This is a review and detailed measurements of the (vintage?) Sunfire Cinema Grand five channel power amp designed by Bob Carver. It is on kind loan from a member. In 1996 it cost US $2,375. This unit is from 1999 and has had its caps upgraded.
I can't say I am a fan of this look. The meter shows an obscure measurement of the "power supply joules." The dial never moves so it is useless.
Back panel shows some deviations from norm as well:
In addition to normal speaker terminals, the front channels also have "current output." This just means that there is a 1 ohm resistor in series with the output. This causes voltage/power loss that is inversely proportional to the impedance of the speaker. As such, it varies the frequency response of the speaker so can have different tonality.
There is balanced XLR input which is what I used for my testing.
This amplifier is the third iteration of Bob Carver. After leaving Phase Linear, he designed the "Magnetic Field" amplifier under the Carver name. That product varies the AC duty cycle as a way to change the incoming AC voltage and with it, the output DC. This lowers the losses in the output transistors since they don't have to operate for worst case (maximum power). See my review of Carver M-1.5t amplifier. Bob then left and started Sunfire and with it, came this amplifier design. Instead of crudely changing the AC duty cycle, this amplifier has a DC to DC converter which tracks the incoming music. The higher the input level, the more it will increase its output voltage, thereby keeping the output transistors in their optimal voltage level. Result again is very high efficiency compared to normal class AB design. Let's measure it to see how well it works.
BTW, there are two versions of this: one at 200 watts and one at 400 watts. Maybe I am going blind but I could not see any designation of such on the unit.
Carver Cinema Grand Amplifier Measurements
As with the M-15.t, I noticed a lot of noise before I fed the unit a signal so let's look at that:
We see that the dc to dc converter is pass through a lot of AC noise and harmonics. This impacts the performance of the unit:
While second harmonic distortion dominates at -72 dB, the mains noise is not far behind, causing SINAD (relative sum of noise+distortion) to drop further to just 67 dB. This is ranks pretty close to the bottom of all the amplifiers tested:
SNR is not good as a result of that noise:
Multitone at 5 watts suffers from both power supply spikes and high intermodulation distortion:
Crosstalk is surprisingly poor:
There seems to be inductive leakage at frequencies below 5 kHz which I am guessing is bleed through the shared power DC to DC converter.
Oddest thing was the frequency response:
There is some verbiage from Bob Carver about "voicing" the amplifier. Perhaps this is intentional but then why is one channel different than the other?
Claim to fame here is high power capability so let's see if it delivers on that:
It does indeed. At the expense of noise and distortion but still, a 37 pound amplifier of the time, with 5 channels no less, would be in no position to produce such a power.
The new DC to DC converter is regulated so no headroom power:
There is healthy power at 8 ohm as well:
I had to lower the input level substantially to get the amp to run the frequency dependence as it would pull back severely at higher frequencies:
The lines are very high in vertical scale indicating high noise and distortion which we already know about. What we had not seen is the difficulty the amp has with high frequencies. This is likely due to the dc to dc converter not being able to track the voltage at higher frequencies. Fortunately music naturally has far lower level at higher frequencies so actual impact is low.
Finally, the amplifier is stable from power on:
Scale is heavily exaggerated with the one channel improving just 1 dB. And the other being stable from start.
Conclusions
Bob seems to have gotten the "high order bit" right in figuring out how to produce a high efficiency, high power amplifier. Alas, much of the talk is about fidelity and in that department, this is a poor showing. Mains noise gets through readily and distortion is quite high even by 1996 standards. From buying used point of view, the cool running environment of this amp means that it ages very well so the risks are lower. Then again that dc to dc converter brings a lot more complexity to the design.
Overall, the Carver Cinema Grand is not something I would recommend. But I can see people purchasing it as a lightweight, multichannel amplifier that delivers a lot of power. To the extent you can purchase it for a lot less than modern class D amps, it would be a decent buy.
