Major flaw with AMPEG PF-500 / 15?

[ingmar808]

I love the tone and practicality of this amp, but it appears to have a major defect. When using the head as a pre for recording, playing a P-bass with a pick, there are lots of nasty pops on the attack transients.

 

Backing off the gain to below 12 o'clock gets rid of the problem - but also gets rid of the saturated sound I wanted in the first place.

 

The clicks and pops aren't noticeable through the cab - maybe the power amp and/or the 15" speaker aren't fast enough to catch them?

 

Anyone else notice this, and do you have a solution short of miking up the cab? I've tried all the output options: XLR out, pre amp out, fx send - same result each time.

 

Is this a fault with the Ampeg, or do all Class D amps do this to some extent?

[Bill Fitzmaurice]

Since you don't hear the pops and clicks through the speaker chances are they're happening in frequencies too high for the speaker to reproduce them. It wouldn't have anything to do with the Class D power amp, as the sends come from before the power amp. You should be able to adjust the EQ on the recording desk channel strip to get rid of those offending frequencies.

[fretmeister]

What Bill said, I reckon.

Speakers really are a low pass and a high pass filter in a box. My own cab tops out at about 4-5Khz (no tweeter) but if I plug into something else with a tweeter I get all manner of crap at the top I don't want.

 

Have you tried running an IR of a suitable cab in the DAW? Record it raw, and then add the IR after. Then you can change the IR as much as you like without re-recording.

It's always a good idea to record a DI track at the same time too. That way you can completely change everything. Amp / FX / Cabs etc etc.

 

[Chienmortbb]

To be honest the can adds as much to the sound as the amp so it is better to record directly and add the processing after. I use a Focusrite for recording or even my Soundcraft Mixer, never straight from the amp. It’s not what it is designed for. 

[police squad]

When I first DI d my PF500 the guy on the desk said it was a very hot signal.

I've had no problem with mine at all. Just turn the gain down on the desk and all is/was fine (I dont use my PF500 as my main now, it's just a spare)

[ingmar808]

Thanks for the replies... The spikiness is way beyond solving with a bit of EQ - also that would just be trying to hide the problem rather than find the cause. Turning down the gain on the desk wouldn't help, as the spikes are caused earlier in the chain.

 

I think it's down to something over-sensitive in the pre-amp design. It sounds great played with fingers, but with a plec it seems to only work with modest gain before getting nasty.

[fretmeister]

But you don’t hear it with a cab.

 

So record with a cab or an IR of a cab. There’s loads of amps that sound crap without a proper bass cab. 
 

Can you post a sound clip? Just the bass, nothing else.