Class D amps lack uumph?

[LewisK1975]

You're right JT. When you come across the DB's, you know. Right now I think my rig is the DB's, but I might be on a festival show in the coming weeks and have to use an SVT and an 810 and then I might decide that's the DB's and be trading my rig in.

It's all subjective, and people will have their own reasons for their preference - that's all I was really trying to say.

[Dood]

I'd like to see some real world testing similar to the reviews in BassGear magazine. Not just to find out which amps can deliver high peaks of current but comparing amplifiers to see which can deliver prolonged current output in the important bass frequencies. I'm thinking that sustaining synth bass notes would drain the power reserves a bit? What amplifiers on the market could deal with and deliver sonic girth throughout the evening.

Just a question really, but one that interests me greatly.

[Iain]

[quote name='dood' timestamp='1437763219' post='2828933']Just a question really, but one that interests me greatly.[/quote]

A 'real world' test where the sound coming out of the cab is measured with different heads is the only way to answer the question but it'll still come down to testing the manufacturer's execution (as Alex pointed out) rather than a definitive A/B > D.

My suspicion is that you get what you pay for at the limits of performance on all classes of amp. A really cheap amp must have made compromises in components assuming a relatively competitive market.

If you're running a cheap '500W' class D at '100W' then you'd expect it to have no issues laying down long low notes, cranked up to just below clipping and I'd expect/hope the more pricey unit delivers.

Question on the A/B vs D debate is what would one expect of an A/B run at it's limits for a long time and would it end up in a puff of smoke rather than nasty clipping and thermal cut-off?

I had an A/B Ampeg (PF-500) that used to cut off in practice sessions after about an hour on a warm day. Never had that issue runing longer and harder with the class D Markbass but it proves nothing really!

Edited July 25, 2015 by Iain

[Roland Rock]

[quote name='Iain' timestamp='1437818052' post='2829235']


A 'real world' test where the sound coming out of the cab is measured with different heads is the only way to answer the question but it'll still come down to testing the manufacturer's execution (as Alex pointed out) rather than a definitive A/B > D.

My suspicion is that you get what you pay for at the limits of performance on all classes of amp. A really cheap amp must have made compromises in components assuming a relatively competitive market.

If you're running a cheap '500W' class D at '100W' then you'd expect it to have no issues laying down long low notes, cranked up to just below clipping and I'd expect/hope the more pricey unit delivers.

Question on the A/B vs D debate is what would one expect of an A/B run at it's limits for a long time and would it end up in a puff of smoke rather than nasty clipping and thermal cut-off?

I had an A/B Ampeg (PF-500) that used to cut off in practice sessions after about an hour on a warm day. Never had that issue runing longer and harder with the class D Markbass but it proves nothing really!
[/quote]

Isn't the PF500 class D?
http://www.ampeg.com/products/portaflex/pf-500/

[Iain]

[quote name='Roland Rock' timestamp='1437819083' post='2829251']
Isn't the PF500 class D?
[url="http://www.ampeg.com/products/portaflex/pf-500/"]http://www.ampeg.com...rtaflex/pf-500/[/url]
[/quote]

Ah, well spotted - doesn't explain it being a heavy brick which is where my confusion comes from! Unimpressive amp when pushed though - definitely lacked oomph that my Markbass BB has in spades.

[Roland Rock]

[quote name='Iain' timestamp='1437819335' post='2829255']


Ah, well spotted - doesn't explain it being a heavy brick which is where my confusion comes from! Unimpressive amp when pushed though - definitely lacked oomph that my Markbass BB has in spades.
[/quote]

Which is an even better illustration to show that it's not the type of amp, but the design that matters

[JTUK]

The Ampeg PF breaks up when pushed which is the whole point of it, IMO.
That IS Ampeg.

[Iain]

[quote name='JTUK' timestamp='1437820071' post='2829266']
The Ampeg PF breaks up when pushed which is the whole point of it, IMO.
That IS Ampeg.
[/quote]

Nothing to do with breaking up and you won't get the classic Ampeg sound from clipping in tbe D power stage. The MOSFET pre-amp maybe. That wasn't the issue with it though - as I said it didn't do 'loud' and went into cut-off when asked to work hard...

