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Joined: 11/28/2014(UTC) Posts: 21  Location: Tatabanya
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Christmas came early, and over thanksgiving I had a chance to chew thru the docs, this and the dyi forums, but still like to clarify a few things before I solder.
I would like to configure a BIII as a 4 channel DAC and stack it with IVYIII on the bottom and a Lagato on top.
On Placid HD Bi for the output stages and Placid HD for the DAC.
Input will i2s on DIN1-2 and DIN5-6(?), all balanced connections. Don't use DSD.
1, IVYIII, Replace the kit default R1-R4 to 1.5k ohm to compensate for the DAC output levels in 4 ch mode.
2, Legato, (Will be adjusted to 2Vrms out in the same process) Replace the kit default R1-R4 to ~378ohm, R9-R16 to 1.68k and C1-C4 to 750pF to compensate for the lower output in 4ch mode and set the RC filter accordingly.
3, Use the standard stacking headers in the kit to connect the IVY on the bottom using DAC output 03 and 04, and use a long 3M 3 pin headers bent in a "Z" to connect the Legato on top to DAC output 07 and 08 (Bend in a Z to meet up with socket on Legato's bottom).
4, Solder jumpers on Buffalo III
J8 to connect + of channel 1,3
J7 to connect - of channel 1,3
J2 to connect + of channels 2,4
J1 to connect - of channels 2,4
J9 to connect + of channels 5,7
J10 to connect - of channels 5,7
J3 to connect + of channels 6,8
J4 to connect - of channels 6,8
5, Set switch on Buffalo 3 for 4 channel mode
Quantizer 8 Bit = SW1:1 On, SW1:2 Off
Differential mode?
How is the input from DIN gets routed? Do I need to short DIN1-3, DIN2-4, DIN5-7 DIN6-8?
PCM jumpers? There is only 6 channels worth that.
Input remap?
Thanks in advance!
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Rank: Administration
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Hi,
I will answer your questions one by one. :)
1. Correct - but I would actually prefer to increase the second stage resistors instead R13-R16. You will get lower noise and distortion.
2. Correct! perfect!
3. As long as you have enough pin to bend this should work fine. :)
4. Correct!
5. No switch for 4 channel mode - you will just feed D2 + D3 with the first pair of channels and D4 + D5 with the second - remember each data line carries two channels. There are a couple of quantizer modes that will work - you can experiment there - I would start with the defaults. You can use JPCM1 and JPCM2 to connect D2 to D3 and D4 to D5 respectively.
I hope everything is more clear now.
One note of caution - the IVY-III will have slightly higher output than the Legato - if you want to to be more equal then shoot for only about 75% more gain out the IVY-III instead of 100% I would not change the Legato.
Have fun with the project!
Cheers!
Russ
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Rank: Member
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Joined: 11/28/2014(UTC) Posts: 21 Location: Tatabanya
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Thank you for your time Russ! Much appreciated.
Totally missed the stereo nature of signal (duh). And it's super clear now :)
I got long pins today and looks as stacking two output stages like this is indeed a workable solution.
MOUSER part #: 517-929705-06-18-EU
In regards to output voltage matching of the legato and IVY,
So (in#2), My numbers are correct for the Legato, but later on you suggest NOT changing the legato.
But since I do need to change them all for the 4ch mode anyway, why would I not want 2Vrms on the Legato?
I find the same comments elsewhere, but fond little in an explanation of why 2Vrms is not a good idea on the Legato.
Noise? THD? Heat? Given that I would be connecting these direct to an amp I would think I really want more not less.
A bit of more noise I think I could live with but certainly do not want more THD. (I will be taking some measurements but like to get a head start.
Perhaps at the end It will be a happy medium of both set to 1.75V,...
Or you just suggesting that for listening test AB comp, I would be better off just lowering the IVY?
For the IVY You also suggest that instead of R1-R1 change (documentation), you prefer adjusting the second stage in R13-R16 for more less gain.
Which results in less noise, (as I understand, this makes sense from the schematics.). Comparing the IVY and Legato schematics and I wonder wouldn't this also be true for the legato? Leaving R1 and R1 default and making all necessary gain changes in R9-R16.
I'm guessing the correct thing to do would be to adjust R1-R4 for input sensitivity (for higher channel count, thus less output on BIII). And for the gain required (1.5, 1.75, 2Vrms) adjust the R9(13)-R16 for output gain and do this on both the IVY and Legato.
On the IVY I'm guessing there should be no changes to C1-C4 if changing R9 to R16?
Your wisdom and expertise for an overly enthusiastic newbie wanna be would be much appreciated on this.
Thanks a million!
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Rank: Member
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Joined: 11/28/2014(UTC) Posts: 21 Location: Tatabanya
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I'm starting to realize why you don't like changes to the Legato. 1W requirement makes the necessary values difficult to source. But then again, with the 4 ch/dac config you got to changes those anyhow. And it seems that 2Vrms on the legato (and the component values required) is one of the easiest to source combinations. Legato IVY B3ch vrms r1-4 - Act r9/16 Act c1-4 Act r1/4 Act OR r13/16 Actual 4 2 400 402 1680 1740 1466 1500 1500 1500 340 340 4 ~1.75 375 360 1650 1500 1375 1500 1312 1320 298 301 4 1.5 300 301 1360 1370 1100 1000 1124 1130 256 255 Edited by user Friday, December 5, 2014 6:44:06 AM(UTC)
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
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Was thanked: 89 time(s) in 83 post(s)
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All meant was that the values you specified for legato are OK and I would not try to balance out the two by adjusting further on Legato. I would do my adjusting on the IVY-III :)
That said - as far as Legato resistors go - no need to be too exact as long as you are close to the original ratio you are OK.
On IVY3 I would *Only* change R13-R16 (increase their value by ~ 75%) this will get you close to matching the legato - but please understand you may need to tweek this to get them to be exact if that is important to you.
I would not change anything else on the legato but the parts you mentioned in your first post.
Only a suggestion - this is DIY so you can and should do whatever appeals to you - but carefully. :)
Cheers!
Russ
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