Lindemann Limetree Bridge network bridge with sample rate converter

A good network bridge will improve the sound quality compared to connecting a computer directly to the DAC. This one also does Roon RAAT, upsampling and downsampling and even converts DSD to PCM. Lindemann, translated to English, gives Lime tree man, which probably explains why Lindemann uses Limetree as name for a series of products, the Bridge being one of them. I presume Lindemann developed it to enable streaming for products that were introduced before streaming took a flight. For anything you throw at it will be converted to either 96 or 192 kHz PCM.

00:47 - There is no transparent mode and although some might not like that, many will. For it solves the problem of having a DAC that does not do very high sampling rates, up and down sampling or DSD. The important question then is, how well does it sound. But let’s first see how to use the Limetree Bridge. The digital output of the Bridge is to be connected to a digital input on your stereo. Both SPDIF and TOSlink are available, there is no USB Audio Class 2 output. On the input side it has to be connected to your router over either Wifi or a network cable. You now can play music from streaming services like Tidal, Qobuz, HighResAudio and Deezer. Spotify is announced but not yet implemented. You can also play internet radio stations next to listening to podcasts, which is quite unique for a network bridge.

If you want to play 01:52 - music that is stored on your computer or NAS, you will need a DLNA or UPnP AV server program installed on that computer or NAS. A good - and free - one for audio is MinimServer. Remarkable is that you can connect a USB CD-drive to the Limetree Bridge and play CD’s from it, which is great. If you don’t have a normal CD-player, you just buy such a drive for € 45. The Limetree Bridge is fully controlled from an app on a smartphone or tablet. Free apps are available for Android, iOS and iPadOS.

Roon RAAT is also supported so if you have 02:32 - the Roon Server program installed on a computer, you can use the Limetree Bridge as endpoint - the name Roon gives to network bridges and renderers. Like all products in the Limetree series, the Bridge is housed in a small aluminium box that uses a wall wart switch mode 5 volts DC, 3 amps power supply. The top of the housing shows a lime tree leaf. The bridge measures 107 by 107 by 40 mm and weighs 300 grams. On the front, left, we see the power switch that doubles as a mode switch - on which later more.

To the right the power LED, a LED that indicates the sampling rate of the incoming 03:18 - signal by colour and a LED that indicates whether the outgoing digital signal is 88.⁴⁄₉₆ kHz or 176.⁸⁄₁₉₂ kHz. On the rear we see the 5 volts DC input, the LAN ethernet socket, the Wifi antenna, a USB A connector for storage media or the cd- drive, the Wifi Protected Setup button, the TOSlink digital output and the SPDIF digital output. After opening the box a blue circuit board attracts the attention. It is the Stream810 streaming module by StreamUnlimited. This company was founded by ex- Philips people 15 years ago in Vienna and offers universal streaming solutions.

Like products of competitor Linkplay 04:13 - you find their products often in serious audio products. It’s like using a DAC chip in stead of building a DAC with discrete components. The output of the streaming module is in I²S format, having the data and clock signals over separate lines. After lifting the Stream810 module we see the works by Lindemann. The DC input voltage is filtered and stabilised here - and at several places on the board. The system is controlled using a Motorola micro controller. The I²S output of the Stream810 is connected to the base board over a multi-pin connector. From there it is sent to the AKM sample rate converter that converts the incoming PCM and DSD signals to either 88.4 and 96 kHz or 176.8 and 192 kHz, so two or four times oversampling for 44.1 and 48. kHz. Whether the output stream is twice or four times base band is set by holding the power switch upwards for 3 seconds.

From the sample rate converter 05:23 - the signal goes to the Burr Brown digital audio transmitter that generates the two’s complement SPDIF signal. That is sent to the output transformer that provides galvanic separation for the SPDIF output. The TOSlink uses the same signal to convert to modulated light used for optical transport. On the Bridge itself there is not much to set or control. As mentioned you can switch the output sampling frequency to either two or four times the base frequency and that’s it. All further control is done using the free app.

But first you have to connect the 06:03 - Bridge to your network. There are two ways: using Wifi or using an ethernet cable. For Wifi you simply press the WPS button on your your router until a LED starts flashing. Then, as soon as the LED on the Bridge starts flashing, use a paper clip or other pointy device to press the WPS button on the rear of the Bridge and you’re set. If you , like me, have no WPS button on your router, you have to temporarily connect the Bridge to the router using a network cable and enter the name of your network and your password in the app’s settings menu by hand. After that you can disconnect the network cable.

