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suggestion/ help needed - DIY class D integrated stereo amplifier - 2 X 100W @8ohms

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sonus

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Hi Guys, I'm new to audio amps & speakers.

I was thinking about making an amplifier as the title suggests - class D integrated stereo amplifier with 2 X 100W @8ohms. Any help/sugeestions as to where to start?
 

jls001

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TPA3255 Evaluation Boards are available at 50% discount right now directly from Texas Instruments US website. At this price there's no reason to buy the Chinese boards.

More than meets your power requirement. It's claimed by users that sonically it's a substantial improvement over the older TPA31xx based amps. It is also quite flexible and can be configured in multiple ways. This board accepts either a pair of single ended analog inputs, or a pair of true differential inputs.

Also available direct from from TI is the TAS5634 EVM board (costlier, and I don't know if there's discount going on). It accepts I²S, USB and coax inputs. No analog input. Very similar power ratings as the TPA3255.
 

sonus

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TPA 3255 EVM on TI is $150 + shipping + taxes, is that the discounted price?
 

sonus

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Another question, when they specify details like:
Output Power at 1%THD+N
– 465 W / 3 Ω PBTL Mono Configuration
– 240 W / 6 Ω BTL Stereo Configuration
– 180 W / 8 Ω BTL Stereo Configuration

so does it means that at 8ohms, the output will be 90W per channel?
 

jls001

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Another question, when they specify details like:
Output Power at 1%THD+N
– 465 W / 3 Ω PBTL Mono Configuration
– 240 W / 6 Ω BTL Stereo Configuration
– 180 W / 8 Ω BTL Stereo Configuration

so does it means that at 8ohms, the output will be 90W per channel?

180W into 8 Ohms BTL Stereo is at 10% THD+N.

The more relevant figure for home users is:

Advanced Integrated Feedback Design with High-speedGate Driver Error Correction
(PurePath™ Ultra-HD)
  • Signal Bandwidth up to 100 kHz for High Frequency Content From HDSources
  • Ultra Low 0.006% THD+N at 1 W into 4 Ω and <0.01% THD+N toClipping
  • >65 dB PSRR (BTL, 1 kHz, No Input Signal)
  • <85 µV(A-Weighted) Output Noise
  • >111 dB (A Weighted) SNR
We won't be using more than 20W or so for driving speakers with nominal efficiencies of 86-88 dB. At such power levels the distortion figures will be vanishingly low. My TPA3118 PBTL is rated for 60W/10%. I've never heard clipping or distortion when driving my 86 dB speakers to very loud SPLs. So the 3255 will have lots and lots of headroom. I would conservatively estimate it will have a very clean 75W (3 dB down for the 1% THD+N figure of 150W/8Ohms).

Discounted price is $75 after you register with TI and log in.
 

stefan

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180W into 8 Ohms BTL Stereo is at 10% THD+N.

The more relevant figure for home users is:

Advanced Integrated Feedback Design with High-speedGate Driver Error Correction
(PurePath™ Ultra-HD)
  • Signal Bandwidth up to 100 kHz for High Frequency Content From HDSources
  • Ultra Low 0.006% THD+N at 1 W into 4 Ω and <0.01% THD+N toClipping
  • >65 dB PSRR (BTL, 1 kHz, No Input Signal)
  • <85 µV(A-Weighted) Output Noise
  • >111 dB (A Weighted) SNR
We won't be using more than 20W or so for driving speakers with nominal efficiencies of 86-88 dB. At such power levels the distortion figures will be vanishingly low. My TPA3118 PBTL is rated for 60W/10%. I've never heard clipping or distortion when driving my 86 dB speakers to very loud SPLs. So the 3255 will have lots and lots of headroom. I would conservatively estimate it will have a very clean 75W (3 dB down for the 1% THD+N figure of 150W/8Ohms).

Discounted price is $75 after you register with TI and log in.
You may or may no get hit with import duties also, if you can get them, they're apparently very good.

Others you can consider are connex (European fellow based out of hong Kong), hypex (Holland) and class d audio(US) I personally am going with connex as there's a great write up on pfm forum, the differences won't be so great, your speakers will play a more important role imo.
 

jls001

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Do add shipping cost of about $18 too.

Customs is a shot in the dark, a Russian Roulette, etc:)

Also, the wattages mentioned in the spec sheet are all per channel output figures so no need to halve them.
 

sonus

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180W into 8 Ohms BTL Stereo is at 10% THD+N.