P.S. no, I don't have any more carver amps to test.
Nor did I seek them out. They just happen to become available all around the same time.
I can't say I am a fan of this look. The meter shows an obscure measurement of the "power supply joules." The dial never moves so it is useless.
Back panel shows some deviations from norm as well:
In addition to normal speaker terminals, the front channels also have "current output." This just means that there is a 1 ohm resistor in series with the output. This causes voltage/power loss that is inversely proportional to the impedance of the speaker. As such, it varies the frequency response of the speaker so can have different tonality.
There is balanced XLR input which is what I used for my testing.
This amplifier is the third iteration of Bob Carver. After leaving Phase Linear, he designed the "Magnetic Field" amplifier under the Carver name. That product varies the AC duty cycle as a way to change the incoming AC voltage and with it, the output DC. This lowers the losses in the output transistors since they don't have to operate for worst case (maximum power). See my review of Carver M-1.5t amplifier. Bob then left and started Sunfire and with it, came this amplifier design. Instead of crudely changing the AC duty cycle, this amplifier has a DC to DC converter which tracks the incoming music. The higher the input level, the more it will increase its output voltage, thereby keeping the output transistors in their optimal voltage level. Result again is very high efficiency compared to normal class AB design. Let's measure it to see how well it works.
BTW, there are two versions of this: one at 200 watts and one at 400 watts. Maybe I am going blind but I could not see any designation of such on the unit.
Carver Cinema Grand Amplifier Measurements
As with the M-15.t, I noticed a lot of noise before I fed the unit a signal so let's look at that:
We see that the dc to dc converter is pass through a lot of AC noise and harmonics. This impacts the performance of the unit:
While second harmonic distortion dominates at -72 dB, the mains noise is not far behind, causing SINAD (relative sum of noise+distortion) to drop further to just 67 dB. This is ranks pretty close to the bottom of all the amplifiers tested:
SNR is not good as a result of that noise:
Multitone at 5 watts suffers from both power supply spikes and high intermodulation distortion:
Crosstalk is surprisingly poor:
There seems to be inductive leakage at frequencies below 5 kHz which I am guessing is bleed through the shared power DC to DC converter.
Oddest thing was the frequency response:
There is some verbiage from Bob Carver about "voicing" the amplifier. Perhaps this is intentional but then why is one channel different than the other?
Claim to fame here is high power capability so let's see if it delivers on that:
It does indeed. At the expense of noise and distortion but still, a 37 pound amplifier of the time, with 5 channels no less, would be in no position to produce such a power.
The new DC to DC converter is regulated so no headroom power:
There is healthy power at 8 ohm as well:
I had to lower the input level substantially to get the amp to run the frequency dependence as it would pull back severely at higher frequencies:
The lines are very high in vertical scale indicating high noise and distortion which we already know about. What we had not seen is the difficulty the amp has with high frequencies. This is likely due to the dc to dc converter not being able to track the voltage at higher frequencies. Fortunately music naturally has far lower level at higher frequencies so actual impact is low.
Finally, the amplifier is stable from power on:
Scale is heavily exaggerated with the one channel improving just 1 dB. And the other being stable from start.
Conclusions
Bob seems to have gotten the "high order bit" right in figuring out how to produce a high efficiency, high power amplifier. Alas, much of the talk is about fidelity and in that department, this is a poor showing. Mains noise gets through readily and distortion is quite high even by 1996 standards. From buying used point of view, the cool running environment of this amp means that it ages very well so the risks are lower. Then again that dc to dc converter brings a lot more complexity to the design.
Overall, the Carver Cinema Grand is not something I would recommend. But I can see people purchasing it as a lightweight, multichannel amplifier that delivers a lot of power. To the extent you can purchase it for a lot less than modern class D amps, it would be a decent buy.
P.S. no, I don't have any more carver amps to test.
Nor did I seek them out. They just happen to become available all around the same time.
