4 Ohm Speakers Burn Up Amps

 

New member
Username: Jportela

Post Number: 1
Registered: Sep-04
I have burned up three amps (Sony STRDE845, HK 330, Sherwood 756) trying to run a surround system with 4 ohm Tower Phase Technology PC 500s as front speakers (Ebay deal). My next try will be a Marantz 7400 ($700 limit)). Does anybody out there have a better idea please.
 

Bronze Member
Username: Natediggidy

Baltimore, Maryland U.S.A.

Post Number: 44
Registered: May-04
Just make sure the receiver you choose is able to handle 4-ohm speaker loads. Both of my Sony's (older models) have a switch on the rear panel that can be set for either 4 or 8 ohm speakers.
 

New member
Username: Jportela

DFW

Post Number: 3
Registered: Sep-04
Thanks. The Sony STR 845 I had does have a switch and still fried itself. I have a second one that runs very hot but I cool it with a fan. I stopped using it because I did not want to lose two amps.
 

Gold Member
Username: Project6

Post Number: 1519
Registered: Dec-03
There's not a lot of amps out there that can handle 4 ohm loads, especially mass market receivers. I hope you got your money back for the Sony.
 

New member
Username: Jportela

DFW

Post Number: 5
Registered: Sep-04
Nope the Sony was out of warranty. The other two are in the process of being returned.Do you know if the Marantz will work or any other for $700? Thanks.
JP
 

Silver Member
Username: Rick_b

New York USA

Post Number: 494
Registered: Dec-03
Jose,

To the best of my knowledge, the Marantz will not handle a 4 ohm load.
 

New member
Username: Jportela

DFW

Post Number: 8
Registered: Sep-04
Ok, thanks to many of you I think I have it under control. I will purchase the NAM T753 for $800. So so price and out of my budget but the person selling it is also the PC500s repair rep and will fix them at cost for me if they are bad. Again I welcome any inputs today and Thank you all again!
 

Silver Member
Username: Gman

Mt. Pleasant, SC

Post Number: 615
Registered: Dec-03
I would try Audiogon.com and see what they have in used solid state amps. I just perused the site and saw a couple of Aragon's at $450 and $650--both excellent amps and easily will drive any 4 ohm amp--saw some Rotel's, Adcom's, etc. that are in your price range.

Of course, this is probably only good if you are in the US. Most individuals won't ship internationally.
 

New member
Username: Jportela

DFW

Post Number: 10
Registered: Sep-04
Will check it out, thanks!
JP
 

Silver Member
Username: Fryguy

Nova Scotia Canada

Post Number: 254
Registered: Jun-04
http://fryguy.ca/Forum/viewtopic.php?p=37#37 for my article on Impedance and Resistance to explain the difference between them.
 

Bronze Member
Username: Jportela

DFW

Post Number: 11
Registered: Sep-04
Thanks, read the article, some of it was above my level.
JP
 

Silver Member
Username: Fryguy

Nova Scotia Canada

Post Number: 259
Registered: Jun-04
what part then i can revise it to be more clear.
 

Bronze Member
Username: Frank_abela

Berkshire UK

Post Number: 90
Registered: Sep-04
Jose

Have you considered that instead of the amps, it's the speakers which are at fault? I don't know the amps you have tried and of course, if they don't have much current capability they would have a problem but you should hear distortion well before the amps give up the ghost.

I'm thinking that if any of the speakers are faulty, one of them could be acting as a short circuit which would then fry almost any amp. The only way to tell would be to connect them to an oscilloscope and check their impedance against frequency. If one of the speakers (any one) dips below 2 ohms for any length of time, chances are that's your problem.

If that's not a problem check your wiring closely to make sure there's no short circuits there (I have had one customer who had put a spike through the cable and shorted it out without realising. Funny thing is the huge amp he was using simply drove more and more current into it until it still burned out one of the speaker units!).

Regards,
Frank.
 

Bronze Member
Username: Jportela

DFW

Post Number: 12
Registered: Sep-04
PC 500s work great on stereo mode. I had the Phase Tech rep/repair guy do a check on them when he came to deliver the NAD 753 and install the whole system again.

The NAD still shutsdown when I crank up the volume with the surround mode on so I have resigned myself after blowing my budget to operate that way: Phase Tech PC 500s in Stereo mode no problem... but with (6 channel mode) the A/R C-225 center, Teatro 4.5s and a single teatro surround center only limited normal volume but great sound anyway.

In summary; I am sure a high end amp would solve the problem but it would create a bigger economic issue at home.

