| 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. |
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| 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. |
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| 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? |
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| 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. |
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| classd4sure |
| quote: | 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... |
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| 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. |
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| 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? |
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| 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. |
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| classd4sure |
| By "audio community" you mean what exactly? Stereophile, etc? Shame as Nuforce? |
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| LineSource |
| quote: | 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? |
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| Tim__x |
| Output impedance has little correlation with the ability to drive low impedance loads. |
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| BWRX |
| quote: | Originally posted by LineSource
So, How do we build a DiY digital amp with very low output impedance? |
Lots of feedback. |
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| classd4sure |
| They seem to make the claim of no feedback |
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| Tim__x |
Lot's of low ESR/ESL bypass caps, low Rdson MOSFETs, a low ESR output inductor with a high pole frequency.
Then apply lots of feedback. ;)
Of course if you use anything except screw terminal connected 00 gauge speaker cable you can give up on your 5 milliohm output impedance. |
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| classd4sure |
| quote: | Originally posted by Tim__x
Lot's of low ESR/ESL bypass caps, low Rdson MOSFETs, a low ESR output inductor with a high pole frequency.
Then apply lots of feedback. ;)
Of course if you use anything except screw terminal connected 00 gauge speaker cable you can give up on your 5 milliohm output impedance. |
OOOoook....... now how do you do it with no feedback (capacitor?), no capacitors, aaaand no transistors!!! lol
I'd bet almost anything that it's got someones module inside, IcePower, powerphysics.... who knows, but I just have the feeling it's not of their own making, or they'd be making more sense of it. |
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| BWRX |
| Maybe they use thyristors (aka SCRs) and some clever turn off method? |
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| fokker |
| quote: | Originally posted by fokker
yeah. At idle, they should output nothing and there is certainly switching losses. so you have zero efficiency. |
even if you don't have switching losses and everything else is perfect (no deadtime, no shot-through, no load, etc.), you will still have low efficiency at low output levels. Here is my thinking.
switching amps are conceptually a capacitor being connected to either the positive rail or the negative rail through an inductor at any point in time. When it is connected to the positive rail, the capacitor gets charged up, and energy is consumed in charging it up - the positive rail has current flowing out.
When it is connected to the negative rail, the capacitor gets discharged, and energy is consumed in discharging it: the negative rail has current flowing in.
so even in an ideal switching amp, you will continue to have those losses (which is in essence connecting the positive rail to the negative rail through the L/C filter indirectly). and your efficiency goes up with the output levels, consistently with the efficiency vs. output curves for smps. |
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| gl |
Being a Magnepan owner I follow what goes on at the AA planar forum too. AFAIK only one inmate has come forward with a recommendation on the Gilmore Raptor. That being said, he is a frequent and credible contributor and has dumped his OTL tube monblocks in favor of the digital amps!!!!!!!!!! This was enough to make me do some research.
I believe that virtually all of the digital amplifier "manufacturers" out there are simply packaging someones pre-built Class D modules. The modules are either the newer ones from B&O (Icepower) or Hypex (UCD) or the older Tripath stuff. The advertising copy from the "manufacturers" all bears eery similarities. For instance the amp primary power quoted is the 4 ohm spec. You have to go looking for the 8 ohm spec. Because there are so few module makers at the moment, the output power rating usually gives you the module type that's buried inside. In the case of the Raptor it appears to be one of the Icepower units.
You need to look at the specs on the OEM modules to get the whole story on the specs, especially the output impedance. These are available on the web.
I just looked at the Glacier Audio site and didn't see anything on the Raptor page about "no transistors" or "no capacitors". Please tell me where you saw this information.
Cheers,
Graeme |
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| classd4sure |
| quote: | | I just looked at the Glacier Audio site and didn't see anything on the Raptor page about "no transistors" or "no capacitors". Please tell me where you saw this information. |
I dont' see it there anymore either :rolleyes: |
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| classd4sure |
| quote: | Originally posted by 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? |
That's copy and paste off their website anyway, if you look now, I don't even see a Raptor 300D or a Raven 100D.
They've done a little editing I think. Sobered up obviously. |
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