Using an A/V Receiver with a Squeezebox
A/V receivers from Sony, Panasonic, JVC, Denon, Yamaha, Pioneer, Marantz, etc. usually have a bad reputation among audiophiles. This is due to:
- low quality components, cheap construction, poor quality amplifiers
- multichannel amplification delivered using one solid-state component (causes overheating and distortion in all channels)
- amplifiers all driven off one power supply, thus current-limited and rarely delivering rated power
- video and other circuitry driven off the same power supply as the amplifer, potentially causing electrical noise
- gimmicky, artifical-sounding DSP effects like "Jazz", "Hall" etc.
- digital conversion of all analog streams, see below
However some receivers are better than others and some are designed to overcome these limitations. The better receivers will have discrete amplifiers, i.e. one per channel, to avoid overheating and distortion issues. Also the higher-end receivers will have better power supplies, better electrical isolation and higher-quality components. And there have been some very good DSP programs developed like Dolby Pro-Logic II.
Analog or Digital?
If you are new to this subject, see here.
Since you have this choice with a Squeezebox, you would think that using analog, you're using the Squeezebox DAC, and using digital, you're using the receiver's DAC. This is not usually the case.
The heart of an A/V receiver is the DSP, digital signal processor. It is used for tone control, speaker level balance, bass management and DSP effects like "Jazz", "Hall", even "Stereo" and decoders like Dolby Pro-Logic II and DTS:Neo 6. It can only work with digital streams, so any analog streams must be converted to digital using the receiver's ADC, analog-to-digital converter. After the DSP, the signal is then sent to the DAC like any other digital signal.
This extra conversion step will alter the sound. It can make it warmer (reduce treble) but may make it so warm as to be muffled in comparison to a digital signal which is sent directly to the DSP.
However, since many receivers are too bright (have too much treble) anyway, this effect may be more pleasing to you, so it's best to experiment and see what you like best.
Most receivers have a "direct" or "bypass" mode which is supposed to send the signal on to the amplifiers unaltered. However you will lose things you may want like bass management, speaker balance and of course any surround processing.
Alternatives and Improvements
Audiophile preamps generally do not have DSPs and pass the analog signal straight on to the amplifier. Also some higher-end A/V preamp/processors (pre/pros) like the Bryston SP2 have a true analog bypass.
Some receivers have preout connections. These are internally connected to the receiver's preamp section before the analog signal is sent to the amplifiers. You can connect a separate amplifier to these connections. Using a separate amplifier can give you several advantages:
- a separate amplifier will usually be of higher quality than the reveiver's internal amplifiers
- it has its own, dedicated power supply, often as large or larger than the receiver's power supply
- it has more power, even if it's rated the same as the receiver's internal amplifiers since it has its own dedicated power supply that's used for nothing else
- the power will be cleaner because it's not connected to video or display circuitry
- the receiver's power supply will be less stressed - more power will be available for the remaining receiver-powered channels and it will run cooler. Note this "extra power" is not equivalent to the power rating of the offloaded channels, for example, if you have a 5 X 100 W receiver and use a separate amplifier for the L & R channels, you will not have an extra 200 W available for the remaining channels. However the power supply will be able to deliver somewhat more power to the remaining channels before distortion and thermal shutdown.
Amplifiers do sound different, so the drawback you may experience when using a separate amplifier with some channels still powered by the receiver is that the channels sound different and the sound may not blend well. However, even when processed using a surround mode like Dolby Pro-Logic II, most music is concentrated in the L & R channels. There's some signal that gets sent to the centre channel and very little that gets sent to the remaining surround channels. So when listening to 2-channel music even in Dolby Pro-Logic II mode, you will experience most of the benefit by using a separate 2-channel amplifier for the L & R channels. You may experience further benefits by using a 3-channel amplifier for L, C and R (or a 2-channel amplifier for L & R and a mono amplifier, also known as a monoblock, for the centre channel). Using a 5- or 7-channel amplifier for complete offloading of all amplification is ideal but may have limited benefit since the surround channels deliver so little sound when playing back music.