Tube Store 7025 preferred

Discussion in 'Amps and Cabs' started by digthosetubes, Feb 17, 2012.

  1. digthosetubes

    digthosetubes Senior Member

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    I have these tubes new onhand:

    Tube Store 7025 preferred. (1)
    Sovtek 12AX7LPS (Russia) (2)
    Tung Sol 12AX7 (Russia) (1)
    JJ ECC83S (Slovak Republic) (2)

    Can someone please help me with these tube question:

    1. Where is the Tube Store 7025 made, what tube, if any, is it modeled after, and how does it sound in general.
    2. What is your opinion of these four tubes in terms of tone and reliability.
    3. Please suggest a starting point for retubbing a KOCH Studiotone. There are only three preamp tubes used in this amp. I understand where V1 is and basically what it does. But I don't really know much about the function of the other two preamp tubes. (They are all 12AX7).

    Power Tubes in there now are TAD EL84-STR's with about five hours on them. I'd rather do this one time, as I find it difficult to install these tubes behind the power tubes and its screen (there to prevent breakage and such).

    The preamp tubes in there now are about five or more years old and I am getting some intermittent hum, which was there before I put in the new EL84s. Normally, this amp runs silent.

    Thank you.
     
  2. Zerksies

    Zerksies Member

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    #1 it is probably a NOS no name brand tube. It cold be a hit or a miss
    #2 I have always preferred the Tungsol 12ax7
    #3 I don't know that amp to well. but V1 is a very important tube it's where your tone is and V3 is probably the phase inverter and V2 is probaly another gain stage so you will get the most tonally out of V1 And 2
     
  3. ked

    ked Supporting Member

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    Don't know anything about this amp or what the function of each position is. Try the Tungsol in V1 and see if you like it. If the amp has a cathode follower, make sure you don't use the Tungsol in that position, it won't handle the voltage. Put the Sovtek 12ax7LPS in the phase inverter position. Don't know what the 7025. I don't like JJ preamp tubes but you can try it in any of the positions.

    Ken
     
  4. solitaire

    solitaire Senior Member

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    1) My memory might fail me, but I believe the review for the Prefered Series 7025 once was that of a TAD branded valve. My guess therefore is that the 7025 is a STR of chinese origin. If so it's as good as it gets amongst current prods.

    2) The Sovtek is bright in an American way, possibly good for cleans but not e.g. for British crunch. The JJ is twangy, very durable and is hard to break up. The Tungsol is quite fat sounding but can have a tendency of kicking-the-bucket in cathode-following or driving stages - as I'm sure does the Sovtek.

    3) Zerksies is probably correct in his guess work. If not going with pedals and fairly low output pickups the body is more important than the breakup of V1. Had it been me I would have put the Prefered in V1, the TS in V2 (unless would that be a cathode follower I'd trade pos w. the Prefered) and the JJ as V3/ PI.
     
  5. MT Buckaroo

    MT Buckaroo Silver Supporting Member

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    I'll play. I'd go with the Tung-Sol RI in V1, the 7025 or JJ in V2, and an LPS in the PI slot.
     
  6. digthosetubes

    digthosetubes Senior Member

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    Thank you, fellows. The Studiotone is a PC board amp and has a pretty strong overdrive section (OD1 and OD 1.5).
    That Tube Store 7025 cost about $25 new -- and that is all I know about it.
    The plate structure is 1/2 inch and the only unique thing about the tube's appearance is a single wire that supports a small halo over the top of the tube.
    The amp has a solid state rectifier section and the power tubes, according to Koch, are self biasing. If this helps any of you advise me further, I would appreciate any thought you all have.
    Thank you.
     
  7. big mike

    big mike Moderator - EL34 Emeritas Staff Member

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    Ditto

    Tungsol sounds great
    JJ or Chinese will handle cathode follower better
    And the Lps is a great PI tube
     
  8. Tommy_G

    Tommy_G Member

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    The LPS isn't as great of a PI tube as some would think. 12ax7's are spec at 1.2mA output, and I seem to recall that someone had posted measurements of LPS's as about half of spec.

    Use a 12AY7 in the PI, and you will notice the ability to drive your power amp section hard without hearing ugly buzzy things.

    Don't ever put a Sovtek LPS in a cathode follower position, unless you feel rich. I went through $100 worth of tubes until I decided enough was enough. That's the first thing you need to know about the LPS, other than they are a great sounding tube.
     
