I have a DNA-225 that has a transformer hum, which (I think) is also seeping into the audio signal (i.e., coming through the speakers). This model does not appear to be subject to the troubled, double-sided input board issue. But, I recall reading somewhere that one maker of McCormack transformers from this time were particularly subject to hum; I can't find, or recall, which brand of transformer it was, although I think the brand name started with a 'C'.
A while ago, I spoke on the phone with Pat about my issue, and he recommended trying a better power cord, and checking for DC noise on my main line. But, after trying a few different power cords (costing up to $900), and trying two different DC blocker devices, I still have hum.
My next step is to get the amp serviced and/or upgraded. I'm able and willing to invest in this, but I wonder if a simple repair/replacement of the transformer makes more sense than a total upgrade.
Other power amps in my stable are:
- DIY clone First Watt Aleph J
- Butler Audio TDB 2250
- Symphonic Line RG1 MK3
- McCormack DNA-125 (still present, but lesser amount of hum)
I also have an Adcom GFA-555, and a Phase Linear PL-400 (with White Oak Audio upgrade), but these are really backups.
My current 'itch' is a CODA S5.5 pure Class A amp, so trying to weigh options. Thanks in advance for advice.