Hi guys
just finished two board on 3255
pffb
one with 450khz and pffb nominal s from national datasheet works fine
the second one 600khz
the only difference is 600khz board didn't start with pffb
pffb on the boards differs only c_fb_out on 600khz board is 1nf instead of 220pf
both board planed to be used with 51v so R_fb_gnd 10k
where im wrong? do i nedd just use 220pf c_fb_out on 600khz board?
just finished two board on 3255
pffb
one with 450khz and pffb nominal s from national datasheet works fine
the second one 600khz
the only difference is 600khz board didn't start with pffb
pffb on the boards differs only c_fb_out on 600khz board is 1nf instead of 220pf
both board planed to be used with 51v so R_fb_gnd 10k
where im wrong? do i nedd just use 220pf c_fb_out on 600khz board?
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Finally someone that confirms what I am hearing.
Do you use transformers for coupling?
Well my DAC has a transformer output stage.
My listening impression now is that the sound is nice, but not perfect - it's a little "dry". This may be a characteristic of my transformer output stage - some other owners of the same DAC have found it unsuitable for direct connection to a power amp - they say it needs a buffer or linestage before the power amp.
But I suspect that if you have a DAC with differential opamp output stage there's a fair chance that the opamp input stage of a TPA325x amp is best bypassed - that's one less opamp in the signal chain. I'm currently trying to convince member daniboun to try this out -
https://www.diyaudio.com/forums/class-d/276982-tpa3251d2-145.html#post6186207
Maybe you can give him your opinion, and listening impressions, in that forum thread?
My listening impression now is that the sound is nice, but not perfect - it's a little "dry". This may be a characteristic of my transformer output stage - some other owners of the same DAC have found it unsuitable for direct connection to a power amp - they say it needs a buffer or linestage before the power amp.
But I suspect that if you have a DAC with differential opamp output stage there's a fair chance that the opamp input stage of a TPA325x amp is best bypassed - that's one less opamp in the signal chain. I'm currently trying to convince member daniboun to try this out -
https://www.diyaudio.com/forums/class-d/276982-tpa3251d2-145.html#post6186207
Maybe you can give him your opinion, and listening impressions, in that forum thread?
Hi everyone, I thought I'd share my variant of TPA3255 front stage. I used THS4531 fully differential amplifier, running on 5V - plenty for my power needs and doesn't need dual supplies.
Objectively speaking it has much lower noise than the stock TL072 opamps. No means to measure THD. Other than that - they sound alright
Objectively speaking it has much lower noise than the stock TL072 opamps. No means to measure THD. Other than that - they sound alright
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Could you post a picture of where you connected the inputs on the 3e board? Did you cut the power or outputs from the on-board op-amps?
I'm presently away from home for at least one week, so cannot take a photo.
To disable the opamps I simply cut the leg of the power supply pin of each one - pin 8.
The 4x small capacitors nearest to the heatsink are the blocking caps. I removed these and soldered my input wires to the now-exposed pads where the negative side of the caps were ... but be careful, I completely broke off one copper pad altogether, which made it extremely difficult to then expose more of the correct copper trace.
Of course this method means you have no blocking caps - not a problem for me, my DAC has no DC offset - but you might need to add outboard blocking caps.
To disable the opamps I simply cut the leg of the power supply pin of each one - pin 8.
The 4x small capacitors nearest to the heatsink are the blocking caps. I removed these and soldered my input wires to the now-exposed pads where the negative side of the caps were ... but be careful, I completely broke off one copper pad altogether, which made it extremely difficult to then expose more of the correct copper trace.
Of course this method means you have no blocking caps - not a problem for me, my DAC has no DC offset - but you might need to add outboard blocking caps.
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Umm -- aren't the substrate parasitic diodes going to conduct and still try to power (minimally) the IC? At the least loading down / clipping whatever I/O's still have signal excursions above pin 4? Metal gate CMOS, at least, used to be famous for *operating* un-powered -- all you needed was one input being driven by a somewhat lower impedance!!
My favorite trick is an 0,020/0,5mm jeweler's screwdriver between 2 SO legs that have already been bled dry with SoderWik (how do they spell that?). Then a small twist of the shaft at just the right temperature (as the iron heats it up), will pop loose whichever leg is in contact with the screwdriver blade edge farthest from the IC body.
It takes a little practice, but it's a breeze once you get the hang of it!
Cheers
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Hi, any chance you can share a bit more details?
sound interesting, I would like to try and build it as I am looking for a nice Class D Kits to build to my Modula MT XE pait that I built a few years ago
Thanks!
alonper: see the pics on post #877. It’s not like one is really ‘building’ the amp and PS but rather just connecting them together in the chassis of your choice.
