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Ampeg PF500/PF350 - part 3, I think

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#862
I finally managed to understand this cutting out thing. You need to be running the head very hard into a 4 ohm load. I turned it up to a volume too loud for anyone's good and it "cut out" but it sure seems like a limiter or protection circuit to me. It kicked on when the pickups in the old MIM J went microphonic.

There is a lot of power on tap before you get to that point. I could see how someone running the head into a 410HLF or a 212, especially if boosting lows, could conceivably run out of steam in a loud band. If faced with some Triple Rect's and all I had was my PF and one of those cabs, I'd run for the hills. Not that it couldn't do it with a little EQ tweaking, it's just that I like my hearing. ;)

For reference, I tend to run my bass knob 9-11 o'clock, mids position 1, mids 2 o'clock, treble flat, and run an MIM J with both pickups on. I couldn't ever see running out of volume with those settings and the PF500 and PF115's. Maybe some heads had a problem but this one is just fine IMO. It'd be silly to expect anything more out of this particular unit it than it already gives. If someone ran my PF500 and it cut out, they need more cabs and maybe more power too. I can't comment if that's the same "cutting out" that everyone else experienced but it seemed like normal amp self-protection under extreme conditions to me.
 
#865
fingerbun said:
Did you get any warning before it cut out?
Click to expand...

My ears said the cabs can't really take any more juice without farting giving me the impression that I'm dumping some serious power into them. I turned down the bass from flat which let me get even more volume. My ears and reasonable expectations from the gear gave me a good idea of far I was pushing it and that was farther than I wanted to be at that point. No farting or real stress but I'm sure that they were darn close. It was when I went to turn it down that the pickups went microphonic and started feeding back. It took it maybe half of a second to momentarily shut off the signal. Came back on just about as fast when I muted the strings. I'm thinking it's got some circuit post-master volume in there that mutes the signal if it gets too hot.
 
#867
christw said:
I finally managed to understand this cutting out thing. You need to be running the head very hard into a 4 ohm load. I turned it up to a volume too loud for anyone's good and it "cut out" but it sure seems like a limiter or protection circuit to me. It kicked on when the pickups in the old MIM J went microphonic.

There is a lot of power on tap before you get to that point. I could see how someone running the head into a 410HLF or a 212, especially if boosting lows, could conceivably run out of steam in a loud band. If faced with some Triple Rect's and all I had was my PF and one of those cabs, I'd run for the hills. Not that it couldn't do it with a little EQ tweaking, it's just that I like my hearing. ;)

For reference, I tend to run my bass knob 9-11 o'clock, mids position 1, mids 2 o'clock, treble flat, and run an MIM J with both pickups on. I couldn't ever see running out of volume with those settings and the PF500 and PF115's. Maybe some heads had a problem but this one is just fine IMO. It'd be silly to expect anything more out of this particular unit it than it already gives. If someone ran my PF500 and it cut out, they need more cabs and maybe more power too. I can't comment if that's the same "cutting out" that everyone else experienced but it seemed like normal amp self-protection under extreme conditions to me.
Click to expand...



finished the gig with a crappy backline 600 on about 3.5-4 (on scale of 10 ) so it was not that loud. Maybe there are just some units that are not well built. Why is everyone trying to try and blame the users. Been gigging for 38 years and i have never had an amp behind me that i couldn't trust
 
#869
christw said:
My ears said the cabs can't really take any more juice without farting giving me the impression that I'm dumping some serious power into them. I turned down the bass from flat which let me get even more volume. My ears and reasonable expectations from the gear gave me a good idea of far I was pushing it and that was farther than I wanted to be at that point. No farting or real stress but I'm sure that they were darn close. It was when I went to turn it down that the pickups went microphonic and started feeding back. It took it maybe half of a second to momentarily shut off the signal. Came back on just about as fast when I muted the strings. I'm thinking it's got some circuit post-master volume in there that mutes the signal if it gets too hot.
Click to expand...

I see it as an engineering thing. For a lot of my gigging I relied on Peavey gear and it tool every piece of abuse I would throw at it. I didn't drive into clipping and I turned down if the speaker started to fart. I assume it was engineered with margin for error, and it still works 30 years later.

I have not owned nor gigged with an SVT, but I associate them with the same characteristics. Solid, and heavy. As I understand it, they are designed to work with you driving the gain stage hard, you will only get optimum tone when the light is flashing.

Then comes along a PF500 that is loud, but dies more or less without obvious warning if someone drives it the same way they would drive an SVT?

I don't get why they didn't engineer it with a little more wiggle room. I don't think they are the only brand with this issue, I have read similar (albiet far less prevalent) reports about Markbass.

Is there something about Class D amps that means they simply can't make them as robust?
 
#870
But you CAN drive it hard. I do it all the time with my Micro VR and PF350 and never had a cutout. I've done it with a PF500 too, although it was at the very volume tolerant GC I go to ;) If it cuts out, it's either a protection circuit kicking in or a defect in manufacturing IMHO.
 
#871
Just at thought, but has anyone measured the power out when one of these amps starts cutting out? It could be that you are just driving them beyond their capability. Remember, with the same cabinets, 500 watts isn't going to sound much louder than 250 watts.
 
#873
The amp. Some amps have a protection circuit when running past their capabilities or out of their specs. To be honest, I don't know if the Ampegs have it, but I would imagine they might.
 
#874
fingerbun said:
I see it as an engineering thing. For a lot of my gigging I relied on Peavey gear and it tool every piece of abuse I would throw at it. I didn't drive into clipping and I turned down if the speaker started to fart. I assume it was engineered with margin for error, and it still works 30 years later.
Click to expand...

My Peavey combo is almost as old (1985) and I've had the same experience. And I did drive mine into the clip light all the time. The thing is indestructable.

But the pf500 sounds way better, so I hope it doesn't let me down. The Peavey isn't really loud enough to back up the Ampeg anyway, even if it is a very loud 40 watts...

If what I read above is correct, than running it into one 8 ohm cab I should be fine. They should've built it for 2 ohms and rated it for 4.
 
#876
JimmyM said:
Some amps have a protection circuit when running past their capabilities or out of their specs. To be honest, I don't know if the Ampegs have it, but I would imagine they might.
Click to expand...

Would there be any way, short of a Papal decree, to find out???
Not putting you on the spot Jimmy.

I may try the customer service number tomorrow, but I would guess the customer support folk may not be savvy to the engineering specs of the amps.

It would be nice to find out, once and for all, what these amps are actually designed to do. OR it would be nice to find out that if these issues come up then it is indeed a sporadic manufacturing issue.
 
#878
The cutting out problem that folks are experiencing with 4-ohm setups is probably
more of an issue for those running ported cab(s) than sealed cabs.

The amp will see the peak demand for power at the ported cab's tuning frequency.
If your cab is tuned to 49Hz, then a G (E string, third fret) is going to be the
most dangerous note, at VOLUME! The danger zone extends out a couple of
notes on either side of the port tuning frequency.
 
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