[Wessel Dirksen]

Hi RAT's,

I don't know if some of you recall me from about a year ago when I was
tuning in here regularly but I was asking some newbie questions back
then and got great friendly advice. I actually regularly refer to saved
threads from here. I got away from the tubes for awhile because my
first project is working just fine without my messing with it and
because I have been pleasantly distracted by a great gal in my life.
Nice to be back.

My question then: How important is it to raise the top tube's heater
potential in a SRPP? I've read it's supposed to be a noise issue with
the neighboring cathode but I've not had any real noise problems with
this so far. It sounds great. The potential difference doesn't burn
anything up does it?

Wessel

[Tom Bavis]

On 21 Dec 2006 13:21:52 -0800, "Wessel Dirksen"
wrote:

Hi RAT's,

I don't know if some of you recall me from about a year ago when I was
tuning in here regularly but I was asking some newbie questions back
then and got great friendly advice. I actually regularly refer to saved
threads from here. I got away from the tubes for awhile because my
first project is working just fine without my messing with it and
because I have been pleasantly distracted by a great gal in my life.
Nice to be back.

My question then: How important is it to raise the top tube's heater
potential in a SRPP? I've read it's supposed to be a noise issue with
the neighboring cathode but I've not had any real noise problems with
this so far. It sounds great. The potential difference doesn't burn
anything up does it?

Wessel

It might... is the heater-to-cathode voltage greater than 100V? Most
tubes are rated for 100V maximum. You might be able to bias the
heater winding to a positive voltage to reducethe differential
(byspass it with a capacitor with a low impedance at 60 Hz),

[Andre Jute]

Wessel Dirksen wrote:
Hi RAT's,

I don't know if some of you recall me from about a year ago when I was
tuning in here regularly but I was asking some newbie questions back
then and got great friendly advice. I actually regularly refer to saved
threads from here. I got away from the tubes for awhile because my
first project is working just fine without my messing with it and
because I have been pleasantly distracted by a great gal in my life.
Nice to be back.

Glad your electronic display attracted a mate.

My question then: How important is it to raise the top tube's heater
potential in a SRPP? I've read it's supposed to be a noise issue with
the neighboring cathode but I've not had any real noise problems with
this so far. It sounds great.

Who says it is a noise issue? I don't quite see it, and I've never
heard it.

The potential difference doesn't burn
anything up does it?

Yes it does. The damage is called cathode stripping. It ruins the tube.
Never seen this one either. There are several ways of solving the
problem.

You can restore normative conditions with DC voltage from a voltage
divider at the end of the B+; this is a very common way of doing it;
see my T44 300B design at
http://members.lycos.co.uk/fiultra/T44bis-'Populaire'-crct.jpg -- the
filament float is the part of the circuit on the blue panel.

You can use a floating (i.e. ungrounded) regulated filament supply; be
careful to note that not all stages of your amp will be the same
voltage above ground or have the same permitted differential; in an amp
with a split 300V plus/minus B supply to drive electrostatic headphones
I recently designed I used a regulated filament supply for each of the
four tubes (used as longtail pairs) because that was simpler than
working out how much above or below ground each tube was and how far it
was from any of the others... (The official story is I was adding value
to a commercial design -- hey-ho!)

Finally, you can do nothing, which is in fact what I normally do with
SRPP; depends how valuable your tubes are, I suppose.

Wessel

Nice to see you back, Wessel.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

[Iain Churches]

"Wessel Dirksen" wrote in message
ups.com...
Hi RAT's,

I don't know if some of you recall me from about a year ago when I was
tuning in here regularly but I was asking some newbie questions back
then and got great friendly advice. I actually regularly refer to saved
threads from here. I got away from the tubes for awhile because my
first project is working just fine without my messing with it and
because I have been pleasantly distracted by a great gal in my life.
Nice to be back.

My question then: How important is it to raise the top tube's heater
potential in a SRPP? I've read it's supposed to be a noise issue with
the neighboring cathode but I've not had any real noise problems with
this so far. It sounds great. The potential difference doesn't burn
anything up does it?

