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Post subject: Fender deluxe 65 reissue speaker extenseion impedance
Posted: Tue Dec 23, 2008 8:36 am
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I just bought a Fender deluxe 65 reissue, and see that the manual states that the extension speaker jack is wired in parrallel with main speaker jack thus affecting the overall impedance of the amp. I have a mesa boogie 4 x 12 8 ohm cabinet that I want to use as the extension cab. With the 1 12 8 ohm speaker in the amp they create a 4 ohm load on the amp. I have been having interminttant tone issues with the amp. It typically sounds beautiful and bright like it should, but sometimes the tone will fade and get a little more distorted.... not as bright. Could this be cause by the impedance mismatch? THere seems to be a lot of opinions on this issue. I also hear a bit of a crackling sound at idle every now and then. Its no big deal, but I just mentioning it in case there could be a connection. I talked to a local fender tech and he said that the ext speaker jack is made for running an 8 ohm speaker. The manual clearly states differently, so I am a bit reluctant to have him work on it at this point. It does state in the manual that an impedance mismatch can damage the amp, but it goes into no more detail than that.

So I guess the only way to match the impedance with an extesnsion cab is to replace the speaker in the amp with a 16 ohm speaker and then rewire my 4 x 12 to 16 ohms thereby creating an 8 ohm load on the amp. Seems like a lot of work to use an extension. ... and then I will have a mismatch if I dont use the extension cab. I have also read that an impedance mismatch of 1/2 or double should not damage the amp.... but could affect the tone. So im my case a 4 ohm load or a 16 ohm load should not hurt the amp, but can hurt the tone.


So I am just looking for some clear information on the impedance issue and the best way to deal with using an extension speaker on my amp without causing any damage to the amp or the tone.

--Rick


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Posted: Tue Dec 23, 2008 12:50 pm
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You should use an 8 ohm cab plugged into the ext. speaker jack. The cab and internal speaker will be in parallel to make 4 ohms, which is safe to do. If Fender didn't want you to plug in an ext. cab, they wouldn't have put it on the amp! I have never read about anyone having a problem doing this with a Fender 8 ohm tube amp. I'm not positive, but it's possible that the DRRI has an 8 ohm and a 4 ohm tap on the transformer. The 4 ohm tap is used when you plug an 8 ohm cab into the ext. speaker jack. The Blues Junior doesn't have an ext. speaker jack, but the amp runs fine if you use a splitter and use an 8 ohm cab in parallel with the 8 ohm internal speaker.

Are you having a problem with your sound without using the Mesa cab? If so, then it's probably tube-related. Even new tubes can be bad.


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Post subject: Fender deluxe 65 reissue speaker extenseion impedance
Posted: Tue Dec 23, 2008 1:20 pm
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So the 8 ohm speaker in the extension jack ( 4 ohm Load) should not cause any deteriation of sound quality? I have read that it does on some other forums, but am not sure if that was accurate information. If not then I probably have some other issue with the intermittant tone issue. It just seems to lose some of its high end at times and then seems to come back and work fine. I used it at a gig with the extension speaker on Sunday, and over a 4 hour gig, the tone was bad about 50% of the time. And its not terrible... its just noticably different. I played it last night without the extension speaker for a few hours and had no trouble. I replaced every cord in my system to eliminate that variable.


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Post subject: Re: Fender deluxe 65 reissue speaker extenseion impedance
Posted: Tue Dec 23, 2008 3:46 pm
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WAKEBRDR549 wrote:
I played it last night without the extension speaker for a few hours and had no trouble. I replaced every cord in my system to eliminate that variable.



So, if the DRRI was fine by itself, then the problem could be a bad speaker cable, or something is wrong with the Mesa cab. Maybe you have a bad speaker(s) in it?


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