TPA3255 - all about DIY, Discussion, Design etc

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chips666

Member
Joined 2007
Hello
To bypass opamps
For XLR connect + - signal to the inputs of the 4 little caps just next to heatsink
Enjoy...

See link: What is wrong with TPA3255? post 989
 

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turion64

turion64

Member
Joined 2019
Paid Member
Peterwitkin said:
Hello guys.

Does Anyone knows how to bypass input OP AMP on
The 3eaudio 2x260w board AMP ?

A picure could be a big help.

I do not need a lot of power and i would like to try to use it directly with a topping dx7pro (balanced output).

Thanks
Click to expand...

Someone mentioned (in another Forum; I’m trying to find the link) to just remove the op-amps and feed your input signals into the output pin/connections of the op-amps. The post had more information on the particulars of doing that

Cheers,

Pete
 
arizonavideo

arizonavideo

Member
Joined 2020
Peterwitkin said:
Hello guys.

Does Anyone knows how to bypass input OP AMP on
The 3eaudio 2x260w board AMP ?

A picure could be a big help.

I do not need a lot of power and i would like to try to use it directly with a topping dx7pro (balanced output).

Thanks
Click to expand...


That is exactly what I plan on doing. I bought a set of Nicron gold caps but think I will just go for the direct connection from my new DAC.
 
P

Peterwitkin

Member
Joined 2019
Thanks a lot for your answers. I'll try to contact linuxfan if i do not understand how to do this.


That is exactly what I plan on doing. I bought a set of Nicron gold caps but think I will just go for the direct connection from my new DAC
Click to expand...


I've found some infos here : https://www.diyaudio.com/forums/class-d/276982-tpa3251d2-145.html#post6186207

If i'm right, we can replace Op amp with this : 10pcs 8Pin DIP-8 SIP Round IC Sockets Adaptor Solder Type IL | eBay

and solder input from XLR as mentionned in the first link.
 
B

bucks bunny

Member
Joined 2020
chriscam said:
Thanks, I know, please see below where you will find the opamps use symmetric supplies. The question concerns the 1/2Vpp the tpa3255 outputs are on - typically 25.5V with a Vpp of 51V. Doesn't the dc imbalance between the driving opamp output (0V) and the OUT_X (Vpp/2) mess up the control loop ?
Click to expand...
I think this may work as long as dc current fed into the op-amps output is low (i.e. in the ballpark of 1mA). Otherwise you may insert dc decoupling caps into into the feedback network.
 
claredes

claredes

Member
Joined 2014
Hello guys!
Beginning of my vision for an amplifier integrated with the TPA3255.
I did that today.
Tomorrow I hope to be able to do more and maybe finish the job and listen to the amplifier.
 

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Rallyfinnen

Rallyfinnen

Member
Joined 2017
chriscam said:
Thanks, I know, please see below where you will find the opamps use symmetric supplies. The question concerns the 1/2Vpp the tpa3255 outputs are on - typically 25.5V with a Vpp of 51V. Doesn't the dc imbalance between the driving opamp output (0V) and the OUT_X (Vpp/2) mess up the control loop ?
Click to expand...

It seems to me the DC will be divided by R_fb (33k?) and R_in(2,7k?) which would make the DC offset before the input cap abt 0,08* the offset on the output.
As mentioned before, it would probably be the current that could do something to the OP-amp.
 
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Rallyfinnen

Rallyfinnen

Member
Joined 2017
cdsgames said:
I have made more progress . This new FFT was made after optimizing zobel network . Instead of one cap and one R I used 3 caps in parallel with 3 R in parallel . THD is 0.00045


Note also the absence of H3




I think that at this point this is the best measured TPA3255 (at 5W , 1Khz , 8R)
Click to expand...

I'm impressed by your measurement! Dominating H2 at such a low level! I ordered a 3251 Aiyima A04 the other day based on some subjective opinions (stupid I know), but after reading some more I started to regret the purchase.. This gives me some kind of hope that maybe it could be improved to a decent amp?
What do you find to be the critical areas? Could I ask for a short summary?
I know the chips and the boards are not the same, but chips are same family and I guess similar structure. Hoping to make something useful out of my impulsive purchase (when it arrives).
 
daniboun

daniboun

Banned
Joined 2019
I ordered a 3251 Aiyima A04 the other day based on some subjective opinions (stupid I know), but after reading some more I started to regret the purchase.. This gives me some kind of hope that maybe it could be improved to a decent amp?
Click to expand...

The Aiyima A04 (Tilear 2.1 version specially) is more than a descent amplifier, it is absolutely a great challenger amigo ! After some minor updates, you can get here an awesome amplifier. I own all TPA325X amps (including high ends one), just take a look to my reviews and also own some Hypex Ncore NC500MP + 250MP + 502MP and IRS2092 high end amps.

If you consider the price of this amplifier, it is probably (for me at least) the best Class D amplifier I listened to. (With OPA1656 + inductors update). $45 for the amp + $20 for the OP amps + $25 for inductors.


IMG-20200619-092930.jpg
 
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Rallyfinnen

Rallyfinnen

Member
Joined 2017
daniboun said:
The Aiyima A04 (Tilear 2.1 version specially) is more than a descent amplifier, it is absolutely a great challenger amigo ! After some minor updates, you can get here an awesome amplifier. I own all TPA325X amps (including high ends one), just take a look to my reviews and also own some Hypex Ncore NC500MP + 250MP + 502MP and IRS2092 high end amps.

If you consider the price of this amplifier, it is probably (for me at least) the best Class D amplifier I listened to. (With OPA1656 + inductors update). $45 for the amp + $20 for the OP amps + $25 for inductors.
Click to expand...

I'm interested if you have measured the Aiyima before/after mods? High power distortion is not critical for me (I play at neighbor friendly levels:), so I might not need to change inductors? It seems the PFFB is not implemented, so that worries me a bit too.
What worries me most it that high order harmonics seems to be quite high. I have seen this in other class D amps, and while adjusting output level, the high order harmonics are 'dancing around' varying a lot in level relative to each other etc.

I'm not sure what version the Chinese will send me..
 
daniboun

daniboun

Banned
Joined 2019
Rallyfinnen said:
I'm interested if you have measured the Aiyima before/after mods? High power distortion is not critical for me (I play at neighbor friendly levels:), so I might not need to change inductors? It seems the PFFB is not implemented, so that worries me a bit too.
What worries me most it that high order harmonics seems to be quite high. I have seen this in other class D amps, and while adjusting output level, the high order harmonics are 'dancing around' varying a lot in level relative to each other etc.

I'm not sure what version the Chinese will send me..
Click to expand...

I did not measure it... Rhing was supposed to send the same one as mine to Audio Science Review (with same tweaks). I was in touch with ASR and they proposed me to review the Aiyima A04 but got no news from Rhing....

But all I can say for now is that it sounds really great even with no PFFB enabled. Compared to the 3E Audio (that I also own) it is better for me. You can read some dithyrambic feedbacks in this forum. In any case he absolutely does not blush in front of my Hypex double Mono NC500MP.
 
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