E.A.R. 509 amps
I had a pair of the original mk1 amps for quite some time.
Very nice sound, especially with volume contol bypassed.
Easy to work on, held its bias ( I always checked every 2-3 months).
I heard they are great driving Quads, which are very picky to drive properly.
Bass was very good, nice extended highs, not truncated like some of the older amps .
Definitely not a tubby sound...more neutral sounding.
I'd say go for them!
Caution ! if you are referring to the pair that's on ebay going off today (6/28)...be aware that he had a pair of 509's end 6/26 for $610. I questioned him about this during the week and never received a reply. If you check his >100 feedback, it is for items purchased by him for less than $5.
I would be careful here !!! If you had a mint pair of 509 amps would you sell them for $610??? and he has two pair?