Orange Crush 30R

[vonFrenchie]

So I am looking at getting an Orange Crush 30R. It's a nice size combo amp that pushes 35 watts max. I wanted to use it as a head every once and a while and it doesn't have a speaker out jack. Would it be safe to wire up a speaker out jack so I can hook it up to my cab. If I did this I would hook up a switch so I can turn the internal speaker on, off and turn on the output jack (3 way center off switch). I would simply cut the internal wires, solder them to a switch and solder the output jack to that switch also. Is this a wise idea and what level amperage switch would I need?

www.orangeamps.com/admin/downloads/Crush30R-Manual.pdf
www.orangeamps.com/products.asp?Action=View&ID=94

[vonFrenchie]

Oh yeah, my cabinet is filled with 212's Eminence Man-O-War's 8ohm speakers. It works in 4 ohm, stereo (8 ohm) and 16 ohm modes.

[newey]

So long as you match the impedance, you should have no problems in disconnecting the internal speaker and running your cab. In looking at the manual, it looks like the amp wants a 4Ω load- but double check that.

If so, and you run your cab at 4Ω, you're fine. Problems may arise, however, if you run both the internal and an external cab together. If the required load is 4Ω and you wire 2 4Ω speakers in parallel, you get 2 Ohms net and your amp won't be happy or survive long.

However, since your cabinet has other options, you can probably work it out for both speakers. (I assume that's what you were intending when you spoke of an On-Off-On switch.)

Solid state amps are more tolerant than tube amps of an impedance mismatch, at least on the high side. You could run a 4Ω SS amp with an 8Ω speaker. The power will be reduced somewhat.

But if it's a 4Ω you don't want to run any configuration which is less than that.

[vonFrenchie]

I knew that it would be unwise to run the internal speaker and the cabinet at the same time. I just didn't know whether or not it would be a good idea to futz with the innards of the amp itself. The sight of other Orange amps with 8ohm and 16ohm separate outputs spooked me a bit.

I am trying to sell my Peavey 400 because its too much power and I can't turn it up at all most days. Plus being in college leaves me without an amplifier on most days. I built the cab with my dad, so it would be a shame to let it sit, and even worse to sell it. I wired it so I could use as many amps as possible with it, I didn't want to get stuck with a 4 ohm or 16 ohm cabinet. It has three inputs and one on/on switch. Obviously its L input, Mono input and R input and a Ser/Par switch.

[newey]

I just didn't know whether or not it would be a good idea to futz with the innards of the amp itself.

Well, you're not really futzing with the innards, just with the speaker connections.

If you use a switch to do this, however, you run the addtional risk that you may have the internal speaker switched off without having the cab connected. If you turn the amp on in that state, it's unloaded entirely- not good for the amp at all!

Now you can say to yourself "I'll be aware of that and never do it". Just like you can say you'll never start your car with the tranny in "drive"- but many a garage wall has been saved by the interlock that manufacturers install to prevent you from doing just that.

In short, there is a way to make it fail-safe- Use a jack to do the switching. You can wire a jack up such that the internal speaker is always on, unless a plug is inserted into the jack, in which case the internal speaker is shut off and only the cab is on line. A TRS jack is used with a mono cable to do this, in the same way TRS jacks are used to cut the battery on effects pedals when nothing is plugged in.

JohnH sent me a diagram for this a few months back, let me see if I can dig it out of the mothballs for you.

BTW, you don't necessarily need to mount the jack to your amp to do this, you could use a length of cable with a female TRS jack and just tape it in place to the back of the amp. But the connections would be a lot more road-worthy if you permanently mount the jack.

EDIT: Sorry, not a TRS Jack but a Headphone Jack, like this one:

www.mouser.com/catalog/specsheets/KC-301052.pdf

A TRS might work as well, but this one certainly will, as it's essentially a jack with a DP switch

[sumgai]

newey,

While it's not highly recommended practice, you can run a solid-state amp with no load, and suffer no ill effects, almost indefinitely. Since there's no load, there's no current draw, thus no heat, thus.... etc.

