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which tubes for max clean headroom? truth or bull-oney about tubes?

Discussion in 'Amp Central Station' started by DjimiWrey, Jan 28, 2021.

  1. DjimiWrey

    DjimiWrey Tele-Meister

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    we're definitely on the same page.
    2011 i actually did have a twin chassis into a head;
    and bought the fantastic port city 2x12 slant cab
    loaded it with the 100 watt speakers from the first trademark 60s,
    before they switched to the inferior imao celestions....
    loved the sound; it was effin gorgeous and it fit well with the trios i was doing back in cali
    ... i'm finally throwing in the tone towel and "settling" for the scx2 in an extended combo cab with a 12" ragin cajun.. i reckon that'll work for the country dance hall house band gig
    they're image conscious and are gonna look at me sideways if i come in with a stack lol
    i'm 66 and have 16 screws in my spine but i'm not giving up... just scaling back
    y'all are awesome and i'm grateful for all the input
     
  2. teleman1

    teleman1 Friend of Leo's

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    Funny, I am 65 with a screwed up head!;) I might suggest an EQ pedal with what you are settling for,the xd has a loop right? You already know whats happening, all we did was concur.

    BTW,even though the inverter pre-amp thing is going on in the XD, I tried some ANOS in there and it certainly made a positive difference.
     
    Last edited: Jan 29, 2021
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  3. Obsessed

    Obsessed Telefied Silver Supporter

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    6L6 or go home.

    There is a reason the 6L6 uses more watts than a 6V6. Coincidence?

    If you are diming an amp for hours, then you have the wrong amp. IMHO.
     
  4. DjimiWrey

    DjimiWrey Tele-Meister

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    forgive me for asking, but what is/are ANOS?
     
  5. Wally

    Wally Telefied Ad Free Member

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    ANOS.....Almost new old stock.... imho, this is a nebulous term at best. Unless one had a NOS tube and used it for just a few hours, how does one know that it is ANOS. It might test as new or close and still have many, many hours on it. I use the term UOS...used old stock unless I know the tube is NOS. How about a new designation...at least I have never seen it.
    TANUOS....test as new used old stock??????
     
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  6. Wally

    Wally Telefied Ad Free Member

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    re: that phase inverter in the SCXD..or anywhere else. When one changes to a different tube there...even a different 12AX7...that tube in effect can rebias that operation due to different operational specs. Just as we look for ‘matched’ power tubes, there are people such as serious audiophiles who look for matched triodes because they understand that if there are imbalances in certain areas then the stereo sound image suffers.
    The phase inverter or a driver is not a tone processing position but how a certain tube affects the bias numbers there affects the strength of the signal out of that position and that does matter as to what the power tubes and the OT send to the speaker....so the sonics can change. That change could also occur with another new production tube that has different operational specs.
     
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  7. printer2

    printer2 Poster Extraordinaire

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    The inverter tube has two triodes, one for the actual splitter part and one for the gain stage before it. So different tubes may have an effect on the gain stage.

    2000W, who are they trying to kid? Not saying it is a bad little unit but their specs reall do not tell you anything given no SPL numbers.


    Since the amp has a gain and volume control and is a channel switching amp it will make a difference. But the amp in question has no volume controls after the tube. The output tubes are designed to clip before the preamp tube. So in this case there should not be much difference with different tubes.


    I will just comment on a quote I found.

     
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  8. printer2

    printer2 Poster Extraordinaire

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    I do have some 12AT7's that I would consider ANOS but I would find it hard to prove. They were in a piece of old test gear, actually a filter, that was used as a teaching tool in the college I worked at. I never saw it used and it might have been the same as other pieces, one instructor gets a bright idea for his course and then it just sits on a shelf. I disposed of a lot of equipment (and probably a couple thousand tubes) when we lost space in a reorganization. I grabbed the filter rather than seeing it go to a recycler.
     
  9. tubelectron

    tubelectron Tele-Afflicted

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    I remember reading an Aspen Pittman article on how the vacuum within the output tube = degree of distortion. And thus the myth began...

    Who wrote this ? o_O

    -tbln.
     
  10. teleman1

    teleman1 Friend of Leo's

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    I meant to say, I tried ANOS for all tubes in the amp. I wouldn't know if one tube individually did or didn't make a significance, but I bet it was the 6v6's, wouldn't you say, Wally?
     
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  11. Wally

    Wally Telefied Ad Free Member

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    I believe that’s first mention of ‘hard’ versus ‘soft’ in this thread was in reference to the use of these terms to indicate the
    difference in performance of various tubes of the same make and model. The New Sensor mentions the use of these terms in their grading.
    I also believe that I do not have the training that would allow me personally to expound upon the influence of the amount of vacuum that is created in the tube, but I did find tubelectron’s statement regarding the hardness of the vacuum interesting. I have spent a while today reading through some vacuum tube history, theory, explanation, etc. I have found one mention of the level of vacuum and it’s effect....not much explanation of the fine points of it, though. Second paragraph under ‘Inside A Tube’.
    https://vacuumtubes.net/How_Vacuum_Tubes_Work.htm

    I am left wondering whether it is a variance in the vacuum, the variance in the metals and construction of the elements of the tube, or a combination of all of those variables that create the differences in operational specs. All I can do is try to get them to work in the circuit and find tubes that please my ears.
     
