Wirewound Resistors Dummy Load question

[Pryde]

didn't want the thread to spin out of control but anyway I thank everyone for their input on helping me get a dummy load unit worked out. I don't plan on maxing anything out for any reason so I think my 8 ohm/240 watt, or 4 ohm/480 watt setup will suffice. I will of course keep an eye out for smoke (as always).

On another note I got an email from a local electronics professor my wife works with who said he has a 40 Mhz, 2 channel, analog oscilloscope, signal generator, and a variac that is mine for the taking

[Enzo]

There you go, can;t beat that.

[bsco]

Hey guy...That's a wicked deal.....Free is always good...

[Sowhat]

Hey SoWhat....nice picture......I will soon have to assemble one of these. I have to ask you...Is your wooden jig adjustable so the ends can be moved in or out to acomodate different sizes of chassis, or is it fixed???

It's adjustable, the uprights just slide in the track, it can take anything up to a 40" chassis although I have never had one that big. I have toyed around with making the tops pivot to adjust the angle but it has been so busy that I have not had time to fiddle around with the design.

[bsco]

It's adjustable, the uprights just slide in the track, it can take anything up to a 40" chassis although I have never had one that big. I have toyed around with making the tops pivot to adjust the angle but it has been so busy that I have not had time to fiddle around with the design.

Good job man!! I will have to make myself something soon...It is getting annoying blocking up a chassis with a bunch of pieces of 2x6's....what you have there is ideal....

[soundguruman]

Hilarious, Enzo asks you about your inductance statements and you start rambling about wattage and power.
And you have it completely backwards, VA is apparent power and takes power factor into account. Measuring watts is measuring watts. We don't measure VA.

I'm going to answer this:

1. It's not yammering. Power factor is very important when you calculate an accurate wattage.
Except that, ALL techs in this industry IGNORE the actual power factor. Therefore, your measurement is inaccurate.

2. VA DOES NOT take power factor into account - you are WRONG. You are so, so, misinformed.

3. The manufacturers who make wire wound resistors DO NOT publish the specs of inductance.
Instead, the manufacturer HIDES this specification.

4. Just because I wanted a more accurate load, and took the time and trouble to do it, does not make me a target for your UNINFORMED attacks.

5. YOU ARE measuring VA. YOU are not measuring the actual wattage.
But you "assume" you are...you are "just calling" VA "wattage."

VA is not actual wattage.

[soundguruman]

There are laboratory measurements and then there are practical guitar amp measurements. A plain resistor has no reactive element, voltage and current track. This is fine for most purposes. What we are all yammering about is the reactive component of a speaker, mainly the inductance of the voice coil. Now we are talking about impedance - the AC version of resistance. Impedance is the sum total of the resistance and the reactances. The reactances come at a phase difference from the resistive. So curent peaks in the inductance at a different time from the peak in the resistance.


When we are talking tone, we see this being cared for in some attenuators, like the Weber Mass. BY adding some inductance and other tweaking, they make what would have been a plain resistor react more like a real speaker. Some folks find that desirable, but to others it doesn;t make so much difference. But tone is a subtle thing.

Now we get to our dummy load. A claim was made that non-inductive - well actually LESS inductive - resistors would be "better." I asked how large an effect would resistor inductance have, and the person who brought it up has no idea. I suspect it has minimal effect. But that person who had no idea what effect it might have still felt comfortable telling us all we should seek specific parts because of it.

" A plain resistor has no reactive element,"

You are wrong. But keep on pretending...

[The Dude]

Since you continue to argue this moot point: Albeit, there may be a very MINISCULE amount of inductance in a resistor (and I do mean MINISCULE). It is small enough to be irrelevant. I just tested my dummy load made up completely of wirewound resistors on a very accurate Sencore LC75. It showed NO inductance. As I said there has to be a miniscule amount via the fact that it is wirewound. However, it is SO negligible that it does not register. The manufacturers do not "hide" this spec, as you stated. They do not spec inductance because there is almost NONE there. But,......feel free to continue marching out of step.

[soundguruman]

Since you continue to argue this moot point: Albeit, there may be a very MINISCULE amount of inductance in a resistor (and I do mean MINISCULE). It is small enough to be irrelevant. I just tested my dummy load made up completely of wirewound resistors on a very accurate Sencore LC75. It showed NO inductance. As I said there has to be a miniscule amount via the fact that it is wirewound. However, it is SO negligible that it does not register. The manufacturers do not "hide" this spec, as you stated. They do not spec inductance because there is almost NONE there. But,......feel free to continue marching out of step.

You tested it with your Radio Shack VOM?
hahahahahahhahahhahahahahhahhahahhahahha!

Just because I wanted accuracy, does not make me your target.

Just because I question your assumptions, does not make me "out of step."

You can follow, like a mindless sheep, ALL you like....
As long as you agree with "popular opinion" that will make you safe, sound, and comfortable...

[The Dude]

Regularly Calibrated. Sencore factory is in my city. It's not me that's making unfounded assumptions based on no evidence.

[g1]

Tell me how you measure VA, then tell me how you measure watts, o wise one. Then tell me which is apparent power and which takes power factor into account.
That is 4 separate questions, please answer in order and try to focus, ie. don't try to change the topic.

Edit: (hint) http://whatis.techtarget.com/definition/volt-ampere-VA

[soundguruman]

[ATTACH=CONFIG]27394[/ATTACH]

Regularly Calibrated. Sencore factory is in my city. It's not me that's making unfounded assumptions based on no evidence.

And FYI:
ALL legitimate measurements are in fact, made with intentionally "non inductive" load resistor bank.

You prefer to use: "a toy." OK, that's fine.

[The Dude]

And FYI:
ALL legitimate measurements are in fact, made with intentionally "non inductive" load resistor bank.

You prefer to use: "a toy." OK, that's fine.

My "toy" is accurate +-2%/microhenry. That is quite accurate enough for any electronic work I'll do. This isn't a science program. It's a bunch of people working on audio amps. If you're not happy with 98% or better accuracy, good for you. You've successfully turned a thread about making a simple dummy load into a nonsensical argument about nothing and have yet to supply any numerical data to back up your "noise". Please show us the machine you used to prove your stance and give us actual data to back it up.

[Enzo]

Ah don't bother feeding the troll, Dude.

[Jazz P Bass]

Please show us the machine you used to prove your stance and give us actual data to back it up.