Che_Guitarra

Dummy plug?
« on: August 12, 2017, 06:55:46 AM »
I just bought a Peavey Classic 30 guitar amp for an absolute bargain. 

I want to try out a few different speakers I have laying around out of curiosity.  The stock speaker is rated at 16Ω, the alternative options I have are all 8Ω.  I've been through a bunch of websites in regards to this specific amp and they all say switching to 8Ω is OK - just put a dummy plug in the external speaker jack.   But they don't define what a dummy plug is.


Is it a solid conductive plug connecting tip to sleeve?  Or is it a non-conductive plug that pushes a non-shorting jack apart?  Or something else altogether?


Re: Dummy plug?
« Reply #1 on: August 12, 2017, 09:13:13 AM »
If it's like an ampeg b25 I think it should be non shorting.  Mine uses a trs (stereo) plug and none of the contacts have continuity.  Its so that I can use 8ohm cabs instead of 16ohms.

Do you have the schematic?  Manual?  Fyi peavey support is very helpful even to 2nd or 3Rd hand owners and gear from 40 years ago!

Alternatively you could just add a resistive load right?  To turn your 8 ohm speaker into 16 as 1 8ohm speaker and 1 8ohm resistor (double check that that's actually ok tho I'm just brainstorming without coffee)

Re: Dummy plug?
« Reply #2 on: August 12, 2017, 12:37:15 PM »
No on the resistor thing. A resistive load is different than an inductive load. ie..a Speaker coil. 

Re: Dummy plug?
« Reply #3 on: August 12, 2017, 12:41:26 PM »
Wire two 8's in series to get 16 ohms if you have two available

abbey road d enfer

Re: Dummy plug?
« Reply #4 on: August 12, 2017, 01:24:04 PM »
The schematic is explicit. The internal speaker is 16 ohm and connected to the 16 ohm secondary.
The external output jack is connected to the 8 ohm secondary; inserting a plug in the external spkr jack disconnects the internal loudspeaker. You don't need any dummy plug, whatever that means in the context.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
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Che_Guitarra

Re: Dummy plug?
« Reply #5 on: August 12, 2017, 08:02:06 PM »
The schematic is explicit. The internal speaker is 16 ohm and connected to the 16 ohm secondary.
The external output jack is connected to the 8 ohm secondary; inserting a plug in the external spkr jack disconnects the internal loudspeaker. You don't need any dummy plug, whatever that means in the context.

Thanks.  Had a long week and wasn't thinking straight last night.  Your post has put me in the right gear.

 I see the OT has a white (16Ω) and green (8Ω) tap in a molex connector (well, so it appears via a google image search).  When I get around to pulling the chassis i'll switch them around, maybe kill off the 16Ω tap.

JohnRoberts

Re: Dummy plug?
« Reply #6 on: August 13, 2017, 12:12:58 PM »
I'm not sure how stable the classic 30, but general advice about tube amps is to never operate them without a load, so when switching loads perhaps power down the amp.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...