Testing outside the box

DSC00808

Space is a bit tight inside the box, so I’m just testing the RIAA amplifier on a few records before I install it permanently inside.  So far, I’ve got through these but the queue is growing!

  • Cowboy Junkies – Trinity Sessions
  • The Pogues – If I should fall from grace with God
  • Lou Reed – Transformer
  • Fat Boy Slim – You’ve come a long way baby
  • various Jazz
  • Radiohead – the Bends
  • vaious Sinead O’Connor

There is something about listening to vinyl that’s lost on CD’s.  It’s making me very happy to hear the difference again!

We built this city,

We built this city on silicon!

Silicon City

Silicon City

Just thought this board looked a bit like a city with towers, houses and roads.  In fact it’s a very-low-noise balanced-input audio amplifier with active ground-control (to Major Tom?) and RIAA filters for playing vinyl records.  Records are not cut with a flat frequency response; the bass is reduced as is the treble so that the cutting / etching of the track stays within physical bounds.  Playing a record requires the reverse filter at 3180us (50Hz low pass), 318us (500Hz high pass) and 50us (2120Hz low pass).

And yes, there was a deliberate decision to colour coordinate the components as long as quality wasn’t compromised – much like what I’ve done to Phoebe and Chloe recently.  In fact, for Phoebe, Chloe and this PCB, colour choice has forced higher quality components to be used.

I call it creative OCD art and it gives me great satisfaction!  Horowitz and Hill were not wrong with the name of their classic book.

Thanks again to the fab folk at Ragworm for producing the PCBs.

Irony is when…

you order some bubble wrap from Amazon, and the box and packing material Amazon use are actually far better suited to what’s required than the bubble wrap itself.

The moral dilemma now is whether to send the bubble wrap back but keep the Amazon box and packing materials?

The packing is for an Arcam FMJ CD 23 Ring DAC CD player – a ground breaking CD player from the turn of the millennium and still highly rated going by what they are selling for on ebay.  I am selling mine as all my CDs are transferred to Apple devices, and very expensive HiFi has no place in a home with 2 manic kids!

Knobs!

No, not the Jeremys Paxman or Clarkson, but these:

Elma K1 knobs

Elma K1 knobs

They can be had with 4mm or 6mm shafts suiting both the 4mm shaft of the 2 pole 6 way Elma switch I got from HiFi collective I’m using, along with the 6mm shaft of the Vishay 50k logarithmic rotary potentiometer I got from Farnell.

Here’s the amplifier with the dimple knobs in situ:

Knobs with dimples

Knobs with dimples

I bought these from 4most electronics, who have a stock now of 19 of each of the 6mm and 4mm dimple and dome type.  Their website is bit out-of-date, but they are the main distributor for Elma (including audio quality switches) in the UK.  Haydn has been very helpful to me, so I recommend you contact him directly.

This might sound like a bit of paid advertising, but it’s unpaid; one of the hardest things I’ve ever found about DIY HiFi is finding hardware that looks as good as the circuitry sounds.  And finally, I think I’ve achieved it thanks to their kind help!

Behemoth’s Baby Bro’

Behemoth's Baby Bro'

Behemoth’s Baby Bro’

At the moment, BBB only supports a single line input (red wires), but in the next (and final) revision, I’ll solder the other lines inputs on (orange and yellow wires), and add the RIAA pre-amp into the gap by the XLR connector (blue wires), but first I need to rework the PCB: space in the box is tighter than I’d expected.  Also there’s some minor drilling errors on the rear panel that I’d like to tighten up, and there’s a batch of new knobs on the way, which I hope will make him look a bit more professional.

BBB's insides

BBB’s insides

First trials suggests she sounds great, particularly how little she cost compared to Behemoth and her Chord SPM 600 power amp, the sale of which funded most of this project.

And best of all, the road-block with Phoebe and Chloe has been lifted by an article I found yesterday which will enhance the accuracy of angles (download Refining Euler angle precision and have a look at sections 2.1 onwards for a spoiler).  I’ll post more details once I’ve updated and tested the code.

Behemoth

My original preamp from the turn of the millenium:

My OTT preamp

My OTT preamp

OTT preamp internals

OTT preamp internals

Back then, it was top quality in every possible way, but I never got to do the corresponding power-amp as there’s something something a bit too “zen” about them – reams of transistors, resistors and capacitors, and lots of complex calculations along with guesswork and testing.  I simply wasn’t smart or experienced enough, so I bought this instead:

Chord SPM 600

Chord SPM 600

I’d never liked my Behemoth’s big black case but there was nothing better at the time.

But times have changed and I started thinking about moving the insides of the Behemoth into this much smaller slicker case from ebay:

S-2207 Aluminium Enclosure

S-2207 Aluminium Enclosure

The idea started as two of these boxes splitting the Behemoth into an RIAA- and pre-amp in a box each.

Then I stumbled over these:

Class-D power amp

Class-D power amp

 

Class-D power amp

Class-D power amp

Class-D power amp

Class-D power amp

Tiny PCBs using the Texas Instruments TPA3116D2 and high quality components.  Available on ebay for £9; so a third box then as the power amp?  Essentially a top of the range DIY HiFi system costing under £100 by reusing parts of the Behemoth.

So I bought cases, and started drilling holes, but as this progressed, it slowly dawned on me that everything could fit into a single case, so be super-cute too.  And that’s my latest project.  There’s not much technical content, but I’ll post up bits and bobs as and when.

My get up and go just got up and went!

You might have noticed the tag-line in the blog header has just changed from “Stuff to fulfil your Raspberry Pi!” to “Raspberry Pi and other Stuffing!” – I’m broadening the scope of this blog outside of Raspberry Pi land.

Things are grinding to a halt with Phoebe and Chloe; I have a small rebuild to do on Phoebe to add her new grommets and ESCs, but that’s only going to bring her up to Chloe’s standards at best.  I have some testing to try with the 0g offsets being zero at ambient / boot temperature, but I’m not convinced that’ll come to much.  And until I can get the horizontal drift reduced, then there’s no way I can even think about implementing kitty, the laser tracker..

I’ve always struggled to hang on to a full time hobby for more that a couple of year before my interest drifts.  This Quadcopter project has done well at 30 months and I would keep going if I had any ideas left of where to go, but I’ve been going round and round in ever decreasing circles for a while now, and I have to stop before I vanish up my own sphincter!

I’m sure I’ll never be far away from this project, and will be back periodically with a new idea, or perhaps just a new video after a sunny day (i.e. few seconds) flying the girls in the park.  But for now, time to let the girls rest, and enjoy the sunshine.

Me? Well I’d previously mentioned my interest in DIY HiFi and something over the weekend set that Rolling Stone off again.  More on that anon.