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Post subject: DRRI External Speaker
Posted: Sun Jul 17, 2011 8:21 am
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Just purchased the DRRI and have a question about using the amp with an external speaker.

I searched this forum and read past comments, but something still doesn't add up.

If the impedance of both speaker jacks combined is 8 ohms, that implies that the amp requires both the internal speaker and external speaker to both be 16 ohms when used together (as the jacks are wired in parallel).

But that would mean that you would need to change the internal speaker back to an 8 ohms version anytime you wanted to use just the internal.

Does this make sense that Fender would design it this way?

I've read elsewhere that Fender designed the amp to handle a 100% mismatch with internal and external 8 ohms speakers connected (running at 4 ohms).

Can someone from Fender clear this up?

Any insight would be greatly appreciated.


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Post subject: Re: DRRI External Speaker
Posted: Sun Jul 17, 2011 8:53 am
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PaulSurf wrote:
If the impedance of both speaker jacks combined is 8 ohms, that implies that the amp requires both the internal speaker and external speaker to both be 16 ohms when used together (as the jacks are wired in parallel).


You are correct.

The amp will tolerate a certain amount of mismatch but I would not trust the output tranny in the re-issues as I would the vintage models (which were designed to permit as much as a 100% mismatch, as you mentioned). I sidestepped the issue altogether by installing a custom OT in mine that has dual secondary taps (8Ω and 4Ω) and use the dummy "polarity" switch on the rear panel to select the impedance I need whenever I run an extension cab with the amp.

HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: DRRI External Speaker
Posted: Mon Jul 18, 2011 8:35 am
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Thanks Arjay.

Your impedance switch sounds like a good solution.

Paul


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Post subject: Re: DRRI External Speaker
Posted: Mon Jul 18, 2011 10:21 am
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The older '65 re-issues (pre '98, I believe) have a "polarity" switch on the rear panel that is connected to precisely nothing. It's just there for "vibe" since the original blackfaces had them. But it's a genuine 250VDC 3A Carling -- ideally suited for its new mission as an impedance selector. It spares the chassis the indignity of having a non-standard hole drilled into it somewhere to mount an aftermarket switch.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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