Why the high price for tube amps?

[Michael A. Terrell]

John Fields wrote:

On Sat, 18 Jan 2014 05:11:31 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


Jim Thompson wrote:

On Fri, 17 Jan 2014 18:39:06 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


Jim Thompson wrote:

On Fri, 17 Jan 2014 23:23:45 +0100, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

Good tubes never were cheap. A good set of matched EL34 for instance can do
a $50,- and you need two set for a stereo amp.

Not when I was a kid, IIRC ~$8 ;-)


The vacuum was shipped separately, when you were a kid. ;-)

Be nice ;-)


I was! Not everyone was skilled enough to install the vacuum.

---
http://www.youtube.com/watch?v=EzyXMEpq4qw

I've seen this before. That's a lot of work, but he looks like he's
having fun.


The 'professor' needed that equipment on Gilligan's Island to build a
transmitter.

RIP Russell Johnson, 2014-01-16. His website hasn't been updated in
years. http://www.russell-johnson.com/


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

 

[Phil Allison]

"Bob Masta"

If you can't find power transformers, or if you're married to the idea of
"audio" transformers, look at tube guitar amp output transformers.

They're mass-marked (well, kinda), won't sound terribly bad, and the
price is nice for lower power kit.

I've been kicking around the idea of a 15W/channel toob amp for my PC
speakers, using guitar amp output trannys sitting on a chassis with
enough space for the nice Hammond ones that Antique Radio Supply sells.


I wouldn't expect any kind of decent high end response from
a guitar amp xfmr.

** But you are far too lazy to look up any data or do any testing.

And you are sooooo wrong.

These amps are definitely not made for "high fidelity".

** Which says nothing about the output transformers.

I doubt a guitar amp designer
would have worried about the response much above a few kHz,

** I doubt you have ever seen or bench tested a guitar amplifier.


FYI:

Hammond's general range output transformers are speced at +/-1dB to 30kHz.

http://www.hammondmfg.com/1608.htm

The guitar amp specific models are speced at +/- 1dB to 15kHz.

http://www.hammondmfg.com/pdf/EDB1750P.pdf


The specs are quite conservative too, most examples being much better.



..... Phil

 

[default]

On Fri, 17 Jan 2014 11:39:17 +0000 (UTC), asdf <asdf@nospam.com>
wrote:

etpm@whidbey.com wrote:

I have been thinking about making a tube amp for fun so I can compare
the sound to a good solid state amp and because I like making things.

Mosfet amps get the best of two worlds IMO: they sound very close or
identical to tubes and can be really easy to build. Not to mention
they're a lot cheaper.
They don't glow unfortunately, but something can be done about that
http://www.youtube.com/watch?v=ekuqOaRbp8g

Nelson Pass had the zen series of mosfets - circuits still on line I'm
sure.

Here's one
http://www.soundandvision.com/content/podcast-42-nelson-pass

https://www.passdiy.com/pdf/ZV9.pdf

class A for clean sound, with light bulbs as current ballasts in the
constant current side of the amp. Light bulbs are still cheap, nice
porcelien/ceramic sockets still available, what's not to like?

The glow will be there, particularly if you parallel a few, and unlike
the light show, when they change brilliance it will be because the
current is modulated.

I cobbled together one of his "Zen" amps and the sound was
exceptional; much better than any bipolar DC coupled class AB I've
listened to. I used a three terminal regulator as a constant current
source. Light bulbs make a lot of sense - dynamic current ballasting
with no heat sink requirements.
--

 

[default]

On Thu, 16 Jan 2014 12:49:51 -0800, etpm@whidbey.com wrote:

I have been thinking about making a tube amp for fun so I can compare
the sound to a good solid state amp and because I like making things.
I remember with fondness the sound from my old tube amps years ago.
But it could be that my memory is flawed. Anyway, I looked at kits and
they are all very expensive. Tubes themselves are not that expensive
and many amps that get good reviews only have a couple tubes.
Transformers are really expensive. Are the transformers used for tube
amps really that special? What if I just buy an old amp from a thrift
store and replace the tubes and any other components that might be
bad. Do the transformers go bad? Does the insulation degrade? I have
and use electric motors that are over 50m years old and their windings
don't suffer from bad insulation. I even have old magnetos on old
tractors that work perfectly and the insulation in them must be pretty
stressed because of the high voltage.
Thanks,
Eric

---
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http://www.avast.com

You can always wind your own output transformers if you like a
challenge. I worked for a PS manufacturer in San Diego and he wound
his own 60 cycle (400 HZ and switch mode) transformers with some
better quality grain-oriented silicon steel cores with a 1:1 stack.

