Joe Davisson Simple Power Amp Speaker Question

[ildar]

I assume the circuit calls for an 8ohm speaker. It's not specified, but it's probably a safe assumption. My question is a two-parter:
1) Can I use a 16ohm load without modification of the circuit?
2) If it does need modification, what specifically does it need?

[twabelljr]

I believe total output will be lower with a 16ohm load. Putting an additional 16ohms of resistance in parallel either at the speaker or at the board will make total load 8ohms.

[ildar]

I believe total output will be lower with a 16ohm load. Putting an additional 16ohms of resistance in parallel either at the speaker or at the board will make total load 8ohms.

In other words, an additonal 16 ohm resistor in series at the speaker out, in this case after the 2200uf cap?

[twabelljr]

I haven't seen the schematic yet, but place another 16ohms across the "-" and (+) speaker connections. Just as if the resistor was another speaker.

[Connoisseur of Distortion]

if you do this, you should make sure that you have a sufficiently strong resistor. i'm not sure what wattage that amp puts out.

[ildar]

I'd post the link, but I don't remember where I got the schem. 
It's a low power (< 2w?) unit. I won't be needing any 100w resistors, that's for sure.

[twabelljr]

Here's the link:       http://www.diystompboxes.com/analogalchemy/amps/simpleamp.html

[Ge_Whiz]

Just use the 16 ohm speaker. Any parallel resistor will only convert output into heat. A transistor amp won't get upset with a higher impedance load. You probably won't notice the reduced output power.

[KMS]

Ge Whiz is right.    If you add a resistor, the resistor will use the extra power (output as heat) and thus no more power will be distributed to the 16 ohm speaker, so the 16 ohm speaker gets the same as it would without the addition of a resistor but you would be working the amp harder with the addition of the resistor.

A 4 ohm load would be best and as far as I know all transistor amps can handle a 4 ohm load.  This would give you the best output.  Four 16 ohm speakers wired in parallel would give you a 4 ohm load. 
Some transistor amps can even handle a 2 ohm load, but you better call the maintenance department of the manufacture and check with them before trying that.

[petemoore]

  4ohm would get max output. 
  max output from small amps such as this may not be [isn't for me at least] what is desired anyway, and volume control changes change 'everything' [volume/distortion/load etc.] enough so that using a speaker with 8 ohms or 16 ohms would be less likely to make the amp try to surpass it's limitations...ie...if amp distortion is not the goal, higher impedance loads are probably well suited to it..but I haven't tried this one..
  With load being depending on input levels etc., if it doesn't distort with a 16 ohm speaker and single coil pickups, a 4 ohm speaker and boosted HB's will probably do it.

[ildar]

I'd like to build two of them, drive them with any of the few various amp sims I've built, preferably with stereo fx (i.e. chorus, delay etc.) between sim and power amps. Kind of a nice little practice/scratch recording setup. Also, sort of a testing ground for effects in my main rig.
I'm not looking for amp distortion, really. I'll get the OD from the sims. It just happens that I've got two 16ohm Eminence speakers in separate cabs and was hoping to use them without any problems.

[petemoore]

  Have you tried any LM386 amp stuff?

[ildar]

Such as the Ruby? I've built that, and I like it, I just want to try something else. 

[ildar]

Sorry to dredge this thread up, but I was looking at the schematic for this again (still haven't found time to build it).
I assume the output is less than 2W. Am I right or wrong?

[ildar]

Anyone?