Apr 072018

My favorite power tube for my vintage McIntosh MC30 monaural amplifiers have been the gray plate GE 6L6GC’s.

Vintage McIntosh MC30 monaural amplifier with GE 6L6GC power tubes.

The GE’s provided a warm, rich, and naturally musical presentation that even the highly esteemed black plate RCA 6L6GC’s had to bow down to.

For my hot-rodded MC30’s the GE’s take musicality to another level, but they are getting expensive at around $90 USD each!

HARMA cryo’d 5881 from Watford Valves.

When my GE 6L6GC’s finally died a week or so ago, I put in some HARMA 5881 cryo’d valves from Watford Valves in the UK that I bought to try in my Leben CS-600 integrated amplifier way back when.

I don’t recommend you substitute 5881’s into an amp designed for 6L6GC’s unless you are sure the amps don’t exceed the ratings of the 5881, as a lot of modern amps calling for a 6L6GC tube will exceed 5881 ratings, which can cause them overheat or arc over.

Given I didn’t have any other 6L6GC’s to try at the time, I went with the 5881’s until some new tubes arrived.

The HARMA cryo’d 5881’s actually sounded quite a lot like the GE 6L6GC’s in the mid-range to me on first listen, but after a couple of albums I became aware that they lacked the beautiful smoothness in the high-frequencies that the GE’s have in spades.

I decided to look over the less expensive new production 6L6GC’s out there to see if there was anything having a reputation of a smooth & warm tonal balance similar to the GE’s.

Tung-Sol 6L6GC-STR (left), GE 6L6GC (right).

As I was reading up on the current crop of 6L6GC’s, the Tung-Sol 6L6GC-STR kept popping up as being a smooth & warm sounding tube with a similar tonal balance to the GE’s.

Tung-Sol says their 6L6GC-STR’s “… are clones of the legendary Philips 6L6GC STR …” which I haven’t had any experience with.

The 6L6GC-STR has a black anode coating which is supposed to give it “a nice smooth, warm sound”.

I ordered two matched pairs ($44.50 per matched pair) of the Tung-Sol 6L6GC-STR’s from Jim McShane, who is one of my favorite tube suppliers on Planet Earth.

To put a little perspective on price, the quad of Tung-Sol 6L6GC-STR’s sell for less than the price of a single NOS GE 6L6GC, so from a cost perspective they’re a bargain if they perform similarly to the GE’s.

Tung-Sol 6L6GC-STR’s in my MC30.

I didn’t waste any time pulling out the 5881’s and putting the Tung-Sol 6L6GC-STR’s in their place.

MC30 with Tung-Sol 6L6GC-STR’s.

I proceeded to warm up the MC30’s while listening to a little NPR on the MX110Z’s FM tuner for a little bit.

It takes about an hour for MC30’s to warm up to the point where they’re at their musical & sonic best, but I couldn’t stand waiting that long, so after about 10 minutes I put Gillian Welch’s & David Rawling’s The Harrow & The Harvest on the Garrard and let ‘er spin!

The Harrow & The Harvest

Gillian Welch’s & David Rawling’s “The Harrow & The Harvest”.

I was immediately impressed with the Tung-Sol 6L6GC-STR’s in my MC30s, and the little buggers gave me goosebumps right off the bat with the way they portrayed Gillian’s & David’s vocals, with a sense of  immediacy & intimacy that I found very alluring.

It’s always a little dangerous to make statements based on first impressions, especially when the Mac’s aren’t even fully warmed up yet as I’m listening, and the tubes have zero hours on them, but I’m really liking what I’m hearing from these Tung-Sol 6L6GC-STR’s in my MC30s.

Fleetwood Mac “Black Magic Woman”.

When I was up visiting my buddy Chad at Lake Chelan in Washington State, he played Fleetwood Mac’s Black Magic Woman for me.

I was immediately smitten and ordered a copy of Black Magic Woman of my own from Discogs as soon as I got home!

As luck would have it, my order of Black Magic Woman from Discogs arrived at the same time as the Tung-Sol 6L6GC-STR’s, so I got to give it a listen today.

Black Magic Woman

Black Magic Woman was recorded back when Fleetwood Mac was a blues-rock band, before they morphed into the rock & roll band of later times with the addition of Lindsey Buckingham and Stevie Nicks. This might very well be my favorite Fleetwood Mac album.

