Just checked my Psvane CV181 tubes in front positions (warm) and TJ Full Music 6SN7s (slightly warmer) in rear positions in my Cary SLP-98 preamp. Can hold my fingers on both, neither are "hot" or burn fingers. Put my tongue on them, no issue there either - just kidding, yak yak 🤪. Power transformer is separate/external on mine, and not heating up the whole preamp top plate surface area either. It's going to vary by design with each preamp, transformer locations, and casing, venting too.