  12. Wally

    Wally Telefied Ad Free Member

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    Maybe....but then I would have to know the Biasing of the tubes being compared to make a valid comparison. A warmly biased new production 6V6 might please me more than a cold biased NOS.
     
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  13. Chiogtr4x

    Chiogtr4x Doctor of Teleocity

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    So the adage we hear or read ( with respect to preamp tubes) about:

    " it doesn't matter about what tube (ex. 12AX7) is in position #V___ , it just has to function..." is not accurate then?
    ( I'm definitely guilty of repeating this!)
     
  14. Wally

    Wally Telefied Ad Free Member

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    it matters in a tone position. It doesn’t matter as much in a driver position. One example would be a microphonic tube. I tried a UOS long plate Sylvania 12AX7 in V1 of a Fender reverb amp last week....ringing like a big bell! Unusable. I put it in in the tremolo spot, and all was fine...no microphony to be heard. As for tone positions...like V2 and the one triode of V4 in a two channel Fender reverb amp based on the AB763 design....a great tube will have more effect on the sounds in the Vib channel in V2 than it will in V4 because everything that goes on in V2 is amplified through the rest of the circuit.
    Sometimes there are concerns other than sound. The cathode follower circuit demands a stout tube that can handle the voltage difference between the cathode and the heater.
    ‘Tube rolling’ can be a time consuming activity, ime. Sometimes the Sonic differences between two tubes are very subtle, but to a discriminating ear that small difference could be the difference between what the player likes and what the player could accept but not like as much as the other. Sometimes the differences are so great that I will mark a certain tube ‘not for tone positions’. It is interesting to witness other people’s reaction to differences. You can learn who has ears and who doesn’t...who is challenged to hear certain frequencies...and sometimes one of these people will instruct me on what they are hearing that perhaps I missed. Sometimes a few minutes and one different tube can turn what could have been a great sounding amp into that great sounding amp. I have heard $4500 boutique Marshall clones become worth that much sonically with the change of a $20 tube.
     
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  15. Chiogtr4x

    Chiogtr4x Doctor of Teleocity

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    Thanks for letting me, bug you ( I do this with 11 Gauge too), just like hearing stuff explained to me! ( even if I don't remember, I can bookmark)

    Edit: I like your explanation after
    " sometimes there are concerns ( with tube type/variant) other than sound..."
    Thanks
     
    Last edited: Jan 29, 2021
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  16. printer2

    printer2 Poster Extraordinaire

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  17. tubelectron

    tubelectron Tele-Afflicted

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    Too bad if most of them don't understand what they do... It is often the problem with Audiophiles, as stated by Bob Crites / Crites Audio - Klipsch parts, service and restoration station :

    [​IMG]

    Conversely, this reply below on your audioasylum link is what I consider a consistent statement on which I plentifully agree. This Guy has probably the same kind of old books as me that deals with tube technology :

    "The 1962 RCA manual states that the final vacuum can vary as much as 100 times."

    1. The quality of the vacuum that can be obtained does vary - just like every other part of a tube's construction. But it is NOT BY DESIGN.

    2. To achieve the vacuum in a tube the bottles are mechanically pumped down, and remaining gas molecules are reduced even further by the getter action.

    3. To preserve the vacuum the internal parts are processed a number of different ways to reduce their emission of any contaminants. BTW, often it is the mica that outgasses most.

    ************************************************************************

    "I am of the belief that this purging of tube parts before assembly is what distinguishes the best of the Western manufactured tubes from those produced in the former communist countries."

    Can I ask for the source of that information? Are you saying that the Russian/Eastern Bloc tubes do not get processed to remove impurities and reduce outgassing? If so you are 100% wrong I'm afraid. It is a required process in tube making. Quoting from a JJ note:

    "Before they are assembled, all parts are thoroughly cleaned using such methods as an ultrasonic bath, chemical cleaning or annealing in an inert gas atmosphere of hydrogen or nitrogen."

    ************************************************************************

    "another myth here, saying that the blue glow is normal"

    Sorry, again I have to differ. Here is a quote from the Sylvania Engineering Data Service, vol. 1, pg 23 (1960?):

    "BLUE GLOWS

    Blue Glows are not tube detriments per se. They are, however, suspects in the eyes of many receiving tube users for lack of a full understanding of their origins. There are several types of Blue Glow which can be described as follows:

    FLUORESCENCE-this type of glow is usually violet in color and most noticeable around the inside surface of the glass bulb. It is most pronounced on power tubes and is the product of electron bombardment of the glass taking place within the tube. It generally has no adverse affect upon receiver performance, and in fact, tubes displaying this phenomenon are particularily good with respect to gas content".

    The article continues, but regarding gas filled tubes like mercury vapor rectifiers, etc.