Black Magic Woman on the CTC Garrard.

My buddy Chad has superb taste in rock & roll music, and Fleetwood Mac’s Black Magic Woman is a must have if you love blues and rock & roll!

Tung-Sol 6L6GC-STR power tubes in the MC30.

But I digress, as this post is supposed to be about the Tung-Sol 6L6GC-STR’s!

I really like the Tung-Sol’s. They come across as naturally musical, warm and smooth, transparent and nuanced, with a nice sense of the musicians’ touch on the instruments. and as I mentioned earlier, they have a really nice way with vocals.

I don’t think these Tung-Sol 6L6GC-STR’s sound like the GE 6L6GC’s exactly, but they’re pretty much in the same league, and in some ways are better, based on my very preliminary listening impressions.

The Tung-Sol’s have more clarity & nuance than the GE’s, and are to the warmer & smoother side of life, like the GE’s. The Tung-Sol’s have an electrifying sense of presence about them that makes music sound exciting, which I like a lot.

The high-frequencies are smoother than the 5881’s, perhaps not as smooth as the GE’s, but more nuanced.

Time will tell, as they’re still brand new out of their boxes, but I like them a lot, and if they smooth out a bit in the upper mid-range & highs, they may very well turn out to be a desirable alternative to expensive NOS GE 6L6GC’s.

I’ll report back as the Tung-Sol 6L6GC-STR tubes get some more run-in time on them.

Day 2 Update

It’s Day 2 with the Tung-Sol 6L6GC-STR tubes in my vintage MC30 monaural amplifiers. I didn’t have time to get a lot more hours in on them, probably only about 7 hours more as I’m writing this.

I put back on the The Harrow & The Harvest for some listening as a baseline, and I continue to be impressed by the mid-range performance of the Tung-Sol 6L6GC-STR’s. They have really nice mid-range tone, with instrumental timbre that sounds very lifelike, and a very interesting acoustic space that wraps around voices and instruments to give them a sort of spooky & spacious presentation.

One thing that has improved noticeably even in this short amount of time is the Tung-Sol’s ability to convey tempos (and changes in tempos), and an increasingly dynamic prowess that makes melody lines become more exciting and engaging.

The Tung-Sol’s upper mid-range sounds a little peaky & edgy in places on a number of albums I’ve listened to that sounded natural with the GE’s (some vocals and muted trumpets, for example).

I’d like to hear a little more smoothness in the upper mid-range out of the Tung-Sol’s, so hopefully they’ll smooth out with more run-in time, as that’s the only significant criticism I have of them at this point.

With that little bit of edginess as an exception, the Tung-Sol’s are right in there in overall performance with the black plate RCA 6L6GC’S and the gray plate GE 6L6GC’s, which are arguably the cream of the NOS crop of 6L6GC’s.

I should say that I’ve made enough changes to the Westminster system lately that it’s possible that the slight upper mid-range edginess/dryness I’m hearing could be due to one of those changes rather than the Tung-Sol’s, so a little investigation is in order to check out that possibility.

More to come …

As always, thanks for stopping by, and may the tone be with you!

 Posted by at 2:16 pm

  31 Responses to “Tung-Sol 6L6GC-STR Vacuum Tubes. Update.”

  1. Hey Jeff!

    I love the tung sols. I’ve used them in all the 6L6GC based amps I’ve owned, including my current MC30s. Though now, I’m using some vintage Sylvania’s that are good…but just not as good as the tung sols. The tung sols have also lasted what seems like forever. Super durable.

    Looking forward to hearing more feedback from you! Given the stigma around new production tubes vs NOS, I’ve been slightly embarrassed to voice my love for the Tung Sols… lol.

    • Hi Tysen,

      The Tung-Sol’s are impressive, and I’m looking forward to how they’ll develop with a little more run-in time.

      NOS tubes can be really good (like the GE’s), but there’s no reason that new production tubes can’t be just as good or better. So far that’s only been true in a few cases, but as companies pay more attention to what customers want (warm, rich, and dimensional sounding tubes), I suspect we will see some really fine tubes as new production.

      Already the 300B, 274B, and EL34-ST, offered by Sophia Electric are in this category, but it’s nice to hear inexpensive new production tubes with a similar sort of tonal balance. It bodes well for the future!

      Kind regards,


      • Hopefully Sophia Electric will make 6L6GCs in the near future!

