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It is currently 28 Oct 2020, 12:47

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 Post subject: Slim Line 100W Class D
PostPosted: 04 Feb 2020, 13:56 
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Joined: 06 Jun 2008, 18:23
Posts: 5291
Location: Australia
This started as a 150W Class D amp, with hifimediy T3 Tripath modules in a 1U enclosure. But the amp had a quiet buzz I could not fix. I then changed it to a 25W single rail chip amp with passives on strip board. That didn’t play music though all voltages etc checked out.

I then saw on eBay a very small (about credit card size) 100W Class D module. And it’s only AU$20 delivered. It worked with the single rail 36V PS I had already made and looked squat enough to fit in the low 1U rack mount enclosure. The module is based on the TDA7498 chip and uses BTL technology. These enclosures are quite smart with an ash stipple finish, steel top, bottom plates and side brackets and Al back and front plates.

The finished amp is called “Image” and the name plate has been ordered. The module is rated 100W into 4 and 80W into 8ohms. Which means better than 70 clean watts before the usual 10% distortion stated with most Class D amps at full power.
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It sounds really excellent and drives my easy to drive Altec horns and 12” woofer well. Bass is very good and the rest of the frequency range appears well balanced. Plenty of power and would drive low sensitivity speakers with ease. Very happy and now I have my super slim line power amp, my own little Devailet which was the main reason I started this project in the first place.
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It doesn’t rival my Holton “Precision” amp with its extreme bass extension and control and sublime transparency but if you hadn’t heard the Holton amp you would never know what you are missing.


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Projects:"Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp | ”Salt Cellar II” - 6EM7 mono wine box triode amp |


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PostPosted: 28 Feb 2020, 23:57 
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Joined: 23 Feb 2020, 21:08
Posts: 11
Nicely done, good for you!

What do you plan to power with it?

I don't have anywhere near your electronics capability. I recently picked up a cheap 2.1 power amp board from Parts Express for less than $20 to power an old Dell sub for soft, mellow background music in my bedroom. I gutted the power amp due to lack of cabling and control for the sub.

I like the boards that can take an old power supply from a laptop computer's docking station or similar. I have access to a superabundance of 19.5v 6 amp and higher power supplies from HP laptop computer docking stations. It seems that the 100w Class D amp boards typically want 24v or even higher. I don't see voltages that high in computer gear, except HP printer power supplies. However those units don't require anywhere near the amps that the power amps require.

I've been experimenting with REW and some test mics. That app is quite powerful for a free utility.
viewtopic.php?f=11&t=6731


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PostPosted: 29 Feb 2020, 00:02 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
I use it with a tube preamp. It is powered by mains 240V and has a linear PS.

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Projects:"Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp | ”Salt Cellar II” - 6EM7 mono wine box triode amp |


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