Paradox Phono 70

I would like to introduce the "Paradox Phono 70"
This is 70 db of passive RIAA gain which will be enough for most any MC cartridge you want to use and it will certainly work for the Paradox Pulse R SMR at about 0.3mv.

Key features
-External power supply with voltage display, set at 18v can vary 17.5 to 18.5 volts
-external loading via RCA's and reusable screw down RCA's
-JFET low noise amplification
-Passive RIAA with only 1 tantalum resistor in the signal path along with 3 JFET's and 3 coupling capacitors
-70 decibels total of low noise gain
-All components are matched from the LSK170 JFET's through RIAA critical components
-Special Litz wire used for all signal and power supply paths
-Ultra high quality parts used throughout like Mundorf 10kuf M-Lytic one per channel
-No crappy switches to degrade the signal path
-Comes with many pairs of load resistors, additional loads upon request.

Like my other Pulse products the Phono 70 has a money back guarantee less any shipping (both to and from)  along with potential refurbishing costs for those that like to "kick" it around! If it returns in the same condition I sent it to you, all monies are refunded less shipping.  $2500- simply amazing.

See 70 owners manual page for more information.

Phono 70

This is how the standard Phono 70 is packaged.

When the 70 arrives it will be very well protected.
It comes well packed in a plastic case using pluck foam to safely hold and protect its content.
You will notice the white plastic wraps the 70 itself. Load resistors and their RCA's set on top. The power supply above. AC power cord to the left and the DC umbilacle to the right.
This is the base Phono 70 kit. Upgrades are available see store or give me a call to find out more.

How to load your Phono 70

See below for how to build extra loads from parts included in kit.

Kit has one assembled load set of 402 ohms.

The picture to the right is all the additional parts that come with a Phono 70 kit besides the power supply and 70 itself.
The power cable connects to the power supply and your AC outlet. 
The power supply display will read approximatly 18 volts, any voltage between 17.5 and 18.5 volts is proper. The power supply itself is set to 18v but your wall voltage vs. my voltage can make a difference of a couple of 10th's of a volt, do not be concerned. There is an adjustable pot inside that can be used to get 18v exactly but it is not important to the sound performance of the 70 so relax and enjoy on what ever the display reads.
Connect the umbilicale between the power supply and Phono 70 using the port on the back of each marked power.
Keep power supply far away from Phono 70 to avoid hum noise. If you have any hum noise check location of 70 with respects to other equipment with power supplies located to close.

Load resistor build
You will have extra RCA's with screw terminals. Grab a pair of values you would like to try and empty RCA's. Now you are ready to build.
Bend leads
It is as simple as the picture implies, bend the ends back on themselves (this gives more bite for the screw contact but is not necessary) then fold over. Loosen both set screws on the end and insert.
Phono 70 wiring kit with loading resistors. How to make more loads!
Each 70 comes with everything you need to get the most from your moving coil cartridge.
One pair of loading resistors is already assembled for you as a reference for you to copy when you build other values included in the kit.
Loading resistors go to ground and there is absolutely no sound improvement from using expensive resistors, precision metal film is all you need. We include 1% metal film resistors so each load value is precise.
Insert resistor
Now that the resistor is inside the screw terminal end tighten screws.
This will hold the values firmly in place.
Now insert RCA into the back panel of the 70 marked LOAD. This can be done on the fly while system is playing records.

Key components to make a truly great RIAA phono

RIAA phono


Passive RIAA vs Active/feedback RIAA

jRIAA equalization is a specification for the recording and playback of phonograph records, established by the Recording Industry Association of America (RIAA). 

