Industrial SMD Gainclone - group buy

[sek]

Hi,

I'm happy this Friday!

I'm so glad you are!

I guess this is the moment when you succeeded. You now know that the project was a good decision and works great. This is very good to hear (no turn-on/off noise, no offset, no hum, good sound). Not even the slightest functional problem, as it seems!

I'm happy for you too, even though I couldn't contribute.

Can you show your test setup?

Sebastian.

 

[peranders]

Setup? Martin Logan SL3 electrostatic speakers, CS4328 based DAC (see my homepage). That's it.

I had no problems at all, 100% right from the idea stage via cad, pcb manufacturing, building and testing. It is not always that I'm so fortunate.

 

[sek]

That speaks for you and your experience

That's it.

No, I meant photos of your test setup with the board, heat sink, trafo, etc.

Sebastian.

 

[peranders]

I used a 200 VA, 2 x 24 V toroid, Austerlitz KS112.1.75 (112 wide, 75 mm high, 68 depth, 1 deg/W at 60 W), rather big. This rather big heatsink gets rather warm playing not too loud.

 

[sek]

Makes me wonder. It should actually stay below hand warm. How hot does the chip get (to the touch, or better in degree) at what power (did you measure the power)?

With 112x75x68mm, the actual dimensions are not that big. At such sizes, the thickness of the sink plate matters much. And the deep fins probably need a steady convection to deliver the 1K/W ratio...

And pictures?

I'm still happy it works great. I had some doubts wether I would like it after we disagreed about the beta test (and I couldn't participate), but that's over now that it's a success!

 

[peranders]

To be honest I played rather loud so it's natural with heat.

You could actually _save_ money if you did build the first amp now but I respect your standpoint. No hard feelings from my side.

It looks good at the moment so I really hope that many of you also build the amp. It's rather common, so it seems, that many DIY'ers buy pcb's, parts etc but never get their projects finished. It's OK if all of you order 100 pcb's and noone build but I would think it had been more fun if as many as possible can get music out of their amps.

 

[VT67]

Hi P-A

If it sounds as good as you say, it will be worthy of all the waiting.
It's three weeks now and those darn parts still haven't arrived.

In my case the chip will be attached to an SK42 heatsink. Hope this will be sufficient now that you have mentioned the large heat development of the amp.

Happy listening

Walter

 

[peranders]

I think 1-2 deg/W will be sufficient in most cases. It depends how hard you are planning to play and also used transformer.

 

[VT67]

Hi P-A

Guess what...., the parts finally arrived today.
Having to wait so long wasn't punishment enough!!
I was charged with a 143 Euro bill to cover VAT and customs fee!?
The package was only 129 Euro. Think I'm gonna make a few phonecalls tommorow to the customs office.
This is sofar the most expensive GC I've built. Anyway, I can finally start on the darn thing. Hope I don't get to stressy with soldering all that SMD stuff.
Keep you posted.

Cheers

Walter

 

[VT67]

Oh yeah, a picture of the parts

 

[peranders]

I'll guess we have a working unit tomorrow then?

 

[VT67]

Hi P-A

Aren't we a bit optimistic? Target is more in the near of "this weekend".
I already placed a few parts on the board to check how it looks and I must say it's not an impossible task to solder that SMD stuff. All this will be done with a magnifying glass ofcourse.

Cheers

Walter

 

[VT67]

Hi P-A

O.K. yesterday evening I already soldered 8 resistors per PCB and now I'm gonna progres with the rest of those eyesores!

Cheers

Walter

 

[peranders]

Solder all SMD parts except for the opamp. Check the voltage with an external power supply if you have the opportunity. If not, solder the rectifier bridges also. Then check that the voltages are 11-13 volts. After that solder all other parts excpet for the LM3886. Check the opamp and that you have signal from it. The gain should be slightly higher than 1. Check also the offset voltage which shall be less than 100 uV (or what the datasheet for the opamp says).

After that, finally, solder the LM3886 or mount it first on the heatsink then solder. This depends how your case and heatsink looks like.

.... and then put in the fuses if you haven't done this already. Start with 1 A slow just as a precaution. Apply voltage, either from the mains directly or via a variable transformer.

Then you will have a working amp.

 

[VT67]

Hi P-A

This is were I am so far (see picture). I'm still missing C1, C6, C7 and C14 --- C21. Ordered those from Elfa and they should have arrived yesterday, but they didn't. I'm going to proceed now with the "magnificent custom made P-A coil", diodes, fuseholders and the electrolytic cap's C4, C10 and C12.

Cheers

Walter

 

[Roushon]

Hi Peranders,
I just caught the end of this very long thread...And showed my interest in the project in the WiKi page. If I am not too late tell me the procedure to get the kits...

 

[peranders]

Hi P-A

This is were I am so far (see picture). I'm still missing C1, C6, C7 and C14 --- C21. Ordered those from Elfa and they should have arrived yesterday, but they didn't. I'm going to proceed now with the "magnificent custom made P-A coil", diodes, fuseholders and the electrolytic cap's C4, C10 and C12.

Cheers

Walter

Looks good! A proof of that it isn't so hard after all to solder this.

 

[peranders]

If I am not too late tell me the procedure to get the kits...

You are not too late because we haven't started yet. When Walter and/or Anders has built their amps and feel that they have succeeded I will start collecting money for the big order. Walter, Anders, when are you ready?

 

[VT67]

In a minute!!!

 

[sek]

You're really pushing your fellows hard, Prof. Sjöström.

But the prototypes look very good!

I guess with the fairly long time of 6 months set as an 'outer' limit for the beta phase, many people are actually counting days until the boards are finally released.

Sebastian.