Why the high price for tube amps?

[Michael A. Terrell]

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. ;-)


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

 

[Jim Thompson]

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 ;-)

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Michael A. Terrell]

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.

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

 

[Bob Masta]

On Fri, 17 Jan 2014 13:53:27 -0600, Tim Wescott
<tim@seemywebsite.really> wrote:

On Fri, 17 Jan 2014 13:58:46 -0500, Michael Black wrote:

On Fri, 17 Jan 2014, etpm@whidbey.com wrote:


I understand about the boutique status of the amps and why this raises
the price of the kits, tubes, and completed units. But I didn't know
that the xmfrs were so special. Is there a simple way to tell if the
xmfrs in a thrift store unit are any good? I suppose I could look for
specific brand names. But is there any other way? Aside from the sound
a tube amp would look cool on the shelf with all the glow. But I mainly
want to see how one I make sounds.
Eric

It's not absolute, but the bigger the transformer the better.

Look at a cheap All American 5 radio, the transformers aren't much
bigger than you'd see in transistor radios (when transistor radios had
transformers in the audio chain). They have to be limited in their
ability to reproduce lower frequencies. A good amplifier from the tube
age would have vastly bigger transformers.

Think about speakers. A tiny 2" speaker in a transistor radio has no
bass, can't handle power, may not even be so good at handling high
frequenies. Good speakers will be much bigger, and with a nice hefty
magnet. It really is the same thing, since both the transformers and the
speakers have to handle the full range of sound and the full power
output,
and are doing it at a low impedance (well the secondary of the output
transformer).

Interstage coupling transformers can be much smaller because they are
operating at high impedance, a very low current situation.

Go with Phil's idea, build the amplifier with plenty of space for output
transformers, and until you find some good ones (hence the space for
their eventual placement) use power output transformers. Not hifi, but
it gives you practice.

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. These amps are definitely not made for
"high fidelity". (There is no source to be faithful to,
because they *are* the source!) Look at the speakers they
are driving. Guitar speakers are usually designed to match
the range of guitars, with emphasis on the low end, and
especially on lots of power. They are completely different
beasts from "high fidelity" speakers such as you might use
in a reproduction system. I doubt a guitar amp designer
would have worried about the response much above a few kHz,
since there wouldn't have been much to begin with.

But they probably would sound OK, in the same way that the
old juke boxes did: Seemed nobody back then wanted too much
high end; leaving it out made things sound "mellow". A big
goal was "gut-thumping bass".

Best regards,


Bob Masta

DAQARTA v7.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusiq generator
Science with your sound card!

 

[amdx]

On 1/18/2014 4:11 AM, Michael A. Terrell 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.

Or have the time to wait for the wagon train to show up.
Mikek

 

[petrus bitbyter]

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> schreef
in bericht newspdjd9hpf4fepp934175hu9mq8k28lu02u@4ax.com...

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 ;-)

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Tubes were less expensive at the time. My first tube was less expensive then
my first transistor. Though a set of matched EL34 for "only" $8? I don't
remember them to be that cheap. Nevertheless you can still buy these types
for much less then the $50,- I mentioned for a real good set.

petrus bitbyter

 

[petrus bitbyter]

"Michael A. Terrell" <mike.terrell@earthlink.net> schreef in bericht
news:a-idnWF_6snKzkfPnZ2dnUVZ_vednZ2d@earthlink.com...

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.

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

Especially that dirty second hand vacuum is not easy to install. You'll need
a vacuum cleaner and a stable hand

petrus bitbyter

 

[Jim Thompson]

On Sat, 18 Jan 2014 10:33:38 -0600, amdx <nojunk@knology.net> wrote:

On 1/18/2014 4:11 AM, Michael A. Terrell 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.

Or have the time to wait for the wagon train to show up.
Mikek

Come on now, guys! I'm only about to celebrate my 18.5 birthday ;-)

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Jim Thompson]

On Sat, 18 Jan 2014 17:49:10 +0100, "petrus bitbyter"
<petrus.bitbyter@hotmail.com> wrote:

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> schreef
in bericht newspdjd9hpf4fepp934175hu9mq8k28lu02u@4ax.com...
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 ;-)

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Tubes were less expensive at the time. My first tube was less expensive then
my first transistor. Though a set of matched EL34 for "only" $8? I don't
remember them to be that cheap. Nevertheless you can still buy these types
for much less then the $50,- I mentioned for a real good set.

petrus bitbyter

I last bought 4 El34's (2 matched pairs) in _1958_ !

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Fred Abse]

On Fri, 17 Jan 2014 12:47:51 -0700, Jim Thompson wrote:

Transformer quality is by-the-pound ;-)

When I built toooob stuff, the transformers were "two-hands" worth.

