I'm looking at the CD160 SM at the moment. I don't quite see the point of making a new PCB just to power up the opamps. From what I see you are still using the components from the main pcb. Why not just disconnect the 100 ohm resistors in the opamp's supply rails and wire the new PSU there? By the way, try OPA227 instead of 2134 
It fits in that place quite well.
Regards,
Venci
It fits in that place quite well. Regards,
Venci
You're right of course - I could just wire the PSU in, but putting the output stage on it's own board gives me two things; I can play around with it (I can switch the whole stage out and change components, like the cap value mentioned earlier), and it means I bypass all the De-emphasis circuitry.
I'm only using the 134's as I have them but I'll see if I can get some samples of the 227's.
Cheers, Josh
I'm only using the 134's as I have them but I'll see if I can get some samples of the 227's.
Cheers, Josh
After all that, the SAA7220/B arrived today so I've put that in (no socket). Haven't had a proper listen yet but it's sounding pretty good so far - if pushed I'd say a little bit more detailed and a touch more realistic - but it's not ground breaking. In keeping with my scientific approach(!) I also changed the DAC decoupling caps at the same time. So...onto the output stage, still tweaking the layout but I might etch them tomorrow.
Cheers, Josh.
Cheers, Josh.
A quick update as it's been a while! Following a few 'school boy errors' I finally have a populated op-amp board (opa227 samples arrived) and an etched and part-drilled PSU board. I've found a transformer with 9v and 15v secondaries that should be ok for the SAA & output stage so I should have the PSU finished over the weekend - I got some 3*7's in the end (splashing out on this now!). I also have a discreet output stage in the works (I'm really struggling with the board layout though) so some 'trials' are on the way.
It's all gone a bit 'off-topic' this thread! Maybe I should start afresh with pics once the output stage is complete.
Cheers, Josh
It's all gone a bit 'off-topic' this thread! Maybe I should start afresh with pics once the output stage is complete.
Cheers, Josh
Is that a bad idea? It's only to save space so if there's gains to be had using dedicated ones then that's what I'll do (I'm ultimately going to have to extend the chassis anyway). I didn't realise that the DF and output stage could interfere with each other as 'far back' (technical term!) as the transformer.
Well - an eventful day! I decided in the end to power the 'modular' output stage from the onboard PSU, from what I've read op-amps are fairly resilient to noise on the PSU so I concentrated my efforts on improving the PSU for the filter instead. I'd originally built a quick one using a 7805 to test, I've since built a two stage PSU around the 317. The first stage drops the 15V AC to about 8V (it's a bit hot though), the second stage - mounted right next to the filter uses another 317 to drop it further to the 5v required.
The op-amp stage is running opa227's, I had originally decoupled each supply to ground and used a 2.2n feedback cap. This sounded ok, but no real improvement. I've just removed the feedback cap and decoupled the supply's to each other instead, the whole thing is much improved (i think!), super detailed & solid bass. (no doubt more to come with a decent output stage).....
....Next up then is a discreet output stage, the PASS D1 looks good but I can't find a transformer to get the required 30v supply. The Fetishizator is another possibility but do I need to worry about 700Mhz+ reaching my tweeters? So that leaves this one!
Lessons learned today......make the pads for screw terminals as big as possible on your PCB's because the ****** things 'twist out' and you end up spending hours 'debugging' a very simple PSU ;o)
And....erm... make sure you plug the RCA's back in so you don't waste even more hours 'debugging' the whole **** cd player ;o))
Cheers for all your input, Josh
The op-amp stage is running opa227's, I had originally decoupled each supply to ground and used a 2.2n feedback cap. This sounded ok, but no real improvement. I've just removed the feedback cap and decoupled the supply's to each other instead, the whole thing is much improved (i think!), super detailed & solid bass. (no doubt more to come with a decent output stage).....
....Next up then is a discreet output stage, the PASS D1 looks good but I can't find a transformer to get the required 30v supply. The Fetishizator is another possibility but do I need to worry about 700Mhz+ reaching my tweeters? So that leaves this one!
Lessons learned today......make the pads for screw terminals as big as possible on your PCB's because the ****** things 'twist out' and you end up spending hours 'debugging' a very simple PSU ;o)
And....erm... make sure you plug the RCA's back in so you don't waste even more hours 'debugging' the whole **** cd player ;o))
Cheers for all your input, Josh
This one is a rather odd circuit. It will sound a bit tube like. I'd definitely put some sort of filtering to limit the bandwidth.
Regards,
Venci
Long time no update! Been a bit busy at work (
To summarise, the 160 now has a SAA7220B & TDA1541A, a second transformer feeding an LM317 based pre-reg followed by 2 x +5v LM317 psu's for the decoders. The output stage is still op-amp based (i know i know), but with 4xsingle OPA227's in the simplest i/v & buffer configuration I could muster.
I have all the parts for the 'rather odd' output stage so that's next, oh and I caved in and splashed out £30.00 for the clock mentioned earlier but it could be a while before it lands on these shores.
The dedicated PSU's have made a massive difference! Initially I 'forgot' to bypass the resistors on the ADJ legs of the 317's and still sounded incredible but it's in another league with the bypass caps in place. Very refined and controlled I think but the detail is amazing, on Beirut's 'The Rip Tide' I swear I can hear them shuffling paper and picking up instruments (or maybe I've gone a bit crazy).
The new output stage will require it's own PSU so that's on the bench and I may well build one for the DAC itself while I'm there (although there's not a great deal else on the -ve supplies, the +5v is still being used in the rest of the player).
I haven't figured out how to implement the clock yet but it will sink in eventually!
