One of my regular vendors has a supply of inexpensive line matching SE
transformers. One 30W model lists for $11.00 and a 10W model for $6.00.

The 6V6 SE headphone amp that I built out of junkbox parts using iron from
an old Wollensak tape recorder turned out fine (I posted a schematic on ABSE
a few months ago). Problem is, there isn't a big supply of these Wollensak
transformers if I want to build more of them.

The thing I find attractive about the line transformers -- besides price --
is their multiple taps, which should add versatility to a headphone amp
design.

For example, the 10W has primary taps at 62.5, 125, 250, 500, 1000, 2000,
4000, & 8000 ohms. The secondary is a single 8 ohm winding.

My initial concerns include:

1. Frequency response at fractional wattages

2. Ability to tolerate DC current when used in an SE application

3. Insulation ratings of windings (obviously it can handle 70V!)

I guess what I'll do is build a test jig, install each tranny, and sweep the
frequency response. I'll probably use a low voltage power triode such as
the Russian 6C19Pi.

Any ideas / suggestions / caveats?

Jon Yaeger wrote:

One of my regular vendors has a supply of inexpensive line matching SE
transformers. One 30W model lists for $11.00 and a 10W model for $6.00.

The 6V6 SE headphone amp that I built out of junkbox parts using iron from
an old Wollensak tape recorder turned out fine (I posted a schematic on ABSE
a few months ago). Problem is, there isn't a big supply of these Wollensak
transformers if I want to build more of them.

The thing I find attractive about the line transformers -- besides price --
is their multiple taps, which should add versatility to a headphone amp
design.

For example, the 10W has primary taps at 62.5, 125, 250, 500, 1000, 2000,
4000, & 8000 ohms. The secondary is a single 8 ohm winding.

My initial concerns include:

1. Frequency response at fractional wattages

Assume 10 watts can be applied to the 8k input, or 282 vrms across the primary.

The applied voltage to the rest of the taps will be lower as you come down the
taps.
Only 25 volts can exist at the 62.5 ohm taps.

Expect winding losses to be high, Fsaturation to be high at 10 watts,
and poor F response.

Set one up and measure it carefully.



2. Ability to tolerate DC current when used in an SE application

Is there a gap? if not you will have to use it in a parafeed topology
with choke feed to the anode, and cap drive to the OPT.


3. Insulation ratings of windings (obviously it can handle 70V!)

Maybe its ok, apply 3,000v to the primary via a string of 1M resistors from a
suitable
supply with the secondary grounded.
If there is no drop in the applied voltage after 4 minutes, maybe the trannies
are OK,
and no leakage is likely.


I guess what I'll do is build a test jig, install each tranny, and sweep the
frequency response. I'll probably use a low voltage power triode such as
the Russian 6C19Pi.

A 6BQ5 would be fine in triode. Parafeed would need
you to have a choke of about 40H, and a 10 uf cap to feed the
8k tranny winding.
The 8k to 8 ohms ratio would be OK for head phones.

Patrick Turner.



Any ideas / suggestions / caveats?

Those transformers are designed for use on constant voltage PA systems. The
one you discuss is for use on a 25 volt system; others were made for 70.7
volt systems. The intent was that you could run wires all around a building
and tap off the necessary power at each point, just like using light bulbs.
At the 25 volt design voltage, the 62.5 ohm tap would provide 10 watts of
audio; the higher impedance taps lesser amounts. That is where the 10 watt
rating comes from.

These things are purely for PA use, are designed for no DC, and, in general,
were not designed with fidelity in mind. That is not to say that they won't
work for your purpose. but don't get your expectations up. I wouldn't worry
to much about the voltage rating, it's hard to make enamel wire break down
much below 1000 volts or so.

"Jon Yaeger" wrote in message
...
One of my regular vendors has a supply of inexpensive line matching SE
transformers. One 30W model lists for $11.00 and a 10W model for $6.00.

The 6V6 SE headphone amp that I built out of junkbox parts using iron from
an old Wollensak tape recorder turned out fine (I posted a schematic on
ABSE
a few months ago). Problem is, there isn't a big supply of these
Wollensak
transformers if I want to build more of them.

The thing I find attractive about the line transformers -- besides
price --
is their multiple taps, which should add versatility to a headphone amp
design.

For example, the 10W has primary taps at 62.5, 125, 250, 500, 1000, 2000,
4000, & 8000 ohms. The secondary is a single 8 ohm winding.