ISTR that the output transformer for the Williamson design had a primary
inductance of 100H.

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[Jim Thompson]

On Sat, 18 Jan 2014 09:38:25 -0800, Fred Abse
<excretatauris@invalid.invalid> wrote:

On Fri, 17 Jan 2014 12:47:51 -0700, Jim Thompson wrote:

Transformer quality is by-the-pound ;-)

When I built toooob stuff, the transformers were "two-hands" worth.

ISTR that the output transformer for the Williamson design had a primary
inductance of 100H.

Wouldn't surprise me a bit. I don't remember a lot about those 50
year-old builds, but I vaguely recall an "ultra-linear" transformer
that had screen taps.

Ah, yes...

<http://www.clarisonus.com/Archives/Trans/Acro55.pdf>

and...

<http://tinyurl.com/m78pkbf>

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Tim Wescott]

On Fri, 17 Jan 2014 12:47:51 -0700, Jim Thompson wrote:

On Fri, 17 Jan 2014 09:53:54 -0800, etpm@whidbey.com wrote:

On Thu, 16 Jan 2014 23:41:07 -0600, Tim Wescott
tim@seemywebsite.really> wrote:

On Thu, 16 Jan 2014 12:49:51 -0800, etpm 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.

Tube amplifier quality is determined quite a bit by the transformer.
If you can find an old tube high fidelity amplifier in a thrift store,
then yes, you could rip out the transformers and make your own and hope
that it would sound good.

If you find some crappy old dime-store radio in thrift store, then
you're probably not going to get much better than crappy old dime-store
radio sound in your amplifier.

All consumer expectations aside, tube transformers are boutique items
that need a lot of expensive metal for the windings and the core, and
are being consumed at low volumes. Even if they were selling 100,000
units a year, you'd still have to pay for the copper and the iron.
Since they ain't selling 100,000 units a year, you're also paying a
stiff premium to buy a low-production item.
Greetings Tim,
I understand about the boutique status of the amps and why this raises
the price of the kits, tubes, and completed units. But I didn't know
that the xmfrs were so special. Is there a simple way to tell if the
xmfrs in a thrift store unit are any good? I suppose I could look for
specific brand names. But is there any other way? Aside from the sound a
tube amp would look cool on the shelf with all the glow. But I mainly
want to see how one I make sounds.
Eric

---
This email is free from viruses and malware because avast! Antivirus
protection is active.
http://www.avast.com

Transformer quality is by-the-pound ;-)

When I built toooob stuff, the transformers were "two-hands" worth.

...Jim Thompson

And copper by the pound costs $$$

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

 

[Fred Abse]

On Sat, 18 Jan 2014 11:06:09 -0700, Jim Thompson wrote:

On Sat, 18 Jan 2014 09:38:25 -0800, Fred Abse
excretatauris@invalid.invalid> wrote:

On Fri, 17 Jan 2014 12:47:51 -0700, Jim Thompson wrote:

Transformer quality is by-the-pound ;-)

When I built toooob stuff, the transformers were "two-hands" worth.

ISTR that the output transformer for the Williamson design had a primary
inductance of 100H.

Wouldn't surprise me a bit. I don't remember a lot about those 50
year-old builds, but I vaguely recall an "ultra-linear" transformer that
had screen taps.

Pretty ubiquitous, even in lowish-end stuff. IIRC, 43% was the "magic" tap
ratio.

AKA "Partial Triode" operation.

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[Jasen Betts]

On 2014-01-18, petrus bitbyter <petrus.bitbyter@hotmail.com> wrote:

"Michael A. Terrell" <mike.terrell@earthlink.net> schreef in bericht
news:a-idnWF_6snKzkfPnZ2dnUVZ_vednZ2d@earthlink.com...

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.

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

Especially that dirty second hand vacuum is not easy to install. You'll need
a vacuum cleaner and a stable hand

A stable hand? that vaccum must have be really dirty!

--
For a good time: install ntp

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Michael A. Terrell]

Jim Thompson wrote:

On Sat, 18 Jan 2014 10:33:38 -0600, amdx <nojunk@knology.net> wrote:

On 1/18/2014 4:11 AM, Michael A. Terrell 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.

Or have the time to wait for the wagon train to show up.
Mikek

Come on now, guys! I'm only about to celebrate my 18.5 birthday ;-)

Yeah, but for the forth time, Jack Benny.


