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Ampeg/Avatar problem driving me nuts

thedudebrah

thedudebrah

Jan 9, 2012
657
61
Philly suburbs
www.avenuekings.bandcamp.com
#1
Long winded post incoming...

I've recently tried to majorly downsize my practice rig. Picked up an Avatar B112 (4ohm eminence driver/tweet/ported) to pair with my PF500.

The cab is a used craigslist deal but it sounds killer in my room at low volume.

The PF500 was old and road beaten. One of my first practices with my new band and the amp was cutting out when the signal peaked. Both the peak and fault lights would flash and then the signal would come back in. I recalled reading about this issue so I started shopping for a new head. Tried a markbass Big Bang and an Orange OB500. Disliked both with the cab, couldn't get my tone and ended up returning them in favor of a brand new PF500.

I picked up the new head the day before a gig, didn't get a chance to demo it. Took it right out of the box and straight to the venue. Once it warmed up, my signal started cutting out again, but with NO FAULT LIGHT this time.

Since I was mid gig, in between songs I would swap cables to spares to no avail.

I took everything home and started swapping things around to replicate the problem and I cannot reproduce the issue. Used the exact same cables, same bass and cranked the volume to gig level and it played fine. Used two different heads into the cab and I couldn't get the cab to cut out. Used the PF500 through two spare cabs I have. No issues. I'm scratching my head.

Do the B112 cabs have any issues internally that would cause the signal to cut at peaks? Did I get a junk PF500 out of the box?

I also tried my bass and cables into a variety of other amps and had no issues with any of them. I'm at a loss.
 
#7
I can only relate my personal experience with the "two" PF-500's I owned.
First one burnt out 30 seconds into it's first power-up, (it was plugged into a 8 ohm Ampeg PF-115.)
Second one burnt out at the beginning of the second set of the first job I used it on, it had maybe 5 hours on it at that time. (It was plugged into my two, 8 ohm, Avatar Neo 210 cabinets.)

A friend's PF-500 went out on him while plugged into his 4 ohm SWR Goliath Senior cabinet.

I've since ran my Avatar cabinets with my Hartke LH-1000, my G.K. MB-800, and my Mesa M-6 bass heads with absolutely no problems.

My bet is there's something going on in these PF-500 heads.....not the cabinets their plugged into.
 
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#9
Fab Superlative said:
This mainly occurred at the venue during a gig? seems like bad venue power?
Click to expand...
I thought that at first since I couldn't replicate it at my home, but the issue appeared again last night at band practice at the drummer's home. The power there seems clean as the PA, two other guitar amps and the back up bass amp function in the room without issue
 
#12
There can also be an issue with the cab's crossover that can cause class D amps (like a PF-500) to oscillate. This causes (inaudible) overdriving and output cycling (self-protection). The PF-500 have has a history of this happening, but it could also be an older crossover design in the cab you bought and not an "amp fault".
 
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#13
"seems like bad venue power?" via Fab Superlative

This seems obvious but it's caused problems for me in the past, if the 110 volt power going into the amp is too low or high it will shutdown the amp. At bars or restaurants with a lot o use it can go allover the place. Use a volt meter to check, or a power conditioner is the way to go, but more crap to carry. I sold a new svt 300 tube ampeg because it would always shutdown. ( also I don't need that much power, but it sounded nice) The old 70's svt I have, that's beat to hell, never shuts down or blows a fuse. Bad power in, always caused my problems when cranking the volume, especially with circuit board amps, it's more of a problem.
 
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#14
Reason why I suspect something is wrong power wise for the OP, is because he cannot duplicate the faults at home.
The fault only seems to occur at different locations.
Even before class D, amps started hitting the scene I was tired of getting zapped & shocked at certain venues we would frequent. I started to carry one of those receptacle testers around in my gig bag, and sure enough started to discover improperly wired power outlets. Lack of ground, was far and away the most common problem I found (no pun intended :D) and I still continue to encounter them to this day.
And I agree with you, from my personal experience it does seem to me that pcb, amps are more sensitive to power fluctuations as well. Cutting out, going into protect mode etc.
 
#15
ITS THE CAB.

I finally was able to reproduce the issue at my home. Used all known working cables, played through my 410HLF, no problems at all. Swapped the speaker cable into the Avatar and it started cutting out. Went back to the HLF, no problem.

Plugged in my old PF500 and it seems to work fine through the HLF. I'm still within the 45 day GC return policy so I'm gonna return the head and look for a used cab to use in the downtime that I have the Avater checked out.
 
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#19
B-string said:
There can also be an issue with the cab's crossover that can cause class D amps (like a PF-500) to oscillate. This causes (inaudible) overdriving and output cycling (self-protection). The PF-500 have has a history of this happening, but it could also be an older crossover design in the cab you bought and not an "amp fault".
Click to expand...

thedudebrah said:
ITS THE CAB.

I finally was able to reproduce the issue at my home. Used all known working cables, played through my 410HLF, no problems at all. Swapped the speaker cable into the Avatar and it started cutting out. Went back to the HLF, no problem.

Plugged in my old PF500 and it seems to work fine through the HLF. I'm still within the 45 day GC return policy so I'm gonna return the head and look for a used cab to use in the downtime that I have the Avater checked out.
Click to expand...

Glad you figured it out! I was also having big problems with the X-over in my fearful knocking class D heads into protection, sometimes I'd get a chirping self-oscillation sound too as the head would repeatedly drop to protection and come out, chirp, drop.

After two tries and a number of months my tech seems to have resolved the issue. He claimed an older class A/B amp would not have had the same trouble, so I got an old LM-III as a backup amp.
 
#20
gkbass13 said:
Could it possibly be due to trying to get gigging volume out of a 4ohm 1x12? I imagine that will cause some seriously clipping from the amp when trying to compete with a drummer and other band mates.
Click to expand...

I thought the same until it happened at practice as well. One of our guitar players was absent and the other plays out of a 15w Orange head and a 112 at practice. The drummer plays pretty mildly.

The signal cuts out at anything over bedroom volume. I never run this amp wide open but I would expect the driver to distort and fart before the signal just totally cut out. I've never had a cab act this way before so if I'm wrong I'm all ears.
 

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