My initial concerns include:

1. Frequency response at fractional wattages

2. Ability to tolerate DC current when used in an SE application

3. Insulation ratings of windings (obviously it can handle 70V!)

I guess what I'll do is build a test jig, install each tranny, and sweep
the
frequency response. I'll probably use a low voltage power triode such as
the Russian 6C19Pi.

Any ideas / suggestions / caveats?

Some criminal imbecile wrote:


Assume 10 watts can be applied to the 8k input, or 282 vrms across the
primary.



** The maximum is 70 volts or possibly 100 volts rms.




............ Phil

On Mon, 18 Apr 2005 09:55:17 +1000, "Phil Allison"
wrote:


Some criminal imbecile wrote:


........... Phil


Oh Phil dear, I worry about you still being at home.
See look what happens when you don't go out!
You pick fights with strangers! You Naughty Boy!
You used to be so well behaved.The Marist Brothers told me so.They
said that you were always quick to catch onto new things, and you
were always one of the first to go down on your knees.You always used
to pray alot, especially in your bedroom.
I tried to get you a job.Did Mr.Rio call you? I gave him your
phone number. You didn't turn him down did you?
How can I get you out of your shack.
Why can't you be well behaved like Paul?
You are such a worry these days.
Love mummy.

"Jon Yaeger" wrote in message
...
One of my regular vendors has a supply of inexpensive line matching SE
transformers. One 30W model lists for $11.00 and a 10W model for $6.00.

The 6V6 SE headphone amp that I built out of junkbox parts using iron from
an old Wollensak tape recorder turned out fine (I posted a schematic on
ABSE
a few months ago). Problem is, there isn't a big supply of these
Wollensak
transformers if I want to build more of them.

The thing I find attractive about the line transformers -- besides
price --
is their multiple taps, which should add versatility to a headphone amp
design.

For example, the 10W has primary taps at 62.5, 125, 250, 500, 1000, 2000,
4000, & 8000 ohms. The secondary is a single 8 ohm winding.

My initial concerns include:

1. Frequency response at fractional wattages

2. Ability to tolerate DC current when used in an SE application

3. Insulation ratings of windings (obviously it can handle 70V!)

I guess what I'll do is build a test jig, install each tranny, and sweep
the
frequency response. I'll probably use a low voltage power triode such as
the Russian 6C19Pi.

Any ideas / suggestions / caveats?


Probably your best bet is to drive the trannies in PP to avoid DC core
saturation.
The winding ratio for the 8000? tap gives N = sqrt(8000/8) = 31.6
Winding ratio for the 2000? tap is 15.8, exactly half of the above figure.
So, a plate--supply--plate hookup must be on the 0-2000-8000 taps.

Backwards, primary Z for an 8? load will be 31,6² x 8 = 8k.
Or, Zp with a 4? load on the secondary will be 31,6² x 4 = 4k.
With PP on the 0-1000-4000 taps Zp is 4k respectively 2k and so on,
giving a lowest possible Zp of 125? on the 0-62.5-250 taps.
Enough room for experiments, I'd tend to use the full primary though.
Also, given the limited-fi properties of line trannies, I'd tend to use a 4?
load i.s.o. 8? to extend low frequency roll off a bit further down the f
axis.

For SE an alternative may be to disassemble the core and re-assemble
into a single E and I stack with an air gap between the two.

Rgds,
Jan.

Jon Yaeger wrote:

One of my regular vendors has a supply of inexpensive line matching SE
transformers. One 30W model lists for $11.00 and a 10W model for $6.00.

The 6V6 SE headphone amp that I built out of junkbox parts using iron from
an old Wollensak tape recorder turned out fine (I posted a schematic on ABSE
a few months ago). Problem is, there isn't a big supply of these Wollensak
transformers if I want to build more of them.

The thing I find attractive about the line transformers -- besides price --
is their multiple taps, which should add versatility to a headphone amp
design.

For example, the 10W has primary taps at 62.5, 125, 250, 500, 1000, 2000,
4000, & 8000 ohms.

Jon- With those windings it would be possible to run PP if you like. For
example, if you were to run the 8K winding plate-to-plate the CT is at 2K. Try
that.

It is most unlikely there will be an air gap, since in ordinary use these
transformers would never see DC. Not recommended for SE use, altho they would
work. The LF will roll off rather quickly.

JLS

The secondary is a single 8 ohm winding.

My initial concerns include:

1. Frequency response at fractional wattages

2. Ability to tolerate DC current when used in an SE application

3. Insulation ratings of windings (obviously it can handle 70V!)

I guess what I'll do is build a test jig, install each tranny, and sweep the
frequency response. I'll probably use a low voltage power triode such as
the Russian 6C19Pi.

Any ideas / suggestions / caveats?

Jon Yaeger wrote:

One of my regular vendors has a supply of inexpensive line matching SE
transformers. One 30W model lists for $11.00 and a 10W model for $6.00.

The 6V6 SE headphone amp that I built out of junkbox parts using iron from
an old Wollensak tape recorder turned out fine (I posted a schematic on ABSE
a few months ago). Problem is, there isn't a big supply of these Wollensak
transformers if I want to build more of them.

The thing I find attractive about the line transformers -- besides price --
is their multiple taps, which should add versatility to a headphone amp
design.

For example, the 10W has primary taps at 62.5, 125, 250, 500, 1000, 2000,
4000, & 8000 ohms.

Jon- With those windings it would be possible to run PP if you like. For
example, if you were to run the 8K winding plate-to-plate the CT is at 2K. Try
that.

It is most unlikely there will be an air gap, since in ordinary use these
transformers would never see DC. Not recommended for SE use, altho they would
work. The LF will roll off rather quickly.

BTW, you could also do some interesting SE UL experiments!

JLS

The secondary is a single 8 ohm winding.

My initial concerns include:

1. Frequency response at fractional wattages

2. Ability to tolerate DC current when used in an SE application

3. Insulation ratings of windings (obviously it can handle 70V!)

I guess what I'll do is build a test jig, install each tranny, and sweep the
frequency response. I'll probably use a low voltage power triode such as
the Russian 6C19Pi.

Any ideas / suggestions / caveats?

John Stewart wrote:

Jon Yaeger wrote:

One of my regular vendors has a supply of inexpensive line matching SE
transformers. One 30W model lists for $11.00 and a 10W model for $6.00.

The 6V6 SE headphone amp that I built out of junkbox parts using iron from
an old Wollensak tape recorder turned out fine (I posted a schematic on ABSE
a few months ago). Problem is, there isn't a big supply of these Wollensak
transformers if I want to build more of them.

The thing I find attractive about the line transformers -- besides price --
is their multiple taps, which should add versatility to a headphone amp
design.

For example, the 10W has primary taps at 62.5, 125, 250, 500, 1000, 2000,
4000, & 8000 ohms.

Jon- With those windings it would be possible to run PP if you like. For
example, if you were to run the 8K winding plate-to-plate the CT is at 2K. Try
that.

It is most unlikely there will be an air gap, since in ordinary use these
transformers would never see DC. Not recommended for SE use, altho they would
work. The LF will roll off rather quickly.

Probably the HF and LF both roll off a bit too early.
But you are right about the 2k tap, it should be the CT of the tranny,
but maybe the primary wire guage changes along the winding.

SE use is no problem if parafeed is used.

Patrick Turner.



JLS

The secondary is a single 8 ohm winding.

My initial concerns include:

1. Frequency response at fractional wattages

2. Ability to tolerate DC current when used in an SE application

3. Insulation ratings of windings (obviously it can handle 70V!)

I guess what I'll do is build a test jig, install each tranny, and sweep the
frequency response. I'll probably use a low voltage power triode such as
the Russian 6C19Pi.

Any ideas / suggestions / caveats?

On Sun, 17 Apr 2005 12:17:06 -0400, Jon Yaeger wrote:

One of my regular vendors has a supply of inexpensive line matching SE
transformers. One 30W model lists for $11.00 and a 10W model for $6.00.

The 6V6 SE headphone amp that I built out of junkbox parts using iron from
an old Wollensak tape recorder turned out fine (I posted a schematic on ABSE
a few months ago). Problem is, there isn't a big supply of these Wollensak
transformers if I want to build more of them.

The thing I find attractive about the line transformers -- besides price --
is their multiple taps, which should add versatility to a headphone amp
design.

For example, the 10W has primary taps at 62.5, 125, 250, 500, 1000, 2000,
4000, & 8000 ohms. The secondary is a single 8 ohm winding.

My initial concerns include:

1. Frequency response at fractional wattages

2. Ability to tolerate DC current when used in an SE application

3. Insulation ratings of windings (obviously it can handle 70V!)

I guess what I'll do is build a test jig, install each tranny, and sweep the
frequency response. I'll probably use a low voltage power triode such as
the Russian 6C19Pi.

Any ideas / suggestions / caveats?

I've used various 'junkbox' line transformers as spk transformers in SE amps...
mileage varies!

Some worked , some didn't work at all (made sparking noises)...

One thing for sure - compared to a proper Hammond output transformer - they all
sounded like ****!