Or you can just use the network 06:46 - cable and forget about Wifi. When you start up the app, it will search for a Lindemann network player and when not found it will display this screen. If the Bridge is properly connected, switched on and started up, it will appear in the app. Tapping on it shows the sources available plus a list of last played music. Let’s go to my music servers and select the Syn3T Synology DS119J that runs MinimServer, select Music and brows by album, go 90125 by Yes and start Owner of a Lonely Heart.

Next to the cover art the properties of the music 07:36 - file are shown: Apple Lossless at 2920 kbps, 96 kHz 24 bit, 2 channel. It all works fine. Let’s jump to Tidal. Since it’s the first time I log in, I have to enter my user name and password. I hope you don’t mind I don’t show that. After that just tap login and you see the standard Tidal categories like New albums. Let’s go for Queen Naija and press play. Then the internet radio menu and let’s go to the local stations. Concertzender Vredenburg Live is the station affiliated with the eight concert halls of the TivoliVredenburg concert halls of Utrecht, the Netherlands, at a 20 minute drive from where I live.

Let me also 08:37 - show you the podcast function by searching for the American/Dutch podcaster and Conspiracy Jester Adam Curry. He runs the No Agenda podcast with grumpy old man John C. Dvorak. Now let me show you some settings. For instance the Wifi connection setting [pause] where you enter the name of your Wifi network - the so called SSID and the password, here called Key. I’m not hiding my password for you, of course, but as you know there are some very bad people on the interwebs. As you see here the wired connection is still active since the connection is selected automatically.

Unplug the network cable and restart the Bridge 09:31 - and it will use Wifi for connection. The quality of a network bridge is defined by properties like a clean power supply and phase noise on the digital outputs. These have influence on the correctness of the digital to analog process. Even the tiniest difference in both parameters can - and often will - be audible after the D/A conversion. Even a good digital front end in the DAC can’t correct for this. It will remain audible, clearly audible. Time to see how the Bridge sounds.

10:08 - This is, within it’s price class a very good sounding bridge. Technically correct would be ‘a bridge that in its price class adds clearly less distortion than most’. But that would sound rather negative while it is very good. Comparing it to the bridges I already have is difficult since they all have a USB port as output while the LimeTree Bridge has SPDIF and TOSlink. The only comparison I could make is with the Raspberry Pi with Hifiberry and Allo SPDIF boards. And those are just a class lower.

Comparing it with 10:47 - the SOtM sMS-200 Ultra NEO with sBooster power supply is a bit tricky since I then use two totally different inputs on my DAC. It then is hard to tell to what degree the inputs on the DAC influence the sound difference. But the SOtM/sBooster is the winner, offering more resolute overall and better sibilance control. The results on other DAC’s might differ, depending on the quality of the SPDIF input and front end on that DAC. It doesn’t make the Lindemann a bad product, though. Especially if you consider it’s costing about half the price of the SOtM. And we can use an identical sBooster power supply but this time the 5 volts version. That does bring the LimeTree Bridge closer to the SOtM, especially sibilance control improves. Isn’t it funny that also with vinyl sibilance is one of the known problems. In the seventies Shure issued the vinyl record “An Audio Obstacle course” for the introduction of the Shure V15 type II cartridge.

It was to be used for adjusting 11:58 - the tone arm and one of the tracks was Mas Que Nada by Sergio Mendez. The S in Mas gave severe problems when the cartridge was not mounted correctly or tone arm was not adjusted properly. In the digital world I us Jennifer Warnes’ track Famous Blue Raincoat from the original release of the album with the same name. To clarify the LimeTree Bridge qualities: it finds its place about a third up in my setup 1. Let me first make clear who should not buy the Limetree Bridge: those that want to connect their DAC using USB, for there is no USB Audio output.

Also those using an MQA DAC should 12:43 - look elsewhere since the sample rate conversion will kill the MQA flag. And those that don’t want sample rate conversion of course. But all others buy a very good sounding network bridge for playing music from streaming services and their own collection on hard disk. Even if that collection contains music at higher sampling rates than the DAC can handle. It’s also a very good option for those that seek a Roon Endpoint of quality.

Sure, there are 13:13 - even better network bridges as we have seen, but not at this price for as far as I know. If you know one, let me know. Just name the product but don’t send links for these might not work. Next week a I have another interesting product for you: a DAC that outputs enough power to properly drive loudspeakers directly. So come back next Friday at 5 pm central European time. Afraid you forget, then subscribe to this channel or follow me on the social media so you will be informed when new videos are out.

If you liked this video, give it a thumbs 13:52 - up. I am so blessed with viewers that support the channel financially, it keeps me independent. If you like to support my work too, the links are in the comments below this video on Youtube. I am Hans Beekhuyzen, thank you for watching and see you in the next show or on theHBproject.com. As always, whatever you do, enjoy the music. And keep safe. .