Ampeg PF500/350, part 4

[John D]

Hahaha, I get that. But the thing is, I (ideologically speaking) shouldn't be running out of headroom. Just as another member previously said, these amps aren't fairly rated to be running at 500W. But that's another argument.

Seriously, and not meaning to flame at all, how do you know you shouldn't be running out of headroom? Have you measured your power out at the point of *cutting out*? You may be in for a surprise.

 

[garythenuke]

Perhaps the Ampeg PF cabs are a little off on the ohms and a pair of them will result in a slightly less than 4ohm load which is causing the problem.

Maybe everyone that has had problems can sound off with which cabs they were running at the time.

I can't imagine Ampeg designing and marketing a product as 4ohm and having that be the true limit. Meaning that in every other industry, there is always a safety cushion. If, in my industry, I say something can handle 4kV or a motor can handle 400 amps, the reality is that it can probably handle a good percentage more than that. Typically 10% is not a huge deal. Even 20% does not cause a powerplant shut down...
I would think Ampeg would design their 4ohm stuff to handle down into the mid 2s for short periods of time. If they really are working as designed and cutting out right AT 3.9995ohms, then Ampeg needs to make a much larger deal of it. I've seen speaker cabinets rated at 4ohms test at 2.68ish. That is low, but I don't think it is unheard of. Are we supposed to take a multimeter to all of our speakers now before we play?

Has anyone tested their cabinets that are causing the trouble to see if they are indeed significantly lower than 4ohms?

 

[Bass 45]

Quote:
Originally Posted by Freddels
Maybe everyone that has had problems can sound off with which cabs they were running at the time.
If we keep quoting the newest previous post, we can have a complete list, all-in-one. (I have added my son's cab below the entry from kobass.)

Copy and paste this list and add your own to the bottom:

GK Neo 212-2 (4 ohm)
SVT 810 (4 ohm)
Ampeg SVR-215 (4ohm)
Ampeg PF115HE (8ohm)
Ampeg PF115HE x2 (4ohm)

GK Neo 212-2 (4 ohm)
SVT 810 (4 ohm)

 

[ryanfenderbass]

Seriously, and not meaning to flame at all, how do you know you shouldn't be running out of headroom? Have you measured your power out at the point of *cutting out*? You may be in for a surprise.

Simply put, I run one cab at 8ohms and get plenty loud (just starts to push the cab). I run 2 cabs and it cuts out at less volume than I'm running into 1 cab.

Or

I only have the gain at noon and the volume at 1:00-2:00 when it craps out. That's why.

Sorry I don't have a more technical explanation to why my amp is underperforming.

 

[Bass 45]

Seriously, and not meaning to flame at all, how do you know you shouldn't be running out of headroom? Have you measured your power out at the point of *cutting out*? You may be in for a surprise.

I mentioned this last night - but here is a list of amps that I use that are rated lower than 500 watts that do not cut out at the same gigs that my PF500 does:

Ampeg V4
Ampeg Portaflex B15R
Ampeg SVT 2
Ampeg BA300/115

 

[Bass 45]

I mentioned this last night - but here is a list of amps that I use that are rated lower than 500 watts that do not cut out at the same gigs that my PF500 does:

Ampeg V4
Ampeg Portaflex B15R
Ampeg SVT 2
Ampeg BA300/115

and I have never made my SVT 2 distort - Jimmy

 

[John D]

Simply put, I run one cab at 8ohms and get plenty loud (just starts to push the cab). I run 2 cabs and it cuts out at less volume than I'm running into 1 cab.

Or

I only have the gain at noon and the volume at 1:00-2:00 when it craps out. That's why.

Sorry I don't have a more technical explanation to why my amp in underperforming.

Nothing you've said here ^^^^surprises me, nor does it make me change my opinion. For several reasons that I won't go into, you and I could both be correct. I'm sorry you are having problems, and I honestly wish I could help you. Still, until someone who is experiencing this issue puts his amp on the bench and measures its true performance at the point of cut out, we are all just guessing. IMO

 

[Bass 45]

Nothing you've said here ^^^^surprises me, nor does it make me change my opinion. For several reasons that I won't go into, you and I could both be correct. I'm sorry you are having problems, and I honestly wish I could help you. Still, until someone who is experiencing this issue puts his amp on the bench and measures its true performance at the point of cut out, we are all just guessing. IMO

I will bring mine in tomorrow. Ampeg might be hoping that one of their authorized service centers will figure this problem out.

 

[JimmyM]

and I have never made my SVT 2 distort - Jimmy

Aw, too bad...it's fun as all getout, although it will get you fired from the Century Village Ladies Auxiliary Annual Awards Luncheon.

