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APRIL 2008
I have never actually enjoyed vinyl LP playback, even when it was essentially
the only medium available. I find it hard to listen beyond the surface noise
and enjoy the music. I wish it were otherwise, but the crackling, popping,
crunching, and swishing noises are just too distracting.
Even if vinyl could be played back noiselessly, I am still not sure that I would
want to deal with it. I remember too well how any problem with the sound
of my LP system produced a laundry list of possible causes. Is the cartridge
tracking right? Do I have the turntable level enough? How about the
azimuth and the anti-skating? Do they need adjusting? Is the stylus worn
or dirty? Do I need better phono leads? Is my preamp loading the
cartridge properly? Sure it sounds good at 47K Ohms, but would it sound
better at, say, 44,100 Ohms?
Vinyl is just not the medium for an obsessive like me. You might well ask,
then, why, having this sort of personality, would I use vacuum tubes in my
listening systems—a technology that generates a lot of heat and starts
wearing out the second you put it to use?
It is a question I have been asking myself lately.
I recently checked the bias settings on the VTL 50-50’s output tubes. Each
tube was off by a noticeable amount. Since it has not been very long since
they were last biased, I decided to pull the 5881s I was using and install
some slightly used 6L6s that were gathering dust. With the newer tubes
and the bias set properly, there was a worthwhile sonic improvement. This
was good in that the living room system definitely sounded better but bad
in that I now felt that I had to upgrade the rest of the tubes in the amp and
preamp. This is the obsessive part that I referred to.
I got on eBay and bought eight JJ Tesla 12AX7s, which are used in the
Audio Experience preamp, and also a set of five Philips 12AT7s to replace
the input tubes in the VTL. I always buy more tubes than I need because I
always seem to get at least one bad tube. Call me pessimistic but that has
been the pattern.
The JJs showed up first and I spent Easter Sunday afternoon testing them
while I watched the Malaysian Grand Prix. The Grand Prix was by far the
more enjoyable part of the day.
I got such mixed results from the JJ tubes that I really had no idea of what
to make of them. Out of eight tubes, I could not find three that tested
close enough to each other to use them in the preamp.
I have no idea what to do in this sort of situation. So I ended up sending
the JJ tubes back. The seller was really great about everything and sent an
almost instantaneous refund. Whether that was because he is a just a
good businessman or whether he just preferred to be rid of me, I can’t say.
The 12AT7s showed up on the following Tuesday. These are Philips JAN
NOS (Joint Army Navy, New Old Stock) tubes. I have used them in the VTL
before and I like them.
My Heathkit TT-1A tube tester says a good 12AT7 should test around
1800. Here are the test results I got:
1) 1650/1400
2) 1650/>3000 (off the meter scale)
3) 2250/>3000 (off the meter scale)
4) 1700/1950
5) 1800/2350
I found myself once again looking at test results that I do not know how to
interpret.
Is Tube one bad? What would cause Tubes 2 and 3 to test so high on one
side? Are they bad? Will they work properly in the amp or could that much
gain cause a problem? Will the difference between the sides of Tube 5 be an
issue? I wish I knew the answers.
Rather than send these tubes back as well (the return postage was getting
out of hand), I decided to put them in the VTL amp and just see how they
sounded. I paired Tubes 1 with 5 and Tubes 2 with 4. My assumption
being that this would tend to even out their differences. I really have no
idea if this is the case or not. I do not know which side of these tubes is
actually being used by the amp or whether only one or both sides are being
used. I do not have a schematic for the VTL and probably could not follow
it if I did.
I put the tubes in and turned the VTL on by itself—and immediately got a
loud racket from the right speaker. Another bad tube.
For the next few moments, I seriously considered switching to solid state
amplification.
I switched Tube 2 with the unused Tube 3. I got lucky. I found the bad
tube on the first try. The amp quieted right down. (Considering its age,
the VTL actually runs pretty quietly. I can only hear some quite low level
hum if I am closer than a foot from the Quad 21L 2’s woofer.)
I turned everything else on and warmed up the system using the Isotek
burn-in CD. Then I did some listening. The soundstage was wide; the bass
sounded and felt deep, the high-end was clean and quiet. Vocals were
beautifully centered in the middle.
The system sounded great, despite having crappy measuring tubes in it.
There are two things about this tube testing experience that bother me.
First, testing the tubes did nothing to identify Tube 2, the noisy tube.
There was no indication that anything was wrong with it.
Second, the system sounds great so the inconsistent results produced by
the testing do not really seem to matter, anyway.
I have been asking myself is there any point to even testing tubes? I
expected that having a quality tube tester would make things simple and
give me clear-cut results. This has not been the case; I get
incomprehensible results that only lead to worries and concerns.
Frankly, I would like someone else to do the worrying and just sell me tubes
that will work in my equipment.
It is possible to purchase matched pairs and quads of just about every type
of output tube. So why isn’t someone selling closely matched six, eight, or
ten-packs of preamp tubes as well? I would happily pay a (reasonable)
premium for this service. If I could get six tubes with no duds, I would be
far happier than I am now buying eight random tubes because I know I will
get at least one outright bad one. It seems to me there is a marketing
opportunity going begging here.
If testing tubes has taught me anything, it is that the less I know about
how my tubes measure, the happier I can live with them. If they sound
good, then they are good. Ignorance, at least where tube measurements
are concerned, can be bliss.
I think the Heathkit TT-1A will be looking for a new home.
