Paul Hynes SR7EHD PSU - unlocking the latent potential of my Technics SL-1210

[Marco]

Hi Gareth,

Dip in every now and then to see what's happening-much progress since I fitted a Kabusa p/s to my pair of Mk5s a few years back now..Just wish I had spare funds to catch up with the latest!
Marcos deck was impressive enough last Scalford, l hope to hear it at the next one with the latest additions. Good work!

Cheers, mate. Glad you liked my T/T last time. Hopefully when you hear it again next year you'll like it even more!

Marco.

[Paul Hynes]

Hi Marco,

The Clearsilver XL fine silver lead I sent you was terminated with silver plated contact XLR connector that I fit as standard on standard SR5 and SR7 power supplies. This was done so you could use it with the standard SR5 power supply.

I have not tried the Furutech connectors on this lead but would expect an audible upgrade over the XLR connector that I fit on the standard leads. The XL connector I fitted to your SR7EHD power supply was chosen because it has a contact resistance of less than 1 milliohm. It is a precision industrial connector that complies with military specifications across Europe and the USA. In other words it is a very good connector. I do not know how it will compare with the Furutech connector but if the Furuteck is a better connector I will be happy to fit this to power supplies on request.

I have been selling the Clearsilver XL cables for a long time on a custom build basis. The configuration of the triple core woven cable is not new. I just applied the parameters of cable construction that I felt were valid for very high quality sound reproduction. Basically a single solid core conductor per core using Fine Silver conductors and low-loss dielectric insulation. And a controlled annealing process to relax the molecular structure of the silver after cable construction.

I use the same physical configuration for DC power leads, signal interconnects, loudspeaker cables and mains power leads (with additional insulation layers to comply with safety regulations) but vary the core diameter according to the electrical requirements of the equipment the cable will be used with.

This cable construction satisfies my requirement for musical coherency in my system.

[Marco]

Hi Paul,

Many thanks for the info - noted. It'll be interesting to see which cable and sockets/plugs are best. I will report on the outcome when I've conducted the test

Marco.

[MartinT]

We were listening to Paul's Clearsilver XLR balanced cables between my preamp and power amp on Saturday and they were sounding mighty fine. I have ordered another set to replace the Canare cable between my phono pre and preamp.

[Marco]

We were listening to Paul's Clearsilver XLR balanced cables between my preamp and power amp on Saturday and they were sounding mighty fine

Yes, I'd forgotten about that; indeed they did!

Marco.

[Marco]

Hi Paul,

I meant to draw your attention to this which I wrote earlier in my mini review of the SR7:

Although such a huge power supply for the Technics is arguably WAY 'over the top', in terms of the measurable current it can draw (and some would therefore say unnecessary), listening tests clearly indicate that there are still significant sonic gains to be had by going down the over-specified transformer route. It is beyond question to my ears that, with the Technics SL-1200/1210, latent potential exists, waiting to be untapped, when the use of a judiciously over-specified external PSU is employed. Paul I'm sure will provide the technical rationale.

Perhaps for the benefit of people reading you could outline your rationale there? Churz!

Marco.

[Paul Hynes]

Hi Marco,

Firstly, any electronic circuit can be strangled by an inadequate power supply, and secondly, there is no such thing as a free lunch in power supply design.

The ideal power supply will have ZERO impedance at ALL load operating frequencies. It is not possible to generate any voltage change across a zero impedance source no matter how much current you pass through it. Therefore there would be no interaction between the power supply and the load. Unfortunately, this ideal power supply does not exist in the real world, as far as I am aware, as the available means of controlling impedance are not ideal.

Real world power supply designs differ enormously in their abilities. Power supplies are only as good as the designer’s acquired knowledge and his product budget at any given level. If you only have a budget of £35 for the material costs of the power supply design you are not going to come up with the finest power supply on the planet. If you insist on using industry standard three terminal regulators, because this is how you are taught at college or university, you are not going to get there either. In fact there is just as much performance variation from design to design as there is with amplifiers, preamplifiers, vinyl front ends, loudspeakers and digital electronics. It erroneous to class all power supplies as just power supplies as they radically affect the performance of the equipment they power.

So what is the rationale behind the SR7 range of power supplies?

The SR7 is a heavy-duty version of the SR5 power supply capable of powering anything from a Mac Mini to a power amplifier with the appropriate selection of components. The regulator circuit topology used in these power supplies has been designed from the ground up as a high performance DC amplifier with a wide AC load operating bandwidth, fast transient response and settling time, very high transient current delivery and very low wideband noise. This circuit topology is the result of many years of dedicated R&D aimed at approaching the ideal power supply performance as closely as possible. If I had a better topology for this application I would be using it.

The improvements over the SR5 come from :-

Increasing the size of the mains transformer. I have already described the mains transformer spec briefly on another thread. Essentially it is custom designed for optimum operation, avoidance of core saturation problems and low operating noise both electrically and mechanically. Making it larger means it has an easier time delivering the goods downstream.

A balanced rectification arrangement has been applied for both supply rails feeding the regulator circuit. The secondaries are always referenced to the 0 volt rail whether the rectifiers are conducting or not.

The energy storage capacitance has been increased by a factor of 4.

Some modifications to the regulator circuit have been applied but I am not at liberty to discuss these, as the regulator topology is the subject of consultancy client non-disclosure agreements.

The net effect of these changes is that the regulator circuit has an easier life as the quality of power that feeds it has been significantly improved, reducing any interaction between the two and load regulation has been improved. As you have found out you can hear this effect directly as improved sound quality in your system. The supply line rejection of the regulator is very good, and extends over a much wider bandwidth than other power supplies generally available, however this rejection is not infinite and this is why it is possible to hear improvements with transformer, rectification, energy storage capacitance and indeed regulator topology changes.

I hope this helps.

Regards
Paul

[Mark Grant]

Looks like I've made the right decision once the extras arrive (Can't find a Furutech FP-682F(R) anywhere in the country),

They are usually a special order item as the Furutech UK distributor does not have any in stock.

Marco had to wait a while for that one, it was easy to fit though

The other connector with threaded locking ring (not sure what its part number is) that Paul has fitted as standard does look high build quality so might be all you need.

This new PSU is a beast of a thing

[MartinT]

Marco - did we resolve why your SR-5 (and presumably your SR-7EHD) has a three-pin socket while my SR-5 has a four-pin? It made immediate PSU swapping impossible.

Paul - what is your standard socketry for PSUs intended for the Technics?

[Paul Hynes]

Hi Martin,

I usually fit the following :-

Standard power supplies.

For the SR3 power supplies a gold plated terminal Lumberg precision 4 pin DIN.

For SR5 and SR7 single supply rail power supplies a silver plated terminal 4 pin XLR

For SR5 and SR7 multi-rail supplies I fit silver plated terminal 4 and 5 pin XLRs in multiples as required.

The use of the 4 pin DIN and XLR is to avoid the possibility of plugging a 3 pin signal lead into the power supply.

XL power supplies (these XL connectors are not physically compatible with XLR connectors so no danger of plugging a signal XLR into the power supply)

For the SR3 power supplies a silver plated 3 pin XL connector.

For SR5 and SR7 single supply rail power supplies a silver plated terminal 3 pin XL connector

For SR5 and SR7 multi-rail supplies I fit silver plated terminal multi-pin XL connectors as required.

I do fit custom connectors as required by the customer as some have their favourite connector type.

I fitted a 4 pin XLR to your and Marco’s XL DC leads as you already had 4 pin XLRs on your SR5 power supplies. This was to allow Marco to assess the use of the Clearsilver XL wiring arrangement on his deck and was replicated for you.

Regards
Paul