1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  

kt77s in an SVT classic?

Discussion in 'Amps and Cabs [BG]' started by subbasshz, Jul 5, 2014.


  1. subbasshz

    subbasshz

    Aug 11, 2012
    phoenix az
    Im addicted to punishing volume.
    searched, didn't find a thread on it. but im sorry if this has been discussed / beat to death.

    I just picked up an svt classic today and im wondering if kt77s are a possibility in these amps, and how it would sound. I love them in my 2203 marshall so im curious about running them in my svt.
     
  2. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Amp is entirely unlike a 2203 so won't be an in any way comparable sound. Don't think too compatible either, might sort of work, then break.
     
  3. subbasshz

    subbasshz

    Aug 11, 2012
    phoenix az
    Im addicted to punishing volume.
    hah, yeah. 2203s aint bass amps, I noted that to say I have enjoyed swapping an amp to them. also I like the idea of all my amps have the same powertubes. Im more or less curious about how much more yummy mid content ill get vs how much lowend Ill loose.
     
  4. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I've heard of folks using KT88's in them but not KT77's. Personally, I think it's all a big waste of time. I figure the amp was designed correctly the second time (first time was with 6146b transmitter tubes that arced really bad when Keith Richards laid into them), and if it worked better to use KT88's, they'd have switched to them. Having said that, I've never done it. I just don't see a need to switch. Some people love buying tubes but I'm not one of them.
     
    hover likes this.
  5. I'm no tube expert but I'd think the kt77's would likely light up like fireworks if you put em IN A SVT.
    I'd imagine it'd be a fast waste of some decent KT77 tubes.
     
  6. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    The KT77 is a lower wattage tube than the 6550. A pair of KT77's in class AB1 is rated for around 70W out, the 6550 is 100W. Headroom will be less with a KT77. I'm not sure that the SVT output transformer is best suited for the KT-77, the plate-to-plate load resistances are different for the two types of tubes.
     
  7. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    EQ on an SVT should sort you for mids compared to the the 2203. Can actually boost mids on the SVT, unlike the 2203.
     
  8. subbasshz

    subbasshz

    Aug 11, 2012
    phoenix az
    Im addicted to punishing volume.
    all good stuff. ill keep the 6550s in there.

    I know a local hifi shop that has a LOT of nos GE 6550s. . .
     
  9. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    That's what I use in mine. Those NOS GE6550A's are worth their weight in gold. Almost that expensive. :laugh:
     
  10. subbasshz

    subbasshz

    Aug 11, 2012
    phoenix az
    Im addicted to punishing volume.
    :lol:

    the tubes in my 2203 are worth more then what I paid for the amp. . . im sure it will be the same with this svt.

    :( lololol
     
  11. paulbystereo

    paulbystereo

    Dec 25, 2008
    Orange, CA
    If you dig the Marshall growl, why not try putting your 2203 in to a proper bass cabinet? It works for Lemmy.. (although his are non master super bass amps, but still). I've personally run a Plexi reissue in to an Eden 410xlt and it sounded awesome. I'd let the SVT do what it does best and leave the 6550s in there.
     
  12. subbasshz

    subbasshz

    Aug 11, 2012
    phoenix az
    Im addicted to punishing volume.
    done it with a superbass, and the 2203. :lol:
     
  13. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    That's where I draw the line, bro. I've got to say that I've yet to have a major life altering moment with power tubes where the expensive ones outweighed the cheap ones. I've swapped many 6L6's out over the years, from tight old NOS tubes to brand new ones, and I just don't hear a difference. I'm new to 6550's as an owner but I've played a lot of rental SVT's with a lot of different tubes in them, and they all sound pretty much the same to me, and if there are differences, I find it almost solely related to V1 in the preamp. Now I'm sure some will argue with me, and I won't rule out a major change, especially if you do something like go from 6550 to KT88, but when the JJ's in my Heritage go, I'll be getting more JJ's.
     
  14. You may like how the Marshall sounds using the KT77 but that does not mean that the amp itself likes using them. Why would you want all your amplifiers to use the same output tube?? That's akin to changing out all the engines in your cars to use the same motor. Just 'cos output tubes generally can plug into the same socket doesn't mean that any tube will work at it's best plugged into that socket. They certainly are not "plug and play".
     
    nashvillebill likes this.
  15. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    All your amps having the same output bottles is pretty convenient for keeping spares. Its just having the wrong valves in your amp that doesn't work.
     
  16. FWIW, I have JJ KT-88's in my SVT now and it sounds the best it ever has. Over the years I have had a lot of different 6550's in it: Sovtek, Winged C and Tung-sol that I can remember. I will be putting NOS GE's next time.
     
  17. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Turning things around, the Marshall 2203 came with EL34 tubes in Europe and 6550's in North America. When they mod the 2203 for 6550's, power tube bias circuit is modified so that the 6550's can be biased properly, and the feedback circuit from the output transformer is modified. Both simple changes. So they do use either tube with the same output transformer in the 2203. Many folks who want distortion, very much prefer the sound of the EL34 tube in that amp.

    I don't know why Marshall feels the need to muck with the output tubes. My Marshall 1962 (Bluesbreaker) / JTM-45 originally came with KT-66 tubes, the reissue uses 5881's. Very different amps in terms of sound. Sigh!
     
    Last edited: Jul 7, 2014
  18. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Costs, availability and reliability are the main drivers for power valve choice. The Vintage Modern series used KT66 but had reliability issues with those valves. Better ones might be available now.
     
  19. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    I know but to change things so dramatically. Having a British version and a North American version of the same amp seems odd, the two versions of the JCM800 and other amps with different components sound different. Install tubes or speakers in North America and claim that the amp was shipped incomplete. I've wondered if in some cases there was some sort of tax advantage. These days, the tubes are all manufactured somewhere else so things are different. I would have made sense when tubes were made in the US and would have been shipped to England to be installed and then shipped back in the amps. Same would be true for speakers if a US made speaker was used.
     
  20. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    There was a lot of political-economic stuff going on with valves, its why 12AX7 and ECC83 are the same valves with different designations either side of the water, to stop cheap imports competing with domestics.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.