Phono stages

iota-audio-design  “small things that matter”

**** New developments & special offer!****

iota signature reference & medianBalanced phono stage, now Rev II

“the second incarnation of these high spec reference products

We are offering an opportunity for all existing owners of the original iota signature reference, and the iota Median balanced phono stages to upgrade any previous version of this product to the recently released REV II versions. The cost of the upgrade is just £240.00, and this will include any service or repair that may be required to the phono stage or power supply, and this will apply if you are the original owner or you purchased the equipment second hand. Following this significant performance upgrade the recalibrated item will also then benefit from a full one year guarantee, whatever its age, and remember the first version of these products was introduced in 1998!

Background and history
The origins of this product go back to 1995 when the speaker and electronics designer Mark Hudson (of HIQ Sound) and I began the development of these phono stages.

Mark Hudson has been responsible for the design of many other phono stages, as well as numerous speakers, amplifiers, DAC’s and other electronics for many internationally known Hi-fi and professional audio manufactures.

A number of the products that we have collaborated on have been marketed under the names of HIQ Sound / Q series and then Iota. Since the early 1990’s I have also produced several different turntables
with power supplies, and arm modifications under the QT & Iota names.

The balanced phono stages were a development of an original idea aiming to produce a phono stage that could extract the highest quality of sound reproduction from vinyl records, with the minimum of noise and interference, whilst still being compatible with the widest range of equipment, and in order to achieve this they would operate in true differential balanced mode. The units were also designed through variable loading and gain to be compatible with any phono cartridge, whatever its output or loading requirements.

The very first units produced in the early 1990's were single box items, with a bespoke cartridge loading, provided for the customer’s chosen cartridge, on individual removable headers.

A revised MKII version some two years later offered the present day arrangement of “dial in” loading and gain switches that could be customer set, as well as revised casework and signal circuitry. It also incorporated a two box construction with the external power supply to further enhance the noise performance of this product. Over the next few months some owners, so delighted by the jump in performance offered by our products over their original equipment, asked if it would be possible to take the idea any further? The first “Signature version” products were designed and produced following this request.

The procedures adopted in the “Signature version” were to optimise the original circuit design, and hand-select all the components in the signal path. Unfortunately due to the laborious and time-consuming nature of this work the cost also increased. As a result it was expected that only a limited number of signature products would be ordered, however the original production batch, expected to sell over the next year was sold out in less than three weeks! All ordered by existing owners of the previous versions after hearing the improved signature product.

The original Iota range was created to incorporate three different phono stages at different performance levels, The Iota LCP 2, the Iota Median phono stage, with either the standard XL psu, or with an upgraded twin output power supply that supported both the Median phono stage and other Iota products at the same time, and finally the revised Iota Signature Reference phono stage, with its dedicated fully regulated, dual mono power supply, taking the original concept even further.

Unfortunately as a result of the significant design changes  between the standard Median and the Signature Reference, & because of  the added complexity it was impossible to provide a direct upgrade path from the Median to the Signature Reference, despite being a development of the original design, & using similar techniques. The Signature Reference differs in many key areas; e.g. different signal circuits with dual mono construction, and larger power supplies, with higher current delivery and extra stages of regulation, plus selected higher-grade, close tolerance selected components are used throughout the dual mono design.

However recent component developments and improvements  now mean that all existing customers, in all models, are able to benefit from the changes offered within the scope of this REV II 2016 upgrade.

After what is now more than 20 years of manufactutring  phono stages, we continue to offer the two most long standing prodcuts in full REV II 2016 form, the iota Median balanced  phono stage, the one box MM & MC unit with our basic X1 power supply. In adition to this we also produce our iota Signature Reference balanced phono stage. This is the two box MM & MC unit, with slected components and its own fully regulated, dual mono, seperate power supply in a second enclosure.

Why a Balanced Phono Stage?

The phono cartridge, either moving coil (MC), or moving magnet (MM) is a devise to “read” the groove of a vinyl record by responding to the modulations within the groove, and as a result of these vibrations,there by generate electrical energy in the form of fractional voltage signals. When these output signals are presented to the phono stage these are “decoded” or more accurately equalised to produce the sound we hear through the speakers.

As such all standard phono cartridges are in fact fundamentally balanced devises, despite this with most conventional phono stage applications turntables are used as a single ended source and terminated in RCA phono plugs. Why ..? We believe largely because of convenience as most other sources in a domestic hi-fi system were traditionally also terminated by phono plugs, and so it was considered the easy option, it certainly has nothing to do with extracting the best performance and lowest noise or immunity from interference!

