Thats pretty good Matthieu and thats without the DAC7 (TDA1547)!!!!
There's loads you can do there too. Multiple 5v feeds and bypassing the internal output stage on the DAC! You'll be busy for sure
There's loads you can do there too. Multiple 5v feeds and bypassing the internal output stage on the DAC! You'll be busy for sure
Actually I quite like a modified CD17, but others have said the SAA7350 DAC (oops, not 1547) is better on its own. And I certainly find the CD-42 sound very enjoyable...
You can transplant your DOS onto the tda1547 output Matthieu, bypassing the internal dac opamps. That will really let it it sing.
If you'd like some info, just PM me.
Cheers, Lee.
If you'd like some info, just PM me.
Cheers, Lee.
Indeed! Bypass those on board opamps with the DOS and it will be excellent!
My original philips CD850MKII that I had from new used the bitstream conversion SAA7350 that works before the DAC7 but sadly no DAC7 🙁. I've also modified a Teac VRDS-10 which uses the same chipset (SAA7350 followed by DAC7) and this player is pretty good to start with much similar to a CD17 but with a better transport.
It is def my opinion that the DAC7 after the 7350 is an awesome combination (much better than the 7350 on its own). I've had my eye out for a cheap CD950 (and I think 940 is the same) for a while. You'll def have fun Matthieu! 🙂
My original philips CD850MKII that I had from new used the bitstream conversion SAA7350 that works before the DAC7 but sadly no DAC7 🙁. I've also modified a Teac VRDS-10 which uses the same chipset (SAA7350 followed by DAC7) and this player is pretty good to start with much similar to a CD17 but with a better transport.
It is def my opinion that the DAC7 after the 7350 is an awesome combination (much better than the 7350 on its own
). I've had my eye out for a cheap CD950 (and I think 940 is the same) for a while. You'll def have fun Matthieu! 🙂
Well guys,
I was a bit reading and looking at the FSM but I see you know that player already 😉
Some ideas of many 5Vs (a simple & clean way like linked, and wood style to help that ugly guy to look better) and just the first half dual op amps, wondering if pins linked to before internal op amps can be used to avoid them... seems you wanna make me move my DOS in this one! Men I'm just scared I've built my CD53 for nothing, meaning that Philips or the Xmas' CD40 will make it... less attractive soudwise, or not. (I've spent soo much time on doing test board DOS... not again... oh no... )
I'll make a thread for it, Lee's help or any input will be welcome as usual.
Enough of out of topic, sorry Simon 😉
Matthieu
I was a bit reading and looking at the FSM but I see you know that player already 😉
Some ideas of many 5Vs (a simple & clean way like linked, and wood style to help that ugly guy to look better) and just the first half dual op amps, wondering if pins linked to before internal op amps can be used to avoid them... seems you wanna make me move my DOS in this one! Men I'm just scared I've built my CD53 for nothing, meaning that Philips or the Xmas' CD40 will make it... less attractive soudwise, or not. (I've spent soo much time on doing test board DOS... not again... oh no... )
I'll make a thread for it, Lee's help or any input will be welcome as usual.
Enough of out of topic, sorry Simon 😉
Matthieu
I have a CD940 (and a CD950 for spares). I just use it as a transport to feed my TDA1541A. All the non essential stages have had the power removed
Stock, I admit it did sound pretty good actually.
I got it because it was a CDM9 - and I thought that would be a reasonably good transport.
Stock, I admit it did sound pretty good actually.
I got it because it was a CDM9 - and I thought that would be a reasonably good transport.
I've seen your topic 😉
A blue star in? Even standard spec ones may outperform our beloved NPC... I don't know why but I'm not ready to hard wire my DOS in my CD-53 and want to leave the opamp parts in case...
http://www.marantzphilips.nl/philips_tda1547/
A blue star in? Even standard spec ones may outperform our beloved NPC... I don't know why but I'm not ready to hard wire my DOS in my CD-53 and want to leave the opamp parts in case...
http://www.marantzphilips.nl/philips_tda1547/
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How to get 0v DC on the output!