One Tube amped guitarist had him wind a custom power transformer and
it ran so cool compared to the OEM one (and was a little smaller too)
that he wanted us to start making output transformers. We dissected
one very expensive one to copy. I think it was called an
"ultra-linear" design and had both plate and cathode windings.

Winding transformers is not that hard. Designing them is somewhat
harder - particularly in the days of slide rules when spread sheets
were unavailable. Wind the first one from calculations then wind
another using results of the first. Two times would almost always
nail it. We'd often build our own bobbins or modify stock ones to
suit the core stack.

I wound a 1 KW induction coil with some 13 miles of wire (32 AWG) in
the secondary. It took me a month to build, but I did the secondary
winding in a week's worth of spare time. I adapted a DC tape reel
drive motor to make a kluged together winding lathe (that took all of
two hours or so) A primitive variac controlled power supply tensioned
the wire and spun it on. The design was from an early wireless text
with modifications since "double cotton covered wire," hard rubber
sheets and gutta-percha is hard to find these days.

What do you do with a KW class induction coil? Excite Tesla coils and
throw lightning, make ozone and X-rays, among other things.
--

 

[Steve]

etpm@whidbey.com writes:

< I have been thinking about making a tube amp for fun so I can compare
< the sound to a good solid state amp and because I like making things.

That makes me sound warm and fuzzy...

< I remember with fondness the sound from my old tube amps years ago.
< But it could be that my memory is flawed. Anyway, I looked at kits and
< they are all very expensive. Tubes themselves are not that expensive
< and many amps that get good reviews only have a couple tubes.

I would think the main cost would be the labor of point to point
soldering - but the truth of the matter is that aluminum chassis do not
exist. You are supposed to use adhesive and there is no such thing as
bakelite (I don't know what that means.) No - the box can not be 5
inches deep. It's some kind of universal truth or something.

< Transformers are really expensive. Are the transformers used for tube
< amps really that special?

I think that the selenium rectifiers might be a bit difficult to find. I
only have one and am using it.

< What if I just buy an old amp from a thrift
< store and replace the tubes and any other components that might be
< bad. Do the transformers go bad? Does the insulation degrade?

The electrolytic capacitors usually dry up from what I understand.

The condenser (read: variable capacitor) is patented and aluminum is no
longer available. If you accidentally mention the phrase ``xyz plating''
as in silver plating they will probably commit you to the psych unit. I
tried building a tuning condenser and ran out of washers only to find
out that I was committing a crime by asking for knurled copper split
rings at the home depot.

Reduction assemblies for the tuner are diffucult to find. I dreamed of
one day making a mold and pouring in some aluminum but again finding
aluminum these days is difficult and who wants to tear apart a still
working gear assembly to attempt a mold - I know there are people that
can do this - I however am not one of them.

< I have
< and use electric motors that are over 50m years old and their windings
< don't suffer from bad insulation.

They used to use better wire and better insulation I think. I have a
current transformer that looks like it has been soaking in sea water
since the 1950s. the black tar ``transformer varnish'' seems to have
worked well as the transformer and the meter still work. Unfortunately
the battery is dead and the resistors are not replaceable (asking for
carbon 1 watt resistors will only make people laugh at you when they try
``correcting'' you with ``you mean ... '' metal film) ... Damn magnets!

< I even have old magnetos on old
< tractors that work perfectly and the insulation in them must be pretty
< stressed because of the high voltage.

Yes high voltage at several milliamps still scares people. They will
think you are making a taser or a plastic truck that plugs into the
electical outlet.

< Thanks,

thank you - needed to vent.