Is there a fix for tighter bass in a Twin Reverb?

Discussion in 'Amp Central Station' started by randysmojo, May 19, 2009.

  1. randysmojo

    randysmojo Tele-Afflicted

    Age:
    46
    Posts:
    1,214
    Joined:
    Jul 19, 2005
    Location:
    Austin, TX
    I have a 1971 Twin Reverb, and it sounds pretty with the Eminence Tonkers I put in it. The only thing is the bass could be a little tighter. Can adjusting the bias either a little hotter or a little colder tighten up the bass any? I'm also thinking about yanking the two outside power tubes to knock the power down some. I know that would make a mis-match in impedence with both speakers hooked up, but is it safe to run it like that for a while?
     
  2. Wally

    Wally Telefied Ad Free Member

    Posts:
    40,151
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Randy, has that amp been recapped? IF not, then the lows are apt to be a bit flabby form that problem, ime.
    ASide from that, what settings on the amp do you use? IF you are running your bass control above 5 with appreciable volume, you might want to roll the bass down a bit.
    Waiting for that answer.....yes there are things to do to tighten up the low end or to change the nature of the beast in order to get rid of flabbiness. Up the capacity in the first stage of fiiltering, change the tone stacks in the channel preamp, as well as cool the bias down a bit.
     
  3. Tim Swartz

    Tim Swartz Friend of Leo's

    Posts:
    2,009
    Joined:
    Mar 18, 2003
    Location:
    Michigan - Tweenst the Great Lakes
    For tight bass you do not want to pull power tubes. Tight bass requires power. As Wally mentions, filter caps are essential as are strong power tubes and speakers capable of delivering the goods (400w EVs would get my recommendation, but the weight might be a factor).
     
  4. randysmojo

    randysmojo Tele-Afflicted

    Age:
    46
    Posts:
    1,214
    Joined:
    Jul 19, 2005
    Location:
    Austin, TX
    It has all new Sprague Filter caps and new Sovtek 6L6WXT's. The speakers are 150Watt Eminence. If I run it a hair colder, will that help?
     
  5. randysmojo

    randysmojo Tele-Afflicted

    Age:
    46
    Posts:
    1,214
    Joined:
    Jul 19, 2005
    Location:
    Austin, TX
    I forgot to add. I'm running the Treble at 4.5 to 5.5, mids around 6-7, and bass around 3.5 to 4.5 all depending on the room, etc.
     
  6. Wally

    Wally Telefied Ad Free Member

    Posts:
    40,151
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Randy, if the new caps in that first stage of filtering are stock values...2 X 70mfd in serires, then imho there is the first place to start. Even though they are new, that 35mfd of capacitance in that stage is not going to yield what you are looking for. 2 X 220 mfds in series will firm that low end up. This is one area in which the TR's from the late
    '70's differ from the BF and early SF TR's. First Fender wenet to 2 X 100mfd and then on to the 220's. Ime, if you hear an amp with big, firm low end, you are listening to an amp with large capacitance in this stage.
    Tim is correct about the EV's....they punch out the low end firmly. To my ear, EV's yield the sound of an amp....no coloration by the speaker, just accurate reproduction. I have no experience with those particular Emi's. Your EQ's settings are acceptable unless you are really pushing the volume. The bass setting might need to be lower if you are going up into the upper half of the volume range, ime.
     
  7. eddiewagner

    eddiewagner Poster Extraordinaire

    Age:
    62
    Posts:
    7,738
    Joined:
    Nov 6, 2005
    Location:
    ROCK!linghausen/germany
    you are a real man! i have a sf 2x12" pro reverb with tonkers too. that amp feels like bolted to the floor. but the sound is so classy, i deal with it. good luck with your search for more bass.
    eddie
     
  8. Wally

    Wally Telefied Ad Free Member

    Posts:
    40,151
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Eddie, don't ever put EV's in one if the PRo REverb feels heavy to you now! There is only one equation that puts
     
  9. randysmojo

    randysmojo Tele-Afflicted

    Age:
    46
    Posts:
    1,214
    Joined:
    Jul 19, 2005
    Location:
    Austin, TX
    I have one EV and the Tonker is about 8 pounds lighter if I remember right. That being said, the Tonker still out weighs the original Oxfords by two or three pounds a piece. Besides, I like the tone of the Tonkers better than the EV in this particular amp.

