That's a good point, I'm still doing my research and I still have my single ended amps to use in the mean time. I think the voltage swing is an issue but I'm still unsure if it's even effected at all
I don't see a way that it would with my limited knowledge unless I connected the two.
But here's what the designer of the M³ had to say about voltage swing
"The M³ is DC-coupled, so any offset will be amplified and show up at the outputs. Since those offsets are equal at the hot and cold sides, they "cancel" when taken differentially from the respective outputs, but the no-signal "zero volt" line will be at the DC offset voltage, not 0V, and thus will severely impact the voltage swing headroom."
That makes me think that I need caps if I use this amp. If I did, would I need 4 or 2 and how do I wire them up?
Yep, basically what it sounds like that means (not my circuit so I don't know) is that that amp is basically a bridge tied pair of single ended amps and not a fully symmetrical amp where the output is always referenced to GND. You would be best off AC coupling to that sort of amp. So use the output caps.
I believe you're correct Russ and I'll confirm, thanks to you and Brian for the responses.
At that point I'm assuming I only need to AC couple the balanced output, and I would need 4 capacitors correct? I'm also a bit foggy on how to wire them, do I put the a cap on each + and - directly to the output pins on the xlr's or do I connect them differently?
I have this formula to calculate the value needed
fc = 1 / (2 * Pi * R * C)
R is the impedance in Ω
C is the capacitance is F
fc is the corner frequency in Hz
solving for C you get:
C = 1 / (2 * Pi * R * fc)
At that point I'm assuming I only need to AC couple the balanced output, and I would need 4 capacitors correct? I'm also a bit foggy on how to wire them, do I put the a cap on each + and - directly to the output pins on the xlr's or do I connect them differently?
I have this formula to calculate the value needed
fc = 1 / (2 * Pi * R * C)
R is the impedance in Ω
C is the capacitance is F
fc is the corner frequency in Hz
solving for C you get:
C = 1 / (2 * Pi * R * fc)
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You will need four caps for balanced and you put them in series right at the output, you obviously need non polar caps.
Do not under estimate the cost of four good NP caps, in many cases they will exceed the cost of Legato.
Given that you are creating a balanced M³ which already has opamps, maybe step back to IVY III for ease?
Do not under estimate the cost of four good NP caps, in many cases they will exceed the cost of Legato.
Given that you are creating a balanced M³ which already has opamps, maybe step back to IVY III for ease?
Thanks Magsy...
Yeah, I'm well aware of the cost of good caps. I may wind up with the IVY but for now I can get some caps that have good reviews for about $10.00 a piece.
Plus at this point I still have 2 single ended amps That I love listening to so since I have the legato I'll use it until I have gathered all the parts and pieces for the balanced M³
Yeah, I'm well aware of the cost of good caps. I may wind up with the IVY but for now I can get some caps that have good reviews for about $10.00 a piece.
Plus at this point I still have 2 single ended amps That I love listening to so since I have the legato I'll use it until I have gathered all the parts and pieces for the balanced M³
Yes, Russ you are correct. AMB confirmed that when using the balanced M³ it must be AC coupled
Depends on where to use them !Hi Russ/Brian,
I am trying to set up my new Legato 3.1 with BII and for C1-C4 I am using some 3.3nF Russian Teflon caps. The problem is that while BII is in idle these caps are getting quite warm and while playing music the caps are running really hot!
Is this normal for the caps in these positions and if not where to look for the problem, please?
I am using one HD Placid BP to power both I/V stages and one old Placid BP for the BAL/SE part. The total current of both Placids is around 350mA, shunted currents are 60-65mA, Legato input volatges -14.0, +14.5V, DC offsets on all outputs is nulled.
Any help and tips will be highly appreciated, please!
Thanks,
Ivo
I am trying to set up my new Legato 3.1 with BII and for C1-C4 I am using some 3.3nF Russian Teflon caps. The problem is that while BII is in idle these caps are getting quite warm and while playing music the caps are running really hot!
Is this normal for the caps in these positions and if not where to look for the problem, please?
I am using one HD Placid BP to power both I/V stages and one old Placid BP for the BAL/SE part. The total current of both Placids is around 350mA, shunted currents are 60-65mA, Legato input volatges -14.0, +14.5V, DC offsets on all outputs is nulled.
Any help and tips will be highly appreciated, please!
Thanks,
Ivo
Russ,
Thanks for the reply! I ordered some polystyrens from ebay and will try your original Wimas from the kit of course and will report back. The thing that's worrying me is is it possible the Legato to oscillate and this to lead for these caps to get hot. Or in any case they shouldn't get so hot if are not bad?
Thank you!
Thanks for the reply! I ordered some polystyrens from ebay and will try your original Wimas from the kit of course and will report back. The thing that's worrying me is is it possible the Legato to oscillate and this to lead for these caps to get hot. Or in any case they shouldn't get so hot if are not bad?
Thank you!
The original caps are very good. Pure polypropylene without the pollution of metalization .
I have searched this thread for the legato 3.1 balanced output impedance. I wasn't able to find any information. I am not sure looking at the schematic if I can properly tell what it is. What would est the output impedance in this circuit? Is it set by the R1/R2 and R3/R4 resistors? Can anyone provide a little guidance? Thanks!
I...
am not entirely sure, but I believe the Legato output impedance is a function of the I/V resistors, so for stock values, it would be 150 ohms per phase for the balanced output. Just as you suspected, R1-4.
am not entirely sure, but I believe the Legato output impedance is a function of the I/V resistors, so for stock values, it would be 150 ohms per phase for the balanced output. Just as you suspected, R1-4.
Yes...
My understanding is that you are correct: 360 ohms per phase. I am sure Russ will eventually confirm (or provide more details on) this. Russ has pointed out that changing the gain of the Legato does involve some compromises, perhaps higher output impedance is one of those compromises.
I am running R1-4 at 180 ohms, and achieve about 1.9 volts output. I have no problems (lack of dynamics etc) running amp direct into 11K per phase in my amp.
My understanding is that you are correct: 360 ohms per phase. I am sure Russ will eventually confirm (or provide more details on) this. Russ has pointed out that changing the gain of the Legato does involve some compromises, perhaps higher output impedance is one of those compromises.
I am running R1-4 at 180 ohms, and achieve about 1.9 volts output. I have no problems (lack of dynamics etc) running amp direct into 11K per phase in my amp.
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