NOS replacement

These are fantastic tubes, I put them on the same level as the RFT's or old Teslas made at Trinec or any other of the great Eastern European EL34's from the 70's and 80's. In my experience they are exceedingly well made, handle current and voltages well over their published spec, operate quitelty and with predictable reliability. Those are the qualities of the best NOS tubes. As for Sound, these tubes dont add much coloration, maybe thats why they are becoming 1st choice tubes for Audiophiles.In guitar amps that lack of coloration is almost a sort of color itself. They are a great choice if you like 6550 's but dont have an amp that should use 6550's - like a Marshall 3203 Artist or Blackstar 20, for example. These tubes provide headroom and the treble bite and detail of the 6550 and also that cracking-ice overdrive cruch of the 6550's without the high current demand. Not a soft clipping, saturated EL34 , its a ballsy old school metal sound. If you want a saturated, midrange forward EL34 sound , then buy the SED EL34, its the best of that type.