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Improving TPA3118 Class D Amplifier


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captrajesh

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If you are willing to wait for 20+ days for it to reach you, these boards are available on eBay for ~US$6 with free shipping for 2 boards. BARGAIN!!!
Some months ago, I got them for ~US$3.50 for 2 boards. That was before they became famous on DIYA. :D
Could you kindly provide the link please?
 

SanjeevM

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Dheeraj, please try the 3118. Guaranteed you won't miss your big Class A;)
Dear JLS,

it is said that an o/p capacitor on this circuit can burst if the circuit is powered on without connecting the speakers. What value of resistance can be permanently connected on the terminals so that the speakers are never open-circuited?
 

jls001

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Dear JLS,

it is said that an o/p capacitor on this circuit can burst if the circuit is powered on without connecting the speakers. What value of resistance can be permanently connected on the terminals so that the speakers are never open-circuited?
Sorry, I'm not really aware of this. Now that you mention it, I can't recall if I ever tested it without connecting to speakers, but it's possible that I may have powered it up for the first couple of times without connecting a load, mainly because my "workstation" is pretty far from my audio rack.

Connecting a resistive load permanently in the output stage will change the characteristics of the output. Instead, one could connect a dummy load of say 8 Ohms rated for at least 10W for the duration of testing. It must of course be ensured that one operates at low power so as not to blow up the dummy load.
 

keith_correa

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Could you kindly provide the link please?
Captain, search for "3118 PBTL" on eBay and you should get tons of hits. But, I suggest that you don't bother with those [unless you want to have fun experimenting with mods] and get this instead - https://www.allo.com/sparky/volt-plus-amp.html. They're well designed, optimized, made and shipped from Bangalore [I think] for "Allo" and sold on amazon.in.

Edit: the Allo Volt+ Amp is also available here.
 
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jls001

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+1 to the Allo Volt+

Modding these boards is not for the faint of heart:)
 

captrajesh

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I suggest that you don't bother with those [unless you want to have fun experimenting with mods] and get this instead - https://www.allo.com/sparky/volt-plus-amp.html. They're well designed, optimized, made and shipped from Bangalore [I think] for "Allo" and sold on amazon.in.

Edit: the Allo Volt+ Amp is also available here.
Ok but I'm wondering how an amp costing 3.5 USD got escalated to 39 USD just with some mods here and there. The other day I was interacting with Joshua who seems to be convinced of the cost escalation but still, I'm wondering! Any comments?
 

SanjeevM

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On the 3116D2 amp page, as well as on a Tube based DAC page I have come across the warning "Do not use a Linear Power Supply" I am confused, what could the reason for this be, since linear regulated supplies are less noisier than SMPS supplies, and therefore suited to Amp applications!
 

jls001

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I've never come across this warning. Can you post url? It would be interesting to learn why.

One good reason I can think of for using linear supply is high cost:)
 

HormusPeston

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These Class-D amps are very similar to an SMPS, which can misbehave when not loaded. But I don't fully understand why they would warn against using a linear power supply. Perhaps if the amp develops a fault, the reservoir condensors might dump a bucket-load of charge into the amp? I'm not sure. But an amplifier with 90% efficiency is a good thing for our planet. A fellow member on these fora just finished making a cute little monster with 15% (?) efficiency!
Cheers,
~hp
 

omishra

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Warning against linear power supply is BS. I am using class T (which similar to class D) since last 12 years. Only switching it off during night 11pm to morning 7am. Nothing happened to it. Only thing you need to take care of is, don't connect or disconnect input or output wires, including grounds while its on. Because this somehow changes internal floating voltage levels such that output driver MOSFETs either driven to death by destroying gate or big DC pulse through load. With proper DC detect and speaker protection it could be avoided.

Or Chinese English, wanted to say don't connect transformer directly, rather use DC power supply like SMPS.
 
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SanjeevM

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That seems more like it. They are warning us not to connect a trafo directly, in Chinese English.
 

SanjeevM

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The 3116 amp is very resolving and clear. It plays bass guitars very well. It lacks the thump-thump of bass drums. How can the bass punch of the 3116 amp be improved?

The circuit requires a 24v 3A supply. I am using a 24v 5A SMPS currently. Will a linear PSU 24v 8A with a 60000 uf capacitor bank make a significant difference in this regard ?
 
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HormusPeston

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This might seem obvious but does any other amplifier, when connected to your system, adequately reproduce the thump that is missing? Only if that is true should you investigate the amplifier you built.
Does the amp sound as if it is clipping when it plays the "thumpy" parts? A simple 'scope will confirm this. Cheers,
~hp
 

SanjeevM

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This might seem obvious but does any other amplifier, when connected to your system, adequately reproduce the thump that is missing? Only if that is true should you investigate the amplifier you built.

Does the amp sound as if it is clipping when it plays the "thumpy" parts? A simple 'scope will confirm this. Cheers,
~hp
Yeah, I am comparing the output of 3116 with the Yamaha HT Amp. The YHT produces the thump but the 3116 does not, on the same tracks.

The 3116 does not sound as if it is clipping, it just does not have the thump in its o/p. Maybe its the Boss DAC, but that DAC is known for better bass o/p, and it has a dedicated supercapacitor too.
 

jls001

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The circuit requires a 24v 3A supply. I am using a 24v 5A SMPS currently. Will a linear PSU 24v 8A with a 60000 uf capacitor bank make a significant difference in this regard ?
I doubt that a big cap bank will improve the bass response. What a big cap bank is supposed to do is provide instantaneous energy when the program material calls for it (like sudden dynamic peaks).

In general I find the bass weight of 3118 lesser than two other amps I compared it to (this is only in relative terms - it has enough bass heft in my system for my taste), but the deficiency in bass weight is in some way made up by the texture of the bass. It brings out the tonality of the bass much better, for example, than the LM3886 based MyRef Rev C amp (though MyRef has more bass weight).
 

greenhorn

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I have seen this comment about reduced bass response for a lot of T amps - even saw the same for my TDA7498E. wonder why
 
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