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    7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

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    wantech

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    Join date : 2017-09-26

    7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by wantech on Thu Oct 12, 2017 12:43 pm

    Thinking of replacing the pc board on my st70, learn that there are many different one

    would like to know which one will be better.... the best......

    7199 vs 6gh8 vs 12au7 vs 6sn7

    thanks
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    Bob Latino
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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by Bob Latino on Thu Oct 12, 2017 1:22 pm

    wantech wrote:Thinking of replacing the pc board on my st70, learn that there are many different one

    would like to know which one will be better.... the best......

    7199 vs 6gh8 vs 12au7 vs 6sn7

    thanks

    Just my opinion but with a STOCK Dynaco ST-70 I would get a new VTA driver board that uses 12AU7 driver tubes. 7199 driver tubes are not made anymore and tend to be expensive now. Yes, you can use a 7199 to 6GH8 adapter on the stock driver board and use the less expensive 6GH8 driver tubes.

    12AU7 and 6SN7 tubes have basically the same characteristics but a 12AU7 is a noval (9 pin) tube and a 6SN7 is an octal (8 pin) tube. Consider these two reasons to favor the 12AU7 board.

    1. 6SN7 tubes draw double the current of a 12AU7 (6SN7 = .6 amps per tube and 12AU7 tubes = .3 amps per tube) Multiply this by the 3 tubes on the driver board (.3 amps X 3) and you get .9 amps extra current draw from the 6SN7 board from a STOCK Dynaco PA-060 power transformer that already runs hot and is already marginal with its ability to provide current for the amp. With three 6SN7's in there, the amp will run even hotter.

    2. 12AU7 tubes are more plentiful and cheaper to buy. There are still many USA made 12AU7 tubes out there. You can also use the military industrial versions of the 12AU7 the 5963, 5814 and 6189. You can also use the 12BH7 on the VTA noval board. USA made 6SN7 tubes tend to be more expensive.

    Some who have the 6SN7 octal version of the VTA driver board will say "it sounds better" but personally I don't hear it ? Large USA manufacturers of tube amps like McIntosh and Conrad Johnson have never used octal driver tubes. A few years back McIntosh came out with their new statement tube amp - the 300 watt MC2301 monoblock amps. These amps are $22,000 a pair. At that price they could have chosen ANY driver circuit/driver tube for "best sound". Each MC2301 amp uses two 12AT7 (noval - 9 pin) driver tubes.

    Bob
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    Peter W.

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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by Peter W. on Thu Oct 12, 2017 1:34 pm

    Opinion Here:

    a) The 7199 is a triode/pentode - a bit more refined and a bit more complex than the two dual triode options.
    b) Whereas the Russians were making them briefly (and, typically, not very well), they are no longer. Meaning that *new* replacements are not available at the present moment.
    c) There were many thousands of them made, and they were used in many different amps from many different manufacturers. So the expectation is that they will remain available - albeit at an increasing cost - into the foreseeable future.
    d) A great many of these tubes are either microphonic, or distort to a greater-or-lesser degree depending on use and age.

    Cutting to the chase: If you have a good supply of 7199s in good condition that are neither microphonic nor distorting, it is my opinion that they are superior to the dual-triode options, if only just. You also have one less filament than with a three-tube configuration and far less current used than with an octal configuration.

    Now, moving on to the 6GH8 - another 'orphan' tube to my knowledge, but one that enjoyed much higher production back in the day, and so might be easier to find and at a better price. I am told (and my one example using same does not refute or support) that the 6GH8 has fewer problems than the 7199.

    Writing for myself - I have a lifetime supply of NIB/NOS RCA-branded 7199s (6), and three amps presently in operation that use them. In my case, I would therefore stick with the 7199s. As well, adapter plugs are available off-the-shelf to convert a 7199 board to 6GH8 use, meaning I am covered either way. In any case, with my vintage amps, I *would not* go with the octal option.

    Were I to advise in a vacuum, I would, in rank order: 1. 6GH8. 2. 7199. 3. 12XX7 x 3. 4. Any Octal option.

    Others will have different thoughts and advice - I am sure well, supported.

    eickmewg

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    Join date : 2014-08-29

    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by eickmewg on Thu Oct 12, 2017 3:41 pm

    There are highly regarded tube preamplifiers, e.g. Icon Audio, Cary, etc., that use 6SN7 tubes.  I am using a Black Treasure CV181 Z in the amplification position and, while an expensive tube, far exceeded a Platinum Mullard 12AU7-type tube, which was just about as expensive.  Maybe for an ST70, with original power transformer, octals aren't appropriate, but that is an amp-related and not a tube-related issue.
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    10-E-C

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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by 10-E-C on Mon Oct 23, 2017 4:14 am

    My wife was rummaging around in a garage sale this past week and called me, I found some vacuum tubes and they are 7199s, do you want them. Of course I replied to her. Two RCA black plates with big folded O-getter, NOS in box for .50 cents each. She did well!!!

