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Is this normal? (Read 1883 times)
Hab_Fan
Ex Member



Is this normal?
10/08/06 at 21:32:57
 
Greetings,
           I may have a problem, then maybe I don't. When playing my SE84C through my speakers which 93db efficient,I get the sound breaking up if i turn the input volume control up past 8 out of 10 and my preamp is at 6 out of 10.I have tried this w/o the preamp , with my cd player on fixed and variable, same result. At first I thought I could be overdriving the input but all devices do not exceed 2 volts output. I have tried all the different combinations of tubes, 3 rectifiers 3 different types of output tubes,along with the JAN Philips 6299.
       Last night I had Sarah McLachlan's Surphacing on , The vocals were Crapping out badly, particularly on Witness, which for me is benchmark tune to  check the total fidelity of a system . In the chorus, the vocal starting getting really fuzzy,is the way I can describe it, then it starts to break up. If I turned it down to half volume on the amp then it had no distortion. I checked the cd player and disc on my trusty Scott Lk-72 and it did an admirable job with it. It seems everything is pointing the my beloved Zen .
        If you have any notion of what is going or gone on this puppy please bring it on. as you can imagine I just won't be the same person until I get this resolved !  :(  Thanks Dan
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Eli Duttman
Ex Member



Re: Is this normal?
Reply #1 - 10/08/06 at 22:51:04
 
You are simply running out of steam.  A reasonable rule of thumb requires than an amp/speaker combination be capable of producing 102 dB. SPL peaks at a 1 M. distance.  A higher SPL at 1 M. is needed in a "cavern".  A SE84 produces approx. 2 W. RMS into an 8 Ohm load.  The rule tells us that 99 dB. efficient 8 Ohm speakers are needed.

If you love the speakers you are using, steps have to be taken to increase the available power.  Possibilities include the EX mod and autotransformers that present a 2 Ohm load to the SE84.
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Tr3vWh0r3
Ex Member



Re: Is this normal?
Reply #2 - 10/09/06 at 01:48:22
 
I have an 84C and live in Toronto. If you wanted to arrange something maybe I could bring mine over to see if the same thing happens? Wait a minute.. A Hab fan? Forget that I ever said anything. GO LEAFS GO! Ok, ok I know. Decware forums are a friendly place, so seriously if you want to give that a try let me know.

Trevor
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« Last Edit: 10/09/06 at 01:49:10 by Tr3vWh0r3 »  
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Hab_Fan
Ex Member



Re: Is this normal?
Reply #3 - 10/09/06 at 14:45:54
 

Hey, Now this sounds like a plan! I'll email you to get all the particulars,thanks , Dan
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Doorman
Ex Member



Re: Is this normal?
Reply #4 - 10/09/06 at 16:02:50
 
Yup, Eli is correct. You are pushing your amp past it's limits!
                                                                Don
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Hab_Fan
Ex Member



Re: Is this normal?
Reply #5 - 10/09/06 at 18:02:46
 
Thanks for the reply,

"HONEY, LOOKS LIKE I NEED A NEW SET OF SPEAKERS,I'LL GO WARM UP THE CAR!"......."CAUSE ELI SAYS SO"....."YOU THINK, I WANT TO GET NEW SPEAKERS ?...YES, YOU CAN GET THAT NEW NAIL POLISH YOU WANTED, BUT NOT IF YOU'RE GOING TO TAKE ALL DAY! "
If it was that easy, eh ?  In all fairness that cd is a killer for bringing out the shortcommings of your system,and you don't even have to turn it up. last night I put on Donald Fagens; Morph the Cat, which will melt alot of woofers,and it played that louder than I wanted to hear w/o problems. time to push ahead the next diy project. Thanks for the reality check Dan
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ado420
Ex Member



Re: Is this normal?
Reply #6 - 10/09/06 at 23:25:50
 
[quote author=Eli Duttman  link=1160343177/0#1 date=1160344264]
If you love the speakers you are using, steps have to be taken to increase the available power.  Possibilities include the EX mod and autotransformers that present a 2 Ohm load to the SE84. [/quote]
Is there a specific type of autotansformer to use for this application?

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Hab_Fan
Ex Member



Re: Is this normal?
Reply #7 - 10/09/06 at 23:57:16
 
Hey, I must confess that I've no experience with autotransformer, Correct me if I'm wrong, are these the transformers used in long runs that attach to speaker basket,like on a public address systems? If they are then how would  go about choosing the correct one ? thanks Dan
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Eli Duttman
Ex Member



Re: Is this normal?
Reply #8 - 10/10/06 at 01:53:01
 
[quote author=Hab_Fan  link=1160343177/0#7 date=1160434636]Hey, I must confess that I've no experience with autotransformer, Correct me if I'm wrong, are these the transformers used in long runs that attach to speaker basket,like on a public address systems? If they are then how would  go about choosing the correct one ? thanks Dan [/quote]


Dan,

What you are thinking of are line transformers for use in PA situations.  For HIFI, a different device is required.

A link to HIFI speaker matching autotransformers follows.
http://www.zeroimpedance.com/

A "common" use for the autoformers is to match low impedance speakers to OTL amps that do better with a 16 Ohm load.  However, connecting things up so the SE84 sees a 2 Ohm load with 8 Ohm speakers is easy.

Please observe that the autoformers are expensive.  Another solution to the problem is to acquire a 2nd SE84 and strap the pair of amps into monoblocks.  You get about 8 WPC into 8 Ohm speakers with strapped SE84s.  8 WPC should be adequate if the 93 dB. rating previously given is honest.
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Hab_Fan
Ex Member



Re: Is this normal?
Reply #9 - 10/10/06 at 03:33:31
 
Yep, it would be the cheaper ,easier  just to get another amp......till then I'll sit just a little closer to the fire ,when the need arises. All the best, Dan
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