    One final hint from a 1943 Sylvania "Radio Tube Hints" publication:

    "When in doubt as to the blue content of other types of tubes a sure test can be made by using a strong magnet next to the blub. A gaasy (sic) tube will not be affect in any way by the presence of the magnet, while the fluorescent glow, which has no affect on the performance of the tube, will shift about as the magnetic field is shifted."

    ************************************************************************

    "the older Soviet and Chinese tubes were simply horrible."

    While I agree regarding Chinese tubes, I do NOT regarding Russian tubes. SOME were not very good, but many were terrific - let me list just a few highly desirable early Russian/Eastern bloc tubes:

    1. Saratov 6H30Pi-DR
    2. Saratov 6P3S-E
    3. Saratov 6P14P-EB
    4. 1578 (6SN7) Russian tubes
    5. 1990s vintage Svetlana EL34 & 6L6GC
    6. Pre-Nato war Ei KT-90 & 6CA7
    7. Red base JJ 6L6GC
    8. Almost any Tesla tube

    Shall I continue??

    **************************************************************************

    "In comparison to NOS American and Western European tubes, baking has a smaller impact unless the tube has had significant hours upon it."

    Check the link below for Morgan Jones explanation of much of what we've been discussing. In the .pdf he says a couple things of note:

    "NOS valves are likely to have been sitting in a cold warehouse for at least twenty, and possibly fifty years, so it should come as no surprise that the vacuum deteriorates. In theory, the getter should consume the molecules to maintain the vacuum, but the most common cause of failure in NOS valves is deterioration of the vacuum - this is often referred to as the valve having gone 'soft'."

    Please note he refers to NOS valves (tubes)!

    He continues:

    "Valves that have no manufacturing defects but have been in storage for many years may accumulate a little gas. If there is any suspicion that this may have occurred to any significant degree, it is better to bake the valves before testing rather than risk damaging fragile oxide-coated cathodes."

    He is referring to NOS, not used tubes! If you read the entire .pdf you can get more background, but the statements just above have the definitive reason for baking - to heat the getter to remove any residual gas.

    Stu, I'm not trying to pick a fight, nor do I have all the answers. But what you posted just doesn't align with what many widely acknowledged experts say is the case. That's why I provided attribution/sourcing for the statements I made.

    -tbln.
     
    Last edited: Jan 30, 2021
  18. printer2

    printer2 Poster Extraordinaire

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    Thanks. I am going to stash this nugget for later.

    "When in doubt as to the blue content of other types of tubes a sure test can be made by using a strong magnet next to the blub. A gaasy (sic) tube will not be affect in any way by the presence of the magnet, while the fluorescent glow, which has no affect on the performance of the tube, will shift about as the magnetic field is shifted."

    But I am unsure what you are saying in relation to your previous post. I am not one to pick a fight either, I just want people to know what is factual. I questioned your previous post and the above information does not address it.

    I asked the question in the Tubes / Valves forum at diyAudio and they are at a loss in relating tube vacuum to clipping. They said that you would have more grid leakage current with a gassy valve, which makes sense. I am no expert in tubes but I was in charge of testing and troubleshooting vacuum furnaces at an aerospace manufacturing plant so I know a thing about the technology. I get why they introduced a getter to capture the remaining gas. I get tube life being reduced by remaining gasses in the tube.

    But with the Sweetwater example of 6L6 compared to EL34's saying the EL34's are a more gassy tube and sound more distorted, well I find it hard to believe. Especially when Mullard and Siemems made EL34's also. I would attribute the difference in sound to the geometry of the parts inside the tube and what it does to the lines on the plate curve graph.

    EL34

    [​IMG]
    6L6

    [​IMG]

    So just to make sure there is no confusion. I have posted was I do not believe the level of vacuum has the effect you attributed to it. That is all. I looked for technical information to clarify your statements and could not find any. I also asked the good people on diyAudio (quite a knowledgeable bunch) what they thought of your post. They could not confirm what you posted. I make no claims, other than question what you posted.
     
    Last edited: Jan 30, 2021
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  19. Dan_Pomykalski

    Dan_Pomykalski Tele-Meister

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    What risk is involved? Also, I , and many others, would definitely go for a 12AY7 before a 12AU7.
     
  20. tubelectron

    tubelectron Tele-Afflicted

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    Too bad for them : they probably never checked this point. o_O

    Any old ham radio from the 20-30 era who worked on Armstrong, Schnell or Reinartz regenerative receivers, or Konteschweller / Flewelling super-regeneration receivers knew that vacuum question well. Unfortunately, they are all passed away now... :(

    [​IMG]

    I have this subject discussed in several of my old books from that era (OK, they are well stored now in my attic, and bring them out would be a hassle :rolleyes:).

    That said, I noticed many times and studied the influence of vacuum degree variations on the tone of guitar amps, and confirmed it by oscilloscope output power monitoring and tube tester checking. That's why I speak about it. Sorry, I do not have pics of all that... :oops:

    [​IMG]

    [​IMG]

    [​IMG]

    I am one of those who thinks (and have noticed) that the influence of vacuum on the performance of a tube - both in lifespan and about clipping tone - is very important, just like the Guy you and I quoted, by the way. :)

    But it's me, OK ? :D

    -tbln.
     
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