Doc B. makes various vacuum tubed amp kits and one preamp kit, they all have odd names for audio equipment. His website is bottlehead.com there is a bulletin board there, and a free online magazine you can download. His Foreplay preamp kit is a dirt cheap($99), terrific sounding preamp. It uses a single 12AU7 tube per channel. While the stock Foreplay sounds very good, there are several cheap modifications you can do to make it sound even better.

There was an article in the 4-99 issue of Valve magazine that describes a few of the mods. You can buy the back issues on CD, and they are very reasonable- only $15 each. That's less than a music CD, and you get a full year of issues.

One of the more popular mods is the snubber, you can buy all the parts you need from Radio Shack for $2.18 plus tax. You need two 10 ohm 2 watt(or more) resistors and two .01uF 2KV capactiors. The resistors are 2 for $.99 and the caps are 2 for $1.19. The resistors are 10-Ohm 10 watt Wirewound Resistors (RS#271-132), the capacitors are .01uF 2kVDC Ceramic Disc Capacitors (RS#272-160). I bought 2 packs of each because they are so cheap, and matched the closest caps and resistors. There are instructions for assembly and a diagram in the Valve article. Some people swear by this upgrade, but I didn't hear that much of a difference. The only difference I heard was the background noise seemed quieter. But I just used the stock diodes (recifier) with the snubber, the differences may be more noticeable if you use faster diodes like UF4007s. It might be worthwhile to replace the stock diodes while you are adding the snubbers, because you will be desoldering half of them anyways. And by the way the UF4007s are really cheap, they are less than $.50 each.

Note: I have been informed that the Foreplay kits now uses the UF4007s as the stock diodes. Most of the Foreplays bought within the last year have been supplied with the new diodes.

I built an external regulated power supply for my Foreplay. For more info click here External PS . But I am still doing a few changes here and there.

Here's a page out of the Hammond Catalog. It's a useful guide for designing power supplies.