[coffeedj]

I just returned from a far east trip and managed to put in a couple of days
in Hong Kong--visiting the DYI shops. There were some interesting points
learned.

First--we can get most of the DYI stuff for better or equal price in the
USA. The one exception is transformers, but without knowledge of the
quality of the local brands it was hard to value these. Second, most of
shops were pretty vanilla and not necessarily staffed by DYI hardcores.
There were, however, a few very enjoyable divergences from this pattern. At
one shop I asked the owner for a specific vinyl I had been looking for (for
decades) and he sort of ignored me. Then as I started talking componets,
amps, speakers, and designs with him he lit up. Once he understood I was a
tube-o-phile and he pulled out the extremely rare vinyl from a pile behind
the desk and sold it to me! I guess I had to prove that I was worthy to buy
first.

The other interesting point was the degree of tube amp and vinyl interest in
Hong Kong. Used vinyl shops abound, and new vinyl is also advertised and
available. It seemed like every little used record or coffee shop I stopped
at had a sound system that was based on some newer chinese tube amp and a
record player. They are really into the tube sound and vinyl in HK.

Made some great contacts--all in all an enjoyable side trip. Stayed at the
Cyberport Hotel--highly recommended for an experience in new asian cyber
community.

[Patrick Turner]

coffeedj wrote:

I just returned from a far east trip and managed to put in a couple of days
in Hong Kong--visiting the DYI shops. There were some interesting points
learned.

First--we can get most of the DYI stuff for better or equal price in the
USA.

But is there such a thing as a DIY shop in HK?

Does this mean hobbyists making amplifiers after work at home are
selling what they have made
for themselves?

The one exception is transformers, but without knowledge of the
quality of the local brands it was hard to value these.

From what I have seen and tested on my bench, Chinese OPTs are
equal to the very worst quality produced by western nations in 1955,
with poor iron, cores not large enough for the watts, too few turns
and low primary inductances, saturation at too high a frequency,
poor HF range, and high leakage inductance and shunt capacitance,
and lord know what sort of insulation or winding practices have been
employed.

However, some OPT would be fine, such as those made for Quad amplifiers
which have been made there since IAG bought quad some years ago.
Consonance amps may also have nice iron, but there is much crap there.


Second, most of
shops were pretty vanilla and not necessarily staffed by DYI hardcores.

Exactly what do you mean?


There were, however, a few very enjoyable divergences from this pattern. At
one shop I asked the owner for a specific vinyl I had been looking for (for
decades) and he sort of ignored me. Then as I started talking componets,
amps, speakers, and designs with him he lit up. Once he understood I was a
tube-o-phile and he pulled out the extremely rare vinyl from a pile behind
the desk and sold it to me! I guess I had to prove that I was worthy to buy
first.

Ah, so you have to foolaroundabit to get served.

The other interesting point was the degree of tube amp and vinyl interest in
Hong Kong.

Its huge; they like tubes.

Used vinyl shops abound, and new vinyl is also advertised and
available.

It seemed like every little used record or coffee shop I stopped
at had a sound system that was based on some newer chinese tube amp and a
record player. They are really into the tube sound and vinyl in HK.

Well they'd certainly get "tube sound" and it wouldn't necessarily be
all that wonderful
going on what i have seen and heard.


Made some great contacts--all in all an enjoyable side trip. Stayed at the
Cyberport Hotel--highly recommended for an experience in new asian cyber
community.

Many fellows have emigrated to Oz from HK and the Audiophile Society of
NSW has a large
contingent in its membership of asian born and Oz born asians who
take their music very seriously, and from what I have
experienced, they are not easy to please, and they do tend to like tubes
and
vinyl, as many of them have for 50 years so far.
I found the Society to be a very pleasant lot of guys to spend a sunday
with listening to music.

The number of young people re-discovering vinyl magic is
very small, but perhaps it is growing amoung discerning ppl
with enough time to spare to enjoy music.
Meanwhile, the local School of Music has had a very hard time this year
attracting
enough students to justify keeping the doors open and teachers employed,
and not many ppl want to perform; they mostly all just want to consume,
be rich, and have no time because of high house prices and demanding
girlfriends.
And don't forget the majority of ppl 25 have been raised on junk. Junk
food, junk TV shows,
and certainly junk pop music.

Patrick Turner.

