1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

Using two Ac15c1’s: One sounds glorious, the other… not so much.

Discussion in 'Glowing Bottle Tube Amp Forum' started by Bearzooka, Mar 3, 2021.

  1. Bearzooka

    Bearzooka TDPRI Member

    Age:
    52
    Posts:
    59
    Joined:
    Aug 5, 2018
    Location:
    none
    I bought a second Ac15c1 and a Radial Engineering Twin City to run both Vox’s together (I have them stacked on top of each other, and only play through the normal channel on each one with the same settings on both amps). The problem is they sound vastly different. The Ac15 on the bottom (original) sounds so full and thick (Lots of low end and clarity, 3-D sounding, lots of presence) as opposed to the one on top (new), which is all mids, and lacks all of that, very thin sounding. I’ve switched the phase on the Twin City, and all it does is thin out the sound of my original Ac15 (making it closer to the new Ac15). I retubed each amp with JJ’s and matched pairs for the power tubes. Pulled both apart to compare the circuit boards, no bright cap mods or other user mods. Both are stock, different chips (I’m assuming for the trem/reverb) and a couple different resistors as far as I can tell. I know components have tolerances, but the sound I’m getting seems too far off to be just that. Anyone out there have a clue?
     
  2. DougM

    DougM Poster Extraordinaire

    Posts:
    6,763
    Joined:
    Jul 5, 2017
    Location:
    Honolulu, HI
    Do they have the same speaker in them?
     
    hotcoffeenochill and Jakedog like this.
  3. MickM

    MickM Poster Extraordinaire Platinum Supporter

    Age:
    63
    Posts:
    5,262
    Joined:
    Oct 13, 2006
    Location:
    A steel guitar engagment.
    Wish I had a clue to help you figure this out. Doug just beat me to the only thing I can think of.
     
  4. Jakedog

    Jakedog Telefied Ad Free Member

    Posts:
    21,175
    Joined:
    Mar 26, 2003
    Location:
    The North Coast
    Are you always playing them in the same positions? I’m sure you thought of it, but just in case- did you switch the top and bottom amps? Does the thick and juicy sound stay with the bottom amp? You could be hearing the bass coupling from one of them sitting on the floor. It’s the reason I won’t use an amp stand or other lifting or angling device. I won’t even leave an amp on casters if I’m done moving it. Any time I take an amp away from sitting flat on the floor it loses all its low end in a very unpleasant way.
     
  5. DougM

    DougM Poster Extraordinaire

    Posts:
    6,763
    Joined:
    Jul 5, 2017
    Location:
    Honolulu, HI
    I was thinking of that too. Great minds think alike, lol. It could also be that the speaker in the new one hasn't broken in and loosened up yet.
     
    RoscoeElegante and Jakedog like this.
  6. 41144

    41144 Tele-Afflicted

    Age:
    68
    Posts:
    1,879
    Joined:
    Sep 5, 2017
    Location:
    Brummagen
    Too obvious I can possibly see but ... for the 2nd one, is it new/how long has it been an issue .... so does the 'new" speaker just need breaking in?
     
  7. Paul G.

    Paul G. Friend of Leo's

    Posts:
    3,568
    Joined:
    Mar 17, 2003
    Location:
    Rhode Island
    I'm thinking the new speaker is tight and needs some time before it'll give up those mids and bass you're lacking. If things don't change, the next thing I'd do is compare the bias between the two amps. Bias can make an amp sound big and full and rich; or weedy and thin.
     
    Jakedog likes this.
  8. Preacher

    Preacher Friend of Leo's

    Posts:
    4,405
    Joined:
    Apr 17, 2007
    Location:
    Big D
    see post above.

    If the new amp is indeed new and competing with an amp that has been around the block and is broken in I am sure it will sound different.

    I also agree with @Jakedog as an amp sitting on the ground seems to have more lower end that one that is suspended.
     
    Jakedog likes this.
  9. David C

    David C Tele-Meister

    Age:
    65
    Posts:
    164
    Joined:
    Mar 28, 2020
    Location:
    Coraopolis, PA
    Just out of curiosity, did you try to compare both amps using just the A/B feature to see if they actually do sound the same? Try putting them both on the floor and using the A/B switch.

    You may not have the room, but I liked spreading the amps apart when I use the splitter for that stereo effect.

    Also, my Radial switch is identical to yours. You should have a Drag adjustment on that pedal. Make sure it is turned to high noon for starters.
     
    Bearzooka and muscmp like this.
  10. RoscoeElegante

    RoscoeElegante Friend of Leo's

    Posts:
    4,371
    Joined:
    Feb 19, 2015
    Location:
    TooFarFromCanada
    +1 what DougM says above.

    I had my AC15C1 for several months and was very frustrated with it. Spiky, harsh, stiff, nasty. Was just about to sell it when I gave it one last big break-in push. I played my Gretsch baritone through it for several hours. The kids weren't home, the neighbors are tolerant, I put on shooters' ear protection and a baseball game and just made a lot of noise. For hours and hours. The next day, I gave it the one last chance at usable volumes and with a variety of guitars, and it was lovely. Just as you describe your older AC15. Lush and expressive and clear and...lovely.

    So my bet is with speaker break-in. Give your newbie more time and more exercise, and see what it's like in a few weeks.

    By the way, I always physically separate amps when I play two (or more) at the same time. That really makes 'em talk with each other.

    Good luck!
     
    muscmp likes this.
  11. muscmp

    muscmp Tele-Afflicted

    Posts:
    1,821
    Joined:
    Jul 1, 2008
    Location:
    california
    yea, what dougm and davidc said above.

    when i bought my ac15, my wife's nephew had owned one for a couple of years and had gigged with it. even tho i thought mine sounded great, when he brought his over, mine was puny and his sounded great. it let me know that it needed to be broken in, particularly the speaker as well as the components.

    i would also recommend spreading the amps out so that it gives you a fuller sound and it may actually be easier to compare and adjust the two with your aby pedal. also may try the top boost on one and normal on the other. i run my aby pedal into both channels and tweak until i like it.

    play music!
     
    RoscoeElegante likes this.
  12. Bluego1

    Bluego1 Tele-Afflicted

    Age:
    57
    Posts:
    1,612
    Joined:
    Aug 3, 2018
    Location:
    Spokane, Washington
    Isolate the ab box as an issue by removing it. Plug each amp into the same wall outlet one at a time and play through them. What do you hear?
    Edit: put them in the same position on the floor, too.
     
    RoscoeElegante likes this.
  13. Bearzooka

    Bearzooka TDPRI Member

    Age:
    52
    Posts:
    59
    Joined:
    Aug 5, 2018
    Location:
    none
    Thanks guys. Both amps have the same speaker, greenbacks. About a month ago I played some music through them both for about 8 hours pretty loud to try and break the speakers in. Im going to reverse them and try them side by side to see if that helps.
     
    Bluego1 likes this.
  14. RCinMempho

    RCinMempho Friend of Leo's

    Posts:
    2,119
    Joined:
    Jul 8, 2003
    Location:
    Maryville, TN
    8 hours might not be enough. It took my Cannibus Rex 12" about 30 hours to break in.
     
    muscmp and RoscoeElegante like this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.