Forums
New posts
Search forums
What's new
New posts
Latest activity
Members
Registered members
Current visitors
Log in
Register
What's new
Search
Search
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Audio and Video Talk
Valves / Vacuum Tubes
Updated circuit for Mars Stereo 70 amplifier
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Help Support AVForums:
This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Message
<blockquote data-quote="Ampdog" data-source="post: 511212" data-attributes="member: 144"><p>Again, well done there, Karel.</p><p></p><p>A general comment regarding all valve amplifiers - just appended here because this is the current circuit on the forum.</p><p></p><p>One often hears about threatening instability when valve amplifiers are operated without a load. Such instability mostly took the form of oscillation in the 50kHz - 100kHz region. It has always been customary to 'load' the output with a 1K resistor, which takes care of tendencies to oscillate unless the design leaves something to be desired. These days of mostly 8 ohm loudspeakers a 680 ohm 1W resistor will do; it absorbes less than 1,5% of the output power. (I have recently 'calmed' a Sansui A111 with this measure; it was on the verge of no-load oscillation, becoming totally stable when 680 ohm load resistors were installed.)</p></blockquote><p></p>
[QUOTE="Ampdog, post: 511212, member: 144"] Again, well done there, Karel. A general comment regarding all valve amplifiers - just appended here because this is the current circuit on the forum. One often hears about threatening instability when valve amplifiers are operated without a load. Such instability mostly took the form of oscillation in the 50kHz - 100kHz region. It has always been customary to 'load' the output with a 1K resistor, which takes care of tendencies to oscillate unless the design leaves something to be desired. These days of mostly 8 ohm loudspeakers a 680 ohm 1W resistor will do; it absorbes less than 1,5% of the output power. (I have recently 'calmed' a Sansui A111 with this measure; it was on the verge of no-load oscillation, becoming totally stable when 680 ohm load resistors were installed.) [/QUOTE]
Insert quotes…
Verification
Post reply
Audio and Video Talk
Valves / Vacuum Tubes
Updated circuit for Mars Stereo 70 amplifier
Top