Any design info on the Gilmore Raptor Digital Amp?

[LineSource]

Any design information on the Gilmore Audio Raptor Digital Amp? The amp seems optimized for very low resistance speakers with a 0.005 ohm output impedance. Does the Raptor use TI digital chips with a special output? Any idea how to construct a 93% efficient amp with a 0.005 ohm output?

Specs for the Gilmore Audio Raptor Digital Amp
Intermodulation Distortion
CCIF: Less than or equal to .001% up to full-rated power, 4 & 8 ohms
SMPTE: less than or equal to .01% up to full-rated power, 4 & 8 ohms
TIM: less than or equal to .003% up to full-rated power, 4 & 8 ohms
Harmonic Distortion
THD + N: less than .05% up to full-rated power, 4 & 8 ohms
Output Power (per channel)
250 watts @ 4 ohms, 10 Hz – 20 kHz
125 watts @ 8 ohms, 10 Hz – 20 kHz
Output Impedance
5 mil-ohms @ 1 kHz
Frequency Response
-3dB @ 60 kHz, 8 ohms
-3dB @ 4 Hz, 8 ohms
+/- 0.3 dB, 20 - 20 kHz
Output Stage Efficiency
93% or greater up to full-rated power
Gain
27 dB in high gain position nominal
20 dB in low gain position nominal
Dynamic Range
112 dB A weighted
Notes
All measurements conducted with AES17 filter on the amplifier output.
All specifications are preliminary and are subject to change without notice
Intermodulation Distortion
CCIF: Less than or equal to .002% up to full rated power, 4 & 8 ohms
SMPTE: less than or equal to .02% up to full rated power, 4 & 8 ohms
TIM: less than or equal to .003% up to full rated power, 4 & 8 ohms
Harmonic Distortion * (see note, below)
THD + N: less than .1% up to full rated power, 4 & 8 ohms
Output Power
500 watts @ 4 ohms, 10 Hz – 20 kHz
250 watts @ 8 ohms, 10 Hz – 20 kHz
Output Impedance
5 mil-ohms @ 1 kHz
Frequency Response
-3dB @ 60 kHz, 8 ohms
-3dB @ 4 hZ, 8 ohms
+/- 0.3 dB, 20 - 20 kHz
Output Stage Efficiency
93% or greater up to full rated power
Gain
27 dB in high gain position nominal
20 dB in low gain position nominal
Dynamic Range
118 dB A weighted
Notes
* All measurements conducted with AES17 filter on the amplifier output.

[MOER]

How can the amplifier's efficiency be better than 93% at all power levels? This amp is a crock or someone is lying about the specs. Efficiency drops as output power drops.

[classd4sure]

Maybe it starts off at 97 and drops down down to 93.

If you want to call em on some BS though, I say we start here:

"Gilmore Audio Amps:

The Raptor 300D: 300 watt digital monoblocs with no transistors and no capacitors. The higest resolution digital engine. All analogue inputs. You have never heard anything like it. Black, sleek, powerful, efficient. Runs very cool. Available June 1, 2005. Made in the USA!

The Raven 100D: 100 watt digital stereo amp with no transistors and no capacitors. The younger brother of The Raptor with identical sonic performance -- just less watts. Available in the Fall. Made in the USA!"

No transistors???? No Caps?? No sale!

Can't really have a "digital" amp with analog inputs either can ya?

[fokker]

I bet you the efficiency drops close to 0% when the input signal is sufficiently close to 0v.

As to no transistors. well, they may have defined "transistors" differently from the rest of us.

The same may apply to their capacitor definition.

[classd4sure]

Originally posted by fokker
I bet you the efficiency drops close to 0% when the input signal is sufficiently close to 0v.

As to no transistors. well, they may have defined "transistors" differently from the rest of us.

The same may apply to their capacitor definition.

0% efficiency at idle? I don't follow you on that one.

Any company with their own definition of standard electronic parts isn't likely to be in the electronics business.

I've seen them state elsewhere "no coupling caps" which OK, but it doesn't allow you to turn around say no "no capacitors". Even a mosfet is still a transistor.. perhaps they're unaware. The 741 they use in the input stage..... still has transistors...

[fokker]

"0% efficiency at idle? I don't follow you on that one."

yeah. At idle, they should output nothing and there is certainly switching losses. so you have zero efficiency.

[LineSource]

Yep, the advertising is funky, but this Gilmore Raptor amp gets very good reviews from the audio community.

Can anyone sketch out a digital amp design with 0.005 ohm output impedance?

*Multiple parallel MosFets, each with separate L filter?
*New super low-R MosFet?

[BWRX]

Hey here's part of their business ethics statement:
"We will never lie to you. We will also try to tell you the whole truth, as we know it. We will not pretend that we know something when we don't."

So that means their specs must be true.

[classd4sure]

By "audio community" you mean what exactly? Stereophile, etc? Shame as Nuforce?

[LineSource]

Originally posted by classd4sure
By "audio community" you mean what exactly? Stereophile, etc? Shame as Nuforce?

The AudioAsylum Ribbon/Planar folks who need to drive high currents into 1 ohm speakers give the Gilmore amps good reviews. Several Apogee and Magnepan owners have favorably compared the Gilmore Raptor and to big Krells etc..

So, How do we build a DiY digital amp with very low output impedance?