LM317 amplifier

[Russell Sit]

Hi,

This is an amplifier circuit employing an adjustable regulator LM317 as the active element. (adopted from Dulcet of the hifidiy.net)

I have done a search, and found this old thread here:
http://www.diyaudio.com/forums/showt...0643#post70643

I am going to build one, but before I actually start, I would like to hear your opinion first.

My plan is to replace the LM317 (max 1.5A) with LM338K (TO-3 package) (max 5-7A), in the hope that I could get more power out from it. Is it feasible, and is there any modification of the circuity needed?

Thanks in advance for your kind help!


Best wishes,
Russell

[SY]

There are chip amps with better performance for this application that are quite inexpensive. Why not use the right part for the job?

[Russell Sit]

Hi SY,

thanks for your reply. I have tried the chip amp way before (LM3875, 3886, OPA549). They are indeed very good.

The LM317 amplfier is just a mini-project for fun. In addition, it does generate heat like a real class A amplifier. ;-)

BTW, isn't the principle of the LM317 circuit similar to that of the chip amp?

Thanks again for your reply.


Best wishes,
Russell

[SY]

It's slower, has much poorer overload characteristics, and higher distortion. You could do better with a good opamp and a big old pass transistor and generate the same heat.

If it's for fun, then just throw one together on the bench and test it. Worst case, you're out $6-7 of parts.