response 1 of 13:

Jun 13 11:14 UTC 1996

Wow, where to start?  Certainly not now, since I have to finish breakfast and
get to work on time.  :)

However, I'll likely have a decent amount to say here soon.

response 3 of 13:

Jun 16 22:16 UTC 1996

You don't need to replace blue-glowing tubes until they burn out prematurely.
(heh).

Sounds like your biasing isn't doing its job!  That's fairly easy for a tech
to diagnose and fix, though, unless the bias tap on the power transformer
died.  Much more likely is that a bias resistor or diode or maybe the filter
capacitor died.  Replacing the tubes won't help, since the bad bias will screw
replacements just as easily.  BTW, a small amount of blue in there is normal,
but any change you've noticed is trouble that needs to be fixed soon.

I've got a great source for tubes, probably $25 or so a pair?  I think that
is the price of the Russkie made Sovtek 6L6 tubes, which are the Fender OEM
variety.


No big surprise, I'm somebody who know a bit about tubes.  ;)

My own guitar amp is a 70's silver face Fender Princeton Reverb, a real sweet
little amp.  I've also got an old 50 watt DuKane chassis I turned into a cross
between a Fender Bassman and a Marshall 50 watt head.  I don't use that one
much, though.

For clean playing, solid state is fine.  I'm not a real snob about that, and
for my tube amp I have a solid state distortion pedal (a Boss "Blues Driver"),
so I'm not relying on tube distortion at all.  Go figure.  ;)  (It's about
doing stuff at a reasonable volume).

I think the main reason I use a tube amp is that I've had it for years and
I'm completely used to it.  Plus, tube amps, at least the older ones, are just
a bit easier to modify for various reasons.  At one point I was playing with
the idea of putting a Deluxe-type inverter stage in my Princeton, but it
didn't seem to improve anything (more gain, but I didn't need that).  Right
now the only change is a tweak to the tone circuit to provide more mids, and
a Peavy Scorpion speaker to replace the previous one (which was some kind of
Music Man OEM).

For bass, solid state is much more useful for EQ.  I've got a little bass
preamp I built with op-amps, a pretty sophisticated EQ for bass.  Tube amps
can be useful because they tend to handle transients better; for bass that
quite often improves the sound at volumes near the amp's power limit.
The classic Ampeg SVT sounds *really* good, mainly because of how well it does
transient attacks.  I've figured out that bass really needs an amplifier rated
for about 3 times what you can scrape by with, since the difference is better
transient response which for bass is *not* subtle.

response 5 of 13:

Jun 17 07:03 UTC 1996

A blue glow means they are gassy. They don't make 6L6s like they used to. 
This item reminds me of my "ultimate" Hi Fi - that I designed and built
in ca. 1954 - push-pull triodes all the way. They don't make amplifiers
like that any more  8^}

response 7 of 13:

Jun 17 11:21 UTC 1996

I would, I usually don't have time.  If it is under control of a music store,
can't you get them to fix it?

Re: 4 - Getting a good matched pair is essential.  I don't know if Purchase
does that, or what brands they sell.  Chinese tubes are pretty common, but
are generally frowned upon for their mortality rate.

Re: 5 - "Push-Pull"?  You are right, nobody makes those any more.  Last I
heard, single ended triodes were the trendy thing.  With directly
heated cathodes.  Western Electric 300B triodes.  The more primitive, the
better.

The power tubes have two main supplies... the B+ supply, which is a positive
300-600 volts on the plates, and a bias supply, which is a negative 40-70
volts on the grids to keep things in balance.  If the bias supply drops (or
the B+ increases), then too much current flows thru the tube when it is just
supposed to be idling.  This is because the tubes in a pair are assigned half
the load each... one handles positive, one handles negative.  So one tubes
is active, the other nearly shut off, until the waveform crosses the zero
voltage line and the tubes swap roles.  If the bias doesn't keep the "off"
tube at its cutoff point, then the tube passes DC and ends up running too hot.
Sometimes *way* too hot.  I'd find it hard to believe that you are getting
too much B+, though, since that is a hard thing to do even on purpose.

response 9 of 13:

Jun 17 21:47 UTC 1996

Regulation circuit might be the problem, if Peavy wasn't such a cheapskate
company.  I've *never* heard of a Peavy with B+ regulation, and few if any
guitar amps by any other manufacturers.

response 11 of 13:

Jun 28 22:40 UTC 1996

I don't have time to fuss with the electronics, so I just play.  I used to
do both.  :)

Know anybody who wants to try those King Crimson interlocking guitar parts
with another guitarist (to wit, me).

response 13 of 13:

Jun 29 12:34 UTC 1996

I might be able to look at your amp, raven.  Looks like a hardware vendor may
have screwed the schedule on my current project at work.  :/