Riverstone Audio - 6J9P-E (6Ж9ПE / 6zh9P-E) Matched Pair (2 tubes) - Vintage Russian Vacuum Tubes - Amplitrex Tested - Replacement for 6J9, E180F, 6688 Tubes - Platinum Grade - NOS (2 Tubes) 6J9P-E

I'm giving them a five against the tubes that came with my nobsound NS-80E... These absolutely add brightness and crispness from those tubes.Honestly those nobsound tubes aren't that bad. I have a pair of Beyerdynamic DT 770 Pro headphones at home, and I think that it actually jacked the bass/volume ability up a bit, but it could be a bit of "they sound better in general" placebo.

These work fairly well when sound is running through them, but without any audio, they emit a constant hiss that's noticeably louder than other tubes of the same form factor. Not horrible, but wouldn't recommend.

I was very happy with everything about the transaction, and the product sounded excellent, especially for the money. Riverstone is very unusual in providing very detailed specs about everything connected with the product, as well as providing an unprecedented guarantee. And the best Russian new or NOS NIB tubes have clearly come a long way.

Great tubes from a great vendor! Swapped out the stock tubes for these russian 6J9P-E tubes,. Excellent warm sound. Riverstone Audio (vendor) provides great products/service. Would buy again.

The sound of these tubes are exellent.