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TPA3255 Reference Design Class D Amp GB

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#881
There are tube equivalents for an opamp based balanced buffer of course. They are not as simple to setup. As this is Class D already, I am not sure you are saving anything by eliminating opamps.

You can remove the opamps and use the balanced output of the HyperSET to drive the TPA3255 directly but note that the outputs of the HyperSET are opamp based balanced drivers.
 
#882
xrk971 said:
Hi Folks,
I am re-releasing the non-PFFB version of this amp (Rev001) as a bare PCB. Note that the commercial Warp-1 amp does not employ PFFB either. The sound of no-PFFB amp is superb and distortion is already low enough that I don’t really think it sounds better with PFFB. The DCDC buck converter that was out of stock for a long time is now back in stock, so that makes building this version much more attractive. There are some tricks that this PCB has compared to other TPA3255 implementations out there that still won’t sound as nice. Thick 2oz copper double stitched ultra-low impedance current paths where it matters, unique extra filtering on outputs, a layout that emphasizes low ground loop area, low impedance, and great symmetry.
Click to expand...
Sorry if I'm bothering you, but I just would like to better understand ways to connect the input signal to the TPA3255.

For example, the version without PFFB that you will re-release, configured in stereo BTL mode, could not eliminate the buffer circuit (opamps + resistors + capacitor), allowing the balanced signal from the previous source to be connected directly to the TPA3255 through of the 10uF input capacitors, eliminating as many components as possible in the signal path??

Do you also sell the assembled boards? In this case, how much should cost a fully assembled non-PFFB board?

Thank you for your kindness to this newbie! :worship:
Nilton
 
#883
Hi SoundBrazil,
I have not tested this but suspect one can do this by not populating any of the opamp circuits and associated components upstream of the 10uF coupling caps. Connect jumper wires from the input A/B/C/D Molex 3 pin connectors at the front to the upstream connection point of the 10uF caps. You could eliminate the caps if you can ensure that your own balanced drive circuit does not have any residual DC. Although that is not recommended.

So don’t populate any component upstream of the yellow boxes. It will be up to you to properly drive the balanced signals to achieve a BTL stereo input or mono parallel BTL input or SE quad input and select appropriate DIP switch settings to achieve this.

I don’t have any more populated (assembled) amp boards left in stock. They are all sold out and I don’t have any plans for more to be made in near future.

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#886
I have been getting several requests for getting another batch of these amps back in production again. I will need at least 10 units of interest for me to start another production batch.

Let’s start a signup for interest in another GB. You can get a discount if you buy it as a preorder during the GB signup. The preorder pricing will be $250 ea. After the preorder is over the regular price will be $327.

Please add your name and number of units here:

Name / Qnty
———————-
JohnDoe / 2 (example)
 
#893
I have the machined heatsink spreader in my shop. Then all you need to do is drill the 4 holes for the stand-off.

https://xrkaudio.etsy.com/listing/1070695614

I will provide these free of charge with every RTR amp order.

Boards are 120mm x 120mm. Corner M3 screw holes are 113mm x113mm spacing. Use 10mm brass M3 standoffs. To get the correct stickup height for the thermal block with silicone insulator sheet.

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#895
Yes. There is a 5th boss near GND Faston that is electrically conductive. That is optional. It is better practice to use a real ground wire to the Faston tab vs relying on contact for the boss. Note that the thermal spacer block is electrically contacted to the “power pad” thermal pad of the chip and this will be connected to local PCB analog ground. But should not contact chassis dirty ground. Hence, use a thermally conductive but electrically insulated spacer like silicone sheet.

Here is a video on how to install the board to an amp chassis with the thermal pad.

 
#898
Love the way this amp sounds, I built one from bare PCB with the panel mount BTSB, it was lots of fun!
Will it have Elna Silmic II for input caps? I am a believer that they do make a difference to how the amp sounds.
Would be great if it included the DC-DC buck converter, less cabling and not needing to source 15v from elsewhere, wouldn't mind waiting a little longer and slight increase in cost for the LM5010ASD and associated components.
 
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