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Old 23rd March 2013, 19:02   #421
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Default Re: Queries in 'Ask the gurus' section

I am using a JBL 3501 rated at 360w rms @ 2 ohms for 1 channel.3501 has two output channels. Does this mean it has total of 720w rms ?
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Old 23rd March 2013, 19:27   #422
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I am using a JBL 3501 rated at 360w rms @ 2 ohms for 1 channel.3501 has two output channels. Does this mean it has total of 720w rms ?
Check the manual:
225W RMS x 1 channel@4 ohms and <1%THD
360W RMS x 1 channel@2 ohms, 14.4V supply and <1%THD

Perhaps you are confused with the provision for 2 'speakers'. This amp is a mono, and caters to only one sub 'channel' - which can be one or more than one sub or coil in parallel or series. It just has 2 connectors for wiring convenience.

Depending on what you connect and how (1 SVC sub 4ohms or 2ohms, 1 DVC sub of 4ohm each coil, 2 SVC subs of 4 ohms each etc.), the sub(s) will present an effective impedance to the amp. This impedance governs how much max power the amp will be able to push into that load. The safe max is still 360W RMS. You can exceed it by sending a larger input signal than permitted (6V), but then you will be hearing weird noises - and possibly seeing the ghost of the amp (greyish-white, smoke-like, just like in movies) soon thereafter.
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Old 23rd March 2013, 19:53   #423
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Default Re: Queries in 'Ask the gurus' section

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Originally Posted by DerAlte View Post
Check the manual:
• 225W RMS x 1 channel@4 ohms and <1%THD
• 360W RMS x 1 channel@2 ohms, 14.4V supply and <1%THD

Perhaps you are confused with the provision for 2 'speakers'. This amp is a mono, and caters to only one sub 'channel' - which can be one or more than one sub or coil in parallel or series. It just has 2 connectors for wiring convenience.

Depending on what you connect and how (1 SVC sub 4ohms or 2ohms, 1 DVC sub of 4ohm each coil, 2 SVC subs of 4 ohms each etc.), the sub(s) will present an effective impedance to the amp. This impedance governs how much max power the amp will be able to push into that load. The safe max is still 360W RMS. You can exceed it by sending a larger input signal than permitted (6V), but then you will be hearing weird noises - and possibly seeing the ghost of the amp (greyish-white, smoke-like, just like in movies) soon thereafter.
Thanks a lot. I am running two dvc(4ohm each coil) wired as 2 ohm load on each speaker terminal of amp .The RMS power of each woofer is 350watts. I am still able to run the set up using 3501 .I have a infinite baffle setup for both woofers .Do you suggest upgrading to GTO 7001 or i can continue with above setup.

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Old 23rd March 2013, 20:18   #424
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... I am running two dvc(4ohm each coil) wired as 2 ohm load on each speaker terminal of amp ...
Can't make out how exactly the subs are wired, but that would either present a 1ohm (all coils in parallel) or 4ohm load (2 coils of each sub in series, 2 subs in parallel) to the amp. Most likely the 4ohms one, since it would go into protection if 1ohm.

If you want full potential of the subs to be exploited, yes 7001 would be better with 4ohms load. Otherwise, you have to hunt for a large mono that can take 1ohm load safely.
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Old 23rd March 2013, 20:48   #425
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Can't make out how exactly the subs are wired, but that would either present a 1ohm (all coils in parallel) or 4ohm load (2 coils of each sub in series, 2 subs in parallel) to the amp. Most likely the 4ohms one, since it would go into protection if 1ohm.

If you want full potential of the subs to be exploited, yes 7001 would be better with 4ohms load. Otherwise, you have to hunt for a large mono that can take 1ohm load safely.
First DVC woofer is wired in paralled to present 2 ohm load to one speaker output.The second is also wired like this to second speaker ouput .So for each speaker output i have a two ohm load.This is the way i have wired the subs.

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Old 24th March 2013, 10:29   #426
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No, this is not alternator while. Alternator whine is a kind of trrrrnnnnn sound which varies with RPM. I am sure it doesn't in your case. Cure for that is grounding the amp properly.

The hiss that you are getting is most likely due bad quality screened RCA cables. Try changing them to see if the hiss vanishes. Also, try twisting a bare copper wire strand around the outside of the RCA sockets at the back of the HU, and connect the wire to a mounting screw on the HU's cover at the back.
Yes, the RCAs are not of very high quality, will change them to Gladen ones ASAP. Also IIRC, the grounding was done on a thin sheet of mettal, I'll try changing the grounding point at the earliest.
Will also try the copper wire activity. Thanks a lot for your advice.
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Old 24th March 2013, 11:11   #427
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First DVC woofer is wired in paralled to present 2 ohm load to one speaker output.The second is also wired like this to second speaker ouput .So for each speaker output i have a two ohm load.This is the way i have wired the subs.
A-ha, 1ohm load effectively. You are lucky not to have blown the amp fuses - maybe you didn't go really loud so far.

It is better for you to look for a mono that is 1ohm capable. Or get the 7001 to work at 4ohms (wire each sub's coils in series, and the subs in parallel).
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Old 25th March 2013, 15:58   #428
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A-ha, 1ohm load effectively. You are lucky not to have blown the amp fuses - maybe you didn't go really loud so far.

