Serious stereo tube amp questions.

I have always like exposed tube equipment. Since I was a little
kid. So I have been thinking about getting a small stereo tube amp for
the living room to replace the typical modern amp we have. That no
longer works.
All the modern small amps have outputs of several tens of watts.
But all of the small tube amps I see and remember only have outputs of
less than ten watts. Is there something sneaky about the how the
output of modern amps is rated? I know there is gonna be some puffing
up of numbers but it seems drastic. And if the modern amps have hugely
inflated numbers does that mean a tube amp rated at 5 watts is really
only a watt or so?
There are a couple amps I have some interest in and would like
opinions on them if anybody here has the time to check out the links.
Here's the first:
https://www.ebay.com/itm/Stereo-6P1-Vacuum-Tube-Amplifier-Class-A-Single-Ended-Power-Amp-6-8W-2-Black/253343561504?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D3d9e7203be8141d5a456d24eb0de6f49%26pid%3D100675%26rk%3D7%26rkt%3D15%26mehot%3Dpp%26sd%3D232926640491%26itm%3D253343561504&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3Afade2d01-dd65-11e8-b2c7-74dbd180c23c%7Cparentrq%3Acc7d86731660aadab4e3bf87fffadd9b%7Ciid%3A1

Sorry about the mile long link. Does this amp look any good for the
money? Can someone even tell from looking at the description? I'd buy
an older used amp with exposed tubes if I could find one that I knew
worked and wasn't really expensive. I want something that sounds OK. I
am by no means an audiophile, my ears aren't that good and I know it.
But I can still hear hum and hiss.

Here's the second amp link:
https://www.ebay.com/p/APPJ-Assembled-Fu32-Single-ended-Tube-Amplifier-Stereo-Power-Amp-Board-HIFI-DIY/716663897?iid=282415070393&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20131231084308%26meid%3D403303410e0041a1b0482a2943aa48ae%26pid%3D100010%26rk%3D4%26rkt%3D12%26mehot%3Dpp%26sd%3D263867889779%26itm%3D282415070393&_trksid=p2047675.c100010.m2109

Another long link. There's probably enough info in that link to
describe the position of every particle in the universe. Anyway, I was
just interested in the power tube, the FU32. I have never seen a tube
like that. Is it actually just two tubes in one glass envelope?
Sharing some pins I assume? Anyway, are these types of tubes common?

The last thing I was wondering about was what determines the output
power of an amp. Is it just the tubes? Transformers? Or a combination
of tubes and transformers?
Thanks,
Eric

 

[Phil Allison]

et...@whidbey.com wrote:

I have always like exposed tube equipment. Since I was a little
kid. So I have been thinking about getting a small stereo tube amp for
the living room to replace the typical modern amp we have. That no
longer works.

** So you might as well replace it with something completely useless.

All the modern small amps have outputs of several tens of watts.
But all of the small tube amps I see and remember only have outputs of
less than ten watts. Is there something sneaky about the how the
output of modern amps is rated?

** No.

The Chinese tube amps you are citing are mere toys.

Ornaments or conversation pieces for oyur desk or mantelpiece.

Sorry about the mile long link. Does this amp look any good for the
money?

** No - its a toy amp.

Another long link. There's probably enough info in that link to
describe the position of every particle in the universe. Anyway, I was
just interested in the power tube, the FU32. I have never seen a tube
like that. Is it actually just two tubes in one glass envelope?
Sharing some pins I assume? Anyway, are these types of tubes common?

** Another toy amp, the Chinese are laughing all the way to the bank.

The last thing I was wondering about was what determines the output
power of an amp. Is it just the tubes? Transformers? Or a combination
of tubes and transformers?

