Impedance matching

MissionBrown
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Re: Impedance matching

Postby MissionBrown » Thu Apr 07, 2011 2:13 pm

Mr. Bill wrote:If the magnet got hot, I'd investigate the possibility that the amp is going into high frequency oscillation. If the output wires are too close to an input line, etc. the amp can start to oscillate at frequencies too high to hear, but not too high for the amp to reproduce. This could also cause the distortion that you are getting.



No problem with the distortion anymore since I've fixed the mic lead, but I'll investigate your other suggestion.
There was something unusual going on, but it'll tale a while to pin down.
Unfortunately I can't test this stuff when my family is home.
For some reason my dear lady doesn't enjoy the experimental process.
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MissionBrown
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Re: Impedance matching

Postby MissionBrown » Thu Apr 07, 2011 6:16 pm

Mr. Bill wrote:Olrockandroller's suggestion of adding a 16 ohm resistor will fix the problem if it is being generated by the mismatched load, and by way of heat, it will also reduce the overall volume of internal isolation speaker as well.



So I can just string two 10 watt 8ohm resistors in series to make up the 16 ohm parralell dummy load and all will be well?

10 watts are the largest that I have available near me.
Will that be ok for heat dissipation along with the speaker?
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MissionBrown
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Re: Impedance matching

Postby MissionBrown » Sun Apr 10, 2011 4:10 pm

I made a simple resistive load to run in parallel with my 16 ohm cab, as suggested earlier in the thread.

It works. To a degree.
As predicted, the amp was quieter due to 50% of the load going via two eight ohm resistors in series (I couldn't source a 16 ohm).

The unfortunate side effect is that the frequency response is drastically altered.
Upper mid and upper upper frequencies are definitely attenuated.
For country it's not so bad a tone, and on my Surfcaster with a p90 ibn the bridge, it actually sounds decent (that guitar is hard to get sounding the way I like).

With the Mosrite though, it just sounds all wrong.
So far I've only run it with my Epiphone 5 watt head via the 8 ohm tap, but I imagine that the result will be fairly similar on the Princeton Reverb. But then, that amp does have some EQ to boost the bass and treble, so I may have a bit more luck.

Has anyone here tried the Weber Z-Matcher?
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MissionBrown
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Re: Impedance matching

Postby MissionBrown » Sun Apr 10, 2011 6:01 pm

I've ordered a Z matcher.
Now to wait a couple of weeks before I get it in the post.

Seems like a really handy device, it was either this or replace my 12" speaker, which I didn't want to do because I like the sound.
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olrocknroller
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Re: Impedance matching

Postby olrocknroller » Mon Apr 11, 2011 5:44 pm

MissionBrown wrote:I've ordered a Z matcher.
Now to wait a couple of weeks before I get it in the post.

Seems like a really handy device, it was either this or replace my 12" speaker, which I didn't want to do because I like the sound.



Experimentation can be a lot of fun, so long as things don't start smoking terminally...I made the mistake of buying a Fender DSP 212 amp, and intensely dislike ALL of the amp models, so am going to explore to see if I can bypass that module. I'm willing to bet it's all one ugly printed circuit board, and good luck isolating anything!
Olrocknroller

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Re: Impedance matching

Postby MissionBrown » Tue Apr 12, 2011 4:40 pm

olrocknroller wrote:
MissionBrown wrote:I've ordered a Z matcher.
Now to wait a couple of weeks before I get it in the post.

Seems like a really handy device, it was either this or replace my 12" speaker, which I didn't want to do because I like the sound.



Experimentation can be a lot of fun, so long as things don't start smoking terminally...I made the mistake of buying a Fender DSP 212 amp, and intensely dislike ALL of the amp models, so am going to explore to see if I can bypass that module. I'm willing to bet it's all one ugly printed circuit board, and good luck isolating anything!


I'm betting that there is a lot of SMD circuitry in there too.
What I don't get is Fender's Vintage Modified series.
Classic amps with DSP is a recipe for market disaster.


Anyway I tried the resistive load on my Princeton, and it worked ok. But in this case, the bottom end was missing. The 10" of the Princeton shook the room more than the 12" did.
It's going to be about a month before the Z matched gets here, so I'll probably just stick with the 5 watt amp in use with my iso cab. The tone is quite good after all, even though it lacks reverb.
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MissionBrown
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Re: Impedance matching

Postby MissionBrown » Sun May 08, 2011 4:39 pm

The Z Matched has passed through customs. Am waiting for delivery.
Hopefully it comes in the post today so I can try it out tonight!
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Re: Impedance matching

Postby dubtrub » Sun May 08, 2011 6:25 pm

Your posts delivers on a Sunday? :o

Ours take Sunday's and every holiday known to man and will even take a day off if the cat has diarrhea.

BTW, Good luck on your project!
Danny Ellison

MissionBrown
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Re: Impedance matching

Postby MissionBrown » Sun May 08, 2011 7:29 pm

Its Monday here in the future :)
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MissionBrown
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Re: Impedance matching

Postby MissionBrown » Tue May 10, 2011 5:21 pm

Finally turned up this morning, a solidly built unit, quite heavy.
Wont get any time to play until the weekend at the soonest, maybe Monday night even!

I'd forgotten that the unit had a line out, something I'm keen to try as I love going DI :)
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