Preamp Tubes? - Who, What, When, Where, Why, and How?

Discussion in 'The Workbench' started by joshuaaewallen, Jan 29, 2009.

  1. joshuaaewallen

    joshuaaewallen Active Member

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    Hey All! I'm still a bit new to the Marshall Forum, but already I have seen quite a bit of discussion regarding the selection and operation of power amp tubes. But... I would really like to get some feed back regarding the selection of preamp tubes.

    I rarely play out, and quite frankly seldom have opportunity to turn my TSL122 up past 1 or 2. I am aware of the fact that because of this, I will be getting most of my tone from my preamp section, and not from the power amp. That being the case I would like to know more about how preamp tubes effect my sound.

    I play mainly classic rock ranging from AC/DC to Def Leppard. Clearly I love distorted guitar tone, but I also love the way my TSL122 sounds on the clean channel. So...

    What I am hoping for is feedback from you more experienced members of the forum regarding such topics as: How will different tubes change my sound to better suit my style of playing? What tonal qualities do different preamp tubes have? What is a good starting point for finding the right tubes for me? Can I "mix-and-match" preamp tubes? How long do preamp tubes last? How often should I replace them?

    Please, do share your thoughts on this subject. I am eager to know what your experiences have been. Thanks in advance for your responses!


    [​IMG]
     
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  2. Patill

    Patill New Member

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    preamp tubes last A LOT longer than power amp tubes because they don´t get that hot. A broken Preamp tube is mostly a production mistake.

    Tubes in microphones for example stay there their whole life usually, there is no socket to change them.

    I don´t know how they will affect your sound, but that´s very hard to tell anyway.
     
  3. steelhorse

    steelhorse New Member

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    yep, yep and yep! Have fun with it and explore the different tonal palettes available, you never know what you might stumble across!

    Depending on the manufacturer, the type of tube (standard, high gain, high gain/balanced, gold pin etc.) and the position, pre amp tubes can make a big difference in tone.
     
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  4. joshuaaewallen

    joshuaaewallen Active Member

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    Are there any good resources to help gain some insight into the tone characteristics of different tubes prior to actually buying a bunch of different tubes and juts blindly experimenting?
     
  5. Eag

    Eag New Member

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    Plenty of good sources. One decision you will be making is whether you are going to go with new production, NOS, or both. Next you will want to assess your amp's tone and decide what you want to change. Is the tone too bright? Too dark? Too fizzy? Too much gain? Not enough gain? Too smooth? Too gritty? There are preamp tubes which will address any of these tonal points. For example, in new production tubes, JJ 12ax7s are generally regarded as rather dark in tone which can be nice for taming a bright and brassy plexi....the list goes on and on and on....
     
  6. jcmjmp

    jcmjmp Well-Known Member

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  7. joshuaaewallen

    joshuaaewallen Active Member

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  8. The Mick

    The Mick New Member

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    One of the best things you can do for your amp and yourself is search the thrift stores for old cabinet stereos from the 50's they were very popular. I have found many with the original Telefunken 12ax7's in them. Dealing with the big cabinet is a pain but for the Telefunken's at the price of the stereo it's worth all the hassle.
     
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  9. Eag

    Eag New Member

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    +1

    Someone gave me an old Revere talkie movie projector dated 1954. It had two Black Plate RCA 12ax7 and one Amperex EL84 in it.

    (I also swiped the way-cool bakelite knobs off of it.)
     
  10. joshuaaewallen

    joshuaaewallen Active Member

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    Hello All...

    Can anyone tell me on a TSL122 which preamp tube effects which part of the signal chain in the preamp?
     
  11. joshuaaewallen

    joshuaaewallen Active Member

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  12. spikei

    spikei New Member

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    its quite a complicated one, i can tell you the v4 is phase inverter, i have seen a thread some were. do a search you will find it.
     
  13. big dooley

    big dooley Well-Known Member VIP Member

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    V1 and V2 are the gain stages
    V3 tone stack / cathode follower
    V4 PI
     
  14. joshuaaewallen

    joshuaaewallen Active Member

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    So... Since the four pre-amp tubes "cascade" gain and tone qualities from one tube to the next... Starting with V1 going up to V4... Am I better off going w/ a lower gain more harmonically rich style 12AX7 then increasing the gain in my tube type as I work up to V4 or am I better off to start w/ a high gain 12AX& and move from there into lower gain 12AX7's? The intent being to not lose my overall high gain, but to also create a more harmonically rich tone, not just high gain w/out any soul. Know what ah mean, Vern?
     
    Last edited: Mar 13, 2009
  15. MartyStrat54

    MartyStrat54 Well-Known Member

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    That is correct and this applies only to modern Marshalls using four ECC83/12AX7's in the circuit.