Kent Johnson
April 2, 2008
I have never actually enjoyed vinyl LP playback, even when it was essentially
the only medium available. I find it hard to listen beyond the surface noise
and enjoy the music. I wish it were otherwise, but the crackling, popping,
crunching, and swishing noises are just too distracting.
Even if vinyl could be played back noiselessly, I am still not sure that I would
want to deal with it. I remember too well how any problem with the sound
of my LP system produced a laundry list of possible causes. Is the cartridge
tracking right? Do I have the turntable level enough? How about the
azimuth and the anti-skating? Do they need adjusting? Is the stylus worn
or dirty? Do I need better phono leads? Is my preamp loading the
cartridge properly? Sure it sounds good at 47K Ohms, but would it sound
better at, say, 44,100 Ohms?
Vinyl is just not the medium for an obsessive like me. You might well ask,
then, why, having this sort of personality, would I use vacuum tubes in my
listening systems—a technology that generates a lot of heat and starts
wearing out the second you put it to use?
It is a question I have been asking myself lately.
I recently checked the bias settings on the VTL 50-50’s output tubes. Each
tube was off by a noticeable amount. Since it has not been very long since
they were last biased, I decided to pull the 5881s I was using and install
some slightly used 6L6s that were gathering dust. With the newer tubes
and the bias set properly, there was a worthwhile sonic improvement. This
was good in that the living room system definitely sounded better but bad
in that I now felt that I had to upgrade the rest of the tubes in the amp and
preamp. This is the obsessive part that I referred to.
I got on eBay and bought eight JJ Tesla 12AX7s, which are used in the
Audio Experience preamp, and also a set of five Philips 12AT7s to replace
the input tubes in the VTL. I always buy more tubes than I need because I
always seem to get at least one bad tube. Call me pessimistic but that has
been the pattern.
The JJs showed up first and I spent Easter Sunday afternoon testing them
while I watched the Malaysian Grand Prix. The Grand Prix was by far the
more enjoyable part of the day.
I got such mixed results from the JJ tubes that I really had no idea of what
to make of them. Out of eight tubes, I could not find three that tested
close enough to each other to use them in the preamp.
I have no idea what to do in this sort of situation. So I ended up sending
the JJ tubes back. The seller was really great about everything and sent an
almost instantaneous refund. Whether that was because he is a just a
good businessman or whether he just preferred to be rid of me, I can’t say.
The 12AT7s showed up on the following Tuesday. These are Philips JAN
NOS (Joint Army Navy, New Old Stock) tubes. I have used them in the VTL
before and I like them.
My Heathkit TT-1A tube tester says a good 12AT7 should test around
1800. Here are the test results I got:
1) 1650/1400
2) 1650/>3000 (off the meter scale)
3) 2250/>3000 (off the meter scale)
4) 1700/1950
5) 1800/2350
I found myself once again looking at test results that I do not know how to
interpret.
Is Tube one bad? What would cause Tubes 2 and 3 to test so high on one
side? Are they bad? Will they work properly in the amp or could that much
gain cause a problem? Will the difference between the sides of Tube 5 be an
issue? I wish I knew the answers.
Rather than send these tubes back as well (the return postage was getting
out of hand), I decided to put them in the VTL amp and just see how they
sounded. I paired Tubes 1 with 5 and Tubes 2 with 4. My assumption
being that this would tend to even out their differences. I really have no
idea if this is the case or not. I do not know which side of these tubes is
actually being used by the amp or whether only one or both sides are being
used. I do not have a schematic for the VTL and probably could not follow
it if I did.
I put the tubes in and turned the VTL on by itself—and immediately got a
loud racket from the right speaker. Another bad tube.
For the next few moments, I seriously considered switching to solid state
amplification.
I switched Tube 2 with the unused Tube 3. I got lucky. I found the bad
tube on the first try. The amp quieted right down. (Considering its age,
the VTL actually runs pretty quietly. I can only hear some quite low level
hum if I am closer than a foot from the Quad 21L 2’s woofer.)
I turned everything else on and warmed up the system using the Isotek
burn-in CD. Then I did some listening. The soundstage was wide; the bass
sounded and felt deep, the high-end was clean and quiet. Vocals were
beautifully centered in the middle.
The system sounded great, despite having crappy measuring tubes in it.
There are two things about this tube testing experience that bother me.
First, testing the tubes did nothing to identify Tube 2, the noisy tube.
There was no indication that anything was wrong with it.
Second, the system sounds great so the inconsistent results produced by
the testing do not really seem to matter, anyway.
I have been asking myself is there any point to even testing tubes? I
expected that having a quality tube tester would make things simple and
give me clear-cut results. This has not been the case; I get
incomprehensible results that only lead to worries and concerns.
Frankly, I would like someone else to do the worrying and just sell me tubes
that will work in my equipment.
It is possible to purchase matched pairs and quads of just about every type
of output tube. So why isn’t someone selling closely matched six, eight, or
ten-packs of preamp tubes as well? I would happily pay a (reasonable)
premium for this service. If I could get six tubes with no duds, I would be
far happier than I am now buying eight random tubes because I know I will
get at least one outright bad one. It seems to me there is a marketing
opportunity going begging here.
If testing tubes has taught me anything, it is that the less I know about
how my tubes measure, the happier I can live with them. If they sound
good, then they are good. Ignorance, at least where tube measurements
are concerned, can be bliss.
I think the Heathkit TT-1A will be looking for a new home.
Kent Johnson
April 2, 2008