[Engineer]

On Mar 11, 10:45 am, Patrick Turner wrote:
coffeedj wrote:

I just returned from a far east trip and managed to put in a couple of days
in Hong Kong--visiting the DYI shops. There were some interesting points
learned.

First--we can get most of the DYI stuff for better or equal price in the
USA.

But is there such a thing as a DIY shop in HK?

Does this mean hobbyists making amplifiers after work at home are
selling what they have made
for themselves?

The one exception is transformers, but without knowledge of the
quality of the local brands it was hard to value these.

From what I have seen and tested on my bench, Chinese OPTs are
equal to the very worst quality produced by western nations in 1955,
with poor iron, cores not large enough for the watts, too few turns
and low primary inductances, saturation at too high a frequency,
poor HF range, and high leakage inductance and shunt capacitance,
and lord know what sort of insulation or winding practices have been
employed.

However, some OPT would be fine, such as those made for Quad amplifiers
which have been made there since IAG bought quad some years ago.
Consonance amps may also have nice iron, but there is much crap there.

Second, most of

shops were pretty vanilla and not necessarily staffed by DYI hardcores.

Exactly what do you mean?

There were, however, a few very enjoyable divergences from this pattern. At
one shop I asked the owner for a specific vinyl I had been looking for (for
decades) and he sort of ignored me. Then as I started talking componets,
amps, speakers, and designs with him he lit up. Once he understood I was a
tube-o-phile and he pulled out the extremely rare vinyl from a pile behind
the desk and sold it to me! I guess I had to prove that I was worthy to buy
first.

Ah, so you have to foolaroundabit to get served.



The other interesting point was the degree of tube amp and vinyl interest in
Hong Kong.

Its huge; they like tubes.

Used vinyl shops abound, and new vinyl is also advertised and

available.

It seemed like every little used record or coffee shop I stopped

at had a sound system that was based on some newer chinese tube amp and a
record player. They are really into the tube sound and vinyl in HK.

Well they'd certainly get "tube sound" and it wouldn't necessarily be
all that wonderful
going on what i have seen and heard.

Made some great contacts--all in all an enjoyable side trip. Stayed at the
Cyberport Hotel--highly recommended for an experience in new asian cyber
community.

Many fellows have emigrated to Oz from HK and the Audiophile Society of
NSW has a large
contingent in its membership of asian born and Oz born asians who
take their music very seriously, and from what I have
experienced, they are not easy to please, and they do tend to like tubes
and
vinyl, as many of them have for 50 years so far.
I found the Society to be a very pleasant lot of guys to spend a sunday
with listening to music.

The number of young people re-discovering vinyl magic is
very small, but perhaps it is growing amoung discerning ppl
with enough time to spare to enjoy music.
Meanwhile, the local School of Music has had a very hard time this year
attracting
enough students to justify keeping the doors open and teachers employed,
and not many ppl want to perform; they mostly all just want to consume,
be rich, and have no time because of high house prices and demanding
girlfriends.
And don't forget the majority of ppl 25 have been raised on junk. Junk
food, junk TV shows,
and certainly junk pop music.

Patrick Turner.

My company has branch service operations in Beijing and Shanghai (OK,
that's not HK!) staffed by some very smart service techs (industrial
electro-optical systems.) On a couple of occasions I have asked one
of them to search out a part for me since "it must be cheaper on
China" (but I've never asked about OPT's.) Not so! To date he has
drawn a blank in the street markets. I recall that he said the stuff
for sale in these markets is current "junky" modern consumer product
(and there are many pirated DVDs and CDs!) I once asked him to find a
stereo decoder chip for a vintage AM/FM receiver - he found it... but
at a higher price than our purchasing dept. found it here, FOB
Toronto, Canada!
Time to go back and check out the Chinese replacement tube market...
Cheers,
Roger

[robert casey]

Patrick Turner wrote:

coffeedj wrote:


First--we can get most of the DYI stuff for better or equal price in the
USA.


But is there such a thing as a DIY shop in HK?

Does this mean hobbyists making amplifiers after work at home are
selling what they have made
for themselves?

I think he means a shop that has tube amp parts sells and sells them to
DIYers.

The one exception is transformers, but without knowledge of the
quality of the local brands it was hard to value these.


From what I have seen and tested on my bench, Chinese OPTs are
equal to the very worst quality produced by western nations in 1955,
with poor iron, cores not large enough for the watts, too few turns
and low primary inductances, saturation at too high a frequency,
poor HF range, and high leakage inductance and shunt capacitance,
and lord know what sort of insulation or winding practices have been
employed.

