| Author |
Message |
Michael
Guest
|
 Posted:
Mon Nov 28, 2005 5:35 pm Post subject:
240vac xformer and tube amp |
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|
I've been in electronics a long time but it's been years since I've messed
with tube stuff but I thought I "may" build a small guitar (practice) amp.
First question is...
Has anyone explored the possibility of using a simple (and generally
inexpensive) 120 to 240vac step up transformer with a solid state bridge
rectifier to get high voltage for a tube?
Is there a design/schematic someone can refer me to on a particular tube
that could operate on the voltage from this arrangement....I would imagine
you could get close to plus 280-290 volts or so under load?
|
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Doggone
Guest
|
| Posted:
Mon Nov 28, 2005 5:35 pm Post subject:
Re: 240vac xformer and tube amp |
|
|
"Michael" <newszz10@yahoo.com> wrote in news:g9adnVN87OBXhBbeRVn-
ig@comcast.com:
You need Duncan's very fine tools.
Go to:
http://www.duncanamps.com/software.html
And download PSU Designer. While you're there, you'll want to get the other
tools too. TDSL is my fav. You'd be hard pressed finding better value on the
net. |
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John Larkin
Guest
|
| Posted:
Mon Nov 28, 2005 5:35 pm Post subject:
Re: 240vac xformer and tube amp |
|
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On Mon, 28 Nov 2005 09:52:55 -0500, "Michael" <newszz10@yahoo.com>
wrote:
| Quote: | I've been in electronics a long time but it's been years since I've messed
with tube stuff but I thought I "may" build a small guitar (practice) amp.
First question is...
Has anyone explored the possibility of using a simple (and generally
inexpensive) 120 to 240vac step up transformer with a solid state bridge
rectifier to get high voltage for a tube?
|
If it's an autotransformer, and most are, it won't be isolated and
will be a shock hazard.
John
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Michael
Guest
|
| Posted:
Mon Nov 28, 2005 5:35 pm Post subject:
Re: 240vac xformer and tube amp |
|
|
I see where Hammond makes a few 230vct transformers, one that will supply
..35a for about 20 bucks....not an autotransformer.
Wonder if anyone has seen a design with these for a small practice amp with
just a few watts?
"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:h8bmo19pcsftem4m4qi347n5sut62ctj8i@4ax.com...
| Quote: | On Mon, 28 Nov 2005 09:52:55 -0500, "Michael" <newszz10@yahoo.com
wrote:
I've been in electronics a long time but it's been years since I've messed
with tube stuff but I thought I "may" build a small guitar (practice) amp.
First question is...
Has anyone explored the possibility of using a simple (and generally
inexpensive) 120 to 240vac step up transformer with a solid state bridge
rectifier to get high voltage for a tube?
If it's an autotransformer, and most are, it won't be isolated and
will be a shock hazard.
John
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John Popelish
Guest
|
| Posted:
Mon Nov 28, 2005 5:35 pm Post subject:
Re: 240vac xformer and tube amp |
|
|
Michael wrote:
| Quote: | I see where Hammond makes a few 230vct transformers, one that will supply
.35a for about 20 bucks....not an autotransformer.
Wonder if anyone has seen a design with these for a small practice amp with
just a few watts?
|
That's an 80 VA transformer. Use a bridge rectifier on it and get 325
VDC out. You could get more than a few watts out of that with a class
B output stage. Use the center tap as a 162 volt DC output for the
earlier stages. |
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|
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Bob
Guest
|
| Posted:
Tue Nov 29, 2005 7:45 am Post subject:
Re: 240vac xformer and tube amp |
|
|
On Mon, 28 Nov 2005 09:52:55 -0500, "Michael" <newszz10@yahoo.com> wrote:
| Quote: | I've been in electronics a long time but it's been years since I've messed
with tube stuff but I thought I "may" build a small guitar (practice) amp.
First question is...
Has anyone explored the possibility of using a simple (and generally
inexpensive) 120 to 240vac step up transformer with a solid state bridge
rectifier to get high voltage for a tube?