As unfortunately the cartridge is also subject to a great many other outside forces acting upon it; not least of which are magnetic radiated fields produced by power supplies, and transformers and other equipment. This is evident by a fixed level of noise at either 50 or 60 Hz dependant upon your countries mains supply. Radio frequency interference in the form of “Ham radio” or “CB radio”, or even local taxi’s may also be heard to break through, as well as the signal we want to hear.

Our phono stage was developed to offer the best performance from the vinyl records without the usual problems of hum, noise, and radio frequency interference. Whilst still offering total flexibility in the choice of cartridge. As there is no such thing as a “standard” cartridge, in respect of either the recommended load or output, it is essential for a phono stage to be adaptable to allow the use of any cartridge currently available, as well as to ensure maximum performance.

The very wide variations in load and output which can be accommodated with this phono stage allows the user to fine tune precisely a specific cartridge and arm combination to a particular system. In fact it is even possible to allow for even minor deviations in specification, sometimes due to manufacturing tolerances, which can be displayed by an individual cartridge. This is not always possible with other phono stages.

The importance of providing the correct load or cartridge termination to ensure maximum performance can not be underestimated. It is essential for both the best performance and to avoid the obvious changes in tonal balance, which will be evident with incorrect loading. With incorrect loading applied to a cartridge it is also possible to induce miss tracking that will produce both a distorted sound, as well as permanent damage to precious vinyl!

Once again with most phono stages these effects are unavoidable, or at best only a compromise position will be offered, which by its very nature compromises the performance of the system, and may not extract all the information available from your vinyl collection. This is why our phono stages are in regular use in professional recording studio applications, where the transfer of rare or unique vinyl takes place directly to new digital master tapes. They are expressly chosen for this application as a result of the exceptional noise performance, tonal accuracy, and fidelity.

Balanced operation for both the input and output ensures the ideal means of handling the very vulnerable signal that vinyl reproduction represents. With this phono stage it is possible to use any practical length of suitable arm cable without experiencing interference problems. The same is also true of the output from the phono stage; true differential balanced operation allows even extreme lengths of cable to be run, once again without “pick up” or interference effecting the signal. This is possible due to “common mode rejection” which is a feature of true differential balanced operation. True balanced operation is only possible by providing not only the equalisation of the original signal but also generating the 180-degree opposite signal as well. Both of these signals must also be protected at all times by a very effective screen to further protect the signal. When the signal is fed into a suitable amplifier the two opposite signals are compared and any additional features (i.e. interference picked up by the cable) is rejected by the action of common mode rejection.

This is not possible with conventional single ended operation, as any interference will simply be added to the original signal and be amplified by your equipment, and you will then hear this in the form of hum or other unwanted noise, or by masking or simply failing to resolve information.

Unpacking & connecting the unit:

The equipment is supplied in two separate boxes; one will contain the phono stage and the other the power supply. The Iota nameplate may still have the protective film in place, unless your retailer has removed this, simply peel this film off to reveal the high gloss finish under the film.

With the exception of the X1 power supply (fitted with a captive cable) all other power supplies are supplied with a standard three pin IEC mains sockets. We also include a suitable mains supply cable with moulded plug. Please confirm the plug as supplied is suitable for your country and its mains voltage. Please also note this product must have the earth connected, & in the event of a fuse failure only replace fuses with the correct type, and value. See rear panel for description.

Because of the design and construction of our phono stage, the power supply will not produce interference with our equipment; therefore you may position the units either side by side or with the phono stage on top of the power supply which ever is most convenient.

First connect the dedicated Iota power supply cable between the units, this cable is fitted with a specific connector and rotary-locking ring. Insert the multi pin plug, five pin for Median, and eight pin for Signature Reference, please observe the correct position of the key slot on one side of the plug, and insert the plug correctly. With the plug fully inserted tighten the rotary locking ring, (finger tight ONLY) this will avoid accidental disconnection.

Now connect your tone arm cable to the phono stage. Usually the red plug or cable is the right hand channel. If your arm cable is fitted with an earth tag connect this to the grounding post on the rear of the phono stage. It is not normally necessary to further connect any ground wire to your pre / integrated amp from this post. Now connect the output cables from the phono stage to your pre /integrated amp.

