cs1 distorting/cracking

[.Jon]

Hey guys, about a month ago i got a cs1 to finish off my polk speaker setup. After a couple weeks I noticed at somewhat high volumes, but not that high, it crackles and distorts in the midhigh range. Like in the 5th element, the ugly warrior guys voices crackle alot when i turn it a little past medium. but it is only in about that frequency range that it does it. Like in war of the world of the worlds, when it emerges, then makes that huge foghorn type noise, it does it really bad there, infact im thinking that could have caused it. I played it about 3 times in a row one day and it distorted and it seems after that it has been distorting in that frequency range. But the thing is, it says it can handle 125 watts, I know thats not the rms rating but this reciever is 100 watts a channel and i have never had the knob past 50%.

any ideas? thanks

[Kenneth Swauger]

Hello .Jon.
Thanks for participating in the Forum. I believe what you are hearing is distortion being produced by your receiver. With high level sources, such as CD players, DVD players and even tape decks, full rated power is reached, with most receivers, when you have the volume control (assuming it is the kind of volume control that starts at the 7:00 o'clock position and rotates to the 5:00 o'clock position) at the 12:00 o'clock position that it is producing all of the power it can. If you have any of the tone controls or "loudness" compensation activated, full rated power can happen at the 11:00 o'clock setting. The reason this can happen is that most amplifier sections of most receivers have an input sensitivity of around 1 to 1.5 Volts. This means that if a signal around 1 Volt is given to the amplifier it will produce whatever its rated power is.
Most high level devices can produce output Voltages in this range. So, you could connect your DVD player to the amplifier section of your receiver and produce full rated power. The receiver's volume control is actually a "turner-downer" it's reducing the Voltage coming from your DVD player and when it gets to the 12:00 o'clock position that's really "0" for the control, it is permitting the full Voltage, of the player, to go to the amplifier section of the receiver. Therefore you get full power at the 12:00 o'clock mark. This is why many receiver companies recommend not turning the volume control past the 12:00 o'clock setting.
When you hear any harshness or brittleness or anything that's sounds strained or distorted consider that an "early warning" sound. Reduce the volume (usually only one notch, in most cases) so that the sound is smooth, clear, some say "sweet". Keep in mind that you are also compressing the dynamic range when you play beyond what the receiver can do. Digital format music and movie soundtracks have very wide dynamic range. But, when the receiver/amplifier is being "clipped" or overdriven a major result is compression of dynamic range. Louder parts are being made quieter and less dynamic, more compressed. Lowering the volume will restore the dynamic capability that digital sound can have.
I hope this is useful information.
Ken

[.Jon]

Thank you very much, I understand everything. Thats probably the problem, but would it only do it on the center channel? I havent really heard anything bad on any other channel. But its prolly the reciever as it is cheap and old.

[Kenneth Swauger]

Hey .jon,
Sometimes receiver companies use fairly "humble" amplifiers for the center and surround positions. They can be what is called "STK" (because the part numbers begin with STK....) amplifiers, which are pre-packaged amplifier modules. These are compact and inexpensive and give the manufacturer a reasonable way to economize. But, they don't have much headroom, meaning they can be overdriven fairly easily. Its possible that's what is built into your unit. You'll sometimes hear manufacturers touting "discreet" components, meaning made from individual parts, instead of a pre-packaged module.
Ken

[.Jon]

really? thanks man. Even more reason to get a new recv. Youve been alot of help!

[miguel rios]

I have a comment on this. I have an AKAI AM-U202 amplifier that uses a STK-4152II chip. If you read the chip specifications it says 30W over 8 Ohms stereo amplifier with +/-27 volts dc. However, AKAI actually uses a +/-45 Volts source, which makes the amplifier to deliver around 75W on 8 Ohms. The amazing thing is that Sanyo says the maximun voltage should be less than 42 Volts!! So, in my view, that is a lot of headroom. I have had that amplifier working for 15 years, and now I'm using it to drive a 15" subwoofer with astonishing results (due to the high efficiency of the speaker).

Miguel

Hey .jon,
Sometimes receiver companies use fairly "humble" amplifiers for the center and surround positions. They can be what is called "STK" (because the part numbers begin with STK....) amplifiers, which are pre-packaged amplifier modules. These are compact and inexpensive and give the manufacturer a reasonable way to economize. But, they don't have much headroom, meaning they can be overdriven fairly easily. Its possible that's what is built into your unit. You'll sometimes hear manufacturers touting "discreet" components, meaning made from individual parts, instead of a pre-packaged module.
Ken

[Kenneth Swauger]

Hello Miguel,
Thanks for the comments, much appreciated. What are some of the characteristics of the amplifier combined with the woofer that you enjoy? Did you build the woofer yourself? What was the design?
Regards, Ken

[miguel rios]

Hi Ken:

Well, after some experiments, I ended building a sealed box of around 250 liters (yes that is a huge box the size of a dishwasher!!), where I put a 15" driver pointing to the ground (the box is raised from the ground through four 12 cm legs). The main thing here is that the speaker has a very good efficiency (92 dBr at 1 meter with 1 W) so the Akai is more than enough to make most of my windows (and some of my neighbors) to rattle a lot. The box is made from a good strong wood (2cm) and has internal parts to make it harder and less vibrating. The amazing thing is to discover how some very low frequency sounds, that are present in some records, at last appear and can be heard. Of course, movies like star wars shine better with all this power.

There are some good plans in the Adire Audio web page (though they use their own 12" driver).


Regards

Miguel

Hello Miguel,
Thanks for the comments, much appreciated. What are some of the characteristics of the amplifier combined with the woofer that you enjoy? Did you build the woofer yourself? What was the design?
Regards, Ken

[aaharvel]

n/a =(