Hi The early results are in from the Eev blog survey and 62 percent of you said you want to see random tear downs and also 62 said that you want to see reverse engineering. Well, the previous video was reverse engineering. so this one I thought I'd do a random teardown. I just grabbed a random bit of kit from the Eevblog lab here and today ta-da we have this Sennheiser True Diversity Receiver.

Not that dual diversity rubbish or no diversity rubbish because everyone knows that in 2021 you can't have no diversity because well, you'll get cancelled and stuff. Anyway, this is the Ew 100 G3. I think that's like Generation Three. I think they're up to at least G4 now and this is the Uh Desktop.

Uh, well, you can. Actually, I think you can even get a rack mount version of this. It's got dual antennas on it and which is better than the one that I use on my camera. which is uh, you've seen this, uh, before.

I've done a tear down of this before. It's the Sennheiser Ew A one. It's actually exactly the same part number, which is like really kind of confusing. Anyway, I guess you know that they uh, match and I've done a tear down of these.

This is the receiver unit that goes on top of my camera. I've done a tear down of the receiver and the Uh transmitter and these are a really good bit of kit. I really like them so I'll link the video up here and down below and at the end if you haven't seen that. Highly recommended.

So let's crack this puppy open and see what's inside. It's going to have lots of diversity, so for all you diversity fanboys or going to run wild anyway, takes about four watts maximum. Uh, we've got balanced output here. Xlr, Joby, and a Uh Trs Jack here for the unbalanced data and data.

I don't know that goes into some, so you know it's like a system type thing. I think the newer model has the Ethernetes and stuff and you do have to get the specific frequency range. By the way, if you get in, these uh, different countries have different, uh, legal requirements for spectrum use and stuff like that, so this one's here. This is for the Australian market, the 626 to 666 megahertz, the B2 range.

So let's crack this open. I don't expect there to be much inside. I suspect it might be fairly empty because it's You know, there's not much more in it. Um, compared to any more screws there.

No compared to the Uh version which sits on top of my camera. but the one that's on my camera is only a single antenna so it's node. It has no diversity whatsoever so it's going to get absolutely cancelled and it'll all of its social media accounts are going to get cancelled and poor old no diversity receiver on the camera. So this is a true diversity and I'll explain with Dave Cad probably in a minute.

So stick around. I'll explain the difference between no diversity, dual diversity, and uh uh, the true diversity. Which this bad boy is true diversity. So let's lift it.

Listen, oh hello, hello. it's just way. hey hey. that's rather nice.

Check. Check this out. and yeah, it's got nothing in it. Um, I I like this look.

look. they've got a little matching. um thing. it doesn't just lift off it, it goes down.

look. it goes down and then slides in like that and you can't lift that out. That's a really nice bit of design. Somebody was thinking there.

I really like that and it's got these little tabs in there like that that do that. That's excellent. Anyway, Um, yeah, that's probably less in there than I thought. Um, Interestingly, they do have different look.

They've got more standoffs here, so I don't know. Is there another model? they could it there? I think they do have like several different models or something. so maybe there's one that needs a bigger and that has a bigger board or something that goes right on the base there. But anyway.

um, it's all on the one Pcb here. Then we've been blobbed for our Lcd front panel here and it's got. what is that? Edcom Germany? Oh, by the way. Designed in Germany, Assembled in the United States of America? disassembled in Australia, not Austria.

And if anyone knows why it was not assembled in Germany, it's I don't know. Is there company politics going on there or something more tax advantages? I don't know if you have any clue. leave it in the comments Anyway, there's nothing on there. There's an Sl8 down there, whatever that's doing, and three blobs for the Um.

Lcd interface and that's all she wrote. But yeah, that's a completely, uh, custom design. Looks like they have a custom window in there too. So there you go.

They've gone to a lot of effort to engineer their own custom window there. and uh, lots of test points on the top side of the board there. So obviously they'd have an automated uh test jig that tests these. um, just standard tactile switches with, uh, big, nice big extended buttons on them.

