Class D amps lack uumph?

[Dan Dare]

Agree with you up to a point, Alex. But if the voltage drops for more than a few milliseconds, they don't like it. My Fohhn PA (which does not have an el cheapo/poorly executed s/m power supply) is not happy with poor quality generated power. At festivals, where you tend to share supply with the beer coolers, etc, etc, the voltage sags when they all kick in and can trigger the protection cut-out.

[Ancient Mariner]

[quote name='JTUK' timestamp='1437397217' post='2825589']
Was talking to an amp designer about this very thing yesterday... I relayed a few 'observations' from 'bass world' and he took on board a few
things abouts cab as they/he don't market them as yet.
But he was most interested in the class D thing and he obviously speaks to other amp makers and the conclusion was that marketing plays a huge
part in all this. That, in itself, doesn't make it bad but you get what the driver is. Whether that is right in the pursuit of sound is down to the individual
but his market is gtrs and he doesn't think they will be led by it. They all want lighter weight but not at the expense of their sound.

I wouldn't have to tell him, but gtrs in general are far more discerning and knowledgable and anal than your average bass player about sound.
In fact the bass player may well be lower down that chain than all the other muso's in the band... even than drummers..!!
and IME...I'd agree with that.
[/quote]

Thing is, we (guitarists) have already been through the SS vs valves issue, and as you say guitarists are generally very demanding in their requirements for tone where the amp is a major part of our sound shaping, rather than just wanting something loud enough to make eyes cross. But the class D design is much less likely to cause us problems (other than being SS, which is already a loser) because generally we don't need the crazy amounts of power to drive our sound like bass players, and most of us aren't fussed about pristine crystal cleans.

[JTUK]

Not that this guy will go down a NEO or class D route as his market is more the top end.
And those guys are ANAL. ( we did talk about those issues )
He knows he will be able to satisfy them with a drivey 12" combo or small separates as he doesn't need massive power
so his weight issues are also served by not having to have a heavy chassis and transformers.. This is just fortunate in its design
that he can build small but even if it wasn't the gtr would still then resort to an old Marshall and 212 or 412..

Their driver is tone first and foremost and they aren't going to divert from that. Some bass players HAVE to consider
weight as the primary concern altho just from memory from past threads on here...probably over 90%
of them say they'd have a valve fridge type set-up if someone else rigged it. So, that to me, points to
weight being the number one factor over ultimate tone which is not something many serious Gtrs would contemplate.

Me..I have both. a lightweight rig which is acceptable and a bit more, IMO,..but when the discerning gig comes out, so
does the full fat-full beans rig. And when I hire out, the same applies..!!

Edited July 22, 2015 by JTUK

[pmjos]

OK techy response for you guys.............

There definitely is a difference between Class D and other types of amps. A distinct technical difference, class D is [b]Digital [/b]and A A/B are analogue. But what does that actually mean?
Class D amps were developed out of Switch Mode Power Supplies and in fact a class D Amp (as in a rig amp) contains a Switch Mode Power Supply (SMPS) and a Class D (Switch Mode) amplifier - both are digital.

A class or A/B works by continuously increasing the 'amplitude' of the whole signal coming in from your bass. It takes what comes in, subject to tone filtration, and makes it bigger. Continuous signal in continuous signal out.

A Class D chops up the signal in into thousands of slices of equal size each with an amplitude ( a value in volts) and then the power amp reproduces each slice with a bigger amplitude (more volts/current). SO what I am saying is the amplification relates to the slices NOT a continuous signal .

Think of it like a modern TV which scans in a new image at 100Hz or 100 times a second. Looks pretty live to most people. Your eyes can't resolve the flicker because its too fast so you see an averaged out smooth image.

Now what is happening in a rig is that the digital signal goes through a low pass filter then to your speaker driver which just like your eye can't resolve at the sample frequency of the digital amp. The filter and speaker do the same job as your eyes with a TV, It produces a uniform tone (moving sound picture) which you hear. You are hearing averaged out slices of your original tone.

That isn't to say it sounds bad to our ears . A modern Class D will sound a little different but most of us won't hear it.