See my post at http://audiokarma.org/forums/showthread.php?t=103925
where I used a pair of Chinese power transformers for OPTs. Low power
amps here. And yes, I took the lams apart and restacked them for the gap
you need for single ended work. And they turned out to be better than I
had reasonably expected, reasonable bass to at least 16KHz. With no
feedback other than what you might get with unbypassed cathodes and
ultralinear taps feeding screen grids. My ears probably don't miss
anything above that anymore anyway... :-) So I'd say that I got at least
mid-fi... These transformers had primaries for 277VAC and 120V (they
were designed for EXIT signs with self contained battery backup)(the
120V lead became the UL tap). After regapping, the primary inductance
measured about 6H. I think I just got lucky with these transformers,
other power transformers could have done much worse.

[Patrick Turner]

Engineer wrote:

On Mar 11, 10:45 am, Patrick Turner wrote:
coffeedj wrote:

I just returned from a far east trip and managed to put in a couple of days
in Hong Kong--visiting the DYI shops. There were some interesting points
learned.

First--we can get most of the DYI stuff for better or equal price in the
USA.

But is there such a thing as a DIY shop in HK?

Does this mean hobbyists making amplifiers after work at home are
selling what they have made
for themselves?

The one exception is transformers, but without knowledge of the
quality of the local brands it was hard to value these.

From what I have seen and tested on my bench, Chinese OPTs are
equal to the very worst quality produced by western nations in 1955,
with poor iron, cores not large enough for the watts, too few turns
and low primary inductances, saturation at too high a frequency,
poor HF range, and high leakage inductance and shunt capacitance,
and lord know what sort of insulation or winding practices have been
employed.

However, some OPT would be fine, such as those made for Quad amplifiers
which have been made there since IAG bought quad some years ago.
Consonance amps may also have nice iron, but there is much crap there.

Second, most of

shops were pretty vanilla and not necessarily staffed by DYI hardcores.

Exactly what do you mean?

There were, however, a few very enjoyable divergences from this pattern. At
one shop I asked the owner for a specific vinyl I had been looking for (for
decades) and he sort of ignored me. Then as I started talking componets,
amps, speakers, and designs with him he lit up. Once he understood I was a
tube-o-phile and he pulled out the extremely rare vinyl from a pile behind
the desk and sold it to me! I guess I had to prove that I was worthy to buy
first.

Ah, so you have to foolaroundabit to get served.



The other interesting point was the degree of tube amp and vinyl interest in
Hong Kong.

Its huge; they like tubes.

Used vinyl shops abound, and new vinyl is also advertised and

available.

It seemed like every little used record or coffee shop I stopped

at had a sound system that was based on some newer chinese tube amp and a
record player. They are really into the tube sound and vinyl in HK.

Well they'd certainly get "tube sound" and it wouldn't necessarily be
all that wonderful
going on what i have seen and heard.

Made some great contacts--all in all an enjoyable side trip. Stayed at the
Cyberport Hotel--highly recommended for an experience in new asian cyber
community.

Many fellows have emigrated to Oz from HK and the Audiophile Society of
NSW has a large
contingent in its membership of asian born and Oz born asians who
take their music very seriously, and from what I have
experienced, they are not easy to please, and they do tend to like tubes
and
vinyl, as many of them have for 50 years so far.
I found the Society to be a very pleasant lot of guys to spend a sunday
with listening to music.

The number of young people re-discovering vinyl magic is
very small, but perhaps it is growing amoung discerning ppl
with enough time to spare to enjoy music.
Meanwhile, the local School of Music has had a very hard time this year
attracting
enough students to justify keeping the doors open and teachers employed,
and not many ppl want to perform; they mostly all just want to consume,
be rich, and have no time because of high house prices and demanding
girlfriends.
And don't forget the majority of ppl 25 have been raised on junk. Junk
food, junk TV shows,
and certainly junk pop music.

Patrick Turner.

