Does class D have the Heft of SS

[Mark Reccord]

I know what youre saying but there have been many a tech debate here stating that at a normal listening level there would be no difference.
Also, Im using one channel of the CA9 into one cab at smaller shows so its not like Im bridging the whole deal. I know that the Crest is a far more powerful amp but its not just the Crest that Im talkin about. Any ClassD head that ive played an actual show with has been lacking in the bottom end and punctuality compared to the SS amps that I've used. Its just something that I've always noticed.
Believe me, if the Class D sounded the same I'd have gone out and bought one to use instead of my rack.

Perhaps the CA9 isn't a great data point here as the people who designed it have said they intentionally tweaked the design so for better low end performance (i.e. it's not flat in the low end). Another thing that you need to be careful with is matching gains. It's quite possible the gain of the CA9 was different than that of the power amp module in the TH and that can also affect how it's perceived. I'm not trying to discount your experience at all, just saying that there are probably variables other than just power amp class at play even when you might think there aren't.

All tech talk aside, I'm a big proponent of people playing what works for them, whatever the reasons. That's why I still drag an old SVT to many of my gigs. Because no other amp I've tried does it for me like that one.

 

[Mark Reccord]

Just curious: have you ever tried a Class D lead sled?

I have. I had to build it to find one, though.

 

[Passinwind]

I have. I had to build it to find one, though.

The Crown K2 worked for me, except that two in a rack weighed ~125 lbs.

 

[aborgman]

I know what youre saying but there have been many a tech debate here stating that at a normal listening level there would be no difference.

At performance volumes, I'd have to disagree.

Say your performance level at the edge of the stage is ~100dB (which is far from ridiculously loud) and the stage is 10 feet deep (~3 meters) and you're using an Ampeg 410HLF (~98dB/1W/1M).

That means you need to be ~110dB at 1 meter. If you're slapping, or playing with some good transients - you quite possibly have 15dB peak to average ratio.

To hit those volumes with that peak to average ratio - we're talking about needing ~450W to avoid transients getting limited.

You want to push that up to 105dB at the edge of the stage - now you're talking 1400W to avoid transients getting limited.

Also, Im using one channel of the CA9 into one cab at smaller shows so its not like Im bridging the whole deal.

That is still 600W into 8ohms, and that is a conservative rating.

I know that the Crest is a far more powerful amp but its not just the Crest that Im talkin about. Any ClassD head that ive played an actual show with has been lacking in the bottom end and punctuality compared to the SS amps that I've used. Its just something that I've always noticed.
Believe me, if the Class D sounded the same I'd have gone out and bought one to use instead of my rack.

Have you compared that CA9 to a comparable class D poweramp?

That CA9 (if only using one side not bridged) is about the equivalent power wise of a Crown XLS2502 running a single side, or a Crown 1002 running bridged.

 

[Mark Reccord]

The Crown K2 worked for me, except that two in a rack weighed ~125 lbs.

Is the K2 class D? I thought it was some permutation of class B/H.

 

[MordBass]

Perhaps the CA9 isn't a great data point here as the people who designed it have said they intentionally tweaked the design so for better low end performance (i.e. it's not flat in the low end). Another thing that you need to be careful with is matching gains. It's quite possible the gain of the CA9 was different than that of the power amp module in the TH and that can also affect how it's perceived. I'm not trying to discount your experience at all, just saying that there are probably variables other than just power amp class at play even when you might think there aren't.

All tech talk aside, I'm a big proponent of people playing what works for them, whatever the reasons. That's why I still drag an old SVT to many of my gigs. Because no other amp I've tried does it for me like that one.

Very well put... its simply what does it for each of us. Im just hoping that I can keep dragging this heavy rack around long enough for somebody to make a lighter option that I wont feel is a compromise. Time will tell lol

 

[agedhorse]

Fair point. by SS I meant traditional lead sled amplifier.

Or is a lead sled amplifier (by traditional definition) a tube amp???

 

[agedhorse]

Is the K2 class D? I thought it was some permutation of class B/H.

It's a unique approach to class D, in that the bridge halves are interlaced which doubles the effective switching frequency. This was helpful at the time because device speeds were still pretty slow compared with today.

 

[Passinwind]

Is the K2 class D? I thought it was some permutation of class B/H.

The K1 and K2 are both Class D, with a big ass toroidal power supply. One of my old ones still runs subs in a local club, 15 years after I offed it in favor of a PLX2 1804 (also long gone now). I loved the sealed and convection cooled aspects of the K2 though, although if you stack them you need an empty rack space between amps.

