The Foreplay line preamp from
is a wonderful thing. This was my second DIY project. I first built a
stock Foreplay with gold RCA jacks, some Kimber wire that I had around and
Cardas solder. The kit was very easy to build - I had no problems at all.
It sounds very good too.
One thing about the Foreplay is that there are many tweaks and
upgrades. My second Foreplay was build in a custom chassis with
the controls on the front and the jacks in the back. I left the
tubes and power transformer on the top plate. Over the following
7 month period, I tried out many upgrades. After that, I decided
to do a rebuild that contained my favorite tweaks.
- Tape in/out
- EIC female connector for power cord
- Doc's 20.5 AWG magnet wire
- Reverse recovery spike filter (VoltSecond's version)
- Grayhill selector switch
- Single-point-ground (SPG)
- Auricap coupling capacitors
- Ceramic tube sockets with gold pins
- Anticipation - Camille Constant Current Source (C4S)
Sweet Whispers stepped attenuators wired in shunt mode
using Lorlin (MSR#105-13571) rotary switches (but don't
buy them as they suck).
- RCA Clear Tops - 12AU7 tubes
Braided power cord with 12 AGW solid core copper wire and
Hubbell plug and EIC male end
Buddha's choke regulated power supply (the "CMC mod")
will Solen capacitors and TDK CMC.
pseudo dual mono power supply
- Lots of heat shrink to help shield everything
- Grid stop resistors (I don't know how much these help anymore)
Layout is very important. If you design a custom chassis, do it
on paper until you get it right. Make sure that you can take it
apart such that you can work on it later (this will definitely
come up). In other words, don't copy my design here. It was easy to
put together, but it is a pain in the arse to take apart.
The Lorlin switches that I used for my attenuators are
sealed and have a stop setting (so you can't go from 0 to 11 in one
click). Something I learned was don't spray contact cleaner
on/in your attenuators. However, denatured alcohol works well.
You want to keep them as clean as possible.
Though direct wiring of the power cord may have sonic improvements,
the braided power cord is so stiff that it can be quite a hassle to
pull out your Foreplay to work on. The EIC connector makes life
easier. You can also easily compare different power cords.
I mounted the CMC filter on perf board with connecting lugs (wires in
my case) at each end. The board is mounted on the side instead of
the top plate to help reduce vibration and EMF.
If you use a single point ground (SPG), heed VoltSecond's advice
(on his psuedo dual mono power supply page) on separate grounds
for each channel. Each channel is connected to chassis ground
via a 10 ohm resistor. I tried hooking it up both with and
without the L/R grounds and resistors, and the L/R grounds and
resistors was much quieter.