Conference hips::uk_audioo

    Found the number for Electramail - 0536 204555, they are the RS mail
    order section.

    Which part of the CD player are you modifying?
    
    Dave

    Dave,
    
    There are two opamps that respond well to replacement.  An LF353N right
    by the DAC chip, this does current to voltage conversion.  The other
    opamp is an NE5532N right by the analogue output.  Most Philips based
    players use these chips, even bitstream.  The AD712JN is a standard
    tweak in exchange for these opamps.  A newer chip is the AD827JN, this
    has a _very_ fast slew rate.  Some say it could go unstable if not
    designed into a circuit, but Walt Clark says it won't, I tend to
    believe Walt.
    
    Not sure if these chips speak French though :-)
    
    Suggest you look at note s 76.11 to 76.16 in AUDIO_ENGINEERING.
    
    Clive.

    Hi Clive,
    
    What sort of part expense and sound improvement are you expecting?
    I presume changing the parts will take you about an hour.
    
    Robert.

    Oh no! It's "take the lid off" time again already. Must have a look
    round inside the old Optic.
    
    How do I get into AUDIO_ENGINEERING? I don't seem to be able to open
    the conference. I have the nodename as DRIVEME::, is that correct?
    
    Dave

    Try DRIVME::AUDIO_ENGINEERING (you had a seven character nodename).
    
    Notes 76 and 30 are the interesting ones for this topic.  Meridian 
    suggest going for the conservative spec 712 chips for starters.  They 
    even seemed flexible over servicing modified kit if the mods are simple 
    chip swaps with identical pin-outs.

    Thanks Clive. I'll have a look in.
    
    Dave

We've just got the latest RS catalogue - they now take ACCESS/VISA etc over the
phone - no mention in the terms of business of the 'bona fide companies' etc, 
I guess they'll deal with anyone - but on a "trade" basis (with regard to Sale
 of Goods Act etc.)

Dave

    I have found that while generally good RS/Electromail don't always
    stock some of the more "Exotic" semiconductors. I have always found
    audiosynthesis (The people who do all the Ben Duncan projects as kits)
    to be pretty good . I got some high precsion Voltage references from
    them.
    
    The Best catalogue I've found is the STC components catalogue, which
    I'll bring in the number for. The down side is you have to often buy
    quite large numbers of things, but the seem to carry roughly 3 times
    the stock of RS. the also sell DECmates !!!!(Old catalogue)

    It took 2 hours to install the opamps, I had to cut the old ones out,
    remove the remains of the pins and then use a solder sucker to clear
    the holes of solder.
    
    It's very early to be definative yet as I should wait for 48 hours to
    allow the chips to burn in, but there is an improvement.  The obvious
    one is the bass, I can only describe it as "very convincing, without
    being over the top".
    
    I'll borrow an unmodified 206 from a friend and do a comparison
    sometime soon.
    
    In terms of burn in time, I'm lucky that my CD has a standby mode that
    leaves the DAC and analogue circuits powered up, switching off the
    laser circuitry.  I checked the supply pins on the opamps, just to be
    sure these continue to receive power.  One heck of a better than leaving
    a CD on repeat for 48 hours.   

I've now changed from AD712 to AD827, very different results from these
chips. The chip swaps relate to the current to voltage convertor opamp by the 
D to A chip and the output opamp on the analogue section. 

The AD 827 gives a far more natural tonal balance, the AD 712 being 
very detailed, but bright too.  The AD 712 tends to tear the music apart and 
make me analyse it along with the recording techniques.  Very impresive 
initially and certainly an improvement over LM 353 and NE5532, but a little
tough to live with without tailing off the HF a little.

The AD 827 is very detailed too, but it seems to integrate the music and 
make it very enjoyable.  

Bass and soundstaging is very good compared the standard cheepo chips.  Very 
happy with the changes.

I wasn't happy when I saw all the dual chips in my expensive CD player, I 
would much prefer dual mono, after all what's the cost of a few extra voltage 
stabilisers.
    

    I'm now into upgrading the power supply of my Linn LK1 preamp.  Having
    looked at a Dirak, it's very expensive for what it is and is also very
    badly implemented.
    
    I'll need a decent transformer at a realistic price, does anyone know 
    the phone number or address of Cotswold Transformers?