Is there a design/schematic someone can refer me to on a particular tube
that could operate on the voltage from this arrangement....I would imagine
you could get close to plus 280-290 volts or so under load?
|
That's almost all I use! (Sorry, my schemo is a proprietary device!)
The peak voltage will be around 330 but will drop under full load back down to
250 or so - perfect for a 6BQ5 power tube. If you run a class A SE amp the
voltage will be stable... don't go over 300...
Preamp tubes like the 12AX7A will run on anything over 150 volts with no
problem...
Don't forget you need a 6 volt filament supply at a few amps...
Oh, I hope you have experience with wiring a high Z high gain wide bandwidth
device - or it won't work... it'll either hum or oscillate or both, probably...
Then there's the matter of Tone...
Bob
Amp builder |
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Bob
Guest
|
| Posted:
Tue Nov 29, 2005 7:51 am Post subject:
Re: 240vac xformer and tube amp |
|
|
On Mon, 28 Nov 2005 11:57:22 -0500, John Popelish <jpopelish@rica.net> wrote:
| Quote: | Michael wrote:
I see where Hammond makes a few 230vct transformers, one that will supply
.35a for about 20 bucks....not an autotransformer.
Wonder if anyone has seen a design with these for a small practice amp with
just a few watts?
That's an 80 VA transformer. Use a bridge rectifier on it and get 325
VDC out.
|
Not at load... I get 275 volts after a 150 ohm filter... about 10 less than the
bridge output, for a SE EL84 5 watt amp. Higher loading would reduce it more...
| Quote: | You could get more than a few watts out of that with a class
B output stage. Use the center tap as a 162 volt DC output for the
earlier stages.
|
You can't use the center tap if you use the full secondary with a bridge...
Bob
Amp builder |
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|
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John Popelish
Guest
|
| Posted:
Tue Nov 29, 2005 8:00 am Post subject:
Re: 240vac xformer and tube amp |
|
|
Bob wrote:
| Quote: | On Mon, 28 Nov 2005 11:57:22 -0500, John Popelish <jpopelish@rica.net> wrote:
That's an 80 VA transformer. Use a bridge rectifier on it and get 325
VDC out.
Not at load... I get 275 volts after a 150 ohm filter... about 10 less than the
bridge output, for a SE EL84 5 watt amp. Higher loading would reduce it more...
You could get more than a few watts out of that with a class
B output stage. Use the center tap as a 162 volt DC output for the
earlier stages.
You can't use the center tap if you use the full secondary with a bridge...
|
Why not? |
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Doggone
Guest
|
| Posted:
Tue Nov 29, 2005 9:35 am Post subject:
Re: 240vac xformer and tube amp |
|
|
Bob <BobFlintsTone@spam.com> wrote in
news:cmcno1948bq2l2htsnuuufr2rlpfa58kb5@4ax.com:
| Quote: | On Mon, 28 Nov 2005 11:57:22 -0500, John Popelish <jpopelish@rica.net
wrote:
Michael wrote:
I see where Hammond makes a few 230vct transformers, one that will
supply .35a for about 20 bucks....not an autotransformer.
Wonder if anyone has seen a design with these for a small practice amp
with just a few watts?
That's an 80 VA transformer. Use a bridge rectifier on it and get 325
VDC out.
Not at load... I get 275 volts after a 150 ohm filter... about 10 less
than the bridge output, for a SE EL84 5 watt amp. Higher loading would
reduce it more...
You could get more than a few watts out of that with a class
B output stage. Use the center tap as a 162 volt DC output for the
earlier stages.
You can't use the center tap if you use the full secondary with a
bridge...
Bob
Amp builder
|
Hi Bob.
You can use the center tap. It will be at exactly 1/2 the B+. |
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|
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Bob
Guest
|
| Posted:
Wed Nov 30, 2005 7:59 am Post subject:
Re: 240vac xformer and tube amp |
|
|
On Mon, 28 Nov 2005 21:00:04 -0500, John Popelish <jpopelish@rica.net> wrote:
| Quote: | Bob wrote:
On Mon, 28 Nov 2005 11:57:22 -0500, John Popelish <jpopelish@rica.net> wrote:
That's an 80 VA transformer. Use a bridge rectifier on it and get 325
VDC out.
