Drive NOS AD1865/62,PCM1704/02/63,TDA1541 from FIFO: Universal I2S-PCM driver board - Page 22 - diyAudio
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Old 16th January 2013, 08:48 PM   #211
qusp is offline qusp  Australia
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lol, yet so far you are the only one complaining....
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Old 17th January 2013, 01:11 AM   #212
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Quote:
Originally Posted by regal View Post
I see what you mean know. Couldn't you convert from i2s to two's compliment at 32 bit then truncate down to 16 bit, that way the LSB would be preserved ?

There are three advantages to 2's compliment with the tda1541a:
1. dual differential
2. dual mono
3. 8xfs (prior to fifo).

Any of three would be negated should we lose the LSB, so I guess I am in the all or nothing camp as far as two's compliment conversion for tda1541 goes (its a touchy subject for many.)

You wouldn't want your design to be less than the best if it is offering this mode I think. The TDA1541A's LSB is its claim to fame in a way, it was developed at a time when there were only 14 bit DAC's, and phillips did a huge amount of engineering to get that 16 bit resolution to match a RBCD standard. Best not offer it on this design if its only 15 bit resolution maybe rev 2 things will fall into place, just my opinion.
regal,

You didn't get my point on the calculation. With the dac working at dual mono differential mode, we didn't lose the LSB, we just got 1 DC offset added on the output.

If the data is A, take 16 bit for example , the range of A will be -32768 to +32767;

With the all bits inverting method I want to use, the differential output will be 2*A+1,
The range of A didn't have any change, but we get a doubled output of A plus 1. Did we lose any resolution?

The invert calculation will apply on all bit and doesn't matter it's 16bit or 32bit.

Regards,

Ian
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Old 17th January 2013, 01:06 PM   #213
regal is offline regal  United States
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Quote:
Originally Posted by iancanada View Post
regal,

You didn't get my point on the calculation. With the dac working at dual mono differential mode, we didn't lose the LSB, we just got 1 DC offset added on the output.

If the data is A, take 16 bit for example , the range of A will be -32768 to +32767;

With the all bits inverting method I want to use, the differential output will be 2*A+1,
The range of A didn't have any change, but we get a doubled output of A plus 1. Did we lose any resolution?

The invert calculation will apply on all bit and doesn't matter it's 16bit or 32bit.

Regards,

Ian
Not complaining just know this issue has been gone over by a lot of enthusiasts.

I hear what you are saying but I would think the "digital" offset would cause a clipping at max output, no ? I guess we need to try and measure.
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Old 17th January 2013, 02:22 PM   #214
noizas is offline noizas  Lithuania
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Quote:
Originally Posted by regal View Post
Not complaining just know this issue has been gone over by a lot of enthusiasts.

I hear what you are saying but I would think the "digital" offset would cause a clipping at max output, no ? I guess we need to try and measure.
Hi regal

at first, it looks you are right: inverting word of all 16x0 to all 16x1 ( or vice verso) should cause clipping.

But we are talking here about two differential data streams: one as it is, another inverted, both from same source.
I can not understand how can be any clipping in inverted stream if it is simply mirrored and here is no any clipping in source?
Do you have personal experience with clipping of inverted data stream?
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Old 17th January 2013, 11:32 PM   #215
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Quote:
Originally Posted by regal View Post
I hear what you are saying
Good to know that

Quote:
Originally Posted by regal View Post
but I would think the "digital" offset would cause a clipping at max output, no ? I guess we need to try and measure.
We are talking about the +1 DC offset introducing to 2's complement format by inverting it for DAC in differential mode. To make it easier, I take 4 bit for example:

For a 4bit 2's complement format, the range will be -8(1000 min) to +7(0111 max).

