Topic: JB3 A/D chip: What is it?

[tms]

I've read here that the a/d converter on the JB3 isn't the best, and that if a taper is serious he/she would use an outboard A/D convertor. 

Has anyone figured out what the actual chip is? 

[Brian Skalinder]

I've read here that the a/d converter on the JB3 isn't the best, and that if a taper is serious he/she would use an outboard A/D convertor. 

Has anyone figured out what the actual chip is? 

Let your ears decide, not what others say (especially since I suspect many of the people bashing the JB3 ADC haven't listened to it in a blind comp for a true comparison):

http://taperssection.com/index.php?topic=14574.0

I'll gladly re-host once I reformat my PC in the next day or two.

[tms]

I've read here that the a/d converter on the JB3 isn't the best, and that if a taper is serious he/she would use an outboard A/D convertor. 

Has anyone figured out what the actual chip is? 

Let your ears decide, not what others say (especially since I suspect many of the people bashing the JB3 ADC haven't listened to it in a blind comp for a true comparison):

http://taperssection.com/index.php?topic=14574.0

I'll gladly re-host once I reformat my PC in the next day or two.

Thanks Brian!

I have seen this before and read your comments.  It's actually the reason why I'm thinking about an outboard a/d to go with my JB3.  But before adding another component to my system I'd like to know what I'm 'upgrading' from. 

What I'm wondering is what the specs are on the JB3 A/D chip.  Does anyone have good quality pictures of the internals of the JB3, especially the board in the region of the line-in jack?  Here are a couple pic that I found online but they're not good enough to read chip ID numbers.  The the only chip I can make out in the vicinity of the Line-in jack is a PIC16LF872 -I/SS (?)which is a microcontroller.  I really doubt they're using that as the A/D although it does have 5 10bit a/d converters according to the data sheet on that chip.

If that is the A/D though, it would be a real good reason to use an outboard A/D converter!

On the underside of the board near the line in is location U705 on the board, the 10 pin chip LTUA which is the Li ion battery charger, so that's not it.

Basically I'm trying to avoid opening up my JB3 although I will do it if necessary.

Todd in Buffalo

[Brian Skalinder]

Ah, you must be a gearhead!

If that is the A/D though, it would be a real good reason to use an outboard A/D converter!

In my mind, it doesn't matter what the actually chip is - only how it sounds.  Trust your ears!  If we were talking about modding the UA5, then the chip might matter.  But if we're simply talking taking it out of the signal chain, it doesn't matter, IMO.  I believe the analog stage has far more impact on the sound of an ADC, than the actual chip itself, so you'll want specs on how Creative implemented the analog stage as well, in order to complete your gearhead evaluatuation.  Me, I'm no techie, so I have to use my ears.

At any rate, all this only to end with:  sorry to say I don't have any specific answers about the specific chip used.

[tms]

Ah, you must be a gearhead!

If that is the A/D though, it would be a real good reason to use an outboard A/D converter!

In my mind, it doesn't matter what the actually chip is - only how it sounds.  Trust your ears!  If we were talking about modding the UA5, then the chip might matter.  But if we're simply talking taking it out of the signal chain, it doesn't matter, IMO.  I believe the analog stage has far more impact on the sound of an ADC, than the actual chip itself, so you'll want specs on how Creative implemented the analog stage as well, in order to complete your gearhead evaluatuation.  Me, I'm no techie, so I have to use my ears.

At any rate, all this only to end with:  sorry to say I don't have any specific answers about the specific chip used.

That's a good point, see what they used to amplify the analog signal before the a/d if they used anything at all. 

The a/d chip might be under the hard drive, I can't see anything that might be it anywhere near the line in jack. 

[Digital Quality]

I read that the AD is a Philips part UDA1380 but when I opened mine up all I found was a UDA1320. I may have misread the part number or the 1320 may just be for output DA.

Here is the 1380 data sheet http://www.semiconductors.philips.com/acrobat_download/datasheets/UDA1380_4.pdf

[Evil Taper]

The JB3 works fine as long as you can feed it a hot enough signal.  Alot of people use mod sbm-1>opti>jb3 to bypass the JB3 ADC and signal weakening that the unit can cause.  It's not neccessary though, especially if you're pulling board feeds or hot rigs.

