Integrating External Amp to AVR

[jels]

Hello Everyone–



I am newer to this space and have a couple of questions regarding amp decision and integration into the system that I would like to achieve. After reading the other threads, I was still a little uncertain about my application. Currently, I have a two channel integrated amp rated to 80 MW, but recently have completed a 5.1 system. My main usage is music at 80%, 15% movie, 5% gaming. The integrated amp worked well enough for my front speakers but have heard them with a more powerful amp and noticed a difference once given the headroom. With a 5 channel system, I am trying to find the best of both worlds of being able to have high quality music fidelity, with home theater option.

My idea is to purchase a Cinema 30, with a Buckeye NCx500 amp. Either 2 channel or 3 channel for the external amp – connected via RCA to XLR. My thought is that if I go with the 3 channel I can set the AVR to the preout setting and take advantage of lower distortion in the DAC. With a 2 channel amp, I would have to flip back and forth if I wanted to transition from music to tv watching. Not a big deal here. Regardless, with using the pre-out setting I look to have a great music experience as I’m bypassing the AVR amps, and a great theater experience by switching the AVR to play back the full the remaining surround channels and center speaker. I know I have to deal with the internal AVR dac, but based on the A1H measurements I still think it would be great.

I’m caught up on a couple of things, I don’t understand how this will all integrate together and if the external amp investment would be better for the 2 channel or 3 channel. I like the idea of buying a powerful amp, with low distortion that I can use in any future systems or speakers. At the power rating I’m concerned about protecting the speakers as they output more power than recommended.



My speaker setup:

L/R – 90 dB spl, recommended amplifier power 30W-300W, 8 Ohm (down to 3.1)

C – 89 dB spl, recommended amplifier power 30W-200W, 8 Ohm (down to 3.1)

SL/SR – 88 dB spl. recommended amplifier power 30W-120W, 8 Ohm (down to 3.7)

The higher end of the amplifier power is the maximum the speaker can handle per the manufacturer.



Buckeye Amp: 380 W @ 8 Ohm (forum search shows that its ~ 32W continuous), Class D

Gain settings when using our Buckeye gain stage:

4 ohm - 24.2dB/3.3Vrms (High), 19.2dB/5.8Vrms (Medium), 14.2dB/10.3Vrms (Low)

8 ohm - 24.2dB/3.4Vrms (High), 19.2dB/6.0Vrms (Medium), 14.2dB/10.8Vrms (Low)

Gain setting when using the Hypex gain stage:

4 ohm - 26.8dB/2.4Vrms

8 ohm - 26.8dB/2.5Vrms



Cinema 30: 140 W into 2 Channels, Class AB



Looking at the Cinema 40 measurements the pre-outs clipped at 3.6V when set to 90 in volume and measured at ~2V when set at 82.5.

Let’s assume that the Buckeye amp is configured with the Hypex gain stage (for AVR)



For a 2 or 3 channel external amp running in 2.1 setup:

Since the AVR can output up to 3.6Vrms, which is greater than Buckeye’s 2.5Vrms this tells me that I can maximize the power of external amp. However, If I turn the AVR up too high, besides the deafinng sound preventing me from doing so, the AVR would clip the external amp correct?

For me not to clip the buckeye amp, I’d have to not go past -3.17 dB of full scale (so 87 since 3.6V was at 90 per Cinema 40 measurment?). This is at 325W. So to keep the amp within 300W, that is another loss of -0.35 dB so the AVR can’t go passed -4dB, or 96 else my speakers and amp would be damaged. I’m not sure if this is correct, but if it is – can I place a limiter on the AVR, or do I just turn the knob down on the Buckeye Amp slightly from the max to avoid the wattage, but that doesn’t solve the clipping problem. I’m not worried about myself, but inevitably a family member will just want to turn it up without knowing and would like to prevent it getting past the point of damage.



For a 3 Channel external amp running in 5.1:

The AVR outputs 3.6Vrms without clipping. This is way past the external amp rating. Difference between 3.6Vrms, and 2.5Vrms is the -3.17db listed above. Though this is confusing to me because at 2.5Vrms (or 87 on avr?), the L/R will be outputting 325W, the C at 325W, and the SL/SR at 67.47W (-3.17db converted from 140W max.

SL/SR @ 3m,67.47W = 96.7 dB

C @ 3m,325W = 104.6dB

L/R @ 3m,325W = 105.6dB



At this setting, not paying attention to how loud this is, the Center Channel would exceed its rating, and I have 9db difference in sound. Is this linear such that I can correct for this in the AVR when running Room Correction? If I sensitize to the 200W C channel rating. Then 325W->200W is -2.11 dB, which is 1.96 Vrms input into the external. Which is around the measured input (8.25 level) from the Cinema 40 review. This would still have the same issue as above with regards to SPL difference and wattage. My head is telling me I’ll be “limited” to the AVR wattage at some point here



Overall, I’m confused on how to integrate the system together and whether I should go for a 2-channel external and connect the C channel to the AVR or a 3 channel external. I like the idea of L/C/R amplified with external for clean, low distortion power for any future setup, but don’t know if the C channel is worth it ($500 difference) versus connecting it to the avr. I’m also confused about how to level match given different amplifier ratings, if the difference in SPL is linear such that it can be corrected. Lastly, the external amplifier is powerful, and I don’t want to damage any components. Looking for help on how to prevent this and what not to ever go past. I understand that the SPL levels will be insanely high at maximum levels, but want to understand the system limitation and how to maximize the setup.

 

[AnalogSteph]

Buckeye Amp: 380 W @ 8 Ohm (forum search shows that its ~ 32W continuous), Class D

32 W? Measurements for a reference NCx500 show about 400 W into 4 ohms and a tad over 200 W into 8 ohms. (Note, do not trust speaker impedance paper specs unless you've seen the measurements.)

I'm not saying you are overthinking this but you probably are, while at the same time not paying attention to other issues. If gain varies too much between internal and extral power amps, you may have difficulty getting the relative levels adjusted. I would expect an internal power amp to be somewhere around 26-29.5 dB, so you may run into trouble when going all the way down to 14.2 dB. That's a setting most appropriate for high-sensitivity horn speakers. Given that your fronts also are a bit more sensitive, I would not expect any issues with either 26.8 or 24.2 dB.

Running front L/R on external power amps is likely to be the diminishing returns solution. Those are the channels that tend to be seeing the most action in the power-sapping bass department. And given what the Cinema 30 costs and its 11 (or 12) power amps, I would expect it to have a relatively stout power supply, so handling C/SL/SR should not prove too much of a hurdle. (Power supply sag is often a dominant concern in multi-channel output tests. In a basic model, 2x 140 W stereo can turn into 7x 25 W or less.)

There is no such thing as perfect protection. You can easily damage speakers well below rated power when attacking them with low bass at high levels. Just don't listen drunk and you should be fine. Party damage remains the leading cause of blown speakers worldwide.

 

[Will P]

Adding external amps is the way to go.

I wonder what features you find in Marantz Cinema 30 which are not available in lower priced AVRs?

You mentioned you have a 5.1 system.

Me personally I'd go with a 5.1 or 7.1 AVR with pre-outs and spend the rest of the budget on external amps (more power), better speakers (lower distortion), subwoofers.