Transformer Covers and PC Boards for DIY audio projects

Transformer Covers

Lundahl has developed a type of cover that houses their transformers appropriately, and provides ventilation and magnetic shielding, while allowing access to the transformer for rewiring should that be needed.

Lundahl Covers

Lundahl commissioned an industrial designer to develop a new transformer cover concept that fit the needs of their particular style of C-core transformer. The designer came up with a very clever, ventilated, space efficient cover that provides some unique functionality. It is a four piece design that uses the transformer itself as a structural member and is configured so the transformer connections are readily accessible without removing the whole assembly from the chassis. The material of construction is very heavy gauge steel, which supplies magnetic shielding allowing close placement of transformers. The finish is a medium charcoal semi-gloss powder coat. The Lundahl name and several lines are silk screen printed in black onto the top surface as a subtle, tasteful accent. Mounting to a chassis surface is accomplished by 4 screws through the bottom and there is a rectangular opening in the bottom through which connecting wires can pass. Because either of the sides facing the connection boards can be removed without disturbing the mounting, rewiring is no big task.

The large version of this cover fits the LL1620/1623/1627/1679/2410/2411/9202 output transformers and the LL1648/1649/1650/1651/1655/1669A power transformers. The overall dimensions are 4.95″ (12.6cm) tall and 3.76″ (9.6cm) in the other two dimensions and the cover weighs 2.3 pounds (1.05kg). A datasheet with detailed dimensions is available.

Lundahl transformer covers

The medium/small cover fits two sizes of transformers, the medium-sized LL1663/1664/1682 output transformers and the LL1638/LL1673 chokes, and the smaller LL1660/LL1671/LL1677/LL1689/LL1692 transformers, as well as the small LL1685 chokes. The overall dimensions are dimensions are 4.33″ (11cm) tall with a 3.76″ (9.6cm) by 3.15″ (8.0cm) footprint and the cover weighs 2 pounds (0.9kg). A datasheet with detailed dimensions is available.

Both sizes are supplied with the assembly hardware. Additional 4mm screw hardware will be needed to attach the cover to the chassis.

Small/Medium Lundahl Transformer cover: $55 each

Large Lundahl Transformer cover: $60 each

PC Boards

We have an array of small PC boards that make application of the smaller low and line level transformers easier. All of these are for the specific transformer types labeled on the PC boards. If you have questions about applicability to specific circuits, contact us at info@kandkaudio.com.

Single LL1544A/1550/1636/1678/9206/LL9226: $5
Board size: 1.2″ (3.1cm) x 1.7″ (4.3cm)
Stereo LL1678/9206/9226 for MC input: $10
Board size: 3.0″ (7.6cm) x 1.8″ (4.6cm)
Single LL1931 for MC input (includes gain switching): $10
Board size: 2.1″ (5.4cm) x 1.7″ (4.3cm)
Single LL1681/1933 for MC input (includes gain switching): $10
Board size: 2.4″ (6.1cm) x 1.7″ (4.3cm)
Stereo LL1931 for MC input (includes gain switching): $20
Board size: 3.2″ (8.2cm) x 2.2″ (5.3cm)
Stereo LL1941 for MC input (includes gain switching): $20
Board size: 3.2″ (8.2cm) x 2.2″ (5.3cm)
Stereo LL1690 (CT access on secondary): $10
Board size: 2.8″ (7.1cm) x 2.4″ (6.1cm)
Stereo LL1684/LL1948 (CT access on secondary): $10
Board size: 2.8″ (7.1cm) x 2.4″ (6.1cm)

We have developed PC boards that mount on and solder to the LL1679 and another for the LL1620/1623/1627/9202. These boards, for the secondary windings side of the transformers, facilitate simple speaker impedance matching changes. A picture of one of these is shown below. Either the terminal/block jumper arrangement shown can be used, or for hair-shirt purists jumpers can be soldered in place of the terminal strip. Wires leading to speaker binding posts solder directly to the PC board. See the individual transformer data sheets for the details of the connections listed below.

LL1620/1623/1627/9202 PC board, options for secondary connection diagram B or C’ :$25

LL1679 PC board, options for secondary connection diagram B or C:$25.00

LL1679 PC board, options for secondary connection diagram C or D:$25.00

 

Inspirations: Music for Solo Flute

Catherine LeGrand, Flutist

Classical Flute Music composed by C.P.E Bach, Hildegard von Bingen, Astor Piazzolla, Claude Debussy and others

This CD was recorded by Kevin Carter using an all-tube analog signal chain direct to a hard drive at 20 bit 88.2kHz resolution. Cad VX-2 vacuum tube microphones were placed in a Blumlein figure 8 crossed pair and amplified by a custom K&K Audio designed and built Lundahl transformer-coupled (using LL1550 and LL1660/PP transformers) microphone preamplifier.

To purchase this CD go to www.in1breath.com