Wessel


Hi Wessel. Nice to see you posting here again:-)

Many books stress the importance of not exceeding the maximum
permitted cathode to heater potential, especially in SRPP, cathode
follower, mu- follower etc etc.

It can be done simply by making a potential divider of two resistors
adding up to say 1M across the B+ Set the value of the lower
resistor to give you the voltage required (I often use 90V) Remember
that the heater supply must be floating. Decouple the lower resistor
with 0.1µF to ground. Take the lead from this divider to a pair of
100 Ohms resistors, and from these to either side of the heater
supply electrolytic.


I have done this on several projects with great success.

Regards to all
Iain

[robert casey]

My question then: How important is it to raise the top tube's heater
potential in a SRPP? I've read it's supposed to be a noise issue with
the neighboring cathode but I've not had any real noise problems with
this so far. It sounds great. The potential difference doesn't burn
anything up does it?


Most tubes are rated to only take about a hundred volts DC between the
heater and the cathode. If you have a separate heater secondary from
the power transformer, you could bias that to a voltage slightly higher
than the voltage the top tube's cathode will usually reside at. The
bottom tube cathode's heater would normally be fed by a grounded heater
secondary. This would mean that you have to divvy up the segments of
the twin triodes between the left and right channels such that one tube
does the bottoms of the left and the right channel, and the other tube
does the tops of the left and the right channels.

[Wessel Dirksen]

On 22 dec 2006, 12:30, "Iain Churches" wrote:
"Wessel Dirksen" wrote in oglegroups.com...





Hi RAT's,

I don't know if some of you recall me from about a year ago when I was
tuning in here regularly but I was asking some newbie questions back
then and got great friendly advice. I actually regularly refer to saved
threads from here. I got away from the tubes for awhile because my
first project is working just fine without my messing with it and
because I have been pleasantly distracted by a great gal in my life.
Nice to be back.

My question then: How important is it to raise the top tube's heater
potential in a SRPP? I've read it's supposed to be a noise issue with
the neighboring cathode but I've not had any real noise problems with
this so far. It sounds great. The potential difference doesn't burn
anything up does it?

WesselHi Wessel. Nice to see you posting here again:-)

Many books stress the importance of not exceeding the maximum
permitted cathode to heater potential, especially in SRPP, cathode
follower, mu- follower etc etc.

It can be done simply by making a potential divider of two resistors
adding up to say 1M across the B+ Set the value of the lower
resistor to give you the voltage required (I often use 90V) Remember
that the heater supply must be floating. Decouple the lower resistor
with 0.1µF to ground. Take the lead from this divider to a pair of
100 Ohms resistors, and from these to either side of the heater
supply electrolytic.

Ian,
It appears that by saying "either" side, you mean 100 ohm to both sides
of the heater voltage. Is this so?
Elegant.

Took awhile to back to this. Thanks everyone.

I have done this on several projects with great success.

Regards to all
Iain- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -

[Patrick Turner]

Wessel Dirksen wrote:

On 22 dec 2006, 12:30, "Iain Churches" wrote:
"Wessel Dirksen" wrote in oglegroups.com...





Hi RAT's,

I don't know if some of you recall me from about a year ago when I was
tuning in here regularly but I was asking some newbie questions back
then and got great friendly advice. I actually regularly refer to saved
threads from here. I got away from the tubes for awhile because my
first project is working just fine without my messing with it and
because I have been pleasantly distracted by a great gal in my life.
Nice to be back.

My question then: How important is it to raise the top tube's heater
potential in a SRPP? I've read it's supposed to be a noise issue with
the neighboring cathode but I've not had any real noise problems with
this so far. It sounds great. The potential difference doesn't burn
anything up does it?

WesselHi Wessel. Nice to see you posting here again:-)

Many books stress the importance of not exceeding the maximum
permitted cathode to heater potential, especially in SRPP, cathode
follower, mu- follower etc etc.