My company has branch service operations in Beijing and Shanghai (OK,
that's not HK!) staffed by some very smart service techs (industrial
electro-optical systems.) On a couple of occasions I have asked one
of them to search out a part for me since "it must be cheaper on
China" (but I've never asked about OPT's.) Not so! To date he has
drawn a blank in the street markets. I recall that he said the stuff
for sale in these markets is current "junky" modern consumer product
(and there are many pirated DVDs and CDs!) I once asked him to find a
stereo decoder chip for a vintage AM/FM receiver - he found it... but
at a higher price than our purchasing dept. found it here, FOB
Toronto, Canada!
Time to go back and check out the Chinese replacement tube market...
Cheers,
Roger

Gee, you'd never get work as a travel agent promoting Chinese
shopping opportunities :-)

But then I hate shopping for hi-fi gear, and I just walk out to my shed
and make what i want, knowing that going to China would be a monumental
waste of
a plane fare.

Patrick Turner.

[Phil Allison]

"robert casey"


See my post at http://audiokarma.org/forums/showthread.php?t=103925
where I used a pair of Chinese power transformers for OPTs. Low power amps
here. And yes, I took the lams apart and restacked them for the gap you
need for single ended work. And they turned out to be better than I had
reasonably expected, reasonable bass to at least 16KHz.


** Gee, that IS good bass.

How do you get it to go up that high ??



........ Phil

[Patrick Turner]

robert casey wrote:

Patrick Turner wrote:

coffeedj wrote:


First--we can get most of the DYI stuff for better or equal price in the
USA.


But is there such a thing as a DIY shop in HK?

Does this mean hobbyists making amplifiers after work at home are
selling what they have made
for themselves?

I think he means a shop that has tube amp parts sells and sells them to
DIYers.

Oh, you mean a shop like Radio Shack in the US, or like Dick Smith
Electronics or Jaycar in Oz,
where the cheapest lowest quality generic mass produced Taiwanese and
Chinese gear is sold
at prices well above the ex factory price?



The one exception is transformers, but without knowledge of the
quality of the local brands it was hard to value these.


From what I have seen and tested on my bench, Chinese OPTs are
equal to the very worst quality produced by western nations in 1955,
with poor iron, cores not large enough for the watts, too few turns
and low primary inductances, saturation at too high a frequency,
poor HF range, and high leakage inductance and shunt capacitance,
and lord know what sort of insulation or winding practices have been
employed.

See my post at http://audiokarma.org/forums/showthread.php?t=103925
where I used a pair of Chinese power transformers for OPTs.


I will NOT be visiting your site to see where you have used power
transformers for
OPT in an audio amplifier.



Low power
amps here. And yes, I took the lams apart and restacked them for the gap
you need for single ended work.


What a horrid way to build an amp!



And they turned out to be better than I
had reasonably expected, reasonable bass to at least 16KHz. With no
feedback other than what you might get with unbypassed cathodes and
ultralinear taps feeding screen grids. My ears probably don't miss
anything above that anymore anyway... :-) So I'd say that I got at least
mid-fi... These transformers had primaries for 277VAC and 120V (they
were designed for EXIT signs with self contained battery backup)(the
120V lead became the UL tap). After regapping, the primary inductance
measured about 6H. I think I just got lucky with these transformers,
other power transformers could have done much worse.


Good luck with mid-fi.

I am only interested in hi-fi.

Should you ever wish to use a mains tranny for an SE amp for hi-fi,
start with at least a KT88 strapped in triode,
then consider a choke feed to the anode, then capacitor couple the anode
to a 240V : 10V
100VA rated TOROIDAL transformer. This should give you the right
load for the tube with 8 ohms connected to the 10V winding, and the
right anode load
and good bandwidth without NFB.

You don't have to pull the lams out of an existing core and re-stack
them.

But you will need a 20H @ 80mA choke and toroidal tranny, and perhaps
you will need to
wind on the 10V winding, or a couple that are in parallel, or remove the
existing
secondaries and re-wind them because 240V : 10V mains trannies are not a
standard item
in any shops I know of.

E&I mains tannies usually have appalling bandwidth, and do not
provide the correct load for the anode unless you use 110V : 5V,
or 240V : 6.3V, but I would never dream of doing it.

Patrick Turner.

[robert casey]

I think he means a shop that has tube amp parts sells and sells them to
DIYers.


Oh, you mean a shop like Radio Shack in the US, or like Dick Smith
Electronics or Jaycar in Oz,
where the cheapest lowest quality generic mass produced Taiwanese and
Chinese gear is sold
at prices well above the ex factory price?



