SS Amp Shootout: Seymour Duncan PS700 vs QSC rmx2450

OrganicZed

OrganicZed

Fractal Fanatic
Okay, so there's been a fair bit of discussion on the forum recently regarding different power amps for use with a guitar cabinet. I happen to own a few and thought I would do a non-scientific shootout.

Video with commentary (pardon the mess, my mother in law is visiting and my guitar room doubles as the guest room):



A second video at higher volume without commentary:



Summary:

The two amps definitely sound different. The QSC produces a thicker, fuller sound while the SD has a bit more upper mid going on and it doesn't seem to reproduce the deepest bass frequencies as well. Both videos were recorded on my phone (I know, not the greatest audio quality) but I think the result reasonably reflects the differences I was hearing in the room.

I prefer the QSC tone wise, but the SD is a cool little box considering it weighs only 6.3 pounds. The QSC is just a bit heavier at 44.5 pounds.
 
OrganicZed said:
Okay, so there's been a fair bit of discussion on the forum recently regarding different power amps for use with a guitar cabinet. I happen to own a few and thought I would do a non-scientific shootout.

Video with commentary (pardon the mess, my mother in law is visiting and my guitar room doubles as the guest room):



A second video at higher volume without commentary:



Summary:

The two amps definitely sound different. The QSC produces a thicker, fuller sound while the SD has a bit more upper mid going on and it doesn't seem to reproduce the deepest bass frequencies as well. Both videos were recorded on my phone (I know, not the greatest audio quality) but I think the result reasonably reflects the differences I was hearing in the room.

I prefer the QSC tone wise, but the SD is a cool little box considering it weighs only 6.3 pounds. The QSC is just a bit heavier at 44.5 pounds.
Click to expand...

Cool comparison, how much you want for the GP3??😃😃😃
 
I wonder if you could EQ the SD to get close to the QSC. They both sound great to my ears.
 
OrganicZed said:
To be clear, the sound in the video is all Axe-FX III. The amp model was the Engl Savage channel 2.
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Oh definitely, I didn't mistake that.

I was just preparing to offer up a kidney for the GP3. Will that be enough or should I sell all of my gear and guitars too?
😂

Edit: I had a GP3 and moronically sold it somewhere back in 2008 or '09😖
 
mtb said:
I wonder if you could EQ the SD to get close to the QSC. They both sound great to my ears.
Click to expand...
Good question. I tried that with the 3 band EQ onboard the PS700. The bass control didn't hit the right frequency range to dial in the low thud that I was hearing from the QSC. I didn't venture beyond that, but it might be possible to get them sounding closer if I used an EQ on the Axe-FX. Perhaps I'll add that to the list of things to try if I make a follow up comparison video.
 
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Just to say it, it's weird to me that amplifier companies don't all get something as basic as raw frequency response pretty much right. If that simple, measurable characteristic isn't together, there isn't much hope for subtler things like transient response and musicality.
 
Dave Merrill said:
Just to say it, it's weird to me that amplifier companies don't all get something as basic as raw frequency response pretty much right. If that simple, measurable characteristic isn't together, there isn't much hope for subtler things like transient response and musicality.
Click to expand...

Assuming that the Seymour Duncan uses the ICE 700AS2 module, this is it's frequency response chart. That looks pretty flat in the 20 Hz - 20 kHz range but there's no data provided on how the amp behaves below 20 Hz.

1676864683296.png

The extra high end I was hearing form the SD PS700 may be explained by the drop in high frequency damping factor of these amps. If I understand this correctly, this means that the amp has a hard time controlling the excursion of the speaker cones in the high frequency ranges.

1676869790812.png

The QSC manual states that the rmx2450 has a frequency response of 20 Hz - 20 kHz (+0 / -1 dB) with a -3 dB fall off at 5 Hz and 50 kHz. It also has a low frequency filter that can be set at 50 Hz (with a 100 Hz boost), 30 Hz, and off. I'm fairly certain that I had it set with the LF filter off, but I'll have to check on that tomorrow. If it was engaged in the 50 Hz setting that may explain some of the observed difference.

Edit: The 30Hz filter was engaged, so that should have had no significant impact on the low end response.

1676864999760.png
 
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OrganicZed said:
Good question. I tried that with the 3 band EQ onboard the PS700. The bass control didn't hit the right frequency range to dial in the low thud that I was hearing from the QSC. I didn't venture beyond that, but it might be possible to get them sounding closer if I used an EQ on the Axe-FX. Perhaps I'll add that to the list of things to try if I make a follow up comparison video.
Click to expand...
Which Ohm input are you using on the cab? With the PS170 I noticed quite some difference between the 4ohm and 16ohm inputs (level normalised due to power differences), with the. 16 ohm input giving more rolled off highs and more pleasant bass frequencies. Also, I wonder if the output level on the PowerStage might make a difference if the ICEPower modules exhibit power dependent frequency response.
 
alethomantis said:
Also, I wonder if the output level on the PowerStage might make a difference if the ICEPower modules exhibit power dependent frequency response.
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I've been thinking more about this question a bit more. The two video clips were recorded with different output settings but the general differences in tonalities were the same. In both instances the QSC had a deeper voicing. If the frequency response observed was power dependent I would think I would have heard that from 100 dB to 110 dB.
 
^ with regard to the SD PS series.. the modules these are based upon are pretty dang flat in frequency response and sound neutral to my ears.. SD has put tone controls on these amps, and I would not assume that BMT at noon is a flat response.. fwiw I specifically avoided putting volume and tone controls in my recent power amp build as a) its unnecessary as Fractal has both right at the output, and b) its just another way to insert coloration and reduce the s/n ratio.

If the PS700 has an aux input (which should bypass tone controls) that may be a more valid comparison of the two units as line level amps
 
Mystic38 said:
^ with regard to the SD PS series.. the modules these are based upon are pretty dang flat in frequency response and sound neutral to my ears.. SD has put tone controls on these amps, and I would not assume that BMT at noon is a flat response.. fwiw I specifically avoided putting volume and tone controls in my recent power amp build as a) its unnecessary as Fractal has both right at the output, and b) its just another way to insert coloration and reduce the s/n ratio.

If the PS700 has an aux input (which should bypass tone controls) that may be a more valid comparison of the two units as line level amps
Click to expand...

That’s a fair point. Why would they label the controls 0 at noon and then have negative and positive values for the other settings if that wasn’t the flat position? Perhaps it would be so that it sounds more like a tube power amp when used with pedals as the only preamp circuits like they advertise.

Edit: There's no AUX input on the PS700. The PS200 does have one.
 
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