Home made field coil speakers.

[dcathro]

The most important thing is that it makes you feel happy and satisfied.

Well, looks are not that important for me, sonic performance is.

I look at much of the hi end industry now as audio jewellery for men.

If you've almost finished - what kind of improvements are you still considering?

I would say that 95% of people would have said "good enough" on this some time ago, but I am playing around to see just how far I can go with optimising the crossover. We are talking very small changes to slopes and attenuation values and finding the right combination.

 

[AMR / iFi audio]

I look at much of the hi end industry now as audio jewellery for men.

That, indeed, is a very good comparison. Fortunately, audio is little bit more difficult to steal than jewellery

We are talking very small changes to slopes and attenuation values and finding the right combination.

The smallest changes can be a real time-consumer, can't they? Fortunately, feeling of absolutely complete work makes it worth it and defines high quality craftsmanship.

 

[dcathro]

We have been in lockdown in Melbourne again. Since I have not been able to get out and visit or have friends over, I have gotten busy and done many of the little DIY projects that have been on the back burner.


Firstly I have refined the speaker crossover further:









There's not much difference in the measured response, but it sounds quite a bit better.


I did some upgrades on my CD player which uses an Arcam Alpha as the transport, but has a NOS DAC board designed by Chris Bryant in the UK. The DAC board already had copper heatsinks and NX Black Gate decoupling caps round the 1541, but I upgrade the bridge diodes to ultrafasts, and change the DAC chip to a single crown. The Transport part was stock from the 90's and was struggling to play many discs, so it was time for a recap. Rather than modify my already working unit, I bought another Arcam Alpha, which I recapped, changed the 7805 heatsink to copper, added a clock module and the bridge diodes to ultrafast. The machine sounded better and now has no problem playing discs. I also can't get over how bright the display is.









Next up was to replace the lids on the power supplies for the field coils. I bought some perforated perspex sheets from RS and measured up and cut the lids out.





The supplies to the wideband Supravoxes are critical, so I wanted to try some mods to them. They are Chinese made regulated linear supplies, and I just changed the power supply diodes over to ultrafasts and changed the heatsinks over from aluminum to copper. I still have to figure out how to make some non metallic lids for these.




Surprisingly the mods to these were very audible ans better dynamics and greater purity in the mids.

Next up was a suggestion from another field coil user, Ralph Karsten from @Atmasphere amplifiers. Ralph said that he had found the gauge of the wire from the power supplies to the field coils to be critical, and the larger the better. The wires I had were pretty thin, so I made up some really beefy ones from Cat5 cables. Also with the bass supplies, I connected them to the back terminals of the supplies which provide higher current output.




Final item was to connect up a dedicated earth to my isolation transformer which I have always had in the system, but with just the standard earth. Rather than putting copper poles in the back garden, I just connected a thick copper wire up to the hot water pipe under the kitchen sink.





Now I have to think what else I can do for the rest of this lockdown.

 

[AMR / iFi audio]

That seems to have been one productive lockdown.
I can see that you're using The Rest of The Robots as the base of your project. Do you recommend it?

The bridge diodes to ultrafasts, the DAC chip to a single crown, the heatsink aluminum to copper. Just wondering which was the most challenging and satisfying part of the Melbourne lockdown project?

 

[dcathro]

That seems to have been one productive lockdown.
I can see that you're using The Rest of The Robots as the base of your project. Do you recommend it?

Well spotted with the book. I lined the xover boxes with my old scifi books to absorb vibrations. I can't say that I have read that book in the last 40 years. I did love all those 1950's and 60's imaginative stories when I was growing up. Somehow the world seemed more full of possibilities, hope and adventure.

The bridge diodes to ultrafasts, the DAC chip to a single crown, the heatsink aluminum to copper. Just wondering which was the most challenging and satisfying part of the Melbourne lockdown project?

All of these jobs were relatively small, and all went without a hitch. Upgrading the CD player was probably the most involved job. The biggest improvements were gained from upgrading the Supravox power supplies and the cables carrying the DC current. There was quite a dramatic improvement. Copper heatsinks are something that I was shown 25 years ago and have been doing ever since. Even on regulators you can hear the difference - it gets rid of that grey solid state sound, giving more harmonic detail and micro dynamic shading. My power amp has a massive copper heatsink. Ultra fast diodes are also a no brainer for me.

Thanks for asking!