Audio shops back in the day ran on coffee...still have my 3 mast sailing ship mug from back in 1978 right here today. However this thread is about McIntosh updates and mods so...... Terry, Back a number of months ago you posted a pdf of a noise spectrum of a C28. I find this interesting and informative. Only 24 times did anyone bother to look at it. It is a shame because it shows how much can be done to improve the C28 preamp. I have reposted because I believe we all can learn much from it if we bother to study it. Can you highlight the test equipment you used for those of us still stuck in back in the day? Do you remember what you did to this unit? The 60 Hz noise still seems high...I have found shield issues on my project C28, mostly in the filter circuits and the convoluted ground drains....how about you.