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pongo  
#1 Posted : Monday, February 21, 2011 12:12:38 AM(UTC)
pongo

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hi - have i to solder in the 3 added resistors with a burson 5,6 V / 500 mA regulator instead the placid?

regards

pongo

Edited by user Tuesday, February 22, 2011 12:05:15 AM(UTC)  | Reason: Not specified

pinnocchio  
#2 Posted : Monday, February 21, 2011 6:31:29 AM(UTC)
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Hi Pongo,

You have to solder the resistor with any power supply. They're used to set voltage of Tridents. One of them is 1.2V and the other two are 3.3V as I recall.

Thanks
Do
NicMac  
#3 Posted : Monday, February 21, 2011 10:15:51 AM(UTC)
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Do they set the voltage? - I thought they set the current!
I know the tridents are supplied with optimal resistors for their specific use on Buffalo II but I have not been able to locate information on how the resistor values are actually calculated.
Cheers,
Nic
pinnocchio  
#4 Posted : Monday, February 21, 2011 3:00:37 PM(UTC)
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Now you make me wonder... You're probably right on that one.

Don't have any information on how it is calculated either.
Russ White  
#5 Posted : Monday, February 21, 2011 7:47:20 PM(UTC)
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They set the current. :) The current is roughly 1.2V across that resistor.

Edited by user Monday, February 21, 2011 7:50:39 PM(UTC)  | Reason: Not specified

NicMac  
#6 Posted : Tuesday, February 22, 2011 2:39:13 PM(UTC)
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Shunted current I assume.
What is the values of resistors provided with the 3v3 and 1v2 tridents?
Anybody read or measured?
Sorry, but I haven't got them to play with yet!

Some curiosity driven measurements and guesses:

While playing 24/92 S/PDIF files I measured the current drawn by Buffalo II on the different supplies using a cheap DMM. I get:
VDD (1.2V): 90-115 mA
DVCC (3.3V): 16 mA
VDD_XO (3.3V): 13 mA
I did not measure AVCC as I assumed it to be very low (I may be wrong as the each side of the dual-shunt supply seems to draw >100 mA @ 5V!).
The current drawn by DVCC and VDD_XO are rather constant (in the time domain of my DMM!) while VDD varies quite a bit with music transients.
As I think to have read that you can draw up to 75 mA on the Volumite header (which is fed by DVCC) I guess that the default 3v3 Tridents must be set to shunt > 16+75 mA. So if my lousy math gets me there R4 = 12-10 ohms to supply 100-120 mA....... as usual I'm very likely to be wrong!
LeonvB  
#7 Posted : Tuesday, February 22, 2011 2:52:07 PM(UTC)
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The values for the Trident resistors can be found in the integration guide. A new version can be found here: http://www.twistedpearaudio.com/docs/docs.aspx
NicMac  
#8 Posted : Tuesday, February 22, 2011 3:24:27 PM(UTC)
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Thanks LeonvB,
Never noticed the "Document Repository".....
BTW in "Appendix: DIP switch settings", for Switch 2, in the comments column it reads: "Has no meaning if switch 1 is OFF". I think it should be: "Has no meaning if switch 1 is ON".
Cheers,
Nic
LeonvB  
#9 Posted : Wednesday, February 23, 2011 10:53:49 AM(UTC)
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It's kind of new, there's no link for it yet from any of the normal pages. Brian is working on it.

I've corrected the mistake, and will upload a new version later this week. If you can find more: keep them coming... If we all work together it should get quite a nice guide for people to use.
sidiropa  
#10 Posted : Tuesday, March 8, 2011 2:18:59 PM(UTC)
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Since I also have two of the 3.3v tridents I wish to use to their full current capacity, it would be great to know which of the three values R values supplied (10R,15R,20R) or any other for that matter would be preferable.....from both the guide and the previous posts 10R seems to be the right one...right?

Edited by user Tuesday, March 8, 2011 2:31:29 PM(UTC)  | Reason: Not specified

Russ White  
#11 Posted : Tuesday, March 8, 2011 5:11:38 PM(UTC)
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The max current from the trident is equivalent to ~1.2 Volts across R4. I = V / R. Remember that the trident has an input voltage limit of 5.5V.

alazira  
#12 Posted : Wednesday, March 9, 2011 5:54:03 AM(UTC)
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Russ White wrote:
The max current from the trident is equivalent to ~1.2 Volts across R4. I = V / R. Remember that the trident has an input voltage limit of 5.5V.



Hi Russ,
Is that 1.2V across R4 for both 3.3V and 1.2V versions? So the 10ohm R4 would set max current at 120mA. Can the current be safely increased by using a lower value for R4 or is that about the max for the trident?
Russ White  
#13 Posted : Wednesday, March 9, 2011 7:49:50 AM(UTC)
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The max load will be something around 150ma. But I have never tried to push it so hard it will fail. :) There are also some other components that would likely need to change to go beyond that in any case.

The short of it is that it was never intended for more than 150ma.

The current is the same regardless of the output voltage.
alazira  
#14 Posted : Thursday, March 10, 2011 12:44:55 PM(UTC)
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Thanks Russ.
The reason I asked is because I tried a 3.3V trident in another application but it didn't run properly. With the 20ohm R4 it only has max current of 60mA, so I'm guessing more is needed. An R4 of 8ohm would allow 150mA, but I will try first by paralleling the 20ohm with a 15ohm to see if that works. Hopefully I won't kill this gem of a product.
Russ White  
#15 Posted : Thursday, March 10, 2011 4:13:11 PM(UTC)
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That works out to about 8.5R which should be just fine. :)

Edited by user Thursday, March 10, 2011 4:14:05 PM(UTC)  | Reason: Not specified

alazira  
#16 Posted : Friday, March 11, 2011 6:50:20 PM(UTC)
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Hi Russ,
The increased current fixed the issue with no magic smoke. Thanks.
stewart  
#17 Posted : Sunday, June 19, 2011 2:10:33 PM(UTC)
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Is there any downside to simply installing a jumper for r1/r2 on the lcdps instead of installing the different resistors when powering a buffalo with tridents?

Edited by user Sunday, June 19, 2011 2:11:07 PM(UTC)  | Reason: Not specified

Russ White  
#18 Posted : Sunday, June 19, 2011 8:37:37 PM(UTC)
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No. You will lose a little filtering, but not much. I wouldn't worry over it.
Brian Donegan  
#19 Posted : Tuesday, June 21, 2011 8:27:53 AM(UTC)
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stewart wrote:
Is there any downside to simply installing a jumper for r1/r2 on the lcdps instead of installing the different resistors when powering a buffalo with tridents?


If it is a recently purchased LCxPS (only two 3W power resistors, both 2R7), you really don;t need to do anything special (like jumpering). Just use what is in the kit.
sureshm  
#20 Posted : Saturday, November 26, 2011 2:30:48 PM(UTC)
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The DVCC trident comes with a 20 ohm resistor for R4 included. Applying the '~1.2 Volts across R4' condition, I get 60ma max current. I am not sure what the DAC chip actually draws from DVCC, but the guide says an additional load of 75ma can be drawn from DVCC from the I2C header. If the chip was to draw say 50ma then we would need a CCS of ~125ma. Does that mean I need to use a different R4 or have I got the calculation wrong somewhere?

The real question I would like answered is whether I can use a volumite and exaU2I (less then 20mA) both drawing current from DVCC and still use a 20 ohm resistor in my trident or should I parallel a 15 ohm as discussed earlier?

A side thought, wouldn't you want ~50mA of current headroom for shunt to work well or is the trident headroom lower?
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