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    Chinese 6SN7 tubes

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    deepee99

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    Chinese 6SN7 tubes

    Post by deepee99 on Tue May 10, 2016 3:20 pm

    We've danced around the topic of 6SN7 tubes and their Chinese CV-181 drop-in replacements on other threads but thought it worthy of a new thread.
    I have a pile of antique 6SN7s (name the American, European or Russian brand, I've probably got a pair). At least in the octal iterations of the SP-14 and M-125 drivers, the Chinese PSVanes and Shu Guang Black Treasures will blow the doors off anything in the inventory. They take several dozens (some say hundreds) of hours to fully develop, but even out of the box they are amazing. Muddy at the top for the first few hours, but at start-up produce a nuanced, detailed bass that doesn't go away as the mid and treble ranges develop. A caution: the PSVanes, at least in the octal driver slots of the M-125s, do generate a hum when new. This may go away as I burn them in in the SP-14. They are dead silent in the SP-14. The Black Treasures have no issues in the M-125 driver slots and are great in the SP-14, but damn near twice the money as the PS Vanes.
    Either tube is a fraction of the price of a rare U.S. 6SN7, and worthy of consideration. Prices are climbing daily.
    One danger, Will Robinson, Beware: these are huge tubes. They may not fit into your enclosed preamp cabinet and are virtually touching each other on the sides -- the latter is no problem but you may need to take the lid off the SP-14 to accommodate their height.
    Unless I see one or more fail at the 500-hour point, these are going to be my go-to preamp and driver tubes.

    Kentley

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    Re: Chinese 6SN7 tubes

    Post by Kentley on Tue May 10, 2016 5:50 pm

    Deepee and I have communicated extensively concerning these Chinese tubes, and my experiences mirror his, though I've yet tried only the ShuGuangs. In the SP-14, there is NO clearance at the tops of these monsters. Easy solution - leave one screw in place at the front of the cover, and wedge up the rear (the metal is flexible enough to do this without any damage to the mounting holes). It may not even be necessary, as these tubes run super-cool (max measured at 85 F!).
    As a center driver in the ST-120, the ShuGuang gives the illusion that you've just moved your magically larger speakers into a magically larger room. It's that dramatic. The difficulty here is the necessity of using an adaptor, increasing the likelihood of pin contact issues. I wonder if a more permanent solution might be had by replacing the socket outright, or at least soldering the adaptor in place. Anyone?
    At any rate, the ShuGuang-as-driver with adaptor towers above all else, so using the brown Dynaco cage is out of the question.


    Last edited by Kentley on Tue May 10, 2016 7:36 pm; edited 1 time in total

    Tube Nube

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    Re: Chinese 6SN7 tubes

    Post by Tube Nube on Tue May 10, 2016 7:19 pm

    Kentley, why do you need an adaptor? Is it for better clearance, or are you running a 12AU7 driver board, rather than the octal driver board?

    Kentley

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    Re: Chinese 6SN7 tubes

    Post by Kentley on Tue May 10, 2016 7:31 pm

    Tube Nube wrote:Kentley, why do you need an adaptor? Is it for better clearance, or are you running a 12AU7 driver board, rather than the octal driver board?
    I'm using the 12AU7 board. As far as I know, an octal board has not been made available by VTA for the ST-120.

    Tube Nube

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    Re: Chinese 6SN7 tubes

    Post by Tube Nube on Tue May 10, 2016 8:06 pm

    I guess I just assumed the octal board could be used on both. I know our friend Don (check dsachsconsulting.com) offers a custom ST 120 using the octal board and torroidal transformers. I'm saving my pennies hoping to have him build one for me this year.


    Last edited by Tube Nube on Tue May 10, 2016 8:08 pm; edited 1 time in total

    Tube Nube

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    Re: Chinese 6SN7 tubes

    Post by Tube Nube on Tue May 10, 2016 8:07 pm

    I think I'd like mine with. mullard GZ33 or 37 rectifier, though. Just can't get over my Mullard envy.

    arledgsc

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    Re: Chinese 6SN7 tubes

    Post by arledgsc on Wed May 11, 2016 9:55 am

    Kentley wrote:
    Tube Nube wrote:Kentley, why do you need an adaptor? Is it for better clearance, or are you running a 12AU7 driver board, rather than the octal driver board?
    I'm using the 12AU7 board. As far as I know, an octal board has not been made available by VTA for the ST-120.

