Re: [EE]:: LM317 amplifiers - 2Hz flat to100Khz, THD ~= 0.012% at 1 kHz (applications)

Hi Russell,

Nice. Reminds me of when I made a Class A headphone/small speaker amplifier with a TL431, three resistors and two capacitors as an inverting amp with a gain of 10.

Worked great, low distortion, the only real shortcoming was the noise from the internal reference was noticeable in headphones. Bedini's use of an opamp for gain would take care of that problem.

Thanks for sharing that.

Bob

________________________________________
From: Piclist <[email protected]> on behalf of RussellMc 
Sent: Saturday, May 3, 2025 4:04 AM
To: Microcontroller discussion list - Public.; Russell McMahon
Subject: [EE]:: LM317 amplifiers - 2Hz flat to100Khz, THD ~= 0.012% at 1 kHz (applications)

From John Bedini, famous for making such amps, among other things

"The Amplifier using these devices uses about 4.2 amps of current on each
channel, about 8.4 amps total. The frequency response on my test equipment
at the time was 2Hz flat to100Khz the THD was very low about .012 at 1 kHz
although some measured much lower then that at the McIntosh Audio Clinics."

From here

https://www.head-fi.org/threads/lm-317-as-audio-amplifier.222363/?fbclid=IwY2xjawKC1C9leHRuA2FlbQIxMABicmlkETFXam55MW9ZRkUxNGVWZkJtAR7ylmcy_FThjrnyGoSb4MF0eqlLuIY_WzYHO881Orh8ZFGG4Ul7cHJAtgoBnA_aem_Qo5h3RVzLhcLS7Gm3sbYsw#post-9991998:~:text=I%20did%20not,answer%20was%20yes
.

Also - Push pull '317 circuit here

https://www.diyaudio.com/community/threads/and-now-the-regulator-chip-jlh-amp.176052/


Russell McMahon