Not at load... I get 275 volts after a 150 ohm filter... about 10 less than the
bridge output, for a SE EL84 5 watt amp. Higher loading would reduce it more...
You could get more than a few watts out of that with a class
B output stage. Use the center tap as a 162 volt DC output for the
earlier stages.
You can't use the center tap if you use the full secondary with a bridge...
Why not?
|
Sorry - my bad - you can... I must have been pre-occupied! |
|
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|
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Bob
Guest
|
| Posted:
Wed Nov 30, 2005 8:01 am Post subject:
Re: 240vac xformer and tube amp |
|
|
On Tue, 29 Nov 2005 04:53:13 GMT, Doggone <running@parked.cars> wrote:
| Quote: | Bob <BobFlintsTone@spam.com> wrote in
news:cmcno1948bq2l2htsnuuufr2rlpfa58kb5@4ax.com:
On Mon, 28 Nov 2005 11:57:22 -0500, John Popelish <jpopelish@rica.net
wrote:
Michael wrote:
I see where Hammond makes a few 230vct transformers, one that will
supply .35a for about 20 bucks....not an autotransformer.
Wonder if anyone has seen a design with these for a small practice amp
with just a few watts?
That's an 80 VA transformer. Use a bridge rectifier on it and get 325
VDC out.
Not at load... I get 275 volts after a 150 ohm filter... about 10 less
than the bridge output, for a SE EL84 5 watt amp. Higher loading would
reduce it more...
You could get more than a few watts out of that with a class
B output stage. Use the center tap as a 162 volt DC output for the
earlier stages.
You can't use the center tap if you use the full secondary with a
bridge...
Bob
Amp builder
Hi Bob.
You can use the center tap. It will be at exactly 1/2 the B+.
|
You're right - I must have been thinking of getting the bias from there, which
is negative... |
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| Back to top |
|
|
Phil S
Guest
|
| Posted:
Wed Nov 30, 2005 8:20 am Post subject:
Re: 240vac xformer and tube amp |
|
|
"Bob" <BobFlintsTone@spam.com> wrote in message
news:01cno1dm4q8qk7tsuvv2nf54ehjm688dd8@4ax.com...
| Quote: | On Mon, 28 Nov 2005 09:52:55 -0500, "Michael" <newszz10@yahoo.com> wrote:
I've been in electronics a long time but it's been years since I've messed
with tube stuff but I thought I "may" build a small guitar (practice) amp.
First question is...
Has anyone explored the possibility of using a simple (and generally
inexpensive) 120 to 240vac step up transformer with a solid state bridge
rectifier to get high voltage for a tube?
Is there a design/schematic someone can refer me to on a particular tube
that could operate on the voltage from this arrangement....I would imagine
you could get close to plus 280-290 volts or so under load?
That's almost all I use! (Sorry, my schemo is a proprietary device!)
The peak voltage will be around 330 but will drop under full load back
down to
250 or so - perfect for a 6BQ5 power tube. If you run a class A SE amp the
voltage will be stable... don't go over 300...
Preamp tubes like the 12AX7A will run on anything over 150 volts with no
problem...
Don't forget you need a 6 volt filament supply at a few amps...
Oh, I hope you have experience with wiring a high Z high gain wide
bandwidth
device - or it won't work... it'll either hum or oscillate or both,
probably...
Then there's the matter of Tone...
Bob
Amp builder
|
Hey Bob!
You're the one who told me to tie two secondary (82v + 125v) windings of
that old Heathkit TV power tranny in series and it would give more than
enough B+ for a Champ like thing. I haven't seen you around in a while.
Thought I'd mention that it worked out just like you said it would. As I
recall, B+ was in the neigborhood of 250VDC. I built it with a diode
bridge, 12AT7, and 6AQ5. Works great! Amp building is addictive. I built
two more since then (5E3-almost, and JTM45).