No, a real shop with real parts. Yes, they are hard to find anymore,
but there are a few in Silicon Valley. Radio Shack hardly has crap
parts, much less anything decent anymore. If they ever did... "Whatever
you wanted, we have a cell phone for you..."


Good luck with mid-fi.

I am only interested in hi-fi.

Well, it was a step above squalid state... :-)

[robert casey]

And they turned out to be better than I had
reasonably expected, reasonable bass to at least 16KHz.



** Gee, that IS good bass.

How do you get it to go up that high ??



....... Phil



:-) Well, it helps to have bat ears. 16KHz is bass to them... :-)

Anyway, I get to maybe 40Hz of bass. Not great bass, but some bass...
This thing ain't gonna hold a candle to a serious stereo, but it came
out better than I expected....

Well, next week is bass fishing season. Maybe I can get more bass
then... :-) '))))

[Patrick Turner]

I've been doing some work with, uh, 'not OPT' transformers too and I'd
be interested to hear how much power you can get on the bass end.

The simulations I've done are a bit deceptive in that they'll indicate
a certain frequency response but you run into increasingly heavy
current demand as the impedance falls off and they don't consider that
in the 'frequency response' curves.

On the other hand, when running music through the things the bass
isn't usually at 'full power' either.

The bass waves are the largest amplitude in music, and
distortion at bass F is the highest as a result in the tube
and also in the OPT because the F approaches saturation F.

If the speakers are sensitive, then indeed low power is used, so the
primary voltage is low on the "OPT" so the tranny doesn't saturate.
The saturation F is dependant on the voltage applied and F, and occurs
with or without a load attatched; it is a voltage caused phenomena,
independant of power production.
but mains trannies have low primary inductance which shunts the load,
so if they don't saturate, they shunt the load anyway....

A 110V mains tranny will saturate usually at about 125Vrms, 60Hz,
so at 30Hz the saturation occurs at around 63V only.
Or at 120Hz, Fsat is at around 250V.
To reduce the Fsat and increase the voltage at which Fsat occurs,
many more primary turns need to be used, or a much bigger core, or both.

Using 240V x 50Hz rated mains trannies helps the situation.
Mains trannies could be OK for a guitar amp where wide response isn't
needed,
and the more distortion the better.

Patrick Turner.

[Patrick Turner]

robert casey wrote:


I think he means a shop that has tube amp parts sells and sells them to
DIYers.


Oh, you mean a shop like Radio Shack in the US, or like Dick Smith
Electronics or Jaycar in Oz,
where the cheapest lowest quality generic mass produced Taiwanese and
Chinese gear is sold
at prices well above the ex factory price?



No, a real shop with real parts. Yes, they are hard to find anymore,
but there are a few in Silicon Valley. Radio Shack hardly has crap
parts, much less anything decent anymore. If they ever did... "Whatever
you wanted, we have a cell phone for you..."

Gone are the days when I could walk into the front door of a local
factory
which had a counter for sales to the public for their output trannies in
3 different grades and
many different impedances, and with all the chokes and power trannies
you could wish for.
All that stopped by 1970.

Patrick Turner.

e


Good luck with mid-fi.

I am only interested in hi-fi.

Well, it was a step above squalid state... :-)

[robert casey]

I've been doing some work with, uh, 'not OPT' transformers too and I'd
be interested to hear how much power you can get on the bass end.

The simulations I've done are a bit deceptive in that they'll indicate
a certain frequency response but you run into increasingly heavy
current demand as the impedance falls off and they don't consider that
in the 'frequency response' curves.

On the other hand, when running music through the things the bass
isn't usually at 'full power' either.


The bass waves are the largest amplitude in music, and
distortion at bass F is the highest as a result in the tube
and also in the OPT because the F approaches saturation F.

If the speakers are sensitive, then indeed low power is used, so the
primary voltage is low on the "OPT" so the tranny doesn't saturate.
The saturation F is dependant on the voltage applied and F, and occurs
with or without a load attatched; it is a voltage caused phenomena,
independant of power production.
but mains trannies have low primary inductance which shunts the load,
so if they don't saturate, they shunt the load anyway....

A 110V mains tranny will saturate usually at about 125Vrms, 60Hz,
so at 30Hz the saturation occurs at around 63V only.
Or at 120Hz, Fsat is at around 250V.
To reduce the Fsat and increase the voltage at which Fsat occurs,
many more primary turns need to be used, or a much bigger core, or both.

