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Because things are never static for too long!

In the living room: gone are the old Intel Atom-based server, the Raspberry Pi for Kodi and the old Intel Core 2 Duo laptop for Roon server. All the services those machines provided are now aggregated into a "less old" Intel Core i5 laptop. Power usage and administration costs will be lowered, with improved all-around performance.

In the bedroom: gone are the Rotel RA-820BX integrated amplifier and the Musical Fidelity V-DAC V1. They are replaced by the Raspberry Pi liberated from the living room, equipped with a HifiBerry AMP2 DAC and class D amp combo (negotiated from another project). Less space and electricity used, and such an improvement in audio quality!

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Mountain house - Washington, USA

This is a project that I have integrated and installed as part as a birthday present. Three zones Roon system, 1 with a DAC and reusing an existing amplifier and set of speakers, 2 using a TI DAC + Class D amplifier (I am extremely positively surprised by how well and cleanly it works, those things got some oomph!). I had to completely rewire the house with Ethernet and add Wi-Fi access points

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Desert house - Dubai, UAE

This was a demo system for a friend's business in Dubai. It has since moved to Dar es Salaam, Tanzania! I've installed it from scratch, including a network remodel (the house was already pre-wired with Ethernet), entirely remotely. Five zones Roon system, using a nice existing Forté + Tannoy kit, or a collection of Focal powered speakers (my friend was a distributor).

I even engineered a mobile system, using a car PC, tablet in dashboard, on-board WiFi and fully integrated DSP system, ready for public demonstration to the local market.

Home system - Redhill, UK

And then there is my 2 zones Roon home system, with multiroom TV+Kodi deployment, quite documented on this web site...

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After more than 10-15 years, you can be certain that the electrolytic capacitors in your amplifier will have aged, leaked, if not worse, and will not perform at their best, making your amplifier a worse performer.

Some of those capacitor are important because they provide an electrical power reserve when volume peaks are needed, some others are on the signal path, some are within the phono pre-amplifier.

A replacement of those capacitors (a recap) is something that is needed at that stage.

Here are the capacitors that will need changing on this amplifier, on the schematic diagram:

Power supply capacitors in yellow, signal path capacitors in pink

Here are the capacitors that will need changing on this amplifier, on the wiring diagram:

Power supply capacitors in yellow, signal path capacitors in pink. Red shows the bias adjustment points and variable resistors

In order to visually help, here are a few shots of the real thing. The two main 8200 µF capacitors for the power supply are not shown here, but you can't miss them, they are the biggest things on the board!

Here is the list and description of the capacitors to change:

ItemNumberVoltage (V)Value (µF)Diameter (mm)Comments
1. Power Supply
C9033582003010,000 µF 35-40V would be ok too
C9043582003010,000 µF 35-40V would be ok too
2. Amplification
C605100106Something like Panasonic FC series
C606100106Something like Panasonic FC series
3. Phono stage
C405104.7"Bead"Something like Panasonic FC series, use 10 µF instead
C406104.7"Bead"Something like Panasonic FC series, use 10 µF instead
C41750106Something like Panasonic FC series
C41850106Something like Panasonic FC series

Here are suggestions for replacement, with references from RS Components:

ItemNumberDescriptionPack ofDiameter (mm)RS Stock NoManufacturer part #PriceURL
1. Power Supply
C903Nichicon Aluminium Electrolytic Capacitor 10000μF 35 V 22mm Through Hole 5101-4 VY Series Lifetime 1000h +105°C122739-5324UVY1V103MRD£3.02
C904Nichicon Aluminium Electrolytic Capacitor 10000μF 35 V 22mm Through Hole 5101-4 VY Series Lifetime 1000h +105°C122739-5324UVY1V103MRD£3.02
C901Nichicon Aluminium Electrolytic Capacitor 2200μF 25 V dc 16mm Through Hole PW Series Lifetime 8000h +105°C516715-2684UPW1E222MHD£4.64
C902Same as above, in the pack of 5-
2. Amplification
C605Nichicon Aluminium Electrolytic Capacitor 10μF 100 V 5mm Through Hole JIS C 5101-1 VY Series Lifetime 1000h +105°C15862-4190UVY2A100MDD£0.24
C606Nichicon Aluminium Electrolytic Capacitor 10μF 100 V 5mm Through Hole JIS C 5101-1 VY Series Lifetime 1000h +105°C15862-4190UVY2A100MDD£0.24
3. Phono stage
C405Nichicon Aluminium Electrolytic Capacitor 10μF 50 V dc 5mm Through Hole PS Series Lifetime 2000h +105°C55519-4289UPS1H100MDD£0.93
C406Same as above, in the pack of 5-
C417Same as above, in the pack of 5-
C418Same as above, in the pack of 5-

For your reference, here are the owner's manual and service manual:

Bought a while ago, very cheap, from eBay, at £30.

They need to be gloss white to blend with the bedroom's furniture.

