Randy G.
2008-09-23 17:34:28 UTC
I have been playing at a local open mic blues jam for almost a year
now, and drop into two others when time allows. I actually played 4
different jams in one week earlier in the month. I thought I would
share a bit of what I have picked up, all FWIW. Much of this is old
hat for experienced musicians, but others may make use of it.
My first live rig was a Bottle 'O Blues microphone and a Roland Cube
60 amplifier. While it was fairly affordable and easy to tote, the
sound was not that great. The solid state amp offered no over-driven
sound and the BOB mic has a flat sound with little to offer at either
end of the spectrum. Still, it was a nice rig to start with. I ended
up with that amp on the recommendation of a friend to whom I later
sold the amp.
I decided to go with a tube amp, and almost bought a Fender Blues
tweed reissue, but the more I read and the couple of times I tried it
at the local music store the less I liked it. In retrospect there are
things I could have changed, but the particle board cabinet did not
thrill me and with three cats in the house, the Tweed would not last.
After some serious shopping and comparison I ended up with a Genz Benz
Black Pearl 30 (BP-30). Among other things, I choose it because it has
a full tube signal path (including the rectifier), a 13 Ply Baltic
birch plywood cabinet, Eminence Red Coat speaker, can be switched from
2 to 4 output tubes as well as from pentode to triode mode (both with
the flick of a switch), three-year warranty, it uses mil spec circuit
board material, and the controls have useful ranges and small
adjustments make a difference... Anyway....
After I got the amp I bought a Cherub microphone. These are a modified
lapel style mic made locally, specifically for harmonica use. A little
box sits on the belt where the mic cable connects, and a fixed cable
goes to the mic which is designed to sit between two fingers of your
choice. You can easily run the cable through a long-sleeved shirt and
the system becomes almost invisible. I plan to go wireless in the
future which would eliminate the cable from me to the amp, and it
would look magical with this mic....
The problem at this point was that, like with most amplifiers designed
to work with guitar, the mic was too hot for the amp. I could barely
turn up the input level, and the drive was almost unusable. I was
constantly fighting feedback and had real problems cutting through the
mix. To solve that I did some experimentation by fabricating an input
attenuator using some resistors and a 2.5 MEG pot. I then added a 500
ohm pot in line so that they would work in tandem- one coarse and one
fine adjustment. That helped a lot, and I was discussing the situation
with a more knowledgeable musician who said I would change the preamp
tunes. Hmmm....
I did some research and learned a bit about tubes, then called Genz
Benz. Another reason I chose GB was the great support they offer.
After speaking to their technician I learned which tubes to change.
The amp comes with a 12AX7 as the Phase Splitter, and two additional
12AX7s in the second and third gain stage in the input section. He
told me to leave the phase splitter unchanged or I would not get the
full 30 watts out of the amp, but the other two input tubes could be
changed for different response. I did a Google on tubes, and as a
point of reference I found the following information about the tubes:
TUBE PERCENT GAIN
12AX7/7025/CV4004 100
5751 70
12AT7 60
12AZ7 60
5965 47
6072/12AY7 44
6829 39
12AV7 38-40
12AU7/6189/5814 17-20
The numbers vary a bit depending on the source of the information, but
the relative levels give a good idea as to what you can do. AFAIK, all
these tubes are interchangeable.
Not knowing which way or how far to go, I ordered two 12AT7s and one
12AU7 (GT Golds). The two 12AX7s worked well and there was a lot of
improvement. I then removed the 12AT7 in the 2nd gain stage position
and replaced it with the 12AU7 and it got even better.
I have played one open mic jam with it since I replaced the tubes and
it was like a different harp player showed up. I could easily hear
myself over the rest of the group. On one tune I was able to turn the
gain "Boost" level up and it sounded delightfully crunchy when I
pushed it, and on another tune I turned up the reverb (which never
sounded very good before) and one of the guitar players even turned to
me and gave me a "that was cool" nod at the end of one of my solos. On
one solo I decided that it was time for the crowd to REALLY hear me,
so I turned up the mic just a bit, and when I hit the first note I saw
just about every head on the dance floor turn to the stage (shades of
Paul Butterfield)!
So the change improved the headroom in the amp. Previously the chords
were muddied and distorted but now come through far more clearly. I
can use more drive and get the crunch I was originally looking for
that was unattainable with the solid state amp. And previously any
attempt at volume to fill the room resulted in feedback; now, with the
additional dynamic range and usable volume, when I crank it I can hear
my sound bounce off the far wall of the club where I play! It's
awesome!
So I have ordered another 12AU7 which is on the way so that both the
2nd and 3rd input stages have 12Au7s to see how that works.
As I stated at the top, most of this will be old news for the
experienced musicians here, but for those starting out and wondering
why "2" is as high as you can set the input volume on an amp, check
the input stage tubes there is probably more in the amp than it would
first appear.