The transformers I used have primaries designed to operate on 277VAC
60Hz, an industrial voltage commonly used in large buildings and
factories here in the USA. So thus at 30Hz, saturation should happen
around 140VAC. But this would be before I regapped the transformers, as
I built a single ended amp. To avoid core saturation from the DC plate
current. Measuring the stock primary inductance, I get 27H. After I
restacked the lams, it's now 6H. At the power levels I'm running, just
2 Watts, that would produce about 115VAC peak to peak variation of B+ as
seen on the tube plate, on the primary. B+ is 115VDC. Ignoring the DC,
the RMS of the AC works out to about 41VAC. 30Hz is not mega-bass, but
for what I wanted, it's sufficient for this project. Also, I'm not
running this amp at ear splitting lease breaking volume....

[Patrick Turner]

robert casey wrote:

I've been doing some work with, uh, 'not OPT' transformers too and I'd
be interested to hear how much power you can get on the bass end.

The simulations I've done are a bit deceptive in that they'll indicate
a certain frequency response but you run into increasingly heavy
current demand as the impedance falls off and they don't consider that
in the 'frequency response' curves.

On the other hand, when running music through the things the bass
isn't usually at 'full power' either.


The bass waves are the largest amplitude in music, and
distortion at bass F is the highest as a result in the tube
and also in the OPT because the F approaches saturation F.

If the speakers are sensitive, then indeed low power is used, so the
primary voltage is low on the "OPT" so the tranny doesn't saturate.
The saturation F is dependant on the voltage applied and F, and occurs
with or without a load attatched; it is a voltage caused phenomena,
independant of power production.
but mains trannies have low primary inductance which shunts the load,
so if they don't saturate, they shunt the load anyway....

A 110V mains tranny will saturate usually at about 125Vrms, 60Hz,
so at 30Hz the saturation occurs at around 63V only.
Or at 120Hz, Fsat is at around 250V.
To reduce the Fsat and increase the voltage at which Fsat occurs,
many more primary turns need to be used, or a much bigger core, or both.

The transformers I used have primaries designed to operate on 277VAC
60Hz, an industrial voltage commonly used in large buildings and
factories here in the USA. So thus at 30Hz, saturation should happen
around 140VAC. But this would be before I regapped the transformers, as
I built a single ended amp.

Chances are that with the gapping, the dc magnnetization you have isn't
more than
0.6Telsa, leaving another 0.6T for the ac flux which sits on top of the
dc flux
to the max is 1.2T.

So even with the gapping, and far fewer "turns per volt"
than one would use for a hi-fi amp, you will stull get audio to
work with the transformer.

To avoid core saturation from the DC plate
current. Measuring the stock primary inductance, I get 27H. After I
restacked the lams, it's now 6H.

The P inductance will start to become a serious shunting impedance to
the amp
power when the L ractance = the load.

So if your load was 4k for the anode, the 6H reactance = 4k at 106Hz,
and its worse at
low levels because inductance falls with signal voltage applied.

This means that perhaps you have 4 watts into 4 k at 1 kHz at clipping,
which is 126Vrms across the primary, but overloading and clipping
will appear at 150Hz, and the power bandwidth will be from 150Hz
upwards.
But when Va = 40V, PO = 0.4 watts, and perhaps all you use, so the
amp will produce enough power without early overload and roll off if
there is NFB to make sure it does.

2 Watts, that would produce about 115VAC peak to peak variation of B+ as
seen on the tube plate, on the primary. B+ is 115VDC. Ignoring the DC,
the RMS of the AC works out to about 41VAC. 30Hz is not mega-bass, but
for what I wanted, it's sufficient for this project. Also, I'm not
running this amp at ear splitting lease breaking volume....


You have it sussed then.

To achieve more, you'd need to consider real purpose made transformers
with many more turns per
volt and some interleaving to extend the HF.

There rae many OPT I have seen in old AM radios with a 6BQ5
that make only 5 watts, and have saturation at 50Hz. at the 1khz
clipping level.

But at 25hz and 1/4 of the power they are fine, and with a sensitive
speaker such as a horn there
is more than enough power.

The first amps I built seriously were around this type of old junk, I
still have the radio
and it sounds well.
The gapped OPT were just one primary wound over the secondary, and I
found room for a second secondary
which dramatically extended the bandwidth to 80khz and allowed NFB and
the sound became
very good indeed, despite OPT limitations.