Please ensure any connection to your existing equipment is made to a spare LINE level only connection, and NOT to any input that already has a phono stage on board, Potential damage to your equipment could result if misconnected. Once all connections have been made switch on your new phono stage and confirm the LED’s show power is available. The Iota equipment will benefit from an extended warm up, and can be left on permanently, unless you do not expect to use the equipment for an extended period, when it is best to switch off the unit and remove the mains cable.

Can I only use this Phono stage with balanced equipment?

No is the simple answer to this question, although originally designed as a true differential balanced unit, and in order to give its best results, the phono stage must be used in total balanced mode. However with either an unbalanced source or amplifier, excellent performance is possible with only simple adapters being required. Either fitted to the back panel of the equipment, or more simply by providing the appropriate balanced to single ended interconnecting cables. Please enquire with your retailer as to whether or not your existing equipment could be modified to take full advantage of balanced operation.

Setting the phono stage for cartridge load and output:

In order to maintain signal integrity & maximum protection from interference the adjustable DIL switches are located inside the metal casework of the unit.

When the unit is new the wrap around lid, which is designed to be an exact fit, can be slightly stiff to slide off, until the lid has been slid on and off a few times.

Remove the mains power supply plug from the back panel of the phono stage.

Place the unit on a smooth protective surface, & remove the screws that secure the units lid, these screws are accessible from the underside of the enclosure. Then put the unit on its side with the feet facing you,& with the front name plate to your left. Place your left hand on the top edge of the unit & while holding this top edge, push the phono stage out of the lid, towards the name plate,with your other hand, by pushing against the back panel. The lid will then easily slide off from the rear of the unit.

Establish the correct loading for your cartridge. E.g. Recommended load and output may be expressed as follows:  
MM = 47K (load) &  4mV (output) Refer to the manufactures specification sheet supplied with your cartridge for this information. Some experimentation with different values may however prove beneficial in many systems.
Locate the DIL switches and set the correct values, set according to the following table, put the switches into the ON position for the value required. The four switches for adjusting the load are coloured Red, and the two gain switches are Blue.

***Please note *** In order to maintain circuit symmetry for the Load switches, the numbers are reversed on two switches. Consequently these two red Load DIL switches have the numbers blanked out. Therefore to set the correct values,please observe the numbering on the following table, and set accordingly.
Put the switches into the ON position for the value required.

Switch layout:

*********  *********    *********   *********
* LOAD *   * LOAD *     * LOAD *   * LOAD *
*********   *********    *********   *********

*********          *********
* GAIN *           * GAIN *
*********          *********

Selecting the correct cartridge gain:

Cartridge Output………..……Gain switch setting
0.1 mV          1
0.125 mV     2
0.150 mV    3
0.200 mV   4
0.250 mV    5
0.300 mV    6
0.400 mV    7
0.500 mV    8
4 mV None ( MM )

Select the correct load for balanced sources see column A. For unbalanced (single ended) sources see column B

Cartridge load. Set Load switches :

                             Input……… A (balanced)       or        B (single ended)……………..switch no’s
                5 ohm                2.5 ohm = 1 2 3 4 5
    10 ohm                    5 ohm = 1 2
          15 ohm                 7.5 ohm = 4 5 7 8
20 ohm                  10 ohm = 1
30 ohm                  15 ohm = 4
40 ohm                  20 ohm = 5
   50 ohm                  25 ohm = 6 7
66 ohm                  33 ohm = 6
   100 ohm                50 ohm = 7 8
200 ohm              100 ohm = 7
        47 K  = None

Please contact your retailer for any further information, or special requirements.

What cable should connect the Balanced Phono Stage?

The original cable fitted to your arm may be constructed in a manner that would support re-termination in true balanced mode. Alternatively if the tone-arm on your turntable is fitted with the standard type SME/Jalco pattern five pin plug, the original cable can be replaced with our dedicated true balanced cable, terminated with a right angled SME plug at one end, and Neutrik XLR plugs at the other.

Due to the extra protection offered by true differential balanced operation, there is essentially no real practical limit to the maximum length of tone arm to phono stage cable. For example during development and testing we have used arm cables in excess of 25 metres without signal degradation!


 This equipment is covered by a full three-year parts and labour warranty, against fault workmanship or materials. This guarantee is offered on a return to manufacturer basis, and does not affect your statutory rights, within the terms of the sale of goods act.

The invoice, or some form of proof of purchase that will be provided by your retailer is your guarantee certificate for the equipment. Please keep a record of the equipment’s serial number, and the date of purchase .

Specification and measured performance