Power Amps

sleepysurf · Dec 20, 2006

Just wondering what type of power amp(s) you are using in your systems?

FYI, Sunfire Amps are technically Class "G", but for practical purposes in this Poll, consider them Class D- Switching Amps.

Reverb2009 · Dec 20, 2006

Class D right now (SunFire), making the move to A/B soon (Pass Labs).

Joey_V · Dec 22, 2006

Well well... with the switch on the Plinius, I go between Class A or Class A/B bias. But, I voted Class A because that's where most of my critical listening lies.

aliveatfive · Dec 22, 2006

Tubes can run in different classes, also. Single-ended triodes are considered class A tube amplfication, while push-pull tubes almost always run in class AB. As you may or may not know, the difference in the sound of these amps is considerable.

JonFo · Dec 25, 2006

Class D - Sunfires = all 14 channels

The IB Sub amp is a Class AB SS Crown.

Peter Hogan · Dec 26, 2006

Zip3kx07 said:
Class D right now (SunFire), making the move to A/B soon (Pass Labs).

JonFo said:
Class D - Sunfires = all 14 channels

The IB Sub amp is a Class AB SS Crown.

Hi,
Actually Sunfire (and the earlier Carvers) are actually a modified class G, which is a special case of class AB. Class G is the same as AB for small signals, but they switch the voltage rails to the output devices for larger signals. This allows them to dissipate less wattage in the output transistors (and also allows more current as well, without exceeding the safe operating area [SOA] of the transistors).

The Carver and Sunfire designs use a 'tracking downconverter', which is Bob Carvers term for a switching power supply. This keeps the output voltage rails just a few volts above what the transistors need at that moment, reducing the wasted power still further (and upping the current capability as well).

You can read more here:
Sunfire Amplifier Whitepaper

Peter

Joey_V · Dec 26, 2006

Peter,

Thanks for the lesson.... love it man! That's what I like about this site, just perusing randomly, I learn without even trying!

Joey

sleepysurf · Dec 26, 2006

Thanks for the link to the "New & Improved" Sunfire "white paper." I hadn't seen this updated version. I wonder why Sunfire discontinued the pure two channel Sunfire 300 and Signature models. Seems NO OTHER design can offer that degree of current output at that price point. Is there some "hush-hush" downside that we are overlooking? Excessive distortion? Poor S/N ratio? Anything? Inquiring minds want to know!

I have a Belles 350A Reference on it's way for auditioning. Will be interesting to see if really outperforms my Sunfire Cinema Grand. Bob Carver might just get the last laugh (at least in my system).

sleepysurf · Dec 26, 2006

sleepysurf said:
Is there some "hush-hush" downside that we are overlooking? Excessive distortion? Poor S/N ratio? Anything? Inquiring minds want to know!

Well, Googling for answers, I found an interesting comment in a Sunfire thread on A'gon... "...any MOSFET amp will produce the same even-order distortion that tube amps produce..as opposed to the odd-order distortion produced by bi-polar transistors which sounds bad."

Since Sunfire uses bipolar output transistors, perhaps this is the "audible downside" to his design. Any EE types lurking who can comment?

FYI, the Belles amp uses MOSFET output transistors, so should be an interesting comparison.

JonFo · Dec 28, 2006

Peter Hogan said:
Hi,
Actually Sunfire (and the earlier Carvers) are actually a modified class G, which is a special case of class AB. Class G is the same as AB for small signals, but they switch the voltage rails to the output devices for larger signals. This allows them to dissipate less wattage in the output transistors (and also allows more current as well, without exceeding the safe operating area [SOA] of the transistors).

The Carver and Sunfire designs use a 'tracking downconverter', which is Bob Carvers term for a switching power supply. This keeps the output voltage rails just a few volts above what the transistors need at that moment, reducing the wasted power still further (and upping the current capability as well).

You can read more here:
Sunfire Amplifier Whitepaper

Peter

Thanks Pete. I was aware it's not a Class D, but for most purposes, the general public likes to think of it as a class-D since it uses the switching power supply. You are right, we should be more specific on this forum.

Carver's design, as usual, is unique and as most often from him, effective

However, I've not seen it consistently called a class G. As a pure G is not quite what the tracking downconverter does. Is there a review or article that you could reference that definitively describes the 'class' for a Sunfire?

BTW- Here is nice write up on the various amp topologies, doesn't quite cover Sunfires, but a good doc anyway:
http://www.qscaudio.com/support/library/papers/amptalk.pdf

sleepysurf · Dec 28, 2006

Gosh, when I created this poll, I didn't realize how little I knew about the various amp classes! I'm sure learning LOTS now! Thanks for all the educational links.

