I geuss I need to ask your opinion. Should I wait to place the order for the power supply until the transformers come in? I wouldn't really need all these being shipped seperately. Can you also put a stop on sending out the legato and volumite so they can all be shipped together? For that matter, I can wait until the Buff II is in stock, Mine is due to arrive in September.
legato Ac coupling caps
Dear Russ,
nowdays there is a big effort, often justified at the ears, to eliminate capacitors on the signal path. And... especially electrolytics!
Now I would like to know if it is possible to eliminate the two 100uF AC coupling capacitors at the outputs of the Legato.
Will not the bipolar power supply (and the circuit) give already a low offset? How low at the balanced outputs?
Which solution you could eventually suggest? (but no transformer please)
Thank you in advance,
GM
Dear Russ,
nowdays there is a big effort, often justified at the ears, to eliminate capacitors on the signal path. And... especially electrolytics!
Now I would like to know if it is possible to eliminate the two 100uF AC coupling capacitors at the outputs of the Legato.
Will not the bipolar power supply (and the circuit) give already a low offset? How low at the balanced outputs?
Which solution you could eventually suggest? (but no transformer please)
Thank you in advance,
GM
to Brian or Russ
Sorry... I forgot... last question...
Is there any chance to eliminate the IC and use another circuit or to convert balanced to unbalanced output?
You developed a top performance discrete circuit, but who has got only unbalanced devices, should go unfotunately for an IC stage.
And I think that lot of audiophiles has got only unbalanced devices... (see for ex. Vacuum tube ones, but not only)
Are you thinking to develop such a modification?
Thanks again!
Sorry... I forgot... last question...
Is there any chance to eliminate the IC and use another circuit or to convert balanced to unbalanced output?
You developed a top performance discrete circuit, but who has got only unbalanced devices, should go unfotunately for an IC stage.
And I think that lot of audiophiles has got only unbalanced devices... (see for ex. Vacuum tube ones, but not only)
Are you thinking to develop such a modification?
Thanks again!
The circuit is designed such that capacitors will be necessary unless you use a transformer. But you are free to use whatever capacitors you like. You can just use them off the board. This has always been the intent. If you want big film caps you would just use them at the outputs.
There is another circuit called "Counterpoint II" which uses a folded cascode and does not require an coupling capacitor.
The legato quite simply is just another type of circuit. It cannot be DC coupled. You will just need to understand that. It sounds incredible, and I don't think you will care once you actually hear it.
I don't personally use SE gear at all.
If you want you can omit the BAL/SE stage and go into 2 Ventus configured as BAL->SE converter. The Ventus is discrete.
Cheers!
Russ
There is another circuit called "Counterpoint II" which uses a folded cascode and does not require an coupling capacitor.
The legato quite simply is just another type of circuit. It cannot be DC coupled. You will just need to understand that. It sounds incredible, and I don't think you will care once you actually hear it.
I don't personally use SE gear at all.
If you want you can omit the BAL/SE stage and go into 2 Ventus configured as BAL->SE converter. The Ventus is discrete.
Cheers!
Russ
Coupling caps
I personally am going to try using "Zen" film caps from northcreekmusic.com. I got 4.7 uF 225V, these are medium size (compared to high dollar monsters like Mundorf Silver/Oil) and their leads will connect directly from PCB to XLR output jacks. I am going into a preamp at 20 k per phase, so 4.7 uF should be fine. But you could not use low values like this into lower impedances. A transformer would be an approach to avoid the caps; of course a transformer will introduce its own set of sonic values. I might try transformer coupling at some point as well... balanced all the way through here...
I personally am going to try using "Zen" film caps from northcreekmusic.com. I got 4.7 uF 225V, these are medium size (compared to high dollar monsters like Mundorf Silver/Oil) and their leads will connect directly from PCB to XLR output jacks. I am going into a preamp at 20 k per phase, so 4.7 uF should be fine. But you could not use low values like this into lower impedances. A transformer would be an approach to avoid the caps; of course a transformer will introduce its own set of sonic values. I might try transformer coupling at some point as well... balanced all the way through here...
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Who says that a cap sounds worse than a tranny or vs. ?
I'll just try it as it's designed - even SE.
No one, that is the entire point, we can try and decide what we like for ourselves. I believe that stock with the electrolytic output caps likely sounds very good indeed; I have no reason to believe that using a quality film cap would sound worse.
coupling caps for Legato
I notice on the TPA Legato page that
"AC-coupling capacitors at the balanced outputs are Nichicon MUSE ES 100uF bipolar audio capacitors (which actually tied as our favorite with Elna RFS (SilmikII) capacitors)." Perhaps it would be interesting to let us know which others were tried and rejected, plus any observations about them.
