| Author |
Message |
Iain M Churches
Guest
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 Posted:
Wed Sep 28, 2005 11:04 am Post subject:
Warm start options |
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Modern valve/tube amps seem to use a delay start
for their HT.
In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
At the moment, the only negative aspect I can see about
this arrangement is that the psu caps will be allowed to
charge to peak voltage as the output valves are drawing
no current. But, providing one makes allowances for this
it should not be a problem.
Does this seem like a good idea?
Any other suggestions?
Iain
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Mike Gilmour
Guest
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| Posted:
Wed Sep 28, 2005 4:00 pm Post subject:
Re: Warm start options |
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"Iain M Churches" <tael@kolumbus.fi> wrote in message
news:dhdbq3$fol$1@phys-news1.kolumbus.fi...
| Quote: | Modern valve/tube amps seem to use a delay start
for their HT.
In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
At the moment, the only negative aspect I can see about
this arrangement is that the psu caps will be allowed to
charge to peak voltage as the output valves are drawing
no current. But, providing one makes allowances for this
it should not be a problem.
Does this seem like a good idea?
Any other suggestions?
Iain
|
Hi Iain,
I actually prefer no delay relay at all, just with separate power and HT
switches. Mind you I was brought up on valve based comms equipment so its
second nature to give time for the valves to warm.....and you're less likely
to be caught out during servicing ;-)
Mike
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Iain M Churches
Guest
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| Posted:
Wed Sep 28, 2005 4:10 pm Post subject:
Re: Warm start options |
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"Mike Gilmour" <mike@tfjazz.freeserve.co.uk> wrote in message
news:sKmdnYetG_hM6qfeRVnytA@pipex.net...
| Quote: |
"Iain M Churches" <tael@kolumbus.fi> wrote in message
news:dhdbq3$fol$1@phys-news1.kolumbus.fi...
Modern valve/tube amps seem to use a delay start
for their HT.
In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
At the moment, the only negative aspect I can see about
this arrangement is that the psu caps will be allowed to
charge to peak voltage as the output valves are drawing
no current. But, providing one makes allowances for this
it should not be a problem.
Does this seem like a good idea?
Any other suggestions?
Iain
Hi Iain,
I actually prefer no delay relay at all, just with separate power and HT
switches. Mind you I was brought up on valve based comms equipment so its
second nature to give time for the valves to warm.....and you're less
likely to be caught out during servicing ;-)
Mike
|
Hi Mike,
Yes, that's how all studio amps and consoles used to do it.
Old studio joke when interviewing trainees:
"Can you count to 45?"
But I wonder if that solution might be too "agricultural" in this
age of infra red remotes and motorised gain controls?
Iain |
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Patrick Turner
Guest
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| Posted:
Wed Sep 28, 2005 7:51 pm Post subject:
Re: Warm start options |
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Iain M Churches wrote:
| Quote: | Modern valve/tube amps seem to use a delay start
for their HT.
In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
At the moment, the only negative aspect I can see about
this arrangement is that the psu caps will be allowed to
charge to peak voltage as the output valves are drawing
no current. But, providing one makes allowances for this
it should not be a problem.
Does this seem like a good idea?
Any other suggestions?
|
There is no reason to delay the B+ in a fixed bias amp.
The fixed bias using Si rectifiers will establish itself
way before the output tubes turn on so no need for a B+
delay because you cannot get a situtation where the
B+ will be established with hot cathodes, and with no bias.
I have seen countless amps with no delay other than a 4 second one to
limit inrush current, and they work fine.
Patrick Turner.
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獅子口
Guest
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| Posted:
Wed Sep 28, 2005 9:06 pm Post subject:
Re: Warm start options |
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In my 211 amp the B+ is supplied by full wave connected diodes.
I place a 20W 10K ohm resistor from the CT of the HT transformer to the
ground.
The resistor is shorted circuit by an octal timer (under USD 10) programable
from 0 to 60 seconds,
so the cap is about charged half to its DC voltage rating when the 211
tubes are warming up.
"Iain M Churches" <tael@kolumbus.fi> 撰寫於郵件新聞:dhdbq3$fol$1@phys-news1.kolumbus.fi...
| Quote: | Modern valve/tube amps seem to use a delay start
for their HT.
In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
At the moment, the only negative aspect I can see about
this arrangement is that the psu caps will be allowed to
charge to peak voltage as the output valves are drawing
no current. But, providing one makes allowances for this
it should not be a problem.
Does this seem like a good idea?
Any other suggestions?
Iain
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Bret Ludwig
Guest
|
| Posted:
Wed Sep 28, 2005 9:54 pm Post subject:
Re: Warm start options |
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| Quote: | In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
|
I like to have separate heater and B+ supplies on their own switch,
but wired so that you cannot have B+ without heater first. Derive the
bias from the heater supply so as long as you have heater voltage you
have bias.
