DIY Purifi Amp builds

[boXem]

Looks like LT3042 and LT3093 LDOs to form a low-noise bipolar PSU and some SOIC-8 OpAmp, might be LM4562, OPA1612, LME49724 or OPA1632?

Well spotted . Opa1612, at least for the first prototype.
But to my eyes, the killer point of the board is not this.

 

[kn0ppers]

I just think it's great we get to prototype PBCs for so little money these days. Allows for more variety of approaches to try. I haven't found a buffer board that ticks all my boxes yet, so maybe I'll have to do something about that if I end up buying a set of Purifis, but I appreciate the fact that more options are appearing.

 

[mocenigo]

Can't wait for Ghent to release his Purifi EVAL case, then it should be trivial.

I am not sure this is 100% a good idea. This would mean using the banana posts which are only attached to the PCB via two soldering joints. If you have heavy cables or you happen to trip onto them, you can cause significant damage. I think those posts are mostly to try out, not for a permanent fixture. I may be completely off the mark of course, but for Ghent it is not necessarily the best idea.

Of course one can use the connectors on the back of the EVAL1, with plugs and wires to connect to other connectors which are properly fixed to the back of the case, as explained already a few times in this thread.

 

[Billy Budapest]

Quick question—my understanding is that for US customers the EVAL1 is DKK4,700 minus VAT. I know that before VAT, the price is approximately $700. Minus VAT, is it around $550?

 

[TimoJ]

Quick question—my understanding is that for US customers the EVAL1 is DKK4,700 minus VAT. I know that before VAT, the price is approximately $700. Minus VAT, is it around $550?

DKK4700 already is without VAT.

 

[Billy Budapest]

DKK4700 already is without VAT.

OK. The page is confusing because it says the DKK4700 is with VAT and without VAT.

 

[TimoJ]

OK. The page is confusing because it says the DKK4700 is with VAT and without VAT.

Where? https://purifi-audio.com/vare/eval1/
There it says:
DKK4,700.00 excl. VAT
DKK5,875.00 incl. VAT

 

[Billy Budapest]

Where? https://purifi-audio.com/vare/eval1/
There it says:
DKK4,700.00 excl. VAT
DKK5,875.00 incl. VAT

When I go to that link, it says:

DKK4,700.00 excl. VAT
DKK4,700.00 incl. VAT

 

[Billy Budapest]

Screenshot:

 

[TimoJ]

When I go to that link, it says:

DKK4,700.00 excl. VAT
DKK4,700.00 incl. VAT

I guess it detects that you are located outside of EU.

 

[Billy Budapest]

I guess it detects that you are located outside of EU.

That must be it. Still confusing as I purchase many items from the EU and am used to calculating the amounts minus VAT. The only issue is finding out the VAT percentages per the sales location. The math afterwards is straightforward. In any event, it’s US$700 for me, give or take.

 

[mocenigo]

When I go to that link, it says:

DKK4,700.00 excl. VAT
DKK4,700.00 incl. VAT

depends on your location

 

[JimB]

Ok I think I see four little tabs in each green box. I fold those tabs outward using the screwdriver or just fold them inward so the wire rests on top of them?

No. First, you fit the wire down inside the whole channel, then, last, fold the little tabs down on top of the wire to secure it. The 'silver' positions are how the part comes, before inserting a wire. The 'black' positions have wires inserted, fully. This let's you see both 'before' and 'after'.

And all I'll really be doing is cutting of the crimps Purifi has on the wires in its kit and inserting the unstripped wires into the appropriate slot using the flat end of the jeweler's screwdriver blade to nudge them into the slot while not touching the contact points circled in red so as to not damage them?

Right.

And the silver colored metal bits in the slots unused in yoour photo and which run the length of each slot are not removed b/c the wires rest on top of them when pressed into the slot? So they are underneath the wires in slots 2, 6,, and 10 in the photo?

Correct. They are not designed to be removed.

 

[JimB]

I use quite heavy bi-wired speaker cables (with locked banana connectors) and those PCB mounted connectors didn't feel stable enough. Maybe if you could somehow add an extra support for them, but in stock form they are supported with just two solder joints.

Understood. I still intend my final builds to have high quality, panel-mounted binding posts. But not for fear of damaging the EVAL1. Through well sized back panel holes, and with the EVAL1 properly secured inside, the whole amp is going to get dragged across the room before you can make that board fail, inside. Of course, to each their own, but I would not hesitate to use the on-board sockets if I was only going to be connecting with banana plugs. In a really extreme condition, I'd make some provision to support the cable so that only 'reasonable' force was applied to the connectors (that includes the banana plugs themselves).

 

[TimoJ]

Understood. I still intend my final builds to have high quality, panel-mounted binding posts. But not for fear of damaging the EVAL1. Through well sized back panel holes, and with the EVAL1 properly secured inside, the whole amp is going to get dragged across the room before you can make that board fail, inside. Of course, to each their own, but I would not hesitate to use the on-board sockets if I was only going to be connecting with banana plugs. In a really extreme condition, I'd make some provision to support the cable so that only 'reasonable' force was applied to the connectors (that includes the banana plugs themselves).

Maybe they would have survived but I do find them pretty sad looking connectors partially sticking out of backpanel holes. Removal was easy so why not.

 

[JimB]

Maybe they would have survived but I do find them pretty sad looking connectors partially sticking out of backpanel holes. Removal was easy so why not.

Indeed. As you know from my example photos, mine are gone (or won't be through the back panel). I just think others shouldn't fear using the internal sockets, if other options are too difficult for them.

 

[wineds]

Since I have been getting PMs about my wiring I edited @JimM original sketch to reflect my setup.

Pinout for SFH619A is here : http://www.vishay.com/docs/83674/sfh619a.pdf

Power switch : https://core-electronics.com.au/metal-pushbutton-latching-16mm-blue.html

Power supply : https://au.mouser.com/ProductDetail/MEAN-WELL/RS-15-12?qs=ql1K%2BkDau3qz9%2BonMzIW2g==

Credit to @JimM

 

[JimB]

Maybe they would have survived but I do find them pretty sad looking connectors partially sticking out of backpanel holes. Removal was easy so why not.

Silly me. I should have suggested: if bi-wiring, you can use BOTH the on-board sockets AND back panel mounted sockets!

 

[TimoJ]

Silly me. I should have suggested: if bi-wiring, you can use BOTH the on-board sockets AND back panel mounted sockets!

But then you'd lose sense wires to the panel mounted sockets. And since Purifi bothered to add those to the PCB sockets, surely they think they have some effect to "something"?

btw. has anyone tried to add an extra sockets for sense wires and terminate those at the speaker's end? (of course with a suitable backup resistors on the PCB in case the wiring breaks)

 

[JimB]

But then you'd lose sense wires to the panel mounted sockets. And since Purifi bothered to add those to the PCB sockets, surely they think they have some effect to "something"? ...

Sure. I think the remote sense paths are needed to ensure the best possible signal to an output connection, given the seemly low quality audio path to that point (the various PCB traces and header/pin connections on the PCBs), and to deliver their super low output impedance (whether it is really valuable or not). I would like to think that one could expect essentially the same voltage at the PCB output pads as at an added connector on the back panel, if using heavy copper wire and good soldering. In such a case, there will be almost no difference between sensing right near where the PCB pad is, and the actual connector (resistance of 3" of 14 AWG ~ 0.6 milliohms).

Still, I do realize they used the sense connection right at the output connector for their demonstration units, and, like you, that is what I am doing with mine.