But that's all she wrote. What's that puppy doing? You know that's just a boring Lm324? Um, so I don't know what's going on there. Why do you need a a 3, 2, 4 on there? Well, there's lots of Rf cans in there, so I think, uh, probably just the best way to do this is just to get the board out and uh, do a couple of screws here. Uh, the B and C's down there locking nuts on those and I'll whack it under the tagano shall we? All Right Here we go under the Tagano microscope and I've taken off the metal cans here and this actually, uh, reminds me it's I had to go back and check my previous video of the wireless uh, one teardown and it's I think it's near identical as you'd probably.

um, expect all the Um cans actually look identical. right down to, um, the shape, the pattern, that they've got this alien looking pattern that they've got on top of this can here. So there's no surprises whatsoever for finding that this is pretty much near identical in terms of just general receiver functionality to the Uh wireless version of this. They've just shrunk this down into that wireless receiver.

But because this is a true diversity receiver compared to the just regular diversity receiver or dual diversity receiver as it's called in the Uh wireless one, then um, yeah, there's gonna be some differences there. And sure enough, the differences are. it's got an extra receiver here. Here's the two antenna inputs here.

and we've got two receivers. So let me show you what the functionality is. We have Davecad. So what is a diversity receiver? Well, it basically the diversity name comes from the fact that you have more than one antenna.

you've actually got at least two antenna. I.e you've diversified your receiving antennas so that they can pick up potentially different signals between them because they're not physically in the same location, they're separated by a certain amount in in some sort of spatial array, or just physically separated like this. They do technically receive different signals. now.

if you're receiving the same signal but from a different location antenna, then you have options. If this one gets a bad signal for some reason, then you can continue to pick up from this antenna here. So you've diversified your options. it's more betterer.

Couldn't pass it up because I'm Australian, so we have to have a look at what's called the multi-path effect and this is what causes these, uh, drop out problems in a receiver. You've got little transmitter Dave here. you've got Dave's camera over here which only has a single antenna on it. Now of course the signal passes line of sight like this.

straight from antenna to antenna. Bob's your uncle, No worries, right? No trap for young players. this is where you can come and guts are. You've got uh, reflective Rf reflective surfaces like the ground and potentially the ceiling like in this office space I've got here.

Up in the ceiling is this is a multi-storey office complex. It's a concrete slab, but there's also a gigantic metal sheet right above and also below on the floor below me. If you've seen in my roof before in various videos gigantic metal sheet, they're just like separating the thing. I'm basically in this like faraday sandwich like this of metal like this.

but it's not just inside places like this, it's outside this. uh, the actual ground itself can act as a reflector. So yeah, you might not have anything above you on the sky, but the ground. And what the problem here is is that you get reflections of the signals off these uh, objects.

They can be all sorts of different Rf reflective objects and if two signals receive at the same time that 180 degrees phase apart, then they can cancel each other out and this can lead to dropouts. And that's why if you have a second antenna here, you might get a drop out in this physical location. but you know, 30 centimeters away. No worries, you can receive that signal.

No problems because you haven't entered this sort of like dead spot where the signal cancels out and drops out. And that's the multi-path effect. The multi-path problem. And that's what diversity having more than one antenna solves.

So please excuse the crew if the model didn't have time to build it, to scale or to paint it. This is a block diagram of a simple Rf receiver you've got. The antenna goes through a filtery thing, it goes into a like an Rf preamplifier, then goes into a mixer which is then mixed with the local oscillator and then you can down convert this and amplified and at the end you get your audio frequency out. Okay, no worries.

what does a dual diversity receiver look like? Or just a diversity receiver? And this is how the Wireless Sennheiser one will work. I was actually wrong at the start. I forgot that this receiver watch the tear down video is actually a a diversity receiver. A dual diversity.

It's only got one antenna, so where's the other antenna? Hmm, that's the tricky part. You'll have to watch the tear down video. I've linked it in up here somewhere. Go check it out! So what happens in a diversity or dual diversity receiver is that there's two antennas like this and they basically go into an Rf switch like this which is controlled by the microprocessor in the thing and it goes into the same exactly the same Rf system.

the bandpass filter, the Uh amplifier, and the mixer which the local oscillator it down converts and you get your audio frequency out or whatever. However, the Uh Rf system works right. Typical block diagram. The problem with this is that the processor actually at some point in this path.

Here it's got to measure the signal level. Am I getting a good signal? You know what is my signal level output. Is it any good? Oh, I'll switch to if it's starting, looks like it's starting to drop out. Oh, I'll switch over to the antenna.