    The volume usually gets set depending on the area between a little over 3 to 4.5. I have never needed to put it higher than that except one gig, where the lead singer is near deaf and has two Yamaha 15" monitors cranked up loud enough to blow heads off.

    Would changing the two caps in the first stage to 100's or 220's even take away from the warmth of the amp, or just tighten up the bass a bit?
     
  10. strat a various

    strat a various Friend of Leo's

    Posts:
    4,116
    Joined:
    May 9, 2008
    Location:
    Texas
    I've got an old SF Twin with gold label Jensens from a Blackface... no flabbiness to the bass, no problems at all, and I play pretty loud several nights a week. I'm thinking you have an out-of-spec internal component OR need new power tubes OR your speakers are on their way out.
    Get hold of a known good 4 ohm speaker cab and play at gig volume through JUST the external cab. Obviously, set the bass tone control where you usually play (I set mine up around "8"). If the amp sounds good through the outboard cab, you know it's your speakers. If that doesn't help, I'd put off buying new speakers until you solve the problem otherwise.
     
  11. Wally

    Wally Telefied Ad Free Member

    Posts:
    40,151
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Imho,the 100's would not be sufficient...but YMMV. Two 100's in series doesn't even double the capacitance in that stage as compared to the 70 mfd's in series. Teh 220's in series triples the capacitance. I suppose you could experiment with the 100's and see if it does it for you.
    WArmth? Solid bottom end doesn't preclude warmth to my ear. The best example of this that I have heard was GErald Weber's Signature amp...big bucks, big sound, lot of warmth with a definitively solid low end. I got to listen to a bit of it at a show when a fellow was considering the amp. Gerald had a special room where he took the amp. The bottom end was so solid that I had to ask him what the capacitance was in the first stage. HE made me ask him twice while looking at me very directly.... and then shared that it was 2 X 200's in series. I have a feeling that you would love to hear that amp. 2X6L6's....and Ihave never heard such a solid bottom end. That didn't prevent the amp from yielding some great overdrive when pushed hard.....which he did. The bottom end hung in there, though...never went flabby. The only bad thing I heard was the price...I just couldn't afford it. lol
     
  12. randysmojo

    randysmojo Tele-Afflicted

    Age:
    46
    Posts:
    1,214
    Joined:
    Jul 19, 2005
    Location:
    Austin, TX
    strat a various, I didn't say it was flubby. The speakers are fine(brand new), the power tubes are fine(again brand new). The bass is just kind of boomy and not completely focused sounding. It's not even real bad, but I am trying to get it a little tighter sounding. I'm going to try a slight adjustment in a little bit. I have a practice tonight, so I will get to turn it up to decent volume and see what it sounds like. Some nights it is pretty close to the perfect tone to me, but others, I guess depending on the room, it could be a little tighter on the lows.
     
  13. strat a various

    strat a various Friend of Leo's

    Posts:
    4,116
    Joined:
    May 9, 2008
    Location:
    Texas
    I dig. Twin Reverbs have all kinds of bass response with those big transformers. I think speaker choice is the thing ... one question- do you play with the amp on the floor, on casters on the floor, on a stand, on a chair?
    Jensens, especially older original ones, tend to be a little thin on the low mids and have a concise bass sound. This fits a big ballsy amp, compensates for all that oomph.
    I'd still try it with some other speakers in other cabs, preferably open back. You may even be able to test it with the speakers in another combo amp if the connectors are spade type and not soldered.
     
  14. randysmojo

    randysmojo Tele-Afflicted

    Age:
    46
    Posts:
    1,214
    Joined:
    Jul 19, 2005
    Location:
    Austin, TX
    I normally play with the amp sitting on top of the road case, or in the bottom of the road case depending on stage setup and monitor situation. If I don't have adequate monitors, I will put it on top of the case so I can hear it better unless the stage isn't stable. If the stage is flimsy for whatever reason, I will leave it in the bottom of the road case and run more in the monitors.
     
  15. strat a various

    strat a various Friend of Leo's

    Posts:
    4,116
    Joined:
    May 9, 2008
    Location:
    Texas
    I'd still try that amp through a known good speaker(s) to rule out the speakers as the problem. If it's boomy through a "tight low end" sounding cab, maybe Wally can help you solder your way into a solution. Good luck, man.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.