All that being said...I do not like the A/R center speaker sound, could I replace it with an extra Phase Tech Teatro surround I have or one of the teatro 4.5s as a center. I have two of each and I really like them. Thanks Frank!
JP
 

Silver Member
Username: Hawk

Highlands Ranch, CO USA

Post Number: 620
Registered: Dec-03
Jose:

I currently run a 5.1 system of Dynaudio 42s, each of which are 4 ohm rated and at some frequencies, they dip as low as 3.4 ohms. The only thing I could find that would drive five 4-ohm speakers in a receiver was NAD (I got the T753 as well--best purchase I ever made!). It has been flawless and handles 4 ohm loads with aplomb. Now, the NAD is rated to handle 2 ohm loads, so if your NAD got fried, it has to be the speakers. So IMO, adding a high end amp would not solve your problem.

Let me suggest another idea--set your 753 up as a three channel system by just running the front three speakers. Set the surrounds to "Off" at the receiver and see what happens. Also disconnect the sub (as you may be getting a feedback signal from the sub's amp which is causing a problem--it is a real longshot, but you never know). If the three channel system runs ok, you can add speakers back one at a time, starting with the sub. If this works ok, then add the rear surrounds (but not the center rear). This should allow you to isolate where the problem is.

Good luck!
 

New member
Username: Booger

Post Number: 1
Registered: Oct-04
Regarding the rear panel switch, this article - http://www.audioholics.com/FAQs/4-ohmspeakersreceiver.php - says:

NOTE: Some Receivers have an impedance selector switch. DON'T USE THEM! The manufacturer puts them there for UL approvals as well as easing consumer concerns about driving low impedance loads. These switches step down voltage feed to the power sections which will limit dynamics and overall fidelity. Keep the switch set for 8 ohms regardless of the impedance of your speakers and ensure proper ventilation of the Receiver.
 

mauimusicman
Unregistered guest
Bob.......that advice is lethal, dude
 

Bronze Member
Username: Jportela

DFW

Post Number: 13
Registered: Sep-04
Thank you all for the great advice!
JP
 

Gold Member
Username: Kegger

MICHIGAN

Post Number: 1816
Registered: Dec-03
Jose I see no has mentioned that you could pretty much use any
reciever and then run a quality 2 channel amp that handles 4 ohms
just for your front speakers!

Use the front preamp outs from the reciever to the 2 channel amp
then run your front speakers from the new amp!
That would eleviate a lot of work from the reciever
and put your 4 ohm speakers on a propper amp.

In the end should sound better too.
1. because the reciever isn't working as hard.
2. you will more then likely have a better amp running the fronts now!
 

Bronze Member
Username: Jportela

DFW

Post Number: 15
Registered: Sep-04
OK, I felt that would work but again, I really am not an audiophile.
I am also on a budget I already blew on the NAD 753.
My plan is to stick to NAD and buy an amp/receiver(I could use the phono input on the receiver) on Ebay. They usually have used ones at prices I can afford. If you would be so kind (or anyone else) could you look at the ones for sale on Ebay and recommend a couple of models at less than $200 please. Any other ideas are welcome. Many thanks.
JP
 

Gold Member
Username: Kegger

MICHIGAN

Post Number: 1817
Registered: Dec-03
If your trying to stay at say 700 or less.

Then a reciever in the $500 or less catagory with another 2 channel
amp in say the $200 or less catagory may be an appropiate place to
start looking!

When I get a chance I could see what's out there!
 

New member
Username: Georgeo

Townsville, QLD Australia

Post Number: 1
Registered: Nov-04
I ve just bought a marantz SR4300 Amp Receiver, and are running sony speakers which all have impedances of 8 Ohms, but at the back of the Amp under the speaker terminals it says rating of 6 Ohms. Will i blow my amp or my speakers on this system?
 

Silver Member
Username: Fryguy

Nova Scotia Canada

Post Number: 335
Registered: Jun-04
no, your fine. Just dont run speakers lower then 6 ohms (lower would be a 4 ohm speaker)or parallel speakers your 8 ohm speakers on one channel.
 

Bronze Member
Username: Jportela

DFW

Post Number: 16
Registered: Sep-04
You do not say how many speakers... but I believe with the information you gave me the answer is NO WAY will you blow them.
JP
 

Silver Member
Username: Fryguy

Nova Scotia Canada

Post Number: 336
Registered: Jun-04
If you have 8 ohm speakers and the amp says it can handle a load down to 6 ohms per channel then your fine.
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