Can You Damage a 1 Watt Amp Mismatching Speaker Impedance?

Clockworkmike said:
Yep thats one of those genie boxes that unlocks the power of beating a bad mismatch! Very cool they came up with these. I thought about getting one of these or the Radial Cab Link to run the Marshall Mode Four into its 2 400w cabinets safely ( currently it can only safely run one MF400 cab at its full 350w power at 8ohms, a single 280w 16ohm cab at 245w or a full stack at 350w into 2 280w cabs at 16ohms each)
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I think RVA has one too!
 
Cadorman said:
View attachment 72283
Here's the situation. I have 2 16 ohm cabs that I want to run off my DSL1HR. The head only has a single 16 ohm output jack. I can daisy chain the pine cab through the OR112. Will running this puny thing with a 12AU7 power tube damage the output transformer at 8 ohms instead of 16 ohms? I'm probably stupid enough to try it, but figured I'd see if anyone that stayed at a Holiday Inn Express last night knew.
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It doubles the current (if current is still available) so it's not a good idea.
If there is not enough current to double, it will at least increase up to the limit of available that it has.
So that is cooking the output tube and making the OT winding hotter than intended.
(that's why it's labeled 16 ohms, they aren't kidding...)

You have to get a 16 ohm 4X12 black flag cab, instead.

Or use one of those impedance adapter thingies instead....

The ideal thingie is a Atlas/ Soundolier model AF 140 auto transformer.
This thingie changes impedance like nobody's business.
It has all sorts of wires and converters and stuff to hook 8 ohm loads or 4 ohm or 2 ohm to a 16 ohm amp.
You can go ohms hog wild young man...
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So the white wire actually has a connector on it. I pulled the orange off and connected the white. I'm going to try it.
 
So, that was basically 45 minutes of playing at full volume on the red channel with 3/4 of the gain. Sounded great. Nothing happened and the output transformer is barely warm to the touch. Far cooler than the power trans which isn't very warm either. This was running into the OR112 with a Vintage 30 16 ohm jumpered to my pine 212 with a pair of 8 ohm Greenbacks in series. The output cable from the amp was reading 7.0 ohms. I'm going to order that switch.
 
Cadorman said:
View attachment 72283
Here's the situation. I have 2 16 ohm cabs that I want to run off my DSL1HR. The head only has a single 16 ohm output jack. I can daisy chain the pine cab through the OR112. Will running this puny thing with a 12AU7 power tube damage the output transformer at 8 ohms instead of 16 ohms? I'm probably stupid enough to try it, but figured I'd see if anyone that stayed at a Holiday Inn Express last night knew.
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The DSL1HR schematic (finally) shows a second tap on the OT secondary.
This tap is labeled "8 ohms" on the schematic.
So it seems that this may be your lucky day after all.
But a way of testing it is to measure the plate current, and check to see if the current is normal.
If the current is excessive, there is probably a mismatch...


Screenshot 2021-08-20 at 09-53-34 No Title - DSL1-60-02-v02 pdf.png
 
Cadorman said:
So, that was basically 45 minutes of playing at full volume on the red channel with 3/4 of the gain. Sounded great. Nothing happened and the output transformer is barely warm to the touch. Far cooler than the power trans which isn't very warm either. This was running into the OR112 with a Vintage 30 16 ohm jumpered to my pine 212 with a pair of 8 ohm Greenbacks in series. The output cable from the amp was reading 7.0 ohms. I'm going to order that switch.
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It turned out OK but be careful about impedance cause the transformer can fry.
 
Amp Mad Scientist said:
The DSL1HR schematic (finally) shows a second tap on the OT secondary.
This tap is labeled "8 ohms" on the schematic.
So it seems that this may be your lucky day after all.
But a way of testing it is to measure the plate current, and check to see if the current is normal.
If the current is excessive, there is probably a mismatch...


View attachment 72332
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How come this schematic does not match up with the actual circuit card component labeling? Just look at the resistor, Jack, and connections numbers on the output side of the tranny. :unsure:
 
Cadorman said:
View attachment 72290
Here's where the black and orange wire connect. There doesn't appear to be a trace connecting R110 to R107 or R108 on the top side. So, you have the output jack, 3 resistors and the 1 watt/.1 watt switch. This is a two sided board.
View attachment 72291
Here's the back. I don't see traces for the orange wire on either side. In this pic the orange wire is the two solder lugs top left going nowhere. The black wire ties into the R108 resistor with traces going to R110 and the switch. All 3 of the bottom lugs are tied together and go to the switch. I guess I don't care about all that. I just want to figure out what that white wire is for.
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Just an observation, the OT connections of the orange and black wires seems backwards to me. In all my years in the electronics field, including many designs, I never saw or used black wire as the hot connection (the orange wire is connected to the ground plane on the circuit card). It’s not an issue in this case, but if you install a switch you need to make sure you are switching and 8 and 16 leads. I’ll go open mine up later on and see if it has the orange to ground and the black hot. In my OCD I’d connect the black to ground.
 
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