4 ohm into 8 ohm/sound cutting out

[markmeloney]

I purchased an Ampeg PF500 and GK 410 from a friend because my 20 year old Peavey TNT combo just wasn't cutting it anymore. I primarily play drums, I really don't know much about how amp watts/ohms work together.

Anyways, I've had zero problems with the amp until a few days ago. I was playing in my garage and all of a sudden my sound cuts out, sounds a little farty, slowly builds itself back up to volume with a "POP" sound, and then sounds fine. It does it twice in about 30 minutes. I've got nothing cranked to 10 in the slightest, I set up up the pf500 correctly and I'm not clipping and causing the thresh light to go on.

I asked one of my guitarist friends and he said I could ruin my head because I've got a 4 ohm head going into an 8 ohm cab. I've researched and researched, but nothing is giving me a really cut and dry answer. I know it's a big nono with tube amps, but there isn't a definite answer I've seen for solid state. It seems like the only real "problem" is that the amp is gonna push less watts. My friends says it'll ruin my head, half the replies on threads here I've seen say it. The manuals for the pf500 and gk 410 say it's fine, and the other half of replies on threads here say that's fine.

My bass has active pickups and I was going through my fuzz pedal and it's possible maybe those 2 batteries might need to be replaced. I also live in a an old farmhouse with bad wiring, stuff like using a vacuum or microwave dims the lights, which I also read could have an effect on amps.

But yeah, I'm at a loss. I was enjoying playing it, but I don't wanna take some guy on the internet's word for it and continue playing, just to fry my gear.

Thank you.

I had some really farty sound and cutting out at one point and was sure I blew a speaker. then I jiggled the speaker cable and realized I just had to replace the cable. talk about a sigh of relief

 

[MVE]

For Gods Sake, start with checking the battery before you send the head in for repair or rewire your house!!!
Better yet, try another signal into the amp (another bass, guitar, keyboard, iPod,.... Whatever...)
I'll bet dollars to donuts, you have a bad battery, cable or dirty jack.
PS. Your guitar friend is a moron and should stop giving advice about things he knows nothing about.

 

[Robert Sperling]

As already stated, 4ohm capable head driving an 8ohm cabinet will not cause this. My best guesses are:
1) Your unreliable power source... You could try a power conditioner but I wouldn't spend big $ on that.
2). Could be using the wrong type of or broken cables (eg, instrument cable for speakers, which are too thin).
3). Overloading the preamp section with too hot a signal from your effects.

If it were me I'd try it without any effects, then try switching cables then using a power conditioner to try and
narrow down the problem (least expensive to most expensive options).

 

[bassrich]

Sounds like you need to replace the active bass batteries or pedal batteries try running the pedal on an ac adapter to see which is the culprit

 

[lz4005]

I also live in a an old farmhouse with bad wiring, stuff like using a vacuum or microwave dims the lights, which I also read could have an effect on amps.

That can seriously damage your equipment. And cause exactly the problem you had.
Check your batteries regardless, but those generally fade down and then don't come back up.
Bad cables and/or connections could do that if you moved around, but I bet it was the bad mains power.

 

[Korladis]

So, first of all, check all batteries. Check all cables. Check the wiring on your bass. If everything but the head seems to be working just fine, then contact Ampeg.

This head should not be giving you any problems going into an 8 ohm cab.

 

[LiquidSignal]

Well, an update.

Fresh batteries in the pedal and bass, and I haven't had the problem happen again.

I also haven't been playing it while other people have used the microwave/vacuum.

idk man.

Thank you for all the replies and help.