jsrtheta
Addicted to Fun and Learning
Well, here you go gentlemen, I dug out the images from 2016.
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The purple and red is before I tweaked the balance control to balance the channels. The green and white is a best case 'flat' frequency response of the integrated amplifier at (1W/1KHz/8ohm (2.83V) preset before sweep). Eeek! -13.5dB at 20Hz and -3dB @20KHz It was so bad I ran a loop-back to make sure my gear wasn't broken.
Was it the preamplifier or the power amplifier or both? I investigated this further by feeding direct into the power stage internally and got this (1W/1KHz/8ohm (2.83V) preset before sweep):
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Around -3.5dB @20Hz and -0.7dB @20KHz- slightly better. So, it was a combination of the preamp stage and power amp stage. Basically it tested and sounded like a PA amplifier (Murray also made PA amplifiers under the Auditec brand). It does have a 'softness' control which when activated gave the response below, not unlike a typical loudness, except it is not linked to volume position. It does however, make the amplifier partially listenable.
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These are screenshots from my trusty old AudioLab hardware.
Murray's basic construction and component quality was excellent for the mid 70s era. A few glaring mistakes in design, but I didn't reverse-engineer the unit to work out where all the issues lay as it was bought just a curiosity and designed by a 'legendary' Australian. Judicious use of the tone controls could partially flatten the response, but the extreme adjustments required to do so were ridiculous. I was tempted to unscrew the knob screws and re-position the zero point, but just left it, as it really wasn't flat in any case.
Man, them are butt ugly!