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Had to take my Ashdown to the doctor.

Discussion in 'Amps and Cabs [BG]' started by no4mk1, Mar 11, 2005.


  1. no4mk1

    no4mk1

    Feb 21, 2003
    Seattle, WA
    I have an Ashdown ABM EVO 300 head that I run through a mini 115 and a mini 112. It has been a very solid amp for the last two years and approximately 25 gigs.

    When I plugged it in at rehearsal last night I was only getting about a third of the power out of it. It wasn't distorting, it was just really weak. I checked both cabs, and they both seemed to be fine. I also made sure it wasn't the bass or cabling.

    It also didn't seem to make a difference whether I was playing through the solid state side of the pre-amp or the tube side.

    So I took it in to Condor Electronics here in Seattle. Hopefully they can find the problem quickly.

    While they are at it I am asking them about the feasability of upgrading it to 500 watts which was possible to do with the previous version.

    So maybe a positive will come out of a negative, but I hate being without an amp. I especially hate spending band fundage on equipment repairs, but I guess it can't be helped. :scowl:

    Chris.
     
  2. no4mk1

    no4mk1

    Feb 21, 2003
    Seattle, WA
    Well... I just got it back.

    The tech replaced a faulty 1st stage op amp and installed a machine pin socket for easy A/B comparisons between different units. He installed a 4560 which he says has a quiter noise floor and has more gain bandwidth than the stock TL072. I'll I know is that it works now.

    The biggest thing I noticed was that the "grind" or tube stage works now! Before, I played the amp with the grind knob all the way over on the tube side, and I only got a bit of "tubey" sound, and that's the way I thought it was supposed to be. But now with the new op amp, I actually get a grindy (good sounding) distortion on the tube side. I'm thinking that the stock op amp was probably just barely working before and I just didn't know any better.

    Do you folks with ABM EVO amps get an actual distortion sound on the tube side?

    It's kind of like I've got a brand new amp now! It always sounded good, but now I've got a much larger range from clean to distorted than I had before. :)


    As far as the power upgrade, turns out that you can't upgrade the power section to 500 watts as they put in bigger transformers on the bigger amps. So while you may have been able to do it on the first generation amps... No go on the newer ones.

    Cheers,
    Chris

    P.S. The repair only cost $100.00, and the turnaround was only a week and a half. Half of the quoted 3 weeks. For all you folks in Seattle, the guys at Condor are great techs!
     
  3. Hey Man......That is really good to hear....missed your first post...but I bet your glad somebody cares! .............
     
  4. no4mk1

    no4mk1

    Feb 21, 2003
    Seattle, WA
    Heh. Yeah. ;)
     
  5. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    Hey that's great! Always nice to know there is good local support for our buds!

    I really like what I've heard of Ashdown. I spent some time with the EVO 5 head and a Bergie cabinet last summer. That was a fine sounding rig. Wish I could have kept it ... so many amps, so little time!
     
  6. notanaggie

    notanaggie Guest

    Sep 30, 2003
    Hmmm....

    He fixed it, but has no clue.......

    He replaced a FET input opamp in an input stage with a lower input impedance standard opamp.......

    He thinks that the low bandwidth 4560 is actually much better than the TLO72....... Ugh

    At least it works now, so you actually got it repaired to operational.
     
  7. no4mk1

    no4mk1

    Feb 21, 2003
    Seattle, WA
    What does that mean to me in english? :)

    Thanks,
    Chris
     
  8. Th9nker

    Th9nker

    Mar 18, 2002
    I've got a ABM 500 Evo II, It gets downright nasty when I crank the tube up....
     
  9. notanaggie

    notanaggie Guest

    Sep 30, 2003
    The original "TLO72" with a "high impedance" input would load the input (your bass) considerably less than the new "4560" part.

    The load the TLO72 puts on the bass is much nearer to the tiny load a tube would put on it.

    How big the difference is would depend on the rest of the circuit.

    What you might find is less high end, a little "lower toned" or middy ....maybe not too relevant to you, maybe it is.

    If your basses are all active, it may not matter much.
     
  10. no4mk1

    no4mk1

    Feb 21, 2003
    Seattle, WA
    O.K. Thanks. That helps a lot!

    Question. If the original op amp was faulty, would that account for not having any "grind" before it finally failed?

    I always assumed that the grind control was a misnomer, because all it did was make the attack a bit spongier and a bit "warmer" sounding. Now it works like it was supposed to I suppose with subtle distortion starting around 9 o'clock and ending in fairly high-gain sounds when dimed.

    Thanks,
    Chris
     
  11. no4mk1

    no4mk1

    Feb 21, 2003
    Seattle, WA
    Thanks. That's exactly what I wanted to know. Apparently my amp has been faulty since I bought it and I didn't know until it actually failed. At least it was faulty in a musical way! I actually kind of miss the way it sounded before, but I'm looking forward to playing with the grind at rehearsal tomorrow! :p
     
  12. bino

    bino

    Jun 27, 2002
    Orange County
    You may have gotten an "upgrade" in the process of having your amp repaired. I had emailed Ashdown about the valve feature and they said the older EVO models had much less grind/distortion than the newer EVO II model. FWIW, I just bought an older, used ABM EVO combo and the valve features sounds about how you originally described yours - only a slight difference.
     
  13. no4mk1

    no4mk1

    Feb 21, 2003
    Seattle, WA
    Well... Unfortunately, the story goes on.

    When I got the amp back, I took it to rehearsal and tried it out. The grind function worked, but it was still running at 1/3 the power.

    So I took it back. This time he traced everything through (he said he got a schematic from Ashdown) and found another opamp (either right before the EQ or right after, I can't remember) that had gone bad and fixed that. He then disconnected the pre-amp from the power amp and sent a test signal straight to the power amp and he said he got a "to-spec 250 watts RMS at 4 ohms". I asked him if he was sure that the ABM EVO was specced at 250 at 4 ohms, because everything I have read places it at 325 at 4 ohms, and he said no, it is a 250 watt amp. I said OK and took it home.

    I rehearsed with it last week and played a gig with it on Thursday, and it did work a lot better, but it's still not right.

    It is more bass heavy with less high and high mid definition (just like notanaggie predicted) and it "feels" like it is only running at about 80% power now. Better, but not where it was.

    Is he correct that this is a 250 watt amp, or is there still something wrong with the power section?

    Maybe it's possible that since the opamp he replaced is favoring more of the low frequencies that the power amp is having to work harder to produce those tones, and it's robbing headroom?

    Is it possible that there is something wrong with the speakers? They both "seem" to be working with no undue distortion, and it's been my experience that speakers either work or they don't. However, this is driving me mad.

    Cheers,
    Chris