Randy G.
http://www.EspressoMyEspresso.com
now, and drop into two others when time allows. I actually played 4
different jams in one week earlier in the month. I thought I would
share a bit of what I have picked up, all FWIW. Much of this is old
hat for experienced musicians, but others may make use of it.
My first live rig was a Bottle 'O Blues microphone and a Roland Cube
60 amplifier. While it was fairly affordable and easy to tote, the
sound was not that great. The solid state amp offered no over-driven
sound and the BOB mic has a flat sound with little to offer at either
end of the spectrum. Still, it was a nice rig to start with. I ended
up with that amp on the recommendation of a friend to whom I later
sold the amp.
I decided to go with a tube amp, and almost bought a Fender Blues
tweed reissue, but the more I read and the couple of times I tried it
at the local music store the less I liked it. In retrospect there are
things I could have changed, but the particle board cabinet did not
thrill me and with three cats in the house, the Tweed would not last.
After some serious shopping and comparison I ended up with a Genz Benz
Black Pearl 30 (BP-30). Among other things, I choose it because it has
a full tube signal path (including the rectifier), a 13 Ply Baltic
birch plywood cabinet, Eminence Red Coat speaker, can be switched from
2 to 4 output tubes as well as from pentode to triode mode (both with
the flick of a switch), three-year warranty, it uses mil spec circuit
board material, and the controls have useful ranges and small
adjustments make a difference... Anyway....
After I got the amp I bought a Cherub microphone. These are a modified
lapel style mic made locally, specifically for harmonica use. A little
box sits on the belt where the mic cable connects, and a fixed cable
goes to the mic which is designed to sit between two fingers of your
choice. You can easily run the cable through a long-sleeved shirt and
the system becomes almost invisible. I plan to go wireless in the
future which would eliminate the cable from me to the amp, and it
would look magical with this mic....
The problem at this point was that, like with most amplifiers designed
to work with guitar, the mic was too hot for the amp. I could barely
turn up the input level, and the drive was almost unusable. I was
constantly fighting feedback and had real problems cutting through the
mix. To solve that I did some experimentation by fabricating an input
attenuator using some resistors and a 2.5 MEG pot. I then added a 500
ohm pot in line so that they would work in tandem- one coarse and one
fine adjustment. That helped a lot, and I was discussing the situation
with a more knowledgeable musician who said I would change the preamp
tunes. Hmmm....
I did some research and learned a bit about tubes, then called Genz
Benz. Another reason I chose GB was the great support they offer.
After speaking to their technician I learned which tubes to change.
The amp comes with a 12AX7 as the Phase Splitter, and two additional
12AX7s in the second and third gain stage in the input section. He
told me to leave the phase splitter unchanged or I would not get the
full 30 watts out of the amp, but the other two input tubes could be
changed for different response. I did a Google on tubes, and as a
point of reference I found the following information about the tubes:
TUBE PERCENT GAIN
12AX7/7025/CV4004 100
5751 70
12AT7 60
12AZ7 60
5965 47
6072/12AY7 44
6829 39
12AV7 38-40
12AU7/6189/5814 17-20
The numbers vary a bit depending on the source of the information, but
the relative levels give a good idea as to what you can do. AFAIK, all
these tubes are interchangeable.
Not knowing which way or how far to go, I ordered two 12AT7s and one
12AU7 (GT Golds). The two 12AX7s worked well and there was a lot of
improvement. I then removed the 12AT7 in the 2nd gain stage position
and replaced it with the 12AU7 and it got even better.
I have played one open mic jam with it since I replaced the tubes and
it was like a different harp player showed up. I could easily hear
myself over the rest of the group. On one tune I was able to turn the
gain "Boost" level up and it sounded delightfully crunchy when I
pushed it, and on another tune I turned up the reverb (which never
sounded very good before) and one of the guitar players even turned to
me and gave me a "that was cool" nod at the end of one of my solos. On
one solo I decided that it was time for the crowd to REALLY hear me,
so I turned up the mic just a bit, and when I hit the first note I saw
just about every head on the dance floor turn to the stage (shades of
Paul Butterfield)!
So the change improved the headroom in the amp. Previously the chords
were muddied and distorted but now come through far more clearly. I
can use more drive and get the crunch I was originally looking for
that was unattainable with the solid state amp. And previously any
attempt at volume to fill the room resulted in feedback; now, with the
additional dynamic range and usable volume, when I crank it I can hear
my sound bounce off the far wall of the club where I play! It's
awesome!
So I have ordered another 12AU7 which is on the way so that both the
2nd and 3rd input stages have 12Au7s to see how that works.
As I stated at the top, most of this will be old news for the
experienced musicians here, but for those starting out and wondering
why "2" is as high as you can set the input volume on an amp, check
the input stage tubes there is probably more in the amp than it would
first appear.
Randy G.
http://www.EspressoMyEspresso.com