Does PPIMV neuter an amp?

[jchrisf]

I've got a Ceriatone 2204 that has PPIMV and I can play it at whisper volumes. I can't even control my 20 watters as well as this amp. I've always thought the tone was great but a little smooth and tame. I'm getting ready to build a Mojotone Brit 50 so I bought the Fryette PS-2A so I can attenuate it and have a fx loop when I'm done. I ran the Ceriatone through the Fryette and this amp has some balls now. I'm not sure if the Fryette is coloring the tone or if the amp is now able to shine. I love it more now. I basically only used the volume on the Fryette. Presence, Depth and the switches were all turned down.

I can barely crack the volume on the Ceriatone here in my house without the PPIMV/Fryette because it is so loud... so I've never been able to experience it with much volume. It is way too loud before 1 on the volume control. I still play pretty loud at home but this amp gets loud fast.

 

[TheGreatGreen]

I depends. I have a Suhr SL68 that I run into a reactive load, and the interesting thing about an amp with a PPIMV into a reactive load is that the control really lets you hear the difference between what a cranked phase inverter does to the sound, vs what cranked power tubes do to the sound.

To me it seems like a cranked phase inverter distorts pretty evenly over the full frequency spectrum, while with the power tubes, the nature of impedance curves means those power tubes hit their headroom limit in the upper treble and low bass much faster than they do in the mids, so as you turn up the master, the treble and low bass tend to stay the same volume while the mids keep getting relatively louder and everything gets more compressed.

With the master volume turned down to whisper volumes and the front volumes cranked, you get a clipping phase inverter tube and clean power tubes. This results in an obviously quite distorted tone, but one that remains quite bright and strident. In this case I think the lack of the compression from the power tubes means the sound does feel a bit more strident and modern, but you also lose some compression as well.

Adding some push from the poweramp will tend to round off the highs and add compression, which makes the amp feel thicker. So yeah there will be a difference.

However I'll also say that if I run the SL68 at whisper quiet PPIMV volumes and use a low pass filter in post to simulate the highs getting rounded off, I can get quite a bit closer to the sound of pushing the power tubes.

 

[DanTravis62]

There's certainly a difference but I dont think "neuter" is the correct description.

The phase inverter distortion is more balanced along the spectrum and power tube distortion is more mid focused (at least with marshalls ime)

It's more a matter of what tone you're trying to get, and there's more than one way to skin a cat in this case.

Generally, the power station does the opposite of "coloring" the tone. It can add or subtract a tiny bit of presence and a tiny bit of depth but they don't lie. That's what the amp sounds like.

 

[harddriver]

Yes a traditional Lar/Mar PPIMV anything below 25-50%(2-5) you will start to lose your NFB in the output signal which you may feel or perceive as loss of highs and the tone can get a bit fizzy especially at so called whisper quiet volumes it really starts to affect the tone. The old Rich mod PPIMV's were worse than the Lar/Mar regarding this.

To alleviate this I always run the PPIMV in conjunction with an attenuator, PPIMV set to at least at or above 2 to 5, this significantly cuts volume but you retain your NFB then set the attenutor to -4 or -8DB or more depending on how quiet you want the volume. You experiment to find a happy medium to suit the end result you want.

 

[fusedbrain]

PPIMV messes with the negative feedback.
PPIMV vs attenuator will sound different due to this effect, notwithstanding the effect that power tube saturation has on the sound.
My experience with PPIMV's in non-master volume amps has been that to get the best results, you need to find your ideal PPIMV level, and tune the negative feedback to that setting.
Edit: Harddriver posted while I was typing my reply

 

[311boogieman]

You guys should quit talking so sexy, I'm getting hot