Sjöström Audio DIY forum

Well,
for starters, the Sony CDP-XA7 ES was one of the last Sony "high-end" CD players (available since 1995
up to 2005). It features a Bitstream DAC with internally balanced IO (although not taking fully advantage
of it in its original configuration). It also uses DC coupling in the output stage instead of a coupling capacitor.
(through an opamp based DC-Servo - OPA-27GP from Burr Brown, IC461/561) 

To follow this thread, the reader needs a Service Manual that can be obtained from various sources,
for example from www.manuals-in-pdf.com via direct .pdf download. 

Since the design is already high-quality (in typical Sony-ES series fashion), most of my
hints will involve merely chaning opamps to more current types, as there has been
TREMENDOUS progress in this field over the last decade with regard to noise immunity
(opamp voltage / current noise), output current capability, linearity and speed (slew rate, settling time).   

http://www.thevintageknob.org/SONY/sonyes/CDPXA7ES/CDPXA7ES.html
http://cdp101.hp.infoseek.co.jp/cdpxa7es/cdpxa7es.html
http://translate.google.com/translate?u=http%3A%2F%2Fcdp101.hp.infoseek.co.jp%2Fcdpxa7es%2Fcdpxa7es.html&langpair=ja%7Cen&hl=fr&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools

For most of the post-DAC filtering, the XA-7 ES originally relies on the AD-712. All these opamps are present  on the PCB as SMD types.
Note that the AD-712 is a FET opamp - in a dual opamp package. I found this puzzling as only the first stage after the DAC (labeled "de-emphasis" filter)
seems to require high-impedance (and hence a FET input opamp). Beyond that it appears to me that ordinary BJT opamps would do the job and provide
reduced noise and better sound also. Maybe back then only the AD-712 was available as an SMD chip.
Also present are NJM-2114D types in DIP package - I guess they are used where higher output current is required. Also, these are ordinary BJT opamps
(In the CDP-XA7 as Headphone driver and variable unbalanced output path amplifier). Essentially, they can be considerd "lower noise" NE-5532 replacement,
they calso can handle higher output current than the plain-vanilla NE-5532. The NJM-2114D are typically found in japanese Audio / Video gear and the
prefix "NJM" stands for "New Japan Radio Corp".
 
My plan is to get "optimal" state of the art opamp types in the audio signal path - for each of the functions the respective stage performs. So my gut feeling tells me
to minimize the parameters noise, "settling time", voltage and and maximize Slew Rate when possible. The problem is - what parameters take precedence in each function ?
 
IC-504, IC-404 ... OPA-27GP ... DC Servo - doesn't seem to require any change
 
IC-401,IC-501 (AD-712) post DAC Filter "De-Emphasis" handles balanced audio out from DAC.... appears to require High input Impedance
preference: replace with THS-4032  (dual type, BJT but 2MegOhm Rin, +/- 16V, 100Mhz, 1.6nV noise, 60ns settling time, 100V/µS slew, 2MegOhm Input Impedance, drives 90mA output, -90dB THD 1Mhz)
fallback: replace with AD8620 (dual type, slightly more noise, FET opamp, +/-13V max, 25Mhz, 6nV noise, 5fA noise, 600ns settling time, 50V/µS slew, THD 0,0006% 10kHz)
 
IC-402, IC-502 (AD-712) labeled "mix amp" (only 1 opamp of the dual AD-712 was used originally !) - makes single ended audio signal from balanced signal
replace with OPA211 (SiGe BJT opamp, +/- 18V, max. 80Mhz, 1.1nV noise, 1pA noise, 400ns settling time, 27V/µS slew rate, THD -136dB 1kHz)
     it appears to me that a BJT opamp can be used here to make the balanced signal single ended. Single type opamp possible since the original opamp used only one half od the dual AD712
     no need for a high-impedance opamp such a FET input opamp and the OPA211 should easily work here (not particulary demanding type wrt. oscilation)
 
IC-403,IC-503 (AD712) labeled "buffer" one for fixed out (appears to be I/V converter), another for Headphone stage
prefenence: replace with THS-4032  (dual type, BJT but 2MegOhm Rin, +/- 16V, 100Mhz, 1.6nV noise, 60ns settling time, 100V/µS slew, 2MegOhm Input Impedance, drives 90mA output, -90dB THD 1Mhz)
fallback: replace with AD8599 (dual type BJT, +/- 18V, 17Mhz, 1.1nV noise, 2000ns settling time, 17V/µS Slew, -120dB THD 1kHz) ... settling time a tad high, but a typical "audio friendly" opamp
 
IC-461, IC-561 ... (NJM-2114D) Preamp/Driver-Stage for Headphone Out and variable Out
preference: replace with THS-4031/32 (drives 90A, BJT but 2MegOhm Rin, +/- 16V, 100Mhz, 1.6nV noise, 60ns settling time, 100V/µS slew, 2MegOhm Input Impedance, drives 90mA output, -90dB THD 1Mhz)
fallback: replace with AD8599 (dual type BJT, +/- 18V, 17Mhz, 1.1nV noise, 2000ns settling time, 17V/µS Slew, 50mA output current, -120dB THD 1kHz)
           
IC-460, IC-560 (NJM-2114D) LowPass Filter for Balanced Out
preference : replace 2x AD8599 per channel with one OPA1632 and change the filter configuration accordingly (OPA-1632 is a fully balanced output opamp)
                  OPA1632 (full balanced audio output opamp, 1.3nV nosie, 50V/µS Slew, +/-16V, 150Mhz BW, 75ns settling time, THD 0,0000022%)
fallback: replace with AD8599 (dual type BJT, +/- 18V, 17Mhz, 1.1nV noise, 2000ns settling time, 17V/µS Slew, 50mA output current, -120dB THD 1kHz)
 
any input is much appreciated !
 
best rgrds from Vienna/Austria
Crossy