What is the EP-PRE
The EP-PRE is a JFET preamplifier that is based on the preamp section of the Echoplex® EP-3® tape echo unit. It will deliver a few db of boost, but I don’t consider it as a boost.
Words such as Enhance, Fatten and Enrich all cover the effect that the EP-PRE has on your tone, but I have yet to find a word that really captures the magic of this amazing little circuit. A friend who has one of the prototypes calls it a “Tone Polisher”.
My own feeling is that it creates a “focus” in my tone and helps me to play with more confidence.
I built my first EP-PRE prototype while recovering from heart surgery in 2007, in response to a thread on The Gear Page. A couple of forum members suggested that the preamp section of the Echoplex® EP-3® should be built into a pedal. I took a look at the schematic, and couldn’t really see, at a glance, how such a simple circuit could affect tone, however I was curious and built my version of the preamp. To my surprise, it fattened my tone and sounded great. At this point, I began to seriously analyze the behavior of the circuit, and found that, apart from a small amount of top and bottom cut, the circuit had a non-linear phase response. I believe that this phase response is the secret of the magic tone.
I enjoyed using the prototype and didn’t really consider building the pedal for sale, because my other pedals are my own original designs. Before long, word got out and I began to receive enquiries from guitar players who wanted to buy this pedal. I designed a PCB, and the EP-PRE is now in production.
The Volume control is the equivalent of Echo Volume in the tape echo unit, wired in reverse, because there is no echo in the EP-PRE. Because I insisted on keeping the circuit interaction the same as in the original tape echo unit, the Volume control works for only about half of its travel. I considered replacing it with a lower value pot and a fixed resistor, but found that, as you wind it further round, while it doesn’t change the volume, it makes a subtle difference to the tone.
We have these switches custom made to our specification, which includes gold contacts for maximum reliability when switching very low current in pedals.
For best compatibility with either Lead-Tin or Lead-Free solder, the PCB has gold plated pads. The use of SMDs for most of the components keeps the PCB small, and there is a full ground plane on one side of the PCB, to minimise induced noise.
The EP-PRE pedal operates from a 9V to 12V DC, Centre Negative power supply that has become the standard for most pedals.
The original EP-3® preamp operates from a zener regulated supply of about 20 Volts DC. The characteristics of the power supply are significant to the operation to the circuit. It just doesn’t work properly on 9 Volts, so the EP-PRE has a Charge-Pump power supply that converts the 9 Volts to more than 17 Volts, and 12 Volts to just over 23V . A Charge-Pump came closer to recreating the dynamics of the power supply in the EP-3® than I could achieve with an external 18 Volt supply.
The price of the EP-PRE is USD $189 including Air Mail postage. If you are not from the USA, please contact us to ask if we can accept your local currency, and for postage rates. We use PayPal for payment. As we are based in Australia, we can accept deposits in Australian Dollars from Australian customers only.
Dave Leslie from 90s Aussie legend band Baby Animals sent me some clips of the EP PRE with his Aussie Aussie made Grubisa Merlin guitar and Reynolds Valveart amp.Â You can listen to them on the Sound Clips Page, where you will also find links to some excellent clips by Testlotsatone and paulscape
If you are interested in ordering an EP-PRE, please use the “Contact Us” page to send an email. When you email, please let us know what part of the world you are from.
® Echoplex and EP-3 are registered trademarks of Dunlop Manufacturing.