Is that any good? and there's various algorithms you can do. Do you uh, switch to the last one that hadn't last known good signal or do you like alternate between them or whatever. There is, however, going to be some time delay when you actually switch between these and can actually measure them. So a dual diversity is it's good.

but it's not as good as a true diversity receiver, which is. what we're looking at here today, and I have another Dave Cad for that. So here it is: the True Diversity receiver, once again, exactly the same thing. It has two antennas like this, but it actually has two complete receiver systems.

It's got two complete filtering systems. It's got two amplifiers like this. It's got two mixers like this single local oscillator to drive, uh, both. of course.

And then this switching happens. It's somewhere on the output here like this. and this way, the processor can actually measure at the same time, can measure the signal from both of these. It doesn't has to what, it doesn't have to wait for it to switch, over, settle, and then measure, and whatever.

so it can basically sample at the same time in real time. and then it can choose, like, practically instantaneously, the best signal from whichever antenna you've got. And of course, you can do this with more than one antenna, but two. There's all sorts of mathematics behind this, of course.

and uh, you know theory. and and you can spit a number out how much better having two antennas? What? you what your odds are. Because it's basically a randomized type thing. You don't know.

unless you're in a completely controlled environment, you don't know where that drop out is going to happen, right? It can happen basically anywhere. So it's basically comes down to statistics, your odds of having to drop out, and which system is better. But anyway, a true diversity system is going to be better because there's no delay and you can sample at the same time. So yeah, this is more better.

But the obvious problem is is this costs more. You've got two Rf amplifier systems, got two mixers, and everything else, and that's what we see in here. We've actually got Ta-da two complete amplifiers there. they are, so let's zoom in on one of them here.

So we're going to have a controlled impedance trace coming out of here. There's going to be a ground plane on the inner layer under there. comes in here. We've got some filtering action happening here.

There you go. I'll leave it for those that are playing along at home to reverse engineer that little filter. There There you go. We've got inductor inductor, inductor, inductor, inductor, inductor, capacitors, capacitors, capacitors.

Oh, we've got some oh look, little diodes there. lots of ground stitching along there for low Rf impedance. but anyway, it comes out of there and it buggers off into the can here. So the reason that the Via drops under and goes under here is because you don't want it running under the can like this, because the metal can, if it's got a little sharp bit on it from the manufacturing, whenever it could actually cut through the solder mask on the Pcb and contact the trace.

So yeah, that could ruin the day. So that's probably why they drop dropping under there. But there you go. That's our receiver and I had to.

I could not find any info on this at all so I had to ask the Twitter. So thank you very much Andrew. Uh, Summer Vaughn? Silentz? maybe? or Samazon? thank you very much. Ah, who pointed out so that symbol turns out to be from Tri-quint uh, Semiconductor, which is now um, Corvo? I? I don't know.

Never heard of, um, either of them. Don't Anything I've heard of Triquin, but that symbol is definitely on top of the Uh chip and the 213. Cmy, it's the only one, so it's a down converter which is really interesting which contains a mixer in it. which is kind of strange because as you'll see, we've already got a mixer further down in the process here.

but it's got to be because it is this package which is a Sct-598 for those playing along at home. There you go which has the big ground pin on here. The reason that ground pins bigger is not for power reasons. It would be for inductive reasons for a low impedance ground path.

That's why it has a big thick pin on it. Oh, look at that. look at that thing of beauty Joy forever. Fantastic.

Anyway, yeah, so that's the reason that it's got that. and uh yeah, it's it. Must be using the mixer because it's got stuff up. And pin one here.

it is There you go. It's doing some mixing goodness. so there you go. It does actually have an inductor and a cap in there between the mixer in, so it's all being used.

So anyway, I'm not going to reverse engineer the whole Rf section of this thing. Uh, they, you know those playing along at home can do that if you so desire knock yourself out. But anyway, the interesting thing is that it is using that mixer and that Rf amp as well. But as I said, we've got two of those.

They are absolutely identical. Check them out, as you'd expect, absolutely identical everything. The filters, um, outside is exactly the same. and if we flip over to the bottom side here, you can see that there is.

There's a saw filter. That would be I won't look up, I won't try, and uh, get that part. But anyway, that would be a uh, I'm sure that is a sore surface. Acoustic wave filter.

It's in a ceramic package. You often get them in the ceramic packages like that. and oh, is that some other filter packages? I don't know what they are basically. Yeah, there are two identical ones here now.

