Saturday, June 07, 2003

I was interested to note that David Hafler died this past week. Due to my long running audiophile obsession, I built a Hafler amp kit about 20 years ago. The amp is still running to this day as part of my brother's stereo system. I was so excited when I received the kit that I stayed up all night and finished it in one night. It worked from the first time I turned it on and continues to this day.

Hafler's influence in the nascent audio industry is right up there with the other greats such as Fisher, Marantz, etc.

It is also interesting that my latest preamp, the McCormack MAP-1, uses an Ambient Recovery Mode (ARM) that has some basis in the equally famous Hafler Circuit. I feel I was somewhat of a pioneer when I installed my first car stereo in my VW bug in the late seventies and built a rear speaker platform that used this Hafler Circuit. The crux of this setup is that you send the positive connectors of both the left and right amplifier channels to the third rear channel. The sound that is emitted from this third speaker is the difference between the two channels which is in essence the out of phase "ambient" information included on the recording. Needless to say I had one of the coolest car sound systems in my school and it led to a minor career in car stereo installation during high-school.

And to think that many think surround sound started with home theater and DVDs?


vtex said...

Hi Chris

I also have a McCormack MAP-1, primarily because of it's Hafler type ARM circuit. I too have employed this since the 1970's. I also tried to wire it into my car, but got no rear signal at all. I was told that car amps use a "common ground" which is why I couldn't do the L-R & R-L for the rear car channels. How did you get around this? I'd love to modify the Mark Levinson system in my 2003 Lexus ES300. Thanks for archiving your blog.

Bill V
Austin, TX

Chris said...

Great to hear from a fellow Map-1 owner.

Regarding your application of a Hafler circuit in your car I can only offer conjectures.

In my original implementation, I wired up the circuit in an early seventies VW Bug. A very simplistic electrical setup to say the least! I believe the car stereo was some manner of Pioneer. I used to hook up car stereos in my friends cars. Most cars were of American origin. The one car I had trouble with was a Japanese car. I later became aware that the Japanese cars use something called a positive ground. This may be the "common ground" you are referring to? I also suspect that things have become so complicated in car electronics, what with circuit protections and increased functions, that wiring something "wrong" such as the Hafler hookup may be next to impossible. There may be ways around this using resisters, etc. but it is beyond my expertise.

Thanks for leaving a comment.