|
Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
|
|
|
Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
|
In Reply to: Call for Adagio DAC Builders posted by Matthias M. on February 4, 2002 at 08:34:35:
Hi,Just a hint. As explained in our private mails - the Adagio will remain a esotheric animal. Before it got pushed into this direction I had for possible commercial release made studies of a much simplified version that should however deliver most of what the big brother does. This was discussed on an arcane HK based Board, so I here repeate the entire conversion as Q&A....
=========================================================
Some random conversations about the Adagio'lito
(little/lite Adagio) DAC=========================================================
Q:
CS8414/PCM1716 DAC Kit, does anyone know who sells this DAC kit now? Anyone try? Any good?
A (by T):
Try: www.diyzone.net.
I did try and I was not impressed by the sound. It is however still worth getting, because you can cut the PCM1716 of and with a little skill fit a TDA1545 to the PCB (Op-Amp Position) and re-use/rebuild the powersupplies to give you +5V for the TDA1545.
Then you have a simple, cheap but great 16-bit non oversampling DAC. I have designed a tube output for the TDA1545 which with minor changes would work great with such a non oversampling concept.
Q:
Is your PCB for the DAC available for sale yet
A (by T):
No and it is unlikely to become available soon. most People want a full Kit and not just a PCB and require more support than I can afford to give, so I suspect the PCB's for DIY'ers are now permanantly shelved.
Q:
I am really ignorant in digital audio. Can you show me how to change to the use of TDA 1545. Was that a dropin replacement? Can I avoid the uses of IT/chokes as described on your site that for TDA1541?
A (by T):
It is not a drop in replacement, in effect you cut away all the tracks around the 8-Pin Op-Amp and the original DAC Chip. Then you wire the whole thing up in the classic "hard wired" fashion, it's only a few wires (3pcs for the Data & Clock, one ground, one Powersupply) and a few resistors and capacitors.
But basically you MUST be comfortable with DIY electronics, otherwise don't bother.
Yes, for the 1545 I have a schematic on DJ's Cheap Tube Audio in the files section which is meant for the cheap Marantz/Philips CD Players which also use the TDA1545. However, it will require "re-tuning" of the Analogue Filter to work well with non oversampling, at the moment the values shown are for the oversampling filter used in the CD-Players....
I checked the design through, here is what it should look like for Non Oversampling (only changed values shown)....
R2 = 100
R3 = 18k
R4 = 11k
R5 = 15k
R9 = 24KC1 = 1n5 Silver Mica
C2 = 100p Silver Mica
C3 = 4n7 Silver MicaThe load on the Output Should ideally be 100K or higher.
Also note that the circuit discussed is suitable ONLY for the TDA1545, NOT for the TDA1541 or ANY other Chip. The changed Values for the Filter noted above are ONLY for non oversampling at 44.1KHz and are not valid at any other sample frequency.
In the same place (DJ CTA) there is also a Schematic for a "super regulator" aimed at supplying the TDA1545.
The whole resulting DAC (the Cheap DAC Kit, TDA1545 and above Valve Analogue stage can probably deliver around 70 - 80% of the sound the Adagio offers.
Q:
I will have to build the same from scratch - etching and drilling a pcb would not be a problem. Do you think the schematics per following would be the same:
http://diglander.iol.it/paeng/a simple 96 khz dac.htm
A (by T):
It is exactly the Kit. All you need to do is to connect the TDA1545 Data Inputs to the relevant outputs from the CS8414 and to add the two 11k Resistors and the Decoupling Cap on the TDA1545 Reference pin (look at the Datasheet on the Philips Web-Site).
Q:
hard to believe by changing a few caps and resistors this would become a non-os. truly amazing.
A (by T):
NO, NO, NO. The changes in capacitors Values are to accomodate a DAC that operates without Oversampling, they do not make (for example) a Philipc CD723 Player into a non-oversampling one.
The changes in capacitor values are needed as the Non Oversampling DAC has a staircase type current output with the "steps" being spaced with a 44.1KHz Frequency. This leads realistically to several decibel HF rolloff.
By making the a Lowpass Filter with a certain degree of "peaking" in the response we can offset this rolloff. However this only required if the DAC operates non oversampling. If the DAC is fed an oversampled signal, like in the Philips CD-723 CD-Player this additional > 3db lift at 20KHz would be very undesirable. So hence the change of values for this pecific application.
Q:
Do you think it is beneficiary if I change the bridge rectifiers to tube? - I just have a tungsol 5u4gb to spare. Whats the value of C6? Do I need to change the caps and add a choke?
A (by T):
Yes. I would in fact recommend the full Supply from the design referneced below:
http://www.diyaudio.de/archive/dac2.pdf
Q:
Referring to the schematics from the digilander.iol.it site, do I just "float" Cc of the CS8414? Fsync connect to WS, Sck to BCK, Sdata to DATA? Mck will again be "floated"?
A (by T):
Yes, this should work.
Q:
On the TDA1545, I obtained the block diagram from the Philips website. There is a Vref outlet from the Iref thro' a 33K resistor.
A (by T):The whole Vref shooting match is needed, also, make both resistors in the Vref circuit 11k, this improved the dynamic range and is needed for my design. You will also need the decoupling Cap, the better quality the better, Sanyo Os-Con SH Series or Black Gate PK are minimum, Black Gate NX-HiQ are better.
Q:
Do I need to connect this Vref somewhere? Also the Vref feeds a couple of Opamps. Do I just ignore the Vref when I use tube analog stage?
A (by T):
Other than feeding it to the chip - yes. It has no further external application.
This is the state of affairs so far, I doubt that there will be much more on exchanges, as short of giving a full hands on tutorial this should cover it anyway.
Other items for reference in this context:
TNT-Audio Convertus DAC design Documents (loads of background and so on, please read this rather than bugging me):
http://www.tnt-audio.com/clinica/convertus1_e.html
The Convertus uses 4 X TDA1543 instead of 1 X TDA1545, Input formats, most connections etc are similar for both chips, main differences are the Reference Pins.
TDA1545 Datasheet:
http://www.semiconductors.philips.com/acrobat/datasheets/TDA1545A_T_3.pdf
The TDA1545 suffers from variations in series production and AFAIK they are still being "graded", it is worth getting the better grades.
Functionally this chip mimics the Operation of the TDA1541, but it operates using CMOS (as oppsoed to bipolar) circuitry and it has the dynamic matching reference capacitors on board, plus it requires just one low current positive 5V supply.
Later T
PS, If there are specific questions the above references and converstions do NOT cover, feel free to ask here, I'll endeavour to answer, but please note that this whole thing is considered by me as "NOT SUPPORTED". So I'll answer ONLY if I feel the question has general merit and if I have sufficient time to answer.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Re: Call for Adagio DAC Builders - Thorsten 10:45:18 02/04/02 (2)
- @zen or @Tazo - Matthias M. 23:04:25 02/04/02 (0)
- Re: Call for Adagio DAC Builders - Matthias M. 11:39:55 02/04/02 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
