Legato Tweakers Thread...

[merlin el mago]

I measured AVCC on the BII, at the ouput of the AVCC module 3.49V, where I have to measure on the Legato, at the + & - input signal coming from BII?

correct.

So I have to adjust with trimmers until each input sit as close to 1.75V, right?

 

[Bassivus]

Just a quick note to confirm some of the discoveries others have reported. I finally have the dual mono Buffalo ll with Trident regulators, 2 Legato 2, full Placid power and three Ventus per side as my amp is single ended. While some things were better I felt I had lost some of the magic of the original Legato (without buffer). The high end seemed soft almost smeared as if there was a phase difference between the three fets. The bass was very full to the point of being bloated without the drive or extension of the IVY or the musicality and balance of the Legato 1. Everything stock, +-15 volt, biased to 1/2 AVCC at input and output, shunting 80 ma...

Do I understand you trimmed Placid Bp for Legato for only 80mA or you are talking other stuff?

 

[Bassivus]

So I have to adjust with trimmers until each input sit as close to 1.75V, right?

Yes thats right 1.745V

 

[stephen1212]

The 80 ma is the excess current headroom measured at r13 and r14 on the Placid bipolar, not the total current which is much higher. I am only driving an amplifier input at the moment not headphones or other heavy loads so 80 ma is likely more than enough.

 

[ferrilu1]

Hi in order to drive the LegatoII board using a Placid BP at 12Volt wath is the current value to set per rail on the Placid? 250 or 360 mA ?
Thanks for your help
gianluca

 

[merlin el mago]

Legato manual recommends +-12 VDC, Placid manual bipolar recommends for all TP products 200 mA

 

[merlin el mago]

Measure Legato inputs:

L+ 0.010
L- 0.007

R+ 0.008
R- 0.005

It's possible these measurements, because are far than 1.745V (AVCC/2)?

 

[Russ White]

Legato manual recommends +-12 VDC, Placid manual bipolar recommends for all TP products 200 mA

Sorry, that is not correct. 200ma is just a good starting point. You have to tune the Placid BP to the load. If your load only draws say 60ma, then 100ma (40ma shunted) would be plenty. But if it draws 200ma you would probably want at least 250ma (50ma shunted).

 

[Russ White]

Measure Legato inputs:

L+ 0.010
L- 0.007

R+ 0.008
R- 0.005

It's possible these measurements, because are far than 1.745V (AVCC/2)?

Did you measure to GND? or between each other?

 

[merlin el mago]

To GND?

 

[Russ White]

Yes you measure voltage between two points. Which two points did you measure?

 

[merlin el mago]

Measure Legato inputs:

L+ 0.010
L- 0.007

R+ 0.008
R- 0.005

It's possible these measurements, because are far than 1.745V (AVCC/2)?

Did you measure to GND? or between each other?

Yes you measure voltage between two points. Which two points did you measure?

L+ to GND left channel
L- to GDN left channel

R+ to GND right channel
R- to GND right channel

 

[Russ White]

Have you started adjusting the pot?

 

[merlin el mago]

Not, I am asking if I do it well before to start to adjust with trimmers, can I start?

 

[Russ White]

Absolutely.

 

[merlin el mago]

thank you

 

[merlin el mago]

Done, this afternoon I will hear the adjust

 

[merlin el mago]

Fine adjust I recommend to everybody spend 5 minutes to do it.

It's necessary to change something to run the Legato +15V -13V, it's also other adjust or upgrade?

 

[stephen1212]

So I paralleled a 2K8 resistor across the two 680 ohm current source resisters in each of the eight positions on the two Legato 2 boards. This added current has brought the outputs down from about 7.5 to about 6.5 Volt while allowing me to keep + - 15 Volt rails. Everything is even more dynamic. There is a weight and size to the instruments, and the depth of the soundstage is amazing.

One question, others have said that distortion models better with asymmetrical power. Does anyone have actual measurements that verify this? I would be willing to use an additional Placid for the Ventus to allow running the Legato 2 with a lower negative rail. Intuitively I might aim to match the current source resistor to the I/V resistor value and lower the negative rail accordingly. With things sounding so good I will not be trying this experiment unless someone can point out a reason as to why it would reduce distortion or be of benefit for other reasons.

Again thanks for pushing me to tweak the bias point. It seems that every aspect is worth optimizing and provides ample reward for the effort.

 

[boudy]

Legato 2 at 1.2V output

I'd like to run at the reduced output.

475R is the value of EACH resistor and not the overall parallel combination, right?

How's the 2.0 manual coming along?

Thanks

-Eric

Here is how I am running my Legato (2.0.0 PCB with 3 FETs per side per half):

I/V resistor 105R(I don't need 2VRMs, 1.2 or so is fine).
Current source resistors are 475R (2 x in parallel)


Russ