Cheers
PS - Any recommendations for the bandwidth filter on that output stage?
(To summarise, the 160 now has a SAA7220B & TDA1541A, a second transformer feeding an LM317 based pre-reg followed by 2 x +5v LM317 psu's for the decoders. The output stage is still op-amp based (i know i know), but with 4xsingle OPA227's in the simplest i/v & buffer configuration I could muster.
I have all the parts for the 'rather odd' output stage so that's next, oh and I caved in and splashed out £30.00 for the clock mentioned earlier but it could be a while before it lands on these shores.
The dedicated PSU's have made a massive difference! Initially I 'forgot' to bypass the resistors on the ADJ legs of the 317's and still sounded incredible but it's in another league with the bypass caps in place. Very refined and controlled I think but the detail is amazing, on Beirut's 'The Rip Tide' I swear I can hear them shuffling paper and picking up instruments (or maybe I've gone a bit crazy).
The new output stage will require it's own PSU so that's on the bench and I may well build one for the DAC itself while I'm there (although there's not a great deal else on the -ve supplies, the +5v is still being used in the rest of the player).
I haven't figured out how to implement the clock yet but it will sink in eventually!
Cheers
PS - Any recommendations for the bandwidth filter on that output stage?
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A simple filter would do the job. Just use a small capacitor from the MOSFET's gate to ground. 220pF is quite enough.
Cheers guys - The clock is great!
I forgot to mention on the previous post that I had performed the Grundig 9009 DEM reclock mod, cap on pin 17, connected to VDD2, diode to pin 16, another cap from here, via a resister to WS.
Now this mod was working great, no locking problems, everything ok.
I've since done the clock upgrade as follows;
x1 to the 7210 and 7220
x1 to pin 4 of the TDA
/2 to pin 2 of the TDA
Initially all was well - sounds fantastic, I've wasted most of my descriptive words on previous mods I'm afraid but it's now in a 'different league?' again!
However, i now get jumps, the cd plays ok for maybe 15-20 seconds, then a quick 'jumble of sound' (like scratching a record back) then carries on ok again.
I think I'm approaching the limits of that DEM reclock, I read in the 'ultimate TDA' thread that I might get locking problems from the DEM if clocked to high, I'm still using WS though so no change in frequency, I may have an 'implementation' issue that's only now starting to show up though.
I'm going to drop the DEM mod and see if that improves things, if it does I'll adopt a different approach.
Any thoughts would be very much appreciated!
Josh
I forgot to mention on the previous post that I had performed the Grundig 9009 DEM reclock mod, cap on pin 17, connected to VDD2, diode to pin 16, another cap from here, via a resister to WS.
Now this mod was working great, no locking problems, everything ok.
I've since done the clock upgrade as follows;
x1 to the 7210 and 7220
x1 to pin 4 of the TDA
/2 to pin 2 of the TDA
Initially all was well - sounds fantastic, I've wasted most of my descriptive words on previous mods I'm afraid but it's now in a 'different league?' again!
However, i now get jumps, the cd plays ok for maybe 15-20 seconds, then a quick 'jumble of sound' (like scratching a record back) then carries on ok again.
I think I'm approaching the limits of that DEM reclock, I read in the 'ultimate TDA' thread that I might get locking problems from the DEM if clocked to high, I'm still using WS though so no change in frequency, I may have an 'implementation' issue that's only now starting to show up though.
I'm going to drop the DEM mod and see if that improves things, if it does I'll adopt a different approach.
Any thoughts would be very much appreciated!
Josh
The quick fix alternative is to get a tight tolerance silver mica cap ( !% or 2% at worst ) of 250 pf and put that across pin 16 and 17.
We all did it with our Alpha's and got a noticeable gain.
It doesn't match the full DEM job but it sure as hell is a simple upgrade.
Or what about a 25v oscon across the -5 and -15 v pins ?
Tried that yet ?
We all did it with our Alpha's and got a noticeable gain.
It doesn't match the full DEM job but it sure as hell is a simple upgrade.
Or what about a 25v oscon across the -5 and -15 v pins ?
Tried that yet ?
When I pulled the DEM reclock I couldn't find a small enough cap to try but I'll have another rummage. I also have a 2.8 feed from the clock so I could try that also - IIRC and I have to invert it for the other pin, I think I have the bits for this. Not tried the cap across the -5 and -15v pins yet - I'm still playing catch up on the various threads about modding these players - seems like an easy enough tweak though, back to the reading!
Very happy at the moment though! Honestly, to look at it it's a miracle it works at all!
Very happy at the moment though! Honestly, to look at it it's a miracle it works at all!
Hi, I built the basic lampizator with the j-fets and it's pretty good (i think)! I also applied the filters, so far so good.
But - I couldn't find a 250p cap of that tolerance so I tried the DEM clock mod again with the diode, resister and pair of caps. Now I think I broken something (it was going to happen sooner or later!).
All I get is a whine from the player, nothing else (noisy at first but then clears up), no music at all. Swapped the output stage, no joy. Reverted to the cap on the DEM, again no joy. If I disconnect the /2 to WS I get silence but that's as far as I've got.
Any thoughts very much appreciated!!
But - I couldn't find a 250p cap of that tolerance so I tried the DEM clock mod again with the diode, resister and pair of caps. Now I think I broken something (it was going to happen sooner or later!).
All I get is a whine from the player, nothing else (noisy at first but then clears up), no music at all. Swapped the output stage, no joy. Reverted to the cap on the DEM, again no joy. If I disconnect the /2 to WS I get silence but that's as far as I've got.
Any thoughts very much appreciated!!
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