Class D is a compromise between lightness and efficiency and tone.This is the same as between Class A, Class A/B ad Class B. Class A is incredibly pure, low distortion and low noise but at 30W you could fry eggs on it and need massive power supplies, Class B is noisier but more efficient, class A/B a hybrid.

The smart cookies have put valve pre amps in before the Class D so you get tone Plus light power , Genz, Aggi

Its all a compromise - its always a compromise BUT digital is getting pretty good and its set to get better. Soon there won't be an argument to have - unless you have hearing like a bat of course.

[fretmeister]

My Demeter VTBP-M-800D (they really need to get some better names for their amps) is amazing and has huge heft.

But saying that - it depends what use the amp is going to put to - when playing with a load of woodwind instruments I don't want heft - I want clear articulation that is merely supportive to the other instruments.

Horses for courses.

[alexclaber]

[quote name='pmjos' timestamp='1437570139' post='2827130']
OK techy response for you guys.............

There definitely is a difference between Class D and other types of amps. A distinct technical difference, class D is [b]Digital [/b]and A A/B are analogue.[/quote]

Class D amps are not digital: http://www.hypex.nl/docs/papers/AES120_353BP.pdf

[Passinwind]

[quote name='alexclaber' timestamp='1437575024' post='2827200']
Class D amps are not digital: [url="http://www.hypex.nl/docs/papers/AES120_353BP.pdf"]http://www.hypex.nl/...ES120_353BP.pdf[/url]
[/quote]

They also do not have to use an SMPS and plenty do not.

There is also a pretty nice technical discussion [url="http://www.talkbass.com/threads/class-d-illustrated-lots-of-pics.1083366/"]here[/url] that may clear a few things up, or not. ;^}

Edited July 22, 2015 by Passinwind

[Guest bassman7755]

[quote name='pmjos' timestamp='1437570139' post='2827130']
A Class D chops up the signal in into thousands of slices of equal size each with an amplitude ( a value in volts) and then the power amp reproduces each slice with a bigger amplitude (more volts/current). SO what I am saying is the amplification relates to the slices NOT a continuous signal .
[/quote]

Actually no, thats not how it works. The input signal is converted into a stream of pulses of the same amplitude and different widths. Those pulses are then used to generate the same variable width pulses of a higher (also fixed) amplitude. The signal is essentially converted to an analogue (since there is no arbitrary precision limit on the pulse duration) time domain signal and then back again.

[url="http://www.audiodesignguide.com/ClassD/pwm1.gif"]http://www.audiodesi...ClassD/pwm1.gif[/url]

Edited July 22, 2015 by bassman7755

[pmjos]

I was trying to be helpful and didn't think explaining PWM would benefit most people. I still don't.

Your comment is correct but unintelligible. For reference I do not also fry eggs on my class A amplifiers or think that I need to become a Bat to hear the difference between Class D and other forms of amplifier.

[pmjos]

Oh and I know that Class D amps are not strictly digital.... its only the processing of the input to the mostly Mosfet driver stages.........

I really won't bother again....... the techy police will get me. I'll just slip off and burn my degree

[alexclaber]

[quote name='pmjos' timestamp='1437584116' post='2827314']
I was trying to be helpful and didn't think explaining PWM would benefit most people. I still don't.

Your comment is correct but unintelligible. For reference I do not also fry eggs on my class A amplifiers or think that I need to become a Bat to hear the difference between Class D and other forms of amplifier.
[/quote]

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.

[JTUK]

[quote name='pmjos' timestamp='1437584332' post='2827317']
Oh and I know that Class D amps are not strictly digital.... its only the processing of the input to the mostly Mosfet driver stages.........

I really won't bother again....... the techy police will get me. I'll just slip off and burn my degree
[/quote]

Wouldn't worry about it, tbh.... plenty of people on here get so hung up on a few things and will talk your hind legs off
and still have cloth ears, IMO. In a way, it can be quite funny the more you hang around and pick a few things up that
aren't generally posted.

[skychaserhigh]

Whatever class D is....I still don't like it !!

[JapanAxe]

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'.

[Guest bassman7755]

[quote name='pmjos' timestamp='1437584332' post='2827317']
Oh and I know that Class D amps are not strictly digital.... its only the processing of the input to the mostly Mosfet driver stages.........

