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Is this a class D amp?

gtirard

gtirard

Feb 22, 2020
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Paris, France
inred-music.com
#1
Saw this bass power amp:
Coda - Jad Freer Audio

And I wonder if it's a class D amp or not.

It says:
  • FULLY ANALOG transistor power amp that develops 350W @ 8Ohm / 700W @ 4Ohm / 1400W @ 2Ohm in just 3.3 Kg -> it seems it's not class D
  • Thanks to the high-performance proprietary switching power supply -> seems it is class D
  • The Coda is enriched by a “simple” class A solid-state preamp section -> not sure
Personally I have a class D amp and I love it, but that intrigues me. Seems to be written in order to make you believe it's not a class D but it has the power/weight ratio of a class D amp?
 
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#2
"Thanks to the high-performance proprietary switching power supply, massive dissipation and dynamic forced ventilation, the CODA is the lightest, most powerful and compact power amp in the world, despite being completely analogue; what results is a sonic presence never heard before, characterized by speed, impact and pressure, which emphasizes the definition of notes."

WOW! Great marketing right there. It's class D (switching power supply) and analogue, because that's what a class D amp is - analogue. Speed! impact! pressure! Maybe the guy writes for NASCAR.
 
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#3
Jaco who? said:
"Thanks to the high-performance proprietary switching power supply, massive dissipation and dynamic forced ventilation, the CODA is the lightest, most powerful and compact power amp in the world, despite being completely analogue; what results is a sonic presence never heard before, characterized by speed, impact and pressure, which emphasizes the definition of notes."

WOW! Great marketing right there. It's class D (switching power supply) and analogue, because that's what a class D amp is - analogue. Speed! impact! pressure! Maybe the guy writes for NASCAR.
Click to expand...

Thank you, it's exactly what I thought. I'm not tech savy, and like many I thought class D amps where "digital"
 
#4
Jaco who? said:
"Thanks to the high-performance proprietary switching power supply, massive dissipation and dynamic forced ventilation, the CODA is the lightest, most powerful and compact power amp in the world, despite being completely analogue; what results is a sonic presence never heard before, characterized by speed, impact and pressure, which emphasizes the definition of notes."

WOW! Great marketing right there. It's class D (switching power supply) and analogue, because that's what a class D amp is - analogue. Speed! impact! pressure! Maybe the guy writes for NASCAR.
Click to expand...

The term Digital is a bit of a misnomer. It's not unusual for people to call class D amps digital, but they are not digital...it's marketing BS. Since these terms are being used inartfully, there is really no telling what Coda actually means. But IMHO, FULLY ANALOG transistor power amp," suggests a class AB output section with a switching power supply.

FYI, a switching power supply does not determine whether an amp is Class D or not.

As an example, both the Epifani UL902C and UL502 were class D amps. The UL502 had a linear power supply and the UL902C had a switching (SMPS) power supply.

AFAIK most modern Class D amps will have a switching power supply though. However, you may find some Class AB amps with SMPS as well.
 
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#5
(Crud! Wasnex beat me to much of what I was just finishing typing out :cool:)

gtirard said:
Seems to be written in order to make you believe it's not a class D but it has the power/weight ratio of a class D amp?
Click to expand...

A correction: "switching power supply" does not, by itself, mean a Class D amp!
It is absolutely possible to use a switching power supply to power a Class AB amplifier -- the standard analog circuit topology that goes all the way back to vacuum tubes. However, this has been uncommon in the musical instrument amplification field, for technical reasons that I would rather leave to the analog engineers to explain.

So, could the designer have mated a Class AB power section to a switching supply? Yes. Heat dissipation would be a challenge, though, and I'm not sure one fan in the back (with no obvious outlet) could clear enough heat to reach the claimed 1400W output. Maybe the specs are BS, maybe the designer just called a Class D output section FULLY ANALOG!11!! There's no way to tell what the heck the guy actually put in the box without tearing one apart.

There are other questions raised by the hyperbolic ad copy. The site claims a switching power supply -- but the fact that the CODA runs only on 220V, and requires factory modification to run at 110V, is very odd, because that's usually only necessary with transformer-based linear power supplies. Most switching power supplies, including those on high-power bass amps, can cope with either 110V or 220V without modification.

gtirard said:
like many I thought class D amps where "digital"
Click to expand...

You might find this post informative.
 
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#6
All of my Markbass heads (bar one) are class AB with switch mode power supplies:-
20210413_152312.jpg
 
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#13
I hate this marketing BS "the CODA is the lightest, most powerful and compact power amp in the world".

700W@4Ohm for 3.3kg, means ~212 W/kg. An amp like the GSS Sumo provides 1000W@4Ohm, weights 2kg, so 500W/kg ; identical ratio for the Quilter BB800.
I know it does not have the same set of features, and watts are what they are, but still, that's a ~250% ratio against the supposedly "lightest, most powerful and compact power amp in the world", not even close.
 
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#16
At least the preamp is class A per the description:

"
The Coda is enriched by a “simple” class A solid-state preamp section, with an ultra-linear response, with its VOLUME, a double speaker output with speakon-combo connectors and a D.I. with transformer inspired by the most famous ones used in recording studios.

"
 
#17
A class D amp operates it’s output devices in “on” or “off” states - this minimizes dissipation in those devices, so there’s less heat to dissipate than a class a, ab, b, or c amp, which operates its devices in in between states.

People think of things that are on or off as being digital, but a class D amp is analog because the timing of when the output devices switch states is “unconstrained” - they can change states whenever it makes sense - the output switching TIMES are analog. Put through an output filter to smooth things out, and the output signal is smooth and continuous - analog.

Part of the confusion stems from the letter used. Class D was used because a, b, and c were taken. D was next in the alphabet. Though “d” means digital in many contexts, this context is different. D is just what came after c.
 
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