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Author Topic: The Dangers of Speaker Impedance Mismatching  (Read 308 times)

looselectron

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The Dangers of Speaker Impedance Mismatching
« on: December 05, 2019, 12:33:12 AM »
Hello. New forum member here, and a proud owner of two of three Peavey Blazers. Why two of three? Well, I was so impressed by this little amp that I wanted another to use with for stereo delays. Unfortunately the second one I got for $12 didn’t work right. So recently I found a third for less than $50 which works fine...so far.

Unfortunately, the first one and the second one seemed to go bad at the same time which could be caused by:

A. Manufacturing defects... :duh
B. Using them together in stereo without proper grounding.  xP
C. Unplugged cables lying on a static-charged carpet.   :o
D. Swapping the stock 4Ω speakers in both each with an 8Ω Jensen C8R. :loco
E. None of the above.  ::)

Can we rule out D?

The data sheet for the TDA2040 suggests it will work fine with an  8Ω speaker, and indeed I found the amp sounded better that way.

OR could the speaker dampening circuitry in Transtube amps make it susceptible to damage?

phatt

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Re: The Dangers of Speaker Impedance Mismatching
« Reply #1 on: December 05, 2019, 03:28:27 AM »
"Amp going bad" is a very vague term.
Maybe explain the symptoms and folks here might be able to help you out.
I doubt the damping is an issue.
Phil

Enzo

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Re: The Dangers of Speaker Impedance Mismatching
« Reply #2 on: December 05, 2019, 11:44:14 AM »
We are technicians, we need to know what the problem is.  "Goes bad" doesn't help.

A.  I have been an authorized Peavey repair center for over 30 years, and I have never seen one of their products so defective they fail en masse.  For that matter I cannot think of any brand like that.  Besides even if there were some systemic failure, it wouldn't happen to all of them at the same time.

D.  No.  Any solid state amp will run cooler on 8 ohms instead of 4 ohms, it puts out only half the power that way.  So no issues there.  I suspect the difference in sound is not the ohms, but the brand and model speaker.

C.  Cables and carpet?  No.

B.  Not likely.

I choose E.


One of these amps if fully repaired, should run about forever.

looselectron

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Re: The Dangers of Speaker Impedance Mismatching
« Reply #3 on: December 09, 2019, 10:23:27 PM »
Sorry.  :-[

"Bad" means some unwanted clipping on the clean channel in one amp. The Peavy Forum suggested retightening the screw grounding the power amp to the heat sink , and that seemed to help, but it still breaks up a bit near max volume which is to be expected, right.

In the other amp, it means awful clipping like a starved fuzz, a MID control that seems to have no effect, and no signal to the reverb tank.

So maybe the op amp driving the reverb went band and/or something further up stream near the input.
Should I move my question to The Newcomer's Forum?

Enzo

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Re: The Dangers of Speaker Impedance Mismatching
« Reply #4 on: December 10, 2019, 01:15:39 AM »
This section is fine, we'll see it either place.

Well, pick one amp at a time to fix, we can't discuss a couple at once, it gets all convoluted.

Reverb:  It is either the drive section, the return section, or the pan itself and its wiring.

 

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