I really won't bother again....... the techy police will get me. I'll just slip off and burn my degree
[/quote]

To be fair, with the exception of the first paragraph, the rest of your post was a very good explanation. I only took issue with the first paragraph because its going to be misleading for someone trying to learn how they work in a bit more detail especially with regard to your specific emphasis on the "digital" bit.

Edited July 23, 2015 by bassman7755

[Musicman20]

Re: guitarists and tubes - I've become much more involved with playing guitar now, and a small Fender tube combo with those pristine cleans is a wonderful thing. I have two low-ish wattage tube amps for guitar, and they do sound great. Guitarists have it much easier though, as a good quality 1x12 22W tube amp covers a lot of ground. Buy a nice overdrive pedal (like a Klon clone) and bam, you have some very interesting tones. However, the new Roland Blues Cube has NO tubes/valves whatsoever, and it sound absolutely stunning. Get it right, and guitarists wanting a solid, reliable, cheaper to run amp will buy it. It IS tough to get it right, more than bass IMO.

[Guest bassman7755]

[quote name='Musicman20' timestamp='1437641388' post='2827720']
Re: guitarists and tubes - I've become much more involved with playing guitar now, and a small Fender tube combo with those pristine cleans is a wonderful thing. I have two low-ish wattage tube amps for guitar, and they do sound great. Guitarists have it much easier though, as a good quality 1x12 22W tube amp covers a lot of ground. Buy a nice overdrive pedal (like a Klon clone) and bam, you have some very interesting tones. However, the new Roland Blues Cube has NO tubes/valves whatsoever, and it sound absolutely stunning. Get it right, and guitarists wanting a solid, reliable, cheaper to run amp will buy it. It IS tough to get it right, more than bass IMO.
[/quote]

To be fair to guitarists then have been generally well ahead of bass players in adopting modelling and other digital tech. The thing about lightweight gear is that there is no market for it until someone starts making the gear and the idea that there is an alternative out there gains some traction. It was the same in the bass world say 20 years ago - people just didnt think about because noone was aware of what was possible.

If someone built a guitar rig that was small, 15kg in weight and sounded reasonably close to a marshall JCM going through a 4x12 I reckon it would be a run away success.

[Jenny_Innie]

I have an RH750 and an RH450 - both of which are slagged off (by some) for not being true 750 and 450 watts amps. However, I can't imagine a scenario where you could run the 750 at full volume via my Barefaced Compact and Retro Two10 combination. No uumph is lacking there I can tell you. In fact, I just picked up another class D amp ...... an Ashdown MiBass 220. It's also a class D and I also can't quite run that at full chat with the speaker combo in a four piece guitar/drums/bass/keys band in a big pub.

I have uumph.

[Musicman20]

[quote name='Jenny_Innie' timestamp='1437648589' post='2827792']
I have an RH750 and an RH450 - both of which are slagged off (by some) for not being true 750 and 450 watts amps. However, I can't imagine a scenario where you could run the 750 at full volume via my Barefaced Compact and Retro Two10 combination. No uumph is lacking there I can tell you. In fact, I just picked up another class D amp ...... an Ashdown MiBass 220. It's also a class D and I also can't quite run that at full chat with the speaker combo in a four piece guitar/drums/bass/keys band in a big pub.

I have uumph.
[/quote]
I've had both those RH amps, and I still have the 750, and I still praise it despite the 'issues' that keep getting raised.

[mcnach]

[quote name='Musicman20' timestamp='1437641388' post='2827720']
Re: guitarists and tubes - I've become much more involved with playing guitar now, and a small Fender tube combo with those pristine cleans is a wonderful thing. I have two low-ish wattage tube amps for guitar, and they do sound great. Guitarists have it much easier though, as a good quality 1x12 22W tube amp covers a lot of ground. Buy a nice overdrive pedal (like a Klon clone) and bam, you have some very interesting tones. However, the new Roland Blues Cube has NO tubes/valves whatsoever, and it sound absolutely stunning. Get it right, and guitarists wanting a solid, reliable, cheaper to run amp will buy it. It IS tough to get it right, more than bass IMO.
[/quote]

While I really love the tone (specially clean!) of a few nice and relatively small valve amps, and I thought that it was in the valve domain where I'd find "guitar peace", I've recently made a great discovery.