Slight repairs needed in a couple of corners.

Day 1 - Repairing the corners

Dismantle the drivers and connectors.

Cut the crushed material clean with a knife.

Apply wood filler, let it dry, sand.

Day 2 - Wrapping the first speaker

Day 3 - Wrapping the second speaker

"Practice makes perfect" they say! Well, at least this one is much better wrapped than the first one...

Panda Panda Panda...

Day 4 - White acoustic cloth


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  • New Raspberry Pi 2 and IQaudIO Pi-DACZero (24/192) replacing my old Musical Fidelity V-DAC (only synchronous USB and max 16/48 on USB) and acting as a network streamer using Roon Bridge
  • Roon server installed on the laptop. This software+service+technology is absolute magic. Great interface on any platform (Linux interface missing, though, but core and Bridge rock the penguin's way!), fantastic metadata, and even better contextualisation, and very nice bit-perfect music transport. The radio feature is such a good way of (re)discovering our extensive music library.
  • This IQaudIO Pi-DACZero is quite nice, and it was free on a black Friday event! But I still want to replace it with a Hifiberry DAC+ Pro, with dual oscillators to eliminate any potential jitter from I²S. Missing those parts.
  • I want another Raspberry Pi 2 int the bedroom, this time with an IQaudIO Pi-DigiAMP, a combination of a 24/192 DAC and a 2x35W Class D amplifier. Add that extra pair of Castle Pembroke Loudspeaker that we have... That would be another all-in-one network streamer using Roon Bridge, allowing for independant music, or in perfect synchronisation with the main system! Missing those parts.
  • Eventually, I'd like to upgrade the server from that 32 bit Atom machine to a 64 bit i5 machine. It would incorporate the roles of the current server (good bye!), of the laptop running the Roon server (good bye!) and the main TV's Raspberry Pi (good bye!) and add HD movie audio capabilities and 4K resolution future-proofing. Much simpler, while keeping the power consumption at bay. Missing those parts.

Here is a project going around in my mind... It will most probably never go anywhere beyond that, but here are notes and thoughts.

The goal would be to build an integrated all-in-one music player/streamer with plenty of features, but still relatively simple and with a low cost.



  • Plug-in speakers, plug-in media storage, plug-in power, play music
  • Small footprint
  • Hi-Fi component look with volume control and IR remote capability
  • Plays all music formats (non-DRM)
  • Built-in 24/192 DAC
  • Built-in 35W Class D amp - Speakers terminals
  • Line level output - RCA terminal - For use with discrete amplification
  • 10/100 Ethernet wired network connectivity
  • Wi-Fi network connectivity
  • Possible Bluetooth (but no Apt-X...)
  • Local or network (Windows, NFS shares) music files
  • Built-in Raspberry Pi 3 computer
  • Possible 7" touchscreen integration
  • Lollypop music management app on touchscreen or remote
  • MPD server - Pretty well regarded, provides mobile device remote
  • Squeezebox server and player for easy mutli-room
  • UPNP - Play from anything not Apple
  • Apple AirPlay - Play from your iPhone/iPad/Mac




Something not looking like a computer component, but like a Hi-Fi component.

External connectivity

All serious looking stuff for audio, plus network and storage connectivity


7" touchscreen - 800 x 480
7" touchscreen - 800 x 480


Processing power, DAC, amplifier and electrical power



  • CD drive for playing and ripping


Item Qty Unit Total
Case 1  £58.00  £58.00
Rotary encoder 1  £2.00  £2.00
IR receiver 1  £2.00  £2.00
Banana sockets x4 1  £7.50  £7.50
RCA sockets x2 1  £3.90  £3.90
USB socket 2  £4.64  £9.28
Ethernet socket 1  £4.40  £4.40
WiFi dongle and antenna 1  £4.50  £4.50
WiFi connector and pigtail 1  £1.24  £1.24
7" Touchscreen 1  £57.59  £57.59
Raspberry Pi 3 1  £35.99  £35.99
Pi-DAC+ 1  £30.00  £30.00
Pi-AMP+ FOR Pi-DAC+ 1  £40.00  £40.00
19v POWER BRICK (65w / 3.4amp) 1  £20.00  £20.00
Software 1  £-  £-
 Total   £276.40



These are of the same model as the speakers I own and use. Got a great deal on eBay.

With a minimum of efforts, these should be looking gorgeous on top of being great sounding!

I may keep them (excuse for a second system, anyone? ) or put them back on eBay (but parting with them will be hard after giving them all that attention, and they are such lovely sounding speakers to have. But I need the money these days...). In the meantime, they are providing a very nice way of keeping cleverly busy!

Step 0 - Initial state

Left speaker

Right speaker


Step 1 - Fixing the left bass driver

Unglued spider
Unglued spider

After checking that the electronics were not in a worrying shape, I plugged the speakers into the amplifiers... The spider on the left bass unit was detached from the basket, which generated vibrations; nothing dramatic. Nothing that Superglue Gel wouldn't solve!

