Results 1 to 8 of 8

Thread: What's going on here?

  1. #1
    Member
    Join Date
    Sep 2006
    Posts
    135
    Thumbs Up/Down
    Received: 2/0
    Given: 0/0
    Rep Power
    13

    What's going on here?

    I have a Vox Straight Six tube overdrive pedal. It sounds really good. When I first got it I thought that it would have some clipping diodes producing the bulk of the distortion. But I can't hear any evidence that there are any. It sounds like the real deal! I do know that it's a true high voltage pedal (200 volts), but every single-tube preamp I've made (high or low voltage) produces very little distortion. This thing has gobs! And it sounds great! How are they doing this with only one tube?

    https://www.gear4music.com/us/en/Gui...itar-Pedal/UET

    0 Not allowed! Not allowed!

  2. #2
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    10,695
    Thumbs Up/Down
    Received: 872/15
    Given: 643/22
    Rep Power
    25
    I am quite certain they have a high gain stage *before* the tube and drive it balls to the wall.

    As in 100X or more before even reaching the first tube grid.

    Of course, since the clipping/distortion comes from the tube itself, thatīs the flavour it acquires.

    1 Not allowed! Not allowed!
    Juan Manuel Fahey

  3. #3
    Don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    10,715
    Thumbs Up/Down
    Received: 815/21
    Given: 1,952/8
    Rep Power
    20
    This doesn't show anything about how the circuits work, but does show some waveforms on a scope. Sounds pretty good too.


    1 Not allowed! Not allowed!
    Quote Originally Posted by The Dude View Post
    But, I did learn something. There are protons, neutrons, electrons, ............ and morons.

  4. #4
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    10,695
    Thumbs Up/Down
    Received: 872/15
    Given: 643/22
    Rep Power
    25
    Thanks.
    Thatīs a typical overdriven triode waveform: flat clipped on top, because it smashes against +V rail; rounded on bottom because tube saturation caused by poor emission with very low plate voltage is not such a sharply defined event.
    Of course top peak can reach +V but bottom will never reach ground.

    Of course, completey different to hand drawn waveforms shown on most (98%) pages explaining "tube sound"

    1 Not allowed! Not allowed!
    Juan Manuel Fahey

  5. #5
    Member
    Join Date
    Sep 2006
    Posts
    135
    Thumbs Up/Down
    Received: 2/0
    Given: 0/0
    Rep Power
    13
    Yeah, I'm actually thinking about doing my own video for the pedal. Every single one I've seen has been terrible. The pedal sounds much better than any of the videos for it would lead you to believe. I don't think there's a single video that uses a Strat. Maybe that's the difference. It sounds great with a Strat.

    I wondered about whether there is a solid state booster stage before the tube. But in my experiments building my own preamps, that approach didn't get it at all. A booster before the tube yielded a pretty crappy sounding distortion.

    Gar Gillies did some strange things with his various Stinger circuits in his Garnet amps. I don't have a clue about how all of that worked. I wondered if maybe Vox had incorporated some of those strange tricks.

    It'd be nice to see a schem of course. Good luck with that, I can't even figure out how to get into the pedal!

    Edit: I just re-watched G1's video. I had forgotten (...blocked out?) that there is a transistor stage before the tube.

    0 Not allowed! Not allowed!
    Last edited by Boy Howdy; 01-09-2019 at 05:15 PM.

  6. #6
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    14,177
    Thumbs Up/Down
    Received: 1,163/5
    Given: 1,229/0
    Rep Power
    28
    Thanks for locating that video g1 Definitely confirms Juan's prediction.

    Very good sounding pedal I think.

    Quote Originally Posted by Boy Howdy View Post
    I wondered about whether there is a solid state booster stage before the tube. But in my experiments building my own preamps, that approach didn't get it at all. A booster before the tube yielded a pretty crappy sounding distortion.

    Gar Gillies did some strange things with his various Stinger circuits in his Garnet amps. I don't have a clue about how all of that worked. I wondered if maybe Vox had incorporated some of those strange tricks.
    There are no "strange things" or special tricks really. Some of it has to do with limiting LF going in as the gain is increased and then filtering some of the hash. That, along with setting up the OD stage to respond the way you want it to. Bias, possibly some voltage sag with a resistor in the HV supply, etc. will change things like symmetry in a dynamic way. Finding the recipe (or knowing how to get there) that sounds good is the only trick.

    0 Not allowed! Not allowed!
    "...less ear-friendly but handy for jazz." Leo_Gnardo

    "A pedal, any kind, will not make a Guitar player more dangerous than he already is." J M Fahey

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  7. #7
    Member
    Join Date
    Sep 2006
    Posts
    135
    Thumbs Up/Down
    Received: 2/0
    Given: 0/0
    Rep Power
    13
    https://gjikaamplification.com/gjika-gainmaster

    Check this out. Tune in at 3:10 to hear the pedal into an absolutely clean amp. That pedal has only one tube. How you reckon he's doing that? I've only been able to get that with two tubes.

    0 Not allowed! Not allowed!

  8. #8
    Member
    Join Date
    Sep 2006
    Posts
    135
    Thumbs Up/Down
    Received: 2/0
    Given: 0/0
    Rep Power
    13

    0 Not allowed! Not allowed!

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •