Cool looking SE 6T9 UL amp

The 6T9 tube has both a triode and a pentode in the one small compact glass envelope. The amp uses Spare Time Gizmo cct. brds. and is in SE UL mode. This is the second of the two amps I built. The first was on a Teflon $7 baking pan chassis. Edcor XSE15-8-5K OPTs are under the lid and help produce a frequency response from 20hz to 20khz (-3db points).

The sound stage produced is extremely wide and deep and when coupled with a pair of Fostex single driver 94db efficient speakers produces the most sumptuous music. Especially classical and voice. The paint used is Epoxy enamel and though the two coats take eight days to dry the finish is very tough.

The amp has no audible hum at 12" from the speakers and produces very sweet mids with excellent detail. At no time does the amp not sound musical and I would recommend the build to anyone wanting a very inexpensive and exceptional sounding amplifier.

SE 6T9 UL amp curcuit board

This Spare Time Gizmo cct. brd. only cost $AU16 and is double sided, screen printed and solder masked. I used it in both 6T9 amps. The components are quality without getting into exotica were available form my local electronics hobby shop. The coupling and input caps I increased to .22uf metallised polypropylene types and the final PS cap I doubled in capacity. Snubbing was added to the diodes and the PS caps. Edcor SE OPTs (XSE15-8-5K) were used and the UL tap wired to pin 10 of the valve sockets. The screen grid resistor left out. The power tranny is Hammond and I went slightly over-size. This is an excellent sounding amp and I would recommend it to any builder of audio gear wanting to try valve amp construction.

SE 6T9 UL amp on a teflon baking pan

This delightful little amp is incredibly musical though it only produces 4.5W of power. When coupled with some very efficient speakers (e.g. Fostex FE167E 6.5" drivers) more than sufficient audio levels are easily obtained. The sound stage is huge and particularly wide. This was the first of these amps I built. The second is also posted on this blog and was purchased by an iPod only user.

Portable high quality mini-recording setup

The setup seen above provides a portable recording facility with direct to digital facilities. The preamp (red lid) is the ESP two transistor low noise preamp and is simple to make and really is very low noise. No hiss or other audio artifacts can be heard at all in even quiet recordings. Mine was built over-size to allow a 12V battery pack to be included under the bonnet. Gain is limited though.

Low noise mic preamp

After purchasing a couple of Berhinger studio mics and valve preamps and doing some recordings of live choirs etc. I decided I wanted something more portable. I bought a Sony ECM-MS957 but required a portable preamp. This is the ESP low noise two transistor preamp. Though it is quite large it has a 12V battery supply and uses large 10uf polypropylene caps throughout. All silver wire and quality components were used. Two attenuators allow separate channel level control. I use a Cowon Audio6 mp3 player with a line input connection for recording direct to digital at 128kps. The whole mini-recording desk runs on batteries and even after four hours of recording barely effected battery level.