    TM
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    PeterCapo

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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by PeterCapo on Mon Oct 23, 2017 9:16 am

    wantech wrote:Thinking of replacing the pc board on my st70, learn that there are many different one

    would like to know which one will be better.... the best......

    7199 vs 6gh8 vs 12au7 vs 6sn7

    thanks

    "Best" in what sense? Flexibility? Laboratory measurements? Sonic character? All of the options could result in different sonic character. Which one is "best" is according to your personal taste.

    More important than exactly which board to use is to first establish whether or not your current Stereo 70, perhaps decades old, is performing to its full potential. If you replace the PC board with a new PC board having all fresh parts (and perhaps likewise throughout your Stereo 70), of course it will likely sound "better" due to the fresh parts alone.

    wantech

    Posts : 8
    Join date : 2017-09-26

    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by wantech on Mon Oct 23, 2017 9:59 am

    10-E-C wrote:My wife was rummaging around in a garage sale this past week and called me, I found some vacuum tubes and they are 7199s, do you want them. Of course I replied to her. Two RCA black plates with big folded O-getter, NOS in box for .50 cents each. She did well!!!

    TM

    sure, I need a pair

    thanks

    wantech

    Posts : 8
    Join date : 2017-09-26

    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by wantech on Mon Oct 23, 2017 10:00 am

    wantech wrote:
    10-E-C wrote:My wife was rummaging around in a garage sale this past week and called me, I found some vacuum tubes and they are 7199s, do you want them. Of course I replied to her. Two RCA black plates with big folded O-getter, NOS in box for .50 cents each. She did well!!!

    TM

    sure, I need a pair

    thanks

    2 pairs

    thanks
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    deepee99

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    If you go the octal route . . .

    Post by deepee99 on Tue Oct 24, 2017 1:40 pm

    Consider the Chinese CV-181s in premium grade from Shu Guang or PSVane. They are very robust and sound to my ears better than any NOS 6SN7 or the noval equivalents.

    eickmewg

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    Join date : 2014-08-29

    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by eickmewg on Tue Oct 24, 2017 1:56 pm

    I'm with you on that, deepee99. Great tubes.
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    deepee99

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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by deepee99 on Tue Oct 24, 2017 2:39 pm

    eickmewg wrote:I'm with you on that, deepee99.  Great tubes.
    Their only drawback is they're as big as power tubes, so make sure there's room on the driver board. OTOH, they pull less heater current than most 6SN7s. The Chinese are on to something here, and their QC is as good or better than most other knock-offs or even NOS tubes, and the supply is steady. Best to order straight out of China or Hong Kong, figure on 8 weeks delivery, but I've never been stung yet.
    Downside: if you get a lame tube they'll honour their warranties, but shipping to and fro via China Post is prohibitive. Best just toss it and buy a new tube.
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    Kentley

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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by Kentley on Tue Oct 24, 2017 8:36 pm

    I must agree wholeheartedly with the deepee faction. Chinese production is on an upsurge, and it seems to be heralded by these very tubes. I currently am running five premium-quality "6SN7s" from the Chinese factories and they are unmatched by any others I've sampled. Cheap? No. Worth it? Yes.
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    tubes4hifi
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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by tubes4hifi on Wed Oct 25, 2017 2:40 pm

    to WanTech
    I'll post the same info here as I did in another topic, for those who don't read EVERYTHING on every post
    As to the sound of 7199, 6GH8, 12AU7, 6SN7 (and various other tubes used in other types of amplifiers)
    The ST70s from the 60s & 70s era used the 7199 tube because it was cheap and served a function. Same with the 6GH8.
    Most modern amplifiers use dual triode tubes like the 12AU7 as well as many other refinements in circuit design.
    Whether something costs $5 or $15 doesn't make a whole load of difference when you are talking about (let's just say) an $700 tube amplifier.
    Tube amplifiers of the 40s-70s era would be considered "tubey" sounding.
    Modern tube amplifiers, including any amplifier with VTA drivers, should not be "tubey" sounding (meaning, in general, flabby bass, rolled off low's and highs, warm midrange)
    but have a clean, clear, flat frequency response, and the main characteristic different from a transistor amp is in general more 3D, wider and deeper soundstage, holographic.
    Another characteristic of push-pull type tube amplifiers is that they have less even order harmonic distortion than a transistor amp, and have more odd order harmonics,
    which for most listeners seems to enrich the sound (harmonic enhancement). Also tube amps do not hard clip, in fact clipping is usually very difficult to hear in a tube amp,
    whereas in a transistor amp it is immediately apparent and extremely obvious.
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    deepee99