  9. Doug's Tubes

    Doug's Tubes Member

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    Made in China by Shuguang....same tube as Ruby 12AX7AC7 HG for a lot less $$.
     
  10. cap47

    cap47 Member

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    Use the 7025 in V1! Great tube for V1!
     
  11. Tommy_G

    Tommy_G Member

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    I'm curious about the tubestore 7025 as well.

    Can anyone explain how it compares tonally to the more common Shuanguang 12ax7a or b (which I buy Groove Tubes gold version of it - the GT12ax7c). That tube needs more mids in my application, but I love its articulation and grit.
     
  12. digthosetubes

    digthosetubes Senior Member

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    [​IMG]
    A little eye candy hopefully to stimulate discussion. The 7025 Preferred is shown on the left, then the Sovtek 12AX7LPS, and the Tung-Sol 12AX7. The posts are appreciated. Thanks.
     
  13. solitaire

    solitaire Senior Member

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    That's a huge simplification, mate. But it does share the same plate structure and spacers. Like I said it has more incommon with TAD pre-amps, which on the outside look indeed a lot like the 12AX7AC7 HG, but are indeed STRs. I suppose you're familiar with that term.
     
  14. solitaire

    solitaire Senior Member

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    Those 12AX7A and 12AX7B are most likely Sinos, not Shuguangs. Sino/ 'China' pre-amps are usually lower quality valves. Shuguangs are sold with an AC suffix followed by a revision number.
     
  15. digthosetubes

    digthosetubes Senior Member

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    I could use a good education about Chinese tubes. Russian ones for that matter.
    I used to Study The Tube Amp Handbook a lot. But it's been some time since I've had my nose pressed in there. I do seem to be able to understand about JJ tubes, the former Tesla company, etc.

    And I guess, without dates, a lot of this tub discussion is clouded.

    I do find all the talk about tubes rather fascinating. They are the heart of an incredible instrument that is the soul of the electric guitar if not the heart.
     
  16. chervokas

    chervokas Member

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    Shuguang describes it's 12ax7 range here http://www.tube.com.cn/en/DIY/xinpintexing.asp:

    "In recent years, the prime amplifier of Shuguang has gotten great achievement. In turn it produces 12AX7, 12AX7A, 12AX7B, 12AX7M, 12AX7-Ⅲ, 12AU7, 12AT7, 6P14P and EL84. 12AX7 is an ordinary kind of product, being generally used where there is no heavy demand of silencing noise and pshaw. 12AX7A is a completely qualified product, which has passed the testing of pshaw, noise and microphone. It is fit for the first tube, satisfying the highest demand of prime signal amplifying. It has high rate of being qualified, far exceeding the Russian products. Its exports occupy 50% of the global outputs. 12AX7B is the improvement of 12AX7A, and it completely obviates the microphone effect of 12AX7A. 12AX7M is the product, which Shuguang specially develops for a foreign company; herein we will not make out a specific introduction. The tube core of 12AX7M is shorter than 12AX7B, thus lowering the possibility of its vibration to the music,and the anti-microphone effect is more sufficient. However, its amplifying performance and gain is relatively inferior. So it is a good choice of the type that has no high demand of amplification performance and sensibility. EL84 is another type of improved product. Comparing with 6P14P, it has greater compressive strength and output power. It is mainly used in bookshelf sounder of low power and the outer sounder of computers. Being considered as the best one in the world, EL84 has broad market outlook.

    7025 is the prime amplifier of highest quality in Shuguang. It can function as 12AX7B. Because of its perfect accomplish in controlling noise and microphone effect, many famous factories in the world stock it. It is the pet work of prime amplifiers in Shuguang."

    How recent the description is, how it related to all the various relabelled or private labelled version for sale in the west I also don't know.
     
  17. thosk

    thosk Silver Supporting Member

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    Many thanks for making clearness of information known.
     
  18. chervokas

    chervokas Member

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    hee hee...well, I didn't translate it!
     
  19. digthosetubes

    digthosetubes Senior Member

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    Nice, indeed. Very.
    You thank me.
     
  20. chervokas

    chervokas Member

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    BTW, just try out the tubes and see what you like. Among new production 12ax7s the only one's I've really liked are the Sovtek LPs but by no means have I made a comprehensive survey and I have heard that in recent years the QC has gotten really dicey on those Sovteks so make sure you buy 'em from some who does good screening (I haven't bought a new production 12ax7 in quite a few years).

    FWIW, because preamp tubes can last a long time in guitar amps, it's often worth it just to spend the bucks on NOS or ANOS preamp tubes.
     

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