Preamp tubes

Discussion in 'Amps and Cabs [BG]' started by No Treble, Feb 21, 2018.


  1. No Treble

    No Treble

    Oct 26, 2016
    1994
    I have an Ampeg V-4BH. As predicted, I am now going to exercise my right to go and change some perfectly fine, working, good parts, for no real reason.

    I found a red-lettered "CHINA" preamp tube in this amp. Probably offers some great access to breakup, and all, but meh. I wannit out of there. I went to "Amplifiedparts.com" and ordered a full preamp tube set for this thing (which the owners manual incorrectly states BTW, 3x 12AX7's and 1x 12AU7 is correct).

    The inevitable question arises: is there a "preheat" time? Any "break in" period for preamp tubes? I've heard some high-end radio amp guys (using the same 12AX7s) talk about a sudden change in sound, usually for the better, but a change none the less. I know that biasing is for power tubes only, but these have unique needs also, right? After I change these tubes, magic should flow from the bass while it's just hanging there hands free, right? These will be what makes the "extremely average" player into a bass hero, right? Like saving orphan children from a burning hospital with my guitar type of awesome, right? Just wondering.
     
  2. disssa

    disssa

    May 6, 2009
    Germany
    "Made in China" does not necessarily mean "bad quality" or "bad sound". Many tubes are made in China. They are bought in large quantities and given a new name. There is a big hype about the sound of different tubes. Many people do not know that it is one and the same tube, but they can hear differences... ;)
     
  3. No Treble

    No Treble

    Oct 26, 2016
    1994
    I can agree that it doesn't necessarily mean that tubes made in China are of a "lesser quality", I was just using this as an excuse to buy NEW TUBES, because just as Chinese product reputations are inferior (stay with me) NEW IS ALWAYS BETTER. Really, I just like options. I found it in the power amp section, in the V2 position. It's not a critical one, just helps me reinforce the argument with the wife about wanting NEW TUBES. New.
     
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  4. Drgonzonm

    Drgonzonm

    Sep 4, 2017
    American SW
    I see you referenced your manual when looking for tube types. Look on page 6 of the manual, where it explains the use of the stand by switch. I going to give bad information. When you plug in your amp,wait 3 minutes before turning off the the standby switch, you should have lights indicating whether the amp is in standby mode.
    After you read the manual, and find my recommendation is way too long, feel free to post any negative comments.

    Another choice is to look up the tube data sheets, and find out if there is a recommended warm up time. After all some tubes do have a recommended warm up time. I use frankstubes to find tube data. Your manual is a better bet.
    Regarding break in time, about 100 hours many manufacters use to provide this service. If a tube will fail early in life, the first hundred hours are critical, then the tube will last close to the bogey life.
     
    Last edited: Feb 21, 2018
  5. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    Which tube set did you buy? Looking at the site they have JJ or TAD sets. I don’t personally like JJ tubes, too many early failures and poor quality products to continue using them for me. If you got the TAD set then as Dissa said you probably got the same Chinese made tube without the generic labeling.

    If you got the apex matched/burned in power tubes I wouldn’t worry much about break in time for those, if not then I’d say keep an eye on the bias setting for a little while. The preamp tubes are self biasing so as they may drift as they age but it should be gradual. I wouldn’t worry about break in time.
     
    No Treble and beans-on-toast like this.
  6. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Some people like to stock up on tubes so they have them when needed. It’s a good idea.

    It is important when buying spare tubes to put them in your amp and use them while they are still under warranty. If they have any issues, you want to discover that while you can still return them. After a month or so you can remove them and put them in storage for when they are needed.

    The place that you bought your tubes from also offers new old stock ones. These are made in the US. This is a good option if you don’t want relabeled made in China tubes. Unfortunately, they cost more.

    Some tube pins, especially on NOS products, have a black tarnished look. This is oxidization and acts as an insulator, like a resistance, inhibiting signal flow. You can gently scrub this away this with Deoxit D5 and an inter-dental brush. This helps improve performance. If you leave a light coating on after cleaning, it protects the pins and the tube socket terminals. Note that tube pins have a plating on them, you don’t want to remove this by polishing the pins with an abrasive cleaner. That is why deoxit is recommended.
     
  7. No Treble

    No Treble

    Oct 26, 2016
    1994
    I ordered a set of 3 (come as a set) Electro Harmonix 12AX7s and a TAD 12AU7. I can agree that TAD may very well be a relabeled China tube. I wanted that one specifically because it was the affordable option to the Genalex gold lion "balanced" dual triode tube. Somewhere in these forums is an article that pointed out the notable improvement using a balanced 12AU7 with this amp, so I got one.

    I opted out of the power tubes at this time. I know I really didn't need them. I like what someone did with these. They are JJs, and that isn't so nice, but instead of the 6L6GC 30W models called out, someone used a little trick to make this V-4BH yell just a little bit louder by putting 4 6550 35W howlers in it. Now, it is a 140W amp, rather than 100W. I will keep these to failure.
     
  8. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    I've seen people replace Made in China Shuguangs with rebranded Shuguangs pretty often. Better things to spend money on.
     
    saabfender and SirMjac28 like this.
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Beware the (entire) tube reseller market, it's full of snake oil, mythology, fanciful stories and dialog designed specifically designed to separate you from as much money as possible.