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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by deepee99 on Wed Oct 25, 2017 3:07 pm

    tubes4hifi wrote:to WanTech
    I'll post the same info here as I did in another topic, for those who don't read EVERYTHING on every post
    As to the sound of 7199, 6GH8, 12AU7, 6SN7 (and various other tubes used in other types of amplifiers)
    The ST70s from the 60s & 70s era used the 7199 tube because it was cheap and served a function.   Same with the 6GH8.
    Most modern amplifiers use dual triode tubes like the 12AU7 as well as many other refinements in circuit design.
    Whether something costs $5 or $15 doesn't make a whole load of difference when you are talking about (let's just say) an $700 tube amplifier.
    Tube amplifiers of the 40s-70s era would be considered "tubey" sounding.
    Modern tube amplifiers, including any amplifier with VTA drivers, should not be "tubey" sounding (meaning, in general, flabby bass, rolled off low's and highs, warm midrange)
    but have a clean, clear, flat frequency response, and the main characteristic different from a transistor amp is in general more 3D, wider and deeper soundstage, holographic.
    Another characteristic of push-pull type tube amplifiers is that they have less even order harmonic distortion than a transistor amp, and have more odd order harmonics,
    which for most listeners seems to enrich the sound (harmonic enhancement). Also tube amps do not hard clip, in fact clipping is usually very difficult to hear in a tube amp,
    whereas in a transistor amp it is immediately apparent and extremely obvious.
    Not to mention that an s/s amp clipping is a good way to send your tweeters or even woofs to the junkyard. Good way to check to see if the woofs have ever been clipping (when interviewing same) is the cone should move smoothly in and out with a gentle push of the hand. If you hear a scratchy sound, go down the block because the tweets are prolly shot, too, due to clipping.
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    Peter W.

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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by Peter W. on Wed Oct 25, 2017 4:33 pm

    Not to mention that an s/s amp clipping is a good way to send your tweeters or even woofs to the junkyard. Good way to check to see if the woofs have ever been clipping (when interviewing same) is the cone should move smoothly in and out with a gentle push of the hand. If you hear a scratchy sound, go down the block because the tweets are prolly shot, too, due to clipping.

    AMEN! What he wrote. YES!

    Not necessarily that clipping is the only possible cause of scraping, but that it takes surprisingly little clipping (10%, and very momentary is considered the absolute maximum) to do real damage, either instantly or cumulatively. Which is why, after about 60 watts or so, the next level is MANY, AKA Brute Force.

    Were I to 'tier' amps irrespective of type (tube or SS)

    SET or amps of 3-watts or less
    15-20 watts
    40-80 watts
    200+ watts

    SS-Only:

    40-60 watts
    200+ watts

    As already noted, tube amps clip softly, so amp power is more of a continuum.
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    Dynalover

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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by Dynalover on Thu Nov 16, 2017 8:52 pm

    tubes4hifi wrote:
    The ST70s from the 60s & 70s era used the 7199 tube because it was cheap and served a function.

    Could be wrong but I seem to recall reading 7199 was a relatively spendy tube, even then. It was designed specifically for audio, something that can't be said for some of the subs.
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    PeterCapo

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    Re: 7199 vs 6gh8 vs 12au7 vs 6sn7 for st70 ????

    Post by PeterCapo on Thu Nov 16, 2017 9:33 pm

    Dynalover wrote:
    tubes4hifi wrote:
    The ST70s from the 60s & 70s era used the 7199 tube because it was cheap and served a function.

    Could be wrong but I seem to recall reading 7199 was a relatively spendy tube, even then. It was designed specifically for audio, something that can't be said for some of the subs.

    It has been my understanding that 7199 was specifically designed for audio.  I found an RCA datasheet that so indicates.  Doesn't seem like the choice of the 7199 was solely a cost-saving measure.

    ****

    Follow-up... I recalled there was an interview with David Hafler a while back.  Found it.  He was specifically asked about the choice of tubes like 6AN8 and 7199.  Screen shot below, but if it is not easily readable, here is the Q&A that shows what Hafler said about it (bold face added for emphasis):

    "Did you use a combination driver tube to keep costs down?
    The combination driver tube was done initially because it was space saving and saved costs without sacrificing anything."



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