Another Tube Pulling thread.

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Red Planet, Oct 5, 2005.

  1. Red Planet

    Red Planet Member

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    Many have said here that it dosnt make that big a difference.

    Using a 100 watt Marshall if I did that and wired my cab two run 16 ohms instead of 8 would the two things in cunjunction give me more help to lowering the volume.

    I know the higher the ohms the less the amp puts out.

    My 2x12 cab is 8 ohms and I'd have to change the speakers to raise the ohms but I have plenty of speakers laying around.
     
  2. AL30

    AL30 Member

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    I really don't think it's going to help that much. Pulling two tubes - while giving you 50 watts - doesn't make much of a difference - around 3 dB. Apparently it does affect the tone according to a few seasoned Marshall players I've spoken with.

    I'm not sure how the cab would affect the volume but I used to run a 100W Metaltronix at 8 ohm and it was still brutally loud.

    You've got a loud amp - period !! You may want to try a Hotplate.

    AL

    *** quick edit ***

    I read your post wrong in regards to impedance. Apologies - but I still don't think it will make much of a difference.
     
  3. Red Planet

    Red Planet Member

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    Well what I'm saying is if I can get a little help from each it might be enuff to make up the difference I need.

    I'm actually working on it right now.

    I'm pulling the two G12T-75 16 ohm Speakers and sticking in two G12 Century Vintage 8 ohm speakers.

    By wiring them in series the cab will be 16 ohms then I just pull two tubes, set the ohms switch to 8 on the amp, and let her rip.

    I'll report back and let you guys know what it does. I also have two G12 Century speakers but I thought I'd try the Century Vintage because they are rated 99 db and the regular Centurys are rated at 102 db. So I dont want use the louder speakers if this works. My guess is I'll like the Tonal Response of the regular Centurys better though. They are more like what came out of the cab.

    Nothing wrong with that just tooo freakin loud.

    If it dosent help I can allways just put it back like it was and maybe try a Hotplate next.
     
  4. AL30

    AL30 Member

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    How much volume difference are you looking to get exactly? Just curious. Please keep us posted. I'm interested in your results.

    AL
     
  5. Red Planet

    Red Planet Member

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    The amount of volume difference I want is not something I can measure. I just want it to be not as loud as it was.

    Which I should say with everything I did I'm pleasently suprised. It works real well!

    I changed the speakers out to be able to get the Cab at 16 ohms. I pulled the two inside Power Tubes. Also while I was inside the cab there was a brace that runs from the front of the Cab to the back. I put a screw in that through the back of the cab into it. That seems to have helped the low end boominess it had going. The speakers I put in it were the Celestion G12 Century Vintage speakers.

    With the G12T-75 Speakers in it it was a tad bright and the new speakers smoothed that out just a little.

    Anyway I fired it up and I'm amased at the sound I'm getting. I cant hear any Tonal Problems from pulling the two tubes. There is a small volume difference from the ohm change and the Tubes.

    I can not believe how good this amp sounds. The clean sound just by rolling the volume knob on my guitar back is amasing. The dirty sound is awsome.

    I'm setting the Preamp Gain full up and the Master Volume a little less than half way. This could be the ultimate giging amp with no pedals and just guitar. Then for those out side gigs just pop two more tubes in and set the ohms switch back on 16 and let her rip.

    One dosent need much to play with this amp. Just a guitar and a set of fingers. :dude

    Who needs a freakin amp that cost 4 or 5 grand when you can play one of these. :eek:
     
  6. Red Planet

    Red Planet Member

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    Also with these new Celestion Neo Speakers the Cab weight went from 54 lbs to 46 lbs.

    It allready was a light cab but now it feels like it dosnt have any speakers in it. I can easily pick it up with one hand.

    Very cool. The head ways 45 pounds.
     
  7. KLB

    KLB Member

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    I wouldn't expect much of a difference from pulling tubes, and I've tried this with 100w Marshalls before.

    That 100w Marshall has huge power, output and filter caps. The combination of those elements is more BEEFY than in a 50w or 20w amp.

    The dynamic response from 2 vs. 4 power tubes won't vary much, but you seem to like it, so that's all that matters.

    50w vs. 100w is only 3db less loud.