It can be done simply by making a potential divider of two resistors
adding up to say 1M across the B+ Set the value of the lower
resistor to give you the voltage required (I often use 90V) Remember
that the heater supply must be floating. Decouple the lower resistor
with 0.1µF to ground. Take the lead from this divider to a pair of
100 Ohms resistors, and from these to either side of the heater
supply electrolytic.

Ian,
It appears that by saying "either" side, you mean 100 ohm to both sides
of the heater voltage. Is this so?
Elegant.

Took awhile to back to this. Thanks everyone.


Where you have one heater supply for SRPP tubes with low rated
heater-cathode voltages of typically 90V, then the heater supply
can be set up as follows :-

Use 100 ohms from each of the heater winding to a connection point that
is
then also connected to a dc voltage divider so that you have a bias
voltage at about +75V
This means the cathode of the bottom tube is about 75V below the bias
voltage,
and if the top tube cathode is at +150V, then its cathode is 75V above
the bias voltage.
The bias voltage divider should be done with
say 220k and 47k or whatever R values that give the wanted bias voltage
which is half way between top and bottom cathode dc voltages.

The bias point of say +75V should be bypassed to 0V with a
100V rated 100uF.

There is still a possibility that power supply noise will still enter
the
tubes via the stray C between cathode and proximity of ac heater
voltages to the
tube grid connections.

To avoid this, rectify the heater ac to make a well filtered ( CRC ) dc
heater
supply which is then all ungrounded but biased up at +75V or wherever
you want it.

For more info on how to combine SRPP or µ-follower stages and heater
supplies, try reading
http://www.turneraudio.com.au/preamp...hono-2005.html
http://www.turneraudio.com.au/preamp...+psu-2005.html

The power supply for the tubed phono and line stages is at the lower
section
of the second of the above pages.

Happy Listening,

Patrick Turner.



I have done this on several projects with great success.

Regards to all
Iain- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -

[Wessel Dirksen]

On 25 jan, 14:12, Patrick Turner wrote:
Wessel Dirksen wrote:

On 22 dec 2006, 12:30, "Iain Churches" wrote:
"Wessel Dirksen" wrote in ooglegroups.com...

Hi RAT's,

I don't know if some of you recall me from about a year ago when I was
tuning in here regularly but I was asking some newbie questions back
then and got great friendly advice. I actually regularly refer to saved
threads from here. I got away from the tubes for awhile because my
first project is working just fine without my messing with it and
because I have been pleasantly distracted by a great gal in my life.
Nice to be back.

My question then: How important is it to raise the top tube's heater
potential in a SRPP? I've read it's supposed to be a noise issue with
the neighboring cathode but I've not had any real noise problems with
this so far. It sounds great. The potential difference doesn't burn
anything up does it?

WesselHi Wessel. Nice to see you posting here again:-)

Many books stress the importance of not exceeding the maximum
permitted cathode to heater potential, especially in SRPP, cathode
follower, mu- follower etc etc.

It can be done simply by making a potential divider of two resistors
adding up to say 1M across the B+ Set the value of the lower
resistor to give you the voltage required (I often use 90V) Remember
that the heater supply must be floating. Decouple the lower resistor
with 0.1µF to ground. Take the lead from this divider to a pair of
100 Ohms resistors, and from these to either side of the heater
supply electrolytic.

Ian,
It appears that by saying "either" side, you mean 100 ohm to both sides
of the heater voltage. Is this so?
Elegant.

Took awhile to back to this. Thanks everyone.Where you have one heater supply for SRPP tubes with low rated
heater-cathode voltages of typically 90V, then the heater supply
can be set up as follows :-

Use 100 ohms from each of the heater winding to a connection point that
is
then also connected to a dc voltage divider so that you have a bias
voltage at about +75V
This means the cathode of the bottom tube is about 75V below the bias
voltage,
and if the top tube cathode is at +150V, then its cathode is 75V above
the bias voltage.
The bias voltage divider should be done with
say 220k and 47k or whatever R values that give the wanted bias voltage
which is half way between top and bottom cathode dc voltages.

The bias point of say +75V should be bypassed to 0V with a
100V rated 100uF.

