K&K Audio / Lundahl Transformers

Welcome! Need support, you got it. Or share youe ideas and experiences.

Use this form to submit comments directly to the Asylum moderators for this forum. We're particularly interested in truly outstanding posts that might be added to our FAQs.
You may also use this form to provide feedback or to call attention to messages that may be in violation of our content rules.

You must login to use this feature.

Inmate Login

By default, logging in will set a session cookie that disappears when you close your browser. Clicking on the 'Remember my Moniker & Password' below will cause a permanent 'Login Cookie' to be set.

Moniker/Username: The Name that you picked or by default, your email. Forgot Moniker?	Examples "Rapper", "Bob W", "joe@aol.com".
Password:	Forgot Password?
	Remember my Moniker & Password ( What's this?)

If you don't have an Asylum Account, you can create one by clicking Here.

Our privacy policy can be reviewed by clicking Here.

Inmate Comments

From:
Your Email:
Subject:

Message Comments

Original Message

Re: Interstage Transformer Nomenclature

Posted by KevinC on January 15, 2005 at 13:35:30:
There are two basic ways to express transformer primary/secondary relationships: as a turns (voltage) ratio or an impedance ratio. The impedance ratio is the mathematical square of of the turns ratio. When one refers to a 1:2 transformer, this means that there are twice as many turns of wire on the secondary side of the transformer, therefore, if a 1VAC signal is present at the primary, a 2VAC signal can be measured at the secondary. If the source impedance of the generator of the signal is 1000 ohms, the impedance measured at the secondary would be 4000 ohms (2 squared). A transformer listed as 1+1:2+2 simply has two separate primary windings and two separate secondary windings. The primaries can be connected in series or in parallel (as can the secondaries), so that the 1+1:2+2 transformer can be used to obtain many different resulting ratios.
For a SE amp the selection of an IT is fairly straightforward. Normally a ratio of anywhere from 1:2 to 2:1 is used. The step-up 1:2 case is useful to get more "voltage drive" from the driver tube, but presents a higher source impedance to the grid of the output tube due to the impedance step-up (2 squared). Often a 1:1 ratio is chosen, assuming that the driver has enough voltage swing to drive the grid of the output tube to nearly 0 volts. Occasionally, when a low driving impedance is needed a step-down IT is chosen (2:1), but it necessitates a large driver tube voltage swing to overcome the voltage step-down.
I hope that this basic stuff helps get you started.

Kevin Carter
K&K Audio
www.kandkaudio.com