Obviously, this is sort of like the main channel and this is the secondary channel here. and they've got them labeled one and two. Funny that, so there's some extra goodness on the bottom. But you can see it's got two absolutely identical receiver systems and and filter systems.

And that's what we're and mixers. that then that's what we've got here. So there you go. It's it's all there.

It is. true diversity. And of course, just be careful because everyone knows that in 2021, if you focus too much on diversity that's your only focus, then well, you're gonna go broke. And thanks to Twitter, I now know that this actual chip has a name.

It's Gary, it's Gaza good on you, Gaza and Gaza's actually got a Twitter profile. Check it out. And there's just a basic application block diagram and I think pretty much we're seeing near identical uh to that on this layout here. Anyway, let's have a look if we go in here.

Here's your main oscillator 230 Meg. There it is. and you can see that's pairing this 4127 chip here. Exactly.

I believe this is all exactly the same sort of stuff that's used in the on-camera wireless receiver as well. So anyway, you can see that obviously this has to power both of these channels. so there's another one over here. There's an identical 4127 chip and you can see these ground here.

This is a dead giveaway that there's a controlled impedance trace running through there. And of course it's going to be the oscillator because the oscillator and the local oscillator has to bugger off to both of these chips here. Just as we saw in our block diagram, our local oscillator goes into the two mixers. So the 41 27, let's go to the video tape.

I believe this is a uh, Bh 4126. uh, if detector for 900 meg speech spread spectrum cordless phones. Looks like it's bang on the money. Um, so this thing.

Of course. once again, this has. well, it's got a local oscillator in it. Or you can probably feed in an external oscillator like we've got here.

And uh, then it's got a mixer as well. And there's a uh, once in and need a filter out here as well. and there's going to be a lot of stuff on the bottom there. That's probably what those filter blocks in there are doing.

Those filter blocks? There would be part of the 4127 filtering around. that chip would be my guess. So there's a typical uh application circuit for that. and if we map that down to the Pcb yeah, you know it's going to be doing something similar.

And they definitely are using the internal mixer because that's Pin 16. So that's buggering off there somewhere, which does something. So yeah, um. so they've got a couple of mixers in this bad boy.

So anyway, there our jewel mixes in there with our local oscillator and it's the same oscillator for both from exactly as per our predicted block diagram. We've got another block up here. that's just. is that just entirely.

Well, it's not entirely passive. There's some other sot 23 jobbies in there. Once again, I'm not going to reverse engineer this and that has actually nothing on the bottom there. And this, uh, previous block here is I didn't near identical to this block down here.

So yeah, they're just reusing the design. As you'd expect, there's no difference. And there it is exactly the same between the 4127 with the local oscillator in there and this block here. Whatever, this one's doing, uh, in the previous one, it's got basically a duplicate over here.

So yeah, once again, not going to reverse engineer this whole thing to get a schematic. Geez, that would be a job and a half wouldn't it? But anyway, nice modular design, lots of cans, uh and oh, by the way, this download down here that there's a diode there, an inductor going into what will be the center tap of this. so going into here, so that must the only thing that's for and you'll notice this. It's buggering off under here and if we follow the money, follow the money.

pops up here and exactly the same thing happening over here. The only reason you would feed something into here via an inductor, it's not having the antenna out. This is for feeding power in to the antenna. Um, so yeah.

um, it must be for like, a remote, uh, Rf amplifier. You know if you want to mount your amplifier somewhere else like a Masthead amplifier like you'd have might have on your Uh Tv at home or something like that, then um, yeah, that's what it must be doing. So I'm sure it has that feature. I didn't know, but obviously it's in the hardware.

That's the only reason for that hardware to exist there. And then over in the processory section, we've got a oh, an 062 Japan Radio Call. This is more more analogy stuff here. A couple of Japan Radio Corps uh, they're an 062 Fete amp are they? And there's our little Uh Watch Crystal 32.768 Kilohertz four megahertz oscillator for our processor in here, which is an Nxp Joby and I believe that's exactly the same one that was used in the on camera receiver as well.

that's in its own little metal can. You don't want the electrons falling out? No wackers. and they've like series terminated Like everything in here like every line on here has is terminated. Look at that.

Wow. And then you've just got some regulation and other uh, jelly bean stuff around here. This goes off to of course, the connector. off to the Lcd front panel.

