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Load Box/Line Out - 300W~16 ohm 
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clipless

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Where the green crosses the green - is that a connection?
It doesn't look right to me, not that I am a wiring whiz.

I really don't know - but will be interested in an answer from someone who knows more then me.


Mon Dec 12, 2016 7:37 pm
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I think 112.5w. But let me ask someone and I'll get back to you.


Mon Dec 12, 2016 8:21 pm
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clipless

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Ok - had to do some reading, and it is a bit confusing to me, but here is my take.

I think you have the resistance calculated correctly.

The power dissipated by the two 30 ohm in parallel is max 300 watts. Putting them in series with the 16 ohm resister knocks it back down to 150 watts.

The 33 ohm resistor in parallel with that circuit gets you back up to 300 watt total max dissipation.

All that said,
1.) I don't know if I would trust myself and my amp with those calcs
and
2.) A load box of just pure resistance affects an am much differently than a true reactive speaker-type load - you may not like the results. I guess it may depend where you are pulling your signal from, but in general it will kill your highs, and take a lot of dynamics out of the amp.

Again, only my 2¢ - there are a lot of people here who know much more than me.


Mon Dec 12, 2016 8:21 pm
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From the top, if the 2nd and 3rd are in parallel then they sum to 75w. And if those are in series with the bottom one then that sums to 225w, and if all of that is in parallel to the top one then that makes 187.5w in total. So maybe that's the answer... this is a good exercise.


Mon Dec 12, 2016 8:32 pm
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mamberg wrote:
Ok - had to do some reading, and it is a bit confusing to me, but here is my take.

I think you have the resistance calculated correctly.

The power dissipated by the two 30 ohm in parallel is max 300 watts. Putting them in series with the 16 ohm resister knocks it back down to 150 watts.

The 33 ohm resistor in parallel with that circuit gets you back up to 300 watt total max dissipation.

All that said,
1.) I don't know if I would trust myself and my amp with those calcs
and
2.) A load box of just pure resistance affects an am much differently than a true reactive speaker-type load - you may not like the results. I guess it may depend where you are pulling your signal from, but in general it will kill your highs, and take a lot of dynamics out of the amp.

Again, only my 2¢ - there are a lot of people here who know much more than me.


parallel knocks the number down, series adds them up.


You got it backwards, no wonder you voted the way you did. It's not your fault ;)


Mon Dec 12, 2016 8:36 pm
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clipless

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My reading told me in series, there is only one path through them, so each had to handle the full power - there is no gain. In parallel, there are two paths - so the power handling doubled.

In a speaker cabinet though, if you have two 150 watt speakers, it doesn't matter which way you wire them (series or parallel), you still have a 300 watt cab.

Will be watching for the definitive answer.......


Mon Dec 12, 2016 8:37 pm
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clipless

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mortatone wrote:
parallel knocks the number down, series adds them up.


That's for resistance though, not power handling.


Mon Dec 12, 2016 8:39 pm
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ah you're right!

So maybe I voted backwards :D


Mon Dec 12, 2016 8:41 pm
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perhaps the 30, 30 and 16 will sum to 150W, and in parallel with teh top one at 150w alone will sum to a total of 300w...


Mon Dec 12, 2016 8:59 pm
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GABmiral
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I'm going with mam's theory on this one - if you put things in parallel, they share equal access to the current path.

What I'm wondering is why not use 4 16-ohm resistors in series-parallel (or parallel-series) and call it good? :idk:

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Mon Dec 12, 2016 9:28 pm
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What are you trying to achieve by using different values?


Tue Dec 13, 2016 3:35 am
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Mamberg was right. 300w.


Maybe you need a bigger heat sink? Or a fan? I haven't messed around with dummy loads at all...


Tue Dec 13, 2016 8:05 am
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I think you might be trying to get less heat by doing it the long way. There are calculations for power, resistance and how big of a heat sink you need. The single 16 ohm resistor will work just fine but you just need to deal with the heat. What are the specs on your heat sink?


Tue Dec 13, 2016 9:33 am
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Does the fan motor produces resistance as well?

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Tue Dec 13, 2016 9:38 am
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clipless

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ok - I was a bit scared to click that mancrates link - but that is some cool stuff!!

think I will be picking up the whiskey crate for my boss.........


Thu Dec 15, 2016 7:51 am
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There are some real, Mad Scientists out there! Cool shit!!! :thu:

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Walt wrote:
But when the hour is nigh, and the lights are low, and I got a little toothpick of a shwag joint in my teeth, and my friends want to hear me play "Into the Void", or "TNT", "or "Cemetery Gates"...I plug my 600 dollar guitar into my 150 dollar amp, and I am a Rawk gawd.


Mon Dec 19, 2016 2:21 pm
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Hi.
First post n all. I build tube amps for a living.
What caught my eye was your sketch of your,what i suppose,output transformer and surrounding components.
Are you running that setup together with the powertubes? Ie;does the components of your line out see DC voltage,or what gives?

In turn,have to ask,why all this bother instead of a powerscaling setup or a well designed PPIMV? If the point of the excercise is to be able to let the amp breathe,only.

FWIW any line out setup often benefits from an elevated ground. Ie; a resistor of minor value between chassis ground,if active chassis,and output.

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Mon Feb 20, 2017 2:41 am
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Ah!
Now i get it...That entire setup is within your load box. For a sec there i thought the transformer was you active OT....Sry.

Much better than a PPIMV..yeah well,opinions vary. PPIMV´s as well as powerscaling setups can be very very versatile IMO. But granted,i keep an attenuator at the shop too. A TAD one..works,what can i say,and is a valuable tool when diagnosing some amps. No argument there.

Then again. Have to say that i have a hard time understanding running a 100w amp balls to the wall for a whisper at the other end. But that´s just me i guess.

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Tue Feb 21, 2017 4:09 pm
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