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Tesoro Volume Pot Question...

Diggler

Diggler

Member
I am in the process of installing a volume knob on a Silver Sabre uMax. The older uMax Tesoro's are super loud and the tone is ear splitting. I am tired of using the tape over the speaker method and okay with voiding the warranty. I tried installing some pots I had laying around (50K and 100K) with various resistors but it was basically like installing an on off switch. I am putting the pot inline with the positive speaker terminal wire. I ordered a 1K linear taper that will arrive in a couple days. Should I expect better results with this pot and am I installing it in the correct location? The speaker is 16ohm and .2w IIRC. Before I drill a new hole in the faceplate, I would like to make sure I am on the right track.
Thanks, Ron
 
with a 16 ohm speaker, putting a 16 ohm resistor in series will cut the power to the speaker by half. A 1K pot is still probably going to act much like a switch. I think you want something in the 100 ohms or less range; I'd probably start with a 50 ohm pot and see what it acted like. Or I'd grab a couple resistors and try them to see how it changed the speaker output. If I had a 4.7 or 5.2 ohm and a 10 ohm, I'd try those and see how much those reduced the volume, then extrapolate those tests to pick a suitable potentiometer.
 
Thanks for the reply. I was able to cancel the order before it shipped. Ordered a 50ohm so will let you know how it goes when I get it installed. Was just supposed to be a quick, spur of the moment mod. Now detector will sit a week on the bench and cost me $12 and may not work. Ha! Thanks again, Ron
 
Tesoro designed the audio amp circuit to use the 16 ohm speakers.
Find the right audio taper pot that will work. Linear taper will also work.
 
Bad news is the part was back ordered until June. Good news is I swapped the 50ohm out for a 25ohm that should work even better. Fingers crossed for closing the uMax up this weekend.
 
I received the 25ohm that was supposed to have identical dimensions as the 50ohm that was back-ordered. It is larger and will not fit in the housing but gave it a try anyway. It smoothly cuts the volume from off to about half of original. Was hoping to go from zero to full blast. Had no idea it would be so difficult to order the correct part.
 
Could you not just use a set of headphones with a volume control on them ?? that would sort the problem out would it not.
 
Sometimes, more and more theses days, I just don't want to use headphones. Used a duct tape flap as volume control for years but sure would be nice to have a knob. I use Killer B Stinger's in the summer and Gray Ghost's in the winter but there are times when I just want to use the speaker, just not blaring loud like the older Tesoro's do. I often reach for another machine because of the LOUD speaker on the Silver Sabre uMax.
 
Reading specification sheets for components can be tedious and at times frustrating. It is easy to get something that is not exactly what you thought you picked from the specifications.

The 25 Ohm potentiometer at least verified you are in the general range and not off by an order of magnitude.

I think I would wire it up like the diagram and see if that works for you. At full volume it will put a slightly higher load on the amplifier than just the 16 Ohm speaker by it self. As the volume gets turned down, the load on the amplifier will approach the 25 ohms of the pot. Even at full volume setting on the pot it should be a little less loud that in original configuration.

Wired like shown should let you turn the speaker all the way down.

The wires that were originally on the speaker would go to the two ends of the pot. The speaker would go between the pot wiper and one end of the pot. Swap the speaker wire from one end of the pot to the other to change which way the pot turns to decrease the sound.
 
Thanks Sven, will try that circuit next. TVR, tried that with 25 ohm and still not much control. Will try Sven's wiring with the 25 and see what happens...
 
Tried Sven's circuit in both directions with 25ohm and volume went from full to about half. Vito, I will get a 1K and give it a spin as well. Someone else suggested 100ohm... I guess it will remain on the operating table until I get lucky. Been using other machines while it's down but always wanted to have control of the volume on this sucker. It is usually my loaner to newbies and I get a little embarrassed hearing them search for signals from across the park. Beats letting them sweat up a pair of my headphones in the Texas heat though! Thanks again for all of the replies.
 
Hi Diggler,
just want to mention that a positive logarithmic potentiometer will work best for this.
--> http://en.wikipedia.org/wiki/Potentiometer#Audio_control
Any linear will do it, too, but your "hearing" will FEEL different as you know it from the volume-control
of your stereo.
 
I had same issues and found I could use a seperate jumper wire from both outter posts on the pot being soldered into play.
 
finnfoto said:
I had same issues and found I could use a seperate jumper wire from both outter posts on the pot being soldered into play.
Click to expand...

Positive to both outer posts and negative to center post or no negative at all?

Vito, I have a few of those pots coming from China. Free shipping so could be a while hah!

Thanks again to all, Ron
 
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