What to do with extra transformers I have?

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matttornado

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I have an extra 100 watt Power and 100 watt Output transformer for a Marshall Plexi / 800. If I use them for an amp build, does it have to be 100 watts? Can I use 100 watt trannys for a 50 watt or 40 watt build? What are my options? I already have a 100 watt 2203 clone.

Thanks!
 
You can use the 100W OT for a 50W build but the primary impedances will be off by a factor of two. That means on the secondary your 16 ohm output shifts to the 8 ohm and the 8 ohm shifts to the 4 ohm output. You just won’t have 4 ohm capability.
 
You can use the 100W OT for a 50W build but the primary impedances will be off by a factor of two. That means on the secondary your 16 ohm output shifts to the 8 ohm and the 8 ohm shifts to the 4 ohm output. You just won’t have 4 ohm capability.
If you built a 50 watter using the 100 Watt Ouput Transformer your 50 watter would hit with the low end and dynamic punch of a 100 watter which would be pretty cool IMHO. When I pull two tubes out of my 100 plexi it still hits harder and punches bigger than my actual 50 watt Marshall so the theory actually works.

Essentially wired as GLPG80 layed out it would be like having a 100 watt amp and pulling two tubes out of it and when you do this you have halve your impedance in the 100 watter, so if driving a 16 ohm load you set the amp to the 8 ohm tap. If driving an 8 ohm load the amp is set tot he 4 ohm tap.

Mojave used to build their Scorpion 50 watt amp with a 100 watt Output transformer for this very reason....so it hit like the 100 watt Peacemaker. You can read about it here:

https://legendarytones.com/mojave-ampworks-scorpion/
1740244570570.jpeg
 
I have an extra 100 watt Power and 100 watt Output transformer for a Marshall Plexi / 800. If I use them for an amp build, does it have to be 100 watts? Can I use 100 watt trannys for a 50 watt or 40 watt build? What are my options? I already have a 100 watt 2203 clone.

Thanks!
The info posted above is incorrect. The correct info is that the 4 ohm tap will now become 8 ohm and the 8 ohm tap will now become 16 ohm. The 16 ohm will be 32 ohm but probably not be used because in practice 32 ohm speaker loads are typicall not used. These videos may help with the concept.
 
You are 100% correct the 16ohm transformer tap would not be used if he wants to use the 100 watt output transformer in a 50 watt amp which coincides with the practice of dropping the impedance by half if you pull two power tubes out of a 100 watt amp with the OPT x-former wired as a 100 watt amp.

16 ohm load = 8 ohm impedance tap
8 ohm load = 4 ohm impedance tap
 
You are 100% correct the 16ohm transformer tap would not be used if he wants to use the 100 watt output transformer in a 50 watt amp which coincides with the practice of dropping the impedance by half if you pull two power tubes out of a 100 watt amp with the OPT x-former wired as a 100 watt amp.

16 ohm load = 8 ohm impedance tap
8 ohm load = 4 ohm impedance tap
4 ohm tap becomes 8 ohm, 8 ohm becomes 16 ohm, and 16 ohm becomes 32
 
4 ohm tap becomes 8 ohm, 8 ohm becomes 16 ohm, and 16 ohm becomes 32
:2thumbsup:
That's exactly what I said. He would not use the 16 ohm transformer tap and that tap from the transformer would not be connected at all. The 8 ohm tap would become the new 16 ohm tap for a 16 ohm load and the 4 ohm tap would be the new 8 ohm tap for an 8 ohm load.

He probably should hardwire the jacks as 16 and 8 ohm only to avoid any issues.
 
:2thumbsup:
That's exactly what I said. He would not use the 16 ohm transformer tap at all. The 8 ohm tap would become the new 16 ohm tap for a 16 ohm load and the 4 ohm tap would be the new 8 ohm tap for an 8 ohm load.

He probably should hardwire the jacks as 16 and 8 ohm only to avoid any issues.
Actually, what you’re saying now is correct but what you posted in the past was incorrect go ahead and read what you posted. I think you’ll see the error.
 
Actually, what you’re saying now is correct but what you posted in the past was incorrect go ahead and read what you posted. I think you’ll see the error.
:2thumbsup:
That's exactly what I said. He would not use the 16 ohm transformer tap and that tap from the transformer would not be connected at all. The 8 ohm tap would become the new 16 ohm tap for a 16 ohm load and the 4 ohm tap would be the new 8 ohm tap for an 8 ohm load.

He probably should hardwire the jacks as 16 and 8 ohm only to avoid any issues.
My mistake it wasn’t you who gave the wrong information it was somebody else you’ll see it up there
 
Actually, what you’re saying now is correct but what you posted in the past was incorrect go ahead and read what you posted. I think you’ll see the error.
I was explaining that wiring the Output transformer in this manner is exactly like when you pull two power tubes in a 100 watt amp that has 16 ohm 8 ohm and 4 ohm taps.

I assumed he would know that the 16 ohm transformer tap of a 100 watt output transformer wired for 50 watts would not be connected to anything so I didn't go into great detail but your posts expounded on it further and explained all the details that I didn't touch on. Thanks for clarifying things if he so decides to go this route:2thumbsup:
 
Ok, so I can use the 100 watt output tranny. Got it. What about the power tranny? just wire it up like 100 watt?
 
The info posted above is incorrect. The correct info is that the 4 ohm tap will now become 8 ohm and the 8 ohm tap will now become 16 ohm. The 16 ohm will be 32 ohm but probably not be used because in practice 32 ohm speaker loads are typicall not used. These videos may help with the concept.


What I posted is not wrong, I view it from the perspective of the load not the source. You half the impedance to the load to reflect a doubling of the primary impedance. The reason you do this is for what you mention above - the 8 became the 16 and the 4 became the 8. There is no 2 ohm and no 32 ohm.

Before you go bashing someone make sure you understand yourself what you’re saying.
 
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