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Class D Switching Power Amplifiers and Power D/A conversion

TPA3250 somebody is listening?
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Old 4th December 2017, 10:07 AM   #11
ICG is offline ICG  Germany
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If the delivered amp is identical with the ebay photos, it got a few very nice features, the preamp OPs (the NE5532) are socketed, that's remarkable. You can easily replace them without any soldering, experiment with different/better OPs etc. The output inductances are air cores, they don't get saturated and start harsh distortions like ferrite ones do if they are too small. Also a nice-to-have is an error-/protection LED.

I haven't heard it but it looks quite promising. On high volumes it will likely profit from a bigger power supply though.
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Old 4th December 2017, 10:20 AM   #12
KaffiMann is offline KaffiMann  Norway
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Or rather, if you require more undistorted power get the TPA3251 or the TPA3255.

I do not know about the performance of the supplied psu, but 24v 4a may be a very balanced choice for this chip. You get "good enough" performance up to 25w/channel in 8 ohm, and 40-45w/channel in 4 ohm.
Otherwise the distortion starts setting in just over 30-35w/channel in 8 ohms and 60-70w/channel 4 ohm anyway, regardless of power supply and voltage. Need more power? Get something else.

Edit:
The numbers are a bit better at 30V supply,still very good for 4ohm loads, but the difference is not humongous, and 24V supplies are probably cheaper.

Edit2:
Just ordered two of these.... Splurged 4$ on shipping to get it just a little bit faster.

Last edited by KaffiMann; 4th December 2017 at 10:38 AM.
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Old 4th December 2017, 10:46 AM   #13
ICG is offline ICG  Germany
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Quote:
Originally Posted by KaffiMann View Post
Otherwise the distortion starts setting in just over 30-35w/channel in 8 ohms and 60-70w/channel 4 ohm anyway, regardless of power supply and voltage. Need more power? Get something else.
While that (distortion) is true, I honestly doubt you'll get 2x70=140W (without any losses!) out of a 96W power-brick. And why add the distortion from the PS and the amp if you can avoid it? Sure, you'll rarely use that much power but that's saving at the wrong end IMO.
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Old 4th December 2017, 10:50 AM   #14
KaffiMann is offline KaffiMann  Norway
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That was "regardless of power supply and voltage", on 4 ohm loads the spec sheet do not recommend loading more than 60W/channel and you get that on ~30V.
On 24V I expect good quality sound up to 25W/channel 8ohm and 40-45W/Channel in 4ohm.
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Old 4th December 2017, 11:07 AM   #15
ICG is offline ICG  Germany
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That's still rather tight for such a power brick, remember, a lot of speakers got quite the dips in the impedance at some point which means it will draw more power with some 'luck'. That will not burn up the power brick but that's saving on the wrong end, why waste potential? These PS aren't very expensive. If you say 'that's enough for me', that's fine. I, personally, would want to use the full potential and I don't like driving PS over the edge, a beefier PS usually lives longer. I like relyability.
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Old 4th December 2017, 11:19 AM   #16
KaffiMann is offline KaffiMann  Norway
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I agree.
But for my intended application I doubt I will ever see 20W on peaks in 8 ohms. And was considering doing this "dual mono" with two amps, each amp uses one channel for the 8ohm load, and one channel for the 4 ohm load. The 24V PSU is free, and it gives me more power than I need from this amp.

If I'm not happy then there are other places they are needed. Need a replacement for my 70's Nikko amp while it gets refurbished, need some new caps, switches and potmeters (both volume and channel panning is worn). Basic cleaning does not work any more.

Edit:
If I'm not happy with the supplied power unit, I got 4x12V SLA sitting around doing nothing that will work great.

Last edited by KaffiMann; 4th December 2017 at 11:24 AM.
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Old 4th December 2017, 11:48 AM   #17
TNT is offline TNT  Sweden
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Quote:
Originally Posted by KaffiMann View Post
I agree.
But for my intended application I doubt I will ever see 20W on peaks in 8 ohms. And was considering doing this "dual mono" with two amps, each amp uses one channel for the 8ohm load, and one channel for the 4 ohm load. The 24V PSU is free, and it gives me more power than I need from this amp.

If I'm not happy then there are other places they are needed. Need a replacement for my 70's Nikko amp while it gets refurbished, need some new caps, switches and potmeters (both volume and channel panning is worn). Basic cleaning does not work any more.

Edit:
If I'm not happy with the supplied power unit, I got 4x12V SLA sitting around doing nothing that will work great.
Please report back on your findings once delivered and tested.

//
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Old 4th December 2017, 03:28 PM   #18
dellama is offline dellama  United States
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The 325X distortion number seems pretty good but does anyone know its harmonic profile? What about its IMD numbers? To me, these class D amps are not really meant for home hifi. Their application should be limited to portable sound reproduction. I will admit that when you start getting under 500 ppm distortion, you're getting into the 'acceptable' range but like in all things, the devil is in the details.

FauxFrench
I've heard lowering the input impedance on these amps helps with the noise. I've been looking at some cheap 3116D2 boards that are all SMD. Their ~25x37mm size allows you to mount a legacy CPU heatsink of any size. The chip is the tallest part on the board. Have a look here.
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Old 4th December 2017, 04:46 PM   #19
doctormord is offline doctormord  Germany
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Thats a nice little amp, even if they use "low cost" dcdc converter parts and do this strange opamp swap-mount thingie. I first thought, there's a differential linedriver on the middle right (pcb) but this seems to be some kind of microcontroller?

@dellama, the TPA324X/5X series does <500ppm with ease at a wide range of listening levels.
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Old 4th December 2017, 05:03 PM   #20
dellama is offline dellama  United States
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Yes, .01% is the specification claim for that chip but depending on the mix of the harmonic profiles, this can sound less than great. It's certainly inferior to the single digit ppm distortion, low noise floor and organized harmonic profile efforts achieved with class AB and composite amps. The other problem I foresee with ALL class D chips is the high frequency non-linearities (>6K) which are bound to diffuse the ambience and soundstage of playback. I haven't heard enough of these to make any final judgment on them but so far, I'm inclined to reject class D for anything other than portable sound. I just ordered a pair of those mini boards to play with. I suspect you'll be interested in their development if you haven't bought a pair for yourself already. Did you note my comment on the main TPA3116 thread about the meager capacitance on this mini board?

Last edited by dellama; 4th December 2017 at 05:06 PM.
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