Changed tubes in Ampeg SVT-CL

Discussion in 'Amps and Cabs [BG]' started by Slpbass81, Jun 18, 2017.


  1. Slpbass81

    Slpbass81

    Dec 16, 2010
    Orlando, FL
    Endorsing: GHS Strings
    My winged-C's finally died after years and I put some JJ's in. The change in sound was drastic. It seems the JJ's are very clear but the low end that you would feel in your chest is completely gone. The sound guy was asking if there was something wrong because of the lack in low end I usually have and he had to push me up in the mains.

    Anyone else switch from Winged-C 6550 to JJ 6550 and notice a difference?
     
  2. TheSlenderman

    TheSlenderman

    Aug 24, 2012
    DeLand, FL
    I'm not sure how picky the newer Ampegs are, but I've seen many have bad experiences with JJs in their older Ampegs, V4s especially.
     
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  3. ThisBass

    ThisBass

    Aug 29, 2012
    Germany
    The only explanation for some noticeable weakness at low response is an improvement of linearity.
    Tube amplifiers show an distinct sensitivety to impedance maximum of the (ported) cab at the lowish side of the bandwith.
    The more the amplifier acts as current source (highish output impedance) the more the impedance peak of the cab will cause some noticeable hump in response at the low end.
    Wheras the lower the amplifier's output specs is impedance wise then the less the impedance curve will impact the (low end) sound.

    May be the JJ tubes improved your amplifier's technical specs to act closer as like a voltage source versus the winged C tubes.

    GE tubes made in the middle 80's can cause a similar sound effect versus GE and (OEM) Magnavox tubes made in the middle 70's.

    It's probably an technical improvement of JJ's vers winged C rather than a bug.
    JJ tubes are mainly designed with respect to serve the HiFi market
     
    Last edited: Jun 18, 2017
  4. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    The lack of chest pumping low end is not right.

    Did you change the small tubes as well? You could have a weak driver tube. Make sure that the two 12AU7's are in the correct sockets and that they are indeed the correct tubes. The third tube in the lower chassis should be a 12AX7. Make sure that they are properly seated.

    The way that the power tube bias is set can make a big difference. Under bias will sound too sterile and lack low end. There is a range where the green LED will be on.

    The amp needs to reach a temperature steady state before the bias is set. Play through the amp for half an hour to properly warm it up. Set the bias as per the manual.
     
    Last edited: Jun 18, 2017
  5. ThisBass

    ThisBass

    Aug 29, 2012
    Germany
    Right ;)
     
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  6. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    I went from Winged C to JJ in my 74 SVT. Didn't notice a major tonal change, but the JJs didn't last long at operating voltage as JJs tend to do. Went back to the winged Cs.
     
  7. Slpbass81

    Slpbass81

    Dec 16, 2010
    Orlando, FL
    Endorsing: GHS Strings
    I didn't touch the preamp or driver tubes as they were recently replaced. I check the bias every gig and tried running it just before it turned red.

    The amp was loud, but just seriously lacking low end that used to be thunderous with the winged c's.
     
  8. JGbassman

    JGbassman

    May 31, 2011
    Iowa
    Just wondering if you could get the sound back by boosting the bass a bit on the amp.

    I'm not trying to be funny, but I'm at the point I'm needing new tubes as well, and I'm looking around for replacements right now. I don't have the winged c tubes you have, and it's too bad they aren't made any longer. My impression not having much experience in tubes is they can definitely change the sound, good or bad. @beans-on-toast would be a good authority to answer questions regarding this.
     
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  9. 74hc

    74hc

    Nov 19, 2015
    California
    Buy all the Wing C's you can. It's talked about among the tube sellers that the Svetlana factory is no longer operating (the real Svetlana which we know as SED due to a lawsuit by Newsensor).
     
  10. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I have not used the Winged C's before but have heard good things. But I have a 69 SVT with NOS GE 6146b's and two Heritages with JJ's, and channel 1 normal on the 69 sounds identical to the Heritages. No lack of chest thumping, no lack of awesome tone. I think there's something more going on than just the tubes.
     
  11. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    There are differences from one make to another but what you are describing sound pretty dramatic. As was mentioned, you can often compensate by dialing in a different EQ setting. If you can't, something is off. Even though the small tubes in the bottom chassis were recently changed, I would still check that the two 12AU7's and the 12AX7 are in the right sockets. Since there's an issue, you have to sweat the details and cover those basses.

