Tone King Gremlin - Tube Installation and Replacement; Choice of Tube Types; Installing Tubes

7
Notes on using the attenuator
In the 0db position, the attenuator is completely bypassed, and the speaker is
connected directly to the output transformer secondary, with no additional circuitry
touching the signal path.
Although the Ironman II attenuator does an excellent job of reducing output power
without changing the tone of the amp’s circuitry, there are other variables in play at
lower volume which do result in some apparent tone change. Here are a few factors
that you should be aware of -
Speaker breakup and compression is a big part of the tone and feel of the amp when
played at high volume. At low power settings, the speaker responds differently, and
does not break up and compress as it does at high power.
The ear’s natural response curve varies at different volume levels, which changes the
way you perceive sounds at different volume levels. Quieter sounds tend to give the
impression of having less bass content.
At lower volume, there is a tendency to hit the guitar strings harder and play more
aggressively than you would if the amp were tuned up very loud. It may take some time
to get used to maintaining your playing style at reduced volume.
4. Tube Installation and Replacement
Choice of Tube Types
I currently recommend the following tube types:
No. Function Brand/Type
V1 1
st
Gain Stage either Channel 1&2 TAD 12AX7A-C
V2 2
nd
Stage C.F. Channel 1&2, Driver Stage TAD 12AX7A-C
V3 Output Tube KT66
The tube brands shown above are our own preferences. You may want to use other
brands, to tailor the sound to your own tastes.
Alternate Tube Choices You May Want to Try
Reducing Gain: If you find the preamp too gainy, and you find that you’re setting the
volume controls down quite low to get sufficient clean headroom, you may want to try
swapping in a 5751, 12AT7, 12AY7 or even 12AU7 in the V1 position.
Installing Tubes
When installing tubes, you may find it helpful to lay the amp on its side on a table, and
shine a light directly into the back of the amp, to aid in locating the position of each
tube. Tubes must be installed in the correct orientation. The smaller, all-glass tubes
have a blank space in the ring of pins which must line up with the blank space in the
ring of tube pins in the tube socket, located on the chassis. The larger, bakelite-base
tubes have a small cylinder with an indexing key in the center of the ring of tube pins,
and this indexing key must match up with the corresponding slot in the socket on the
chassis.