Did I just get burned? Sketchy used AG500 (video)

Discussion in 'Amps and Cabs [BG]' started by Rottie Roo Roo, Jun 9, 2021.

  1. Rottie Roo Roo

    Rottie Roo Roo Supporting Member

    Just picked up an AG500 on Kijiji (Canadian Craigslist) and I'm concerned that someone might have knowingly sold me a faulty unit.

    It's partially my fault, I didn't meet him at his house, instead opting to meet him in a public place to do the deed; everything seemed legit. He said it was just collecting dust but everything was working OK last he checked, he was selling it because he'd not used it in a few years. So I paid him the cash, it was a good deal, and when I took it home other than a bit of dust in the pots that cleared up as soon as I gave 'em a few twists, everything was honky dory and I had a nice practice session.

    Well, I fired it up today after putting it in a rather expensive rack case and it started making the strangest buzzing and humming sounds. It did work OK (I see what people mean about the thin low end but it's pretty nice). The buzzing sounds are really bugging me and I hope this guy isn't trying to pull a fast one on me.

    I took a video of it, the guy is still not answering me but he dropped a few cookie crumbs that led to his home address, so, before I rectify the problem I'd like to know if there's a quick fix that can solve the issue the easy way.

    I've posted a video of the issues - the cab is mic'd with a sennheiser e835 through a cheap ART USB mixer, so you should get some idea of the problem.

  2. Rottie Roo Roo

    Rottie Roo Roo Supporting Member

    Do you think the case might have had something to do with it?
    BrentSimons and punchdrunk like this.
  3. JeezyMcNuggles


    Feb 23, 2018
    Santa Maria, CA
    I suck, but nobody really notices
    Try it in a different room, with a P bass.
    BrentSimons likes this.
  4. Rottie Roo Roo

    Rottie Roo Roo Supporting Member

    Still has the buzz in the kitchen. I don't have a P bass but I have a P/J - Same buzz whether full P or full blend (I have it wired V/B/T). It actually doesn't really change whether or not something is plugged in

    I don't want to jump to conclusions but I would be very upset if this guy knowingly sold me something that didn't work properly.
  5. Redbrangus

    Redbrangus Supporting Member

    Nov 19, 2018
    Under The X In Texas
    To the guy's credit, it worked OK for you at first. It sounds like maybe you've got a semiconductor (or possibly a passive component) early in the signal path (first preamp stage?) that's gone south -- a qualified tech could probably isolate and repair that relatively easy. Just to confirm, it still makes that noise when there's nothing at all plugged into the input...no bass or unterminated cable or anything?
  6. Rottie Roo Roo

    Rottie Roo Roo Supporting Member

    The buzzing is relatively unchanged whether or not a bass is plugged in... there are different hissing noises as the various knobs are rotated (which is to be somewhat expected from a high output device) but the bothersome buzz retains its volume and frequency regardless of other parameters - save for it being slightly more pronounced when the unit is engaged (engage/standby button depressed).

    *edited for clarity
    Last edited: Jun 9, 2021
  7. Redbrangus

    Redbrangus Supporting Member

    Nov 19, 2018
    Under The X In Texas
    I'm not where I can do any serious monitoring, but my impression was the biggest change in noise came when you turned the input level up, and while turning the EQ controls had some effect, it was relatively little in comparison to that of the cranking the input level control. Is that perception accurate, or at least approximately so?
  8. Rottie Roo Roo

    Rottie Roo Roo Supporting Member

    Yes, but that's not the noise I am referring to. Those only really become noticeable when the amp is cranked up - I'm less concerned about that as I'm told it's to be expected at higher volumes especially on the 2nd OD channel. If you'll notice in the video there is a steady buzzing throughout that only slightly dissipates when the engage button is depressed. At 1:14 I turn the amp off and you can hear the dead silence.
    JeezyMcNuggles likes this.
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Are you sure (really sure) that your power source is properly grounded and code correct?

    Can you try it in a different building with a known good power source?
  10. JeezyMcNuggles


    Feb 23, 2018
    Santa Maria, CA
    I suck, but nobody really notices
    Ehh, I was thinking that it could just be that particular spot/plug with that amp, at that particular time. Know what I mean? By P bass, I just meant something with a humbucker.
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The buzz is present with nothing plugged into the input. It’s not the bass.
  12. Cowboy in Latvia

    Cowboy in Latvia

    Mar 1, 2015
    Apologies for the possibly stupid question, could it be because of a bad speaker/speakon cable?
    agedhorse and JeezyMcNuggles like this.
  13. Pulverizor


    Jun 14, 2018
    New Zealand
    It's almost completely silent compared to my Rumble! :D
    But should you expect any 500Watt amplifier to be noise free with the knobs maxed out?
  14. Jaco who?

    Jaco who?

    May 20, 2008
    It didn't hum before you put in the rack case? You may have loosened a ground wire somehow. I agree, the hissy sounds with the knobs turned up doesn't seem that unusual.

    Edit: Did you remove the rubber feet to fit it in the case? One of the screws could serve double duty as a ground connection.
    Last edited: Jun 10, 2021 at 5:21 AM
    Clark W, Carl Hillman and Aqualung60 like this.
  15. sxaxsx


    May 23, 2012
    Harrisburg PA
    Selling you a working amp that buzzes with a bass not plugged in doesn't really sound like the guy scammed you. I mean not a very good scam anyway.
    Does the lift ground button change anything?
    Take it out of the case and try it, obviously that should have been the first thing you did after noticing it.
    Reedt2000 likes this.
  16. MrBass617


    Mar 13, 2013
    I have one of these I bought new and used for years without issue. Then it started doing what yours is doing. Hissing noise. I sent it to Aguilar and they changed out a few things and sent it back. Cannot remember what they changed. The problem came back soon after and I put the amp away. Now Aguilar does not service the amp anymore, instead recommending I take it to a general electronics repair shop, and they will provide the schematic. I don't have a great deal of trust for the electronics shops in my area, so it sits as a base for my tube amps at home. Sad.
    The technology in the amplification section is Class T, from Tripath, which is long gone, and Class T went the way of the Betamax. I'm afraid it may be in the power section, but really have no idea. Wish I had better info to relate.
  17. lfmn16

    lfmn16 Supporting Member

    Sep 21, 2011
    charles town, wv
    So it was working, you put in a rack case and started having problems. Did you try taking it out of the case? I'm not a expert, but it seems like that's where you should start - recreate the conditions under which it was working.
    Last edited: Jun 10, 2021 at 7:02 AM
  18. friskinator

    friskinator Supporting Member

    Apr 5, 2007
    Even if it does have a problem, it was an as-is sale. Caveat emptor and all. The seller has no responsibility here.
    mcnach, MHensleyJr, DrMole and 6 others like this.
  19. ficelles


    Feb 28, 2010
    Devon, England
    The trouble with any gear that is out of warranty is the next time it's fired up might be the time it goes wrong. That's why I hate selling gear and prefer to trade it to a store that knows what to expect from used equipment. So the guy could well have been completely honest and you just happened to be the owner when a used amp decided to develop a problem. Caveat emptor always applies.
  20. Thumpin6string

    Thumpin6string Supporting Member

    Apr 25, 2013
    Shoals Indiana
    As stated above, remove from case and check if buzz is gone. You can also try a patch cable between the send and return. Dirty send and return jacks can cause a lot of weird issues.
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