Amplifier recommendation

jaynana · Post by **jaynana** » Mon Dec 26, 2011 9:10 am

i was stuffed last night - sort of late lunch which ended up with dinner; another one today, at an aunts

thanks Sanj, yes that's what i've done, right? i've tapped onto the rear left and rear right from the BM54.

i get the low end sound allright, with only the RCA inner of the amp connected (either both left/right or left and right).

the issue sanj is that the moment the RCA outer (again either both left/right or left and right). the radio knocks itself out cold (not sure if its the head unit or the BM54 that goes out though cos its all the speakers that go quiet).

whilst producing base, the amp starts developing a low freq pumping noise. (there's also other ambient noise which can be cancelled out by setting the low filter of the amp)

somebody told me this could be a grounding problem ie, when the amp is not properly grounded the amp draws ground through the RCAs. is that what it is?

any help is highly appreciated Sanj

Sanj · Post by **Sanj** » Mon Dec 26, 2011 10:38 am

So where have you taken your ground point from? Is the cable as short as it can possibly be, also?

Is the amp new or 2nd hand?

Take a pic of either end of the amp and show what you've connected where.

jaynana · Post by **jaynana** » Mon Dec 26, 2011 4:12 pm

how do i attach photos? that seems more complicted than fixing an amp:)?

in anycase, here are the clarifs u asked for:
1. its not a second hand sub but i had this in my previous car for many years. ive changed cars so now i'm trying to fix this into the E53 X5. ive had no probs with it in the previous car so i don't suspect the sub.
2. ground cable is a 4mm, connected to the chassis with paint scraped with a size 10 bolt. because its a bit long, to eliminate the possibility that its prob not grounded well enough what i did was i got another 1 1/2 ft long 4mm cable and did a parallel connetion to the chassis. made no difference.

i've made some progress, although i've not fixed the issue.

ive grounded the RCA outer to the chassis. this seems to increase amp output, and eliminate the pumping noise.

i've driven around with this config since yesteray (around 30 miles). and i've figured that its not entirely fixed, and the sound comes intermittently.

all of above is still with one or both of BM54 speakers connected to the RCA inner only. The moment i touch the BM54 speaker output to the RCA outer, the radio knocks itself out! and either it starts again in a few seconds (this is new, since i grounded the RCA outer); or i need to press a channel (1 to 6 buttons) or switch the radio on/off to get it working again.

ive also done some (brave or stupid) testing.

with or without the RCA outer grounded, the moment one of the BM54 cables touch the RCA outer, the radio knocks itself out cold! (and then i have to restart as above).

so its like.. now the system is working (maybe i'm speaking too soon, i will tell you tomorrow after todays run of around 30 miles). but this is with the RCA inner conneted to the BM54 output; RCA outer (only one of them actually) grounded to the chassis.

rather annoyingly i can't get BM54 output properly connected to the amp!!

sorry if i'm all over the place, tahts cos i'm no professional! pls let me know what you think based on above. also if you tell me how to uplaod photos i can do that too (i've taken photos, only to realise there's no option to upload!)

cheers

j

phill · Post by **phill** » Mon Dec 26, 2011 4:37 pm

You need to joint photo bucket upload your photos there and then copy the img links shown below the photo in photo bucket, then paste this into your post.

Phill

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Rusty · Post by **Rusty** » Mon Dec 26, 2011 4:55 pm

Are you taking the high level speaker output from the BM54 directly into the low level RCA amp input? I know I asked earlier but it may have been missed. On my setup, the speaker output from the stereo is wired to the 'high level input' on the amp. If I weren't using this input I would have to use a high to low level converter to be able to supply the correct signal to the amp.

Just a thought

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jaynana · Post by **jaynana** » Mon Dec 26, 2011 5:03 pm

[quote=""phill""]You need to joint photo bucket upload your photos there and then copy the img links shown below the photo in photo bucket, then paste this into your post.

Phill

Sent from my iPod touch using Tapatalk[/quote]

wht? sorry mate didn't get that

jaynana · Post by **jaynana** » Mon Dec 26, 2011 5:06 pm

[quote=""rusty nail""]Are you taking the high level speaker output from the BM54 directly into the low level RCA amp input? I know I asked earlier but it may have been missed. On my setup, the speaker output from the stereo is wired to the 'high level input' on the amp. If I weren't using this input I would have to use a high to low level converter to be able to supply the correct signal to the amp.

Just a thought

Sent from my iPod device using Tapatalk[/quote]

yes, i'm taking the output from the bm54 directly into the RCA amp input. this should theoritically work cos my amp says it supports high level inputs; but the gain is set at around 25% and the base is earth-shattering (when it works!) so i guess a high-low input converter should be helpful.

i don't mind doing that, but can somebody tell me why my car head unit or the BM54 simply hate the amps RCA outer? that doens't sound normal, right?

jaynana · Post by **jaynana** » Wed Dec 28, 2011 11:47 am

guys, any more help on this pls?

another possible thought from another forum - are the BM54 speaker outputs balanced outputs rather than one being grounded?

Rusty · Post by **Rusty** » Wed Dec 28, 2011 12:36 pm

[quote=""jaynana""][quote=""rusty nail""]Are you taking the high level speaker output from the BM54 directly into the low level RCA amp input? I know I asked earlier but it may have been missed. On my setup, the speaker output from the stereo is wired to the 'high level input' on the amp. If I weren't using this input I would have to use a high to low level converter to be able to supply the correct signal to the amp.

Just a thought

Sent from my iPod device using Tapatalk[/quote]

yes, i'm taking the output from the bm54 directly into the RCA amp input. this should theoritically work cos my amp says it supports high level inputs; but the gain is set at around 25% and the base is earth-shattering (when it works!) so i guess a high-low input converter should be helpful.

i don't mind doing that, but can somebody tell me why my car head unit or the BM54 simply hate the amps RCA outer? that doens't sound normal, right?[/quote]

My amp supports high level inputs, but has a separate input connector.

I would def look at that as you could damage the amp otherwise if you are putting too high a signal in.

Speakers may not be grounded on one side, so yes that would cause a problem too.

Good luck mate

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jaynana · Post by **jaynana** » Wed Dec 28, 2011 12:56 pm

thx, which one of these will you recommend mate?

1.
http://www.amazon.co.uk/Bumper-High-Con ... 15&sr=8-13

2.
http://www.amazon.co.uk/Audio-Line-Leve ... =8-1-fkmr2

3.
http://www.amazon.co.uk/Speaker-Convert ... 715&sr=8-1

note that the 1st one (Bumper) has a ground loop isolator built into it. given my issue im tempted to try that out. but the cheap price worries me though.. plus never heard of that brand.

FLI is the brand commonly available at Halfords, its French i think.. but it has no adjustments..

does anybody have any other suggested high-low converters with ground loop isolation built in?

Rusty · Post by **Rusty** » Wed Dec 28, 2011 8:22 pm

Wouldn't like to say one way or another, but 1&3 look similar except 3 has the flying leads. None contain too much inside, so just pick the one you think suit best as I'm sure any of them would work.
Before you buy though, I do have a one in the garage, I'll have a look at that one for you.

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jaynana · Post by **jaynana** » Wed Dec 28, 2011 11:12 pm

3rd has many versions of it in different sites with different brand names. u know what that means.. some unbranded chinese unit, so i wouldn't go for it.

cheers mate, lemme know if u find it pls..

j

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