We have some new equipment in the rehearsal studios we normally use, and there's this little Fender amp in there. I did not pay attention at first, but after a few weeks I noticed that whichever of our guitarists was using it sounded fantastic. IN particular, a stratocaster through it with a nearly clean sound was just beautiful. I'm not saying it was the best sound ever, and maybe on its own it might not be amazing... but in the band context it was just delicious. I noticed it. Each guitarist noticed it. We didn't notice everybody else noticed it until one made a comment and we all jumped in "yeah! I was thinking that too!!!".

As a result, two of the three guitarists are ditching their bigger amps and getting one of those Fenders. Guitarist number 1 already found one.

The amp? A Fender 112 deluxe. Solid State. Not a valve in sight.

£70 on eBay, 10kg. Loud enough for any of our gigs.
Lucky gits. I hate them! :-p

I'm after one too now.

[LewisK1975]

These sort of threads (whilst sometimes interesting to read for the occasional pearls of wisdom/knowledge) are farcical really.

We all have things we like and things we don't like. What a dreadfully boring world it would be if we all liked/disliked the same thing.

And for anyone wondering my rig is all lightweight, PUMA500 and 2 Barefaced supercompacts. I personally am very happy with my setup - someone else might think it sounds rubbish. That's fine, it's ME who has to be happy with MY setup.

Opinions are like private parts, everyone has them but when you start waving them in people's faces people don't generally like it!!

Rant over!

[wateroftyne]

[quote name='LewisK1975' timestamp='1437652687' post='2827858']
These sort of threads (whilst sometimes interesting to read for the occasional pearls of wisdom/knowledge) are farcical really.

We all have things we like and things we don't like. What a dreadfully boring world it would be if we all liked/disliked the same thing.

And for anyone wondering my rig is all lightweight, PUMA500 and 2 Barefaced supercompacts. I personally am very happy with my setup - someone else might think it sounds rubbish. That's fine, it's ME who has to be happy with MY setup.

Opinions are like private parts, everyone has them but when you start waving them in people's faces people don't generally like it!!

Rant over!
[/quote]

I disagree. You like what you have - that's fine.

Some of us think they have - generally speaking - a common characteristic, so we're just having an interesting discussion about the merits of commonly available class-D bass amp technology.

[LewisK1975]

Point taken - but there are elements of the thread where people are comparing class-D with Valve amps, not with other class-D amps, which in my opinion (waving it around ) doesn't really get to a conclusion at all.

It's (kinda) like Vinyl vs. CD, that's really the point I was trying to make.

Perhaps the point of the thread wasn't to arrive at a definitive answer, which is fine. No offence was intended..

[Muzz]

A definitive answer? On here? Whooooooowweeeeeee....

[JTUK]

[quote name='LewisK1975' timestamp='1437654218' post='2827882']
Point taken - but[b] there are elements of the thread where people are comparing class-D with Valve amps, not with other class-D amps[/b], which in my opinion (waving it around ) doesn't really get to a conclusion at all.

It's (kinda) like Vinyl vs. CD, that's really the point I was trying to make.

Perhaps the point of the thread wasn't to arrive at a definitive answer, which is fine. No offence was intended..
[/quote]

And that is because if sound is your soul arbiter, those comparisons are relevent.
It is not about best lightweight, it is about best sound.

I don't know why people can't hear it..maybe they don't want to, maybe they can't ..or maybe it doesn't suit their argument
but I'd worry if they really truely were oblivious to it.
Having said that, not my problem..lets hope it doesn't become yours...not yours specifically, I mean the players.

Of course, some rigs wouldn't rescue some people and their version of sound, no matter what their composite.

When I was young, I used an old Selmer TnB... imagine what you would pay for that now..and a Marshall Super lead..and then Hiwatt...
and I made all but the Hiwatt sound average or less. Sound City ..?? Sound Sh**y more like..and that is what they were called.

Now, I'd make a decent fist out of anyhting IMO... but I wouldn't truely 'love' many of them.
But when you come across the DB's...that is when you know.. IME.

Another thing is...if you can't play, you are really open to pot luck because you don't know any different...

Edited July 23, 2015 by JTUK