"Micro Bamboo Project" : 3E Audio 260-2-29A Stereo amplifier + Micro-Audio PSU

[PlasticDoc]

I have just found random posts here.

Now if you don't believe them it's difficult to convince you afterwards.

Advertisements based on selective snippets of subjective client reviews should be posted in the appropriate place, which, if I am not mistaken, is either the vendor's website or the "Desperate Dealers Forum" thread on this forum.

 

[BDWoody]

Now if you don't believe them it's difficult to convince you afterwards.

How about something other than anecdotal claims. It's definitely going to be hard to convince anyone of anything if it is just based on stories.

 

[jwdevos]

This thread has inspired my to give the 3E Audio board a try too. I ordered two boards, and two PSU's from Micro Audio. I noticed the post about good results with a cheaper PSU, which is obviously interesting in this price range, but I went for the Micro Audio option mainly because of the build quality. Whether there's a notable impact on the sound of the amp or not, I trust the better build quality to last a while longer.

I went for 46V versions, slightly under the max rating of the 3E boards.

Can anybody comment about the built-in speaker protection of the 260-2-29A? There's supposed to be speaker protection, but I find it tough to determine if it's adequate for all failure scenario's and I don't want to blow up someones expensive speakers trying to impress them with a cheap amp. I'm considering adding a couple of Guardian-86 boards by Neurochrome just to be sure, but that means a pretty big part of the total budget on such a cheap amp.

 

[3eaudio]

@jwdevos no need extra speaker protection as TPA3255 include these features.

 

[Roland68]

@jwdevos no need extra speaker protection as TPA3255 include these features.

I wouldn't rely on that, at least not with expensive speakers.
The protection is only integrated in the chip. I've already lost expensive speaker chassis to DC twice in my life, once even large and resilient woofers because an amplifier broke. If things go really badly, the power supplies deliver 36-48 volts DC at several amps.

@jwdevos
In the diyaudio forum I've seen several projects on SSR protection circuits, I particularly liked the one by xrk971.
Personally, I would only go to that trouble with expensive chassis. These amplifier ICs are really good and it happens much less than with normal amplifiers.

 

[somebodyelse]

It would be good to have some clear documentation of the failure modes that the protection covers, and the modes it doesn't. This isn't specific to 3E - many other manufacturers miss it too. This would let people make a more informed decision about whether to add extra protection for their speakers.

From my understanding of the TPA3255 datasheet section 9.4.1 most of the built in protection is to protect the amp from various conditions that may damage it. Only the 'DC Speaker Protection' (section 9.4.1.3) is to protect the speaker, and even that seems to be limited in what protection it offers. Nominally it is there in case one speaker terminal is accidentally connected to ground when the amp is in a bridged mode, which would lead to DC on the speaker. This is detected by an imbalance in current in the bridged channels, not by detecting DC at the output terminals, so doesn't protect against other sources of DC offset. It also doesn't protect against an output transistor failing short, although that _might_ at least trigger fault indication due to current mismatch - @3eaudio can you confirm or deny this? The fault signal could be used to disconnect or power down the power supply if this happens.

 

[jwdevos]

Thanks everyone for helping me understand speaker protection in relation to this particular circuit a little bit better. I think I'd rather add 200 bucks to each build, grab a pair of Guardian-86's (https://neurochrome.com/products/guardian-86) and sleep much better. My DIY amps might end up at friends places over time and preventing speaker damage and pops is the must crucial safety factor for me with these DIY projects, besides personal safety of course.

 

[hi30u]

Thanks everyone for helping me understand speaker protection in relation to this particular circuit a little bit better. I think I'd rather add 200 bucks to each build, grab a pair of Guardian-86's (https://neurochrome.com/products/guardian-86) and sleep much better. My DIY amps might end up at friends places over time and preventing speaker damage and pops is the must crucial safety factor for me with these DIY projects, besides personal safety of course.

This is on the Amp to Speaker path, correct?
Can someone test or measure and confirm this claim about the Guardian 86:

- No relays! All switching is done with MOSFETs for the lowest distortion.
- No relay contacts to wear, thus, no change in performance due to aging.
- Adds no measurable distortion.
- Floating photovoltaic MOSFET driver ensures consistent good performance throughout the full swing of the output signal.

 

[somebodyelse]

Neurochrome's amps have performed as claimed when tested here, so I would trust the performance graph that backs up the distortion claim.

 

[jwdevos]

This is on the Amp to Speaker path, correct?
Can someone test or measure and confirm this claim about the Guardian 86:

- No relays! All switching is done with MOSFETs for the lowest distortion.
- No relay contacts to wear, thus, no change in performance due to aging.
- Adds no measurable distortion.
- Floating photovoltaic MOSFET driver ensures consistent good performance throughout the full swing of the output signal.

That's right, the speaker protection takes place between the output of the 3e Audio PCB and the Speakon connectors I'll be using. I was worried about "placing something extra in the signal path" but the same pair of protection modules in my Modulus-86 amp don't seem to get in the way.

Regarding the two claims about the relays: speaker protection is often done using relays. All relays are prone to contact wear because of the way they are physically implemented.
I have no knowledge about distortion with relays versus MOSFETs, but Neurochrome provides distortion measurement results on the product page (on the tab labeled "Performance Graphs"). The bit about "no measurable distortion" is because the gear used to measure this (by Audio Precision, similar to the equipment that gets used a lot in reviews on this forum) isn't any more accurate than the speaker protection itself.

