Tag Archives: audio

Q&A: Per Lundahl (Transformer Design)

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Per Lundahl is a multitalented designer who runs one of world’s leading high-performance audio transformer manufacturing outfits, Lundahl Transformers, which is based in Norrtalje, Sweden. After graduating from the School of Physics at the Royal Institute of Technology in Stockholm, he worked as a computer consultant for Ericsson. It wasn’t until he decided to move out of the city that he joined his family’s business, which his parents started in 1958.

Per Lundahl, CEO of Lundahl Transformers

In the April 2012 issue of audioXpress magazine, Lundahl shares stories about the company’s focus and products. He states:

I design all our new transformers. Our audio market is divided into two segments, Pro Audio and Audiophile. The Pro Audio segment includes transformers for microphones, mic pre-amps, splitters, distribution amplifiers, and other studio equipment. The Audiophile segment is transformers for MC phono cartridge step-up and for tube and solid state amplifiers.

Our biggest selling products are two types of transformers for microphone preamplifier inputs. In the Audiophile domain, our tube amplifier interstage and line output transformers are popular.

We constantly develop new transformers based on the requests of our customers. Presently we are developing an auto-transformer for a Chinese company and an interstage/line output transformer for some European customers. The latter will probably be added to our range of standard transformers, available to everyone.

For the very fastidious audiophile, we are also introducing silver wire in some of our transformer types. Initially, the wire will mainly be in our high-end MC transformers, but depending on the response, it is possible that we will extend the silver wire product range.

You can read the entire interview in audioXpressApril, which is currently available on newsstands.

Tube amp transformers

audioXpress is an Elektor group publication.

Voice Coil Parts & Production

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Voice coils are essential elements in loudspeakers of all sorts. Thus, understanding how a voice coil works is essential for audio engineers and DIYers alike. The main parts the bobbin, the voice coil wire, and the collar. Mike Klasco and Steve Tatarunis of Menlo Scientific provide in-depth information about voice coils in the March 2012 issue of audioXpress magazine.

The parts of a voice coil (Source: Precision Econowind)

Klaso and Tatarunis write:

“The bobbin provides a rigid structure on which the voice coil wire can be wound and the collar can serve several purposes. It secures the coil lead-out wires, reinforces the bobbin, and provides a convenient material for diaphragm attachment … In some cases—headphone speakers, for example—a monolithic (self supporting no bobbin or collar) voice coil may be used. But this article will focus on the more commonly used bobbin, coil, and collar designs.

Loudspeaker voice coils are seldom considered critical elements that contribute to sound quality, and few technical papers have addressed this issue. But when designing a voice coil, the selection and application of materials can have profound effects upon sound quantity, quality, and power handling. The mechanical energy from the winding stack moves by transconduction through the bobbin and collar before reaching the diaphragm. Any non-linearities in this path are superimposed upon the response of the speaker. Intrinsic characteristics of materials such as internal damping and Young’s modulus create specific sonic signatures and contribute to the residual distortion spectrum of the transducer … In selecting a particular material, a coil winder makes important trade-offs on the winding process. Knowledge of these variables can ensure better, more cost-effective coils, avoid conflicts, and improve production yields. Torsional resonances, internal losses, and electrical conductivity of the bobbin materials are some of the factors effecting the distortion, sensitivity, and sound quality of the finished loudspeaker.”

A close-up view of both a good voice coil and a burned voice coil (Source: The Speaker Exchange)

You can read the entire article here. For subscription information, go to www.audioamateur.com.

audioXpress magazine, like Circuit Cellar, is an Elektor group publication.

 

DIY Audio Design with Tymkrs

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With the growing popularity of embedded design kits and microcontroller-based platforms for rapid prototyping, it’s now easier and more affordable than ever for engineers, DIYers, musicians, audiophiles, and academics to customize electronics applications of their own. The March 2012 issue of audioXpress magazine will feature an interview with two DIYers—the duo behind Tymkrs.com—who do just that. “Atdiy” and “Whisker” provide details about Zombietech.tv, their design interests, and their recent projects. Here are some of their most interesting DIY designs:

  • SidCog Organ: Combine a programmable SID chip from the Commodore 64 and an old Hammond organ
  • Laser Audio Transmitter: Use a laser to transmit audio with a laser transmitter and a solar panel receiver
  • High-Impedance Preamplifier: A preamp designed with a JFET for loud and clean sound

Note: All photos courtesy of Tymkrs. The interview will appear in the March 2012  issue of audioXpress. audioXpress magazine (www.audioamateur.com), like Circuit Cellar, is an Elektor group publication.

EE Rap – Listen

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While doing some research for our upcoming interview with Dave Jones of the EEVblog, we came across “The EE Rap.” Check it out:

Here are the details from EEVBlog:
Music: Cole Hadwin
Vocals: Cole Hadwin, Ben Brand
Sound Bites: Dave Jones of EEVBlog.com