 

[eyeballkid]

There are more than one. What have you checked out lately?

I tried the streamliner, shuttle, ampeg 7, mesa, fender. Been to performances with bands I'm familiar with playing some of those plus the TC.
I will admit, the markbass I heard was impressively good though.

 

[Passinwind]

Very well put... its simply what does it for each of us. Im just hoping that I can keep dragging this heavy rack around long enough for somebody to make a lighter option that I wont feel is a compromise. Time will tell lol

I feel that, although my situation is very different, as I am attempting to port back to upright bass. Preferably unamplified, no less. Talk about a ball and chain!

 

[MordBass]

I feel that, although my situation is very different, as I am attempting to port back to upright bass. Preferably unamplified, no less. Talk about a ball and chain!

Yea I cant even imagine that hahaha. I use a small foldable cart for my rack which helps a bunch... as long as I keep remembering not to do leg day at the gym before a show.... man that sucked.

 

[GreyBeard]

I know what youre saying but there have been many a tech debate here stating that at a normal listening level there would be no difference.
Also, Im using one channel of the CA9 into one cab at smaller shows so its not like Im bridging the whole deal. I know that the Crest is a far more powerful amp but its not just the Crest that Im talkin about. Any ClassD head that ive played an actual show with has been lacking in the bottom end and punctuality compared to the SS amps that I've used. Its just something that I've always noticed.
Believe me, if the Class D sounded the same I'd have gone out and bought one to use instead of my rack.

I wonder what the high pass is on a CA9 maybe 30hz. I bet the difference you hear is something with the HP filter on the CA9 and on the smaller class D amps. I used a QSC-PLX1202 for a while and you could set the HP to either 30 or 50hz. I could definitely feel a difference. I usually left it at 50 so as to not overwork my speakers.

 

[Passinwind]

Yea I cant even imagine that hahaha. I use a small foldable cart for my rack which helps a bunch... as long as I keep remembering not to do leg day at the gym before a show.... man that sucked.

Back when I was lugging a van load I would have to forgo windsurfing on gig days, and maybe the day after as well. But hey, you gotta suffer if you want to sing da blues.

 

[MordBass]

I wonder what the high pass is on a CA9 maybe 30hz. I bet the difference you hear is something with the HP filter on the CA9 and on the smaller class D amps. I used a QSC-PLX1202 for a while and you could set the HP to either 30 or 50hz. I could definitely feel a difference. I usually left it at 50 so as to not overwork my speakers.

Thats a fair idea. I wonder if the Class D amps tend to run the HPF differently due to limitations in the bottom end.

 

[dukeorock]

Betcha a dollar... if you took two identical amps, but disguised them to look different and added a 25lb weight inside one and did a shootout, the heavier amp would win every single time. Just a hunch

 

[Bob Lee (QSC)]

It's quite possible the gain of the CA9 was different than that of the power amp module in the TH

The CA Series amps were designed for DJs and semi-pro users, who tended to use upstream gear with lower output voltage capabilities than pro sound reinforcement companies used. So the CA Series amps had a lot of gain, and the gain was higher with the higher power models so they would all have an input "sensitivity" of about 0.775 V at full gain.

 

[BurningSkies]

So, I have a power amp sitting at home that's class D and 1600w RMS at 8ohms (1% THD). Who wants to bring their CA 9 over and see how they compare.

From experience, I've been running higher powered Class D amps in live full band high volume settings now for something like 8 years. I've shared my rig dozens of times with other players and done so in rooms across the northeast. As of yet, no one has ever said "Is this amp Class D" or "This amp doesn't slam".

 

[Bob Lee (QSC)]

I wonder what the high pass is on a CA9 maybe 30hz. I bet the difference you hear is something with the HP filter on the CA9 and on the smaller class D amps. I used a QSC-PLX1202 for a while and you could set the HP to either 30 or 50hz. I could definitely feel a difference. I usually left it at 50 so as to not overwork my speakers.

I don't recall the CA Series having a high-pass filter, other than the one built into the servo at about 2 or 3 Hz or thereabouts.

 

[Passinwind]

The CA Series amps were designed for DJs and semi-pro users, who tended to use upstream gear with lower output voltage capabilities than pro sound reinforcement companies used. So the CA Series amps had a lot of gain, and the gain was higher with the higher power models so they would all have an input "sensitivity" of about 0.775 V at full gain.

When I borrowed the QSC A/B/X comparator rig from you the gain matching exercise for a CA9 and my PLX 1804 was pretty goofy at first blush. I have to wonder how many people would arrive at those relative knob positions when attempting casual gain matching.