TI TPA3255EVM

Given there are 5 different boards on offer from TI, beyond looking at the 3255 because it can put out the most power, what other reasons are there for picking one amp over the other? I have 96db 8 ohm speakers and was wondering if one of these amps in particular is better matched for these speakers. Or does it really not make that much difference as I would be listening at fairly low power?
 
The 3251 within the same power envelope is a little higher performance and, since you're not likely running these guys at full power, will have a bit better signal to noise ratio (ultimately we never want both gain and attenuation in the same path). Not sure if the smaller amps have any advantage when the evm's all cost the same amount.

I have too much gain with my 3255 but went big for ostensible future proofing and since I'm running one board 4x SE, where it's nice to have the headroom.
 
Last edited:
Thanks DPH. How do you determine higher performance from the spec sheets? From what little I understand I was initially just looking at lowest THD+N at lower power but then read in another thread that this doesnt necessarily mean it sounds good (something to do with feedback) so wasn't really sure to go from there.
 
Eeesh, that gets into a dangerous discussion about whether feedback sounds "worse" or "better". Which, IMO, becomes nonsense philosophical discussion quickly. But that's me. :)

I was going off distortion @power levels. The 3251 and 3255 should sound pretty similar and that we're really getting into specmanship. The 3251 is lower noise (makes sense since it's lower gain, too) and lower distortion in its power band.
 
I want to connect the Reset switch terminals to a switch on the front panel.

Also, I want to bring the Fault Leds to leds on the front panel.

What is the way to do that?

I assume you have the 3251 board. Take a look at the schematic (fig. 6) on p.14. On the bottom at the middle of the page, you will find the reset switch connections. The reset switch has 5 connections, 3 on one side and 2 on the other. When pin 5 is connect to pin 6 (a "dead" end), the amp in on (Normal) When pin 5 is connecting to pin 3 or 4 (ground), it is in reset mode - no sound. So, just connect pin 6 to either pin 3 or 4 via a toggle(on-off) switch while setting the reset switch on the board at normal. You need to solder wires from pin 6, and from pin 3 or 4 and connect the wires to the external switch, which presumably will be located on the amp chassis.
 
Hi DHP:
I think the feedback comment was about the amount of feedback required to achieve a given result rather than "feedback bad, no feedback good". In any case it wasn't specific enough comment for me to know whether it actually had a noticable affect on these amps, it just made me uncertain about relying solely on THD+N to make a judgement.

The one comment I have read that relates directly to the TPA3251 and 8 ohm is "Beside that, the 3255 is better used with 8R+ speakers, as output FETs RDSon is (way) higher than 3251" (by doctormord) which seemed to indicate perhaps the 3251 isn't the best for my speakers (or am I just reading it wrong)? Or does the higher performance in power range with better S/N outweigh this consideration? Perhaps I'm being a bit picky, but my experience with a bunch of TPA3116 amps has been that I find the high frequency hiss annoying in quiet passages of music (3m listening distance - and I do seem attuned to hearing high freq noise), so I am not keen to repeat the experience.
 
In all honesty, you're probably trying to split hairs. Ill be corrected if I'm wrong, but low rdson is a feature not a detraction as it affords lower losses, especially driving high current (low impedance speakers).

Advantage, albeit tiny, for the 3251 across the board, becoming greater with low impedance speakers.

Flip a coin between more power and marginally better specs in your power band. Both are more than powerful enough for your need. The 3251 is a bit quieter, but booth are I believe quieter than the tpa3118 and certainly higher performing.

A straight thd+n number isn't too helpful, but the plots themselves vs frequency are telling.
 
DPH - I agree its probably all quite marginal. Without a proper studio test setup is it even possible to hear an audible difference between the 3250 and 3255 at lower power? I have no idea how far the plots have to be apart before its possible to tell. The Rdson comment came up because its one of the few specific things I've seen on the 3251+8 ohm - had no idea myself what the real world implication was.

Speaking of splitting hairs, I notice that the 3250 has as a lower plot up to 40W. Am I correct in thinking the difference is due to it being tested at a lower temperature (25'C rather than 75'C) and so that if testing conditions were equal the 3251 would be better?

Thanks for your replies.
 
The only like-for-like plot would be figure 3 in each respective datasheet, which looks pretty much identical at 8 ohms (the only plot available on the 3250).

No advantage that I see for the 3250, and lower power. Same built in gain as 3251.

I'd decide between the 3251 and 3255 as far as which TI board to jump on. Both will treat you well, but in your case I'd go for the 3251.
 
The Meanwell units have been well regarded here, and I'm favorably impressed myself. But look at your major electronics distributors in EU/France to see who's making a 36 V, ~300 watt SMPS.

I'm a bit wary of the Alibaba's of the world for the power side of electronics, but that's just me.
 
As the input requirement for these boards is 2volts can anyone recomend a simple preamp with volume control that would be suitable.

I have looked at the various chinese preamp clones but the reviews are generally not good !!

I want something that will not impact the sound quality of the tpa3255 ev board but dont want to spend a fortune !!
 
Powered-up my TPA3255EVM for the first time today and there was a high-pitched noise coming from the speakers. I checked the power connections of my system and noticed that the amp was sharing the same power strip as the pc monitor, moved it to a different power strip and high-pitched noise was gone.

Do i like the sound of this amp? Absolutely! This amp made my diy gainclone sound like a "sissy" amp. It has more power, instruments in music have more "weight", I was worried about the high frequency harshness often associated with old class d amps but not on this one. I'm not missing my gainclone amp.

This was my first amp build and because of all the help here it was a pleasant experience for me. Thanks everyone.
 

Attachments

  • D99945CD-3580-4E1A-9C27-D7C4CC2162C7.jpeg
    D99945CD-3580-4E1A-9C27-D7C4CC2162C7.jpeg
    113 KB · Views: 404