Are you using the stock tubes?
TAD-60 Owners
Paul recently added the following language to the Bias Instruction page for the TAD-60:
*NEW SINGLE ENDED CLASS A BIAS: This amplifier will operate class A for the first 10 watts and class A/B 10-50 watts if final biased this way: V1, V3 set to 175, V2, V4 set to 500. See if you notice improved smoothness in the midrange and richer bass compared to regular all 350 bias. Only giving up 10 watts on top (50w instead of 60w) for class-A mode. Single ended - because the 500 biased tube is doing most of the amplification 360 degrees up to 10 watts while the 175 biased tube is acting as an out of phase damping brake, offering little in phase amplification under 10 watts. Have it all, single ended class A and 50 watts A/B when needed.
Check it out!
*NEW SINGLE ENDED CLASS A BIAS: This amplifier will operate class A for the first 10 watts and class A/B 10-50 watts if final biased this way: V1, V3 set to 175, V2, V4 set to 500. See if you notice improved smoothness in the midrange and richer bass compared to regular all 350 bias. Only giving up 10 watts on top (50w instead of 60w) for class-A mode. Single ended - because the 500 biased tube is doing most of the amplification 360 degrees up to 10 watts while the 175 biased tube is acting as an out of phase damping brake, offering little in phase amplification under 10 watts. Have it all, single ended class A and 50 watts A/B when needed.
Check it out!