New SL1200/1210 external power supply

[Paul Hynes]

New SR4-21 Technics SL1200/1210 external power supply.

There have been a number of threads about power supplies on the AoS forum where people have said they would like one of my power supplies for the Technics SL1200/1210 but cost has been an issue. I decided to do something about this and I have designed a linear power supply for those on a restricted budget.

High performance for a given cost is a must for any product I design, so I have spent some time on the circuit R&D over the last year and arrived at a nice discrete component regulator circuit, that is a considerable improvement sonically over the typical three terminal regulator offerings currently available.

There are several important areas that require consideration for power supply performance and I paid particular attention to the following parameters.

Low output noise is provided by the use of high quality, low noise components used in a low noise circuit configuration.

High supply line rejection achieved by driving the low noise voltage reference, and the regulator error amplifier, from the regulated output voltage, rather than the unregulated input voltage. This increases the supply line rejection considerably giving >80 dB rejection from DC to 100 KHz with around 50 dB rejection at 10 MHz. For comparison the LM317 regulator supply line rejection is around 80 dB from DC to 1 KHz but it falls above 1 KHz to the point where it reaches zero at around 10 MHz which allows more RFI interference through due to poor rejection ability.

Fast transient response and settling time, together with wide operating bandwidth, is essential when dealing with varying load currents that can extend to frequencies considerably higher than the audio bandwidth, for example with digital circuitry. This is important to maintain the output voltage regulation with dynamic loads. The error amplifier devices have an operating bandwidth of >150 MHz and the output device can swing from a few milliamps to the full rated output in <500 nanoseconds. This is a factor of 10 better than a voltage regulator based on an LM317 typically used in general purpose linear regulators.

Low output impedance is also important as, this will dictate how much regulator output voltage fluctuation will occur for a given change in load current. The regulator output impedance is <5 milliohms from DC to 100 KHz ensuring tight regulation under large dynamic load current swings.

The SR4-21 power supply can provide up to 1.4 amps continuously and the output stage is fully protected against short circuit and thermal overload. The power supply comes complete with an IEC mains lead and a high quality DC lead.

The SR4 costs £195 including VAT. The power supply can be shipped worldwide and insured carriage and packing in the UK costs £12. International shipping costs can be quoted once the destination is known. Payment can be via Credit or Debit card (excluding AMEX), Bank Transfer or Paypal. Cheques accepted subject to clearance.

The product worldwide guarantee covers parts and labour for three years from receipt of goods, subject to correct application, and is transferable should you decide to re-sell at a later date.

There is also a 56 day, return if not satisfied guarantee for standard products. This allows a reasonable burn in period before appraisal.

The SR4 is the first product to be designed and manufactured via the new manufacturing partnership of Paul Hynes and ACS LTD and it will be manufactured at the ACS facility in Norfolk. Sales enquiries should be directed to David Webb at ACS.

David Webb can be contacted at :-

Advanced Camera Services Ltd
Unit 10 Linmore Court
Threxton Road Industrial Estate
Watton
Norfolk IP25 6NG

T 01953 889 324
F 01953 880 086
ACS_2005@BTconnect.com
www.advancedcameraservices.co.uk
Opening Times 9.30am–5.30pm Mon–Fri

If we can be of further help let us know.

Regards
Paul and ACS

[WOStantonCS100]

Loaded question to ask a manufacturer, generally speaking (how good is a lower cost version compared to a higher cost version); but, since, per this forum, I've known you to be nothing but straight forward, I have to ask.

How far off will the SR4-21 be compared to the SR7-EHD in performance?

[Paul Hynes]

The SR4 sits comfortably just behind the SR3 regarding sound quality. I have used a different circuit topology than the SR3 due to budget constraints. The SR4 easily outpaces any of the typical three terminal chip linear regulator supplies like the LM317 and the various clone updates by other manufacturers, and for this reason alone it is a valid product option. The SR3 is quieter than the SR4 and it has a more musical presentation. The SR5 builds on the SR3 performance by using a 160VA custom-built mains transformer and upgraded rectification and regulator output stage. The SR7 goes a step further with a larger 250VA custom-built mains transformer and the rectification and output stage are further upgraded together with an increased energy storage capacitor bank.

As you move up the range, timbre, tempo and timing improve and the dynamic scale increases in both directions. Image stability is also progressively enhanced, particularly when the music gets busy. The differences between the power supplies are easily heard. If any two of the power supplies were so close in performance that it were hard to hear the difference, one of them would be redundant in my view, and it would not be worth offering both.

Biff, it really comes down to what engineering can be done at a given price and, in this instance, you get what you pay for. I cannot give you SR7 performance for the price of the SR4. The mains transformer alone that is used in the SR7 costs considerably more than the total material cost of the SR4.

If there were no budget considerations and you were to compare the SR4 to the SR7, you would choose the SR7 and this would be an instant decision, as the difference between the two power supplies is substantial. If your budget were limited to say, £200, and you compared the SR4 to a typical three terminal chip regulated linear supply you would happily choose the SR4, as the difference here is also quite substantial and certainly enough to warrant the cost of the SR4.

I have tried to be straight-forward as usual, but the question “How far off will the SR4-21 be compared to the SR7-EHD in performance?” is a difficult question to answer as it will depend on the overall resolution and transparency of your sound system. You should hear a difference with any system as you will be upgrading the resolution of the deck, but it will be much more obvious with a transparent system.

Regards
Paul

[julesd68]

The product worldwide guarantee covers parts and labour for three years from receipt of goods, subject to correct application, and is transferable should you decide to re-sell at a later date.

There is also a 56 day, return if not satisfied guarantee for standard products. This allows a reasonable burn in period before appraisal.

I've got to say this is quite exceptional customer service.

Paul will be my first port of call when I want to upgrade the Timestep I'm collecting on Saturday.