Okay, so you have a preamp that you need to hook up to your AV receiver. Even though your AV receiver already has a built-in preamp, there are certain conditions where hooking up an external preamp to your AV receiver might be necessary. In particular, if you have a stereo signal with no volume control that you’re trying to play through your 3.x or higher surround sound system.
Hooking up a preamp to your AV receiver is pretty simple if your receiver has the capability:
- Find the AV receiver’s Home Theater (HT) Bypass or Direct In port.
- Plug the output of your preamp into the HT Bypass/Direct In input of your receiver.
- Turn the volume all the way down on your preamp before switching over to the HT Bypass/Direct In channel.
- Adjust your preamp’s volume to your liking.
For the most part, a preamp is unnecessary if you have an AV receiver. AV receivers already have built-in preamps that handle the volume, EQ, and gain, and many are not outfitted to accept an external preamp. There are, however, situations in which using an external preamp will be necessary.
What Is a Preamp?
A preamp takes a weak high impedance signal and converts it to a noise-tolerant low impedance signal sufficient for further processing. The preamplifier provides a degree of voltage gain to make it resistant to interference.
Preamplifiers condition electrical sound signals so they can be further processed and amplified by a power amplifier, which adds current gain, allowing it to drive loudspeakers.
Most audio-producing devices come equipped with a preamp from your AV receiver to guitar amplifiers to televisions. If you were to hook an external preamplifier directly into any of these you’d likely have to turn the volume on the device way down to compensate and might get some audio distortion due to the extra gain.
For this reason, if you want to hook up an external preamp to one of these devices, you will need to find a way to bypass the internal preamp. In actuality, preamps are designed to be paired with power amplifiers, not these other sorts of sound-amplifying devices.
However, there are some rare instances where an external preamp may not be your best option, but your only option.
Why Would I Need a Preamp?
Let’s say you’re an audiophile. Actually, if you’re reading an article about preamps, you probably are an audiophile. So let’s say you want your home theater system to double as your listening room.
The problem you’ll run into is that a home theater sound system is designed for movies and shows, not music. Because of this, the internal preamp of your AV receiver will not be calibrated for music quality.
For this reason, some high-end AV receivers have an HT Bypass or Direct In input that bypasses the AV receiver’s internal preamp and powers the signal directly as it is. There are a number of instances where a preamp might come into play here.
Reasons to Use an External Preamp
First, of AV receivers that have an HT Bypass or Direct In, most only have one, so if you are looking to hook up more than one audio source, you will need the multi-channel capability of a preamp.
Second, if your audio source doesn’t have an internal volume control, you will need a preamp, since the HT Bypass or Direct In powers the signal at full volume because part of bypassing the AV receiver’s internal preamp means bypassing its volume conditioning stage.
In either of these scenarios, you will need to get an external preamp to hook into your AV receiver. Although this is fairly straightforward, there are some precautions you will need to take to avoid blowing out your sound system or damaging your hearing.
Steps for Connecting a Preamp to a Receiver
Connecting a preamp to your AV receiver isn’t hard if your receiver has a HT Bypass or Direct In input. However, there are some very basic steps you will need to follow in setting up your system to avoid damaging either your speakers or your hearing.
1. Turn Everything Off
The first thing you’ll want to do is to turn all of your audio equipment off, especially your AV receiver. This doesn’t require you to unplug anything. You just want to make sure your speakers aren’t on when you’re setting things up.
You know that pop that speakers make when you plug something in while they’re on? That’s the sound of a jolt of voltage pushing your speaker cone out in a way it wasn’t designed for. Turn your equipment off every time you are plugging and unplugging.
2. Plug Your Audio Device(s) into Your Preamp
It is highly recommended that if you have the capability, you should plug any music playing devices through an external preamp designed for audio rather than video.
This will usually give you a better tone and gain for music than those designed for home theater systems. This will also ensure that you get the proper stereo mix music is recorded in, rather than trying to mash it onto a 3.x system or higher.
3. Plug Your Preamp into the Receiver
With all of your audio devices plugged into the preamp, plug the preamp’s Output or Phono Out directly into the AV receiver’s HT Bypass or Direct In.
In all likelihood, this will require a pair of RCA cables. Make sure you plug red to red and white to white to get the intended right-left separation.
4. Turn Your Preamp On and Lower the Volume All the Way Down
When you go through the HT Bypass or Direct In, you are bypassing all of your AV receiver’s internal volume controls. So whatever you send through the HT Bypass or Direct In will come out of your speakers at the full volume that goes into it.
Before you turn on your AV receiver, it is essential that you turn your preamp volume all the way down or risk damaging your speakers or your hearing.
5. Turn on the Receiver and Adjust the Preamp’s Volume
Now that you have the volume all the way down on the preamp, you are ready to power on your receiver. Play audio through the preamp that has the full range of sound you’d expect your average listening experience to be.
With the music playing, slowly adjust your preamp’s volume until you reach a comfortable listening level.
6. Adjust the Preamp’s Gain
If the sound is scratchy or thin, it may mean you need to adjust the preamp’s gain. Gain has a similar effect to volume, except that whereas volume controls the loudness of the output signal, gain strengthens the loudness of the input signal before being processed by the preamp.
To adjust the gain, turn your volume down slightly, and adjust your gain up slightly until it’s back at a comfortable listening level, and repeat until you get a sound you like.
Too much gain will make the sound distorted, so watch out. If you reach this point and still don’t like the sound, you may want to try adjusting the preamp’s EQ settings.
You’re All Set!
One last thing you may need to do is to individually adjust the output volume of your audio sources so that they play at the same level when you switch audio channels. Otherwise, you should be good to go!
Reasons You Can’t Connect a Preamp to a Receiver
As we’ve mentioned throughout this article, not every AV receiver has an HT Bypass or Direct In input. For the most part, it is only the high-end AV receivers that do.
It is important that you do not try to plug a preamp into a regular input because it will force the AV receiver’s preamp to deal with more voltage than it is designed to handle.
If you need to use a preamp but your AV receiver doesn’t let you bypass it, that doesn’t necessarily mean you should upgrade to a pricier AV receiver. Instead, you can pair your preamp with the device it was designed to deal with, a power amplifier.
A power amplifier is basically what you turn your AV receiver into when you use the HT Bypass or Direct In inputs, so if you’re looking to upgrade in order to accommodate a preamp, getting a power amp may be a more cost-effective way to go.