audio transformer, about 30W size, easily available?

M

mw

Guest
Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog ad?

Thanks for any ideas,
mw
 
"mw" <mw@avoidspam.com> wrote in message
news:kv6He.27$3M4.2@newssvr27.news.prodigy.net...
Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog
ad?

Thanks for any ideas,
mw
Click to expand...
Good luck finding anything with high frequency response, 4K to 17K That
almost has to be ferrite
 
jabara wrote:
"mw" <mw@avoidspam.com> wrote in message
news:kv6He.27$3M4.2@newssvr27.news.prodigy.net...
Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog
ad?
Thanks for any ideas,
mw

Good luck finding anything with high frequency response, 4K to 17K That
almost has to be ferrite
Click to expand...
?!?!?!?!?!

Then how do all the iron-cored transformer coupled tube amps acheive
full 20-20kHz response?




--
_____________________
Christopher R. Carlen
crobc@bogus-remove-me.sbcglobal.net
SuSE 9.1 Linux 2.6.5
 
you might try http://www.edcorusa.com/downloads/other.htm


"mw" <mw@avoidspam.com> wrote in message
news:kv6He.27$3M4.2@newssvr27.news.prodigy.net...
Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble and
tried to use a power transformer, but that's not working well because they
are designed to work well at 60 Hz and the ones I've tried roll off very
fast at higher frequencies. This isn't an audiophile project, but I want
something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those "classic
tube audio transformers" that go for $100. I can't use the little audio
transformers sold in Digikey because their power handling is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog
ad?

Thanks for any ideas,
mw
Click to expand...
 
On Sun, 31 Jul 2005 15:54:56 GMT, mw <mw@avoidspam.com> wrote:

Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog ad?

Thanks for any ideas,
mw
Click to expand...

Google "70 volt line transformer". Scads of good hits.

John
 
mw wrote:
Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog ad?

Thanks for any ideas,
mw
Click to expand...
http://www.hammondmfg.com/5cindex.htm might be what you want.
--
Link to my "Computers for disabled Veterans" project website deleted
after threats were telephoned to my church.

Michael A. Terrell
Central Florida
 
John Larkin wrote:
Google "70 volt line transformer". Scads of good hits.
Click to expand...
That's the problem... too many hits. This seems to be a simple issue
where today's manufacturers don't bother to give any detailed info.
Just advertisements and surface level details.

I'd like to find a spec sheet showing some details before spending more
money... something with freq response, dB losses, watts, weight.

The closest I've seen to what I am looking for is the PA transformers on
the Hammond page mentioned by Michael A. Terrell (thanks, Michael).
I'll probably spring for the 117F32. Not perfect, but close. Or maybe
the 119Y30... wish Hammond had more details on the web site.

mw
 
How about some more details on what you want. What primary and secondary
impedance? what taps, if any? how much unbalanced DC in the primary,
etc.etc.

The standard 70 volt stuff is probably OK for 100 - 5000 Hz, with no DC in
the primary.

"mw" <mw@avoidspam.com> wrote in message
news:Ee9He.39$3M4.29@newssvr27.news.prodigy.net...
John Larkin wrote:
Google "70 volt line transformer". Scads of good hits.

That's the problem... too many hits. This seems to be a simple issue
where today's manufacturers don't bother to give any detailed info.
Just advertisements and surface level details.

I'd like to find a spec sheet showing some details before spending more
money... something with freq response, dB losses, watts, weight.

The closest I've seen to what I am looking for is the PA transformers on
the Hammond page mentioned by Michael A. Terrell (thanks, Michael).
I'll probably spring for the 117F32. Not perfect, but close. Or maybe
the 119Y30... wish Hammond had more details on the web site.

mw
Click to expand...
 
"Chris Carlen" <crobc@BOGUSFIELD.sbcglobal.net> wrote in message
news:dcj0pe02maq@news4.newsguy.com...
jabara wrote:
"mw" <mw@avoidspam.com> wrote in message
news:kv6He.27$3M4.2@newssvr27.news.prodigy.net...
Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog
ad?
Thanks for any ideas,
mw

Good luck finding anything with high frequency response, 4K to 17K That
almost has to be ferrite

?!?!?!?!?!

Then how do all the iron-cored transformer coupled tube amps acheive full
20-20kHz response?
Click to expand...
It won't be small. I still have a 25 - 30 W ultralinear output transformer
that I used with a pair of 7034? tubes. It is about 4"square and 5 - 6
inches tall. Must weigh about 5 pounds.

Tam
--
_____________________
Christopher R. Carlen
crobc@bogus-remove-me.sbcglobal.net
SuSE 9.1 Linux 2.6.5
Click to expand...
 
