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Legato or IVY III outputs for Buffalo II?

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#121
12v or 15v?

I had to increase to voltage across R1 and R2 to .3vdc in order to get a healthy 12volts when I loaded with the Lagato.
Just curious, will current demands go down or up if I increase voltage toward 15v. I have plenty of ventilation and the PS is in a different box than the Buff/Lagato.
After almost 100 hours it is really sounding very good. I am using the OPA2227 in the buffer.
 
#129
AussieAmpBloke said:
igwt,

Both!
360mA per rail is 360mA through the whole thing.
Click to expand...

needsp said:
Hi Pelliot

When I went from 12 to 15V, the total current (for just the I/V stages- no buffers, no Bal/SE stage) increased from 180mA to 200mA

Paul
Click to expand...

The current without buffers, and Bal/SE stage is ok around 200mA?
Current without Bal/SE stage ?

From the manual!
"Adjust VR1 and VR2 on the Legato until each of the inputs sit as close to AVCC/2 as possible.
Don't sweat over this very much. Testing has shown that anything close is just fine."

This last adjustment should be made with or without the buffalo dac?
Thanks
 
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#132
Russ, I measure 2mv dc between + and - for one channel and -64mv for the other. This is before the AC-coupling capacitors. I am guessing that the other channel has higher dc due to transistors not being matched close enough? Would I be able to reduce the dc by replacing QP1 or QN1 on the respective channel?
 
#133
Russ White said:
The output impedance is well under 1ohm. And the drive capability is about 20ma. I have used it driving 600ohm headphones with ease. But I am not sure I would drive a load less than that. It could be done with some tweaking.

Cheers!
Russ
Click to expand...

Hi Russ,
I am planning on using my Baffalo II with speakers outputs, both SE and Bal, and balanced headphones outputs. I would like to be able to use my low impedence Denon AH-D2000's.

From your note above it sounds like this may be an issue with the Legato. What do you recommend? I recently bought a Legato to compare with my IVY III but haven't tried it yet.

You had told me before how to hook up the IVY III to do this, I am just wondering if it's possible, and how, to do this with the Legato.

Thanks in advance.

Mark
 
#134
BrianDonegan said:
Current drawn by the ballsie stage is minimal (just that of an LM4562).

Adjust for AVCC with the dac attached.
Click to expand...

Brian,

I cannot go further than 1,58 with the trimmers (VACC measures 3,57 and 3,58), so there is no way I can get VACC/2 at the Buffalo output because trimmers have already reached their top limit.

What could I do if I would want to get around 1,75 ??

thank you !
Pepe
 
#135
lindamar said:
Brian,

I cannot go further than 1,58 with the trimmers (VACC measures 3,57 and 3,58), so there is no way I can get VACC/2 at the Buffalo output because trimmers have already reached their top limit.

What could I do if I would want to get around 1,75 ??

thank you !
Pepe
Click to expand...

This might happen if you run lower voltage rails. If you do you may need to decrease R19 and R22. Try 3.92K or something close to that.

Cheers!
Russ
 
#136
Russ White said:
This might happen if you run lower voltage rails. If you do you may need to decrease R19 and R22. Try 3.92K or something close to that.

Cheers!
Russ
Click to expand...

Thank you Russ !!

I forgot to mention that my Placid is setup to provide +- 12 VDC to the Legato module , guess you are refering to that , right ?.

I will try 15 volts and report here again if there is any problem.

best
Pepe
 
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#137
Russ White said:
I don't see it that way at all. Here is why. There are two distinct processes involved here.

First we have a symmetrical I/V converter. It is fully discrete with no global NFB. It stands on its own.

Then we have an orthogonal but practical and extremely useful bal/se stage which you the builder can decide to use or not. It is completely optional. The DAC is a balanced DAC, not SE. This I/V stage is a balanced I/V stage.

All of that to say to do BAL/SE with discrete components right would take more space than I had on this PCB, and would not have yielded as good results as what is there right now.

Instead, I took the pragmatic approach and offered the builder options. Use the excellent on-board BAL/SE stage, or do something else with the balanced signal.

One great option would be the Ventus which is a discrete BAl/SE converter. But it is far too large and makes too much heat to put on something like the Legato PCB. 🙂

So I think the choice was the most logical I could make given the goals regarding form factor etc. 😎

Cheers!
Russ
Click to expand...

hey look like I said, I dont have an issue with it, I quite like opamps, as I feel that for some jobs there just isnt a better option. It sounds like this is one of those times, but if I were an opamp hating NFB freak looking for an alternative for SE output (and you would be surprised how many people are just that), I guess I would be disappointed to see that you took it half way and then finished it off with an opamp. I guess some people that love no feedback also like SE output due to the feeling that come of the goodness found in the even order distortion and harmonics is cancelled out along with the noise and bad distortion by CMMR. I do wish there was a way to retain that along with the benefits of balanced audio, but for now i'm not willing to take that trade off.

I get why you did it, but I guess it just wouldnt have been my first choice. it also means you cant have a fully discrete dual differential balanced output.

i'll still be buying though, looks great for my purposes
 
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#138
Qusp...

I am not sure I understand this:

" it also means you cant have a fully discrete dual differential balanced output."

I have a Legato (not running yet) it appears to me to have a fully discrete, dual differential, balanced output. I did not stuff the board with the circuitry for the BAL/SE converter, so there is no IC Opamp on board at all.
I suggest that those who must have SE output, and do not want an IC Opamp in the signal path, should go ahead and use transformers for BAL/SE conversion.
Personally, I have no use for SE output.
 
#140
I had the IVY lll in for a few weeks and I am now listening to the Lagato with Ballsie. First impressions are that the Lagato has a bit more sweetness and roundness but less extended in the highs. I will be putting the IVY back end this weekend to confirm. My speakers are Maggy llla's with a ribbon tweeter.
 
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