5 watts isn't enough for my hi-fi speakers and I need 20 watts at least.

Patrick Turner.

[tubegarden]

On Mar 12, 12:54?am, Patrick Turner wrote:

5 watts isn't enough for my hi-fi speakers and I need 20 watts at least.

Patrick Turner.


Hi Rats!

I have horns from Dr. Bruce Edgar I bartered for them ... the
drivers were built by Nick McKinney, before he ran off screaming into
the insurance jungles. 15" with 4 ohm Z, which is considerably
increased by the horns. Somewhere around 105dB/W/M. My little SE amps
drive them just fine.

I like what I hear. I do not find it fun to attack others with
different approaches. Well, except Eyesore, who thinks having his head
up his fundament is enlightenment In a sense, it may be, for
him ...

We get grouchy as our bodies decompose. Meds help, some. We often die
before our verbal, or typed, abuses drive anyone to suicide.

The Music is much better than our rude lyrics. Let us give thanks ...

Happy Ears!
Al

[robert casey]

The P inductance will start to become a serious shunting impedance to
the amp
power when the L ractance = the load.

So if your load was 4k for the anode, the 6H reactance = 4k at 106Hz,
and its worse at
low levels because inductance falls with signal voltage applied.

It's more like 2.5K of reactance. Which would make it more like 66Hz.
Still not megabass. :-)

This means that perhaps you have 4 watts into 4 k at 1 kHz at clipping,
which is 126Vrms across the primary, but overloading and clipping
will appear at 150Hz, and the power bandwidth will be from 150Hz
upwards.
But when Va = 40V, PO = 0.4 watts, and perhaps all you use, so the
amp will produce enough power without early overload and roll off if
there is NFB to make sure it does.


2 Watts, that would produce about 115VAC peak to peak variation of B+ as
seen on the tube plate, on the primary. B+ is 115VDC. Ignoring the DC,
the RMS of the AC works out to about 41VAC. 30Hz is not mega-bass, but
for what I wanted, it's sufficient for this project. Also, I'm not
running this amp at ear splitting lease breaking volume....



You have it sussed then.

To achieve more, you'd need to consider real purpose made transformers
with many more turns per
volt and some interleaving to extend the HF.

I'm continuing to look for a pair of real OPTs that aren't physically
too large (I have somewhat limited space). But I don't think anyone
makes 5 watt hifi OPTs. Well, not for mega $... :-) I've seen approx 30
watt ones, but they are too large.

[- - : R A T B o y : - -]

"robert casey" wrote in message
link.net...

... Well, next week is bass fishing season. Maybe I can get more bass
then... :-) '))))

Do you use a treble hook?!!

[robert casey]

I'm continuing to look for a pair of real OPTs that aren't physically
too large (I have somewhat limited space). But I don't think anyone
makes 5 watt hifi OPTs. Well, not for mega $... :-) I've seen approx 30
watt ones, but they are too large.



Found and bought a pair off ebay. We'll see how they do once I get
them. claimed to spec:
Primary impedance is 3000 Ohm (3K) , Primary current 100 mA, DC
resistance is 300 ohms, 20 Henrys
Secondary is 8 ohms and is conservatively rated for 10 watts continuous.
Frequency response is 20 Hz to 100 kHz +/- 1 db at 1 watt, tested on
Hewlett Packard audio analyzer.
Each transformer has the insulation Hipot tested to 3000 Volts DC.
Constructed with high grade M6 grain oriented silicon steel laminations
for excellent low frequency response and low distortion.
Primary and secondary interleaved for excellent high frequency response.
Core has an air gap for single ended operation.
Made by TRANSCENDAR TRANSFORMERS

Dropped about $89 for a pair, I'll see if they are any good or not...
seller has good feedback 100% and sells related items.

[Tom A.]

But is there such a thing as a DIY shop in HK?

I visited diyhifisupply, the guys behind www.diyhifisupply.com which
sell the Ella tube amp and since recently a preamp based on John
Broskie's Aikido. I bought a number of decent capacitators and
resistances there.
They had the Ella on demo (the new one with the remote) connected to
experimental diy speakers that used a small array of Jordan fullrange
units for all but the lowest bass. There was nothing wrong with that
sound.
I had to take an economy flight to singapore before flying back to
Europe, if I had flown back directly (in business class), I might have
been tempted to buy the Ella kit.

Tom