Quote:
Originally Posted by faranks
right, so I guess I should have clarified a bit, I took for granted that you were using a hi-low level input converter (a box that steps down voltage and turns speaker leads into RCA leads). If you are not using this, and just running the speaker level into a spliced RCA, then you are introducing much more input voltage to the amplifiers preamp than it was ever designed to handle...this is probably (one of) the source of the induced noise. Some amps have a high level input area that is designed to receive an already amplified signal, I am not familiar with that amp though.
This would also explain why you are able to have your gain down so low, your input signal is so hot it is disproportionate. Additionally, you will want your low pass crossover to be set around 80Hz, if it's down much lower you will be missing out on some music.
lastly, the +/- doesn't really matter as long as you're only using one. if you are using 2 (sets) then you just have to be consistent, if they are opposing then they will be out of phase with each other and you won't get much sound. The sub can be out of phase with the music and you will not be able to tell mostly due to variances in room acoustics.
Merry Christmas!
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Hi Faranks
I'm not using a hi-low level input converter as my amp is supposed to be able to handle speaker level outs (although yeah, gain at 25% and still earth shattering base (when it works) may indicate that i probably should be converting to low level inputs)
i''ve also set the low pass filter to around 80Hz.
ok, now with regard to my pumping noise, here's what i've done:
1. I ran (around 30miles) with the RCA grounded yesterday. sound improves when RCA is grounded, but the pumping noise comes up intermittently. so its not entirely gone.
today i drilled a new hole, scraped the paint and did the ground newly, with a 4mm cable.
i then tried the following, hoping that the ground now was good:
1. removed RCA outer grounding, and tried to connect the car speaker outs to the RCA outer. bang! the radio knocks itself out.
2. thought ground could still be bad and made a parallel ground with a 1 1/2ft 4mm cable from the chassis to the amp. still no difference (when i connect the car speaker out to the RCA outer radio goes out)
then i got a bit brave and tried a few other things:
3. removed the RCAs entirely, and then tried to touch the car speaker outs to the RCA outers (RCA inner now disconnected). the moment either cable touches the RCA outer the radio goes out!!
so it now looks like my car head unit or car amp really really hate the RCA outer of my external amp
if you have any further thoughts on above pls let me know,
here's what i plan to try out next:
1. drive around another 40miles or so today (now that the amp is newly grounded (and RCA is grounded) i'm hoping that the pumping noise would have gone away entirely- not even intermittent i hope.
2. if that doesn't work, buy and fix a ground loop isolator? links to 2 units below:
Skytronic Ground Loop Isolator: Amazon.co.uk: Electronics
Ground loop isolator audio noise hum removal: Amazon.co.uk: Electronics
3. alternatively before trying that out, should i fix a hi-low input converter. does that isolate the ground as well? below is what i've found:
FLI Audio Line Level Car Rear Speaker Wire To RCA Converter: Amazon.co.uk: Car & Motorbike
Speaker to RCA Converter / High to low Line Level Converter: Amazon.co.uk: Car & Motorbike
is that the type of thing you suggest faranks?
cheers
j