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
Valve output transformer question
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="handsome" data-source="post: 983437" data-attributes="member: 772"><p>Its good to use the highest tap on <em>tapped secondary</em> because you are then using the entire secondary. Using a lower tap leaves the "upper bit" flapping in the wind <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> which can compromise coupling. This is why some transformers have separate secondary windings that are combined in different ways to get the appropriate impedance - so the primary is always coupled to all of the secondary. How much performance is compromised is obviously down to the quality of the transformer. </p><p></p><p>Working out thenew feedback resistance is simple:</p><p></p><p>New R = Old R/ square root (old impedance/new impedance)</p><p>New R = 39 000R/square root (16/8)</p><p>New R = 39 000R/ 1.41</p><p>=27 650R</p><p></p><p>27 k will do of course. You don't want to fiddle with R4 as it sets the bias for the input tube. You can apply the same calculation to the capacitor that bypasses the feedback resistor - in this case obviously there is none.</p></blockquote><p></p>
[QUOTE="handsome, post: 983437, member: 772"] Its good to use the highest tap on [i]tapped secondary[/i] because you are then using the entire secondary. Using a lower tap leaves the "upper bit" flapping in the wind :-) which can compromise coupling. This is why some transformers have separate secondary windings that are combined in different ways to get the appropriate impedance - so the primary is always coupled to all of the secondary. How much performance is compromised is obviously down to the quality of the transformer. Working out thenew feedback resistance is simple: New R = Old R/ square root (old impedance/new impedance) New R = 39 000R/square root (16/8) New R = 39 000R/ 1.41 =27 650R 27 k will do of course. You don't want to fiddle with R4 as it sets the bias for the input tube. You can apply the same calculation to the capacitor that bypasses the feedback resistor - in this case obviously there is none. [/QUOTE]
Insert quotes…
Verification
Post reply
Audio and Video Talk
Valves / Vacuum Tubes
Valve output transformer question
Top