How do i dummy load the 5150? (impulses)

[kev]

I made a dummy load box – cost about $30 or so, works great.
Add another $30 if you need a DI box – Behringer Ultra G is good enough.

Power resistor, aluminum body, 8 ohms, 200 watts, w/leads. $15
http://amptechtools.com/truload.htm

Input jack - $2 - $4
http://www.allparts.com/store/electronics-jacks-ep-0055-002,Product.asp

Unfinished wooden box with hinge @ any craft store $8 - $10.
http://www.dickblick.com/zz604/10/

2 x bits of wire about 2” each, solder, flux, $0


1) Drill a hole in the back or side of the wooden box for the input jack.
Test install the input jack to make sure it fits (I had to scrape the inside box a bit – box was too thick).
Remove jack to make soldering easier.
2) Solder wires to power resistor leads.
3) Solder wires to input jack – gender neutral, doesn’t matter which goes where.
Check connection with Multimeter if you suck at soldering like me.
4) Install input jack in wooden box hole.
5) I attached the resistor to the bottom of the box with Velcro so it won’t slide around.

** Note: the resistor gets pretty hot, so make sure the wooden box doesn’t catch fire or melt the Velcro.
Ideally, you should cut a piece of aluminum sheeting, glue to the bottom of the box and glue the resistor to the aluminum sheet with thermal glue.


Connect amp’s speaker/cabinet-out to DI in – with speaker cables.
Connect DI’s cabinet-out to load box – with speaker cables.
Connect DI’s output-to-mixer to ….a mixer or your PC/Mac.

AWESOME! I'll see if i can find some similar stuff in the UK. It sounds like great fun

 

[Torsis]

Yeah, real easy to make - EtherForBreakfast told me how to do it.
Just make sure you get a power resistor with the ohmage your amp/cab is at.

When I plugged my '82 JCM800 in, I was thinking ...Hmmm this might not be a good idea afterall...
I was waiting for something to blow up, but everything was fine.

Pretty cool turning up the master vol to 8 at 2am, though.

 

[AdamWathan]

I think the connection explanation for that load box is wrong.

Connecting the speaker out to a DI? You don't want a powered signal going through there, that should completely fry the DI shouldn't it? What you want to do is connect the speaker out with a speaker cable directly to the load box and run the FX send to the DI...

 

[Torsis]

Yeah, that would work, too - probably depends on the DI.
The Ultra G can handle it - basically it runs in-line between the amp & cab (load box in this case) then has an XLR out to the board.

As part of the Ultra G specs: Direct connection of amplifier outputs with ratings of up to 3,000 Watts.

 

[kass]

With a non-master volume amp like a 5150,

har har

 

[Metaltastic]

...what?

 

[reneisgod]

Ok maybe i haven't read this properly and now im wondering why no one else has said this yet,

all your wanting is to play the head without the cab using impulses?

use the FX send man?

Thats what i use you don't even have to plug the cab in.
Just straight into the head and FX send into my sound card.

Whats all this dummy load nonsense all about when the amp has FX send
and why the hell would you need your cab connected if your head has FX send

seriously confused to what your all going on about fx send end of story

 

[slashvanyoung]

why the hell would you need your cab connected if your head has FX send

Maybe, just maybe, he doesn't want to fry his head?

Because running a tube amp without a load is not the very best thing you can do to it.

 

[kev]

Ive been trying to find a power resistor like that in the UK but im having problems so far

 

[reneisgod]

Maybe, just maybe, he doesn't want to fry his head?

Because running a tube amp without a load is not the very best thing you can do to it.

just play the amp on stand-by works for me man.

 

[slashvanyoung]

@ kev: Have you tried eBay? Maybe you can get a good ol' Marshall Power Brake for little money?

@ reneisgod: I thought you don't get a signal if the amp is on standby?? Maybe that's different between 5150 and 6505. Great, now I'm confused too...

 

[kev]

@ kev: Have you tried eBay? Maybe you can get a good ol' Marshall Power Brake for little money?

@ reneisgod: I thought you don't get a signal if the amp is on standby?? Maybe that's different between 5150 and 6505. Great, now I'm confused too...

defo no signal on standby on either amp unfortunately mate, they use the same circuit! I cant really afford to stretch to the power brakes/ hotplates as im a student and a tight arse lol... Ive found a couple of companies that i may email about it as im hoping to get the job done as cheaply and as cheerfully as possible I might just see how bad the postage is on that link from toxic actually.

 

[Torsis]

Kev -
That link was the first one I found with a picture of a power resistor

I bought mine at Parts Express - and based on the picture & price (about $15 bucks), I bought the 100w one.
They ship internationally.

http://www.partsexpress.com/webpage.cfm?&Webpage_ID=3&CAT_ID=41&ObjectGroup_ID=340&SO=2

 

[kev]

yeh i spotted that one too on my searches! Ive been searching for an hour now lol. The shipping from partsexpress outweighs the cost of the item, and ive also got to spend $50 to qualify (might take it up if i cant find anything else thoguh). Im thinking about wiring a bunch of resistors up in series so it reaches the 120w mark. I havent a clue if Ohms need to match though as i havent studied them since technology 5 years ago at school!

What happens to the other 20w of the 5150?

 

[reneisgod]

so what kind of damage would a head sustain without a dummy load, isn't it a case of risking it, as in its not a case of gradual damage not using a dummy load its more a case of the possibility of your head being fried. Or is there other damage that can be done in the background with the head still running but say maybe an alter in tone or something?

 

[JBroll]

Remember the scene in Ferris Bueller's Day Off where they're trying to crank the engine in reverse to turn the mileage count back, and the dorky prick kicks the thing until the front wheels hit the ground and it drives through the back windows and into the trees below the house? Kinda like that, except remove the dorky prick, add four-wheel-drive, and replace the trees with fire and death and Bambi's mother getting shot.

Jeff

 

[Torsis]

As for damage to the head w/o a dummy load attached, I think it has something to do with the electrical energy/heat produced by the amp, with nowhere to go.
Obviously, it has to go somewhere, so it would take the path of least resistance and probably build up in the OT and/or short out or shorten the life of the amp components.

Jeff B's explaination is better, though.

I’ve heard/read countless times people saying you shouldn’t run a tube amp w/o speakers attached (or a dummy load), and never heard/read anyone say that’s bullshit and not necessary, so I take that at face value.
If it wasn’t a problem, why do amp techs have load boxes on their benches, particularly when they often just turn the amp on to check stuff for short periods of time?

 

[Metaltastic]

What I wonder is why it only seems to be that way with tube amps and not solid state...

 

[JBroll]

Solid state amps don't need as many obnoxious transformers. That's also a big reason why they're lighter and one of the biggest reasons why they're cheaper.

Jeff

 

[Emdprodukt]

had no problems ordering my tubecube from germany for less then 150 dollars... awesome stuff.

why don't you use a cab. at thomann there's a 1x12 harley benton for only 59,-€. don't think you can find any cheaper. if you want to record via send fx and with the dummy cable in the return fx, there's tone through the speaker though. if you don't want to go higher than "neighbour friendly" volume, you can hit the post gain knob at 4 max. but that should be enough. I'm doing it this way because all the cheap attenuators are to be ordered in the usa only ...

Here's the link: http://www.thomann.de/gb/harley_benton_g112.htm it's GBP 43.21 + 7.45 shipping