    Look here mid page!   tube4hifi 6SN7 board

    arledgsc

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    Re: Chinese 6SN7 tubes

    Post by arledgsc on Wed May 11, 2016 10:15 am

    The Black Treasure CV-181s can be really expensive.  Last year I purchased two BT CV-181s from Ebay seller "hanshare-electronics".  Good, respected Chinese seller who has been in business for several years.  Paid less than $150 for the pair.  The first one has been going strong for a while and the 2nd still in the box.  So look around.

    deepee99

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    Re: Chinese 6SN7 tubes

    Post by deepee99 on Wed May 11, 2016 10:42 am

    I've had good luck from the Chinese eBay sellers.
    I think my first pair of Black Treasures was just north of $100; I just picked up a quad of them for $250. The PSVanes run about $100 a pair. Not been burned yet, and some of the sellers even send a thank-you note and a follow-up query to make sure you got them and they're OK.
    Only problem is they generally take about a month to get here.

    Kentley

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    Re: Chinese 6SN7 tubes

    Post by Kentley on Wed May 11, 2016 11:24 am

    arledgsc wrote:
    Kentley wrote:
    Tube Nube wrote:Kentley, why do you need an adaptor? Is it for better clearance, or are you running a 12AU7 driver board, rather than the octal driver board?
    I'm using the 12AU7 board. As far as I know, an octal board has not been made available by VTA for the ST-120.

    Look here mid page!   tube4hifi 6SN7 board

    Octal board referred to is for VTA ST-70 only. As far as I know, it is not usable in ST-120.

    deepee99

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    Re: Chinese 6SN7 tubes

    Post by deepee99 on Wed May 11, 2016 2:24 pm

    Kentley wrote:
    arledgsc wrote:
    Kentley wrote:
    Tube Nube wrote:Kentley, why do you need an adaptor? Is it for better clearance, or are you running a 12AU7 driver board, rather than the octal driver board?
    I'm using the 12AU7 board. As far as I know, an octal board has not been made available by VTA for the ST-120.

    Look here mid page!   tube4hifi 6SN7 board

    Octal board referred to is for VTA ST-70 only. As far as I know, it is not usable in ST-120.
    I think Skizo is using adapters for 6SN7s on his noval 120. Again, the ShuGuangs and PSVanes are huge tubes, much bigger than the old RCA editions, bordering on KT-88 size, and with the pin-and- volt adapters would probably not fit in even a a jerry-rigged stock case, but with the open-air ST-120 and M-125s, no worries except at the socket level if you're up-converting from novals. Make sure there's room for the adapter. As both the PSVanes (which are a tad smaller) and Black Treasures burn in they continue to amaze. Our Chinese friends are on to something and what continues to amaze is how cool they run. You can put your hand on top of them after an hour's running and feel warmth, not heat, and they pull no more amps out of the wall than antique NOS tubes. 
    If these babies can hold up for a couple thousand hours we're looking at a $300 tube.

    Bob Latino
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    Re: Chinese 6SN7 tubes

    Post by Bob Latino on Wed May 11, 2016 4:43 pm

    Kentley wrote:

    Octal board referred to is for VTA ST-70 only. As far as I know, it is not usable in ST-120.

    I do not use or recommend the octal board for any of the VTA amp kits. I am not saying that they will not work in the VTA amps ... They will but IMHO they have no "superior sound quality advantage" over the noval board. The amp may sound "different" but that does not mean it will sound "better".

    Large USA tube amp manufacturers like McIntosh and Conrad Johnson have never used octal driver tubes in any of their amps. A few years ago McIntosh came out with their statement tube amp - the MC2301 300 watt per channel monoblock amps. These amps cost $22,000 a pair. At that price they could have chosen any driver circuit for best sound. Each 300 watt monoblock uses two 12AT7 (noval) driver tubes .. You can see the two 12AT7 driver tubes in the photo below. This single channel monoblock amp uses EIGHT 6550 (or KT88) output tubes and the two 12AT7's as driver tubes.