Attached diagram of my output stage. The 5k variable resistors replaced fixed 2k7's. I used 20 turn pots for accuraccy. With the player fully warmed up and the disk stopped, I tuned the pots to give me as close as poss to 0v. Once warm I can get it stable at about 3mV.
No output caps has dropped freq response through the floor. The sound is fuller and defiantely more dynamic. The sound is punchy and tight and silky smooth at the top. Anyone with output caps due to DC on the output should look at tying into +v rail into the DAC out and I can definately say simple is better here!😀
Attached diagram of my output stage. The 5k variable resistors replaced fixed 2k7's. I used 20 turn pots for accuraccy. With the player fully warmed up and the disk stopped, I tuned the pots to give me as close as poss to 0v. Once warm I can get it stable at about 3mV.
No output caps has dropped freq response through the floor. The sound is fuller and defiantely more dynamic. The sound is punchy and tight and silky smooth at the top. Anyone with output caps due to DC on the output should look at tying into +v rail into the DAC out and I can definately say simple is better here!😀
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Try adding a small cap (1-10uF or more) from the junction of your two resistors to ground, it'll filter off PSU noise.
Or replace the trimpot with a small trimmable current-source instead and you'll get more of the same again.
So long as your raw supply is quiet,the simple resistor approach does indeed work quite well to inject 2mA and do away with the DC offset - much better than it does for biasing an opamp output stage for example, because the output of this dac is 0v by definition. IOW there is no voltage swing across the resistor and therefore, no current swing through it. But it appears in parallel with the dacs output as a load on the I/V stage signal current. A small error term.
The CCS has *much* higher dynamic impedance and therefore freedom from PSU interference and the loading effect 🙂
Or replace the trimpot with a small trimmable current-source instead and you'll get more of the same again.
So long as your raw supply is quiet,the simple resistor approach does indeed work quite well to inject 2mA and do away with the DC offset - much better than it does for biasing an opamp output stage for example, because the output of this dac is 0v by definition. IOW there is no voltage swing across the resistor and therefore, no current swing through it. But it appears in parallel with the dacs output as a load on the I/V stage signal current. A small error term.
The CCS has *much* higher dynamic impedance and therefore freedom from PSU interference and the loading effect 🙂
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Hi Martin, there was 10uF to gnd between the 2 r's in the original circuit. These were removed months ago although I cannot remember why!?!?!😕 Would you use there? elco's came out!
Can you confirm what you mean by trimmable current source? and also CCS!
I might be having a blonde day
Thanks Ian
Edit: yep def blonde! Constant current supply??
Can you confirm what you mean by trimmable current source? and also CCS!
I might be having a blonde day
Thanks Ian
Edit: yep def blonde! Constant current supply??
Any preference on cap type here? Would it be better fed from its own +12v SPower and then not use a cap at all or both??
Do you have any pointers on a better circuit?
Ian
That cap was originally a 10uF Cerafine Ian. I snipped mine out and the sound-quality improved dramatically, really opening up the treble. I have a feeling then, that a really high quality cap is needed.
Lee.
Lee.
Or a "no/low" noise powersupply then there wouldn't be any noise to filter off?
SPower maybe?
Simple adjustable CCS for experimental purposes - remove the fixed and adjustable resistors, replace with a jfet with a trimpot between Gate and source. Say BF245C with a 2k trimpot, connect the Drain to your +ve rail, and the jfet gate to the Dac current output. Twiddle the trimpot to set current (start with it mid-span). It'll probably drift a little from switch-on / be a bit sensitive to adjustment, but that doesn't matter much so long as DC offset stays under 10-20mV. It will have a dynamic impedance rather higher than the resistor array - up around 100Kohm.
Amongst other things, yes. A bit more elaborate in this case.
Note that jfet -based CCS are by no means perfect, or even particularly high impedance compared with simple BJT-based ideas, but this is at least and order of magnitude better than the resistor method. Do be aware this simple CCS needs at least 9-10v across it for best performance - not a problem in this case.
Note that jfet -based CCS are by no means perfect, or even particularly high impedance compared with simple BJT-based ideas, but this is at least and order of magnitude better than the resistor method. Do be aware this simple CCS needs at least 9-10v across it for best performance - not a problem in this case.
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