    While there are some honest folks in that business, it's very hard to make a living without joining the fray of the above and buyers are easily duped by a good story that they want to believe.
     
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  10. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    Those figures are dissipation wattage, not power output. The V4 won't do higher output with different tubes unless you've modified the power supply and output transformer to match. What will happen is that the higher current draw is going to stress your power transformer. I've had three of the vintage amps, the one that ran 6550s ran significantly hotter than the others due to the higher current draw. Power output wasn't noticeably different IMO. Not sure how the V4BH PT will stand up to the extra current draw.
     
    Passinwind likes this.
  11. No Treble

    No Treble

    Oct 26, 2016
    1994
    It seems to not care all that much. I don't ever really get to max output, because it is plenty loud. I bet the cab starts to distort and kill small furry animals before I ever get to "stressing the power transformer".

    Well, it was only a set of preamp tubes, around $60 including $4 for shipping. I never inhaled! That shouldn't require a second mortgage on the house. Hardly what the IRS wants for their "products and services".

    I'm not sure I've heard the right tone in your message. Actually, I find it presumptuous. Maybe I should lighten up some, but dang, buddy. Next time I want financial advice, I suppose I should ask your opinion first?

    I was simply asking about preamp tubes. The little tubes. Is there a "burn-in" period, or any cautions involving the preamp tubes? Preamp tubes? Remember those pesky preamp tubes?

    cd9906d7a6e12540687506798a85c55d--super-troopers-beautiful-men.jpg
     
  12. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    The little tubes are also called small signal tubes. They amplify low level signals. They aren’t only found in preliminary amplifiers, they are also in power amplifiers.

    A burn-in period is good as it can weed out tubes with issues. Some resellers burn-in tubes, 24 hours for example. There are two types of burn-in that is typically performed. One just energizes the heater, in the other, they apply a bias and high voltage and test the tube under typical operating conditions. After a burn-in, they perform various tests. Some resellers do not perform any burn-in or testing.

    Tubes do not need to be burnt in to sound better as can be the case with speakers.
     
    Last edited: Feb 21, 2018
    No Treble likes this.
  13. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    When you ask a question, you are the one who needs to lighten up if it's not the answer you are looking for.

    If you already know the answer then why ask the question? If you are looking for folks to simply agree with you and give you strokes, this probably isn't the best forum for that kind of thing. YMMV.
     
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  14. No Treble

    No Treble

    Oct 26, 2016
    1994
    Thank you sir. That's the kind of stuff I was looking for, you know, some helpful information, relevant to the question.

    See above reply. Sheesh. So critical, if not also off-topic, but what do I know? I'm the one asking questions here.
     
  15. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    If you don't (or can't) see the relevance and value in what I posted, it's no wonder you express such an attitude.

    How about this... good boy, atta boy, good job, awesome sauce man! Is this more along the lines of what you are looking for?
     
    robd, S-Bigbottom, TinIndian and 5 others like this.
  16. BassmanPaul

    BassmanPaul Inactive

    <sigh> Why do so many threads end up with the OP getting snarky when all folk are doing is trying to help him?

    The biggie for me in changing from 6L6GC output tubes to 6550 is the heater draw. Four 6L6GC draw 3.6A, 0.9A x 4. Four 6550 draw 6A, 1.5A x 4. That’s nearly twice the heater draw for no gain in output power. I can only hope Ampeg kept this in mind when they spec’d the power transformer.
     
    Dominic DeCosa likes this.
  17. Wasnex

    Wasnex

    Dec 25, 2011
    In my experience the EH 12AX7s tend to bright with lean bass. They broke up early in the bass amp I tried them in, and the transition into distortion was sudden and varied with frequency; I.E., low notes required a stronger signal to distort than higher notes.

    I think this tube would be best if you are looking for bright, high-gain distortion and don't mind if the lows wash out. I'll keep rolling them into amps, but I doubt they ever make the cut in a bass amp. Hopefully they will sound better in your V4. Every circuit is different, so it its possible.

    Is there a particular change you are looking for?

    I found the Sino 12AX7B to be even higher gain than the EH 12AX7, but they have a more balanced sound and transition much smoother into OD. I wound up going with the Genalex ECC83/12AX7 (Chinese version). This version of the Genalex was very similar to the Sino 12AX7B, but with slightly lower gain and even better tonal balance and touch sensitivity.

    I have had good luck with TAD tubes. In my experience their selection and matching process is top notch.
     
    No Treble likes this.
  18. 40Hz

    40Hz Supporting Member

    This is where the OP lost me. :laugh:
     
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  19. Drgonzonm

    Drgonzonm

    Sep 4, 2017
    American SW
    If you can believe posters on the net, Ampeg provided kits to upgrade to the 6550's on the v4 amps. While not v4's are upgradeable, enough of them are, so 6550s in a v4 are not a big surprise.
    I wouldn't change to 6l6s without a tech rebiasing the the tubes.
     
    Last edited: Feb 21, 2018
    No Treble likes this.
  20. Wasnex

    Wasnex

    Dec 25, 2011
    IMHO tube rolling can be beneficial and a lot of fun if you have a handful of tubes. More likely to lead to disappointment if you randomly select one tube. I think I have 8-9 varieties of 12AX7s and the EH may be my least favorite. It's actually a good tube that produces relatively consistent results, but it doesn't have the characteristics I like.
     
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  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Jun 12, 2021

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