Not so for a tube amp, in fact there it's the exact opposite - some kind of load, proper or otherwise, must be present whenever the B+ is supplied to the plates. 'Nuff said.

HTH




sumgai

[sumgai]

vF,

Figuring out the amperage for that switch is easy. You already know the wattage (30), and the ohmage (4), so you need only apply a bit of Ohm's Law, and you're all set.

The basic tenet of Ohm's Law is:

Volts = Amps x Resistance

ergo....

Ahh, dahellwidit.... You wanna 3 amp switch. Leave the math and such crap to the Engineers, eh?

Oh, and most switches are rated at 125 or 250vAC, so that shouldn't be a problem for your needs.

HTH



sumgai

[vonFrenchie]

newey, that is a great great idea that I never thought of. I am opening pedals up all the time and I can't believe I overlooked it, such a simple solution.

I'll draw something up today and see what ya'll think about it.

gai, thanks for the amperage. There is a reason why I'm majoring in criminal justice and not electrical engineering.... its called MATH

[vonFrenchie]

This is a diagram of the internal speaker only. Obviously all red lines are positive and all black lines are negative, I say this just to make it 100% clear.



I connected the stereo (or right) channel to the ground just for redundancy. If there is a chance that it will fail... assume it will. That way I can connect the negative to the switch. I also connected BOTH the positive and negative to the internal switches just to completely cut the speaker out. I know this isn't completely necessary, but it doesn't hurt, as far as I know.

[newey]

I can't claim any credit for the idea, it's been around a while. This is the way headphones are generally wired so as to mute a speaker connection when the 'phones are in use.

I found JohnH's PM to me, and realized that discussion was a bit different- I was talking about an extension cab for my amp that would allow the internal speaker and the cab to be used at the same time. Series speaker wiring was needed to match the impedance. John came up with this fail-safe design using a toggle switch and a switching jack. With no jack, the internal speaker operates normally. Inserting a jack AND flipping the switch gives the internal speaker and a cab in series. If no jack is inserted, flipping the switch does nothing. This was to prevent a possible unloading of the amp.

I still haven't done this, another of those "sometime in the future" projects.

Here's JohnH's take on this:



This was to allow the 8Ω internal speaker to be used with an 8Ω cab; series gives 16 Ohms, which will cut the power output a bit but won't hurt my (solid-state) amp. Now SG says I won't hurt it anyway, but hey, I'd rather not tempt the fates too much. It's a cheap amp, but I like it.

[sumgai]

newey,

No, I said that you can safely operate a solid-state amp into no load (infinite impedance), not into a load that's too low in impedance. As the impedance goes lower, getting closer to a short-circuit, the amp sees no reason not to deliver more current (thanks, Mr. Ohm!), and of course, that's when the Environmental Police show up on your doorstep.

Over time, I've found that a rule of thumb is that you can get away with "dis-obeying" the 1:1 rule by a factor of 2 - you can go down by 50%, or you can go up by 100%, and still be inside the comfort zone of your power amp. Beyond that by more than a few percent, and all bets are off. And of course, the tone is also affected, sometimes noticibly, sometimes really noticibly.

HTH



sumgai

[vonFrenchie]

Okay, so I kind of understand JohnH's lovely drawing, but what (if anything) is wrong with mine?

[sumgai]

Frenchie,

Your diagram doesn't allow both the internal and external speakers to play at the same time, which is the whole reason for the series wiring scheme. John allows you to use both (in series), or just the external speaker only.

It all depends on what you want to accomplish, that's all.



sumgai

[vonFrenchie]

Well I just want to use the combo in either combo mode or head mode, not combo linked to a cab... mode. So I'm thinking my little diagram drawn up from both of your suggestion's is what works well.