The Koch KC50 'Harmonica'
This is my Koch amp: a combo with a 12 inch Celestion
speaker. It is not a guitar amp but an amp especially designed for the
harmonica. It's a Dutch brand. The amp has been taken out of
production, becaus the market for harp amps is small, at least in the
Netherlands. Unlike guitar players, harp players mostly buy old,
relatively inexpensive amps. The Koch has a clean channel and an
overdrive channel. The overdive has to options, with each a different
kind of distortion: 'gain' (first stage of the overdrive channel) and
'drive' (second stage of the overdrive channel). The amp also has a
good reverb (leftmost knob). To controle feedback the amp has a number
of possibilities to cut of the high tones, by means of press-buttons.
Futhermore there is a bassboost to increase the lower bassrange of the
overdrive channel. With a pentode-triode switch the amp can be played
at 25 and at 50 Watt power. The speaker is easy to disconnect. I
sometimes do this to connect the amp with the "3x10 inch and a tweeter"
box I normally
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use with my Bassman100 silverface amp. This gives a different and also
very good sound. The clean and the overdrive channel have different
inputs and each has a different input for low and high impedance mics.
The clean and overdrive channel are automatically linked when only one
channel is plugged in. Switching between channels is possible with a
manual switch and a footswitch. When both channels are plugged in, the
link disconects and the player can switch microphones while playing.
This is only a part of the possibilities of this amp. If anyone want to
know more, pleas ask.
As noted above, the amp was especially designed for harp playing.
Nevertheless, a little customization was nessesary. The two pre-amp
tubes where both 12AX7 tubes. When using much gain or drive, the volume
knob couln't be set higher than about 2 or 3. I switched the tubes for
a 12AY7 (first one) and a 12AT7 (second one). Now I can screw up the
volume knob to about 6-9, depending on the amount of gain and/or drive,
which gives me much more possibilities to create an optimal sound. I
also have a couple of 12AU7 tubes. So I can experiment a little bit
further. But for now, I am very satified with the sound.
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