Tubes Asylum Questions about tubes and gear that glows. FAQ

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Tubes Asylum ]

---

[ Alert Moderator ]

---

Guitar Amp Review of the Gold Lion KT66

Posted by TubeAcolyte (D) on August 8, 2019 at 13:56:43

Hello!

I recently came into ownership of a quad of New Sensor Reissue Gold Lion KT66 tubes. I just had to share my listening impressions! WHAT A TUBE!

These were installed into a Masrhall-esque clone. Originally, the power tubes were New Sensor Reissue Tung-Sol 6L6GC's. The preamp is loaded with pretty standard NOS stuff.

At moderate volume settings, Tung-Sol 6L6GC's were OK. I found them a bit low-end heavy and a bit unexciting and dull. Standard. Like a Clydesdale horse: meant to work, not really about finesse.
- Testing at mid-master and high-preamp, the Tung-Sol 6L6GC could sound bloated in the low-end, confused in the mids, and recessed in the highs. There was simply no articulation of the preamp signal. it was as if my signal was gradually being stuffed into a tube, clipping and topping out, and losing signal information due to over-compression. There was just no fun or life in it.
- With high master and mid-preamp, I got a clearer signal, but the tones were still "meh"; the low-end was still bloated, mids were still a bit confused, the highs were somewhere between somewhat-accurate to shrilly, and break-up was boring and a little farty/thwoppy/raunchy

There came a point where there were few settings with the EQ that could tame the crap tones. It just didn't sound right. I know what magical sounds a 6L6GC can make - they're key to the Fender tone and a slew of other amps. And, I've heard Marshall amps with 6L6GC's. This was simply no-bueno.

Installing these KT66's was like lifting a wet blanket off my amplifier and then some. Everything just got better. Frequency response became more even, and there was greater articulation of sounds across a more open sound stage. There's a certain sweetness to the low-end, the mids are magical, and the highs roll off at just the right points. Also, I found that my preamp and EQ became useful again; it was like I had rediscover the amp all over again.

As the master volume is increased and we get into power tube break-up territory, there's a life that comes out in the Gold Lions that just didn't with the Tung-Sols. It's like an energy, or a form of excitement. Fresh tubes? Perhaps. Better tube? Very likely.

Power tube overdrive with the Tung-Sol 6L6GC sounded like "GGRRRJJJJJSSSHH", like the tube was attempting to play a Metallica through a paper-towel tube stuffed with bees. The Gold Lion reveals a more rolling "GRRINGRRRINGINGING". The amp now has that classic Marshall overdrive we hear in old-school ACDC and Hendrix tunes. At certain higher-volume settings, there's a very satisfying 3D "ahhh" that comes through as well.

I have some more testing to do - I'll update my post when I have some more notes to share :)

Some specs for the technically minded:
-Transformers are Heyboer
-Power Transformer label: JTM45-HV; HTS-7134; 9960824
-Output Transformer label: 103 PT 6:6/8K/100V; HTS-8969; 9960718
-Choke label: P-CF22699 9890652
-460V anode / 459V screen
-16.75v of bias supply (on standby)
-Tubes are running about 25.5-26ma each (just shy of 12W idle)
-Speaker load: 4x12 JBL G125 wired to 8ohm
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
May your tubes be lively, warm, and long-lasting. Holy be thy heater.

This post is made possible by the generous support of people like you and our sponsors:

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---