Marantz CD40 NOS question

[MaccaAu]

:violin: Listening to my modded CD40 atm, done the NOS wiring but not sure how to solder the 14 decouping caps on the TDA1541A? do i desolder (remove a little solder first) on the smd or just solder it to the top of the smd?

Sounds awesome :D nice bass and detail
All Elna SimicII except the large 6800uf is a 6800uf 50v Elna Tonerex. Furtech RCA, 24awg silver wiring to RCA. Opamps - lme49720. Rubber mat above mech. Blutac around clock
http://i63.tinypic.com/2a612kg.jpg
http://i66.tinypic.com/14azcsp.jpg

[Light Dependant Resistor]

Hi
To do this de solder using solder wick, applying solder to the
solder wick as you go to wet it. I would use replacement SMD capacitors,
There are slightly different values of cap needed on a few of the pins,
you need to look up these values.

Here is an image of the job done neatly with SMD, compare it to others that
end up a mess. 17246

http://lampizator.eu/LAMPIZATOR/TDA1541%20corner/TDA1541.html
17247

Cheers / Chris

[MaccaAu]

Hi Chris
Thanks so those smds are different values. i can fit more at the bottom of a cd40 than cd50, more room to fit caps. Lampizator seemed to keep his smds in place. There would be some good smds now days to relace the smds.

[Light Dependant Resistor]

Hi Sam
There is some optimization of this area, Philips originally fitted 100n ( 104) caps all SMD
but are capacitors the best part ?, or a part they found would work in place of doing more
research ?. It would suggest either bipolar transistors, or even fets may be better. I have
many years ago tried diodes, but now have much better skill with SMD parts. The
description below is quite complex ( as you can see ) and has far too many
dependencies on other circuitry, being added , but not necessarily related to the DAC itself,
for my liking. Needs a bit more research,

Cheers / Chris

http://www.dutchaudioclassics.nl/philips-tda1541.asp
To switch the binary weighted currents to the output line of the D/A converter, three different types of switches are used depending on the value of the bit currents to be switched. To avoid differences in base current losses owing to the different bit currents, the six most significant bits are switched with a fast diode-transistor switch, as is shown in Fig. 4. The diode-transistor switch is controlled by data latches and driven by a differential amplifier. At the emitter node of the switch a voltage swing of half the collector swing is present. To avoid long settling times due to the parasitic load Zout, a cascode stage is added. To further minimize this parasitic load and to preserve the current generation network from switching transients, an extra cascode stage is added. The next four bit currents are switched with compensated diode-transistor switches, as shown in Fig. 5. This compensation is added to cancel the voltage swing at the current source connection which causes long settling times as these bit currents are small to discharge the parasitic capacitors. When the bit current is drained to Vref, an extra current Icomp is added to the current source connection and this causes an extra voltage drop over the resistor R, which cancels the voltage swing at the emitter node. Furthermore, a cascode stage is added to minimize the influence of the remaining voltage swing across the parasitic load, which is mainly the collector–substrate capacitance of the passive divider.

[Yomanze]

Don't mess with changing those TDA1541A caps... the PCB is way too fragile and you *will* lift tracks. They're only really suitable to change when they're through-hole versions.

Also, they're nice and close to the chip pins as they are.

[Yomanze]

Hi Sam
There is some optimization of this area, Philips originally fitted 100n ( 104) caps all SMD
but are capacitors the best part ?, or a part they found would work in place of doing more
research ?. It would suggest either bipolar transistors, or even fets may be better. I have
many years ago tried diodes, but now have much better skill with SMD parts. The
description below is quite complex ( as you can see ) and has far too many
dependencies on other circuitry, being added , but not necessarily related to the DAC itself,
for my liking. Needs a bit more research,

Cheers / Chris

http://www.dutchaudioclassics.nl/philips-tda1541.asp
To switch the binary weighted currents to the output line of the D/A converter, three different types of switches are used depending on the value of the bit currents to be switched. To avoid differences in base current losses owing to the different bit currents, the six most significant bits are switched with a fast diode-transistor switch, as is shown in Fig. 4. The diode-transistor switch is controlled by data latches and driven by a differential amplifier. At the emitter node of the switch a voltage swing of half the collector swing is present. To avoid long settling times due to the parasitic load Zout, a cascode stage is added. To further minimize this parasitic load and to preserve the current generation network from switching transients, an extra cascode stage is added. The next four bit currents are switched with compensated diode-transistor switches, as shown in Fig. 5. This compensation is added to cancel the voltage swing at the current source connection which causes long settling times as these bit currents are small to discharge the parasitic capacitors. When the bit current is drained to Vref, an extra current Icomp is added to the current source connection and this causes an extra voltage drop over the resistor R, which cancels the voltage swing at the emitter node. Furthermore, a cascode stage is added to minimize the influence of the remaining voltage swing across the parasitic load, which is mainly the collector–substrate capacitance of the passive divider.

This is the optimum for the TDA1541A (super tight cap placement, and bigger caps on the MSBs):

http://i1092.photobucket.com/albums/i405/neil_yeomans/audial2_zps26193523.jpg

[MaccaAu]

Hi Sam
There is some optimization of this area, Philips originally fitted 100n ( 104) caps all SMD
but are capacitors the best part ?, or a part they found would work in place of doing more
research ?. It would suggest either bipolar transistors, or even fets may be better. I have
many years ago tried diodes, but now have much better skill with SMD parts. The
description below is quite complex ( as you can see ) and has far too many
dependencies on other circuitry, being added , but not necessarily related to the DAC itself,
for my liking. Needs a bit more research,

Cheers / Chris

http://www.dutchaudioclassics.nl/philips-tda1541.asp
To switch the binary weighted currents to the output line of the D/A converter, three different types of switches are used depending on the value of the bit currents to be switched. To avoid differences in base current losses owing to the different bit currents, the six most significant bits are switched with a fast diode-transistor switch, as is shown in Fig. 4. The diode-transistor switch is controlled by data latches and driven by a differential amplifier. At the emitter node of the switch a voltage swing of half the collector swing is present. To avoid long settling times due to the parasitic load Zout, a cascode stage is added. To further minimize this parasitic load and to preserve the current generation network from switching transients, an extra cascode stage is added. The next four bit currents are switched with compensated diode-transistor switches, as shown in Fig. 5. This compensation is added to cancel the voltage swing at the current source connection which causes long settling times as these bit currents are small to discharge the parasitic capacitors. When the bit current is drained to Vref, an extra current Icomp is added to the current source connection and this causes an extra voltage drop over the resistor R, which cancels the voltage swing at the emitter node. Furthermore, a cascode stage is added to minimize the influence of the remaining voltage swing across the parasitic load, which is mainly the collector–substrate capacitance of the passive divider.


Hi Chris
Thanks that is very detailed information about the TDA, so much to take in, in the read. There is still some new old stock TDAs from that website, they are the chinese made ones.

SMDs and I are not very good atm, had trouble desolding them and also soldering them, they are so tiny especially the opamps. I removed the mutting transistors from the CD40, they looked more like caps near the bi-polars on the output. I am happy how it sounds, maybe someday when my skill with smds is better I can think of fixing it.

Don't mess with changing those TDA1541A caps... the PCB is way too fragile and you *will* lift tracks. They're only really suitable to change when they're through-hole versions.

Also, they're nice and close to the chip pins as they are.

Hi Neil,
Ive done the NOS wiring, so best I leave the smds then, already lifted some tracks and had to bridge them with wire, so also worried about too much heat on the TDA also with soldering.