Keyboard into Guitar Amp question

[Sherman Stax]

hey everyone...here's an incredibly basic question. i'm used to playing keys through a DI but have just paid off a refurbished fender twin. was thinking it might add a bit of class to the keyboard sound (live and in studio). what is the deal with keyboards and guitar amps? is there an impedance issue ie do i need some kind of Di box/ Lo-Z to Hi-Z thing? or am i talking a complete load of bollocks?

[winky dinglehoffer]

I run keyboards through guitar amps all the time. It's not a problem.

[Sicily]

I'd guess it depends on the keybord you're using, but I've heard about folks blowing guitar amps up in one way or another by using them with keyboards...

It probably has something to do with the incredibly low tones some of them can make. I use my Juno 106 through a guitar amp as well, but at fairly low volumes. Most people will tell you to use a bass rig to play keyboards through.

[bedbug]

I recently blew a set of cheap stereo speakers by running a keyboard through our band's "P.A." (a four track hooked up to whatever cheap speakers are around) and playing the electric piano sound.

But I've played my cheap Roland synth through an Ampeg guitar amp lots of times and have never had a problem with it (other than the sound not being exactly what I wanted).

[DUC]

Nothing cooler than playing my minimoog through a 1964 Fender Bassman with a 2x15 cab.

[eeldip]

first of all, your idea is great. personally, i hate DI keyboards live. i like the sound of a keyboard to "come from somewhere", and have a sonic signature that seperates it out from the other things in the PA (if it is being re-enforced). this is especially true if the keyboard is integrated with other instruments that have amps.

also, amps roll off the highs and compress the signal. both of which are pretty big benefits for live work, and again, allow for a more integrated sound with a band or whatnot.

some problems you can run into relate to the impedance issue talked about above, some amps dont respond to them as well as others. i had a vox ac30 sitting in my studio for a year or so (some rich friend of mine brought it over and left it cause it was too heavy). keyboards sounded great though it, but they were so hot that you couldnt turn the volume past 1. and the volume knob was really not setup to work between 0 and 1, so usually it would just jump from silence to too loud. i also have a peavey 4x10 tweed thing that works, but can be sort of buzzy.

if you have problems, you could try buying a transformer for the signal and that may help...

[Sherman Stax]

thanks guys...yeah i had some issues with playing my juno thru my old amp (a cheap marshall combo) when we were practising.... i noticed the volume thing too, the keys had to be set to virtually zero volume. and the amp sounded like it was crapping out, although i wasn't sure if this was the keys or the fact that it was a well loved and gigged amp. i don't really want to damage my twin so maybe a transformer is the way to go. would a DI box do the business?

[eeldip]

a DI is not made for this purpose, you need something to translate a line level signal to an instrument level signal.

[markpar]

a DI is not made for this purpose, you need something to translate a line level signal to an instrument level signal.

Won't a ReAmp do that? http://www.reamp.com

-mark

[EasyGo]

you need something to translate a line level signal to an instrument level signal.

Yeah, it does seem like the line level might do some sort of harm, but no one seems to report any!

There's a simple circuit on the Jensen site for line to instrument level:

http://www.jensentransformers.com/as/as092.pdf

[EasyGo]

a DI is not made for this purpose, you need something to translate a line level signal to an instrument level signal.

All this talk about keyboards and guitar amps got me thinking.

A couple months back, eric blam, xonlocust, and I built DIs from the Jensen Transformers site.

http://www.jensentransformers.com/as/as066.pdf

I'd hoped this passive DI could be used in reverse as to 'reamp,' or send line level, low impedance signals, such auxilliary sends, tape outputs, and keyboards through guitar amps expecting an instrument level, high impedance signal.

I'm happy to report that the experiment is at least a preliminary success. Last night I plugged my Roland DJ70 keyboard with volume knob cranked (using a 1/4" to female XLR cable) into the DI and through to my Mesa Boogie guitar amp. Without the pad engaged, the signal was overly loud, but with the variable pad switched in, I was able to attenuate the signal down to an instrument level, using the pot as an ordinary volume control.

Thought this might be of interest to keyboardists that plug into guitar amps, or those interested in sending recorded tracks to guitar amps.

The project cost ~$120 in parts, which is not bad considering you get a nice transparent DI (bass or keys) and line-to-instrument level in reverse. Jensen says to use a different transformer and circuit for reamping, but this seems to work fine.

I could print the parts list from Jensen and Mouser if anyone's interested.

Don

[NewYorkDave]

Contrary to what the makers of certain devices would have you believe, there really isn't an impedance issue when you're going into a high-Z input like a guitar amp. There's a LEVEL and BALANCE issue, however. For the matter at hand: the typical synth has unbalanced line-level outputs on 1/4" jacks. You can plug it right into the guitar amp; the high level might distort the first preamp stage; but if you like the sound, go with it. It's not going to "blow anything up." Excessive bass levels CAN destroy the speakers, however. If the sound is too distorted even with the amp turned down, try turning down the synth and/or use a simple resistive pad. You don't need a "reamp" or any such device.

[eflatminor]

As I believe others have said, it's not an impedance issue. It's a level issue. The keyboard sends a line level signal out which is much hotter than the signal comming out of a guitar. You might end up with little usable volume control but it should work.

Also to keep in mind is the fact that most guitar amps are made "dirty" meaning their amplifier circuits are inherently distorted (not the preamp fuzzy distortion but THD type distortion). They also roll off the lows and highs. This is the sound we humans love for an electric guitar but it's not well suited to most keyboard sounds where a wide frequency range and clean amplification are generally sought. On the other hand, if you like the sound going through a guitar amp, go with it!

[Sherman Stax]

that reminds me of a cheesy but memorable guide to impedance i read somewhere - high into low won't go, low into high will fly! i wonder who made that up...