Phil |
|
| Back to top |
|
|
Bob
Guest
|
| Posted:
Wed Nov 30, 2005 8:57 am Post subject:
Re: 240vac xformer and tube amp |
|
|
On Tue, 29 Nov 2005 21:20:19 -0500, "Phil S" <psymonds_no_spam@comcast.net>
wrote:
| Quote: |
"Bob" <BobFlintsTone@spam.com> wrote in message
news:01cno1dm4q8qk7tsuvv2nf54ehjm688dd8@4ax.com...
On Mon, 28 Nov 2005 09:52:55 -0500, "Michael" <newszz10@yahoo.com> wrote:
I've been in electronics a long time but it's been years since I've messed
with tube stuff but I thought I "may" build a small guitar (practice) amp.
First question is...
Has anyone explored the possibility of using a simple (and generally
inexpensive) 120 to 240vac step up transformer with a solid state bridge
rectifier to get high voltage for a tube?
Is there a design/schematic someone can refer me to on a particular tube
that could operate on the voltage from this arrangement....I would imagine
you could get close to plus 280-290 volts or so under load?
That's almost all I use! (Sorry, my schemo is a proprietary device!)
The peak voltage will be around 330 but will drop under full load back
down to
250 or so - perfect for a 6BQ5 power tube. If you run a class A SE amp the
voltage will be stable... don't go over 300...
Preamp tubes like the 12AX7A will run on anything over 150 volts with no
problem...
Don't forget you need a 6 volt filament supply at a few amps...
Oh, I hope you have experience with wiring a high Z high gain wide
bandwidth
device - or it won't work... it'll either hum or oscillate or both,
probably...
Then there's the matter of Tone...
Bob
Amp builder
Hey Bob!
You're the one who told me to tie two secondary (82v + 125v) windings of
that old Heathkit TV power tranny in series and it would give more than
enough B+ for a Champ like thing. I haven't seen you around in a while.
Thought I'd mention that it worked out just like you said it would. As I
recall, B+ was in the neigborhood of 250VDC. I built it with a diode
bridge, 12AT7, and 6AQ5. Works great! Amp building is addictive. I built
two more since then (5E3-almost, and JTM45).
Phil
|
Hi Phil - I remember you!
I don't come here too much because of the off topic political bullshit - some
people can't understand this is a guitar amp group...
As for addictive amp building - I'm now working on number twenty something...
I'm trying toroids this time! |
|
| Back to top |
|
|
Phil S
Guest
|
| Posted:
Wed Nov 30, 2005 9:12 am Post subject:
Re: 240vac xformer and tube amp |
|
|
"Bob" <BobFlintsTone@spam.com> wrote in message
news:a35qo194jmiv8f7ib7p4bl3d86cjoqpr9b@4ax.com...
| Quote: | On Tue, 29 Nov 2005 21:20:19 -0500, "Phil S"
psymonds_no_spam@comcast.net
wrote:
"Bob" <BobFlintsTone@spam.com> wrote in message
news:01cno1dm4q8qk7tsuvv2nf54ehjm688dd8@4ax.com...
On Mon, 28 Nov 2005 09:52:55 -0500, "Michael" <newszz10@yahoo.com
wrote:
I've been in electronics a long time but it's been years since I've
messed
with tube stuff but I thought I "may" build a small guitar (practice)
amp.
First question is...
Has anyone explored the possibility of using a simple (and generally
inexpensive) 120 to 240vac step up transformer with a solid state bridge
rectifier to get high voltage for a tube?
Is there a design/schematic someone can refer me to on a particular tube
that could operate on the voltage from this arrangement....I would
imagine
you could get close to plus 280-290 volts or so under load?
That's almost all I use! (Sorry, my schemo is a proprietary device!)
The peak voltage will be around 330 but will drop under full load back
down to
250 or so - perfect for a 6BQ5 power tube. If you run a class A SE amp
the
voltage will be stable... don't go over 300...
Preamp tubes like the 12AX7A will run on anything over 150 volts with no
problem...
Don't forget you need a 6 volt filament supply at a few amps...
Oh, I hope you have experience with wiring a high Z high gain wide
bandwidth
device - or it won't work... it'll either hum or oscillate or both,
probably...
