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
Sansui 1000A Transformers on chassis
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: 759176" data-attributes="member: 144"><p>Firstly, output power is not simply working into a certain load impedance, but also transferring all of the valve generated power to the load. Putting resistors in serie with the anode(s) may give the 'right' impedance, but the power dissipated in the resistors is heat and does not contribute to the output.</p><p></p><p>As to the tables, one looks at class AB1 operation. (In class AB2 some input grid power is drawn and this is not generally applicable to quality audio amplifiers.) The lower power (18W) into a 3K8 load compared to 26,5W into 6K6 ohm is rather abnormal. (Usually output power increases with decrease in load impedance, as reflected in the higher peak current drawn, all other things being equal. I did not go to plotting graphical analysis for a check at this time; let us leave it at that.)</p><p></p><p>Basic Ohms Law arithmetic will show that to get 30W into a 6600 ohm load in push-pull, some at least 430V h.t. is required (taking an anode saturation dip of 80V) - this is irrespective of the valve used. One is therefore limited by Ohms Law regarding maximum output power available.</p><p></p><p>[Also keep in mind that valve data sheets give power available <em>at the valve anode(s)</em>. The efficiency of the OPT (at best some 90%) comes afterwards, thus a tabled output of 30W will give only 27W to the loudspeaker.]</p></blockquote><p></p>
[QUOTE="Ampdog, post: 759176, member: 144"] Firstly, output power is not simply working into a certain load impedance, but also transferring all of the valve generated power to the load. Putting resistors in serie with the anode(s) may give the 'right' impedance, but the power dissipated in the resistors is heat and does not contribute to the output. As to the tables, one looks at class AB1 operation. (In class AB2 some input grid power is drawn and this is not generally applicable to quality audio amplifiers.) The lower power (18W) into a 3K8 load compared to 26,5W into 6K6 ohm is rather abnormal. (Usually output power increases with decrease in load impedance, as reflected in the higher peak current drawn, all other things being equal. I did not go to plotting graphical analysis for a check at this time; let us leave it at that.) Basic Ohms Law arithmetic will show that to get 30W into a 6600 ohm load in push-pull, some at least 430V h.t. is required (taking an anode saturation dip of 80V) - this is irrespective of the valve used. One is therefore limited by Ohms Law regarding maximum output power available. [Also keep in mind that valve data sheets give power available [i]at the valve anode(s)[/i]. The efficiency of the OPT (at best some 90%) comes afterwards, thus a tabled output of 30W will give only 27W to the loudspeaker.] [/QUOTE]
Insert quotes…
Verification
Post reply
Audio and Video Talk
Valves / Vacuum Tubes
Sansui 1000A Transformers on chassis
Top