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Hi, I'm quite interested in building this amp, I have the LM4780 available, now it is obsolete. 1) What is the THD levels, is there any measurement data in relation to this PCB? 2) How does this make over 100 wrms, the other kits I have looked at seem to give around 60 wrms (parallel) 3) I have an unused Pass B1 buffer preamp which I want to use, is it suitable for this board as it has very low gain. 4) On the web page it states, "balanced inputs recommended for best performance", my preamp doesn't have balanced out, I have seen some boards on fleabay based on the drv134 to convert to balance, is this absolutely necessary/worthwhile? 5) What rating for the transformer for best performance? I'll be using one per channel. 6) Any advised upgrades, maybe some caps? 7) How does it sound  ? Thanks
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Rank: Member
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Ok, question 2 I have figured out, question 5, I have seen the ratings required somewhere on this forum. So for the remaining? 1) What is the THD levels, is there any measurement data in relation to this PCB? 3) I have an unused Pass B1 buffer preamp which I want to use, is it suitable for this board as it has very low gain. 4) On the web page it states, "balanced inputs recommended for best performance", my preamp doesn't have balanced out, I have seen some boards on fleabay based on the drv134 to convert to balance, is this absolutely necessary/worthwhile? something like this maybe? http://www.ebay.com/itm/222441370583 This would do the trick right??? This would also work on the same transformer as the B1. 6) Any advised upgrades, maybe some caps? 7) How does it sound????? I couldn't find much in the way of a review as such. Anyone? Edited by user Wednesday, June 28, 2017 2:07:49 PM(UTC)
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Maybe you can run balanced signal from your source (DAC?) directly to sympatico with only attenuator in between to control volume level? B1 will likely only make things worse (less transparent etc.) and won't do anything useful here and also forces you to go a single-ended route... Upgrades - only the big and small electrolytes. Depends on speakers, but putting 22000uF caps there instead of 10000 improved a lot of things and is still not much. Even then some speakers are still too heavy for Sympaticos, but adding caps helped in my case. Finally - the trafo affect a lot of things somehow, get as big/powerfull as can afford\reasonable. I gone from 300 to 500 and it got better against my test "heavy" speaker. It sounds very good. Transparent, detailed, spacious, but somehow never harsh. Sympatico's speciality is soundstage - it produced some of the most amazing 3D effects i ever heard in stereo. It's "weak" side is only it's power - it just doesn't like some speakers and it's notrelated to speaker's impedance, a mystery to me. Adding trafo+caps help, but only to some extent.. Finally - carefull when going balanced with sympatico. I burned 1 bass driver with legato+sympatico wiring accident, my mistake though  Edited by user Thursday, June 29, 2017 4:51:13 PM(UTC)
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Rank: Administration
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Sorry, missed this...
1) I think Russ had done some measurements a while back, but I do not have them handy. THD was quite low.
3) You probably don't need it, unless it is your volume control.
4) You can just use SE input, tying -IN the GND. We added a spot for a resistor to compensate for SE input by bumping gain a bit (included in kit). I would not add a DRV.
6) We include parts that will provide optimum performance for the design. The benefits of part changes will be a subjective decision. It's a kit, so you can swap out whatever parts you want, but I think you will like it as is.
7) I like it. I can't comment beyond that in any meaningful way.
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Thanks for the replies, I have one more question though, does this require a thiele network also?
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Rank: Administration
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No. You can add one, but it is definitely not required.
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Rank: Member
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Thanks Brian, just as I was opening the forum I got email notification of your reply!
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