** Totally off with the fairies.


...... Phil

 

[default]

On Wed, 31 Oct 2018 17:19:04 -0700, etpm@whidbey.com wrote:

I have always like exposed tube equipment. Since I was a little
kid. So I have been thinking about getting a small stereo tube amp for
the living room to replace the typical modern amp we have. That no
longer works.
All the modern small amps have outputs of several tens of watts.
But all of the small tube amps I see and remember only have outputs of
less than ten watts. Is there something sneaky about the how the
output of modern amps is rated? I know there is gonna be some puffing
up of numbers but it seems drastic. And if the modern amps have hugely
inflated numbers does that mean a tube amp rated at 5 watts is really
only a watt or so?
There are a couple amps I have some interest in and would like
opinions on them if anybody here has the time to check out the links.
Here's the first:
https://www.ebay.com/itm/Stereo-6P1-Vacuum-Tube-Amplifier-Class-A-Single-Ended-Power-Amp-6-8W-2-Black/253343561504?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D3d9e7203be8141d5a456d24eb0de6f49%26pid%3D100675%26rk%3D7%26rkt%3D15%26mehot%3Dpp%26sd%3D232926640491%26itm%3D253343561504&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3Afade2d01-dd65-11e8-b2c7-74dbd180c23c%7Cparentrq%3Acc7d86731660aadab4e3bf87fffadd9b%7Ciid%3A1

Sorry about the mile long link. Does this amp look any good for the
money? Can someone even tell from looking at the description? I'd buy
an older used amp with exposed tubes if I could find one that I knew
worked and wasn't really expensive. I want something that sounds OK. I
am by no means an audiophile, my ears aren't that good and I know it.
But I can still hear hum and hiss.

Here's the second amp link:
https://www.ebay.com/p/APPJ-Assembled-Fu32-Single-ended-Tube-Amplifier-Stereo-Power-Amp-Board-HIFI-DIY/716663897?iid=282415070393&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20131231084308%26meid%3D403303410e0041a1b0482a2943aa48ae%26pid%3D100010%26rk%3D4%26rkt%3D12%26mehot%3Dpp%26sd%3D263867889779%26itm%3D282415070393&_trksid=p2047675.c100010.m2109

Another long link. There's probably enough info in that link to
describe the position of every particle in the universe. Anyway, I was
just interested in the power tube, the FU32. I have never seen a tube
like that. Is it actually just two tubes in one glass envelope?
Sharing some pins I assume? Anyway, are these types of tubes common?

The last thing I was wondering about was what determines the output
power of an amp. Is it just the tubes? Transformers? Or a combination
of tubes and transformers?
Thanks,
Eric

Back in the day...

Tube amps were usually rated in RMS power whereas transistor amps were
often rated in something called "music power" which meant very little
as a rule. Some of the things were so hyped that the only way they
could produce their rated power was "the instantaneous peak power, at
the wall-plug, the instant they were turned on."

RMS power is what counts, although some more ethical manufacturers did
actually come up with a few schemes to dramatically improve reserve
power for the occasional bass note that needed a lot of power, they
called it "dynamic power," which, in turn, became over-used and
abused. They couldn't sustain that power output for long, but the amp
was designed so it could pull that amount from the (beefy) power
supply caps for a brief period before protection circuitry kicked in
and limited it.

All that said, with most efficient speakers a few watts is all you
generally actually need. With both tube and transistor amps they
over-drive differently and when a tube amp is over driven it still
sounds OK (up to a point) whereas a transistor amp over-drives
produces square waves that don't sound nearly as good. (AND have the
nasty habit of sailing on through the high pass network of the speaker
crossovers and frying the midrange and tweeters which can't handle the
power that woofers can)

You can get tube amps into the 100's of watts, but they are costly.
Unless you have a guitar amp, and a sadistic bent, or are deaf, or are
driving some theater seat-shaker transducers, a tube amp with ten
watts per channel is probably going to be enough for most people.

If you care about the sound class A will always sound better than
class AB. (I can't say about digital amps because I don't own any)
Mosfet output stages sound better to me than bipolar transistors as a
rule.