There is still a possibility that power supply noise will still enter
the
tubes via the stray C between cathode and proximity of ac heater
voltages to the
tube grid connections.

To avoid this, rectify the heater ac to make a well filtered ( CRC ) dc
heater
supply which is then all ungrounded but biased up at +75V or wherever
you want it.

For more info on how to combine SRPP or µ-follower stages and heater
supplies, try readinghttp://www.turneraudio.com.au/preamp-rocket-phono-2005.htmlhttp://www.turneraudio.com.au/preamp-nemo-line+psu-2005.html

The power supply for the tubed phono and line stages is at the lower
section
of the second of the above pages.

Happy Listening,

Patrick Turner.

Thanks for that Patrick. Now this circuit is clear to me.

Anyone know what the heater/cathode potential limit is for the Sovtec
6H30? 100V same as the rest?




I have done this on several projects with great success.

Regards to all
Iain- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -

[Patrick Turner]

Wessel Dirksen wrote:

On 25 jan, 14:12, Patrick Turner wrote:
Wessel Dirksen wrote:

On 22 dec 2006, 12:30, "Iain Churches" wrote:
"Wessel Dirksen" wrote in oglegroups.com...

Hi RAT's,

I don't know if some of you recall me from about a year ago when I was
tuning in here regularly but I was asking some newbie questions back
then and got great friendly advice. I actually regularly refer to saved
threads from here. I got away from the tubes for awhile because my
first project is working just fine without my messing with it and
because I have been pleasantly distracted by a great gal in my life.
Nice to be back.

My question then: How important is it to raise the top tube's heater
potential in a SRPP? I've read it's supposed to be a noise issue with
the neighboring cathode but I've not had any real noise problems with
this so far. It sounds great. The potential difference doesn't burn
anything up does it?

WesselHi Wessel. Nice to see you posting here again:-)

Many books stress the importance of not exceeding the maximum
permitted cathode to heater potential, especially in SRPP, cathode
follower, mu- follower etc etc.

It can be done simply by making a potential divider of two resistors
adding up to say 1M across the B+ Set the value of the lower
resistor to give you the voltage required (I often use 90V) Remember
that the heater supply must be floating. Decouple the lower resistor
with 0.1µF to ground. Take the lead from this divider to a pair of
100 Ohms resistors, and from these to either side of the heater
supply electrolytic.

Ian,
It appears that by saying "either" side, you mean 100 ohm to both sides
of the heater voltage. Is this so?
Elegant.

Took awhile to back to this. Thanks everyone.Where you have one heater supply for SRPP tubes with low rated
heater-cathode voltages of typically 90V, then the heater supply
can be set up as follows :-

Use 100 ohms from each of the heater winding to a connection point that
is
then also connected to a dc voltage divider so that you have a bias
voltage at about +75V
This means the cathode of the bottom tube is about 75V below the bias
voltage,
and if the top tube cathode is at +150V, then its cathode is 75V above
the bias voltage.
The bias voltage divider should be done with
say 220k and 47k or whatever R values that give the wanted bias voltage
which is half way between top and bottom cathode dc voltages.

The bias point of say +75V should be bypassed to 0V with a
100V rated 100uF.

There is still a possibility that power supply noise will still enter
the
tubes via the stray C between cathode and proximity of ac heater
voltages to the
tube grid connections.

To avoid this, rectify the heater ac to make a well filtered ( CRC ) dc
heater
supply which is then all ungrounded but biased up at +75V or wherever
you want it.

For more info on how to combine SRPP or µ-follower stages and heater
supplies, try readinghttp://www.turneraudio.com.au/preamp-rocket-phono-2005.htmlhttp://www.turneraudio.com.au/preamp-nemo-line+psu-2005.html

The power supply for the tubed phono and line stages is at the lower
section
of the second of the above pages.

Happy Listening,

Patrick Turner.

Thanks for that Patrick. Now this circuit is clear to me.

Anyone know what the heater/cathode potential limit is for the Sovtec
6H30? 100V same as the rest?

