D.I.Y Trichord Dino+ PSU

For the past year or so I've been happily using a Trichord Dino mk2 phono stage.

The Dino was a big upgrade over my previous set-up and it has a very fast/tight sound.

As standard the Dino comes with an external power transformer which links to the phono stage via an 'umbilical' cord and 4 pin Din style connector. The standard transformer is a 40VA toroid which feeds 18v AC to the Dino. Rectification and filtering is done by a 4 diode bridge rectifier and 2 large(ish) smoothing caps.

Trichord Research offers two upgrade options over the standard power supply.
The first level upgrade is to the Dino+ power supply (RRP £292) and the second level is to what Trichord call the 'Never Connected' PSU (RRP £514).

This thread shows my attempt to make an upgraded power supply for my Dino which is hopefully roughly equivalent to the Dino+.

According to information on the Trichord Research website:

The 'Dino +' Power Supply unit comprises of two completelly independent and isolated dc supply circuits. One for the positive voltage rail and one for the negative, The specially made low noise audio 80VA toroidal transformer is followed by two bridge rectifiers built with ultra fast soft recovery diodes for low RF genration. The bridges are followed by RC/RC filtering comprising of 4 x 1800uF capacitors before conventional 3 pin voltage regulators. This level of filtering and regulation provides very low noise power supply lines before entering the main amplifier unit.

Here's my attempt to replicate the Dino+ as a D.I.Y project.

I chose to use a ready made PCB from Rod Elliot Sound. This is the PO5 board.
You can see a bare PCB in the foreground an the populated PCB in the background.
The four large capacitors are 2200uf Rubycon ZLH, the smaller ones are Rubycon YXF. I used Schottkey 11DQ10 diodes for the rectifier and normal 1N4004 elsewhere.
The resistors are a bit of a mixture but they are mainly 1% tolerance metal films.

On the left you can see the voltage regs attached to a home-made heat sink which I made from aluminium corner strip bought at my local B&Q. The regs are LM317T and LM337.


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I sourced at bare aluminium case from Maplin and sprayed it satin black to match my other kit.
I ordered the transformer online from Airlink transformers. It is an 80VA toroid with 2x 20v secondaries. I connected two of the leads together to make a centre tap giving me 20v-0v-20v.
I mounted an IEC plug inlet on the back of the case, a power on/off switch and drilled a hole in the front for a power indicator LED.
I contacted Trichord Research and they kindly sold me a one of the PSU connectors for just £4.80 inc VAT and P&P.


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The instructions for the Dino state a power supply voltage of 22v DC. Amazingly I'm getting exactly +22v and -22v DC on each rail.


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Four self adhesive rubber feet on the underside complete the job. These feet came from Maplin and interestingly they appear to be the exact same part which Linn used in the 90's. So if you need spares for you Linn LK85/140 you know where to get some.


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The finished article looks quite smart.


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I haven't done much listening yet but it's a clear improvement.

 

Very nice, and with the positive benefit of keeping AC rectification outside the phono (=high gain) stage box; rectifiction is a very noisy process.

I'm not sure if the board has been updated from the ESP project 5 schematic (http://sound.westhost.com/project05b.htm) but I'm mildly surprised it doesn't use the optional capacitor across the lower voltage -set resistor (R4A or B; R6 a or b). Popping 10uF in there would pick up at least 10dB of performance (ripple rejection, noise, and output impedance) per the datasheet...

It could be dead easy to do if the pads are already on the PCB i.e. if R4A and R6A are used but R4B and R6B are free - add a cap to each o fteh latter!

- Yes I did sent this suggestion to Rod Elliott

 

Excellent work.
Looks very neat and nicely made.

 

Thanks Rob and Martin,

I've been listening this evening at it quite an improvement over the standard PSU.

Martin, do you mean like this?


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Oh and obviously the same on the the R4A/B side with the LM317.

If I understand correctly I could remove R4/6 B and solder it under the board in parallel with R4 A/B (as shown in the sketch above).

A 10nF (ceramic?) cap could then be put in the place where R4/6 B came from.

 

Yes I think that has to be the main benefit really! It's all well and good getting a low noise DC feed but if there is lots of EMI and RFI, from nearby TXs and rectifiers that's rather pointless.

MJP,

Haha.. same tricks come up again and again. How about a zener

 

Hi Simon,

Airlink offer various upgrade options on their toroidal transformers. For a bit extra you can specify them with an electrostatic screen or GOSS steel band. Have a look here:

http://www.airlinktransformers.com/..._transformers_standard_range/3-CM0080225.html

What's your opinion on these upgrades?

Yes, I may well be buying more zeners now that I've learnt that trick!
I'll see what my 3-pin Guru (aka Martin) advises.

 

Oops just realised that Felix wrote 10uF and not 10nF.

Good job I haven't done anything yet!

Apart from the 10nF/10uF mistake is my schematic correct?

 

Looks right to me, but make sure the cap polarity is correct.

 

I finally got around to fitting a couple of capacitors across the voltage set resistors as recommended by Felix earlier in this thread.

There is no room on the top side of the PCB but I managed to squeeze them in on the underside of the PCB.

The ESP PO-5 board employs a pair of voltage set resistors in order to give more scope for setting different voltages, these are R4 A/B and R6 A/B.

I used Rubycon YXM 63v 33uF


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Good work.

Might be worth keeping Rod Elliot in the loop for a future board revision.

There's a 'never connected' PSU for the Gyrodec built by Trichord for Michell (or under licence).
I'm not sure a motor already driven by a conventional regulated supply would benefit but I've often thought of trying one.

 

Rob

Never had a response

 

That's a pity. You've only advised on a simple way to improve things.

I once emailed with a question regarding a mod to one of his EQ circuits and got a response, albeit three weeks later

I'd give him the benefit of doubt of just being very busy.

 

He does mention using a capacitor between the adjust pin and ground here:

http://sound.westhost.com/articles/power-supplies2.htm

For lowest possible noise, a cap is commonly used from the adjustment pin to earth (ground), and this should have a discharge diode fitted between the adjust and output pins (oriented appropriately for polarity of course).

 

As another slight refinement I've put the AC lines to and from the transformer together as twisted pairs.

I know the wires could be shortened considerably but I don't want to cut them short in case I end up wanting to re-use the transformer again on a different project in the future.


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I've been promising myself a nicer powercord to link the Dino to the PSU for while and I finally got around to it a few weeks ago.

Here is it:


The cable is multi-stranded copper and is available from Farnell priced at about £4 per meter. The connectors are the same as those used by Trichord and are available from eBay.

The new cable is about 70cm long which is all I need in my installation.

 

Any chance you could give me a link to the specific Trichord PSU connector. I think i know which type but would appreciate confirmation.

I have a Trichord Delphini MKII and would like to see if i can improve on their standard cable.