I wouldn't know how to verify the last claim, but Tom, the force behind Neurochrome, is always glad to help and answer questions. He probably wouldn't make any claims that he can't support. You can contact him through his website if you want to learn more about his products.

 

[hi30u]

The fault signal could be used to disconnect or power down the power supply if this happens.

Agreed, 3E (or other brand) Amps should implement the same monitoring as in the Guardian 86 = at each speaker's output.
And then, in case of any potential problem, do two things:
- disconnect the speakers "at once" (relay or MOSFET)
- power down the Amp (and PSU if feasible).

 

[EfrenSanani]

Greetings from Spain friends, I wanted to ask you what modifications I should make on the board to use the SE mode input, the documentation of 3e audio is not clear to me what to change on the PCB, should I buy operational for U1 and U2, if you could attach an image I would greatly appreciate it.

 

[activewire]

Greetings from Spain friends, I wanted to ask you what modifications I should make on the board to use the SE mode input, the documentation of 3e audio is not clear to me what to change on the PCB, should I buy operational for U1 and U2, if you could attach an image I would greatly appreciate it.

Yes: you will need OpAmps for U1 and U2 also relocate the 0 ohm resistor (meaning it acts as a jumper) see my pics here
Post in thread '9 Channel 3E Audio Amp(s) project'
https://audiosciencereview.com/foru...nel-3e-audio-amp-s-project.53855/post-1983201

 

[EfrenSanani]

Yes: you will need OpAmps for U1 and U2 also relocate the 0 ohm resistor (meaning it acts as a jumper) see my pics here
Post in thread '9 Channel 3E Audio Amp(s) project'
https://audiosciencereview.com/foru...nel-3e-audio-amp-s-project.53855/post-1983201

Wow, very well documented, thank you very much for your help and have a great day.

 

[DaveFred]

Exactly this my experience with Micro Audio PSU as well. In two words, fuller and beefier maintaining all other sound charateristics

much better bass control, especially the lowest frequencies, better presence of sound, sound is more tangible and still crystal-clear. I love this amp!
With MP-H250S48 power supply the sound was also good, but kind of shy and not so pronounced.

These sort of claims make me mad (<-edit:language stronger than meant to be) irk me.

Such an obvious improvement should be easy to measure and display, yet, never is.

 

[Roland68]

These sort of claims make me mad.

Such an obvious improvement should be easy to measure and display, yet, never is.

There is no reason why something like this should make you mad. Everyone has the right to express their opinions and experiences, just like you.

I can confirm for myself that there can be audible differences in power supplies and analog circuits, the emphasis is on can, but we are not talking about worlds here and it is more like the difference between a usable violin for a few thousand € and a significantly more expensive violin like the one played by well-known soloists.

But and this is the crux of the matter, people perceive such differences very differently, ranging from unimportant/inaudible to absolutely crucial.
I can hear such differences in certain music, and it is important for me there too, but, as I said, they are more nuances than major differences.

 

[DaveFred]

Since the Pin 1 is grounded from the 3E Module, I would follow the old pratice. Just my opinion )

Just solder the three wires from the 3e JST connector,

3e JST pin 1 In + to XLR Pin 2
3e JST pin 2 In - to XLR Pin 3
3e JST pin 3 AGND to XLR Pin 1

To the XLR connector,

That's it.

And don't worry about alternate wiring suggestions about shield to chassis or XLR casing to ground

^Is a question, not a statement, just looking for clarification.

 

[fluid]

Just solder the three wires from the 3e JST connector,

3e JST pin 1 In + to XLR Pin 2
3e JST pin 2 In - to XLR Pin 3
3e JST pin 3 AGND to XLR Pin 1

To the XLR connector,

That's it.

And don't worry about alternate wiring suggestions about shield to chassis or XLR casing to ground

^Is a question, not a statement, just looking for clarification.

http://www.troelsgravesen.dk/FUSION-BI-AMP/AN_Legacy_pin_1_problems.pdf

"Pin 1 is not an audio connection. Pin 1 is for shielding."

 

[DaveFred]

http://www.troelsgravesen.dk/FUSION-BI-AMP/AN_Legacy_pin_1_problems.pdf

"Pin 1 is not an audio connection. Pin 1 is for shielding."

I read that, but I also looked at the pic of the sample unit @3eaudio sent Amir,

Conflicting answers...

 

[fluid]

Conflicting answers...

I don't think so. There is one right way to do it, there is a standard, AES48
https://www.aes.org/publications/standards/search.cfm?docID=44

Some good explanation from Bruno Putzeys on the why in the wiring section
https://www.edn.com/the-g-word-how-to-get-your-audio-off-the-ground-part-3/

The cable shown in the picture is an off the shelf pre made JST that has been used for convenience and low price.
The fact that it measures nicely shows that in this scenario it does not have any great effect by wiring it in a sub optimal fashion.
This can change if multiple amplifiers or other components are used. Induced hum and buzz is a real deteriment to audio performance.

With a standard twisted pair and shield microphone cable used for input it can be wired where the shield actually stands a chance of shielding the signal. Avoiding the extra 15 minutes and cost (if you don't already have an offcut of mic cable) to do it properly seems like false ecomony to me.