Xmas Amp - Dibya's TDA7293 by Jhofland

[xrk971]

Yes, chassis “dirty ground” at the star hub.

 

[Kokanee]

Thanks X. One more quick question, below is the plan for the low cap psu and the SSR protection. Look OK?

Is there any advantage to having the negative speaker binding post connected to the 0V on the All Cees psu rather than the - out on the SSR module.

 

[xrk971]

Connecting negative speakers to 0v on PSU is actually ideal as that gives more direct return path to the PSU.

 

[Kokanee]

Thank you sir, I shall carry on.

 

[Kay Pirinha]

Connecting negative speakers to 0v on PSU is actually ideal as that gives more direct return path to the PSU.

True, but it may also increase the output inductive loop.

Best regards!

 

[Kokanee]

I finished my basic wiring, and gave each channel a test thru 10W/10ohm resistors. Mains power supplied thru a variac and dim bulb tester. increased the voltage slowly to 110V with dead silence, no pops, no smoke. Measured the offset and received 1.8mV on the left channel and 0.9 mV on the right channel. I think everything is OK, so I will connect the low cap psu and the ssr modules, and see if it will play some music. Below are a couple of pics of my wiring so far.

 

[xrk971]

Looking good. I think you will have music no problem.

 

[Signal lost]

Great looking build. Hope all goes well and you get to finally listen to this sweet amp

 

[Kokanee]

Thanks for all the encouragement. I hooked up everything and powered up each channel separately. The left channel played music for a bit and then it cut out. It turned out to be a rookie error: I left one of the corner bolts off of the amp board as it was to hard to tighten down due to proximity to the heatsinks. I thought it would be OK with the 3 other corner bolts holding it. Amazing what you learn when building. Did the same to the other channel, then powered it up again. I must say that this is a very nice amplifier. I am listening to some very nice tunes through my produces does sound this

 

[xrk971]

Why would lack of a mounting bolt for PCB cause music to cut out? If the TDA chip itself was not attached to a heatsink it would thermally cut out due to self-protect.

 

[Kokanee]

Oops, My computer ran out of power, and I could not edit the above post as I was timed out. So to continue:

Did the same to the other channel, then powered it up again. I must say that this is a very nice amplifier. I am listening to some very nice tunes through my mid-fi spkrs and it sounds great. Will let it play for awhile and see if any changes happen.

I would like to thank the designers of this amplifier and all the help I have received from everyone on this forum. Happy building to all and here is a pic of Xmas layout (or should I say the wiring maze).



MM

 

[Kokanee]

Not sure X, when I pressed on the side of the pcb where there was no bolt it made a connection. When I released the pressure the music would cut out. So maybe the pressure caused the chip die to conduct. After I bolted down the corner of the pcb it must have applied the pressure needed to make contact, as I had no more problems. Just to be sure, I will apply a bit more torque to the chip against the heatsink.

 

[Vunce]

My suspicion is you have cold solder joints on the chip pins. The solder should fill the holes completely and slightly wick up the chip legs. Not too much where a bridge between legs could happen.

 

[Kokanee]

Thanks X and Vunce. I will watch the amp with interest and see if any weird stuff happens. This is a temporary case, so I will check the chip condition when I move the amp to a permanent case.

 

[Signal lost]

If i remember correctly( a stretch these days) the right rear corner of the board is the ground or ground breaker. It is the only bolt hole with a conductive ring.

 

[asuslover]

For people who already built this ,
c16, is the nichicon kz 100uf the best choice? did anyone try other caps?
Thanks

 

[Kay Pirinha]

Any 100 µF/63V will do.

Best regards!

 

[Francois G]

He’s asking about “best choice”, not merely an electrically adequate solution. Are you saying quality of ‘lytic doesn’t matter in C16 position? I have a KZ and I’m still building, so the answer is of interest to me too.

 

[asuslover]

I would like to use 105C capacitor because it is very close to the heatsink.
I was thinking of the nichicon ka instead of the kz.

 

[Kokanee]

I don't think that C16 has to be a special cap. It is not mentioned in any of the posts as being "critical or you must have", so any decent quality cap as Kay P noted above should work. On my amp I used one that I had in my inventory, looks like the brown Elna silmic type, but is just another brand 63V/100V/105C. I did use the Elna Silmic II for C5, C11 as part of Dibya's secret sauce. . My amp is playing nicely.