# need advice on pro audio amp hookup to onkyo txsr805



## bowser (Feb 11, 2010)

I have purchased 2 cerwin vega cv900 pro audio amps with intention of easy cable conversion to hookup to my onkyo txsr805 reciever. I bought mono 1/4 inch to rca adapters but im getting a loud buzz sound at all volume levels. my question i guess is a ground loop isolator the remedy ? and if so exactly what cables do i need for best sound and ease of hookup and easy on the wallet, I have the understanding that unbalanced & balanced are offending connections and i would be grateful for some advise on what i need fo hookup. my plan is for 1 amp to power my mains, and the other as mono block for my 21 inch subwoofer.


----------



## RLouis (Jan 20, 2010)

Looking at the CV900 manual it looks like you only have one option to possibly reduce the hum somewhat. That's to clip the ground pin from the wall side of the power cord (at your own risk of course). If the noise/hum is coming from the AC ground that will help a great deal, but it may not depending on the source of the hum. Try it with a cheap power cord before clipping the pin on a good cord. The way the manual reads Cerwin strongly recommends use of the balanced connectors.

From manual>> We recommend using balanced three-conductor cabling wherever possible. Unbalanced two-conductor 1/4” plugs can also be inserted into these inputs, but you will get better signal quality and less noise and hum if you use balanced lines.

The amp does not have a ground lift switch on it and there doesn't even appear to be a switch to switch between balanced and un-balanced inputs, as most amps have.

Many times (usually) light dimmer switches and appliances like refrigerators will dump a great deal of noise back into the ground side of a home electrical system and many amps do a great job of returning that noise back out your speakers. Clipping the ground pin, if you don't have a ground lift switch, is the cheapest/easyest way eliminate that source of noise.

If that doesn't work than your only other option may be an unbalanced to balanced converter. That again may help but not completely eliminate the hum. Many "pro" audio amps are just noisy.

Ideally you should get a true home audio amp at least for your mains and just use the CV900 for your sub. Get another 21 and you have dual 21's and dual CV900s to bring the house down!


----------



## tonyvdb (Sep 5, 2007)

The important thing to reduce hum is to make sure that the power for the amp is on the same lag in the breaker panel (there are two) as the rest of the equipment.


----------



## bowser (Feb 11, 2010)

Thanks for response, Ive heard some people say on reviews line level shifters work great. price is pretty steep on some models. I just think removing safety ground is a drastic risk but i see the point behind it. Plus line level shifters work to level out onkyo to the amps potential, causing a higher output overall correct? From reviews some have said amps had dramatic increase in output from using line level shifters. Can anyone verify this claim? I am open to any suggestions anyone has to offer, Again thanks to all


----------



## tonyvdb (Sep 5, 2007)

Seeing as you already have the amp its hard to go backwards however its still better to use an amp that has the proper unballanced inputs. The Samson S-convert is your best choice right now cost wise and you may not need to cut the ground on the amp.


----------



## bowser (Feb 11, 2010)

two 21" would destroy my dwelling hehe!


----------



## bowser (Feb 11, 2010)

Can anyone tell me if i will cause damage to my amps or speakers with this buzz humm problem, Using it until i find a solution. I would not forgive myself if anything catastrophic happens. Thanks for any suggestions


----------



## bowser (Feb 11, 2010)

OK i think a samson s convert is in order, Can a ground loop isolator work between my Onkyo and line level shifters if the samson don't eliminate noise or would that overkill?


----------



## tonyvdb (Sep 5, 2007)

The isolator may work and its better than cutting the ground completely.


----------



## bowser (Feb 11, 2010)

OK thanks for the input, Sounds like i have good options in wich to choose, I welcome any and all suggestions. Thanks.


----------

