[`ZACK`[_2_]]

has anyone used the boot strap diver in tube
outputs?

and what are your your thoughts on this method.


thanks
zack

[Don Pearce[_3_]]

On Sat, 10 Apr 2010 14:12:18 +1000, "`ZACK`"
wrote:

has anyone used the boot strap diver in tube
outputs?

and what are your your thoughts on this method.


It's fine provided you have a reliable method for releasing the lead
weights from your shoes once you reach the bottom. I understand a few
people have drowned because they improvised and got it wrong. The
actual tube output system can be problematic because its safe
operation assumes that your submariner is not overweight. A fat man
can easily get jammed and of course that is it for the rest of the
crew too.

d

[`ZACK`[_2_]]

"Don Pearce" wrote in message
...
On Sat, 10 Apr 2010 14:12:18 +1000, "`ZACK`"
wrote:

has anyone used the boot strap diver in tube
outputs?

and what are your your thoughts on this method.


It's fine provided you have a reliable method for releasing the lead
weights from your shoes once you reach the bottom. I understand a few
people have drowned because they improvised and got it wrong. The
actual tube output system can be problematic because its safe
operation assumes that your submariner is not overweight. A fat man
can easily get jammed and of course that is it for the rest of the
crew too.

d

read the heading it ses tube amps

[Don Pearce[_3_]]

On Sat, 10 Apr 2010 17:53:28 +1000, "`ZACK`"
wrote:


"Don Pearce" wrote in message
...
On Sat, 10 Apr 2010 14:12:18 +1000, "`ZACK`"
wrote:

has anyone used the boot strap diver in tube
outputs?

and what are your your thoughts on this method.


It's fine provided you have a reliable method for releasing the lead
weights from your shoes once you reach the bottom. I understand a few
people have drowned because they improvised and got it wrong. The
actual tube output system can be problematic because its safe
operation assumes that your submariner is not overweight. A fat man
can easily get jammed and of course that is it for the rest of the
crew too.

d

read the heading it ses tube amps

Read the message, it says diver.

d

[`ZACK`[_2_]]

"Don Pearce" wrote in message
...
On Sat, 10 Apr 2010 17:53:28 +1000, "`ZACK`"
wrote:


"Don Pearce" wrote in message
...
On Sat, 10 Apr 2010 14:12:18 +1000, "`ZACK`"
wrote:

has anyone used the boot strap diver in tube
outputs?

and what are your your thoughts on this method.


It's fine provided you have a reliable method for releasing the lead
weights from your shoes once you reach the bottom. I understand a few
people have drowned because they improvised and got it wrong. The
actual tube output system can be problematic because its safe
operation assumes that your submariner is not overweight. A fat man
can easily get jammed and of course that is it for the rest of the
crew too.

d

read the heading it ses tube amps

Read the message, it says diver.

d

you well know what im after, is an answer
on tube amp boot straped drivers, if you dont know
dont reply.

[sparky]

On Apr 10, 11:38*pm, "`ZACK`" wrote:
"Don Pearce" wrote in message

...





On Sat, 10 Apr 2010 17:53:28 +1000, "`ZACK`"
wrote:

"Don Pearce" wrote in message
...
On Sat, 10 Apr 2010 14:12:18 +1000, "`ZACK`"
wrote:

has anyone used the boot strap diver in tube
outputs?

and what are your your thoughts on this method.

It's fine provided you have a reliable method for releasing the lead
weights from your shoes once you reach the bottom. I understand a few
people have drowned because they improvised and got it wrong. The
actual tube output system can be problematic because its safe
operation assumes that your submariner is not overweight. A fat man
can easily get jammed and of course that is it for the rest of the
crew too.

d

read the heading it ses tube amps

Read the message, it says diver.

d

you well know what im after, is an answer
on tube amp boot straped drivers, if you dont know
dont reply.- Hide quoted text -

- Show quoted text -



You really have to watch when you take those tubes diving. The cold
water may shatter the hot glass.

[Patrick Turner]

On Apr 12, 10:49*am, sparky wrote:
On Apr 10, 11:38*pm, "`ZACK`" wrote:





"Don Pearce" wrote in message

...

On Sat, 10 Apr 2010 17:53:28 +1000, "`ZACK`"
wrote:

"Don Pearce" wrote in message
...
On Sat, 10 Apr 2010 14:12:18 +1000, "`ZACK`"
wrote:

has anyone used the boot strap diver in tube
outputs?

and what are your your thoughts on this method.

