Thoughts on building a small power amp for a Heil Talkbox

[gators81]

I have a Heil Talkbox that I use from time to time. In a normal situation, I run a speaker cable from one of the two 4ohm speaker outs on my Boogie Dual Caliber. The drawback is that for the Heil to sound it's best, the master volume needs to be cranked up pretty good. Great for big gigs where I can sidefill off stage, but sucks for small gigs where the amp is close and stage volume is an issue.

Is it feasable to build a small power amp that I could run out of the Slave output on my amp? Or should I just find an inexpensive little amp, like one of those 8" or 10" speaker type, and just feed the Heil off of that from the Slave out on the Boogie?

[ACS]

I personally run my talkbox (DIY, not Heil, but the same concept - high powered mid range horn driver) using my 15W solid state Peavey Audition practice amp.  Run it with a simple A/B to my main amp.

Actually, you'd think this would compromise on the sound, but ironically, the sound through the Peavey (using the internal distortion 'channel'  ) is actually better than when I've run the talkbox from anything else...

[sean k]

I'm putting one of these things together and got quite confused initially about how much power was required to drive the compression driver... until I did some searches under talkbox driver and found alot of guys were quite happy using very little amps, with even impedance mismatches, to drive the driver. So I'm going to try a TDA 1905 at 25V into a 16ohm driver.

Seems to be it's a little bit more about matching the power to the driver with the sensitivity of the microphone you're going to use it with.

[gators81]

I used to have a Peavey Decade practice amp but got rid of it years ago. Wish I still had it now. I think I'll just go to a couple of pawn shops and see what I can find. Maybe ebay.

[ehofherr]

I did a quick search on eabay and found a lot of Fender practice amps for little $$.  When I first built a talk-box, I powered my HF driver with a Marshall MS-II (when using just the talkbox) and a Fender Frontman practice amp when using the talkbox as an extension speaker.  No real difference in sound (tone or level).  I ultimately turned to the ROG Little Gem MK II to power the HF driver.

That works great!  I don't have to worry about stage noise or anything.  I can use battery or wall-wart for power.  The cost to build even a Ruby is much less than purchasing a practice amp.  Just my 2 cents worth.

Right now, my daughter is using the Frontman practice amp.  When she's finished with it, I'm going to replace the 8" speaker with an 8" HF driver I have sitting around.  That will be another talkbox.

[gators81]

I found an inexpensive Ibamez anp at a pawn shop for $40 bucks. Wired the speaker out to a switch jack so I can still use the amp for practice and checking projects at my workbench. Pluging in a cable disconnects the speaker for use with the talkbox on stage. Works just fine.

[RJB510]

I was thinking of doing the same thing.

I was going to make an "LPB1" http://www.tonepad.com/project.asp?id=31 preamp and run that into the Ruby from ROG.
First, I know that this isn't huge power and lots of people just use a practice amp. But a self contained unit would be better for me to begin with. Will this setup work? (not concerned with volume but more problems i could find that could blow my driver such as impedance mismatch etc).

The horn driver I am using is a 200w max power. Is 8ohm and has a freq. response of 750-20000hz.

After reading all the talkbox threads available, I have seen that I need to add a cap in series to limit the lower frequencies. I was looking at a 22uf or 15uf cap to filter out the lows. Should I go lower or does that sound about right?

Will I need an inductor to roll off the high's also?

Where should I put these? Inbetween the preamp and power amp stages? Or can I just simply modify the Ruby amp to better suit the frequency I should be aiming for with that driver? or not bother with any of that, and just put it inline after the amp with the driver?

Sorry for the bombardment of questions, but some of this stuff just goes over my head sometimes and i'd had to waste $75 on a driver the first time (i couldn't get a cheaper driver, Stuff in Australia sucks for this kind of thing)

Cheers

[petemoore]

  Elliot sound has stuff...to read !
  Since the LM386 has limited output, restricting passive losses to the input will make the most of whats available, limiting bandwidth pre-amp allow the amp currents to ''focus'' on what is relevant [ie LF's aren't probably helping the driver or the amp, HF's may need tamed if too sharp, further filterings etc. may prove useful. ITCase this generally means bandpass filter.
  What tends to blow the diaphrams isn't too big but too small an amp, pushed to clipping [can thwack-slap a coil right out of the socket, don't ask how I know], so it's limited headroom that Would be a danger.
  That said, you have 200w driver, much more stubborn as far as getting fried or over-stressed than say a 15w one. And the LM386 can clip or rail out all day on this beast and not even begin to ruffle a diaphram, in fact the driver can be made to deliver output many times above the call that a voice box requires.
  Most of the recordings I remember have 'distortion'> voice box sound, but this is probably an amplifier [tube or SS with plenty of headroom] large enough to control the coil without 'breaking a sweat' [or nearing a power rail]. The distortion would be a typical small signal distortion. 
  So for x times a bukk or three, LM386 is a handy amp, and will do a voicebox effect, when more control and louder output of the driver is desired, a more powerful amp will do it, powerful enough possible to blow the driver...mainly if you let clipping of SS output get to it [make amp that isn't pushed to limit, larger amplifier is actually safer in this regard, once over X power level, clipping can 'blap 'n slap' the diaphram, the 386 does this and the driver absorbs it all day because the output, though hard clipped, is still weak enough].