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

 

[Michael A. Terrell]

Jim Thompson wrote:

On Sat, 18 Jan 2014 17:49:10 +0100, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> schreef
in bericht newspdjd9hpf4fepp934175hu9mq8k28lu02u@4ax.com...
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 ;-)

...Jim Thompson

Tubes were less expensive at the time. My first tube was less expensive then
my first transistor. Though a set of matched EL34 for "only" $8? I don't
remember them to be that cheap. Nevertheless you can still buy these types
for much less then the $50,- I mentioned for a real good set.

petrus bitbyter


I last bought 4 El34's (2 matched pairs) in _1958_ !

That was two years before I built my first radio.


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

 

[Jim Thompson]

On Sat, 18 Jan 2014 16:53:54 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Jim Thompson wrote:

On Sat, 18 Jan 2014 10:33:38 -0600, amdx <nojunk@knology.net> wrote:

On 1/18/2014 4:11 AM, Michael A. Terrell 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.

Or have the time to wait for the wagon train to show up.
Mikek

Come on now, guys! I'm only about to celebrate my 18.5 birthday ;-)


Yeah, but for the forth time, Jack Benny.

Exacutly ;-) Well! Not exacutly, more like fourth time >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Jim Thompson]

On Sat, 18 Jan 2014 16:55:39 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Jim Thompson wrote:

On Sat, 18 Jan 2014 17:49:10 +0100, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> schreef
in bericht newspdjd9hpf4fepp934175hu9mq8k28lu02u@4ax.com...
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 ;-)

...Jim Thompson

Tubes were less expensive at the time. My first tube was less expensive then
my first transistor. Though a set of matched EL34 for "only" $8? I don't
remember them to be that cheap. Nevertheless you can still buy these types
for much less then the $50,- I mentioned for a real good set.

petrus bitbyter


I last bought 4 El34's (2 matched pairs) in _1958_ !


That was two years before I built my first radio.

I built my first tube radio, a TRF, when I was in Cub Scouts; and
built a superhet with CK760's when I was ~14.

(Advantage: Father had radio and TV repair shop up and running by
1948.)

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Tim Wescott]

On Fri, 17 Jan 2014 11:42:07 -0800, etpm wrote:

On Fri, 17 Jan 2014 12:07:02 -0600, Tim Wescott
tim@seemywebsite.really> wrote:

On Fri, 17 Jan 2014 09:53:54 -0800, etpm wrote:

On Thu, 16 Jan 2014 23:41:07 -0600, Tim Wescott
tim@seemywebsite.really> wrote:

On Thu, 16 Jan 2014 12:49:51 -0800, etpm 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.

Tube amplifier quality is determined quite a bit by the transformer.
If you can find an old tube high fidelity amplifier in a thrift store,
then yes, you could rip out the transformers and make your own and
hope that it would sound good.

If you find some crappy old dime-store radio in thrift store, then
you're probably not going to get much better than crappy old
dime-store radio sound in your amplifier.

All consumer expectations aside, tube transformers are boutique items
that need a lot of expensive metal for the windings and the core, and
are being consumed at low volumes. Even if they were selling 100,000
units a year, you'd still have to pay for the copper and the iron.
Since they ain't selling 100,000 units a year, you're also paying a
stiff premium to buy a low-production item.
Greetings Tim,
I understand about the boutique status of the amps and why this raises
the price of the kits, tubes, and completed units. But I didn't know
that the xmfrs were so special. Is there a simple way to tell if the
xmfrs in a thrift store unit are any good? I suppose I could look for
specific brand names. But is there any other way? Aside from the sound
a tube amp would look cool on the shelf with all the glow. But I
mainly want to see how one I make sounds.

The only way I know would be to make sure that the thrift store
amplifier was pretty damned good to begin with.

There's a pretty marked correlation between quality and expense to an
audio transformer, and always has been. Not very many people would have
built cheezy equipment with really good transformers.

The only other possible way that I can think of would be to hook up with
an old-time audiophile who happens to know if there were any brands or
models whose transformers were better than the rest of the amp.

But I just don't think that you're going to hit the "audiophile"
threshold in a thrift-store tube amp, if you could even find something
in a thrift store with tubes. You may hit paydirt at an estate sale, or
finding something on eBay that's trashed but has good output
transformers, but I just don't think the local Goodwill is going to be
your friend, here.
The reason I mentioned thrift stores is because I do see old tube amps
and radios for sale pretty cheap ikn thrift stores around where I live.

Snag one! Or three! If it's your first amp, then anything that had
pretensions of being high fidelity is probably going to work for you.
The rest you can sell on eBay and get some $$ for buying toobs.

Note that every one is going to be set up differently -- without knowing
the specs of the final transformers you'll be at a bit of a
disadvantage. You can try measuring turns ratio and work out the input
impedance from that: it'll probably be pretty close. But if you get
something that's set up for ultra linear operation, or some wacky output
tubes, or some such, you may be up a creek until you get it figured out.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[John Fields]

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

11:08