Tube Rolling Update: The replacement set of NOS tubes arrived last friday. After about 20 minutes of listening with the stock tubes (at a set volume level) I decided to go ahead and replace all the tubes all at once just to be sure all the tubes are working and that they light up properly - and they did.
The replacement tubes I receive:
1. 5Z4 Type - 5AR4/GZ34 Mullard standard-base.
2. 6L6 Type - Tung Sol KT66/7581 (matched pair).
3. 6SN7 Type - KenRad VT231 black-glass (matched pair, rectangular plate - not round plates).
First impressions: not much of a difference I'm afraid. I was expecting a more immediate and easily discernable change to the sonic characteristics of my system; but that was not the case at all, not like the time when I replaced a set of unknown Chinese KT88s tubes with Valve Art KT88s on my Air-Tight ATM-2 power amp. The KT88 experience was immediate; it felt as if the power had doubled on my amp. So in comparison, my first real tube rolling experience was a bit of a let down. Also, this was my first experience with ÂmicrophonicsÂ. With the Kenrads plugged in, even a mild tap on the preamp knobs will generate loud humms through the speakers.
But now that IÂve had these tubes for a few days in my system, I feel the sound has warmed up appreciably, the music has more Âair and the bass is definitely more defined. I think some of the characteristics discussed throughout this thread are slowly beginning to appear in the system.
Late last night my wife and I returned home from a birthday party and instead of going right off to bed, I decided to play with the system a bit more. So I took out the Kenrads VT231s and put the stock 6SN7s back to see what changes are, if any. I could be wrong as I was quite tired and slightly intoxicated - I thought the stock 6SN7s sounded better with the rest of the NOS tubes in place than the kenrads vt231s. As I said, IÂm not a 100% sure however I will check this out tonight as soon as I get home and report back soon.