It is better for you to look for a mono that is 1ohm capable. Or get the 7001 to work at 4ohms (wire each sub's coils in series, and the subs in parallel).
I am using 1004 to drive front and rear speakers . Now when i switched over to 7001 today i get a whine(from all 4 speakers only not woofers) and i find it is coming due to 7001 .And using exactly the same setup 3501 does not have any whine from any speaker.

What can be the reason?
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Old 25th March 2013, 17:14   #429
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I am using 1004 to drive front and rear speakers . Now when i switched over to 7001 today i get a whine(from all 4 speakers only not woofers) and i find it is coming due to 7001 .And using exactly the same setup 3501 does not have any whine from any speaker.

What can be the reason?
Did you put back the 3501 to check?

This sounds like the grounding is disturbed when you connect the 7001. Try grounding the outer connection of the RCA sockets of the 7001 to the nearest grounding point. Run a length of bare copper wire around the sockets to do that.
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Old 25th March 2013, 17:36   #430
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Default Re: Queries in 'Ask the gurus' section

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Did you put back the 3501 to check?

This sounds like the grounding is disturbed when you connect the 7001. Try grounding the outer connection of the RCA sockets of the 7001 to the nearest grounding point. Run a length of bare copper wire around the sockets to do that.
Yes when all failed i put back the 3501 .7001 still with me (Inr11600/- down the drain and i feel bad about it). When i connected 7001 I tried connecting RC leads outer part using a wire to connect to ground but the whine increases with that .I tried connecting 7001 body with earth point using a 4 gauge wire it had no effect.I even tried connecting RC leads outer part to earth coming into amp and whine increased.Though i could do it for only one RC lead and not for pair combined.

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Old 25th March 2013, 18:34   #431
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Yes when all failed i put back the 3501 .7001 still with me (Inr11600/- down the drain and i feel bad about it). When i connected 7001 I tried connecting RC leads outer part using a wire to connect to ground but the whine increases with that .I tried connecting 7001 body with earth point using a 4 gauge wire it had no effect.I even tried connecting RC leads outer part to earth coming into amp and whine increased.Though i could do it for only one RC lead and not for pair combined.
A-ha! OK, the problem is not with the 7001. The problem is still grounding, but it looks like you are introducing some difference in the wiring scheme when you are putting in the 7001 in place of the 3501. That should explain the whine coming through whatever is connected to the 1004 also. If you manage to switch only the 1004 off, you will find the whine in the subs also.

Are you doing the installation yourself, or is an installer doing it for you? One possibility is trying with another 7001 or any other mono amp, if there is a likely issue of grounding with your 7001 (and then you can return the faulty 7001). The other is trying the RCA grounding at the HU end (which HU do you have?).
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Old 25th March 2013, 22:21   #432
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A-ha! OK, the problem is not with the 7001. The problem is still grounding, but it looks like you are introducing some difference in the wiring scheme when you are putting in the 7001 in place of the 3501. That should explain the whine coming through whatever is connected to the 1004 also. If you manage to switch only the 1004 off, you will find the whine in the subs also.

Are you doing the installation yourself, or is an installer doing it for you? One possibility is trying with another 7001 or any other mono amp, if there is a likely issue of grounding with your 7001 (and then you can return the faulty 7001). The other is trying the RCA grounding at the HU end (which HU do you have?).
I have a kenwood 8016BT and i do installation myself as i donot like people tearing my small car apart. Let me explain a bit further. I hook up 1004 there is no whine .I let 1004 stay connected now. I hook up 3501 there is no whine. Instead of 3501 i hook up 7001 i have whine even in speakers connected to 1004. If i remove RC leads going into 7001 whine goes away.If i put these RC leads into 1004 (by removing one pair from it ) there is no whine.The person i bought it from says it is not possible to replace 7001 . The wiring scheme and routing is not changed at all . I will go to the shop tommorow i bought 7001 from to see if he helps else it is money down the drain .
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Old 27th March 2013, 10:34   #433
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... I will go to the shop tommorow i bought 7001 from to see if he helps else it is money down the drain .
That's great - something that you can / should be proud of.

Don't worry, it won't be money down the drain. Call the JBL service guys, and explain the problem to them. They will anyway ask you to come to the service center. The problem that you are facing is a ground loop problem with the 7001. The JBL service guys will be able to solve it. If there is something seriously wrong, they will replace the piece.
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Old 27th March 2013, 10:37   #434
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That's great - something that you can / should be proud of.

Don't worry, it won't be money down the drain. Call the JBL service guys, and explain the problem to them. They will anyway ask you to come to the service center. The problem that you are facing is a ground loop problem with the 7001. The JBL service guys will be able to solve it. If there is something seriously wrong, they will replace the piece.
I returned the 7001 piece yesterday and await a fresh piece.
Hopefully will get it by tomorrow.
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Old 28th March 2013, 11:00   #435
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So for each speaker output i have a two ohm load.This is the way i have wired the subs.
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I returned the 7001 piece yesterday and await a fresh piece.
Hopefully will get it by tomorrow.
did the JBL shop see the faulty 7001?
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