Certainly seemed to lack bottom end too and putting the Big Bang through the 115 PF cab I still have backs that up.

[BanditSid]

[quote name='alexclaber' timestamp='1437586487' post='2827345']


I don't think it's helpful to claim that class D amps are digital when they're not, they're just another analogue approach, albeit a far more efficient one. Get two equally well implemented amps of equal power, one class AB and one class D and run them so they never clip and you won't be able to hear a difference.

The sonic differences arise in how the amps clip or if one has deficiencies in its design or implementation.
[/quote]

Alex made some very valid points that were missed I think. A power amplifier has one very simple job, it transfers the stored power in the power supply reservoir to the loudspeakers, this is simplistic but is it's basic function. Whatever amplifier topology you use, if it's done properly it should give the same results - but it will waste more power doing it as you head from class D through class AB to class A. Bass amplifiers are more demanding than any other application since they are mainly passing large low frequency signals that require large currents for long periods, placing a huge demand on the power supply which is where the problem will often lie.

I've designed and built lots of amplifiers using both valves and transistors and while there are subtle differences in the sound, the biggest influence is the power supply, especially for bass which needs to have sufficient storage capacity to sustain a long bass note without a voltage dip. Switchmode power supplies are extremely common now and should be the perfect solution since they can react to supply demands very quickly, but only if they are designed to do so in a bass amp deployment. I gig a GK MB800 which is a great little amp but does have limitations. The amp uses IcePower amp/PSU modules and they are the amp's Achilles heel, since they are not specifically designed for bass use - the distortion level is extremely high as the power level rises and the PSU is designed for a general PA application. A typical bass note starts off at high level and low frequency, the GK amp then distorts this heavily and runs out of current in the PSU to sustain the note after the initial attack - the lack of uumph this post mentioned.

As Alex said the design and implementation are key to getting a good sound, a class D amp can be made to deliver the same power to a speaker as a class AB with the same levels of distortion and damping factor, resulting in no discernible difference audibly. The power supply is more important to a bass amp and is the area that most amps fall down in, if companies could address this they would have a winner. A lightweight class D amp could easily deliver all that a bass player could ask for, if the accountants allowed the design to be implemented properly.

[wateroftyne]

These techie explanations are great - they're really explaining what I've been hearing for a while now in the consumer bass end of the Class D market.

If someone (Alex?) can come up with a lightweight with a power supply that isn't lightweight (if you know what I mean), colour me interested.

[mcnach]

[quote name='wateroftyne' timestamp='1437858157' post='2829625']
These techie explanations are great - they're really explaining what I've been hearing for a while now in the consumer bass end of the Class D market.

If someone (Alex?) can come up with a lightweight with a power supply that isn't lightweight (if you know what I mean), colour me interested.
[/quote]

It sounds like it's doable just not cheap. It probably would not sell thousands of units rapidly, but there surely must be a market for it.

[obbm]

I happened across a review of the Phil Jones BG400 combo recently

[url="http://www.youtube.com/watch?v=5v_Ki3h9uKc"]http://www.youtube.com/watch?v=5v_Ki3h9uKc[/url]

It's basically a Compact 4 cab turned into a combo which happens to have a Class D power stage. The reviewer commented that PJB had gone to great lengths to beef up the power supply to give an improved performance over earlier PJB amps. The down side was that it was heavier than expected, so it looks like it can be done. Shame that it's not available over here yet.

[fretmeister]

[quote name='wateroftyne' timestamp='1437858157' post='2829625']
These techie explanations are great - they're really explaining what I've been hearing for a while now in the consumer bass end of the Class D market.

If someone (Alex?) can come up with a lightweight with a power supply that isn't lightweight (if you know what I mean), colour me interested.
[/quote]

Try the Demeter.

It's brilliant.

