Timbral accuracy of 1543

[analog_sa]

Over the last week or so i have experimented with a reasonably well built 1543 nos dac. Four independent PS, BG caps, no caps in front of the 8414. Ok, the regulators so far are quite basic - 317/78l05 types. The sound is in many ways impressive compared to my Cyrus dac - better bass, more air and space, better dynamics. Probably more extended on both sides.

But... there is something really wrong with the sound of well known instruments. Piano doesn't quite sound like a piano, the flute is almost unrecognisable; it sounds like the ratio between the fundamental tone and the harmonics is destroyed. It is not obvious with all types of music and it may not even be bothersome to all.

Is this a common trait of the 1543 or could it be specific to my implementation. Too many Black Gates perhaps? In comparison, the Cyrus uses horrendous tantalums everywhere but instruments have obviously more correct timbre.

I have read many times references to the 1543 'tonality' and how it takes time getting used to. Is this the same?

Thanks

[ThorstenL]

Konnichiwa,

Originally posted by analog_sa
Over the last week or so i have experimented with a reasonably well built 1543 nos dac. Four independent PS, BG caps,

The BG's hopefully N/NX/NXHiQ and not more generic stuff... ;-)

Originally posted by analog_sa
no caps in front of the 8414.

I don't think you can actually do that, sorry. The CS8414 Inputs must be biased to 2.5V, most digital outputs in players/transports are ground referenced.

You MUST have a way handeling the DC offset if the grounds are linked, that means either a transformer or capacitors.

Originally posted by analog_sa
But... there is something really wrong with the sound of well known instruments. Piano doesn't quite sound like a piano, the flute is almost unrecognisable; it sounds like the ratio between the fundamental tone and the harmonics is destroyed.

There seems to be something wrong then.

Originally posted by analog_sa
Is this a common trait of the 1543 or could it be specific to my implementation.

I find the 1543 to sound rather rough and forward, plus somewhat "simplyfying" and "generalising", but instruments remain well recognisable.

Sayonara

[analog_sa]

The CS8414 Inputs must be biased to 2.5V

I asked about it and how is it resolved in Kusunoki's dac in a separate thread. After not liking the 75179 i used a DS8923 line receiver/driver. The spdif is coupled differentially between the two inputs of the 8923 without a ground reference . The two outputs drive differentially the Rxp and Rxp on the 8414. Does changing the receiver's biasing bring any negative effects?

Regarding the tonality, the effect is probably subtler than 'unrecognizable' but sufficient even for my wife to notice it.

[ThorstenL]

Konnichiwa,

Originally posted by analog_sa
I asked about it and how is it resolved in Kusunoki's dac in a separate thread. After not liking the 75179 i used a DS8923 line receiver/driver. The spdif is coupled differentially between the two inputs of the 8923 without a ground reference . The two outputs drive differentially the Rxp and Rxp on the 8414. Does changing the receiver's biasing bring any negative effects?

If you drive the inputs from a TTL/CMOS output differentially you are fine, no worries there, BUT:

Originally posted by analog_sa
The spdif is coupled differentially between the two inputs of the 8923 without a ground reference .

Are you sure? No ground reference from the CD Drive? Nothing creeping in from the Amp backwards through the audio connections and the digital ground?

You may still find adding interface transformers or coupling cap's may be neccesary, in this case ahead of the receiver. It might work fine, but I'd just chack, in case....

I personally would have been highly unlikely to use an active reciever that offers no better performance that the build in one in the CS8412, a pair of capacitors or a Transformer seem much preferrable.....

Sayonara

[Peter Daniel]

You might be interested in reading this, regarding performance of TDA1543. While it was only an early prototype version, and later changes (especially changing bypasses structure, filtering arrangement, parts in PLL loop and input coupling) brought some improvements which addressed the noted shortcomings: http://www.6moons.com/audioreviews/audiozone2/zone.html
Check also the second-opinion commentary on the DAC, here: http://www.6moons.com/audioreviews/a...e2/zone_3.html

Just for comparison, the current version was posted here: http://www.diyaudio.com/forums/showt...425#post530425

[kittaylor]

Care to give a full decription of your dac, analog_sa? FLute sounds good on my 1543/8412 clone.

Bad decoupling cap choices can wreck the sound, and there's lots of potential for distortion in the TDA1543 resistor value.

[analog_sa]

Are you sure? No ground reference from the CD Drive? Nothing creeping in from the Amp backwards through the audio connections and the digital ground?

I wish i was sure All i can say is that i tried with and without caps at both positions - between the input receiver and the reansport and between the driver output and 8414. Removal of both caps brought an obvious improvement. Reliabilty, otoh, is likely compromised as the input of the ds8923 is pretty much at the mercy of whatever ground potential the transport floats at. Maybe a couple of zeners across the input will be wise.

Care to give a full decription of your dac,

I gladly will once it settles down a bit At present it's on three separate boards allowing for easier experiments. Grounding seems good but wiring length is obviously compromised. Regarding the decoupling, i've read all your adventures on pinkfish and thouroughly enjoyed them. My decoupling is simple but probably sufficient at this stage - 4u7 BGN and smd ceramic triplet on the 8414 pins. The 1543 didn't take well to ceramic decoupling so it's just a 4u7 BGN at present. Each PS has it's own transformer, rectifier and regulator - this made a huge improvement compared to a shared transformer.

[Peter Daniel]

What are you using for rectifiers?

[analog_sa]

the AZ's only tonal failings were a slight emphasis of sibilance on certain recordings and an equally slight perceptible thinning of instrumental and vocal timbres in the upper registers

Peter,

Thanks for the links. The above review is pretty much in line with my own perceptions. I still wonder to what extent is the 1543 responsible. In your experience is the 1541A better tonally?

[analog_sa]

What are you using for rectifiers?

MUR860. I had a recent distressing experience with those so maybe i should rethink their use.

My digital rig is in a different room from the analogue and i thought of having my old Dyna ST-70 perform amp duties in it. Not that it's such a great amp but it fits on the rack and it's happy driving the ProAc Studio 150.

While checking the Dyna general health i thought it would be great to swap the ancient selenium rectifier in the bias supply to MUR860. The result wasn't pretty. I never knew selenium was supposed to sound good but the MUR860 was simply unlistenable in that position.