    It is possible that the power tube sextet is not well matched or has an issue and this is affecting the performance of the amp. A tech can take some power supply voltage readings and measure the cathode current of each power tube to determine if the amp is performing within specs.

    There is a reason why people liked the winged C 6550's more than any other tubein these amps. Some resellers still have them but unfortunately, the cost is as high as NOS GE 6550's.
     
    Last edited: Jun 19, 2017
  12. Yep, I agree with Jimmy and Beans: something else is wrong. What was going on that made you decide to change the power tubes?
     
  13. gregmon79

    gregmon79 I did it for the muff... Supporting Member

    Dec 20, 2012
    Chicago IL
    I don't have an Ampeg but I do have an Electric Power Unit powered by KT88's. I tried JJ preamp tubes in there before and it made a HUGE difference in output. Lowered it quite a bit I figured there would be some variation but not THAT much. I also went from the power tubes that were in ,when it was retubed, some Sovteks, to JJs and I could hear a difference in sound there as well. Tubes will change the character you get out of your amp when you swap tube brands out.

    I'm no expert of course. And I'll tell you this much, I will no longer use JJ's after these die out. The first set of 4 I put in there when I replaced the Sovteks, one of them went out on my the first week. I know that's sorta par for the course with tubes sometimes. But after that happened I hopped online and did some research. And there are a lot or folks out there who have had a lot of trouble with JJs and even small hate groups of them. I guess by now, I feel there are better tubes out there and if I'm going to spend my money on that, I want to buy some decent tubes.

    Or it could be what these guys are saying. When was the last time you had it biased and serviced by a good tech? I know I can feel comfy swapping pre amp tubes, but when it comes to the power tubes, I won't touch those. Ever. I know on my amp they aren't something you can just swap out. You need to get it biased and all that good stuff.
     
    Last edited: Jun 19, 2017
  14. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    I'm in that camp. I'll only buy JJ tubes if they're through a rebrander or with extended burn-in/apex matching from AES, and even then only if there aren't other options available. I have a friend who swears by JJ power tubes in his amps bought from a specific vendor that only sells JJ tubes, and is constantly having problems. I've been burned enough by JJ tubes from a number of vendors that I just don't bother with them anymore.
     
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  15. okcrum

    okcrum in your chest Supporting Member

    Oct 5, 2009
    Verde Valley, AZ
    RIP Dark Horse strings
    How far do you have to turn the bass knob to get the low end back? Assuming you didn't change tone settings at the gig, how much did FOH have to boost your low end? Why would your tone to FOH change because of the power tubes if you were running DI?

    Where'd you get the JJs? ;)
     
    Last edited: Jun 19, 2017
  16. gregmon79

    gregmon79 I did it for the muff... Supporting Member

    Dec 20, 2012
    Chicago IL

    Kinda crazy that he consistently has issues with them and STILL continues to get them. To each his own though huh… It’s only taken me one set to realize I won’t be using them again. They are working good now, so I hope I’m not jinxing myself by saying that, but I almost can’t wait till I can get some other power tubes. I will most likely go with a lower shelf Gold Lion or the Sovteks. Sovteks are awesome! I really what they brought out of the Electric.
     
  17. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    What happens if you put your original tubes back in?
     
  18. Mastermold

    Mastermold Supporting Member

    I've never had any problems with the JJs in my HSVT-CL. Bottom for days.
     
  19. ThisBass

    ThisBass

    Aug 29, 2012
    Germany
    If JJ tubes was primarily of sad quality as mentioned they wouldn't sell tubes anymore.
    Not sure ampeg would tolerate serially failure complaints due to tube issues

    It's hard to to get "decent" tubes these days anyway, especially if (any) tubes are meant to be used for MI application.
    Based on common average retail price in the 70's and 80's we had to charge for "decent" 6550 any "decent" 6550 tube these days would sale around 70..80 US dollar a piece.

    Different tubes may cause a slightly different sound. I still have got a nearly brand new set of GE 6550 made in the middle 80's. I have had these GE 6550 tubes in my svt for a couple of hours but was not happy with this sterile and boring sound. And if I remember correctly the retail price in EU for GE 6550 was already something around 25..30 US Dollar a piece in the 80's.

    So if you want buy really decent tubes like made in the good old 70's you may want buy OEM tubes and you'll charge nothing more "comparable" amount of bugs than we had to charge in the 70's
     
    Last edited: Jun 19, 2017
  20. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
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