" head in parallell with cabinet without using micro PA, J8 - speakersimulator output.

In box with mini mixer & phone amp

Samples recorded using JCM800 preamp:

Sample 1, Recorded via micro PA cabinet & microphone

Sample 1, Speakersimulator output

Sample 2, Recorded via micro PA cabinet & microphone

Sample 2, Speakersimulator output

Sample 3, Recorded via micro PA cabinet & microphone

Sample 3, Speakersimulator output

Sample 4, Recorded via micro PA cabinet & microphone

Sample 4, Speakersimulator output

Sample 5, Recorded via micro PA cabinet & microphone

Sample 5, Speakersimulator output

Sample recorded by Konstantin Dolotov (dks), LP guitar, UENGO-1 preamplifier (dks design), 1x12 cabinet CELESTION G12M & Sennheiser E906 microphone

Mix

Charvel Model 6 Orange Crackle with EMG 85 and Jackson J50BC, Chris Custom Screamer, ENGL Tube Toner e430 into KMG FET microamp (250 mW), Randall RG75 used as Cab only. Test includes recording with Shure SM58 without cap, PA line output parallel to cab with impulse (Mesa 4x12 V30) and cabsim out of microamp.