If you want to get fancy you can use a rotary switch. I saw one setup
that used a four way switch for a coin-op clothesdryer, available for a
few dollars from any appliance store. I think it might have been in the
old "Sound Practices" or "Glass Audio". I just use two toggle switches
myself. The split rocker used for parking and head lights in GM cars,
or the BAT and ALT master switch in Cessna aircraft, would work ok too.
They are DC rated but will actually work fine on 115 VAC at these
currents. |
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Iain M Churches
Guest
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| Posted:
Wed Sep 28, 2005 10:58 pm Post subject:
Re: Warm start options |
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"Patrick Turner" <info@turneraudio.com.au> wrote in message
news:433AACF8.4530F9E4@turneraudio.com.au...
| Quote: |
Iain M Churches wrote:
Modern valve/tube amps seem to use a delay start
for their HT.
In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
At the moment, the only negative aspect I can see about
this arrangement is that the psu caps will be allowed to
charge to peak voltage as the output valves are drawing
no current. But, providing one makes allowances for this
it should not be a problem.
Does this seem like a good idea?
Any other suggestions?
There is no reason to delay the B+ in a fixed bias amp.
The fixed bias using Si rectifiers will establish itself
way before the output tubes turn on so no need for a B+
delay because you cannot get a situtation where the
B+ will be established with hot cathodes, and with no bias.
I have seen countless amps with no delay other than a 4 second one to
limit inrush current, and they work fine.
Patrick Turner.
Hi Patrick, |
My idea was to give the cathodes time to heat before allowing the OP
tubes to pass any current, and having a very negative voltage at the
grids would achieve this. But is this a good idea?
iain |
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west
Guest
|
| Posted:
Thu Sep 29, 2005 4:43 am Post subject:
Re: Warm start options |
|
|
"Iain M Churches" <tael@kolumbus.fi> wrote in message
news:dhdbq3$fol$1@phys-news1.kolumbus.fi...
| Quote: | Modern valve/tube amps seem to use a delay start
for their HT.
In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
At the moment, the only negative aspect I can see about
this arrangement is that the psu caps will be allowed to
charge to peak voltage as the output valves are drawing
no current. But, providing one makes allowances for this
it should not be a problem.
Does this seem like a good idea?
Any other suggestions?
Iain
|
There's a plethora of approaches you can take, Iain. Which is the best? The
answer, I believe, can break the record for the longest thread ever on RAT.
One of the basic tenets in electronic design is to be parsimonious with
parts. Wouldn't a temporary -80v bias require an additional circuit?
Cordially,
west
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Adam Stouffer
Guest
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| Posted:
Thu Sep 29, 2005 4:43 am Post subject:
Re: Warm start options |
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Iain M Churches wrote:
| Quote: |
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
|
Sounds like a good job for a PIC chip. Now if I only knew how to program
them :) Those things are damn handy.
Adam |
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Chris Hornbeck
Guest
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| Posted:
Thu Sep 29, 2005 4:43 am Post subject:
Re: Warm start options |
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|
On Wed, 28 Sep 2005 09:04:37 +0300, "Iain M Churches"
<tael@kolumbus.fi> wrote:
| Quote: | In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
|
Lots of good stuff already, but let me just add that
the thermal delays will suffer from arcing at the
end of their cycle, so must often be used to operate
a relay.
Also, a two pole relay allows you to force a
restart "from cold", by turning off the delay relay's
heater, which matters if voltage soaring or similar is
an issue.
Good fortune,
Chris Hornbeck
"I had a perspective on the booing, too. You
can kill somebody with kindness." -Bob Dylan |
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Iain M Churches
Guest
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| Posted:
Thu Sep 29, 2005 12:44 pm Post subject:
Re: Warm start options |
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|
"獅子口" <lionmouth@scientist.com> wrote in message
news:433abf52$1_3@rain.i-cable.com...
| Quote: | In my 211 amp the B+ is supplied by full wave connected diodes.
I place a 20W 10K ohm resistor from the CT of the HT transformer to the
ground.
The resistor is shorted circuit by an octal timer (under USD 10)
programable from 0 to 60 seconds,
so the cap is about charged half to its DC voltage rating when the 211
tubes are warming up.
That sounds like a good scheme, although I have been warned about |
switching high DC voltages with relays. But by "shorted" you probably
mean "connected" ?
Another idea might be to use a bleeder resistor across the N/O
contacts of a relay to allow the cap chain to charge slowly to say
half the working voltage, (not enough to allow the OP valves to
draw current) and so reduce the inrush current when the
relay switches.
Waddayathink?