    Octal tubes have a disadvantage. Each 6SN7 (octal tube) will use double the current of its noval twin, the 12AU7. A 12AU7 uses .30 amps and a 6SN7 uses .60 amps .. You multiply that extra .30 amps by three tubes and you wind up with an extra .90 amps the power transformer will have to draw. This near 1 extra amp will add up to a noticeable amount of extra heat on any amp that uses octal drivers.

    Bob

    deepee99

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    Re: Chinese 6SN7 tubes

    Post by deepee99 on Wed May 11, 2016 5:00 pm

    Bob, I feel insulted.
    VTA amps are far superior to Macs. Please do not compare them in the same sentence Smile

    Kentley

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    Re: Chinese 6SN7 tubes

    Post by Kentley on Wed May 11, 2016 5:10 pm

    In my particular (or perhaps "peculiar") case, I've only replaced the center driver with a 6sN7, while leaving the two 12AU7 inverters. Therefore the increased current draw is only .30 amps. Measurements of the power tranny temp measured no increase whatsoever in operating temp.
    As far as SQ goes, for me the difference is welcome and noticeable - it's LARGER.
    For me, the downside is the extreme variability of the 6SN7 clan. They tend to be noisier and more microphonic. But from tube to tube - even of the same brand, build, and vintage, they can exhibit a whole range of quirks. Not great for the plug-and-play folks at all.

    Bob Latino
    Admin

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    Re: Chinese 6SN7 tubes

    Post by Bob Latino on Wed May 11, 2016 6:28 pm

    Kentley wrote:
    For me, the downside is the extreme variability of the 6SN7 clan. They tend to be noisier and more microphonic. But from tube to tube - even of the same brand, build, and vintage, they can exhibit a whole range of quirks. Not great for the plug-and-play folks at all.

    Kentley,

    I am glad you mentioned that .. I too have found over the years in experience with 6SN7 type tubes that (maybe because the elements inside the tube are physically larger?) they tend to be more microphonic and/or noisy when compare to a 12AU7 ..

    Bob

    deepee99

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    Re: Chinese 6SN7 tubes

    Post by deepee99 on Wed May 11, 2016 9:29 pm

    Bob Latino wrote:
    Kentley wrote:
    For me, the downside is the extreme variability of the 6SN7 clan. They tend to be noisier and more microphonic. But from tube to tube - even of the same brand, build, and vintage, they can exhibit a whole range of quirks. Not great for the plug-and-play folks at all.

    Kentley,

    I am glad you mentioned that .. I too have found over the years in experience with 6SN7 type tubes that (maybe because the elements inside the tube are physically larger?) they tend to be more microphonic and/or noisy when compare to a 12AU7 ..

    Bob
    I've had a few microphonic novals, too. IMHO, unless you're banging them with a pencil or table-dancing on top of them, the only annoyance they give is when you're flipping the selector switches. Maybe I've been lucky but for me microphonics has been a non-issue in terms of sound quality. Two of my new Chinese 6SN7s will give a nice chime if you thwack them hard enough but left alone their sound quality is the same as their brethren. My larger concern with the Chinese tubes is, Will they last? I would think with their huge size and getter-flashing mass, and their cool operating temps, they might just well.


    Last edited by deepee99 on Wed May 11, 2016 9:44 pm; edited 1 time in total (Reason for editing : diction)

    Maintarget

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    Re: Chinese 6SN7 tubes

    Post by Maintarget on Wed May 11, 2016 10:30 pm

    With a huge variety to choose from, low cost (For now) and .30A heater current wouldn't it be better to use 12SN7 tubes?
    I'm using smoked glass RCA JAN CRC-6SN7-gt VT-231in my SP-14 had one that was making a hell of a racket swapped out with another and wow!
    I am seriously considering going the adapter route on the center driver tube on my ST-120 and trying some 6SN7

    sKiZo

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    Re: Chinese 6SN7 tubes

    Post by sKiZo on Thu May 12, 2016 2:06 am

    Bigger is ALWAYS better, right?



    I'm thinking this is the longest I've gone without rolling a tube ... and not really having any desire to. Just a sweet mellow sound with the current set.

    arledgsc

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    Re: Chinese 6SN7 tubes

    Post by arledgsc on Thu May 12, 2016 11:03 am

    sKiZo wrote:Bigger is ALWAYS better, right?

    I'm thinking this is the longest I've gone without rolling a tube ... and not really having any desire to. Just a sweet mellow sound with the current set.

