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Hallo,
Just received my Legato and noticed there are different silkscreen markings to the ones in the manual.
I can't find QP1-4 or QN7-14. Any help apreciated as I'm stuck with the build and don't want to mess things up. Thanks.
Regards.
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First the bad news: I sent Brian a batch of the new Legato boards that were meant to be prototyped. he accidentally sent some of them to people who ordered the current legato. He is sending you replacement PCBs for the current legato kit.
Here is the good news: You get a free Legato version 2 PCB!!! If you would like to be a beta tester I will post the schematic and you just need to get parts.
Sorry for the mix up.
Cheers!
Russ
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Hi Russ,
Yes, I'd love to get involved. All I need is the new schematics. I'll build v-2 first since It's here already.
While I think about it, have you thought about a little add on board sort of like Otto but plugging directly into Buffalo headers to route signal either to Legato or Ivy. There are quite a few peple with both of them it wold be interesting to have switchable I/v stage. What do you think?
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Hello Russ, Can I also be a beta tester  of the new version of Legato. Thanks Subbu
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Hi Russ Just received the pcb, thank you. That must be the quickest post I've ever had from US. Now what about that schematic  Can't wait sorry...
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Here you go. All of the P-channel FETs are BS250 R1-4 and R9-16 are 1W types though 1/2W should be fine. The rest of the Rs are 1/4W. keep in mind, while I trust these values, they are subject to change in the final release. If you use PNP bipolar only use one pair per side, not 3 pair. Edited by user Tuesday, September 21, 2010 7:26:59 PM(UTC)
| Reason: Not specified File Attachment(s):  legato2_sch.pdf (61kb) downloaded 403 time(s).You cannot view/download attachments. Try to login or register.
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Looks very interesting!! If you are able to remove C5-8 (DC blocking) in the signal path that would have been more than great (servo?). (Btw, you got PM from me.) Edited by user Wednesday, September 22, 2010 3:06:48 AM(UTC)
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tbm wrote:Looks very interesting!!
If you are able to remove C5-8 (DC blocking) in the signal path that would have been more than great (servo?).
(Btw, you got PM from me.)
The only really good way to add a servo to this circuit would be to use a folded cascode. I actually have a circuit that does that, but it is different from the Legato. It is the new revision of Counterpoint. The downside to using the folded cascode and servo is that the circuit is far more complex. The main point of version 2 of Legato is the removal of the buffer since it is almost never really needed and adding the additional FETs in parallel to increase the overall transconductance. I also paralleled the main load bearing Rs. All in all it is not a significantly changed circuit. Edited by user Wednesday, September 22, 2010 5:13:36 AM(UTC)
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Also for those folks requesting to be beta testers (by PM or otherwise) . Thanks for your interest, but we will not have to do any more beta testing other than on those PCBs already sent out.
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Just checking:
Is "OUT_R/L .4/.5 the SE output and the .1/.2/.3 the balanced out?
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The outputs are clearly marked on the board.
The SE outputs are OUTL.1 and OUTR.5
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Hi Russ
Paralleling BS250's- what an excellent idea! I'd been looking for a MOSFET with higher Yfs and lower on resistance to try, but they're all power devices, and I guess they'd need to operate at much higher currents than the BS250 to keep these characteristics
Paul
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Please folks, stop asking for a servo, etc. on the Legato design. Give it a listen! If you are worried about the coupling caps, use some quality film/foils, you will not be sorry. I am using Mundorf zN with the Legato 1 and the sound is superb. A servo would add noise, require more complexity, and it is an uneccessary feedback loop. The sonics of the Legato are likely so good because it is a simple circuit, as such it requires coupling caps.
If Russ has improved on the Legato 1 already with the Legato 2, all I can say is Wow! Russ, what about a JFET Legato? Would that possibly be even better?
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needsp wrote:Hi Russ
Paralleling BS250's- what an excellent idea! I'd been looking for a MOSFET with higher Yfs and lower on resistance to try, but they're all power devices, and I guess they'd need to operate at much higher currents than the BS250 to keep these characteristics
Paul
Hi Paul, The power type FET devices also all have much higher parasitic capacitance. :) Thanks for the tip of the hat. I do appreciate it. The reason we use the BS250 is because it is really quite linear. It is a very good match in the CFP. There are a couple other small signal FETs (Phillips) that would also work well, but they are very hard to obtain. Cheers! Russ
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barrows wrote:Please folks, stop asking for a servo, etc. on the Legato design. Give it a listen! If you are worried about the coupling caps, use some quality film/foils, you will not be sorry. I am using Mundorf zN with the Legato 1 and the sound is superb. A servo would add noise, require more complexity, and it is an uneccessary feedback loop. The sonics of the Legato are likely so good because it is a simple circuit, as such it requires coupling caps.
If Russ has improved on the Legato 1 already with the Legato 2, all I can say is Wow! Russ, what about a JFET Legato? Would that possibly be even better? Thanks for the kind words. I fully agree that part of the *magic* of Legato is it's simplicity. There is a lot of truth in the "Less is more" idiom. As for the JFET, while they are indeed quite low noise, their transconductance is actually far too low in my opinion. I have seen Nelson Pass has used them in his DIY "Zen I/V". While I think the complementary nature of the design is laudable and excellent for what it is, it unfortunately is not a good match at all for a balanced high current output DAC such as the ESS9018. The input impedance is so high as to modulate the inputs far beyond what is require for detectable distortion. I am not saying I would rule them out completely, but some feedback is required to make them really work well I think. At least in this application. Cheers! Russ ** EDIT ** I meant to say that JFET transconductance is very low. Edited by user Thursday, September 23, 2010 8:48:41 PM(UTC)
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Still waiting for the rest of the components...From RRRSSS Components he he. Edited by user Saturday, September 25, 2010 4:25:04 PM(UTC)
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Hi guys! My newly received Legato PCB also happened to be the 2.0.0 version. with best regards from Oslo, Norway Edited by user Tuesday, January 18, 2011 3:23:53 AM(UTC)
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Russ, how about ZVP2106A ? RDS(on)=5ohm, the other parameters seems alike. edit: Just to clarify, it's not just a wild guess. In the BS250P data sheet it says: "Refer to ZVP2106A for graphs". Edited by user Monday, October 4, 2010 9:39:38 AM(UTC)
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Hi avr300
I bought some ZVP2106A from Rapid Electronics in the UK and may give them a try. Though I didn't notice the "Refer to ZVP2106A for graphs" in the BS250P datasheet- I found them independently!
Legato actually uses BS250KL. BS250P is a Philips type, which isn't an exact equivalent of the BS250KL (from Vishay Siliconix) that Russ used. TP0610KL is identical to the latter- it shares the same datasheet- except the pinning is reversed- just turn each device through 180 degrees.
Think I've got this right- Russ will no doubt correct me if I haven't
Paul
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Hi Paul.. I saw your post at DIY. Sorry for deep linking, this is the only data sheet which is "in hand" (not my host). http://courses.cit.corne...2/csm44_hvd2/bs250kl.pdfAs I see it, the BS250P, the ZVP210A and the TP0610KL are identical and is off the BS250KL by 180 degrees. Do you agree with me on that? The BL250KL is unobtainable here in DK, that's why I have to seek for an alternative.
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