Then there's the matter of Tone...
Bob
Amp builder
Hey Bob!
You're the one who told me to tie two secondary (82v + 125v) windings of
that old Heathkit TV power tranny in series and it would give more than
enough B+ for a Champ like thing. I haven't seen you around in a while.
Thought I'd mention that it worked out just like you said it would. As I
recall, B+ was in the neigborhood of 250VDC. I built it with a diode
bridge, 12AT7, and 6AQ5. Works great! Amp building is addictive. I
built
two more since then (5E3-almost, and JTM45).
Phil
Hi Phil - I remember you!
I don't come here too much because of the off topic political bullshit -
some
people can't understand this is a guitar amp group...
As for addictive amp building - I'm now working on number twenty
something...
I'm trying toroids this time!
|
Well you dropped in at a decent time. Between the filters and whatnot,
things are down below a dull roar at the moment. I don't think it will stay
that way. Anyhow, it was nice to see you drop by. Toroids, huh? What's
the deal with them?
Phil |
|
| Back to top |
|
|
Doggone
Guest
|
| Posted:
Wed Nov 30, 2005 9:31 am Post subject:
Re: 240vac xformer and tube amp |
|
|
Bob <BobFlintsTone@spam.com> wrote in
news:a35qo194jmiv8f7ib7p4bl3d86cjoqpr9b@4ax.com:
| Quote: | On Tue, 29 Nov 2005 21:20:19 -0500, "Phil S"
psymonds_no_spam@comcast.net> wrote:
"Bob" <BobFlintsTone@spam.com> wrote in message
news:01cno1dm4q8qk7tsuvv2nf54ehjm688dd8@4ax.com...
On Mon, 28 Nov 2005 09:52:55 -0500, "Michael" <newszz10@yahoo.com
wrote:
I've been in electronics a long time but it's been years since I've
messed with tube stuff but I thought I "may" build a small guitar
(practice) amp.
First question is...
Has anyone explored the possibility of using a simple (and generally
inexpensive) 120 to 240vac step up transformer with a solid state
bridge rectifier to get high voltage for a tube?
Is there a design/schematic someone can refer me to on a particular
tube that could operate on the voltage from this arrangement....I
would imagine you could get close to plus 280-290 volts or so under
load?
That's almost all I use! (Sorry, my schemo is a proprietary device!)
The peak voltage will be around 330 but will drop under full load back
down to
250 or so - perfect for a 6BQ5 power tube. If you run a class A SE amp
the voltage will be stable... don't go over 300...
Preamp tubes like the 12AX7A will run on anything over 150 volts with
no problem...
Don't forget you need a 6 volt filament supply at a few amps...
Oh, I hope you have experience with wiring a high Z high gain wide
bandwidth
device - or it won't work... it'll either hum or oscillate or both,
probably...
Then there's the matter of Tone...
Bob
Amp builder
Hey Bob!
You're the one who told me to tie two secondary (82v + 125v) windings of
that old Heathkit TV power tranny in series and it would give more than
enough B+ for a Champ like thing. I haven't seen you around in a while.
Thought I'd mention that it worked out just like you said it would. As
I recall, B+ was in the neigborhood of 250VDC. I built it with a diode
bridge, 12AT7, and 6AQ5. Works great! Amp building is addictive. I
built two more since then (5E3-almost, and JTM45).
Phil
Hi Phil - I remember you!
I don't come here too much because of the off topic political bullshit -
some people can't understand this is a guitar amp group...
As for addictive amp building - I'm now working on number twenty
something... I'm trying toroids this time!
|
Amp junkies can be itentified by the solder burns on their hands.
Do you know of a source for toroidal transformers with both a high voltage
and filament windings or do you wind your own? I found Hammond have decent
toroidals but don't have mixed windings. They also tend to be quite pricey. I
find it had to justify the extra cost when recycled iron can be had so cheap.
Is there such a thing as a toroidal output transformer?
<thinking>......... R.K. style......................................
Would the core end up being unrealistically large? What do you think? |
|
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