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Accessories for DIY audio projects Two Terminal Constant Current Source These products were developed based on the Supertex DN2540N5 and IXYS IXTP01N100D depletion mode MOSFETs to enable constant current operation of tube circuits without having to worry about a source of bias. They are very simple and easy to integrate into existing designs. Use current sources to provide excellent balance in "long-tail" pair differential circuits or to obtain highly linear constant current triode operation as a plate load. Add a heat sink kit for operation at higher levels of power dissipation. Three versions are offered: an economical basic current source with very good performance, a cascode current source for improved measured performance and a slight sonic improvement, and a compact cascode current source that can be used to replace resistors for easy upgrading to constant current operation. These kits feature current adjustability over a wide range (2.5mA to 100mA) and space for a fixed resistor to replace the variable resistor once the “correct” current has been determined. The minimum operating voltage is 4VDC + 1/2 peak-to-peak AC signal amplitude and the voltage rating maximum is 1000VDC.
Transformer Covers We have sourced a range of covers for Lundahl transformers in three styles. Lundahl Covers
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” (9.53cm) in the other two dimensions and the cover weighs 2.3 pounds (1.05kg). It is supplied with the assembly hardware. Additional hardware will be needed to attach the cover to the chassis. Lundahl Transformer cover: $55 each
Retro Covers There are three sizes of these retro looking 3 piece transformer covers. The transformer mounts on the base, then the body/top of the cover screws to flanges on the base. The base and transformer are held to the chassis by the transformer mounting screws. The body and base are steel and are finished with a classic black wrinkle finish, while the top is brushed anodized natural aluminum. The dimensions are given below. Subtract 0.4" from the width, depth, and the height for internal dimensions. Because the body and base are steel, they afford some magnetic field shielding, where necessary, too.
Contemporary Covers Pictured below is a contemporary-looking cast aluminum cover that fits over the larger (LL1620/1623/1627/1679/9202) and smaller (LL1663/1664/1682/1683) transformers or chokes (LL1638/1673/1685). They are 4.75 x 4.75 inches at the base and taper slightly to 3.56 inches tall. The covers attach to the chassis by 4 x 6-32 threaded holes in the corners. They are stocked finished with matte black powder coat. Unfortunately, they do not fit the somewhat larger power transformers (LL1648/1649/1650/1651/1669A). Contemporary transformer cover: $36 each PC Boards
PC Board #1 - For LL1544A/1550/1635/1678/9206:$6.00
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 PC Board #1 - For LL1544A/1550/1635/1678/9206:$6.00 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 |
1004 Olive Chapel Rd.
Apex, NC 27502 USA (919) 387-0911 Mon-Fri 8 a.m. - 5 p.m. EST
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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. Please see the illustrations below for an idea of how this cover goes together and its final appearance. 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.
This small PC board (1.2" x 1.7") aids in connecting primaries and
secondaries for several similar Lundahl transformers:
LL1544A/1550/1635/1678/9206.
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.