The RIAA equalization curve was intended to operate as a de facto global industry standard for records since 1954. However, it is almost impossible to say when the change actually took place.
Taken from Wikipedia
The junction gate field-effect transistor (JFET) is the simplest type of field-effect transistor.
A JFET has a large input impedance (sometimes on the order of 10,000,000,000 ohms), which means that it has a negligible effect on external components or circuits connected to its gate.
Taken from Wikipedia

The LSK170 is a new and superior version of the 2sk170 which is acclaimed for it's low noise in voltage gain situations. 
Passive RIAA equalization uses only one additional part (resistor) in the signal path. With Active RIAA equalization additional resistors and capacitors are used in a feedback circuit which are then reintroduced back into the signal path.
Passive shunts the equalization signal to ground amplifying less record surface noise where as Active equalization then amplifies the signal and any noise along with it.
We believe Passive is the superior sonically but requires a circuit to loose 20db of GAIN.

Circuit Choices

The parts, signal path

Power supply and overall

When dealing with premier Phono cartridges they are of very low output (MC type) like 0.25mv and sometimes less. To amplify this signal a lot of GAIN is required. Lots of gain can mean lots of noise if the device is not exceptionally quiet that is why so many circuits in production today use JFET Operational Amplifiers (OP Amps) a high input impedance and quality gain. Tubes are ok and do a great job of voltage gain but the types that sound best cost lots of money and are normally limited to less than 18db of gain per stage requiring 2 tubes per channel just for 30 or 40db of RIAA gain.
Often tubes are paired with SUT's (Step Up Transformers) to accomplish the necessary overall gain as using another tube will lead to unacceptable noise in the system. Needless to say SUT's are very limited overall in their gain and going through a mile of wire is not my idea of high speed. To get the most out of any MC cartridge a proper damping must be applied see page "MC Cartridge Loading 101".
Paradox use 3 discreet JFETS which each have 30db of gain. After loosing 20db to Passive RIAA we are left with 70db and thus the name "Phono 70".

For Paradox it is all about life like sound. So the parts used are of the upmost importance.
Parts like op amps and high gain tubes (like the 12AX7 most likely the worst sounding commonly used tube out there) are NOT acceptable. Using 3 quality tubes with two stages each is a better choice but too noisy and expensive to operate not to mention the constant sound change as they wear out.
Enter the discrete  JFET (op amp JFET uses nearly 100 parts for their circuit) one part for the signal and 30db of ultra quiet low noise gain, thank you.
Coupling capacitors always so critical to the overall sound are not some plastic film with its credit card plastic sound imparted to everything. Try scraping a credit card against a stubbly beard or your arm (many other surfaces are fine to use also for the test) or any other surface and take note of the sound. All plastic caps impart that sound into the system and by plastic I am talking about poly, styreen, mylar, teflon etc. Now some plastics do sound way better than others (teflon) but they are still still plastic.
We use PIO which though not perfect sound more life like as a general rule, they are similar to the PIO's used in Shindo products. Our lone resistor in the signal path is tantalum, sonic-ally the best available. Even the signal in/out and the power wire is a high quality Litz copper conductor.

The power supply parts are equally as important as the signal path parts.
The regulated outboard power supply keeps its magnetic stray field far away from the delicate signal and JFETS. The umbilical cord used to connect the two is the same high quality copper Litz conductor as used in the signal path. Large isolation inductors along with a styreen bypass for the Mundorf MLytic (10,000uf per channel) capacitors are used per channel for isolation. This isolation and speed continues with a styreen capacitor at each component/JFET.
Listed here last but perhaps the most important is our ultra high quality circuit board. They are designed from scratch and not by computer, although built in a computer, for the shortest signal path and most flowing circuit. Like a river, yes it is our river technology, we avoid the normal CAD problems and 90 degree connections you get when the computer builds you board. Using a 0.125" thick board material along with double thick copper and plate through holes it will not resonate like the others. The signal path is also extremely short 2" less the components the signal has to travel through so much for point to point wiring used in the best tubes, what do you think about a foot and a half of wire maybe more?
Overall when everything is added up you simply have one of the finest RIAA Phono amplifiers built on the planet earth.