I've managed to snag a pair of Crown amps that were sold as Gradient
Drive Amplifiers for a MRI machine. They sound great, but weigh 80
pounds per channel, can put out 1,000 watts RMS (I can literally make
toast with the output - I tried it). It is class AB but the crossover
point is biased at about 100 watts so the first 100 is class A, and
anything over that and you don't want to be in the same room with it,
or better be calling the fire department because your woofers are on
fire. If the speakers could handle it I'd probably get complaints
from seismic monitoring stations.

Digital amps can produce large amounts of power cheaply. They are
more akin to switching power supplies that are modulated by a music
source.

 

[default]

On Wed, 31 Oct 2018 17:19:04 -0700, etpm@whidbey.com wrote:

The last thing I was wondering about was what determines the output
power of an amp. Is it just the tubes? Transformers? Or a combination
of tubes and transformers?
Thanks,

It is determined by how much power goes to the speakers. That, in
turn, is usually dependent on the voltage the amp is running on, by
ohms law. Power (watts) is the amps times the volts. If you have 8
ohm speakers and are pushing one amp through them you have 8 watts of
power and are using 8 volts to do it. Really high power transistor
amps use power supplies capable of 200 volts and can produce a few
thousand watts at the speakers.

The voltage a tube amp runs on is not as important because you
generally have an output transformer and aren't driving speakers
directly. But the power is still important and it still takes more
iron, copper and money to produce more power in conventional tube
amps.

Class A produces heat because when the amp is just sitting there with
the sound muted it is still dissipating the full power through the
tubes or transistors, class AB is static power is determined by the
bias point (how much current is allowed to flow with no sound out -
higher bias = more heat and better sound due to less cross-over
distortion)

Everything gets larger in conventional (linear) amplifiers as power
increases. More copper, more iron, bigger filter caps, more money. At
some point, if you really like music and have golden ears, the money
is better spent developing a good music room rather than shelling out
more for amps. There is such a thing as a law of diminishing returns.
For $50 you can build a pretty decent amp but to make it sound
significantly better might take $500....

We had some audio power amps in the navy that were used to drive a
deflection yoke in a direction finding display. Old tube technology.
The amp used direct drive and had a whole chassis of nothing but big
tubes with graphite plates running cherry red and producing huge
amounts of heat to push the relatively low voltage through the
deflection coils. It was all done to produce a very low distortion
signal so the display would show a perfect circular light trace on the
screen. Any deviation from perfection resulted in a DF bearing being
off by a degree or two. (which translates into miles of error)

They were replaced with solid state devices and better technology.

 

[Ralph Mowery]

In article <uogltd9eds7vrkj408rssql9db6lepj02t@4ax.com>,
default@defaulter.net says...

Digital amps can produce large amounts of power cheaply. They are
more akin to switching power supplies that are modulated by a music
source.

I bought a couple of the 5 watt or so switching amps form China to play
with. Put them on a scope and it was interisting. Instead of seeing a
sine wave, it looked like a bunch of pulses. It sounded ok to my
untrained ear for voice quality.

 

[Michael Black]

On Thu, 1 Nov 2018, Ralph Mowery wrote:

In article <uogltd9eds7vrkj408rssql9db6lepj02t@4ax.com>,
default@defaulter.net says...

Digital amps can produce large amounts of power cheaply. They are
more akin to switching power supplies that are modulated by a music
source.



I bought a couple of the 5 watt or so switching amps form China to play
with. Put them on a scope and it was interisting. Instead of seeing a
sine wave, it looked like a bunch of pulses. It sounded ok to my
untrained ear for voice quality.

I remember a 555 based class D amplifier in Elementary Electronicsi n the
mid-seventies. And it relied on the speaker, and the ear, to do the
filtering. So of course on a scope it would look digital, but might sound
'fine".

I've not paid enough attention to more serious work to know how much
relies on the speaker to do the filtering and how much is doen by
deliberate filters.

