AX-Tu4360c

[lazeris 0]

After almost 20 hours I finally got my system up and running. Integrating into a Factory system with a Navagation unit is a headache but I did it. I used a RF 360.2 to send the signal to my amps. I have not put in the AX-3200DE yet but that will be this weekend along with my RE MX18.

So I should start off by saying this amp sounds amazing. I am running my stock speakers and it makes them sound soo much better than the stock amp. There are things I am hearing in my music that I couldnt hear before. The only issue I have is that when the volume is low or where there should be silence in the music there is HISSSSSS. I dont think its normal and I have identified the amp as the cause of the hiss. If I disconnect the RCA's into the amp the hiss is still there so I assume it is the amp. I called Greg at US Amps and he recomended a couple things that didnt help at all so he said that I would have to take it back to the dealer and have them send it in. After waiting so long to get this amp installed I am disapointed that I have this issue. Oh well at least its not ground noise, although the hiss is kind of loud. Any ideas? Oh and the gains are completely set to 0 I cant turn them down any more. Another thing that tells me its the amp is that if I turn the gain up the hiss gets louder. I may just live with it I dont want to wait a long time to have to send it in and wait to get it back.

[JimJ 11]

There's way, way too much gain in the preamp stage, I noticed the same problem when I auditioned the TU-300C. IMO, 12AX7's have no place in hi-fi equipment...six volt tubes like the 6DJ8 or 6922 are vastly better to use.

There are tubes out there like the GE 5751 that have less gain than a 12AX7, that might reduce the problem but I can't say for sure as I didn't have any on hand to try...places like the Tube Store and Tubedepot.com sell them, IIRC...

[thanosdbfan 0]

I used to have similar problems with my old school TU 600...

Try to do the next.

1.Check your amplifier ground wire connection.It is best to sand off the paint on the chassis ground connection spot.

2.Use a bigger ground wire

3.Try to use a single ground spot for every unit (one for each amp one for the proccessor etc)

4.Don't use a capacitor.Useless...(at least for USAMPS)

If you see any improvement,check the power wire/wires.

Last thing you should check is the RF (360.2) unit.There is a possibility that it my not be compatible with the input of USAMPS.I have witnessed this with my old symmetry EPX 2 (A lot of hiss and popping when i turned off the amps).Problem was solved with a new USX-3

[JimJ 11]

It's really not ground noise, I know exactly the noise he's talking about, and it happened to me when I hooked the TU300C up to a bench DC power supply, so there couldn't have been a ground loop there

IIRC, your amp has a different (better-designed, lower-gain) preamp stage.

[lazeris 0]

The problem is at the amp. I can disconnect the 360 from it and still get the hiss.