    As for speakers, using fewer and lower efficiency speakers in a CLOSED back cab will help control volume.

    With four "99db" (your Century Vintage) speakers in a closed cab.

    1 speaker = 99db with 1 watt at 1 meter distance.
    2 speakers = 102db " "
    4 speakers = 105db " "

    Change those to Heritage G12M20 and you will reduce those numbers above by 3db, plus the feel will be LESS stiff. (Neodymium vs. Ceramic magnets.)

    IMO, you'll get more volume control without modding your amp by using an attenuator at -3 or -6.

    Have fun and don't blow out 'yer hearing. :D
     
  8. Red Planet

    Red Planet Member

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    I'm using two Century Vintage speakers in a 2x12 cab not 4.
     
  9. KLB

    KLB Member

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    Yeah, I saw that.

    I was just using 4 to show the volume change as more speakers are added. You would have to add a 2nd 4x12 cab to double the volume by 3db, and so forth.
     
  10. Red Planet

    Red Planet Member

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    OK I thought you thought I had a 4x12.

    I'm happy with the tone right now. It is still pretty freakin loud. I upped the cab impedance to make it less effecient and pulled two tubes.

    I may try to put the two tubes back and see what the difference is. It would be nice if I had a db Meter. :D
     
  11. Killa-B

    Killa-B Member

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    I find pulling 2 tubes mostly moves the breakup zone to a more managable volume. In other words, the amp doen't stay clean as long.

    (as everyone knows Im sure) the decibel system is logarithmic, so 3db is quite appreciable to the ears.

    As others have said, if you like it, that's all that counts.:dude
     
  12. Red Planet

    Red Planet Member

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    I agree Killa.

    Its sounding pretty good right now.
     
  13. KHK

    KHK Silver Supporting Member

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    Interesting thread and really coincidental. I spoke to a guy by the name of Kevin O'Conner a couple of weeks ago about his power scaling circuit. He heads up London Power and he suggested that I try pulling tubes from my amps. I got the impression that he felt that the decrease in output is not linear. I pulled a power tube out of my Deluxe Reverb and it made a huge difference in the perceived loudness of the amp to my ears while still sounding good. I have a 100W Boogie w/4 6L6's and he suggested that I could pull three tubes and be OK and that the output might go down to like 7W or so. This could only be done safely with a fixed bias amplifier.

    I am not technical when it comes to this stuff but he seemed to know what he was talking about. My amp tech says that he has published a number of books on amps etc.. and he is pretty well known in the industry. This is probably old news to alot of you guys but I thought I would pass it on. I'll let you know if anything blows up but for now, everythings working.
     
  14. Red Planet

    Red Planet Member

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    Well I did a little testing today.

    I set a Microphone (Shure Beta 57) in front of one of the speakers in the amp and went into my Recording board.

    I set the Channel it was going into so the Signal was at 0 db. Then I set the Output Level Meters from the Board Mains so it read 0 db at the loudest most Aggressive point of Playing, using some Heavey Power Chords for the Playing.

    This was all done with Two Tubes Pulled (the Center two). Going into a 16 ohm cab with the ohms Selector set on 8 ohms.

    Then I shut the amp off stuck the two missing Tubes back in it reset the ohms Selector to 16 ohms and fired her back up.

    It was easy to see the results. The Level Meters on my Board were going to +4 db and the Level Indicator on the input of the channel was peaking red.

    So I can tell a 4 db difference between the 2 and 4 Power Tubes. Also while doing this I swapped back and forth several times and did notice a Major Difference in the Loudness of the Amp.

    Now you also have to bear in mind that I changed the Speakers in the Cab from 97 db 16 ohm Speakers to 99 db 8 ohm Speakers.


    Its hard for me to say what difference that made because I cant switch that back and forth easy. I was trying to get the Amp to put out less with the Cab running at 16 ohms but realise the 4 db difference in the Speakers may cancel that out. As someone pointed out.

    Tonight I'm gonna swap the Speakers back and see what the difference is with that, having taken a reading of the db Level before I make the swap to see if I get a difference with the ohm change and Speaker db change. I will do it four ways. 50 and 100 watt on both sets of Speakers just to check it all I can. Then I will post back my findings.
     

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