Was that enough info?
Pete
Thanks for reply, i cant find pics on post #877..strange.
Anyhow, regarding 3eaudio and TPA3255, i wanted to order this and the PS but it seems that the PS is not available... So I am wondering if its recomended to order the 3eaudio TPA3250 All in One? Or you have any other idea? I can order the 3255 board but the PS is not available anymore... Any idea for replacement?
Thanks
Hi Alonper: I’ll repost the pictures. Hopefully you can see them this time. As far as the PS goes, he (3e-audio) stopped posting that unit on his website but he was selling them on eBay. I don’t know whether he still does. Here’s a link to the original unit’s posting ...hopefully you can message him and see if he still has any left.
TV Boards, Parts & Components for sale | In Stock | eBay
You don’t necessarily have to use 3e-audio’s PS. You can probably find others with the same power characteristics.
Regards, Pete
TV Boards, Parts & Components for sale | In Stock | eBay
You don’t necessarily have to use 3e-audio’s PS. You can probably find others with the same power characteristics.
Regards, Pete
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Thanks Pete!
Yes, I've checked with them (3e audio) and the PS is sold-out..
And I the TPA3255 is not available in their stores (both Ebay and Aliexpress).
I need to drive 2-Way Module MT XE (I think they are 4 ohm) I guess that 140W is enough, so I will order the TPA3251 which is their only board available now
I will also order the caps you mentioned in your post. (Panasonic FC grade 1500uF 50V caps).
Regarding the PS, any recommendations?
btw...my source is SMSL M6 or just my laptop (Lenovo T470p), no pre-amp - how will it be to connect them directly to the TPA325x?
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alonper: your DAC has analog out so I would use that as your your direct source into the amp. Your laptop can be a source into the DAC via USB. Don’t use the laptop’s internal sound card as it’s probably not audiophile quality (unless you’re using an external sound card of some sort).
As far as a PS goes, it depends on what you feel like doing or what you’re capable of. The 3e-audio PS was a self-contained unit ..it had the transformer built in so you just plug in the AC mains current on one side and it outputs DC on the other that you bring directly into the amp. There are several on the market and I’m sure AliExpress sells units like that.
You can try a Meanwell switching power supply that can output the DC voltage range you need but you’d need one that has enough amps to power your amp.
If you’re handy with a soldering iron and wiring up a toroidal (or similar) transformer you have a wide range of regulated or unregulated PS board kits you can buy & assemble (you only need a single rail type since you only need DC "+" & ground/return line ). You can then choose to modify the kits by changing out to better audio-grade capacitors or higher uF types.
Or, similarly to the kits, you can just buy a PS board and populate it with components of your choosing right from the start (but you’d still need a separate transformer to power the PS board).
What’s your thoughts?
Regards,
Pete
As far as a PS goes, it depends on what you feel like doing or what you’re capable of. The 3e-audio PS was a self-contained unit ..it had the transformer built in so you just plug in the AC mains current on one side and it outputs DC on the other that you bring directly into the amp. There are several on the market and I’m sure AliExpress sells units like that.
You can try a Meanwell switching power supply that can output the DC voltage range you need but you’d need one that has enough amps to power your amp.
If you’re handy with a soldering iron and wiring up a toroidal (or similar) transformer you have a wide range of regulated or unregulated PS board kits you can buy & assemble (you only need a single rail type since you only need DC "+" & ground/return line ). You can then choose to modify the kits by changing out to better audio-grade capacitors or higher uF types.
Or, similarly to the kits, you can just buy a PS board and populate it with components of your choosing right from the start (but you’d still need a separate transformer to power the PS board).
What’s your thoughts?
Regards,
Pete
Meanwell is a reputable brand, and the LRS-350-36 is a popular/affordable choice for TPA3251. But I think one step better are the resonant SMPS units from Connex Electronic, which are built to similarly high levels as the 3e-audio products.
The SMPS300RS is enough power for low-to-moderately-loud listening levels -
SMPS300RS | Connex Electronic
But if you intend to push your amp to the upper limit of its power levels, consider the SMPS600RS -
SMPS600RS | Connex Electronic
In either case, order the 36V version.
Connect from your M6's RCA outputs to the TPA3251 single-ended inputs, but then you would need to use software volume control on your laptop.
Better to wire a 10k or 20k potentiometer at the inputs of the TPA3251 for volume control, then configure your laptop for fixed-gain output, preferabley "bit-perfect" - you will need to Google this.