Michael

 

[default]

On Thu, 1 Nov 2018 12:34:19 -0400, Ralph Mowery
<rmowery28146@earthlink.net> wrote:

In article <uogltd9eds7vrkj408rssql9db6lepj02t@4ax.com>,
default@defaulter.net says...

Digital amps can produce large amounts of power cheaply. They are
more akin to switching power supplies that are modulated by a music
source.



I bought a couple of the 5 watt or so switching amps form China to play
with. Put them on a scope and it was interisting. Instead of seeing a
sine wave, it looked like a bunch of pulses. It sounded ok to my
untrained ear for voice quality.

Sometimes it takes some magic to get a good reading with a scope and
digital sound source. A ground loop or sometimes just the way the amp
is laid out and shielded will allow switching transients through...
and other times it is just not filtered all that well, particularly
those elcheapo Chinese amps where most of the design effort is in
marketing bling rather than quality components like low ESR caps and
suitable magnetic components.

 

On Thu, 01 Nov 2018 06:08:51 -0400, default <default@defaulter.net>
wrote:

On Wed, 31 Oct 2018 17:19:04 -0700, etpm@whidbey.com wrote:

The last thing I was wondering about was what determines the output
power of an amp. Is it just the tubes? Transformers? Or a combination
of tubes and transformers?
Thanks,


It is determined by how much power goes to the speakers. That, in
turn, is usually dependent on the voltage the amp is running on, by
ohms law. Power (watts) is the amps times the volts. If you have 8
ohm speakers and are pushing one amp through them you have 8 watts of
power and are using 8 volts to do it. Really high power transistor
amps use power supplies capable of 200 volts and can produce a few
thousand watts at the speakers.

The voltage a tube amp runs on is not as important because you
generally have an output transformer and aren't driving speakers
directly. But the power is still important and it still takes more
iron, copper and money to produce more power in conventional tube
amps.

Class A produces heat because when the amp is just sitting there with
the sound muted it is still dissipating the full power through the
tubes or transistors, class AB is static power is determined by the
bias point (how much current is allowed to flow with no sound out -
higher bias = more heat and better sound due to less cross-over
distortion)

Everything gets larger in conventional (linear) amplifiers as power
increases. More copper, more iron, bigger filter caps, more money. At
some point, if you really like music and have golden ears, the money
is better spent developing a good music room rather than shelling out
more for amps. There is such a thing as a law of diminishing returns.
For $50 you can build a pretty decent amp but to make it sound
significantly better might take $500....

We had some audio power amps in the navy that were used to drive a
deflection yoke in a direction finding display. Old tube technology.
The amp used direct drive and had a whole chassis of nothing but big
tubes with graphite plates running cherry red and producing huge
amounts of heat to push the relatively low voltage through the
deflection coils. It was all done to produce a very low distortion
signal so the display would show a perfect circular light trace on the
screen. Any deviation from perfection resulted in a DF bearing being
off by a degree or two. (which translates into miles of error)

They were replaced with solid state devices and better technology.

Thanks for the replies. The amps I have been considering are all class
A amps. I am not interested in hybrid amps. And even though I listen
to MP3 players every day and will be playing an MP3 player through
whatever amp I get I still want a purely analog amp.
Eric

 

[Jasen Betts]

On 2018-11-01, etpm@whidbey.com <etpm@whidbey.com> wrote:

https://www.ebay.com/itm/Stereo-6P1-Vacuum-Tube-Amplifier-Class-A-Single-Ended-Power-Amp-6-8W-2-Black/253343561504?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D3d9e7203be8141d5a456d24eb0de6f49%26pid%3D100675%26rk%3D7%26rkt%3D15%26mehot%3Dpp%26sd%3D232926640491%26itm%3D253343561504&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3Afade2d01-dd65-11e8-b2c7-74dbd180c23c%7Cparentrq%3Acc7d86731660aadab4e3bf87fffadd9b%7Ciid%3A1

Sorry about the mile long link.

you can trim those:

https://www.ebay.com/p/X/716663897

--
When I tried casting out nines I made a hash of it.