Unfortunately, no way I can find to edit the choices in the Poll, so I'll leave them as is, with an edited disclaimer re Sunfire.

sleepysurf · Jan 1, 2007

Continuing my online education about amps, I've discovered a whole series of archived "Maximum dB" columns written by Doug Blackburn of Soundstage. The index of articles can be found here, and includes a superb series of three articles from 1998 titled... "The Amplifier: What’s Inside?" Highly recommended as a tutorial for us neophytes!

http://www.soundstage.com/maxdb/maxdb.htm

One caveat, the article does include some "fringe" audiophile tweak suggestions, but the gist of the technical section is mainstream.

Peter Hogan · Jan 2, 2007

JonFo said:
Thanks Pete. I was aware it's not a Class D, but for most purposes, the general public likes to think of it as a class-D since it uses the switching power supply. You are right, we should be more specific on this forum.

Carver's design, as usual, is unique and as most often from him, effective

However, I've not seen it consistently called a class G. As a pure G is not quite what the tracking downconverter does. Is there a review or article that you could reference that definitively describes the 'class' for a Sunfire?

BTW- Here is nice write up on the various amp topologies, doesn't quite cover Sunfires, but a good doc anyway:
http://www.qscaudio.com/support/library/papers/amptalk.pdf

Hi,
Class G is a class AB with the exception that the output devices do not have a single fixed voltage supply. Classically, the voltage supply to the output transistors is stepped, i.e. it goes from one set voltage to another (and sometimes a third), say 30, 60 and 90 volts. At low signal levels, it is at 30 volts, then as the signal level increases it will switch to the next higher voltage so it has enough voltage to produce the output waveform without distortion.

Bob Carver's tracking downconverter is a high frequency switching supply that 'tracks' the voltage needed for the output transistors, and varies the supply voltage to the output transistors continuously (not in fixed steps), so that it is always just a few volts more than the transistors need. This allows the output transistors to dissipate very little power, since there is very little voltage across them (and why his amps always run cool). It also allows them to deliver their full allowable current at all times, without exceeding the safe operating area of the transistors.

I consider his amps a modified class G, since it is a class AB biased output, but with variable supply voltage to the output transistors. However it is a continuously variable voltage, instead of the stepped voltage used in the classical class G.

HTH,
Peter

Dreamer · Jan 18, 2007

I suppose I'd fall in to the "modified Class G" camp. I'm running a pair of Carver M-500t's in bridged mono mode to drive my original Sequels. Seems to work just fine--amps run cool, speakers sound great, everyone is happy (except, perhaps my neighbors...:rocker: )

--Richard C.

Kaboomnash · Nov 2, 2007

I know my Pass X-250 does Class A and A/B,,, but hey I can live with A/B in the polls.

twich54 · Nov 2, 2007

Kaboomnash said:
I know my Pass X-250 does Class A and A/B,,, but hey I can live with A/B in the polls.

It is actually a class "A/B" amp for only their XA series are true class "A". The class "AB" designation means initially for the first few watts or so (Pass actually biases their products further up the Class "A" ladder) the amps operates in a class "A" configuration and then transitions itself to Class "B" for the remainder of it's power band.

mcmd · Nov 2, 2007

Hi all,

I voted A/AB. My (vintage) Threshold S/500 operating guide explains it like this:

"Threshold S/Series Stasis amplifiers employ pure Class A operation in all signal portions of the amplifier except the power current sources in the bootstrap section of the output stage, where heavily biased AB operation is used."

I am a big vintage Threshold fan, owning 2 S/500's and a S/300.

Best regards,

Marc

cabinum · Jul 25, 2022

Does anyone have a copy of the Sunfire white paper or a link to one?

JonFo · Jul 25, 2022

cabinum said:
Does anyone have a copy of the Sunfire white paper or a link to one?

Sure: https://thecarversite.com/yetanotherforum/userfiles/Sunfire_Amplifier_Whitepaper.pdf

DanR · Jul 28, 2022

What a great post! I run a combination of 3 amps on the Odysseys I just got a couple of months ago. I modded the speakers to an active crossover for the 8” and 10” woofers. I have a completely overhauled less than a year ago Krell KSA100 MKII powering the panels, and 2 class A/B pro amps powering the woofers. A Behringer KM750 on the 8” woofers which are new as well and present a 4ohm load, a Crown XLi 800 powers the 10” woofers which are also new and present a 8ohm load. All 3 amps are matched in power output to their respective impedance loads to 200 watts each. I have an order in with ML on a new pair of panels that should be finished sometime in November. The Odysseys are 21 years old now and one of the panels is on the way out so it’s time to replace them. They sound fantastic still set up like this.

Power Amps

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