    Please note that the preamp tube is actually two identical circuits inside of one glass envelope. However, in the real world, they might not be that identical. When replacing tubes, it is nice to have a tube tester, because it will tell you how close each half is matched. It is imperative to use a close matched 12AX7 on V4, the phase inverter. On V1 I put a tube that exhibits high gain and V2 gets a similar treatment (You may not want as much gain, so you could use a tube that measures on the low side. I have used 12AX7's that only read 60 per cent in V1 and V2 and the owners are thrilled with the sound they get.) V3 isn't as critical, but I still put a good tube in it anyway.

    I like the sound of almost any NOS tube. It's a joy to be running tubes in your amp with 1955 date codes. Telefunkens, RCA Gray and Black Plates, Sylvania's, GE's and Raytheon's are all good tubes (as long as they test in an acceptable range).

    I have all GE 12Ax7's (1964 date codes) in my DSL401 with Canadian made RCA Black Plate EL84's. What a monster! Total difference in tonal qualities versus the stock OE tubes.

    I wish I could bring some of my tubes and my tester up to where you live and we could have some fun dialing in your TSL122. However, you know if you have a question you can contact me here or by PM.

    Marty
     
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  16. joshuaaewallen

    joshuaaewallen Active Member

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    Thank you! Now that is what I have been looking for. I know that there is going to be a certain amount of experimentation no matter what, but up to this point I really have had no clue where to start. So reading this really rocks!

    What kind of differences in tone qualities between the different tubes you have tried?

    I guess I am hoping someone out there with more experience will just say... "So you're playing this guitar, this amp, and you like this style of music.. Why don't you try this... (such-n-such combination of pre-amp)" Then I have, to my mind, a good starting point for experimentation.
     
    Last edited: Mar 13, 2009
  17. joshuaaewallen

    joshuaaewallen Active Member

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    Thanks! That's uber helpful! You guys rock.
     
  18. MartyStrat54

    MartyStrat54 Well-Known Member

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    I posted the following on a different thread that had expanded into tube usage. I thought I would go ahead and post it here since it contains info on preamp tubes.

    Marty

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

    The gain stages are V1 and V2. One thing a 401 shares with its big brothers are four preamp tubes. What these four tubes do has been posted on other threads, so I won't go into detail about them all. However, keep in mind that an ECC83/12AX7 is a high-mu twin triode. It contains two gain stages per tube and that means your amp has four gain stages and that's a lot. In theory, a 12AX7 has a gain factor of 100, but when it is placed in the amp, it looses some of its gain due to the resistance of the circuit. A tube that will give you more gain is a 12BZ7. It is a direct replacement for a 12AX7 and has a gain of 100 as well. However, it has half the plate resistance so it maintains more gain when placed into a circuit, such as V1. I know several players who did this and they love the way it sounds. Note: I would only use a 12BZ7 in V1. Adding more could make the amp feedback and squeal at moderate volume levels.

    Some people want less gain. This allows the volume controls to be cranked more and therefore you get more power tube distortion (the 12BZ7 will give you more preamp gain and preamp distortion). The tubes of choice are a 12AT7 with a gain factor of 70, a 12AU7 with a gain factor of only 17 and a 5751 (which is a low noise, lower gain 12AX7) with a gain factor of 70. Other 12xx7 tubes with a 9A pin layout are: 12AX7A, 12AD7, 12DF7, 12DT7, 7025 (Ultra quiet, high gain 12AX7), and 12DM7. There are many more and some of these other tubes might work. I'm only listing what are known to be direct replacements for an ECC83/12AX7 tube. Note: If you want a super clean channel, I would recommend a 5751 or a 7025. This is what I use in V1. However the 5751 can be bought for less money than a 7025. The 7025 is very quiet, but has a gain factor of 100 like a 12AX7.

    I you want to try a 12BZ7, the only place you can find them are on Ebay. I haven't seen any tube dealers that sell them (or they were out of stock). These tubes are usually new old stock (NOS) tubes and are in great condition.
     
  19. joshuaaewallen

    joshuaaewallen Active Member

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    V4 is the one in the metal shield / tube, correct?
     
  20. joshuaaewallen

    joshuaaewallen Active Member

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    How much squealing are we talking? Could this possibly be used to create controlled feedback?

    ... Pre-Amp distortion sounds more like my cup of tea. I never have opportunity to crank up enough to actually get power amp distortion. Plus I am theorizing that the split EL84/EL34 power section might help w/ that anyway...

    Ok... We know I like my preamp distortion... How do I balance this rock-n-roll fantasy with my love of a sweet clean channel? Since you prescribe the V1 position be changed for clean and distortion? I can honestly say that as-is, the TSL122 has a pretty amazing clean channel which is very surprising for a multi-channel amp. What do you think?
     

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