Chris Carlen <crobc@BOGUSFIELD.sbcglobal.net> wrote:

jabara wrote:
"mw" <mw@avoidspam.com> wrote in message
news:kv6He.27$3M4.2@newssvr27.news.prodigy.net...
Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog
ad?
Thanks for any ideas,
mw

Good luck finding anything with high frequency response, 4K to 17K That
almost has to be ferrite

?!?!?!?!?!

Then how do all the iron-cored transformer coupled tube amps acheive
full 20-20kHz response?
Click to expand...
Thinner laminations than power transformers and interleaved windings.

Even top-quality laminations loose interest in the proceedings at higher
frequencies and the transformer effectively becomes air-coupled. The
tighter the windings are interleaved, the better the HF coupling.

With valve O/P transformers you have high primary impedances and lots of
turns, which gives lots of stray capacitance and the possibility of
self-resonance all over the place. That is another reason for splitting
up the windings.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
 
mw wrote:

Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog ad?
Click to expand...
You don't say what the primary side drive is - i.e. tube or transistor.

If it's transistor and you want and you want something like a 1:1 transformer
you can pretty much forget it unless you want to pay for a custom wound job.
There's simply no market for such things.

70V transformers are designed to be loaded with quite a high impedance - no
good for 8 ohms. Their audio performance is typically pretty lacklustre too.

What on earth do you *want* a transfomer for anyway with all the limitations it
entails ?

Graham
 
"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42ED6249.D87912CE@hotmail.com...
mw wrote:

Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog
ad?

You don't say what the primary side drive is - i.e. tube or transistor.

If it's transistor and you want and you want something like a 1:1
transformer
you can pretty much forget it unless you want to pay for a custom wound
job.
There's simply no market for such things.

70V transformers are designed to be loaded with quite a high impedance -
no
good for 8 ohms.
Click to expand...
Could you clarify this for me? Exactly what impedance should they be loaded
with?
 
BFoelsch wrote:

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42ED6249.D87912CE@hotmail.com...
mw wrote:

Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog
ad?

You don't say what the primary side drive is - i.e. tube or transistor.

If it's transistor and you want and you want something like a 1:1
transformer
you can pretty much forget it unless you want to pay for a custom wound
job.
There's simply no market for such things.

70V transformers are designed to be loaded with quite a high impedance -
no
good for 8 ohms.

Could you clarify this for me? Exactly what impedance should they be loaded
with?
Click to expand...
It's calculated from first principles.

If it's 30W you want and the voltage is 70V then I = W/V = 30/70 = ~ 0.43

Zl = V / I = 70 / 0.43 = ~ 163 ohms

70 V line sytems are commonly used for distributed audio with multiple loads.
Each transformer is designed for a given wattage. If you have a 30W amplifer
you can load it with up to 30W worth of loads.

Graham
 
"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42ED88D1.242CA476@hotmail.com...
BFoelsch wrote:

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42ED6249.D87912CE@hotmail.com...
mw wrote:

Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've
tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or
Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a
catalog
ad?

You don't say what the primary side drive is - i.e. tube or transistor.

If it's transistor and you want and you want something like a 1:1
transformer
you can pretty much forget it unless you want to pay for a custom wound
job.
There's simply no market for such things.

70V transformers are designed to be loaded with quite a high
impedance -
no
good for 8 ohms.

Could you clarify this for me? Exactly what impedance should they be
loaded
with?

It's calculated from first principles.

If it's 30W you want and the voltage is 70V then I = W/V = 30/70 = ~ 0.43

Zl = V / I = 70 / 0.43 = ~ 163 ohms
Click to expand...
Yes, but you are calculating the impedance that the transformer places
across the 70 volt line. You specifically state that

70V transformers are designed to be loaded with quite a high
impedance -
no
good for 8 ohms.
Click to expand...
What do your calculations do to support your point? You haven't mentioned a
single word about the transformer load (secondary winding) other than to say
that it must be other than 8 ohms. What does the reflected primary impedance
have to do with the optimum secondary load, and why are 70 volt transformers
no good for 8 ohm loads?

I'm still confused. Why can't a transformer with a 167 ohm primary be
designed to match an 8 ohm speaker?

???????????????
 
mw wrote:
John Larkin wrote:
Google "70 volt line transformer". Scads of good hits.

That's the problem... too many hits. This seems to be a simple issue
where today's manufacturers don't bother to give any detailed info.
Just advertisements and surface level details.

I'd like to find a spec sheet showing some details before spending
more money... something with freq response, dB losses, watts, weight.

