I am using rogue audio m180s , will these tubes work ?
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I run Sonic Frontiers SFM-160s, which use four KT-88/6550s per amp to produce 160w. My current situation has Gold Lions in the amps. Great sound.
I exchanged e-mails with Chris Johnson re: the KT-120s. While an increase in power of about 10% is common in SF gear (which of course was not designed to take full advantage of the KT-120s), Chris felt the major benefit in his equipment was the LT reliability. The SFM-160s really push the four KT-88s hard and I do have tubes go a bit more often than I would like. With the KT-120s, the LT reliability issue is much better.
I have not tried this, as I recently re-tubed with matched quads of Gold Lions. Plus, I am very happy with the sound.
Folks, beware that the KT-120 draws 1.8 Amps heater current per tube, as compared to the KT88 1.6A spec.
A stereo push-pull amp with four KT-120 tubes will draw 800 additional milliamps from the heater winding. The amplifier's power transformer will run hot and possibly fail in the long run.
I think this may be an excellent tube for a new design buit around its strengths.
IMO one can safely try KT-120s only on conservatively designed tube amps with over-specified power transformers that run cool and that use self-bias / cathode bias.
Fixed bias amplifiers need to be modified before one installs KT-120s, so this rules out most USA-made muscle push-pull amps.
I hope this helps.
Help me better understand "self-bias/cathode bias".
My Sonic Frontiers monoblocks use four KT-88s per amp. I have a knob on the amp that allows me to select one of these four tubes. Using a screw driver, I can turn a shaft with a slot in it to adjust the bias using a meter.
Is this a fixed bias amp?
I have recently installed a set of the 120s in 2 of my amps... First in a McShane modded Citation 2 with a level 2 plus kit and a complete rebuild...and secondly in a pair of Heathkit W6M mono blocks. I can hear a marginal difference in the Citation although I expected a little more out of them, but there is a marked improvement in the W6s which actually outperform the Citation now. I must add that the W6s have also had a McShane type upgrade to the power supplies and have more than 5 times the capacitance of originals. I'm sure this helped. I bumped the bias up a bit, but am still running them at a very conservative figure for the bias. I'm looking for longevity rather than the absolute max the tubes will do, but they do kick butt!
The only thign you need to be concerned with is 1. The height of the tube is considerably more than KT88s and 2. The filament draw is quite a bit more than 6550s or KT88s. Check your schematic and make sure you have the extra current to handle them....otherwise you might make a boat anchor out of your power transformer. An easy way to check if you don't have specs is to measure the filament voltage with the stock tubes installed. Then try it with the KT120s. If you notice a drop in the voltage your transformer won't handle them....don't risk it. Otherwise, have fun... they have excellent bottom end and are very clean sounding tubes. My favorites have always been winged C 6550s, but I might have found a new favorite....and the prices on them are dropping considerably.
Hope this helps someone.
I just heard about the new KT 120 tube. I own an ARC VS 115, which came with "Winged C' SED 6550 tubes. Does anyone know whether the VS 115 will need an ARC mod in order to handle the KT 120.
As is, my amp puts out plenty of power for my system. I really don't aneed anymore. More importantly, does the new tube sound better than the 6550?
They work great in my new Jolida JD502P...I talked to everybody except the janitor (unless I DID talk to the janitor) at Jolida before risking transformer meltdown and was assured it was fine...they do run hotter than 6550s, but sound more refined with seemingly more dynamic range and treble accuracy than the 6550s...not as much physical "tube glow" since the grids are less exposed, but that's OK. I now have the original 6550's, KT120s, and a set of new Svetlana KT88s (just got those) for the damn thing so off I roll!
Damn Wolf that is a lot of tubes for the Jolida. I'm curious to know your findings on the Svetlana KT88 tubes with the 502P. When I went to one tube e-tailer inquiring about the Tung Sol KT-120 he said he won't be carrying the KT-120 but recommended the Penta KT-88SC for the Jolida. At $208 for the quad I'll keep them in mind but right now I'm focusing in on the KT-120.
Just putting this out here as an FYI.
I know TC Tubes has a matching service for the Tung Sol KT-120 this could be another alternative. When I had corresponded with Jim McShane here is what he said about the matched Tung Sol KT-120s he sells.
"All tubes (even new) are carefully tested on my AVO
CT-160, TV-7 or B&K 747 testers. Power tubes are
tested and matched at real operating voltages, not
just with a tube tester.
The KT-120s are run in for at least 24 hours then tested at
465 volts on the plate and screen with -50 on the grid. They
are tested for grid current ("gas") and shorts while blazing hot from the match rig."
I hope this helps