aboulang@BBN.COM (Albert Boulanger) (12/05/90)
Reply to Kevin Kennedy, *NOT* me. Just posting for Kevin ;-).
Kennedy Audio Laboratories
C/O Kevin R Kennedy
240 Barker Ave. #8
Lowell, Ma. 01850
Tel:(508)441-1010
12/90
It's that time again, when Kevin rambles on about audio and related
subjects. This time I'm going to talk about the Sony CDP-790 CD player;
capable of good performance at a rather reasonable price, the Magnepan
1.4 loudspeaker; an easy to drive dipole, suitable for moderately sized
rooms, and the Counterpoint SA-12 hybrid power amplifer from a few
years back; affordable, quick and detailed without stridency....
I recently concluded that performance of CD players had advanced to
a sufficient degree to warrant some investigation. This feeling was
further agravated by my friend Paul who recently purchased a Sony Car
Walkman CD player that was in some respects better than my older
Philips/Magnavox. As I really didn't have a lot of money to invest I
looked at players costing under $400 and did some fairly inconclusive
listening at a number of stores, but even on the mediocre system that
was used the CDP-790 seemed more detailed and neutral than the others,
(Magnavox 502, JVC, Pioneer, etc.) and based on this I plunked down my
hard earned cash. This player should be available for under $300.00 at
any Sony distributor. This player can actually reproduce some depth and
ambience without the usual decay into a brick wall at very low levels.
Detail is very good and the sound is smooth, clean and fairly
inoffensive. It also is loaded with user oriented features that make it
very user friendly. The player uses Analog Devices AD1860N DAC's with
18 bits resolution and 8 times oversampling, a very simple one pole low
pass filter and a 4558 op amp as an output buffer. I was able to
improve the performance considerably by replacing the op amp with a
5532AN. In addition I replaced four 1K, four 220 ohm and two 560 ohm
resistors with Resista metal films, and all the film caps with Mallory
polystyrenes. I forced the output of the 5532 into class A operation
for better linearity by tying 10K resistors from pin 4 to pins 1 and 7
respectively. Other changes I made include Wima 1uF caps across the 47u
output capacitors and 0.01uF bypass caps across the 470uF supply
decoupling caps adjacent to the DACS. I think that a better version of
the AD1860 is available (AN). When I finally get the schematics I plan
force the DAC op-amps into class A operation if possible. There is a
lot of room for modifications and a tube buffer stage would be easily
fitted. Edges are very sharp on the chassis and cover so be careful not
get cut. Modify at your own risk, the service manual is recommended and
good soldering technique is a must.
I recently acquired a pair of used Magnepan 1.4 loudspeakers, and
to say that they are a big improvement over my old AR-58S loudspeakers
would be a gross understatement. They have absolutely phenomenal
transient response and much better overall resolution than anything I
have ever owned. It is even surprising to hear the improvement in low
frequency accuracy, but best of all, the speaker handles detailed and
complex passages without becoming confused and congested. The speaker
is very dynamic when driven by the appropriate amplifier - high current
capability is a must and amplifiers of over 100 watts a channel at 4
ohms or less may be acceptable. My HK Citation II sadly doesn't cut it,
but the modified Phase-Linear DRS-900 I talked about in an earlier
letter does a very good job. I'm in the process of designing a mosfet/
tube hybrid power amplifier for these and other low impedance planar
loudspeakers. Placement is rather critical and I've found that these
speakers must be kept well away from the walls and corners to prevent
serious interaction between the front and rear radiation from the
dipole. ( I.E. Low frequency cancelation and early reflections. ) I'm
rather pleased overall, and am rediscovering a lot of my recordings.
I have found that bypassing the fuse improves the sound slightly, but I
don't recommend this if you like your music really LOUD or if you have
ANY question about the dc stability of your amplifiers! CAVEAT!!
A friend of mine recently brought his Counterpoint SA-12 power amp.
for me to listen to. I was surprised by its fairly warm, open sound and
its ability to drive the Magnepans fairly well. Its one shortcoming is
its rather high output impedance (0.9 ohms) or low damping factor which
results in somewhat soft rounded bass response with some speakers. Over
-all loop feedback is not employed, instead the vacuum tube voltage
amplifiers utilize overall feedback and the output stage operates
without feedback. Counterpoint claims that any reactive load can be
driven and I suspect that it would make a good match with the
Quad ESL-63 and U.S Pro-monitor.
I recently purchased a Finyl CD kit to find out whether it actually
does anything audible to the sound of CD's. The consensus of all five
listeners involved over the last few weeks is that it subtly improves
the level of ambience and low level detail and in addition almost
completely removes a very slight sibilence on voices and a slight edge
heard on some CD's. There really isn't any scientifically valid reason
that I am aware of as to why this treatment should have any audible
effects, but it does seem to do what is claimed for it...
For those of you embroiled in the controversy over absolute
polarity I refer you to a little known book by R.C. Johnsen and
entitled "The Wood Effect" available from: The Modern Audio Association,
23 Stillings St., Boston, Ma. 02210. Cost is $9.00 including shipping
and handling. Usual disclaimer: I have no connection commercially with
the Association and am not even a member.. I think you'll find the book
interesting, informative and thought provoking. I thoroughly enjoyed my
copy. Check it out.....
Kevin Kennedy