13661921_10153845918651973_2581469085835065427_oAnd indeed, after 12h, I plugged the speaker back, and did some testing. A few clean sine waves (40 Hz and a few others in the low range, generated using Audacity), then music, starting with Limit To Your Love by James Blake, as it proposes a great mix of electronically generated deep bass along with a generous helping of the rest of the audible bandwidth.

Back to sounding as good as new, properly gorgeous: very clean sound, articulate medium, tight bass (amazing for the size).

Step 2 - Wood restoration, right speaker


  1. Clean with a damp cloth
  2. Dry with a dry cloth
  3. Use 000 steel wool
  4. Get rid of the dust with a dry cloth
  5. Apply Restor-A-Finish with 0000 steel wool
  6. Wipe dry
  7. Wait for 30mn
  8. Apply Feed-N-Wax
  9. Wait for 30mn
  10. Wipe with a clean cloth
  11. Buff with a soft cloth

Let's compare directly...

compare right plinth compare right side

Step 3 - Wood restoration, left speaker

Plinth progression

Right side, before and after

Final result

Step 4 - Fixing the right tweeter

So, either the tweeter broke since the first test, or I wasn't too careful and too focused on the vibrating bass/medium driver! In any case, zero treble from the right tweeter...

After testing the components of the crossover network (all good) and applying a 10 kHz sine directly to the twitter (no sound), I unsoldered it and measured an open loop.

Finding an original component might prove difficult, and I am not too keen on using a pair of new but non-original tweeters. So I performed open driver surgery. What did I have to lose?

The small wire between the voice coil and the connection post is broken.

Four positive factors:

  1. The cut is close to the connection post, far away from the voice coil, in a place where it is completely static
  2. There is a possible overlap of the two broken ends
  3. The enamel used for isolation appears to be pretty easy to get rid of
  4. I have measured the voice coil between the loose wire and the other connecting post at 5.3 Ohm. The voice coil is in a good shape!

I need to find someone better equipped and more experienced than me to solder this, especially as it may be aluminium wire and thus need special solder (Alusol).

Step 5 (much, much later) - Finally fixing the right tweeter

Many attempts later, a trip to France and multiple phone calls and visits to specialists, all with no positive result, that voice coil wire is decidedly too thin...

Last hope attempt, as it was more or less a make or break forever: I used a short length of copper tube (from a models/hobbies store) filled with a bit of solder wire and speaker cable elements, then inserted my two pieces of voice coil wire on each end. I applied heat from the soldering iron to melt the solder, and voilà! Contact, continuity and correct direct impedance! A few drops of super glue made sure that it will never, ever move around.

I soldered the tweeter back to the filters, put it all back together and started playing with HF sine waves. Sounds perfect! The test tracks provided a lot of pleasure too!

Step 6 - Castle logo badges

Well know problem with Castle speakers: the logo badges break and drop off the cabinets. It is also quite difficult to source new or old badges due to the complicated history of the brand.

Of course that pair is missing its logos.

I used an online-sourced image of the logo, tweaked it in The Gimp, made is a vector-based SVG drawing in Inkscape, then transformed it into a 3D model using Tinkercad.

There is an online community of owners of 3D printers selling printing services, a bit like Uber for 3D printing. It's all on 3D Hubs, and, most importantly, there is a guy offering his services literally up my street. I was delivered the following in less than three hours, for the grand sum of £1.98!

Text and specs

Stylised PembrokeOur smallest floor standing system, the Castle Pembroke combines high performance with great flexibility. That is because it uses our acclaimed downward firing reflex port technique. This gives the twin advantages of dispersing the ‘chuffing’ effect common to all forward firing reflex designs and allows greater freedom of room placement. The Pembroke can be positioned very close to a rear wall without impairing sound quality.

A 130mm carbon fibre coned bass unit with a shaped 30mm pole, oversized magnet and long throw voice coil gives the Pembroke performance which belies its compact size with bass extension down to 52Hz. High frequencies are handled by Castle’s own low modulus polyamide dome tweeter used in many of our Classic Range models for its smooth extension, clarity and accuracy. Overall smooth, dynamic response is assured by the Pembroke’s audiophile grade crossover which also offers the option of bi-wiring.

Frequency Response 45Hz-20kHz
Nominal Impedance 8 ohms
Sensitivity 87dB for 1W at 1m
Amplifier Requirements 15-75 Watts
System Type Downward firing reflex
Bass Unit 130mm (5 in.) woven carbon fibre coned, cast chassis
Treble Unit 19mm (.75 inch) low modulus polyamide
Height 710mm (28 in.)
Width 190mm (8.4 in)
Depth 220mm (8.7 in.)
Weight Each 9.7kg (21.3 lbs)
Weight Packed 22kg (48.4 lbs)


Castle Classic Brochure
Castle Classic Instruction Manual
Instruction Manual

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