    Looking good there Skizo.   How much heat is coming off the power transformer?   Seems you have a lot of heater power demand.

    deepee99

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    Re: Chinese 6SN7 tubes

    Post by deepee99 on Thu May 12, 2016 11:18 am

    arledgsc wrote:
    sKiZo wrote:Bigger is ALWAYS better, right?

    I'm thinking this is the longest I've gone without rolling a tube ... and not really having any desire to. Just a sweet mellow sound with the current set.

    Looking good there Skizo.   How much heat is coming off the power transformer?   Seems you have a lot of heater power demand.
    You'd think so, but maybe not. Heater current doesn't necessarily increase with the size of the tube.

    Tube Nube

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    Re: Chinese 6SN7 tubes

    Post by Tube Nube on Thu May 12, 2016 11:51 am

    I wouldn't mind hearing those MacIntosh mono bludgeons, though I don't guess I'd be so impressed as to want to turn my back on the present Dyna-sty of the mighty Dynakit lineage. It would just be neat to hear what spending 10 times the dough gets you.

    It's an interesting discussion about octal tubes. I can't contribute in a technical way, but only my observations that there's certainly a contemporary shift in a segment of our hobby toward embracing these tubes. I've often read that they are more prone to microphonics -- a downside -- but bring a "lusher" and/or warmer sound, which, as Bob has said, is different but not necessarily better. Elsewhere, I've read that the 6SN7 type tube is a much better tube, by design, for audio, than "the small signal tubes" (12xx7 types?), but I didn't get any understanding so far of what it is about those tubes that that assertion was based on. I'd be interested to hear it, in not too technical lingo, if anyone knows a basis for this claim.

    It's nice that, after just a few short years of Roy and Bob putting up their website and this forum, we have so many good choices in equipment. I don't know how many people I've steered in this direction, but I take every opportunity to do it, because I know they won't get stung. Or burned. They'll just have their miss conceptions from other sites rectified.

    Tube Nube

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    Re: Chinese 6SN7 tubes

    Post by Tube Nube on Thu May 12, 2016 12:21 pm

    http://www.effectrode.com/signal-tubes/the-6sn7gt-the-best-general-purpose-dual-triode/

    An interesting article on the 6SN7 and its history!

    deepee99

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    Re: Chinese 6SN7 tubes

    Post by deepee99 on Thu May 12, 2016 2:13 pm

    Tube Nube wrote:http://www.effectrode.com/signal-tubes/the-6sn7gt-the-best-general-purpose-dual-triode/

    An interesting article on the 6SN7 and its history!
    Good stuff! Thanks, Nube.
    IIRC, the highly coveted Red Base RCA 6SN7s (5692) are a little hard on VTA iron -- the filaments pull more current than the GTAs and GTBs. Not tried them and don't intend to.
    Cheers,
    d

    sKiZo

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    Re: Chinese 6SN7 tubes

    Post by sKiZo on Thu May 12, 2016 2:50 pm

    arledgsc wrote:
    Looking good there Skizo.   How much heat is coming off the power transformer?   Seems you have a lot of heater power demand.

    Haven't gone gung ho with the temp probe yet, but I have checked a time or two after an ... "energetic" session, with no seemingly significant increase in btu's. At least it passes the "putting a finger on the iron and not leaving a couple layers of skin" test.

    All the tubes used present a heavier load than normal, but no issues so far. Probably helps that I run the thing at around 116vac courtesy of my lil bucker ...



    ... and I'd think the additional ventilation on the chassis plate helps a bunch.

    Also worth mentioning, I ran the KT120's for a long time at 60mV each, and have backed that down to a more typical 55mV. At one point, the higher bias provided more bottom end punch, but that doesn't seem to be the case now that the tubes are well broken in.

    On the flip side, I don't expect that my usual heaping helping of dbx bass synth and expansion help the heat situation any, but the amp should be used to that by now ... ;-}

    BTW ... is it just me, or does the adapter make this tube look like a bowling trophy?



    deepee99

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    Re: Chinese 6SN7 tubes

    Post by deepee99 on Thu May 12, 2016 3:26 pm

    Skiz,
    Back 'em off to about .45 or .50 and see what happens. That seems to be the magic number for KT-88s.

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