I'm excited about this new I/V and will be using the "swap from IVY order" button as soon as I see it.
Frank in Mpls.
I notice on the TPA Legato page that
"AC-coupling capacitors at the balanced outputs are Nichicon MUSE ES 100uF bipolar audio capacitors (which actually tied as our favorite with Elna RFS (SilmikII) capacitors)." Perhaps it would be interesting to let us know which others were tried and rejected, plus any observations about them.
I'm excited about this new I/V and will be using the "swap from IVY order" button as soon as I see it.
Frank in Mpls.
Russ,
Could you please confirm/correct my understanding? Those who have tried using transformers directly connected to the Buffalo have been running the DAC in voltage mode since it’s difficult to get the impedance of transformers low enough. If you use a transformer with the Legato, then you can have DAC in current mode, an active stage doing I/V and depending on the set up a transformer doing the rest (filtering, AC coupling, bal to se)?
Also, the current Legato site shows that only ±12VDC rails are recommended. Is it still possible to use ±15VDC, or has further testing showed that it is not ideal?
Thanks
Could you please confirm/correct my understanding? Those who have tried using transformers directly connected to the Buffalo have been running the DAC in voltage mode since it’s difficult to get the impedance of transformers low enough. If you use a transformer with the Legato, then you can have DAC in current mode, an active stage doing I/V and depending on the set up a transformer doing the rest (filtering, AC coupling, bal to se)?
Also, the current Legato site shows that only ±12VDC rails are recommended. Is it still possible to use ±15VDC, or has further testing showed that it is not ideal?
Thanks
sorry if this seems a silly question:
can you explain the power supply requirements for the legato.
I am a little confused by the statement from the website:
do you mean one of each? ( ... the set ) or either one will work. if one of each, (one LCBPS and one Placide BP) , can you briefly explain the advantages .
can you explain the power supply requirements for the legato.
I am a little confused by the statement from the website:
do you mean one of each? ( ... the set ) or either one will work. if one of each, (one LCBPS and one Placide BP) , can you briefly explain the advantages .
Use the...
Placid(s). You need bipolar supplies (+, G, -). You can use 1, 2, or 3 supplies depending on fancy you want to get. 2 gives you true "dual mono" power supplies. You would only need three if you were planning on using the single ended outputs (to power the balanced to single ended converter). Or, you can KISS, and use just one Dual Placid (or LCBS) to power the whole Legato board.
While theoretically using dual (or triple) supplies might/should be better, I wonder if the difference would even be audible. Adding additional supplies means additional diode bridges, which could add noise...
I am not going to populate the single ended converter, and I just plan to run a single Dual Placid for L and R power, keeping it simple makes sense to me.
Placid(s). You need bipolar supplies (+, G, -). You can use 1, 2, or 3 supplies depending on fancy you want to get. 2 gives you true "dual mono" power supplies. You would only need three if you were planning on using the single ended outputs (to power the balanced to single ended converter). Or, you can KISS, and use just one Dual Placid (or LCBS) to power the whole Legato board.
While theoretically using dual (or triple) supplies might/should be better, I wonder if the difference would even be audible. Adding additional supplies means additional diode bridges, which could add noise...
I am not going to populate the single ended converter, and I just plan to run a single Dual Placid for L and R power, keeping it simple makes sense to me.
The Legato input impedance is in the milliohms . You could indeed use a transformer after it, but I would leave the low pass filter on the Legato because it is a low order filter anyway.
10-15V rails will work just fine. 12V will result in less heat than 15V so we generally recommend that.
Speaking of heat. Legato generates a lot of it. Make sure your case is ventilated. Slots top and bottom please. It is a 400ma class A device. No component is overly stressed, but combined they make a good amount of heat. I have been running mine for months with no issues, but I just want to be sure none of you are surprised that it runs rather warm.
The transistors actually don't generate that much heat, its really the 1W resistors. You can mitigate this a bit by building the board with the resistors raised slightly to allow them to cool a bit better. Bottom line is, as long as your case has reasonable ventilation (no need for fan etc) you will be just fine. And if you find it running warmer than you like, you can easily just reduce the rail voltage. The circuit runs quite well even down to 10V rails.
Cheers!
Russ
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