[GregS[_3_]]

In article , wrote:
On Dec 5, 2:22 pm, Chris Morriss wrote:
In message
,
writes

Hello all,
First, I like my 901s regardless so no flaming please.
I need help with this condition:
I have two sets of 901's. One pair of series IV and one pair of
series VI, both with the matching Bose EQ.

My problem is that some CD,s and even some passages on soother CD's
cause distortion when using the EQ. This can be at any volume level.
I have only had this problem with recent CDs. (Diana Krall, Chris
Botti) All my older CD's and the radio plays fine and loud. I have
tried different recievers, CD decks and even replaced all the caps in
one of the EQs. Anyone else having issues or know where I can find a
service manual for these EQ's?
Really appreciate the help

Perhaps the high output signal is overloading the input on the
equaliser. Can you make up a simple 6dB pad (a couple of 10k resistors
in an 'L' network for each channel)? This may drop the signal enough.
What is the input spec for the equaliser? Modern highly-compressed CDs
may be putting out 2V rms or so and that may be the problem.
--
Chris Morriss

Thanks for the help folks. Yes the problem seems to be on both
channels and I have tryed it on two different systems. I was
thinking to try attenuation as well. I have tried different CD
players and even drove the eq's input off of a portable cd deck
headphone jack with varied volume output and could detect the
distortion at very low levels. Does the RMS voltage value remain
constant on a headphone channel?

I don't know the input spec on the bose Eq but would apprecieate it
anyone has that information or a link to a service manual.

I can't belive that I am the only person haveing these issues or that
I have aquired two systems with the same problem.
A call to Bose says they will check out the EQ for 60 dollars. I
assume new systems they are selling have upgraded EQs. What are they
doing or changing?

Love the "hat" comment. I deserve it.
Thanks again,
Any other comments?

I would check the supply on the opamp pins. You need a diagram of the specific
chip. The should be at least 15 volts minimum between plus and minus up
to about 30 volts which is normally used. If you have a scope look for ripple.

I have seen a couple of models of the equalizer. Some seem outlandish
in their opperation. One, I could not reduce the treble enough.
The orginal model came out and the second model, a fully transistorized
unit had a little more selection than the first. After that they were chip opamps,
typically using TLO74's or TLO72's, can't remember. The first models escentially
mimicked the orginal, with even more boost selection, some uncontrolable.
After that, it seemed they were less concerned with the boost, but added
a type of midrange control. If you suck out the low mids, it would appear
to do the same thing as boost the treble and bass. Bose always says
they make improvements, like over a hundred improvements, more
like 100 cost saving features.

greg