dagrev

Look for a fuse getting dark. My 300 happened to have a one of the fuses getting dark. Now, that may have been a cause or a result of something causing the buzz. I once cleaned an old tube and it had a mum afterwards. At this point I'm at my depth on electronics. Hope you get it sorted out. Note the upper fuse.

New ABM 300. Quick ABM update. Got the new one yesterday. Much more quite. Very slight sound where you know it's on, but that's it. Nothing like the buzzing before. Just it time to grab it for rehearsal using the same Jbass I used Sunday for a good comp. Noticeably more mids (nothing honky), just more punch, and noticeably not as big sounding as the older 500 in the lows. A little brighter as well. More tube sound as well on the 300. Sounded great. I like big, thick bass so I'll have to do some different EQing, but will have to do so in a way that I don't cover up that nice punch. Normally I have the shape (scoop) disengaged and the bass may be flat or 1:30 at the most depending on the bass. I was more at 2:30 by the end of rehearsal. Great sounding head. Ashdown continues to impress. (Said the Ampeg guy who has now owned almost as many Ashdowns as Ampegs. Currently have 3 Ash, 3 Pegs.)

Update: Took the 300 to rehearsal to check for buzz. I noticed it. Hard to tell how loud with people talking, etc. Not loud, but still there, so I think it will be gong back. But, I will take the 500 over there tomorrow to compare before sending it back. The fans on those covers a little buzz and with the 300 having no fan noise, buzz is more apparent. Also a little louder on the 300 as well. Nice sounding amp otherwise. Not a big in the lows or all around heft, but it's got knobs and sliders to fix that. Sorry about the incorrect place to post this. At another forum where I'm a regular in the States, this is where such discussion would go, so my apologies.

@ClusterOne Thanks for the info. Same buzz with cable but no bass. Briefly this morning when I had some time I connected both the 500 iii and the 300 iv and left an instrument cable unconnected to a bass. Both make the same noise/sound, with the 300 being a little louder. Touching the tip, same sound. And, kind of "shorting" the cable trick by touching the sleeve and then the tip, both make noise when this is done (louder hum). I had input/output low as it was early. At lunch will try again, but I'm beginning to wonder if it's not something in the house since neither one was quite when I "short" out the cable. (Said the person who knows nearly nothing!) Wed night I will try another location entirely and see what happens.

I tried the head upstairs with with different cab. Not as buzzy, but still there. Oddly enough when I would move the Pbass around the sound would change. @ClusterOne may be on to something as it or the cords seemed to be acting like an antenna (maybe). I tried my 500 iii and did notice some of the same thing when in front of the cab downstairs. I never noticed it before because the two fans cover it up, unless right in front of the cab. Not as loud, but something there nonetheless. I think Wed night I will take it to where it will get the most use and see what happens.

Thanks. You may be on to something. It does sound very similar to what one might get from a single coil and if you move something it would change or go a way. This just doesn't go away. I may try it in another room or location before sending it back just to make sure as a last ditch effort to keep my good deal.

I just heard back from a bass player friend who has a PhD is electronic engineering, also happens to know Mark Gooday a little. He said to return it. Should not be that way and could be simple or expensive to fix. I emailed the big online seller and they said they would send a free return label. So my great deal kind of went out the window. Bummed about that. Might ask if they have a tech in the area as I would really like to keep it. Such is life. I appreciate all the help and advice. If something changes, I'll update.

Yes, same noise. But no noise if nothing connected in the input. Does get louder if output is raised. Never goes away even is output is all the way off.

Clip of the bizz. Will have to turn it up a little. It's more quite in the clip than live. ABM.mp3

I was able to use a car trim removal tool to carefully get the plugs out. Changed valves and that was not is source.

Thanks. For the heck of it I just emailed Ashdown to see what Dave says. I'm really more concerned about the seller not taking it back if turns out to be an issue. I did mention that valve no valve or EQ changes affect it. Whatever Ahsdown says may likely confirm your thought about the valve, or provide basis that it may be more than that (as much as can be known without listening to it), and assure the seller something is a bit off.

Thanks. Yes, I'm wondering about that. It would make for an easy fix. I have newer JJ in my 500 and an Eden in a box. I may try the Eden (which was quite), before contacting seller or Ashdown to rule it out. Yet as I think about it, I don't want any indication of me opening the head up as they may not take it back if I choose due to the hiss becoming more than I want to listen to. Those screw covers may not look perfect after prying them out.

I'm slightly concerned about the slight buzz when the amp is on. The old 500 iii is dead quite. For kicks I asked an ai if this was a problem and it said it was due to the some differences in the iii and iv. Anyone else encountering this or do I potentially have a problem, and maybe why it was returned and resold?

New ABM in the house. Original box and manual. Mint condition with no signs of use. Has that new smell. Not my settings, I just turned it on to make sure lights came on, everything worked and it made bass sounds. More of a slight pop when turned on and click and common speaker 'puff' when turned off. The 500 is silent on and off. Doesn't seem to be a problem, just unexpected. The detent on the output have me in between, one being nothing and the next one being too much for tube grind at home. Got it managed, but only fooled with it enough to make sure it worked. I definitely have more room to adjust the input and overall volume. The single fan is silent compared to the two fans on the 500 which was noticeable. This one is barely on and nice and quite. I imagine it's variable and speeds us as needed. I'll bring the 500 home tomorrow to compare. The 300 may be a tad brighter.

Thanks guys! @AlexMUKInteresting. What was your goal in this change and how did it affect the tone, or did it?