Carver's tracking downconverter - thoughts?


2001-02-19 10:38 pm
Has anyone looked at Bob Carver's
patent on the sunfire amplifier
(power supply) tracking downconverter?

The controversial designer has once
again come up with something off the wall - hehe

I haven't heard Sunfire amplifiers
so I can't comment, has anyone
researched this shtuff ?

Is it live or is it memorex (snake oil) ?
Hi thylantyr

I too am interested in the sunfire amplifier from Bob Carver.
I have listened to one of his amplifiers and while they are clean, they tend to have a clinical sound about them.

Having said that, from a technical point of view, I am very interested how he has achieved such high power with very low thermal loss.

So if any one comes up with a schematic of one of these amplifiers I would very much like to see it...

Anthony Holton

PS: thanks for the patent link


2001-02-19 10:38 pm
I could be wrong, but Bob Carver is a good marketeer (Is that a
word? ha ha). I think his amplifier topologies are generic,
his main focus is on power supply "black magic" to convince
consumers that he has more bang for the buck in terms
of real estate - hehe

The magnetic field power amp, nothing more than a
switching power supply with three? voltage per rail,
to minimize heat loss, thus making a smaller amplifier.
I'm pretty sure Hifonics used a similar method also 10-15 years
ago in their car amplifiers.

Now he has patented a method which allows rails
to follow input signal, minimizing the heat dissipation.
I saw an inside picture of the sunfire amp, the only
heat sink was the chassis, but there was a rats nets
of wiring and looked ugly.

Why go thru all the trouble to make a complex power supply?
To save money and space? If so, why doesn't pass on the cost savings to the consumers - haha......

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
Given the broad nature of the prior art and the verbosity
of the claims portion of the patent, I think we are probably
seeing a fairly narrow patent, in which the patentability
of the circuit hangs on smaller details.

This sort of approach is very common when the patent
office rejects broad claims; the applicant continues to
narrow the scope of the patent until it becomes
sufficiently technically unique.

Keep in mind too, that the legal part of this is only in
the formal single sentence claim, and given the imprecision
of the English language, you can have to fairly unrelated
inventions described in the same manner.
Schematics, descriptions, and accounts have been previously available at which is a patent search website. I have seen actual pages of the filed patent here which include some schematic detail. This website now requires a log-in and I am unsure if a fee is now associated with it. It almost looks like a normal PWM but instead of a constant Vref it is referenced to the Vds of the FETs and the changing audio signal.


2001-02-04 4:23 am
I am going to refer to a different patent to make it simpler to explain.
Load the images with your TIFF viewer and go to fig.5 on the third page.
The Sunfire subwoofer amp uses this idea with two extras: 1)the pass transistor for the high voltage tier runs switch mode, instead of linear as shown here, and 2)the level shift for the high voltage tier is referenced to the input, and there is an all pass delay network between the input and the amplifier. This gives the supply a little time to get the voltage in the right ballpark before the signal actually gets into the amp.
I've had a very brief listen to one of the Sunfire amps. Unfortunately, I was limited to poor radio reception, as I didn't bring a CD, and all the salespeople were busy with paying customers.... The store had just started carrying the Sunfire line when I when sub shopping, and I was steered clear from them by the salesman. I also had a brief listen to the original Sunfire Sub at college. Unfortunately the guy had it in his dorm room closet - I was thoroughly underwhelmed.

My understanding is that the Sunfire amplifiers are more or less a "typical" Class A topology with a fancy power supply that tracks the input (plus 6 volts). But it has been a while since I read the whitepaper(s), and I was unable to find them on any of Bob's web sites. I do remember a lot of fluff with little significant content.

Still, it is a novel idea, and many large Class A amps seem to be incorporating an "adaptive biasing" scheme as of late. And isn't this now a distinct amplifier class? Class H or something?

Mark Broker


2002-04-12 4:41 am
I have looked at Sunfire amplifiers but the price will hurt me severly.

Whats interesting with the Sunfire amplifiers is that it can handle two different loudspeakers per channel. One loudspeaker can be hooked up to the current output to hear close to vacuum sound and the subwoofer can be hooked to the voltage output for solid state sound.

There have been other previous post about sunfire amplifiers. Please search this Forum.
--Still, it is a novel idea

I think Bob Carvers ideas are brilliant,
but I don't think he does justice to his
own creations. I.E., hifonics amplifiers
use the same type of technology that
he patented in 1980? and those car
amplifiers were excellent. Then Carver
uses his own technology and makes
inferior products, ie the magnetic field
amplifiers and even his car amplifiers
were junk, I still have one in my closet
torn apart - garbage.

I'd like to see someone else take
his "tracking downconverter" concept
and apply it correctly -- >muhahaha
Thanks for the kind comment regarding the HiFonics amps.....

"hifonics amplifiers
use the same type of technology that
he patented in 1980? and those car
amplifiers were excellent. "

Just to set the record straight, the HiFonics varipower amplifiers used mostly a 3 tier rail switching scheme, common to all channels, outside the amp feedback loops. I assume you are referring to the Carver Cube and descendants, that used actual series output stages, with the rail "switching" being done inside each channel's feedback loop.

Hope that makes sense,
Lukas Louw, VP Eng for HiFonics 1991 to 1995
"you would need one for each rail though."

If you do a bridge amp you only need one.

Huh? If you have two supply rails (+ & - V) you need two pwm amps one for each rail. Or maybe you see something I don't?

He's probably talking about a single rail bridged amp.

Anyway, you only need one PWM amp to create tracking rails for a mono amp running on split rails. Take a floating +-5 volt supply, connect it's + and - to the AB amp collectors, and connect it's common to the output of the PWM amp.... You'd have to repeat this for each amplification channel. There are any number of variations on this theme. Just go to and you'll see umpteen patents that all amount to the same thing, covering the same variations.

tracking etc

Well maybe he is talking about a single rail bridge, but he didn't say. Bridging or not is irrelevant in this context, single supply is.

Yes, there are many variations. The floating supply is a good option. The reason I mentioned pwm amps is because they are available for a quick check-of-principle if anyone wanted to try it out.

Jan Didden
Hi all

A "bridge-type single voltage tracking downconverter plus linear output stage" amp is the BASH amplifier topology.
Currently I am not able to access their homepage but the last time I visited it, I felt that they were quite honest about their technology's abilities (wich is not self-evident, regarding the hype you can read on the web regarding switching amplifiers).


"A "bridge-type single voltage tracking downconverter plus linear output stage" amp is the BASH amplifier topology."

Yes, that is one of the more interesting ones, based on a patent by John French. If I remember correctly, they use a floating PWM switch, limiting the AB amp to bridged output topology....... It is also supposedly capable of full range operation, wheras the Carver tracking converter poops out at about 7KHz. I've not had the pleasure to put a recent Bash amp on the bench, but I have a friend who has, and the amps do not produce rated continious power. They apparently get rated power under peak conditions, and continious around 60% of rated....... I don't know if that is by philosophy, or sheer optimism....

I have tested the original Bash car amps way back in the early 90's, and they had no b*lls, mostly due to poorly regulated supplies.