The closest I've seen to what I am looking for is the PA transformers
on the Hammond page mentioned by Michael A. Terrell (thanks, Michael).
I'll probably spring for the 117F32. Not perfect, but close. Or
maybe the 119Y30... wish Hammond had more details on the web site.

mw
http://www.sowter.co.uk/
Click to expand...
--
ciao Ban
Bordighera, Italy
 
no_one wrote:

you might try http://www.edcorusa.com/downloads/other.htm
Click to expand...
That's exactly what I was looking for... amazing... I was hoping such a
thing would exist.

EM4045 30W audio transformer
input: 70 V
output: 8 ohms
freq response: 50 to 15kHz, +/- 1 dB (how do they do it?!)
insertion loss 0.5 dB
$21.88 (no minimum order!) (that's very competitive with the "no spec
and non-in stock" parts I've seen listed on the distributor's web sites)

Thanks!

mw
 
"mw" <mw@avoidspam.com> wrote in message
news:kv6He.27$3M4.2@newssvr27.news.prodigy.net...
Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a catalog
ad?

Thanks for any ideas,
mw
Click to expand...
I've used some mains toroids from Farnell in a push-pull pentode circuit and
achieved <10Hz to 7KHz. Is this good enough for you?

Graham Holloway
>
 
Graham Holloway wrote:
I've used some mains toroids from Farnell in a push-pull pentode circuit and
achieved <10Hz to 7KHz. Is this good enough for you?
Click to expand...
That's pretty good, especially the low end. Vendor and part number?

mw
 
"mw" <mw@avoidspam.com> wrote in message
news:vhnHe.232$3M4.151@newssvr27.news.prodigy.net...
Graham Holloway wrote:
I've used some mains toroids from Farnell in a push-pull pentode circuit
and
achieved <10Hz to 7KHz. Is this good enough for you?

That's pretty good, especially the low end. Vendor and part number?

mw
Click to expand...
Sorry, just checked and found I got them from RS Components (UK), Part No.
257-5017. They are 50VA mains toroids (2x12V secondaries, 2x120V primaries)
and I used two. The secondaries were paralleled with the centre tap formed
going to 0V. A 120V primary of one was placed in series with a 120V primary
of the other and vice versa. This enabled the correct ratio to be achieved
and to cancel the DC component in each valve.

Graham Holloway
 
BFoelsch wrote:

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42ED88D1.242CA476@hotmail.com...

BFoelsch wrote:

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42ED6249.D87912CE@hotmail.com...
mw wrote:

Hi,

Know of any easily available (inexpensive and stocked) 30W audio
transformer to couple to an 8 ohm speaker?

I am experimenting with a custom audio amplifier design that uses
tranformer coupling rather than the usual capacitors. I took a gamble
and tried to use a power transformer, but that's not working well
because they are designed to work well at 60 Hz and the ones I've
tried
roll off very fast at higher frequencies. This isn't an audiophile
project, but I want something a little better.

I want something I can get at a place like DigiKey or Newark or
Mouser,
not from a custom house or scrounging at hamfests or one of those
"classic tube audio transformers" that go for $100. I can't use the
little audio transformers sold in Digikey because their power handling
is too small.

Would one of those 70V PA distribution transformers work for this? Is
there a PA transformer vendor with real spec sheets, not just a
catalog
ad?

You don't say what the primary side drive is - i.e. tube or transistor.

If it's transistor and you want and you want something like a 1:1
transformer
you can pretty much forget it unless you want to pay for a custom wound
job.
There's simply no market for such things.

70V transformers are designed to be loaded with quite a high
impedance -
no
good for 8 ohms.

Could you clarify this for me? Exactly what impedance should they be
loaded
with?

It's calculated from first principles.

If it's 30W you want and the voltage is 70V then I = W/V = 30/70 = ~ 0.43

Zl = V / I = 70 / 0.43 = ~ 163 ohms


Yes, but you are calculating the impedance that the transformer places
across the 70 volt line. You specifically state that

70V transformers are designed to be loaded with quite a high
impedance -
no
good for 8 ohms.

What do your calculations do to support your point? You haven't mentioned a
single word about the transformer load (secondary winding) other than to say
that it must be other than 8 ohms.
Click to expand...
No I'm talking about the secondary ! The primary is unknown until the OP gives
some data.

What does the reflected primary impedance
have to do with the optimum secondary load, and why are 70 volt transformers
no good for 8 ohm loads?

I'm still confused. Why can't a transformer with a 167 ohm primary be
designed to match an 8 ohm speaker?
Click to expand...
No you twit ! That's the *SECONDARY* load impedance / voltage ! 160 odd ohms
isn't 8 ohms. Do you know nothing ?

Are you the original OP btw ?

Graham
 
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