Engine noise through amp9

[nightfire]

Hey guys,

I tried my Amp9 in my car for the first time last night, and I've been getting some wicked noise coming from it when the engine is running. It's a whistling in tune with the engine speed and it's *loud*.

I tried installing a noise filter (rated 15A) in front of the amp; no difference.

Using a regular Kenwood car amp, there is no noise, so I know the signal from the head unit is clean..

I tried grounding and ungrounding the RCAs directly to the case.. no difference.

Any ideas?

- Gord

[V-bro]

Put a transformer inbetween, when signal is strong enough get a 1:1, when you use a weak signal from an mp3 player for instance get a 1:2 or 1:4 transformer...

I had the same groplem when I connect a source that is also connected to the same ground....so I got myself two OEP A262A2E transformers and all noise is gone now....

------X-max. can be several meters on any driver, too bad it can be done only once...------

[nightfire]

quote:Originally posted by V-bro
[br]Put a transformer inbetween, when signal is strong enough get a 1:1, when you use a weak signal from an mp3 player for instance get a 1:2 or 1:4 transformer...

I had the same groplem when I connect a source that is also connected to the same ground....so I got myself two OEP A262A2E transformers and all noise is gone now....

------X-max. can be several meters on any driver, too bad it can be done only once...------

Interesting...

I actually solved (most of) the problem by installing 4x15000uF caps right at the alternator, but there's still a little whine left so I'll try some transformers.

Thanks!

- Gord

[V-bro]

Hi Gord,

you'll be surprized about the detail richness and dynamics too, at least I was...

[V-bro]

oh and, the OEP trannies can be ordered with a shielding case and bottomplate. My trannies haven't, so when I place it near a power supply tranny I get 50hz hum, but I mainly use it in my car. There iit works quite nice, though if I place it under my chair I still have a very faint bit of noise, easily overruled by even soft music. If I place it above the chairs it's deadsilent. So obviously the shielding could be better...

Here's a picture with the shielding cover and bottomplate:

[abelma]

Hello V-Bro.
I am interested to try a transformer on the input. I wish to isolate the ground from the source to the amplifier ground.
What about the source impedance and amplifier input impedance, what is the parameter to choice for those transfomers?
I need a preamplifier or a psssive pre is good? Can i connect that after a passive preamp?
Thank's for the help.


Living in Belgium

[abelma]

quote:Originally posted by abelma
[br]Hello V-Bro.
I am interested to try a transformer on the input. I wish to isolate the ground from the source to the amplifier ground.
What about the source impedance and amplifier input impedance, what is the parameter to choice for those transfomers?
I need an active preamplifier or a passive pre is good? Can i connect that after a passive preamp?
Thank's for the help.


Living in Belgium

[V-bro]

Hi, I have to admit I left the science of making transformers to the manufacturer. I did check if my output opamps didn't get hot....

It may be a good idea to place the transformer before the passive pre, it will be easier on the source output... With an active pre you might wanna place them before AND after

[abelma]

Thank You V-Bro !
I am looking in the internet information about the transformers inter stages and it sounds very interesting, and also, a solution for my first problem in my AMP10 when one channel input ground disconnect (Bad connector) the source ground from the amplifier input ground >> the 5.6 Ohm output filter resistor went to smoke !. With the transformer the amplifier input ground will be always connected independent from the source ground...i think i am not wrong? (100% neewby and learning here)

[V-bro]

Is there DC on the signal somewhere? Is there a voltage between the two grounds? A transformer can heat up badly from DC current running through the windings...

A ground loop means there is AC current between both grounds from two circuits, it can result in hum, whistling, noise(s)...only once had such a severe loop that it gave shocks and sparked when connecting. This was with a TV to a stereo. It was solved by placing a Monacor RFT-2 filter on the antennasocket...this one produced REALLY LOUD 100hz hum...

Still pretty strange it smoked the resistor, a transformer could provide a solution here I think. You won't be disapointed with the sonic qualities