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Transformer-fed TDA8932 25W/8R mono amp kits

Hello, everyone,
I've finally been able to assemble my mono amps r3.😊 And what can I say, they sound really good. Not at all like other Class-D chips I know. Very warm sound. I can really recommend these things. Many thanks and respect first and foremost to Richard for your efforts. But also to everyone else who provides support and Ideas here. Shipping and packaging were very good!

I would like to use one Meanwell SMPS per amp. A DCDC converter should then be attached to one of the SMPS, which should supply an ADAU1701 board with 5VDC. Signal source would be a Iphone5s. Now to my question: Should everything have a common ground? Or should I use an isolated DCDC converter for the DSP? Signal ground has to be connected anyway...

Fertige Boards.jpg

regards
Henning
 
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With transformer isolation as at the input to these amps, there could be hum if the primary is allowed to float with respect to the amp's 0V. So I would say don't bother with the isolated DC/DC. a normal buck regulator will be fine.

Thanks for your encouraging feedback.
Thanks for the fast respond.
I'll try that and let you know how it went. :)
 
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Hi everyone...a little late to the game here but assembled the two boards and did a power on test with an 8 ohm load on outputs and 12VDC then 24VDC powering the board. Using the shunts instead of LM317s. Yellow lights on both boards! Waiting for a chassis to get them fully assembled and test with music. What a fun little amp build. Hoping for not your typical Class D sound. Thanks Richard!
 

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Finished assembling boards in the chassis and powered it up with a single 24V 2.5A power brick. No hum or obvious noise out of the speakers. Didn't measure any appreciable mV DC offset out of the speaker outputs either. Listened for 30 min then grounded the signal input grounds to the 0V of the power input. Might have made the HF signal a bit cleaner but that could be a biased observation. Very nice soundstage with no muddiness even with my preamp that only has a 10uF film cap as a DC blocker on it signal outputs. An airiness to classical music not heard with any other Class Ds but we'll see after I hook it up in my main listening room. I'll keep it on the test platform for a few days yet.

Again, thanks to Richard for this little gem.

Pictures aren't uploading for some reason. Will try again later

Pete
 
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So I've been playing these with various preamps and they don't have the typical Class D sound of the 3255-based amps I have. They have an even response, a nice bit of airiness but I want to try for more sparkle at the upper end (all classical music listening). They are non-fatiguing and have different character depending on the preamp used.

Preamps tested were Wayne's BA2018, Pete Millett's NuHybrid Nutube-based headphone/preamp, Nelson Pass's BA3 & B1Korg. The most lyrical, so far, is with Pete Millett's NuHybrid Nutube headphone/preamp with Sparkos opamps in place of the stock BOM opamps. Since I've (biasedly) found that all of the preamps , whose PS's that can use Sparkos Regulators in place of the normal 78xx & 79xx regs, just always sound cleaner and more defined, I think I'll take the experience of Shertzy and try Sparkos regs at the U3 position to see what that brings. Granted the idea of this project is a wonderful sound out of a simple, inexpensive Class D circuit and adding $100 USD of regulators seems a bit absurd but I want to love this amp. It's a marvelous sounding low powered amp.
 
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But, re-reading Richard's original statements in post #1 I fear I may be under-powering the two boards (amperage wise) so I bought a Mean Well LRS-150-24 which is rated at 24V & 6.5A. Before I spend the money on any Sparkos regulators to try, instead of Richard's shunts, this would be a cheaper option.

Pete
 
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I find if I run a good amperage SMPS on a low ish requirements of class d amps that the PSU seems to give if a PWM 'noise '. I get it with my Tracopower 24v. I forget their spec but I think 4A each....I ran one or channel and I could hear a sound coming from the PSU itself. Not from the speakers. Same PSU on an ACA Mini and silent. Have read about loading SMPS with a power resistor to shut them up
 
When a SMPS is emitting noise, it often comes from not properly wound coils/inductors. There is an easy fix, just put some little drops of a good super glue on them and they are dead quiet. Of course let the glue completely dry out before powering the SMPS again. The glue should not be heat sensitive. I have made this "mod" on a lot of SMPS and it always worked.
 
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Just a FYI, I've built up a r6 version of the amp and used Richard's IR shunts and my bias is that they makes the amp sound more clear and open. Bass impact is still quite good. I'm awaiting the delivery another set of IR shunts to put into the r5 version boards I own to replace the normal shunts. Sparkos regs have also been tried in the r5 builds. I've never tried the stock regulators at U3.

Cheers