unpleasant distortion on 18w lite - any idea?

[Mauri]

Hi all,
a long time ago I built my first valve amp from the ampmaker.com schematics attached a long time ago. It was working fine back then, but then it remained unused for a couple of years. I have now fired it up again and it sounds terrible. I strummed a chord or 2 and recorded for reference. This was recorded with the volume at around 11 o'clock and the nasty distortion gets worse at higher volumes. I checked all the soldering, which is fine. Voltages look OK. I swapped all the valves. Nothing obviously wrong with the caps. So I am beginning to think it may be the OT, but before going ahead and investing in a replacement, I was wondering if anyone had heard something similar before and if they identified the issue/solution.
Thank you so much in advance

[JMPGuitars]

It sounds like you need the Paul Ruby Mod. You can see it here in this schematic: files/JMPGuitars_18_Watt_Superlite_TMB_Schematic.pdf

Thanks,
Josh

[Mauri]

Thank you for your reply. I'll try that out.