They are burned in for 24 hours and matched in Quads by New Sensor. Beware of other Vendors matching their own tubes. Try a Quad in your ST-70, VTL, Marantz 8B, QuickSilver MX-190 (2 Quads or an Octet), or a Pair or Quad in your Marshall or any Guitar amplifier that uses El34 tubes.
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