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Discussion Starter #1
Hey everyone,

I've been googling for days trying to find tutorials on building amps with switchable output impedance, however I feel like I am either searching for the wrong thing, or that there are no tutorials online for that... Does anyone know of any kits or tutorials that achieve this? I'm going for something similar to what I've seen from demo videos of some Welborne Labs stuff on YouTube.

Any thoughts, insight, anything is greatly appreciated!

Cheers!
 

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Hey Skipper,

If you get a transformer with 4, 8 & 16 ohm taps, you can wire them out to individual jacks or to a selector switch to vary the output impedance to suit your cabinets.

Is this what you are referring to or something more in-depth?
 

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Isn't it as simple as using a multi-tap output transformer wired to a 3-way switch?

*EDIT*
If you get a transformer with 4, 8 & 16 ohm taps, you can wire them out to individual jacks or to a selector switch to vary the output impedance to suit your cabinets.
BAH... Beat me to it by seconds!
 

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Info copied from the Welborne Labs site is in red....

Are you looking for something like "TB1", etc ?

The parts list shows them as being " turret terminal strip(s)"

TB1 10 turret terminal strip ____
TB2 10 turret terminal strip ____
TB3 5 turret terminal strip ____
TB4 10 turret terminal strip


Here are some pics of these....
turret terminal strip - Google Search

Here is a pic of a sample...



You now must decide which tap of the output transformer T2 you will be using (2, 4, 8 or 16 ohms). This decision is best made based upon the impedance of the speakers you will be using. Refer to the table below for the output transformer coding. The output impedances are selected by interconnecting the eight color coded secondary leads as shown below. Figure 3 depicts the connection for 8 ohms, however the terminals of TB1 can be used for connecting any of the configurations below. If you decide to shorten the output leads of the transformer T2, the red enamel coating on the wires must be removed before soldering to the terminals. This can be easily done by scraping with a razor blade.

Join the leads by soldering them to the terminals of TB1. Secondary wire color code: BW - Black w/White Letters GR - Green BK - Black BL - Blue CL - Clear Y - Yellow WH - White R - Red

upload_2017-9-17_8-56-36.png


Was this any help? Others with more knowledge and experience will hopefully see this and post a response.

Those Welborne Lab amps look amazing!!
Welborne Labs
 

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Go on the Trinity Amps forums and look at some of the schematics and layouts for their amps (usually the top post in each sub forum for each amp type), though I think (based on my Triwatt build) they usually use 2 jacks not 3. Might get you most of the way there.
 

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Discussion Starter #12
Wow, I wrote this and totally checked out! Sorry guys! Thanks for all the replies! Things have been really busy for me lately as I'm getting ready to launch a website for those extension cabs and (eventually) amplifiers that I'm going to start building!

@greco, that's amazing! Those totally would work well for what I'm going after.

@dcole, I'm definitely looking for some more "in depth" discussion/instruction. Although, I suppose I probably should just look into purchasing a kit to build so that I can learn hands on.
 
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