Author Archives: remco

Got Kodi? Got Lyrion? Boomer or Gen X? Get this.

I’m a genX-er and have spent most of my life either being a remote control for a Boomer or using a remote control with no wifi and no screen. And just like I hate cars with touch screens, I want haptic feedback on my playback device as well.

For the longest time I’ve been running Kodi on my media center attached to the TV, since you can map remote control keys for media control. But as nice as it is for video, Kodi kinda sucks for music playback.

Boomerlamp controlled by Boomerbox

Boomerlamp controlled by Boomerbox

Roon is not for me for many reasons, and Kodi doesn’t offer Spotify or Tidal integrations and I still have my local music storage. Enter Lyrion (formerly Logitech Media Centre) that does all I need and is open source. Win. Now I can push a Tidal playlist to Lyrion and enjoy a mix of local or remote streaming.

But then Kodi just sits there and goes ‘who stole my audio’. Sure, you can turn off the TV entirely and read a book, but I already finished my book. And I want to skip tracks with an infrared remote like it’s 1992 again. For some reason there wasn’t a working plugin for Kodi that can interface with Lyrion. So I guess you’ll have to do with whatever I could whip up with an agent on a Saturday evening.

https://github.com/itsonlyaudio/Kodi-Lyrion-Control

No warranty expressed or implied. Repo abandonment almost guaranteed. But I’m enjoying music playback again, and so should you.

Harman / Kardon Citation eleven resources

Usual disclaimer: not my main work, we do not accept repairs. (but by golly, they do seem to find me).

In order to save anyone working on this amp a bunch of time, here is everything you need to fix this amp. The circuit is about as simple as my old sacdenhancer, so no need to go into that.

Service manual

https://elektrotanya.com/harman_kardon_citation-eleven_11_sm.pdf/download.html

User manual / specifications

https://www.manualslib.com/manual/279186/Harman-Kardon-Citation-11.html

PCB holder

A very nice construction style. Unfortunately 40 year old plastic gets brittle and I broke one just by looking at it the wrong way. So here’s a 3D print model.

EQ section hum

The equalizer is open loop and has no PSRR, so you can’t expect better than 600 uV of hum overall (spec: -80 dB relative to 6V = 600 uV).

If the EQ section picks up more than 1 mV of hum with the 60 Hz slider all the way up and maximum volume, this is due to L601 picking up stray magnetic field from the mains transformer (L601 and C607 are tuned to 60 Hz).

L601

L601

The citation eleven on my desk had two different L601 coils in each channel and I didn’t know which one was the original. But one was wound in such a way that it picked up over 6 mV, i.e. probably a replacement not wound symmetrically. The metal shielding is not effective on magnetic fields and in fact amplifies the field lines as it creates a short circuited winding. So the coil should be magnetically shielded and wound symmetrically.

There is a replacement coil available that is shielded correctly and brought the hum well under 300 uV. I remcomend it over the original, even.

The full DSS930 reverse engineering

Last time we looked at the amplifier output and found some strange problems. This time we isolate the DSP and verify that in fact, the problem comes from here and is actually worse than previously thought.

 

Now that it’s clear we need to design a replacement DSP, we need to understand all the system level communication going on. With the help of some probes a logic analyzer, a spreadsheet and educated guesswork we managed to do just that.

Files -as promised in the videos- here:

https://www.itsonlyaudio.com/files/HOST TO DSP commands.ods

https://www.itsonlyaudio.com/files/DSS COMMAND MANCHESTER DECODING.ods

https://www.itsonlyaudio.com/files/digital gain vs volume step on RC.ods

The circuit boards for the upgrades have been gathering dust for about a year already. Customers seem to not judge this my highest priority, and fair enough. But fear not, wheels are turning. Next up: upsampling.

Stream Unlimited CD-80 (Quad CD-99II)

No video this time, as this was supposed to be a 1-hour job… that ended up on the back burner with all the other projects for 3 months. Paying customers come first…

This is a Quad CD99-II, a friend asked me to check why it no longer read discs. Apparently it had been reading only about half of them for a while, and when that symptom was ignored, it had stopped altogether. Continue reading →

Philips DSS930 – A Loudspeaker Ahead Of Its Time. Part 1: A Dark Secret

In the early 90s Philips were at the top of their game when they introduced the DSS930, a digital-input only, active DSP loudspeaker far ahead of its time. We got our hands on a pair, investigate the design and the state of these classics and discover a design flaw that has gone unnoticed for 30 years.

 

 

 

Functional check and repair of a Bose 1800 “Professional Solid State Dual Channel Power Amplifier”

 

bose1800 thermal cam

Fire in the disco

 

Two posts in one year? Is the world ending? Well, yes, but not just today.

I’ve been visited by a pair of handsome Bose 1800 amps over the past weeks. They needed a DC output delay / DC protection relays because apparently that tech did not yet exist in the mid 1970s. Those solid state devices were still a bit scary, I suppose. Continue reading →