 

[Bass 45]

Aw, too bad...it's fun as all getout, although it will get you fired from the Century Village Ladies Auxiliary Annual Awards Luncheon.

 

[John D]

Ampeg SVR-215 (4ohm)
Ampeg PF115HE (8ohm)
Ampeg PF115HE x2 (4ohm)

GK Neo 212-2 (4 ohm)
SVT 810 (4 ohm)

They all have these things in common: tubes and a power supply made of beer can sized caps and a huge chunk of Iron and copper in the transformers.

 

[John D]

Aw, too bad...it's fun as all getout, although it will get you fired from the Century Village Ladies Auxiliary Annual Awards Luncheon.

That sounds to me like the voice of experience talking.

 

[Bass 45]

They all have these things in common: tubes and a power supply made of beer can sized caps and a huge chunk of Iron and copper in the transformers.

Except the BA300 - which is class D with a tube pre. This is why I think adding a tube preamp to the PF500 and leaving the PF350 alone (for people who don't need a ton of power - and want to keep it cheap) may be a nice solution.

 

[John D]

Except the BA300 - which is class D with a tube pre. This is why I think adding a tube preamp to the PF500 and leaving the PF350 alone (for people who don't need a ton of power - and want to keep it cheap) may be a nice solution.

I think the tube preamp is significant. I'm not familiar with the BA300, but from the information I can find, it doesn't have provisions for an external speaker cabinet, which may also be significant.

FWIW, my theory on the PF500 is that the power supply, not the power amp, is the problem. I suspect that the power supply is not capable of keeping up with the power amp demands at high volume (power) levels and a playing style that generates large transient spikes. Adding cabinets, boosting the bass EQ, and slapping the base all put high demands on the power supply. I am assuming that the limiter monitors the rail voltage, and if so, the limiter could kick in at apparently lower volume levels, if the power supply, rail voltage was below its normal level. Let the flames begin.

 

[mellotron]

I would think Ampeg would design their 4ohm stuff to handle down into the mid 2s for short periods of time. If they really are working as designed and cutting out right AT 3.9995ohms, then Ampeg needs to make a much larger deal of it. I've seen speaker cabinets rated at 4ohms test at 2.68ish. That is low, but I don't think it is unheard of. Are we supposed to take a multimeter to all of our speakers now before we play?

Has anyone tested their cabinets that are causing the trouble to see if they are indeed significantly lower than 4ohms?

Other than a common ohm meter, I am not sure what you might use to test a cab. Here is a repeat of my post 858 from Part 3 of this long thread:

An audio signal is AC (an alternating current). Speaker ohm ratings are a measurement of AC reactance, not DC resistance, and DC resistance has absolutely nothing to do with audio into a speaker.

Measuring a speaker with an ohm meter uses a DC signal, so does not have anything to do with the 8ohm or 4ohm rating. An 8 ohm cabinet is not really 5.1ohms; a 4 ohm cabinet is not really 2.55 ohms.

 

[peddles]

Just tested this amp with my guitar paired with 2 of the pf15" and the sound was incredible. I love a versatile amp like this, very warm and beefy but just does something to that high end that makes me smile.

 

[Spectrum]

I'm going back to all tube for good, quite honestly, and keep the small amps for backup and the smallest of small gigs.

So wait a minute, first people's amps are cutting out; now you're cutting out too, Jimmy?

I love the way this thing sounds but I'm only running one pf210 cab. I might eventually get a second cab and then I'll start to lose sleep over it.

The good news is that Ampeg makes a really killer solid state amp. Hopefully they are paying attention to this issue and will improve on it. I may go tube someday but for now this thing is awesome on its own, even without any effects at all.

 

[2milehighspike]

Just tested this amp with my guitar paired with 2 of the pf15" and the sound was incredible. I love a versatile amp like this, very warm and beefy but just does something to that high end that makes me smile.

Hell yea, I have been using mine for guitar with a fulltone gt 500 and it puts out the fattest blues tone, another member uses it for keys and says the same thing.

 

[tombowlus]

Except the BA300 - which is class D with a tube pre. This is why I think adding a tube preamp to the PF500 and leaving the PF350 alone (for people who don't need a ton of power - and want to keep it cheap) may be a nice solution.

Well, the PF500 with a tube pre starts to get awfully close to the 7Pro, so my guess is that Ampeg wouldn't want to blur the lines. Of course, if you want a PF500 with a tube preamp, more power, and a modest amount of added weight, the 7Pro is there for you!

 

[ddbassGA]

...Of course, if you want a PF500 with a tube preamp, more power, and a modest amount of added weight, the 7Pro is there for you!

But no flippy...