Just got my Tung_Sol KT120s today and ran a few tests on them. Also since the tests I have managed to get a few hours listening in. Tubes this big should take 100hours plus to burn in. After the power test (below) I have listening notes. My current amp is the Be Bamp which usually has matched JJ Blue Glass KT88s running at 93mA idle current.
The amp is SE UL with 0NFB.
I ran a power test with the KT88s to see if simply by plugging in the 120s I'd get more power. And I did!
The way I tried to test initially failed so a resistive 9.4ohm load with the digital CRO and the function generator was used.
All tests @ 1khz into 9.4 ohms.
The KT88s produced 6.6W RMS. By simply replacing the 88s with the KT120s the max power jumped to 8.0W.
My speakers are 6ohms and with the 88 I have measure 7.8W in the past. I had to use two 4.7ohm resistors and just read across one to keep the input voltage peak across the digital CRO down.
You can see a 17% jump in power simply by swapping tubes out. I upped the plate idle current to 111mA but this gave no more power so I left the idle current at 93mA. This way I can roll between 88s and 120s.
Worth the money for sure. I bought a quad matched set. The tubes are big but not a patch on my 211s. Think of over-sized KT88s and your in the ball park.
Sound appears a little more open with the 120s. Good authority and transients, balanced. Lighter sound than the 88s. The 88s are a little darker, these feel brighter and crisper through the mid range. The bass starts to roll off after 31Hz but still plenty of energy at 20Hz. The bass tests are from a CD so the whole system is still delivering down at 20Hz!! There is a room resonance at 50Hz (windows rattle, floor (wooden) shakes.UPDATE
- see this blog post for my Tung-Sol KT120 Tubes - SE Listening Impressions and Notes
(29 June 2010)