        Do the Tung Sol 6L6GCs sound similar to the 6L6Gs you wrote about a while back? thetubestore.com says that “the internal assembly is almost identical to the 6L6GC STRS.” I’ve wanted to try the 6L6Gs, but if they’re the same tube as 6L6GCs, it’s hard to justify the extra money for prettier glass.

        FYI, you should try out the Tung Sol 12AX7s next! I think they sound lovely.


        • Hi Tysen,

          The Sophia Electric EL34-ST’s are really nice in the Leben CS-600, but as far as I know, SE doesn’t have plans for a 6L6GC.

          One of my 6L6G tubes failed after a short time, so I have never pursued them further.

          Kind regards,


  2. Hi Jeff,

    I used MC30 with KT66 GEC “clear top brown base”.
    I liked midrange and tone with these tubes. But I newer used other output tubes in MC30. So I can’t compare KT66 to other tubes …
    But, I did tube rolling with other tubes in my MC30.
    The most impresive tube that I tried was 12BH7 Mazda.
    I used Telefunken smooth plate input 12AX7, Mulard driver 12AX7 and Amperex BB 12AU7.
    Billie Holiday voice and piano tone reproduction was uncomparable.
    I regret that I sold this amplifier.


    • Hi Alex,

      The MC30’s are really something special, and I’m glad my buddy Leo put me onto them way back when. Now it seems nearly all my friends have a pair of MC30’s in their systems!

      The MC30’s have musical qualities that very few amplifiers can match, and even with all the amplifiers that have passed through here, there’s very few that I have thought could approach the MC30’s in terms of overall tone, emotional involvement, and sheer musicality.

      Kind regards,


  3. Hi Jeff, do you plan to try in your Leben?


    • Hi Peter,

      I don’t really have plans to do that at the moment. With all the upcoming reviews I have in the works, plus my satisfaction with the Sophia Electric EL34-ST tubes I have in the Leben right now, it probably won’t make it to the top of the to-do list.

      One nice thing about the Tung-Sol 6L6GC-STR tubes in the Leben CS-600 would be their short height, which would allow the use of the Leben’s top cover, which I can’t do with the EL34-ST’s.

      Kind regards,


      • Sorry Jeff a little bit out of topic can you please help me here I am thinking of Leben route or Shindo what would you say the difference between the two I know it is a stupid question because it all depends on the speakers also the problem is I can’t demo these products in person and since I trust your taste in hifi if you can help me out Thank you

        • Hi Dimitris,

          It all depends on what sort of sound you prefer. The Shindo gear is very nice, and my recollection is that it has a warmer & richer nuevo-vintage sort of presentation, which endears it to a lot of enthusiasts. The Leben is a more of a contemporary presentation, that is a little leaner and more extended in the high-frequencies.

          I hope that helps!

          Kind regards,


          • Hi Jeff,

            I will continue out of topic questions…

            I had EAR 834P (active RIAA) and Croft (passive RIAA) phono stages. I preferred EAR sound. It was more all-in-one and more musical.
            As result I built by myself phonostage based EAR scheme but with much better quality parts and power supply.
            But so many people blame EAR and other classic phonostages active RIAA schemes.
            Maybe my decision was wrong?

            Can you explain what is the difference between well designed active RIAA like McIntosh and passive (without feedback) like Leben?
            And what kind of RIAA scheme used Shindo.


          • Hi Alex,

            I do not know what kind of phono stage design the Shindo preamp’s use, so I can’t be of much help there.

            As far as classic phono stage designs go, I’m definitely not an expert, but I can share with you what Hyodo-san (of Leben) told me when back I wrote about his RS30EQ phono stage:

            Hyodo-san divides classic valve phono stages into two basic design genres: those like the Marantz Model 7 that use negative feedback (NFB) to achieve RIAA phono equalization; and those like the Harman Kardon Citation IV that use no NFB, and use capacitors and resistors (CR) to achieve RIAA equalization (and which Hyodo-san considers to be “a masterpiece” of phono preamplifier design).

            The vintage Marantz Model 7 uses three stages of 12AX7 amplification for RIAA equalization where NFB is applied from the 3rd stage cathode to the 1st stage cathode. Hyodo San says the good points of the NFB type equalization as used in the Marantz are that it’s easy to get a good signal-to-noise ratio; it doesn’t require high gain; and it isn’t very sensitive to tube quality. He says the downside of the NFB approach is that the impedance at high frequencies becomes very low which gives a hard and dry sound that negatively affects musicality.