Iain |
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Iain M Churches
Guest
|
| Posted:
Thu Sep 29, 2005 12:45 pm Post subject:
Re: Warm start options |
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"west" <westley@Tampabay.rr.com> wrote in message
news:uUI_e.113614$xl6.108888@tornado.tampabay.rr.com...
| Quote: | "Iain M Churches" <tael@kolumbus.fi> wrote in message
news:dhdbq3$fol$1@phys-news1.kolumbus.fi...
Modern valve/tube amps seem to use a delay start
for their HT.
In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
At the moment, the only negative aspect I can see about
this arrangement is that the psu caps will be allowed to
charge to peak voltage as the output valves are drawing
no current. But, providing one makes allowances for this
it should not be a problem.
Does this seem like a good idea?
Any other suggestions?
There's a plethora of approaches you can take, Iain. Which is the best?
The
answer, I believe, can break the record for the longest thread ever on
RAT.
One of the basic tenets in electronic design is to be parsimonious with
parts.
|
Hi West
Yes. I am looking for what that great audiophile Tina Turner calls
"Simply the Best":-)
| Quote: | Wouldn't a temporary -80v bias require an additional circuit?
|
The bias supply is -80VDC with a 25k/2W pot across it, with bias
fed from the wiper. My idea was to have a timer relay which would
be connected to the top of the pot (-80VDC) while the timer was
running, and then switch to the wiper after 45s to set the bias at the
normal level and let the valves draw current.
Does that make sense?
Would it be better than switching the HT?
Cheers
Iain |
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Iain M Churches
Guest
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| Posted:
Thu Sep 29, 2005 12:46 pm Post subject:
Re: Warm start options |
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|
"Chris Hornbeck" <chrishornbeckremovethis@att.net> wrote in message
news:v1bmj1d31nbefa3iaqvcfcjpj69v7sc6uu@4ax.com...
| Quote: | On Wed, 28 Sep 2005 09:04:37 +0300, "Iain M Churches"
tael@kolumbus.fi> wrote:
In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
Lots of good stuff already,
|
Yes. RAT is a great group.
| Quote: | but let me just add that
the thermal delays will suffer from arcing at the
end of their cycle, so must often be used to operate
a relay.
|
I did not go into detail, but it is wired just as you describe,
and operates a power relay. The thermal relay switches off
after the delay time has been reached. That should ensure
that it lasts for many years. I did find though in the case of the
DLS 16 that they vary enormously. So I had to pick and match
and vary the voltage across the heater to get a pair (one each
channel psu) that would switch at almost the same time.
| Quote: |
Also, a two pole relay allows you to force a
restart "from cold", by turning off the delay relay's
heater, which matters if voltage soaring or similar is
an issue.
|
That is one reason why I liked the idea of switching the
bias, as it is low voltage with minimal current.
Iain |
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Sander deWaal
Guest
|
| Posted:
Thu Sep 29, 2005 9:30 pm Post subject:
Re: Warm start options |
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|
Adam Stouffer <adam_stouffer@hotmail.com> said:
| Quote: | I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
|
| Quote: | Sounds like a good job for a PIC chip. Now if I only knew how to program
them :) Those things are damn handy.
|
Nothing that a simple NE555 can't do.
--
"Audio as a serious hobby is going down the tubes."
- Howard Ferstler, 25/4/2005 |
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Chris Hornbeck
Guest
|
| Posted:
Fri Sep 30, 2005 4:24 am Post subject:
Re: Warm start options |
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|
On Thu, 29 Sep 2005 10:46:46 +0300, "Iain M Churches"
<tael@kolumbus.fi> wrote:
| Quote: | I did not go into detail, but it is wired just as you describe,
and operates a power relay. The thermal relay switches off
after the delay time has been reached. That should ensure
that it lasts for many years. I did find though in the case of the
DLS 16 that they vary enormously. So I had to pick and match
and vary the voltage across the heater to get a pair (one each
channel psu) that would switch at almost the same time.
|
If I'm following you correctly, you're operating *after*
the power transformer's secondary. You might really
enjoy the freedom of design you'd get from separate
filament and HV power transformers.
I know; I know; "I'm not worthy" you say. BZZZT.
Yes you are. Live now. Life's short.
| Quote: | Also, a two pole relay allows you to force a
restart "from cold", by turning off the delay relay's
heater, which matters if voltage soaring or similar is
an issue.
That is one reason why I liked the idea of switching the
bias, as it is low voltage with minimal current.
|
I'm just not convinced that this *does anything*
useful or important. And has the serious disadvantage
of lacking a silent startup that comes free by *not*
doing it.
But that's just me. Good fortune, and Big Fun,
Chris Hornbeck
"I did it because he lied, 'cause he took you for a ride,
because time was on his side, and because...
I want you" -Dylan |
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