SAA7220 + TDA1541 (comment and questions)

[13mh13]

Comment:
A dynamic duo ... this combo still impresses me with its classic multibit Philips sound. I do, however, prefer the combo in its default milieu: the Philips (or Philips-based) CDP, with the CDM mech, the SAA7x10 decoder, etc. Vintage Creek, Arcam, Naim -- and here in the US, modified Magnavoxes -- hold their own for 16/44.1, even today.

Questions:
In this 2007 DIYA post, Martin noted:

One more little thing - for chips designed to work together - they don't interface very well without a bit of work! Find the long 'TDA1541 thread in this forum of more details, but the key tweak is to use RC decoupling in the signal lines between these two chips to reduce HF noise injection into the dacs substrate (1K/10pF was suggested)*. Your Arcam already has some resistors in place in these lines, so definitely add small caps (10-22pF) to digital ground at the 1541 input pins. It helps a surprising amount.

Martin (or anyone)...I assume you meant the small cap (to ground) comes after the in-line resistor? Or does it matter?
How about the three I2S lines between SAA7x10 and SAA7220 -- any similar RC decoupling needed?

Thanks!

 

[martin clark]

Good heven's that's a while ago! and My CD2 is still runnng like that...

Try it; yes, tiny cap, 10pf to ground plane after the resistor, i.e. tda15xx input pin to 0v plane as close as poss. On data and latch enable, leave clock line alone; just add say 100r in series there.

 

[13mh13]

Try it; yes, tiny cap, 10pf to ground plane after the resistor, i.e. tda15xx input pin to 0v plane as close as poss. On data and latch enable, leave clock line alone; just add say 100r in series there.

The Arcam 5 CDP uses:

DATA: 390R
BCK: 120R
WS: 390R
... with no caps.
[I don't have an Arcam; only Philips and Magnavox mods.]
Is it a matter of tweaking with a 'scope ... plugging-n-chugging values until the signal looks clean?

BTW: About that modded CD2 ... I'm sure you've had some pretty decent DACs/CDPs pass thru your system ... so how does it (sonically) still hold up for 16/44.1?

 

[martin clark]

Actually, for Arcam Alpha5, ask 'MikeP' here: I suggested similar+ several related mods to him over on zerogain , as-was, some several years (nearly a decade!) ago, and he ran with them.

For myself - oh, yes, I've several alternatives, but for the one-box /play a disc/relax approach - still happy with my take on the CD2. Maybe I'm easily pleased, who knows...

 

[davidsrsb]

On the BCK line a low resistor value might be removing edge ringing. Getting a clean clock edge with no overshoot or doubling is quite hard, especially on single layer boards

 

[Mike P]

I just had a read through my Arcam Alpha 5 notes and I'm pretty sure I used 5.6pF NPO caps on the DATA and WS lines only.

More recently I did a similar mod to a Sony CDP-337ESD (see post #16 here):

https://pinkfishmedia.net/forum/threads/sony-337esd-mods.180202/

PS: The spec of this player is now a bit different to how it was when this thread ended. The big silly coupling caps have gone now and I finally settled on the original JRC5532DD opamps too!

 

[Yomanze]

Have you tried the old Signetics NE5532N or variants like Signetics NE5532AFE? These are very highly rated. Audio Jade on eBay are selling some authentic ones.

 

[Mike P]

Have you tried the old Signetics NE5532N or variants like Signetics NE5532AFE? These are very highly rated. Audio Jade on eBay are selling some authentic ones.

I've tried Signetics NE5532AN, Philips NE5532N and Texas NE5532P. So far the JRC5532DD are my favourites. I haven't tried the ceramic package NE5532AFE.

 

[13mh13]

Thx for the feedback, folks.

A bit OT, but I'll ask everyone reading this the same generic question I posed to Martin:

I'm sure you've had some pretty decent DACs/CDPs pass thru your system over the years ... so how does the classic SAA7220/TDA1541(A) still sonically hold up for 16/44.1?

 

[13mh13]

Getting a clean clock edge with no overshoot or doubling is quite hard, especially on single layer boards

I forgot if the copper (top) "shield" layer on the component side --which is ground -- qualifies as 2nd layer. Have a look at my CDB473 ...

 

[davidsrsb]

That copper layer looks like it is made as a floating shield. I don't see connections to it, so the ICs are not using it as a ground reference.
Not a very effective way of educing noise.

 

[13mh13]

That copper layer looks like it is made as a floating shield. I don't see connections to it, so the ICs are not using it as a ground reference.
Not a very effective way of reducing noise.

This species of copper shield PCB is used in several Philips-based CDPs of the late-1980s. The shield is grounded to electronic devices. It is a ground plane. Moreover, it's done well: digital and analog are common (= non-split ground plane).
http://www.tentlabs.com/Components/Shuntcomp/assets/Supply_decoupling.pdf#page=5

 

[Dowser]

Thx for the feedback, folks.

A bit OT, but I'll ask everyone reading this the same generic question I posed to Martin:

I'm sure you've had some pretty decent DACs/CDPs pass thru your system over the years ... so how does the classic SAA7220/TDA1541(A) still sonically hold up for 16/44.1?

I have had a few pass through my hands - currently still have 2 Naim CDIs and a Woodbridge WS3. I prefer the sound of this combo, although also spent a lot of time trying to get a Marantz CD60 to sound as good with heavy modding and failed. CDI with Flea is still best CD sound I have heard.

 

[13mh13]

I have had a few pass through my hands - currently still have 2 Naim CDIs and a Woodbridge WS3. I prefer the sound of this combo, although also spent a lot of time trying to get a Marantz CD60 to sound as good with heavy modding and failed. CDI with Flea is still best CD sound I have heard.

I have a Philips CD60 (exactly the same model as the Marantz CD60) which was a North America-only model. I, too heavily modded this, but could not get it to sound as good as my modded CD650. It may be the 650's superior disk-spin motor (Hall-effect, not a "toy" motor of CDM-4/19). Or it may be the larger xformer.
I recall Stereophile didn't like the stock Naim CD1 too much [review not yet online], tho' they totally dug the CDPs that came after: CD2, CDX. etc. Ditto glowing reviews of SAA7220/TDA1541A MSB player and Creek CD60.

 

[13mh13]

Good heven's that's a while ago! and My CD2 is still runnng like that...

Try it; yes, tiny cap, 10pf to ground plane after the resistor, i.e. tda15xx input pin to 0v plane as close as poss. On data and latch enable, leave clock line alone; just add say 100r in series there.

For the cap, I found the connection to ground to be a make-or-break ... literally. I lost all signal (no audio output!) when connecting cap to nearest convenient ground. Removed caps (just kept Rs) -- music back! Hmm ... let's try adding caps back, but grounding right to pin 14 on 1541 (dig. gnd.). Music with, I think, improved fidelity.