I've been a fan of low cost matrix surround for several years now. Though I didn't need another decoder, when J&R Music World changed the price of the Dynaco QD-1 (Series II L) to $19.95, I just had to buy one and give it a try!

There's a lot to like (and dislike) about the QD-1. Allow me to explain. The Dynaco QD-1 Series II L decoder is pictured immediately below.

In their owner's manual, Dynaco refers to this unit as the "DYNACO Home Theater System". This little box can be configured as a three, four, or even five channel system. This decoder is of the passive-matrix variety. That is, it does not perform any active signal processing or channel steering.

I received my unit within two days of ordering it from J&R Music World ( www.jandr.com ). The construction quality is very good. The unit is approximately 2.5" (inches) high, 8" (inches) wide, and almost 7" (inches) deep. It weighs in at 5 pounds and has a very shiny front panel. Attached to the bottom of the unit are 4 rubber feet allowing easy and safe placement on top an existing component.

Features

Front panel controls

The Dynaco is quite simple to operate. The front panel contains three knobs. The left most knob is labelled as the "MODE" control and allows you to select one of three options.

The "Theater" mode is the normal mode of operation in which all connected speakers are utilized. The "Surround" mode shuts off the front left and right speakers. Only the surround speakers (and a center speaker if connected) are operational in this mode. Finally the "Stereo" mode turns on only the front left and right speakers. The center speaker and surround speakers are off in "Stereo" mode.

The center knob is the "GAIN" control. It controls the volume for the center and surround channels.

The center and surround channels are both affected simultaneously thru the GAIN control. There is no way to separately adjust the center channel volume with the QD-1 Series II L decoder.

The rightmost switch on the QD-1 is the "CONTROL" knob.

It has three settings. With the CONTROL knob set to "FLAT", the surround channels get a full frequency response signal. This is great for material not specifically encoded in Dolby Surround. However, Dolby Surround Sound decoders usually attenuate frequencies above 7 kHz. To provide a more accurate frequency balance for Dolby Surround material, a "Contour" setting is available which limits the surround channels frequency response to 7 kHz. (The "Contour" setting may also come in handy when listening to material that may have bit of noise in the surround channels.) Finally, there is a "Center OFF" setting which allows you to turn off the center channel only (should you have one connected).

Rear Panel Connections
Connecting the QD-1 to your (thru your) existing stereo system is quite easy. The right and left speaker outputs of your existing system are connected to the right and left amplifier inputs on the Dynaco.

The terminal connectors on the Dynaco can accept banana or spade lugs, solid pins, or just twisted wire. You can then attach your left and right front speakers to the appropriate outputs on the back of the unit.

Note also that the Dynaco provides output for a front center speaker. Dynaco considers the center speaker purely optional and then they only recommend it if your front speakers are more than 8 feet apart.

The rear of the unit also provides you with your right and left rear speaker outputs.

Dynaco recommends that the impedance of your rear speakers match that of your front speakers. (Indeed, I found the rear speaker impedance to be critical--more on this later.)

Inside Circuit Layout
The inside of the unit is neatly laid out. (Click on the image below if you wish a larger view.)

Note in the diagram above the presence of a half dozen 10 watt resistors as well as the "triple ganged" variable resistor. A wire wound coil and 50 volt 20 microfarad capacitor are also mounted on the internal circuit board. (Dynaco claims that with this circuit, your amplifier should never see less than 4 ohms for any speaker connection.) 

Performance
It took only a matter of a few minutes to reconfigure my home theater system to accommodate the QD-1. (Note: I do not have a center speaker so this review does not cover the Dynaco's front center channel.) Though the Dynaco was easy to set up, I was immediately disappointed with its performance. I simply could not get adequate volume from the rear surround speakers. Even with the Gain control in its maximum position, the rear channel volume was at least 3 decibels lower than what I would consider acceptable.

Now my front speakers are rated at 8 ohms. My rear speakers have an "8 to 16" ohm rating. As an experiment, I attached the rear speaker outputs to the front speakers and the front speaker outputs to the rear speakers. I wanted to find out if my speaker impedances were the cause of the very low rear channel output.

Making the switch did result in better rear channel volume. However it still was about 1 or 2 decibels below what I usually consider balanced for my system. Note: I primarily use my rear speakers for musical ambience enhancement. They are not played loudly at all.

Also, there was considerable "leakage" of the front center channel into the rear channels. In fact, after a bit more experimenting with the Dynaco QD-1 I realized that this unit does not feed a pure L-R channel to the rears at all. This unit is performing just like their early 4 channel matrix decoders. (Much like circuit #3 on my "Do It Yourself Surround Sound" page.) In other words, the Dynaco QD-1 Series II L decoder provides 1970's style 4 channel matrix decoding with the additional possibilty of attaching a front center speaker output if desired.

If this (4 channel matrix) decoding is what you're looking for than the Dynaco is a great bargain. However, I for one, am not a fan of this type of decoding. Why? Because it only offers about 3 decibels of channel separation which is very, very, minimal. I guess I'm now used to the front center channel being completely isolated from the rear channel. It wasn't long before I took the Dynaco out of my system and went back to using the internal (non-ProLogic) Dolby Surround decoder in my receiver. I much prefer the effect of a pure L-R channel in the rear speakers without any center channel sound coming thru the rears.

Summary
The Dynaco QD-1 Series II L provides 4 channel matrix decoding. If you're looking for the original matrix 4 channel experience, then the Dynaco is for you. However, this unit is being marketed as a low cost "Home Theater decoder". In this area, it fails to deliver the goods. I was very disappointed in the lack of rear channel volume as well as the considerable leakage of the front center channel to the rears.

Of course, we're talking about a decoder that now retails for only $19.95!   The performance of this doesn't seem so bad if you can get it at that price.

This unit is a bargain in parts alone! Do it yourselfers may wish to buy this unit, then cannibalize it for parts. It's extremely well built with quality components. However, it does not deliver the surround sound experience that most people are looking for.

If you have further questions or comments, feel free to send me email. My name is Chris and I can be reached at: ckantack@yahoo.com (Or click on the envelope icon below.)

This web page was last updated on: 01/25/20 12:04 PM Pacific Time.