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Coffman Labs, LLC www.coffmanlabs.com
RECOMMENDATIONS
The G1-A will burn in over the first week or so, becoming more
mellifluous in the process. After that, you should not notice much
change.
We recommend that you play with various tubes to match your
personal taste and system. To assist you, here are some points to
consider, in order of importance:
1. 12AU7s provide the highest level of tube customization in
the phono stage. 1960's and 1970's USA production
12AU7s are a large improvement over current production
tubes. However, vintage Euro or old Black-Plate USA tubes
are most highly recommended.
2. 5AR4s can be changed for Euro GZ-34s to very good effect.
The main difference will be in improved tightness of the
bass.
3. 12AX7 phono stage, like the 12AU7, works very well with
vintage Black-Plate USA or Euro tubes.
4. 5687s are the last tube we recommend changing in your
"tube rolling" endeavors. TungSol Black-Plates are
considered premium by many, but the RCA Bronze-Plates
are also very good—though they tend to be a bit more
sensitive. Raytheon tubes are also very linear. The best
5687 tubes are the Sylvania Gold Brand, gold pin—however
these are very rare and also slightly microphonic.
Replacement tubes can be bought from a number of reputable tube
dealers, all of which can be found online. Coffman Labs has a large
stock of vintage Euro and USA tubes as well, and you may contact us
with any tube-related questions. We specifically screen all of our
appropriate tube types for use in the G1-A, so you may buy from us
with confidence at www.coffmanlabs.com.
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