Axiom Home Page Forums General Discussion Home Theater Question on amp to my Onkyo 805

I decided to try out two of these amps on my system:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=302-601

I connected one per M60. At low levels the M60 sound great, but once I start increasing the volume to levels that are loud, the M60 start sounding "scratchy" like some kind of distortion. Is this sound caused by the amps not able to handle the demand of the M60's or the M60's not able to handle the amp?? I also have the M60's at the THX recommended of 80hz...should I increase to 100 or so the M60's are also set to "small".

Much appreciated.

That's not a "pre-amp", it is a power amp.

I'm guessing that you're using the 805 as the pre-amp, and feeding the pre-out signal to the AudioSource amp.

Could be a connection issue.

I would not fault the M60's. I would not cross them over at 100Hz.

I'm skeptical that these amps would provide a meaningful improvement over the internal amps of the 805.

It looks to me you taken a step backwards in your amplification. Why would you replace the Onkyo amps which are rated at 130 watts per channel with budget amps rated at 50?

The onkyo was maxing out at 88 volume level and was not loud enough for my taste. I added these and it did increase the sound. Now I put the volume level at 70 and it is very loud except the scratchy sound that I mentioned. I have these bridged as the amps manual recommends per M60.

I double checked the connections and I have the amps connected as recommended by the Onkyo manual/pre-outs.

It could be that you are running them into clipping.

I'm using an 805 a pre-amp for an A1400. I can bring my M80s to levels well over 110db (sustain), so this is not a pre-amp issue (unless you have a defective unit).

Rick,

The sound is more scratchy than actual "clipping". I've heard other speakers clip before and the sound is very different.

Also, the amp is bridgeable which the manual states it puts out 150 watts. Don't know if this is true, but it does make my M60's sound louder.

jj

If it is clipping I would expect a scratchy, edgy sound. They very well may be rated as such but who knows what portion of this is usable power. Back some time ago I tried an Audiosource 2 channel pre amp (pre M80s and Rotel). I ended up sending it back because it made my system sound smeared. The sound quality of the unit was less than I desired.

I would have to agree with wid. It sounds to me like you are pushing the limits of the amp and you are now recognizing the 1% distortion they have when bridged in mono mode. To get above the SPL you already achieve from the stock Onkyo amps with clean sound, you need to look at amps with 200W into 8ohm or more.

The M60s can handle just about any amount of power you want to put into them, but the trick, as you are discovering, is to have them still sound clear and for that it takes lots of power.

A rough number from the Crown power calculator, if you are 10 ft away from your speakers and want on avg 95 db from the 89db M60s and you are listening to music with a dynamic range of 10db(a good avg) you will need about 350Watts/ch.

Agreed again on the likelihood of clipping. I have a cheap 50x2 Sherwood amp that I tested in my main room at one point and when I reached the limit of the amp, I heard the exact same "scratchy" sound you are describing.

Jason