The more relevant figure for home users is:

Advanced Integrated Feedback Design with High-speedGate Driver Error Correction
(PurePath™ Ultra-HD)
  • Signal Bandwidth up to 100 kHz for High Frequency Content From HDSources
  • Ultra Low 0.006% THD+N at 1 W into 4 Ω and <0.01% THD+N toClipping
  • >65 dB PSRR (BTL, 1 kHz, No Input Signal)
  • <85 µV(A-Weighted) Output Noise
  • >111 dB (A Weighted) SNR
We won't be using more than 20W or so for driving speakers with nominal efficiencies of 86-88 dB. At such power levels the distortion figures will be vanishingly low. My TPA3118 PBTL is rated for 60W/10%. I've never heard clipping or distortion when driving my 86 dB speakers to very loud SPLs. So the 3255 will have lots and lots of headroom. I would conservatively estimate it will have a very clean 75W (3 dB down for the 1% THD+N figure of 150W/8Ohms).

Discounted price is $75 after you register with TI and log in.

the spec mentioned in my post was for TAS5634, anyway, the point is that is the wattage mentioned in that spec for each channel or is it combined ch1+ch2 ------------- Understood from above post, it is per channel

Regarding the power requirements/utility. If i use a pair of tweeter rated 15-30 W & Woofers rated 60-85 W, what should be the power of the amp I would need?
 
Last edited:

sonus

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180W into 8 Ohms BTL Stereo is at 10% THD+N.

The more relevant figure for home users is:

Advanced Integrated Feedback Design with High-speedGate Driver Error Correction
(PurePath™ Ultra-HD)
  • Signal Bandwidth up to 100 kHz for High Frequency Content From HDSources
  • Ultra Low 0.006% THD+N at 1 W into 4 Ω and <0.01% THD+N toClipping
  • >65 dB PSRR (BTL, 1 kHz, No Input Signal)
  • <85 µV(A-Weighted) Output Noise
  • >111 dB (A Weighted) SNR
We won't be using more than 20W or so for driving speakers with nominal efficiencies of 86-88 dB. At such power levels the distortion figures will be vanishingly low. My TPA3118 PBTL is rated for 60W/10%. I've never heard clipping or distortion when driving my 86 dB speakers to very loud SPLs. So the 3255 will have lots and lots of headroom. I would conservatively estimate it will have a very clean 75W (3 dB down for the 1% THD+N figure of 150W/8Ohms).

Discounted price is $75 after you register with TI and log in.
I am registered on Ti, still it shows $149
 

sonus

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Do add shipping cost of about $18 too.

Customs is a shot in the dark, a Russian Roulette, etc:)

Also, the wattages mentioned in the spec sheet are all per channel output figures so no need to halve them.
customs no issue, someone is arriving from USA. Only thing is the discount.
 

sonus

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Discount code "highpoweraudio" at checkout.
Thanks, it works. Also, using the code, shipping is free within US.

Regarding the power requirements/utility. If i use a pair of tweeter rated 15-30 W & Woofers rated 60-85 W, what should be the power of the amp I would need?
 

Aniket

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jls001

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Regarding the power requirements/utility. If i use a pair of tweeter rated 15-30 W & Woofers rated 60-85 W, what should be the power of the amp I would need?

I think this really depends on whether or not you plan to push the drivers hard. The general wisdom is one should not send clipped signal from amp to speakers as a clipped signal can damage drivers, especially tweeters. One can go easy on the volume knob and keep the amplification chain well within its linear range to avoid clipping, OR use amplifier with sufficient headroom and push the drivers hard to their maximum capability. The second scenario is very unlikely because our ears will give up long before the drivers give up.

To answer your question, buy a high powered amp if you'll be playing sustained high SPLs. Otherwise many here would testify that their 40-50W amps can more than drive their speakers to stupidly loud SPLs. Of course how good/bad am amp sounds is hardly correlated to its output power.
 

sonus

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I think this really depends on whether or not you plan to push the drivers hard. The general wisdom is one should not send clipped signal from amp to speakers as a clipped signal can damage drivers, especially tweeters. One can go easy on the volume knob and keep the amplification chain well within its linear range to avoid clipping, OR use amplifier with sufficient headroom and push the drivers hard to their maximum capability. The second scenario is very unlikely because our ears will give up long before the drivers give up.

To answer your question, buy a high powered amp if you'll be playing sustained high SPLs. Otherwise many here would testify that their 40-50W amps can more than drive their speakers to stupidly loud SPLs. Of course how good/bad am amp sounds is hardly correlated to its output power.

I guess 50-60 W would do the job then, and that should be the output figure at 1% THD, to preserve SQ.
 
Last edited:

sonus

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Another question that comes to my mind, if you refer the below image, you'll see the power o/p is given for 2 ohms, 3 ohms & 4 ohms. Should this amp be able to drive 8 ohm drivers? why?

1.jpg
 

SanjeevM

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I am using this 3251 chip to drive my Paradigm Monitor towers which are 8 ohms.

Though I haven't measured, this chip produces quite a loud sound. I have had to put a restriction of 70% volume on the Volumio player software !!
 
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