Safe Talk Box

[Bananagab]

Hello!

I want to build a talk box. I saw how easy and inexpensive it is to build and it seems like a really cool effect to use. But, according to multiple websites, a diy talk box can easily blow your amp up.
I also read that using a tube amp is really not recommended because switching between the regular guitar cabinet and the talk box can damage the amp.

My question is, what precautions do I have to take to safely use a diy talk box? Is there a particular wiring I should use or the one included below is safe?

My amp setup is a Tiny Terror connected to a 8 ohm 1x12 speaker cabinet.6

Thanks in advance!

[greaser_au]

Running a valve amp without a load is not recommended, it can cause damage to output valves and/or output transformers, especially if signal is running through the amp.

Note that if the talk box switch is break-before-make it will leave the amp without a load briefly (and there is likely to be some signal through the amp at this point!) - one would expect the manufacturers of the Real Thing (tm)  will select their switches correctly...   

One other concern is that failure of the talk box switch or driver can leave the amp without a load for an extended period.

david

[patricks]

The original Heil talkbox used the setup in the diagram you posted, but newer versions (MXR M222 talkbox, and the Banshee Rocktron) have an inbuilt solid-state amp. That way, you can use the talkbox almost like a regular stompbox without having to worry about blowing up your guitar amp.
The MXR talkbox uses a class D amplifier; it shouldn't be hard to find a suitable circuit to adapt. Careful of the output level, though, or you'll rattle your fillings loose. With an ABY box, you could even run the talkbox in parallel with your guitar signal chain 

[GibsonGM]

I made one out of a horn driver I was given. What you use isn't that important, but THIS is....

I used an A/B switch...send my signal to my big ol' tube amp normally...when I want the box, I hit the A/B, sending my signal to a SMALL 5W (?) SS PRACTICE AMP that i don't care much about, and the "A" path is grounded to reduce hiss in main amp.  This drives the talk box via speaker out jack, and my little voice tube is mounted on a separate mic stand from my vocal mic.     The PA does the rest.  It's between you and the sound man at that point....

This is, I believe, how Frampton and the other Gods did it in the 70s...all you are risking is the small amp, which has MORE than enough juice to get loud enough for the mic....the mic just needs to hear talking-level volume...if you kill the little amp, so what?   I used mine many times, esp. at home just jamming, and it never had any trouble at all driving that horn.

Hope that gives some more info...

[karbomusic]

I built one as pictured above 20 years ago, ran it live through an old Fender Bassman head for years, never had a problem but also never had a failure where the amp didn't have a load. I was always nervous about it. That being said, I still have it and am wondering if something like a small LM386 amp circuit might work to power the horn? Easy enough to try since I have a couple of those lying around.

[Mark Hammer]

I have one of those Danelectro Free Speech talkbox units.  It comes in the form of a stompbox, and uses a 386-based on-board mini-amp and speaker, with a specially-cast bezel built into the chassis above the speaker, so you can attach the hose.  There is a jack for plugging in a mic.  The unit treats everything just like a stompbox, such that  when bypassed, the amp is still "running", and connected to the speaker, but the mic is disabled, and the guitar has a straight feedthrough.  Oddly enough, if you have no hose or mic, you can use the unit asa small battery-powered amp.  Although the small bezel hole makes for reduced audible loudness.

How does it sound?  Okay, but you really need to watch mic placement to get a decent sound.  Like any talk box, thebass will be lacking.

No matter what the setup, or amp type, engaging and bypassing the effect will involve somehow cancelling the mic input, such that one doesn't get feedback from the talk-unit itself when bypassing it.  The speaker can remain connected to the amp, and you'll get whatever residual hiss it produces, but the mic signal feeding the amp has to be lifted.

[PRR]

If you use the TT to drive a passive talkbox, it "will" have a load: the driver inside the talkbox.

But that load may not be right for the amp.

And I do NOT believe you want all 15 Watts being hosed into your head. Permanent deafness is a real problem.

Also I doubt that all the effects/distortion in your regular amp path are useful via talkbox.

I thought these things tapped into the "guitar cord". When talkboxing, the cord to the amp is fed "silence", so the amp rests safely(*). A mini-amp in the talkbox drives its speaker to the hose. Singer-mike feeds PA system.

(*) Alternately the talkbox could have a mike preamp and feed your mouth-output from mike to regular guitar amp, which is quite safe though extra guitar-y.

[Mark Hammer]

We've had many discussions about talkboxes over the years.  One of the things I keep reminding people about (though it wasn't the nature of the original post in this thread) is keeping the path between the speaker/driver and the mic efficient.  The longer and more narrow the hose, the more acoustic energy is lost (plastic hoses absorbing a lot), and the more the tone is shaped by the resonant properties of the hose.  So the hose should be as short and wide as possible, whilst still being able to fit near your mouth and the mic+hose be encirclable by your mouth.

I haven't seen many experiments with things like electret capsules, and the like.  People seem to just assume you plunk an SM58 on a mic stand like a voice mic.  One needs to think of the hose and mic as being one continuous path, and your mouth is simply the "EQ" inserted in the way.

[Bananagab]

Ok,
So I should buy the cheapest 1-5W amp possible or build something like this http://cdn.instructables.com/FOL/UZZA/I2IWCZRD/FOLUZZAI2IWCZRD.MEDIUM.jpg or that http://www.runoffgroove.com/ruby.html and use a A/B box to switch between the main guitar amp and the talk box right?

[Mark Hammer]

You don't necessarily have to switch between the talk box and your main amp.  The Free Speech pedal I mentioned is just like any other stompbox.  It goes in your pedal chain to your guitar amp, except that what gets fed to your guitar amp is the modified guitar tone from the mic.

[Bananagab]

You don't necessarily have to switch between the talk box and your main amp.  The Free Speech pedal I mentioned is just like any other stompbox.  It goes in your pedal chain to your guitar amp, except that what gets fed to your guitar amp is the modified guitar tone from the mic.

I'm not sure on how to build that. I can't find a schematic online and I'm not experienced enough to figure that out on my own .

[karbomusic]

And I do NOT believe you want all 15 Watts being hosed into your head. Permanent deafness is a real problem.

Imagine what the 100 watt Bassman was like. No bother to the ears but rattled fillings like a jackhammer. The hose didn't stand a chance at calming that fury down. The driver was from an old Kustom PA cab with 2x12 + horn. That driver withstood amazing abuse and still works to this day.

[Mark Hammer]

You don't necessarily have to switch between the talk box and your main amp.  The Free Speech pedal I mentioned is just like any other stompbox.  It goes in your pedal chain to your guitar amp, except that what gets fed to your guitar amp is the modified guitar tone from the mic.

I'm not sure on how to build that. I can't find a schematic online and I'm not experienced enough to figure that out on my own .

Imagine the following:  Your guitar signal goes to something like a loop selector.  In bypass mode, it works as per usual.  In "effect" mode, it feeds a small 386-or-other based amp that feeds a speaker of suitable dimensions/efficiency.  While the input to the pedal goes to the mini-amp, the output of the effect comes from a mic preamp.  The challenge is to find a mic capsule with decent sensitivity, capacity to withstand a mouth crowding it that badly, and suitable frequency response, and make a mic preamp that can bring the mic signal level up to something comparable to the bypass level.

You may find that some frequency tailoring of both the mini-amp and mic preamp is needed to arrive at an effect tone you like, and that doesn't suddenly change from big and beefy to thin and reedy.  That may or may not be a tall order, but if you want to do it, that's how its done.

As an aside, cheap plastic funnels from the dollar store make a great adapter for fitting between a speaker and a hose.