"2-tier Class H" output circuitry.

[Toasted]

Any help chaps?

[essexbasscat]

Class H ?

[Dad3353]

Class H...

[url="http://fr.wikipedia.org/wiki/Classes_de_fonctionnement_d"]http://fr.wikipedia.org/wiki/Classes_de_fonctionnement_d'un_amplificateur_%C3%A9lectronique#Classe_H[/url]

...but what's te question..?

[Toasted]

Some of QSCs amps are listed with class H output circuitry. I've never heard of it. Class D has made me sceptical of switching amps. Anyone tried / got any sense to talk about Class H?

The best output section I ever tried was the class A Aguilar DB750.

[Dad3353]

Dunno, mate, I play acoustic drums, sorry...

Edited April 16, 2012 by Dad3353

[Bill Fitzmaurice]

It's not new technology, Carver had it 25 years ago. There are two power rails, one for low voltage/current draw one for high voltage/current draw. The result is higher efficiency than typical Class AB, not so high as Class D. Class A is so inefficient you can get double duty using it to heat your house.

[Mr. Foxen]

[quote name='Toasted' timestamp='1334606955' post='1618539']
The best output section I ever tried was the class A Aguilar DB750.
[/quote]

Sure the output is class A, rather than the preamp? That would be really seriously hot all the time.

[Toasted]

I'm probably talking out of my arse mr.foxen. Thanks bill :-).

[Davebassics]

Class B for me! Maybe Class A in the Winter.

[dan670844]

I used a QSC RMX 2450 power amp for a long time, many gigs a great amp, sound quality and clarity was great and it had a lot of reserve current so playing dynamics were great, It was class H, personally I didnt give a monkeys, it was selected on power and sound quality, it was no lighweight amp though, but I guess for the power rating at the bandwidth it could deliver it was quite light!

[Mr. Foxen]

[quote name='Davebassics' timestamp='1334694848' post='1619997']
Class B for me! Maybe Class A in the Winter.
[/quote]

Class AB for audio amps, class B has a glitch where the waveform crosses 0v, you need a little overlap where it operates in class A to sort it out, so with a class AB amp, if you play really quietly, its in class A, louder goes to B. In a vox AC30 the overlap is quite big, so they are sometimes called class A, but technically aren't. Oh, and the Peavey Windsor I think, has a thing they describe as sweeping between class A an B, but it is actually unbalancing the phase inverter to the crossover point isn't at 0v and you get the distortion from the glitch. Not sure how useful knowing that is, but I was trying to explain the Vox AC30 thing to someone.

[Phil Starr]

Bill's answer probably says enough but if you want a little more about amp classes written for musicians then have a look at this. I adapted it from an answer to an earlier thread in BC.
[url="http://www.ultimate-guitar.com/columns/the_guide_to/a_guide_to_amplifier_classes.html"]http://www.ultimate-guitar.com/columns/the_guide_to/a_guide_to_amplifier_classes.html[/url]

cheers

[[email protected]]

i had that same question. class g uses two voltage rails while class h changes the voltage in the rails. i could see class g being called two tier because of the two rails but i don't know why class h would be called that. and by the way, they are ab amps until they need the extra power. and no they don't have the distortion issues of class d. i've done homework and own class a class ab class d and class h amps. the only one i am not too happy with is the class d. i have powered pa speakers with ab for the mids and highs and class d for the bass. those sound good. 

[agedhorse]

3 hours ago, [email protected] said:

i had that same question. class g uses two voltage rails while class h changes the voltage in the rails. i could see class g being called two tier because of the two rails but i don't know why class h would be called that. and by the way, they are ab amps until they need the extra power. and no they don't have the distortion issues of class d. i've done homework and own class a class ab class d and class h amps. the only one i am not too happy with is the class d. i have powered pa speakers with ab for the mids and highs and class d for the bass. those sound good. 

Both class G and Class H have multiple rails (can be either 2 or 3 tiers), both operate as class B/AB until approaching the rails at which point either the lower rail hands off to the higher rail or the signal hands modulated the higher rail into the lower rail. They can in fact have terrible distortion issues if the rail handoff (called commutation) is not done well.  the terminology of class G and H are interchanged in definition depending on where in the world you are located. In the US, class H commutates the rails, class g commutates the signal tier.

Class D amps do not have the distortion issues that you claim, you may not be happy with your class d amps, but not for the reasons you state because the distortion numbers are very close between good class d and good class AB/G/H.

[agedhorse]

On 16/04/2012 at 03:08, Toasted said:

Any help chaps?

What exactly is the question?

[BassmanPaul]

On 17/04/2012 at 16:34, Davebassics said:

Class B for me! Maybe Class A in the Winter.

You wouldn't like the Crossover distortion from Class B.

Edited November 22, 2020 by BassmanPaul

[agedhorse]

Proper class B has almost no crossover distortion, but the challenge is to keep the bias conduction angle the same across the entire audio spectrum. At higher audio frequencies, sometimes additional bias is necessary to insure no crossover distortion which leads to more than enough bias at lower audio frequencies. This is an example of why often a single bias value is not adequate, and by biasing slightly into class AB at DC (and lower audio frequencies) to be sure that the operation at higher audio frequencies is adequate for at least class B operation.

[LukeFRC]

On 22/11/2020 at 18:22, agedhorse said:

What exactly is the question?

it was sometime last decade before the world went crazy 

[Chienmortbb]

11 hours ago, agedhorse said:

Proper class B has almost no crossover distortion, but the challenge is to keep the bias conduction angle the same across the entire audio spectrum. At higher audio frequencies, sometimes additional bias is necessary to insure no crossover distortion which leads to more than enough bias at lower audio frequencies. This is an example of why often a single bias value is not adequate, and by biasing slightly into class AB at DC (and lower audio frequencies) to be sure that the operation at higher audio frequencies is adequate for at least class B operation.

Spot on again @agedhorse I think the classification Class AB is very misleading, as it almost implies that the power stages of the amp are operating in Class A at some point.

[Chienmortbb]

On 22/11/2020 at 20:21, BassmanPaul said:

You wouldn't like the Crossover distortion from Class B.

Unless it were badly designed, you proabbly would not notice it on an instrument amp.

[agedhorse]

7 hours ago, Chienmortbb said:

Spot on again @agedhorse I think the classification Class AB is very misleading, as it almost implies that the power stages of the amp are operating in Class A at some point.

Kind of yes and no. Whenever the conduction angle of each side of the push-pull pair is greater than 180 degrees, as some low level of signal one half will be sourcing current while the other half will be sinking current throughout the full waveform, and technically that's class A. BUT, often the distortion can be worse because the handoff from the positive to negative half may not have the identical curve shape so the distortion can actually increase where these curves overlap and under this condition it's possible for class B (if the ends of the curves just meet) can have "better" (lower) distortion characteristics.

This is something that Doug Self did a lot of research on maybe 20-25 years ago. The challenge is that the bias point at 100Hz may be different than at 10kHz, therefore a happy medium must be arrived at, usually that ends up slightly over biased at low frequencies for adequate bias at higher frequencies. In practice though, this is of no consequence.