            The downside of the vintage Harman Kardon Citation IV style of CR equalization is the need for high gain and a dependence on very high quality tubes. Implementation is also more difficult than with NFB designs because the tubes are directly amplified, and only the finest can be used. Hyodo San feels that the difficulties of the CR type of equalization are worth the extra design trouble because it is so stable in the high frequencies, which provides superior musicality by being much more transparent, and more natural and involving sounding.

            As you would expect, Hyodo-san designed the Leben RS-30EQ phono preamplifier as a zero negative feedback CR RIAA equalizer in the spirit of the classic Harman Kardon Citation IV.

            After having listened to quite a lot of phono stages, I do concur that the HK Citation IV is a wonderful sounding design, as is the RS30EQ which is inspired by the HK.

            I would trust your ears. If you like the way a phono stage with negative feedback sounds in your system the best, it is the best for you.

            I hope that helps!

            Kind regards,


          • Hi Jeff,

            Thank you for interesting information.

            Did you compare McIntosh MX110Z RIAA to RS30EQ?


          • I haven’t directly compared them, Alex.

            I do use both routinely and enjoy them, however.

            Kind regards,


          • Hi Jeff,
            One day I will try Duelund JAM capacitors in my phono stage instead of Audio Note copper.
            I think it will improve general transparency of my phono stage.

          • Hi Alex,

            Thank you for reporting on the Duelund JAM cap’s. My experience has been limited to trying the Duelund tinned-copper prototype capacitors in my MX110’s cathode follower and the HF crossover of my Altec A5’s, where they were remarkable in both clarity and naturalness.

            I forgot to mention that on the phono stages, for either type, that perhaps what makes more of a difference than topology is the way a given manufacturer voiced it to work with their associated equipment. So while both the Leben RS30EQ and MX110’s phono stage sound great in the context of their, those companies have voiced them to work well with their associated equipment, but I haven’t really tried them outside of the the context of their associated equipment.

            However having said that, my favorite phono stage that I have is the New Valve Order SPA II phono preamplifier, which for my tastes bests both the MX110 & RS30EQ phono stages, and its MC setting has enough gain so a SUT is not needed, which is really nice.

            You can read more about it HERE.

            The NVO SPA II combined with the SPEC RSA-M3 EX Real Sound Amplifier makes for a really beautiful sounding presentation with my Westminster’s, for example.

            Anyways, have fun!

            Kin regards,


          • Hi Jeff,

            Thank you for a link to NVO.

            Because my phono stage it is my DIY project I did it voicing by myself.
            I don’t have such huge expirience like Hyodo-san or Yazaki-san, but I tweaked my phono stage a couple of times. I and my friends liked a final result.
            The sound is “analog” in good meaning of this word and sound tone is fine.
            I’m just always looking for to improve my sound.


          • Hi Alex,

            I think your approach is a good one!

            Kind regards,


          • I forgot to mention, that my phonostage project was inspired by Romy the Cat’s “End of Life Phonostage”.

          • Hi Alex,

            I hadn’t heard of the End of Life Phonostage project before, so I looked it up.

            Looks nice!

            Kind regards,


  4. Thank you very much Jeff

  5. Hi Jeff,

    Since the MC30 amps showed up at your place, I have loved the deep rich dark smooth character which I thought was the character of the amp. Then, at a time when George was on travel, I borrowed George’s MC30 amps for an extended listening. George had the GE 6L6GC tubes like the ones in your MC30 amps. Once again I perceived the rich dark smooth character, which I attributed solely to the amp. So I bought a pair of Mac MC30 amps from Yves Beauvais.

    My MC30 amps came with Russian Tung Sol tubes 6L6GC power tubes. My initial reaction to the Russian Tung Sol tubes was that maybe the GE tubes had been too dark, and euphonic, and not sufficiently articulate. It was not long, though, until GE tubes were back in the amp, where they remain. I just love the magic of the GE 6L6GC tube.

    I’m not sure my Russian Tung Sol 6L6 GC STR tubes ever got fully broken in. It will be interesting to hear whether you find improvement with break in time. Perhaps the Russian tubes will rise to the magic of the GE version with sufficient break in.
    All of the GE 6L6GC tubes I have used have been pre-owned, and fully broken in.