[tms]

I read that the AD is a Philips part UDA1380 but when I opened mine up all I found was a UDA1320. I may have misread the part number or the 1320 may just be for output DA.

Here is the 1380 data sheet http://www.semiconductors.philips.com/acrobat_download/datasheets/UDA1380_4.pdf

I did open mine up last night and wrote down as many chips as possible.  A lot of them are hidden under the LCD and the ribbon cable that travels under the HDD.   I did read one to be a UDA1380TT.  It would make sense b/c there is a crystal right next to it I believe labeled 24.576S 2H.   That must be for clocking the A/D and D/A. 

Table 24 on page 33 of the sheet you posted says this chip can do 16, 18, 20, and 24 bit data output.  Too bad these aren't available in the firmware. :-(

It looks like what they did was place the ADC DAC chip over near the headphone out jack (which this chip supports) and the line outs.  I guess the priority for the designers was playback and not recording, I have read interviews where this was mentioned as the strenght of the JB3;  102dB S/N ratio (?) on the output. 

The downside is that the traces carrying the analog in travel across the board, probably directly under the HDD.  That explains the HDD noise problems when recording at high gain settings.

[Digital Quality]

Speaking of this chip, I've been using my backup jb3 to listen to mp3 at work lately. I think it's a pretty nice sounding player, much sweeter and more round than the ipod it replaced  That said, I think there is some compression in the output path though even with no eax applied. This got me wondering if there may be some sneak compression on the input side too?

[Brian Skalinder]

This got me wondering if there may be some sneak compression on the input side too?

I wonder.  When I ran my JB3 v. D100 line-in / ADC comp, I noticed the JB3 line-in seemed just the slightest bit compressed relative to the D100.

[tms]

This got me wondering if there may be some sneak compression on the input side too?

I wonder.  When I ran my JB3 v. D100 line-in / ADC comp, I noticed the JB3 line-in seemed just the slightest bit compressed relative to the D100.

A bit (No pun intended) off topic, but what are the options for outboard ADC for this?  It has to be 16 bit, right, or else the data will be truncated.  Looking at the UA-5, I don't see that it's switchable from 24 bit. Only the rate is adjustable.  Am I missing something?

[bgalizio]

There is an "advanced" (or "adv") switch on the UA-5 which changes it from 16 to 24 bit.

[tms]

There is an "advanced" (or "adv") switch on the UA-5 which changes it from 16 to 24 bit.

Aaaaahhh... That's what that switch is for.   Any other A/D's out there that do 16 bit to avoid truncation by the JB3?

[Nick Graham]

There is an "advanced" (or "adv") switch on the UA-5 which changes it from 16 to 24 bit.

Aaaaahhh... That's what that switch is for.   Any other A/D's out there that do 16 bit to avoid truncation by the JB3?

Quite a few actually...

Graham Patten ADC-20
Denecke AD20
Sony SBM1
Apogee AD-500

[tms]

There is an "advanced" (or "adv") switch on the UA-5 which changes it from 16 to 24 bit.

Aaaaahhh... That's what that switch is for.   Any other A/D's out there that do 16 bit to avoid truncation by the JB3?

Quite a few actually...

Graham Patten ADC-20
Denecke AD20
Sony SBM1
Apogee AD-500

I had considered the first two, but neither seems to be swichable to 16 bit.  They're both 20 bit and I don't want to truncate to 16 with the JB3.

I never considered the other two, where can I buy them? They don't seem available anymore.

[Digital Quality]

I think they are just 20 bit on the front end and they get decimated down for the output so they have 16 bit outputs. It's just that the filtering is done in 20 bit, they throw the last 4 away for you.

On the JB3 AD, I had a thought this weekend. You could maybe slip some insulation foil between the disc and the board to help isolate the analog lines. I don't remember how tight things are in there but it seems like something could fit in there. May be worth a shot but it sounds like you have resigned to an outboard ADC.