Although not strictly needed at chez vitalstates a preamp was deemed useful when taking amps to diy get-togethers. This was started as a low cost endeavour as it wasn’t considered a necessity, a real example of how initial ideas can be wide of the mark.
This is unashamed promotion for the B1 as it is fantastically easy to build and sounds fantastic as well (authors opinion).
The B1 is a passive pre-amp and therefore has no gain. It is however a buffer and provides good impedance matching between components. Many passive preamps seem to be criticised as dull and lifeless, but whether this dull and lifeless is caused by impedance matching issues can only be guessed at. You have my word for it, there is no dull and lifeless here. Full details and explanation, including circuits can be found on the Firstwatt site here.
In true DIY style the amp was built on matrix board. This is very easy as the circuit only consists of half a dozen components, but if in doubt ready made circuit boards can be bought from the Firstwatt site.
Again, in the interests of VFM, the B1 was housed in a modest plastic equipment box from Maplin. The box put the budget back by £7.50 but this is not considered to detract from the appearance. Indeed, the whole amplifier cost no more than £20 so its more than eligible to join the other offerings as representing good music for minimum outlay.
The B1 was recently run alongside a fairly expensive TVC based pre-amp at a DIY meeting and acquitted itself amazingly well. It was generally agreed the B1 held it’s own against such exotic company, but it was only when the fact was leaked that the B1 had a £2.50 Maplin pot that the gravity of the comparison became apparent.