output transformer and related speakers ohm impendence

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

Moderators: CurtissRobin, colossal, zaphod_phil, Daviedawg, Graydon

Post Reply
User avatar
davemojo
Occasional poster
Occasional poster
Posts: 161
Joined: Wed 01/06/21 4:14 am
Location: Hoofddorp
Contact:

output transformer and related speakers ohm impendence

Post by davemojo »

Hi All,

Last week I have created my first post on this forum, I am new to amp building and I am new on 18watt Technical discussions.

Pardon me my ignorance but electronics is where I got my study done, but that was long long time ago. I had some TV repairs experience, once I built a radio but that was also 25 years ago hehehe was only 21 at that time so no experience on guitar amps.

I am building some sort of 18Watt Bluesbreaker using a custom built 2x 12" Combo Cabinet and putting 2x 12" Celestion G12M 25 W. I am not sure if that is going to be the definitive choice since the amp is going to be used with an Organ B3 clone a Crumar Mojo.

On previous post someone said:
"You can use any speakers you want as long as you correctly match the impedance."

What is going to determine on my 18Watt project build th ohm impendence for the speakers 4 8 or 16 ohms?

Is the output transformer, or the power transformer, or combination of both?

I bought the following transformers
power
https://www.tonefactory.nl/marshall-sty ... att-5v-tap
output
https://www.tonefactory.nl/marshall-sty ... er-18-watt

Now for what I can read on some short specs at Tonefactory
Secondary Impendence: 4-8-16 ohm

So to my understanding once I connect the output transformer the power transformer and fully complete the circuit build I can put any speakers with 4-8-16 ohm impendence is that correct?

Thanks
0 x
Davide Violante
Rockers&Rocks
www.rockers.rocks

User avatar
Bieworm
Verbose Moderator
Verbose Moderator
Posts: 2287
Joined: Mon 02/10/20 8:24 am
Location: Belgium

Re: output transformer and related speakers ohm impendence

Post by Bieworm »

You wire the OT for the 3 different impedances with a rotary switch. Then you can choose the impedance position which matches your speaker arrangement. When you take 2 dedicated transformers for 18Watt type amp you can't go wrong, no matter what brand. They are all fine.
2 x
"THIS should be played at high volume..preferably in a residential area"

Post Reply