New Interstage Transformers Designed for Single-Ended Amplifiers

Lundahl Transformers has quietly introduced a series of new transformers that were designed specifically for SE use as interstage transformers. While the LL1660, LL1692A, and LL1671 have been great transformers in my hands and in those of many others, there was performance to be gained by designing new transformers whose winding geometry has been optimized solely for single ended drivers and output stages.

These are the part numbers, prices, and their turns ratio data. Data sheets can be accessed from the data sheet menu.

Part                  Turns Ratio         Price (USD)

LL2746                   1:2                        $145

LL2753                   1:1                        $145

LL2756                   1:1                        $145

LL2762                   1:1                        $110

The LL2746, LL2753, LL2756, and LL2762 are also available with amorphous iron cores and/or silver wire coils at higher prices.

The LL2746 and LL2753 are designed to work with lower plate impedance tubes than the LL2756 and LL2762. The LL2756 and LL2762 are similar in application, but the LL2756 is larger and has a lower winding resistance for a given amount of primary inductance than does the smaller LL2762 (same size as the LL1660).

Audio Transformer Basics 101

We’ve added a new series of reference documents under the “Transformers” menu heading, labeled “Transformer Basics 101”.  These articles were developed and authored for Lundahl Transformers by a well-known pro audio designer, Ken DeLoria.  These provide an excellent introduction to audio transformers:  rationale for use, applications examples, construction/manufacturing, and a bit of transformer theory and math.  Please feel free to browse these six “white papers” and take away information that can help you design better audio equipment.

Amplifier Input Stage and Power Supply Kits

These kits are now all in stock ready to go.  They make amplifier construction using the output stage of your choice straightforward and sonically rewarding.  A few early adopters have already built PP amps using the interstage transformer input stage and a variety of output tubes, including PP 6C33C and PP KT150 tubes.  Pictures and descriptions are forthcoming.

To sweeten the deal, we are offering a 10% discount on any amplifier components order that includes, but is not limited to, the following:

  • 2 channels of input stage kit (including the interstage transformers, if applicable)
  • 1 or 2 power supply kits
  • 2 channels of Lundahl output transformers

Give these a try for your next amplifier project!

New Products for April 2015

As some of you know, I’ve been developing a number of new products over the past year or so and many of them are ready or nearly ready for release.  Here is a synopsis of the products pending the full release of information in the relevant website pages:

Trio Phono Preamplifier Kit – The intro material and description are already on the website phono preamplifier page.  There are actually two overlapping kits ready to go.  The first is what I have called a Main Board Kit, which includes all of the circuitry on a PC board, including the output transformers (which in this case are off of the PC board due to size and weight).  This kit allows you to use your own enclosure, connectors, switches, power transformer and power supply choke to build a first-class tube phono preamplifier suitable for high output MM and MC cartidges .  The price of this kit is $625.  The other kit is what I have called a Complete Kit, which includes all of the parts listed above, as well as a few simple tools to complete the same Trio Phono Preamplifier without anything but solder, common tools, and labor.  The price of the Complete Kit is $1250.  An optional input board with MC input transformers and variable resistive loading is available as a kit for $375.  The use of this option will allow the Trio to be used with virtually any MC cartridge that has ever existed!

Trio Phono Preamplifier

Trio Phono Preamplifier

Single-Ended and Push-Pull Amplifier Input Stage Kits – Perhaps four or five years ago, I became interested in a group of relatively common high transconductance pentodes and their potential for use in audio designs, both from a practical standpoint and, of course, from a sonic standpoint.  The most well-known of these is the German Post D3a, but there are many others.  I have built a number of audio circuits using these tubes as triodes and found that they can sound really good and have unusual utility, in that they are quiet, have lots of gain, and have medium-low plate impedance.  So far the most promising application for them in my hands has been as amplifier input/driver stages in 2 stage single-ended and push-pull designs.  After building some “test amplifiers” including a couple of SE 6C33C amplifiers I’m quite fond of, I’ve developed three kits using these tubes.   All of these kits contain the parts (including Russian 6J49P tubes) necessary to drive your favorite output tube(s) in an amplifier chassis of your choice.   Two types of coupling to the output stage are possible with these kits, capacitive coupling or transformer coupling.  The capacitively coupled stages are supported with current source loading for the tubes.  The SE kit can be used with a LL1670 grid choke for better interfacing with the preamp driving it and the PP kits include an LL1544A phase splitting input transformer, so they accept balanced or unbalanced input signals.   Each output stage board includes the audio circuit and power supply decoupling or regulation.  A complete description with technical specifications will be published on the Power Amplifier page soon.

SE Input Stage Kit with Cap Coupling –  $125/ch without LL1670, $185/ch with LL1670, add $25 per channel for Jensen foil/oil cap

SE Input Stage Kit with Interstage Transformer Coupling – TBD

PP Input Stage Kit with Cap Coupling –  $199/ch with Jantzen Superior Z-Caps, $225/ch with Jensen copper foil/oil caps

PP Input Stage Kit with Interstage Transformer Coupling –  $199/ch without IT; $319/ch with Lundahl LL1692A/PP

Amplifier Power Supply Kits – I’ve also designed some simple kits that facilitate tube amplifier building.  While some of you will not be impressed by the lack of a tube rectifier, etc., these make amplifier construction more straightforward and address turn-on delay and soft start all in one package.  More information will be available soon.

Welcome to the new site

Welcome to our new site! We’ll have more content to post soon. Thanks for having a look around!