I have a guitar pedal on the way and it only has a plug for a 9v transformer, surely it wouldn't hurt to put a nine volt battery plug on it? If I did I assume id have to disconnect if I wanted to use the transformer?

Does the transformer supply AC or DC? If it is AC, you cannot use a battery. If it is a transformer / rectifier and supplies DC, you can use a battery. Read the back of the transformer, it will tell you.

Yes, it uses a transformer,The Ravish requires 9
– 9.6VDC at 200mA , can't imagine why they didn't add a battery socket in the first place. Here it is! http://www.ehx.com/assets/instructions/ravish.pdf

I guess they figured you would eat up batteries, You could have a 9 volt battery and end to fit into jack, just watch polarity, Most are tip positive, verify.
DC is Clean Power, may be some ripple from an ac transformer.
You could even use a Larger 9 volt battery. A rechargeable RC battery and charger would work, an example:

http://www.ebay.com/itm/9-6-Volt-4200-mAh-NiMH-Battery-Pack-Airsoft-Gun-RC-/110746850464?pt=US_Rechargeable_Batteries&hash=item19c906d4a0

They have chargerx for these at Hobby storex, Kmart, walmart?

Look at batteries and chargers here:
http://www.hobby-lobby.com/

I edited 2 words and had them end in x instead of s, other wise it you have an unwanted link to a an unwanted link?

So 4200 mAh won't damage it?

No, it will just Last for a really long time and is rechargeable.
The resistance of the electronics, will only draw that amount of load.
Another way to look at it is if you hooked your Effects to 2 9 volt batteries in PARALLEL, It would still be 9 volts, but last twice as long. If you hooked the 9 volt batteries in SERIES, that would be 18 volts, and likely do damage.

If this used 12 volts, you could use a car battery?

Ah, of course! Thanks again, it looks better than a common 9v.

I emailed the manufacturer this is what he said-Yes it does take a high current. If you tried to power it with batteries a standard 9 volt would last an hour or two at maximum. Also as the energy of the battery starts to get depleted the unit will start to get noisy, and also when really low it would start malfunctioning. It needs constant power which can only be achieved with an adaptor.
The pedal has a lot of very bright lights for some reasonI think I'll try your idea with the better battery, a few hours should be enough and I could always carry a spare, its worth it for the portability! What I want to know is I will have to add a switch I assume so that only battery OR transformer are on at once, should I put the break on the negative?

I thought the transformer plugged in, if so unplug it, and plug in new battery pack with the jack to match.
Just looked back at the Manual and the Tip is NEGATIVE.
Verify or Damage may occur.

Very good, no operations required. Warranty maintained! Thanks again!