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Improving TPA3118 Class D Amplifier

jls001

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From the datasheet:
I checked my stock - I have only two pieces of 3.3 uF polystyrenes. And they're huge, probably half the size of the 3118 board. I'll use the Elna Silmic II as I have sufficient.
 
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jls001

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So I tried changing the input caps as suggested earlier. I used 10 uF electrolytic as that's what I have in stock. The datasheet circuit shows one 1 uF cap each on the positive and negative leads of the input, so I inserted one 10uF cap on each lead. I measured the combined capacitance and was surprised to see that they measured nearly 15 uF. So the caps used in my boards are actually about 4.7 uF and not 1 uF suggested in the datasheet circuit. 4.7 uF was actually close to the correct cap value for my gain setting of ~26 dB.

At one point I actually got both channels to play properly and could listen to the change, if any. I have to truthfully report that I didn't hear improvement in bass.

Later, I removed the original 4.7 uF SMD caps so that the value of cap is 10 uF which is the highest recommended value (though it's not the value recommended for my gain setting). This last exercise turned out to be my undoing - while desoldering the two SMD caps, the thin traces of the board peeled off. End result is both boards are beyond my ability to see clearly to troubleshoot further. The traces and SMD components are genuinely small unless one has a good, wearable magnification device.

While I was at it, I also separated the trace for the signal and power grounds on the bottom side of the board.

Since the sound of the TPA3118 is genuinely good to my ears, I'll get two fresh PBTL boards and rebuild them.

Mods to be done will NOT need me to desolder SMDs or solder on top of existing SMD leads. I'll stick to default gain of 32 dB that the board comes with, and only tinker around with changing the four power decoupling caps (coupling caps are SMD but they sit on much larger board traces) and bootstrap snubbers. These two mentioned mods are what matter sonically, so I'll stick to what makes a difference.
 

Pygmy

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Does anyone know a suitable power cap replacement (low esr) to use with 24v power? I assume the standard 25v suggestions (Panasonic oscons 330uf 25v) don't have enough margin for 24v input..?
 

jls001

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I'm building PeeCeeBee v4H.

I seriously considered the 3255 but had doubts about sourcing a good SMPS so I thought I'll stick for now with good old AB amp.

My 3118s conked off due to my over zealous mods. Need to buy two boards again and at least restore them to working status:)
 

SanjeevM

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I have one to spare, which is very good, and needs no mods. PM me if you want it.
 

jls001

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Have you finished your PeeCeeBee v4H?

As I also have a MyRef amp, I wonder how the v4H compares to it.

Yes, I have completed building the PeeCeeBee v4.

I have done small changes in the internal wiring to suit my listening tastes.

I find the sound signature of PeeCeeBee v4 much more to my liking than the MyRef Rev C. It is much more neutral compared to the warmth of MyRef Rev C. It is also more resolving. Its bass is really good - both weight and texture. And the v4 has very consistent biasing facilities (I struggled quite a bit with MyRef). I would suggest you to build the v4 or better yet the v4H.
 

saikatbiswas82

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Moving slowly towards class d amps. There are so many threads going on diyaudio on this interesting topic. Some are saying that TAS5630 is better than TPA amps. However need to do a side-by-side comparison to decide.

I've already tested TAS5630 in my setup and liking it very much. Yet to test IRS2092 based amps.
 

carlmart

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Yes, I have completed building the PeeCeeBee v4.

I have done small changes in the internal wiring to suit my listening tastes.
Can you specify what changes are those?

I find the sound signature of PeeCeeBee v4 much more to my liking than the MyRef Rev C. It is much more neutral compared to the warmth of MyRef Rev C. It is also more resolving. Its bass is really good - both weight and texture. And the v4 has very consistent biasing facilities (I struggled quite a bit with MyRef). I would suggest you to build the v4 or better yet the v4H.
What are the differences between V4 and V4H? Which did you build?

What did you struggle with on the MyRef bias? Can you tune it?

Have you seen any LTSpice simulations for the V4 or V4H?
 

jls001

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Can you specify what changes are those?

What are the differences between V4 and V4H? Which did you build?

What did you struggle with on the MyRef bias? Can you tune it?

Have you seen any LTSpice simulations for the V4 or V4H?
Changes:

1/ replaced all silver plated copper wires used for Vcc and Vee and speaker wires inside the amp, to tinned copper. With silver plated copper there was a midbass bump which I didn't like. The tinned copper moved this midbass bump further down and gave a sense of deeper bass. But more importantly, the tonality with tinned copper is much more to my liking.

I built the V4. V4H is much more powerful and is supposed to be more refined than the V4 (from what I could gather in the V4H thread on diyaudio).

My MyRef Rev C kept blowing the R11 (1R) even after swapping out to higher wattage. I used the Rev C for several months after it was completed but it started giving me the same problem and I gave up on it.

LTSpice simulation is probably available on the relevant threads in diyaudio. Please check the threads.
 

carlmart

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My MyRef Rev C kept blowing the R11 (1R) even after swapping out to higher wattage. I used the Rev C for several months after it was completed but it started giving me the same problem and I gave up on it.
I don't remember what R11 linked on the MyRef schematic: can you refresh me? It seems like you some kind of oscillation.

But if you had that problem, how could you compare the MyRef to the class D and V4 amps?
 

jls001

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I don't remember what R11 linked on the MyRef schematic: can you refresh me? It seems like you some kind of oscillation.

But if you had that problem, how could you compare the MyRef to the class D and V4 amps?
R11 is from MyRef Rev C schematic of Linuxguru's board, so the component numbering may be different in other boards. The value is 1 Ohm.

3118 was built just after completing MyRev so I could listen to both. MyRef decommissioned long back after it failed again. 3118 too unused after my mods ended up destroying one of the PBTL mono boards and I didn't buy a new board. Both these happened many months ago (if not a year at least).

V4 completed recently. So no occasion to compare it directly to MyRef and 3118. My comparison is only from audio memory so may not be most accurate.
 

carlmart

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Looking around, I think I found a dual TPA3116 that carries all the mods to make it sound better, like the original SMD 330uF electrolytics you changed (replaced here with 2200uF caps) and film caps on the output, instead of ceramics:

https://www.ebay.com/itm/DC-12-24V-TPA3116D2-HIFI-Digital-2-0-Dual-Channel-Stereo-Amplifier-Board-50W-2/312259025137?_trkparms=aid=222007&algo=SIM.MBE&ao=1&asc=20131231084308&meid=2d22f6f4a5eb4a59a8ac097ff87fa1ce&pid=100010&rk=2&rkt=12&sd=173487748738&itm=312259025137&_trksid=p2047675.c100010.m2109
 
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