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Class D Switching Power Amplifiers and Power D/A conversion

TPA3255 - all about DIY, Discussion, Design etc.
TPA3255 - all about DIY, Discussion, Design etc.
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Old 15th October 2018, 02:33 PM   #911
doctormord is offline doctormord  Germany
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Point, i assumpted same efficiency for both tops and sub.
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Old 17th October 2018, 05:50 PM   #912
jimk04 is offline jimk04  United Kingdom
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So my MW SPV 300 48 .....fan spins all the time so I disconnected. It gets warm.....pretty warm. Not measured. Will do tonight.

Bought some 82r 2 watt res to slow it down. Soldered it all up. Fan still spins like hell. Realised I was sent 0.1R!

I also can hear the pwm of the smps. Even at decent levels watching TV. I must have bat ears.! It is just sat on the rack at the moment. It isnt in a case but I intended to run it this way but the noise will be a factor now.

What is normal temps for the 3255 board.? Or indeed safe temps for components? I have 3e. 48v and decent listening levels for an hour and more and coils and caps nudging 40c. Heatsink mid 30s. MW SMSP case is more than just warm.
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Old 17th October 2018, 07:41 PM   #913
doctormord is offline doctormord  Germany
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Without knowing your ambient temperature it’s hard to tell but 40degC fr coils n caps is just normal. The coils heat up the caps by radiation and trace conduction. Nothing to worry about. For the heatsink, they work best when they’re hot.
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Old 18th October 2018, 07:15 AM   #914
jimk04 is offline jimk04  United Kingdom
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Thanks doc. Ambient room temp approx 19C. Smps doesn't have a lot of free air. And is amongst other warm components.

I tucked it behind the centre speaker last night and is much quieter. Shame as I was going to put a nice wooden fascia on it and have it visible as I quite like the aluminium enclosure.
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Old 26th October 2018, 08:03 PM   #915
Jakobie is offline Jakobie
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Do you guys think a 57v supply is too much? I can get tons of these things for free and would be nice to use on the TPA3255.
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Old 26th October 2018, 09:24 PM   #916
multisync is offline multisync  Canada
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I think the max recommended by TI for a 6 ohm or greater load is 56 VDC. The absolute max rating is 69. Spike maybe or transient. A couple of diodes in series and you will be in the ballpark for a 6 ohm load. I will be doing the same thing.

I rescued a power transformer from an old dead 5 channel receiver. It gives 57.5 vdc with no load. I will put 2 full wave bridges in series.

check the power supply under load and see how much it drops,
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Old 26th October 2018, 09:43 PM   #917
Jakobie is offline Jakobie
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56.3V under 8Ω load
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Old 29th October 2018, 12:29 PM   #918
doctormord is offline doctormord  Germany
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Quote:
Originally Posted by multisync View Post
I think the max recommended by TI for a 6 ohm or greater load is 56 VDC. The absolute max rating is 69. Spike maybe or transient. A couple of diodes in series and you will be in the ballpark for a 6 ohm load. I will be doing the same thing.

Keep in mind:
"For load impedance ≥ 6Ω PVDD can be increased, provided a reduced over- current threshold is set."


Quote:
The absolute max rating is 69

Take note, that this is DC + Peak AC and includes filter ringing, switching spikes etc. at the output. I wouldn't recommend going further than 56.5V with reducted OCP-Trippoint.

Last edited by doctormord; 29th October 2018 at 12:33 PM.
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Old 2nd November 2018, 01:51 AM   #919
pblossom is offline pblossom  United States
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Default IEEE Article

Build Your Own Professional-Grade Audio Amp on the Sort of Cheap - IEEE Spectrum
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The human capacity for self delusion is nearly infinite.
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Old 9th November 2018, 08:54 AM   #920
MirageZA is offline MirageZA  South Africa
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Default PFFB on TPA3255

Hello Friends,

My first post here :-)

I have acquired 2 TI modules, one for reference and other one for mods. So far I have replaced NE with OPA1612, there is subtle, positive sonic difference.

TPA3255 - all about DIY, Discussion, Design etc.-img_0092-jpg


For now, I'm using linear bench power supply, 30V/6A. I have noticed that both modules have ever so slight hiss (you really have to put your ear next to twitter) - OP amp change made no difference so I presume it's TPA3255 itself.

As I don't intent to play at full volume, I don't have a problem with lower gain and would like to try PFFB implementation, as per TI's schematics.

TPA3255 - all about DIY, Discussion, Design etc.-screenshot-2018-11-09-10-14-17-png


My question - is it worth to try? Coming from old school amplification, a little bit of negative feedback is good. How about 3255, can I expect lower noise floor (less hiss in my case).
In my view, PFFB is more elegant solution than coil/caps mods on the output.

Many thanks for your help!
Alex
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