How does KLD UT 18 hand wired amp work
KLD UT18 1 8w hand wired amplifier based on VOX AC15, it has two channels controlling gain independently and can plug two guitar simultaneously. Two channels are: Lead and Normal. Below is sechmatic of UT18, the blue line represents the flow of signal of Normal channel, red line represents the flow of signal of Lead channel . |
Normal : V1B-V3-V4/5 The signal of Normal channel passes through classic gamma network comprised of a 1M (R39)grid leak resistor and an 47K(R36 ) effective grid-stopper resistance.Different with Marshall and Fender amp, the gride leak resistor R36 is 47K, not 68K as JCM 25 and Bassman 25, which let the more signal flows to grid of V1B. Lead: V1A-V2-V3-V4/5 The signal of Lead channel also passes through classic gamma network comprised of a 1M (R38)grid leak resistor and an 47K effective grid-stopper resistance.After passing through the first preamp V1A and VR1, it goes to the second preamp V2B, then to cathode follower V2A which supplies the tone stack with a low impedance signal. Tone stack In order to compensate guitar amp pickups which has strong low middle emphasis and little high frequency response - overall a very muddy and muffled sound, tone stack provids compensation for the natural sound of a pickup - the middle pot simply boosts the pickup's normal 'middley' sound. The treble and bass pots do the
opposite , boosting higher and lower frequency levels, leaving a notch in-between for middle freq tone. So with typical settings of a bit of bass, middle and treble, the overall tone equalization complements the natural pickup sound for a balanced response of lows, mids and highs. The Long Tail Pair (LTP) Phase Inverter (also called the cathode-coupled phase inverter) is the most popular phase inverter in guitar amplifiers due to its large output voltage swing and sweet overdrive tone. Unlike the non-amplifying cathodyne phase inverter used in many guitar amps the LTP phase inverter not only creates a dual mirror image signal stream but it also acts as a gain stage boosting the signal by about 1/4 of what two normal triode gain stages would. This added gain gives its output more voltage swing to drive big bottle power tubes to a fully distorted state. The LTP is a true differential amplifier and uses both halves of a dual triode tube (usually a 12AX7or 12AT7). Power amplifier:EL84 push-pull class AB The power amp stage of UT18 is almost same as Marshall TMB 18, only except the value of R24 little difference. R40 and R41(2K2) are grid stopper resistor which help tame oscillation of amp,and can reduce high freq tone in amp, but they need be within 10K. |