SVP-CL tube replacement question

Discussion in 'Amps and Cabs [BG]' started by codegear, Nov 1, 2008.

  1. codegear


    Dec 26, 2005
    Hello Dears.

    I got SVP-CL and tubes (2x12ax7 and 2x12au7) seperately.
    But I don't know what tubes have to go to what socket.(v1, v2, v3, v4)
    Give me helps SVP-CL users.

  2. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    There isn't a tube chart under the lid? There should be something inside it indicating it. If not, and if nobody can help you here, write or call Ampeg CS and they should be able to help.
  3. codegear


    Dec 26, 2005

    There isn't no tube name at all on the circuit.
    I send to Ampeg CS, but it's weekend i have to use tommorro.
    So if somebody know let me know.

  4. rbonner


    Sep 25, 2008
    OK look, The 12AU7 and the 12AX7 are both from the same familys of tube. The pin outs are the same between the two tubes. The gain of the 12AX7 is much higher than the 12AU7 plus the plate voltage ability of the 12AU7 is higher by 100V.

    So what does this mean? You aren't going to blow up the tubes by switching them.

    My guesstimation is the early signal path tubes are going to be the 12AX7. So tracking from the input to the preamp, that first tube is a gimmy its a 12AX7. I'm going to figure the BUFFER and Preamp output is going to be a 12AU7...

    I would think the compressor would be a 12AX7 and quite possibly the equalizer is the other side of the 12AX7. You should be able to track right through the preamp and "logically" figure out what is where.

    If i had a SVP here, I'd open it up for you. I went through an SVT-CL manual here that doesnt have any tube layout.

    Oh well, She'll either Fly or Fry.... Naw, plug em in and turn it on. BOB
  5. cb56


    Jul 2, 2000
    Probably the best thing to do would be to PM Jerrold Tiers and ask him. He worked for Ampeg when those were being made.
  6. So the confusion and WAGs can be put to rest, here's the OP's answer:

    Lid off; front panel facing you, just as you would operate the unit:

    From left (closest to the input jack) to right, they are arranged as :

    V1 ------ V2 ------- V3 ------- V4
    12AX7 -- 12AU7 -- 12AX7 -- 12AU7

    There is no compressor in these units. Don't know where that idea came from.
    prue likes this.
  7. codegear


    Dec 26, 2005
    Dear Dave M

    Thanks soooo much.

    And Thanks to other guys for the replys.

    Have a good day.

  8. rbonner


    Sep 25, 2008
    The Master of WAG makes a suggestion. Its good that you had the unit in front of you. The poor guy was in need of the device and without the correct data my point was he wasn't going to blow it up by being wrong. My preamps have compressors. Excuse the error.
  9. codegear


    Dec 26, 2005
    I got reply from AMPEG CS as following.
    Which is different to Dave's suggestion.
    What is correct?


    Hi Joshua,

    As you're looking at the front of the amp. The order from left to right is AU in V1, AX V2, AU V3, AX V4
  10. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    The order of tubes is, starting from the input jack and going towards the other end..... with knobs towards you.......

    Premium 12AX7, 12AU7, 12AX7, 12AU7.

    Premium tube means low noise, etc, since it is the first stage....
    prue likes this.
  11. Steve


    Aug 10, 2001
    That's the way mine is and always has been. If it's wrong, it works and sounds pretty darn good that way.
  12. DJJazzV

    DJJazzV "There's nuthin wrong with this brain!" Supporting Member

    May 17, 2007
    New Jersey

    Your reply was perfect for me. As soon as I saw the word "Premium" for the first position, my tube selection was answered! Your post, plus my recent experience with tube swapping in a Markbass TA503 led me to my favorite combination yet!

    JJ ECC803s (Hi Gain 12ax7), Jan/Phillips (5814a 12au7), JJ ECC83s (12ax7), Jan/Phillips (5814a 12au7).

    I used to have Tung-Sol 12ax7 tubes in it, but the Markbass made me try the JJ tubes, and I like them even more!
    Thank you!!!

    GAIN/Pad Question, since you would be an Ampeg SVP-CL expert:

    I have an 18v Fender Am Deluxe V active bass. Do I have to use the PAD (meant for active basses)? When I don't use it, the gain clips on the low B around 2 o'clock. When I do use it, I can turn the gain almost all the way up without clipping. Is the Pad limiting some of the tube gain in any way? I don't boost or cut anything on the bass's active preamp at all.

    Thanks again!

  13. Funnily enought, the SVP-CL isnt the preamp from the SVT-CL. The SVP-CL is the same (or more or less the same) as the SVT-VR preamp. The signal path uses half of the 12AX7 with half of the 12AU7 to act as a whole 12DW7.
  14. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    The pad is simply an attenuator on the input. it does therefore limit overall gain, which in some situations with the SVP-CL is not good..........

    The SVP-CL is indeed NOTHING to do with the SVT-CL....... It's a stupid name..... I admit it, which is cheap for me to say since I didn't name it.

    yes, it is pretty much the SVT classic pre, with the 12AU7s subbing for the low-gain half of the 12DW7, as well as the 6C4. That accounts for the low output, which is also like the SVT.
  15. NashKat


    Mar 11, 2011
    SE Tennessee
    Many Thanks! A previous owner rearranged the tubes in my SVPCL. This old thread helped me! 05/23/2021.
    Jim C likes this.