Ampeg PF350 (ss) vs PF500 (mofset)

[jeff7bass]

I'm considering one of these heads but noticed a difference (other than power, few other features) and that's the pre-amp on the PF500 is mofset while the PF350 is solid state. What effects on the sound (or otherwise) does the mofset pre-amp give the PF500?

Thanks.

[BassmanPaul]

MOSFETs are SS and are usually used in the output stage not the pre-amp.

[seamonkey]

There are mosfet op amps - a few cents more, and a more "ideal" op amp.
Mentioning MOSFET is just for Marketing here.
Ampeg shouldn't really mention the types of devices used, even for output.
They should just publish specs and actual measurements.

These heads are so inexpensive, and look to be very well built, that they really don't have to do measurements for the crowd they will sell to.

I'm sure each if voiced a little different, so you going to have to try them at home and on the venue before deciding.

[jeff7bass]

Thanks guys. Pretty sure the mofset described in the PF500 was in the pre-amp as both used class “D” amps.
Regardless, there was a lot of useful information in the PF350/PF500 thread so I’m fairly certain that for my purposes, the PF350 is the better fit. I was looking for more grit and lower volume levels since I’ll be powering a single 12” cab with it.

[okcrum]

If it's a discrete MOSFET (and I think it is) the marketing is in the fact that it behaves more like a triode tube than a regular JFET. They can also be made quite low noise. MOSFETs were first widely used as RF preamps and mixers.

[Frankjohnson]

Originally Posted by jeff7bass

Thanks guys. Pretty sure the mofset described in the PF500 was in the pre-amp as both used class “D” amps.
Regardless, there was a lot of useful information in the PF350/PF500 thread so I’m fairly certain that for my purposes, the PF350 is the better fit. I was looking for more grit and lower volume levels since I’ll be powering a single 12” cab with it.

Goose the preamp side more, maion volume less....grit will follow. I use a 8 ohm 12 " cab sometimes....it be as Gritty as I want it!

[jeff7bass]

But is it True Grit?!!!

[Slackerprince]

Originally Posted by jeff7bass

But is it True Grit?!!!

You'll have to put on an eye patch to find out.

[60bass]

Originally Posted by jeff7bass

Thanks guys. Pretty sure the mofset described in the PF500 was in the pre-amp as both used class “D” amps.
Regardless, there was a lot of useful information in the PF350/PF500 thread so I’m fairly certain that for my purposes, the PF350 is the better fit. I was looking for more grit and lower volume levels since I’ll be powering a single 12” cab with it.

With a single cabinet why not spring for the PF500?

If you're going to use an 8 ohm cab, (which is what most players will do so they can add another 8 ohm cab later) you get 250 watts with the PF300 and 300 watts with the PF500 @ 8 ohms.

You're never going to hear that 50 watt difference. I think with the wider tonal options on the PF500, you'll still be able to dial in some grit at lower levels. Probably more so considering the switchable mids on the 500. Still the best way to know for sure is to try both heads with the cab you want to use and your bass.

However if you ever want to add another 8 ohm cab down the road, that 500 watts on the PF500 will get you up there in volume pretty good. It's always nice to have more power and not need it, than to need more power and not have it.

Just my .02 YMMV

Keep Low