    Over this last weekend I had a chance to hear Harry’s Klipschorns (he is using Eliptrac mid and high frequency horns) with the illustrious Altec Lansing 1750B amps which use RCA 811 tubes. One hundred sixty five watts of dead quiet triode power into one of the most efficient speakers ever made. Although Harry’s Klipschorns sounde great. The 811 amp pretty much blew away a very good sounding pair of 807 push/pull amps. It is surprising how uncolored and articulate the Harry’s 1750B amps are, very clean and articulate, but not with the nasty stuff that normally comes along with articulate amps. The system sounded just very natural, with a magnificent, transcendent and majestic ease. Quite a contrast to the dark euphonic magical sound I am used to with the MC30 amps using GE 6L6GC tubes.

    It will be interesting to see how I feel about the MC30/GE 6L6GC sound compared to the 1750B sound as time goes by. The wonderful thing about the MC30/GE 6L6GC sound is how good it tends to make each and every record sound. Generally speaking, I can’t wait to turn the system on and get into the music. That said, it would be nice to have a pair of 1750B amps to play around with.

    I look forward to hearing your Westminster system with the Russian tubes in the MC30 amps.

    Best Regards,

    • Hi Pete,

      Thanks for sharing the adventure with Harry and the Altec 1750B amplifiers, it sounds like you had fun! The Altec 1750B amps vary all over the place price-wise, depending on their condition, but I’d love to hear them one of these days!

      What the Tung-Sol 6L6GC-STR does well it does very well, but so far it hasn’t been able to match the GE’s in the upper mid-range and high-frequencies, which is the critical region for my Tannoy’s to perform well.

      Time will tell …

      Kind regards,


  6. Hi Jeff !!!!

    I have a Leben CS600 with a 25th Diapason Adamantes speakers and the treble is a bit hard for my personal taste.
    I want to replace the tubes with others that soften the treble a lot.
    And I’ve thought about the EH KT90 and the Tung Sol 6L6G.
    What do you recommend?

    Kind regards and thanks very much

    • Hi Fernando,

      Unfortunately, quite a lot of contemporary loudspeakers have a forward and hard treble, which is not easy to address with anything short of replacing the speaker with something a little more natural sounding.

      The Leben CS600 is a fairly neutral integrated tube amplifier that is at its best with warmer and more natural sounding loudspeakers, so it may be difficult to get a happy match with the Diapason’s.

      However, the EH KT90 tubes provide the warmest presentation from the CS600 that I have been able to get from it, so that may help.

      Another possibility is adding in L-pads to the Diapason’s crossovers so you can turn down the amount of high-frequency energy, so that may be worth considering too, and is an inexpensive fix.

      Let me know if you are able solve this issue to your satisfaction.

      Kind regards,


      • Hi Jeff.

        But the Tungsol 6L6G have not tried them?
        They say that its main characteristic is warm sound and very soft trebles.

        The Diapason Adamantes I have associated with several amplifiers (Jadis i35, Unison Research S6, Puresound A30, Mastersound Dueventi, Moon 600i) and there was no hard treble. They are quite neutral speakers, warm and natural, suitable for classical music and jazz.

        Thank you very much for your advice

        • Hi Fernando,

          I have tried the Tung-Sol 6L6G, but I thought my GE 6L6GC tubes outperformed them by being warmer, richer, smoother, and just more musically engaging. The Tung-Sol 6L6G tubes also proved to be unreliable, and after one failed early I’ve never used them again.

          I hope that helps.

          Kind regards,


  7. Hello Jeff

    and what do you recommended in pre-valves 6CS7?
    Sylvania, FIVRE, RCA, Raytheon…….?


    • Hi Fernando,

      My favorites are NOS Sylvania’s, they match my system balance and tastes the best.

      Kind regards,


      • Hi Jeff.

        Currently it is difficult to find Sylvania 6CS7.
        I search without stopping and I can not find for sale.
        Do you know any particular place where there is a sale?



        • Hi Fernando,

          The last place I bought Sylvania 6CS7’s was at Radio Electric Supply (http://www.vacuumtubes.net/).

          I don’t know if they currently have them in stock, but they usually have a nice supply of NOS 6CS7’s from various producers.

          Kind regards,


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