No, I don't exactly know what the heater-cathode voltage is, but
100V is a safe bet, even when official ratings are higher.


Patrick Turner.




I have done this on several projects with great success.

Regards to all
Iain- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -

[Wessel Dirksen]

Last question on this topic.

Maybe I'm missing something here, but why is a floating heater supply
in itself not a solution to the problem? "Floating" would seem to
indicate that there is no potential relative to the rest of the
elements in the tube. As such would it not just be a hot piece of
metal in the neighborhood with no (little) thermionic attraction to
the cathode?

A lightning rod also has to be grounded to work. Wrong?

Wessel



On 27 jan, 14:08, Patrick Turner wrote:
Wessel Dirksen wrote:

On 25 jan, 14:12, Patrick Turner wrote:
Wessel Dirksen wrote:

On 22 dec 2006, 12:30, "Iain Churches" wrote:
"Wessel Dirksen" wrote in oglegroups.com...

Hi RAT's,

I don't know if some of you recall me from about a year ago when I was
tuning in here regularly but I was asking some newbie questions back
then and got great friendly advice. I actually regularly refer to saved
threads from here. I got away from the tubes for awhile because my
first project is working just fine without my messing with it and
because I have been pleasantly distracted by a great gal in my life.
Nice to be back.

My question then: How important is it to raise the top tube's heater
potential in a SRPP? I've read it's supposed to be a noise issue with
the neighboring cathode but I've not had any real noise problems with
this so far. It sounds great. The potential difference doesn't burn
anything up does it?

WesselHi Wessel. Nice to see you posting here again:-)

Many books stress the importance of not exceeding the maximum
permitted cathode to heater potential, especially in SRPP, cathode
follower, mu- follower etc etc.

It can be done simply by making a potential divider of two resistors
adding up to say 1M across the B+ Set the value of the lower
resistor to give you the voltage required (I often use 90V) Remember
that the heater supply must be floating. Decouple the lower resistor
with 0.1µF to ground. Take the lead from this divider to a pair of
100 Ohms resistors, and from these to either side of the heater
supply electrolytic.

Ian,
It appears that by saying "either" side, you mean 100 ohm to both sides
of the heater voltage. Is this so?
Elegant.

Took awhile to back to this. Thanks everyone.Where you have one heater supply for SRPP tubes with low rated
heater-cathode voltages of typically 90V, then the heater supply
can be set up as follows :-

Use 100 ohms from each of the heater winding to a connection point that
is
then also connected to a dc voltage divider so that you have a bias
voltage at about +75V
This means the cathode of the bottom tube is about 75V below the bias
voltage,
and if the top tube cathode is at +150V, then its cathode is 75V above
the bias voltage.
The bias voltage divider should be done with
say 220k and 47k or whatever R values that give the wanted bias voltage
which is half way between top and bottom cathode dc voltages.

The bias point of say +75V should be bypassed to 0V with a
100V rated 100uF.

There is still a possibility that power supply noise will still enter
the
tubes via the stray C between cathode and proximity of ac heater
voltages to the
tube grid connections.

To avoid this, rectify the heater ac to make a well filtered ( CRC ) dc
heater
supply which is then all ungrounded but biased up at +75V or wherever
you want it.

For more info on how to combine SRPP or µ-follower stages and heater
supplies, try readinghttp://www.turneraudio.com.au/preamp-rocket-phono-2005.htmlhttp://www...

The power supply for the tubed phono and line stages is at the lower
section
of the second of the above pages.

Happy Listening,

Patrick Turner.

Thanks for that Patrick. Now this circuit is clear to me.

Anyone know what the heater/cathode potential limit is for the Sovtec
6H30? 100V same as the rest?No, I don't exactly know what the heater-cathode voltage is, but
100V is a safe bet, even when official ratings are higher.

Patrick Turner.





I have done this on several projects with great success.

Regards to all
Iain- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -- Tekst uit oorspronkelijk bericht niet weergeven -- Tekst uit oorspronkelijk bericht weergeven -