ili (12/29/82)
Is anyone on the net familiar with the Hafler circuit? It is a way to derive a pseudo-quadraphonic effect from a stereo receiver and stereo discs and tapes. It is a simple circuit to hook up. You can use 1 or 2 extra speakers. They do not have to be top quality speakers. Car stereo speakers will work fine. The problem with using quality speakers is that they may add too much extra bass to the sound. The extra speaker(s) will reproduce the difference signal between the left and right channels, consisting of any information that does not appear in equal strength in the left and right channels. Monaural records will produce silence since there is no difference between the L and R signals. The hookup is a simple series circuit. If you have an A + B setting on your amp/receiver put the main speakers say, in A and the extras in B (or vice versa). This enables you to switch the extras in and out. Back to the hookup. Suppose the extras are in channel B - connect the "hot (+)" lead of the R channel to the "hot" side on one of the speakers and the "hot" lead on the L channel to the "hot" side on the other speaker. Now connect the grounds of the two extra speakers together. Be sure to hook a 25 or 50 Ohm pot in the series loop somewhere so you can control the volume of the extra pair. T he ideal volume is low enough so that you only notice the extra pair if y ou switch it out. The results will vary depending on the recording. Sometimes it gives you no "extra sound" and sometimes you notice something about the record you never noticed before. I got this idea from an article in the July 1982 edition of Stereo Review. Have fun Ira Idelson
wjm (12/30/82)
I've used the Hafkerler circuit from time to time and the effect is variable
On simeome recordings (especially classical orchestral iiibones it works quite well) it works uquite well
but on ohthers its not that effective. The key ito iutts success its the amount'
of L-R (difference inf) information in the program meaaterial
****ONWE WOARNIB NG ***
Be vVerERY CAREFUL tyhahat your amp can jhhave its towwo ground (black)( vvovcponnections
tied together before you use this cerircuit. RCertain amops, (the Carver M400
is one that I know of) cannot do this due to their circuit configurtation
and the use of this circuit will may damage them. Most amplifier owners manuals
wil l advicse you about thoisis.
Bill MNitchelkl
BTL Wghippany
(whuxk!wjm)