Xmas Amp - Dibya's TDA7293 by Jhofland

[xrk971]

Originally Posted by ClaudeG

Pardon my ignorance... I see a lot of care to insulate the bolt + heatsink from the amp's power chip, as often the case.

I always wondered how this worked inside the chip's hole: for sure the bolt must be touching when passing through - how is that insulated?

Many thanks and sorry for the basic question, learning on how to build amps!

Claude

Yes, as Astromo pointed out they are called insulating bushing or “shoulder washers”. Typically nylon but I have seen Teflon as well.

For example:
https://www.amazon.com/dp/B00KV6P828..._JRX.FbT4H9MM1

I am using ceramic insulator pad but silicone spacer is probably fine as the thermal flux is not huge.

[xrk971]

Originally Posted by pinkfloyd4ever

Looks good X. Do you know the model number of those heatsinks? I’m thinking they might work well for a MoFo

Indeed, I bought these for use in Class A like a MoFo. They are Dell T7500 LGA1366 CPU heatsinks. Typically surplus circa $20 a pair. They are nice and heavy. With a Noctua fan can easily handle 150w is my guess.

Dell Precision T3500 T5500 T7500 LGA 1366 Processor Heatsink 0T021F LOT OF 2 | eBay

[invaderzim]

Originally Posted by xrk971

The TDA7293 Xmas Amp is now playing music! ...

This is really exciting. Planning and building amps makes me feel like a kid looking at the Christmas catalogs.

[xrk971]

Originally Posted by Kay Pirinha

Great! I'm eagerly awaiting the boards now! Btw, is there some way elaborated already to provide our postage adresses to you and to enable you to calculate the s/h fee?

Best regards!

Now that we have two verification builds out of the way, we are ready to proceed to the address and shipment payment phase. The moderators told me to start a thread in the Swap Meet forum to do this and keep this thread for technical discussions. I’ll start that shortly. Since I am not allowed to use Etsy for handling the logistics of auto calculating shipment, I think the easiest thing for me is to charge approx flat rates similar to the past to cover PayPal fees, padded envelopes, and shipping labels.

Probably $5 in US, $8 Canada, and $15 everywhere else.

[xrk971]

Here is the link to the giveaway logistics thread in the Swap Meet forum.

Dibya’s TDA7293 Xmas amp by Jhofland - Giveaway

[xrk971]

Here are the final design files with the following changes:

1. Isolate the mounting bolt pads from the ground plane, except the top right bolt is connected to the ground via a ground loop breaker (opposed diodes, 10R resistor, and 100nF film cap, all in parallel)

2. Add third set of optional pads for Wima 4.7uF 250v MKP film cap at C1

3. Add 100k resistor to input pin upstream of input coupling cap.

4. Update BOM to show 47k5 resistor for R15 to allow DC servo to work properly.

New and final board layout (107mm x 65mm):

[xrk971]

I have been listening to the Xmas amp for two days now. Both on my 10F/RS225 TLs and my Rockville 2-way bookshelf speakers. It’s a great sounding amp. Smooth and very enjoyable. Can put out some power when needed. It’s quite amazing how easy it is to build. The startup is also very painless. Not a white knuckle experience like firing up some amps for the first time. With DC servo the offset is rock steady near 4mV no matter what.
I’m really enjoying mine!