If A=+7 (0111, max), the inverting result will be -8 (1000), so the differential output would be +7 - (-8) = +15, it's exactly 2*A+1;

OK, If A=-8 (1000, min), the inverting result will be +7 (0111), so the differential output would be -8 - (+7) = -15, it's also 2*A+1;

And more, If A=0 (0000), the inverting result will be -1 (1111), so the differential output would be 0 - (-1) = 1, still 2*A+1;

It's just a 2'complement converting method, I didn't see there is any problem except the +1 issue.

But agree with you, I have to have some test, just to confirm. But I no longer keep my old TDA1541 DAC now.

Regards,

Ian
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Old 18th January 2013, 11:46 AM   #216
regal is offline regal  United States
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Quote:
Originally Posted by iancanada View Post
Good to know that



We are talking about the +1 DC offset introducing to 2's complement format by inverting it for DAC in differential mode. To make it easier, I take 4 bit for example:

For a 4bit 2's complement format, the range will be -8(1000 min) to +7(0111 max).

If A=+7 (0111, max), the inverting result will be -8 (1000), so the differential output would be +7 - (-8) = +15, it's exactly 2*A+1;

OK, If A=-8 (1000, min), the inverting result will be +7 (0111), so the differential output would be -8 - (+7) = -15, it's also 2*A+1;

And more, If A=0 (0000), the inverting result will be -1 (1111), so the differential output would be 0 - (-1) = 1, still 2*A+1;

It's just a 2'complement converting method, I didn't see there is any problem except the +1 issue.

But agree with you, I have to have some test, just to confirm. But I no longer keep my old TDA1541 DAC now.

Regards,

Ian
I've got a blank red barron PCB and a TDA1541 I could send you when I send in my two fifo's for upgraded firmwares, just can't get away from work long enough to build the powersupplies and populate.

Thankyou for all the work on the fifo and now daughter board, its shaping up to be a really ground breaking design.
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Old 20th January 2013, 06:14 PM   #217
JoeyDD is offline JoeyDD  Canada
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Hi, I'm also very interested in this board!

TOTAL = 55

TV Man x 2
merlin el mago
rtd
jameshillj
erin
Nikola Krivorov x 3
Rupor54
vitalica
analog_sa
andrea_mori x 5
dsavitsk
tagheuer
hirez69 x 2
ccliu
BDL
cddumat
regal
zoran
Jogi
Zen(zenelectro) x 2
Buzzforb
SPWON
crobbins5421 X 2
marcus1 X 2
casshan x 2
Dweeb99 X 2
jackw X 2
kazap X 2
danzup x 3
Giordano x2
Tony_T
Tubo x1
clivem x2
noizas x2
JoeyDD x2
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Old 20th January 2013, 08:32 PM   #218
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Quote:
Originally Posted by regal View Post
I've got a blank red barron PCB and a TDA1541 I could send you when I send in my two fifo's for upgraded firmwares, just can't get away from work long enough to build the powersupplies and populate.

Thankyou for all the work on the fifo and now daughter board, its shaping up to be a really ground breaking design.
Thanks regal for offering the PCB. But I'm afraid I need a pair of differential mode 1541 DAC with offset binary jumper. Just let me figure out if I could source them.

You can send the fifo back to me at any time for upgrade. Still keep my address tag?

Have a nice weekend.

Ian
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Old 20th January 2013, 09:19 PM   #219
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Default Offset Binary format option for TDA1541 achieved

PcmTransmitter.v
"......
//2013-01-19 Add offset binary format jumper for TAD1541 OB mode
//2013-01-20 Optional offset binary output achieved
......
module PcmTransmitter(
reset, //system reset
mclk, //system clk
obflagn, //offset binary format flag
......
);
...
endmodule
"

Please see the actual measurement screen shot from my logic analyzer for details.

Tested at 384Khz Fs with MCLK=256Fs.

Ian
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Old 20th January 2013, 09:54 PM   #220
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Default Tested in 16bit

Previous test was in 24bit
Now is in 16bit

Ian
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File Type: png OffsetBinary16BIT.png (26.5 KB, 245 views)
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