[KoshNaranek]

Mike, Jason implied that the analog stage of the parallel DAC chosen for the Bimby was difficult to implement. Could you please expand on the rationale for the chip chosen?

Thank you.

 

[madwolfa]

Mike, Jason implied that the analog stage of the parallel DAC chosen for the Bimby was difficult to implement. Could you please expand on the rationale for the chip chosen?

 
Price and the fact that it is a 2 channel DAC in one IC. It has some damn impressive specs as well, even compared to more expensive chips. 

 

[jimmers]

Mike, Jason implied that the analog stage of the parallel DAC chosen for the Bimby was difficult to implement. Could you please expand on the rationale for the chip chosen?

Thank you.

It's the one used in the DAC data sheet?
 
(BIPOLAR MODE, 4-Quadrant Multiplying Mode schematic)
 
 
Edit: Or did you mean why AD5547CRUZ? 

 

[KoshNaranek]

It's the one used in the DAC data sheet?

(BIPOLAR MODE, 4-Quadrant Multiplying Mode schematic)


Edit: Or did you mean why [COLOR=000000]AD5547CRUZ? [/COLOR]:blink:

I was curious why a parallel DAC vs serial. It sounded like it was more difficult to implement

 

[rtaylor76]

I was curious why a parallel DAC vs serial. It sounded like it was more difficult to implement

I think parallel DAC because it can decode L and R simultaneously for extremely low phase error.

Also, I doubt Robert [/S MIke ]or Jason will answer...trade secrets I am sure.

It's late. I keep wanting to call Mike Robert because of the use of the quote in the title of this thread.

 

[AviP]

Also, I doubt Robert or Jason will answer...trade secrets I am sure.

Mike* or Jason

 

[jimmers]

I was curious why a parallel DAC vs serial. It sounded like it was more difficult to implement

Aha! I mistook your query.
AD5547CRUZ is 2 channel so only one chip needed, so cheaper, and takes up less room - not sure why the externals were a problem as it looks like they went with the datasheet, and on the surface the parallel loading would appear to be straightforward (as long as you remember to load all the bits)

 

[KoshNaranek]

Aha! I mistook your query.
AD5547CRUZ is 2 channel so only one chip needed, so cheaper, and takes up less room - not sure why the externals were a problem as it looks like they went with the datasheet, and on the surface the parallel loading would appear to be straightforward (as long as you remember to load all the bits)

Thank you for your response. My understanding of the bit loading is that it would require more preprocessing than serial.

A previous post by Jason implied the part count for analog stage required more parts.

 

[madwolfa]

Aha! I mistook your query.
AD5547CRUZ is 2 channel so only one chip needed, so cheaper, and takes up less room - not sure why the externals were a problem as it looks like they went with the datasheet, and on the surface the parallel loading would appear to be straightforward (as long as you remember to load all the bits)

Parallel bits loading is challenging, but not a big deal (mostly done in firmware). The problem is that this specific DAC outputs current (I) instead of voltage (V), hence you need an IV converter. Discrete IV implementation would be extremely complicated (read: lots of PCB real estate), so they used a precision op-amp (AD8512) instead in Bimby and Mimby.

Yggy and Gumby chips output voltages, hence the analog part is relatively simple.

 

[jimmers]

My bad.
When I wrote "on the surface the parallel loading would appear to be straightforward" I'm afraid I was thinking microcontroller rather than the actual SHARC DSP which is not as parallel friendly.

 

[Baldr]

I think parallel DAC because it can decode L and R simultaneously for extremely low phase error.  

It's late. I keep wanting to call Mike Robert because of the use of the quote in the title of this thread.
 

Parallel because the best 16 bit DAC out there was two channel with parallel inputs - it also happened to be a multiplying DAC, requiring multiple voltage references.  This expands and complicates discrete circuitry for the Bimby/Mimby.  Another feature of the DAC is a current output, which requires a proposed discrete circuit to be even a more complex I/V converter.  The op-amps chosen were recommended by Analog devices to maintain the less than 1 LSB DNL and INL specs, a crazy level of performance for a spec (INL) seldom quoted at all.  Yes, the DACs are separate, allowing simultaneous decoding of channels for no phase interchannel difference.
 
 I am not just an Wagnerian opera buff.  Don't get me wrong - I feel a spiritual as possible for me listening to opera.  I felt the rapturous ecstasy of liebestod (love and death) listening to a 1936 recording of Kirsten Flagstad less than an hour ago, capping off 4 hours of Tristan und Isolde.  With the exception of Puccini (and Mozart), I am not a big FLIO (fan of light Italian opera) - I am a huge fan of classical music from Haydn forward and Monteverdi backwards.  Late romantic music and 20th century music is also amazing to me.  In case there are some of you who missed one of my cues - I am an unashamed Dead Head.  My daughter was conceived at a Grateful Dead Concert, back in the day when concerts were concerts, given at parks and fields.   Robert Hunter and Jerry Garcia were a writing team who created poetry at their absolute pinnacle with Ripple,  IMHO.  
 
As transported as I have been at Wagnerian venues, I always feel constrained and afraid of tapping my toes, as most Wagnerian opera patrons, particularly at the Met, will turn around or tap others on the shoulder disapprovingly.  Quite a bit different at a Dead concert with Jerry singing and playing his guitar with 7 fingers and two thumbs against the occasional uneven musicianship of the rest of the band.   Bob Weir looking down as he played and swayed close-eyed.  Pig-Pen shouting "Let's Phuck" at the top of his voice, usually once per concert right after Turn on Your Love Light.  One thermos of lemonade for free, one with a dollar donation, right at the entrance.  Dozens of fans openly taping the concert with no objection from the band.  Those concerts were amazing.  An opera is full of introverted patrons.  A Dead concert is full of extroverted ones.  The music from an opera is very, very filled with awe and wonder - as is the whole of the experience from a Dead concert.
 
I digress. 

 

[KoshNaranek]

Thank you

 

[kstuart]

  Quote

I am a huge fan of classical music from Haydn forward and Monteverdi backwards.

Ha !  Although I enjoy all genres and periods of music, I am a huge fan of classical music from Haydn backwards and Monteverdi forward. 

 
And for those who are wondering what he is talklng about in the second half of his post:
 
 

 

[kstuart]

... and at the very same show


 


 

 

[US Blues]

  ... and at the very same show
   
   

If you don't know Jorma, you don't know Jack!