A Studio Preamplifier

The first was interested in a flexible preamp for use with a high-end acoustic guitar with piezo-electric bridge pickup, and the second wanted a preamp for use with a guitar emulator, to provide add someof the warmth that vacuum valves can provide. Both of these requirements, and very probably many more, can be met using a variation on The Universal Tube
A Studio Preamplifier - schematic

Preamp design. I have, in fact, used my RA-100 Reference Amplifier for precisely such purposes; the combination of clean, noise-free amplification and non-obtrusive tone controls makes an ideal preamplifier for musical instruments. However, if we`re looking for a dedicated, standalone preamplifier (perhaps assembled on a rack-mountable panel), there are a few changes we can implement to the universal preamp design in order to improve and customise it for musical instrument applications. As of this writing, I have not actually built this variant on the Universal Preamp design, and it`s unlikely that I`ll do so in the foreseeable future. I will therefore be grateful for any reports, and would be happy to help out in the relatively unlikely event that there are significant bugs in the design implementation as presented here. This is the main reason why I put this project into the "advanced" category; other than the fact that there may be tweaks required, there is nothing particularly difficult about the design or its construction. Here is the schematic of the modified preamplifier circuit, redrawn from the original to fit better into the web format. An enlarged and dithered version, suitable for laser-printing at 300 dpi (final size 7-1/2" x 10") is available by right-clicking / Save As. here. This is essentially a revisited version of the tone control preamp section of the RA-100, so you might want to have a look at parts of...

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