Good old 7805. There you go. No workers, some more regulation around there. That's all your power stuff and the rest of it is just.

this is just your audio stuff. Um, yeah, the power in here for your Dc power jack that's fused and it's got some protection by the look of it. and uh, deity protection. And then you've got all your analogy goodness.

is that discreet? That's a discrete amplifier That's a discrete transistor amplifier. I think. Is there anything? Note: There's nothing on the bottom. Yeah.

So I think the balanced amp and unbalanced amp. There are discrete transistor amplifiers. Nice. Oh, and the previous one had a compander which is well, which compresses the audio and you've got a matching one down there.

Five, Seven Five. No, it's not a Seven four, Hc, Five Seven Five. It's actually a Five Seven five compander uh chip which squishes the audio levels and then uh Re expands them at the other end. There, it is cool audio.

I think that there's many companies that make this, but Cool audio. I I want to use something from Cool Audio because they're just cool. Oh, look at that wireless microphones for the application. Go figure.

Now this down here. This is interesting. Check this out. It's upside down so all the electrons are going to fall out.

Let me flip that around and range and version. Now these are these are resistors here which allows the you would think allows the processor inside to know what version of the Pcb is being used and what range it is. I assume at range means um you know the different models for around the world like B Range or whatever here for Australia and you can see one side of these resistors is grounded and the other side is uh going off to A Via here you might think this goes off to the processor, but hmm. let's flip it over.

You'll see that it unless it goes off in an inner layer, which I don't think it does, it goes off to a test pad on the bottom and that's it. That is. so. and there's a corresponding ground, uh, test point there as well.

This is so the better. And there's all sorts of tests. There's all sorts of test points all over this board. Check them out so there's obviously at the production stage.

Yeah, all the silver bits on there. they're all test points. So they all go to Pogo pins. So at the on the production test line this used to be my day job is designing a bit of nail stuff.

This board will plug in here. it'll line up with like the holes in this thing. uh yep. you know you can use these as alignment holes.

We've got holes over here and the mounting holes as well. You put those down, all goes under the Better Nails tester and this can. This will hooked up to all sorts of Rf test gear and stuff like this which will completely automate test this board and it can measure it, knows which range it is. So then this test automated test software knows which frequency range to test for because you have program because it's populated with it, just reads those resistor values.

It knows. Oh yeah, I've got a an Australian B Series model. I'm going to test it for all over the B series. uh, frequency range and stuff like that.

So it can test that. and and then the version number. It knows what version number of the board it's got. and Bob's your uncle? Uh, does it program? Uh, Well, yeah, there's a header.

There's that. I assume that's a little Jtag programming header down there. Do they program it? Yeah, yeah. I think that would be a program.

They probably program the processor on the board as well. No problems. So yeah, there's no reason for the micro on board to, you know, know or care about this sort of stuff. But the production test jig and production test hardware and software.

It really needs to know what version of the board it is so I can select the appropriate test. So there you go. Isn't that cool? There's not much else on there. Oh, and we just missed it on the bottom here.

4580 audio Op-amp Of course. there's a 45-80 in here. and that's um, the audio frequency output. Like the actual audio output of the Rf.

So that's the final audio output. There you go. There's another unpopulated footprint there. Don't know what the business is there.

Is that an alternative footprint regulator? And they're you. Because this is a regulator. Obviously, Maybe that's an alternative? I do. Yeah, I don't know what's going on there.

Oh, and I forgot. This of course has a digital uh, you know, allows you to select digitally select the frequency. so it's got to have a Dds in there, a direct digital synthesis uh, generator. And sure enough, there it is the Adf Four Triple One Seven that allows uh, the software on here to generate the firmware to generate a specific frequency, Rf frequency, that or channel that you're transmitting on because you can actually dial in the frequency and you can scan as it's got scan modes that you can scan for a signal and then automatically lock it in and stuff like that.

and uh, you know, automatically identify the receiver and pair them and stuff like that. So yeah, there's our Dds generator chip, so there you go. So that's really rather cool. I like that that is the Uh Ew 100 desktop version.

I guess because the the model numbers the same might be some subtle difference. I don't know. Sennheiser is a bit weird when they come to like naming stuff. It's very strange.

Anyway, Um, yeah, that's a that's a well-designed bit of kit. I like that. So there you go. I hope you enjoyed that video.

If you did, please give it a big thumbs up. As always, discuss down below: catch you next time you.