Legato 3 - Look ma! No caps!

[RollE2k]

It says this module runs 12-15v, and that 15v is the "best".
Is it anyway possible to make it run even higher voltage, say 18v? and would there be any benefit doing that? (i'm just thinking it wouldn't be necessary burning 9v in the shunt-PSU i have right now, which is why i ask)

 

[Russ White]

It is possible, you may want to tweak some resistor values. You would also need to be sure that the opamp you use for bal/se can handle it.

Personally. I would stay in the 12-15V range.

 

[RollE2k]

I won't be using any opamps, since i will run balanced straight into my linestage (they will share box).
Hmm, then i'll maybe have to look into modifying for higher voltage, since i wouldn't want to increse sinking on the PSU.

 

[RollE2k]

By the way, since these are DC-cancelling - i won't need any caps between the legato and my volcontroller going into the grid of my tubes in the line stage?

 

[Erlend Sæterdal]

Is it possible to use other resistors around the opamp to get some gain there ? Change the resistors 21-24 to 10 kohm ?

 

[BrianDonegan]

Is it possible to use other resistors around the opamp to get some gain there ? Change the resistors 21-24 to 10 kohm ?

Yes. It's a straight forward op-amp stage, so the usual gain calculations can be used.

 

[RollE2k]

By the way, current consumption is said to be 350mA. How much is it approx without the opamps?

 

[avr300]

Still aprox. 350mA

 

[necplusultra]

Greetings,

so I fired up the legato3 for the first time. I set the ballanced Voltage to 0 but the SE does not fluctuate. It stays at 0 even if I turn the pots completeley left or right. Does this mean that the IC1 is blown?

 

[necplusultra]

Greetings again.

I tried the opamp in an O2 and it confirms to be functionning. I am powering legato3 with salas bib with about 300ma on each +- 15 V rails. The bal section can be trimmed to offset 0 v dc. The SE section cannot be trimmed no matter what direction the wiper on vr3 vr4 are turned. I'm not using the buffer section so I jumpered j5,j6. I don't have anything populated at r25, r26, l1,L2 uc2,uc3.

ANy help would be appreciated.

Note: my system is direct with no caps so I don't want to try it out live before knowing if there is DC at the SE end

 

[necplusultra]

OK my bad

populated R25,r26 and works now.

 

[RollE2k]

By the way, how sensitive is the legato for Input voltage difference between the positive and negative voltage? I'm going for resistor to set voltage, not pots and wonder if it would be +14.90/-15.00 would that just be trimmed out at the output?

And also as said, if i wire the outputs to my linestage without any ground connection, would that be any problem (they are in same case, and i don't want to mix ground from both supplies, but they will all be connected to chassis through a resistor or rectifier bridge)?

 

[Russ White]

Not very sensitive at all. anything within a volt on either side should be fine.

 

[nvduybom]

Hello ,

I measure my Legato with all out put Balance & SE is 0.1 mV DC , but When I reset power supply then all value is changed . What is wrong ?

Van Duy

 

[Russ White]

It could be your PS settling? Its hard to say. if you like open up a thread on the support forum with pictures.

 

[Erlend Sæterdal]

Toslink problem with Buffalo




Sorry for posting it here. I could not find the Buffalo tread. On your support side I can not post pictures like this. The toslink make the lock led flashing. I use the 270 series resistor and 100 ohm parrallel. Will it make the difference with 75 ohm ? Or do I have to change anything else ?

 

[Russ White]

View attachment 326457


Sorry for posting it here. I could not find the Buffalo tread. On your support side I can not post pictures like this. The toslink make the lock led flashing. I use the 270 series resistor and 100 ohm parrallel. Will it make the difference with 75 ohm ? Or do I have to change anything else ?

Reduce the size of the picture and post it on the support forum please.

This is definitely not the right thread.

Still one hint, try tying -IN to GND for that input.

Do not respond in this thread or I will start deleting posts.

Thanks!

Russ

 

[nvduybom]

It could be your PS settling? Its hard to say. if you like open up a thread on the support forum with pictures.

Thanks for your reply ,

I think it is time warm up of Mosfet and Transistor ?.

I measured all out put is 0V with 200mV DC meter, then I off/on power,the output about 8mV and measured -1.6mV in 5 minute later .

It is normal ? .Can I connect direct to tube pre-amplifier ? .

Van Duy

 

[Russ White]

It really depends on the amp.

BTW when measured like that the inputs are floating. Which will effect things.

This is why you need to measure again once the DAC is conneted.

If the few mv of warm-up offset is too much your amp then use AC coupling caps.

One other note - the main pair of NPN (QN5 QN6 etc) can be thermally coupled. This should significantly reduce any such drift.

I do this by gluing them together or using heat-shrink tubing etc.

Cheers!
Russ

 

[avr300]

One other note - the main pair of NPN (QN5 QN6 etc) can be thermally coupled. This should significantly reduce any such drift.

One picture = 1000' of words.

This if from an earlier Legato but the picture is principal.

Sorry for interrupting the threat.