[JapanAxe]

[quote name='fretmeister' timestamp='1437912892' post='2829900']
Try the Demeter.

It's brilliant.
[/quote]

I concur.

[wateroftyne]

Yeah... I might just do that....

[JTUK]

The problem ...potentially... is that the Demeter is very clean. Great balance but very clean
so it may not suit all...
I'm not a believer in a clean sound then muddying it up with a pedal myself so it is
a question of does what you do, work with the amp...
I find in some ways it does so that is a plus technically, but it will also force me to
articulate differently.

That is besides whether it cuts it in the Class D heft 'issue'.

Personal opinion is that the TKS S112 cabs and the Demeter are a good match...and totally different
from the TH and S112's. So the cabs themselves aren't a one trick pony.

[fretmeister]

The Demeter certainly is very clean and it really allows the sound of the individual bass to come through - but you won't get 1960s tones out of it without a pedal

I love the clean piano tone it has - but I'm also a big pedal fan so it ticks all my boxes.

[CamdenRob]

[quote name='fretmeister' timestamp='1437989208' post='2830487']
The Demeter certainly is very clean and it really allows the sound of the individual bass to come through
[/quote]

[quote name='fretmeister' timestamp='1437989208' post='2830487']
I love the clean piano tone it has
[/quote]

The more people say things like this the more I want one

[bassmachine2112]

Hiho,just an observation-Last night I gigged with my Orange OBT 500 after the band summer holiday,it is a class D.There was no lack of uuuumph and it sounded great.
It,s in the design.A good sounding amp with uuuumph is always a good sounding amp wiith uuumph,it doesn,t really matter and I,ve been through some amount of amps and cabs in my time and I,m converted and a lot easier than putting a valve head on top of a 8x10 or trying to squeeze it in a car/awkward load ins.

[Conan]

[quote name='CamdenRob' timestamp='1437989500' post='2830492']
Me too!



The more people say things like this the more I want one
[/quote]

Edited July 27, 2015 by Conan

[wateroftyne]

Hmm... apparently the Demeter uses the same B&O module that's in many of the common class-D's: Tonehammer, Shuttle, Streamliner, etc. So it's probably not for me.

The new Mesa subway uses a next-generation module, so it might be... we'll see.

[fretmeister]

That's interesting. My Demeter has loads more welly than my Genz.

[vailbass]

[quote name='Bill Fitzmaurice' timestamp='1437257339' post='2824727']
Right. That doesn't mean that some Class D amps might not be anemic, but don't blame it on being Class D, blame it on poor design by the manufacturer. Powersoft wouldn't be where it is if there was something inherently deficient about Class D.
[/quote]
I disagree, the K10 running my dual 15" wedges sounds great, it's also nearly $10,000 for 2 channels! The Class D bass amps on the market are largely just plain 'cheap' and sound like it.

[grandad]

[quote name='JapanAxe' timestamp='1437592795' post='2827447']
The easiest way to visualise Class D is to think of it like a FM radio transmitter. Your audio signal is modulating a much higher frequency carrier. I realise I may have lost a lot of people already...

It seems to be widely accepted that a lot of Class D power amps are somewhat optimistically spec'd. The infamous [url="http://cdn-downloads.tcelectronic.com/media/914735/tc_electronic_bass_amp_power_rating___active_power_management.pdf"]TC active power management article[/url] is actually quite illuminating in this respect, in that it it gives a good example of a real world Class D solution, where the initial note attack is sacrificed in order to reproduce the rest of the note, in a way that sounds subjectively 'as loud as' a much more powerful amp. One person's 'loud' is another person's 'baked-in compression'.
[/quote]

Only just read this article. I understand the controversy now.

[wateroftyne]

[quote name='vailbass' timestamp='1450672122' post='2934733']
I disagree, the K10 running my dual 15" wedges sounds great, it's also nearly $10,000 for 2 channels! The Class D bass amps on the market are largely just plain 'cheap' and sound like it.
[/quote]

This is my take on it, too. Until the high-end stuff filters down to consumer level, it ain't for me.