It's fine provided you have a reliable method for releasing the lead
weights from your shoes once you reach the bottom. I understand a few
people have drowned because they improvised and got it wrong. The
actual tube output system can be problematic because its safe
operation assumes that your submariner is not overweight. A fat man
can easily get jammed and of course that is it for the rest of the
crew too.

d

read the heading it ses tube amps

Read the message, it says diver.

d

you well know what im after, is an answer
on tube amp boot straped drivers, if you dont know
dont reply.- Hide quoted text -

- Show quoted text -

You really have to watch when you take those tubes diving. The cold
water may shatter the hot glass.- Hide quoted text -

Not as interesting as the diving competitions where the shielas enter
the water feet first from 30 feet up.

They can suffer pussy burst if they don't watch out ;-O

Patrick Turner.





- Show quoted text -

[`ZACK`[_2_]]

"Don Pearce" wrote in message
...
On Sat, 10 Apr 2010 14:12:18 +1000, "`ZACK`"
wrote:

has anyone used the boot strap diver in tube
outputs?

and what are your your thoughts on this method.


It's fine provided you have a reliable method for releasing the lead
weights from your shoes once you reach the bottom. I understand a few
people have drowned because they improvised and got it wrong. The
actual tube output system can be problematic because its safe
operation assumes that your submariner is not overweight. A fat man
can easily get jammed and of course that is it for the rest of the
crew too.

d

look if you want to know what a
ac boot strapped driver is click this
http://www.lenardaudio.com/education...ve_amps_3.html

and scroll down the page to the
heading ac boot strapped driver.

[Patrick Turner]

On Apr 13, 6:50*pm, flipper wrote:
On Tue, 13 Apr 2010 16:29:22 +1000, "`ZACK`"





wrote:

"Don Pearce" wrote in message
...
On Sat, 10 Apr 2010 14:12:18 +1000, "`ZACK`"
wrote:

has anyone used the boot strap diver in tube
outputs?

and what are your your thoughts on this method.

It's fine provided you have a reliable method for releasing the lead
weights from your shoes once you reach the bottom. I understand a few
people have drowned because they improvised and got it wrong. The
actual tube output system can be problematic because its safe
operation assumes that your submariner is not overweight. A fat man
can easily get jammed and of course that is it for the rest of the
crew too.

d

look if you want to know what a
ac boot strapped driver is click this
http://www.lenardaudio.com/education...ve_amps_3.html

and scroll down the page to the
heading ac boot strapped driver.

Oh, so that's the kind of bootstrap you're asking about.

I've spiced but not built that version, although I used an AC
bootstrap CCS in the solid state section of the hybrid PC Speaker Amp.

I don't know why they picked 150K/47k. The cathode load will be those
in parallel, then in (AC) parallel with Rk, so all dissimilar value
resistors does is lower the load, and the bootstrapped impedance, from
what equal ones would be: I.E. 100k each.

It's a good driver but, their idealized description notwithstanding,
it isn't "zero distortion." Nothing is "zero distortion."

Indeed you are correct.

A better way for a low Rout driver is to start with a gain stage using
a choke with CT to B+ plus series R from each end of choke to gain
triode anodes. The un-gapped choke would have L = 200H at least so
that is becomes an extremely high impedance load for audio F. THIS
reduces the THD to perhaps 1.5% 3H at 200Vrms anode to anode but no
matter what one does with raising the anode load ohms or with
bootstrapping there will still be the odd order THD of the triodes
even if thw anode load was a CCS. The LTP produced mainly 3H. It is
inherent in the triodes and does not cancel, or is formed because the
gm change in each +/- parts of wave cycles are different, ie, the
increase and decrease in gm at Va = -100V is different to where Va =
+100V, and the discrepancy resolves to 3H.

Using a lone SE tube the THD at 100Vrms from say a 1/2 12AU7 with very
high value RL might be 3%.
The 3H might be 0.3%. But when you have two together in a PP LTP
you'll get maybe 1.5% 3H and virtually no 2H unless the tubes have
differing characteristics, or you have a tail for the LTP which is too
low a resistance. CCS make the best tails for LTP.

The above stage can de direct coupled to 12AU7 CF and Rout is very
low. But when grid current is encountered the low Rout ensures the
coupling caps to output grids will charge up very quickly, amd most
quickly when GNFB is used to that the slightest overload into grid
current causes vicious paralysis because the output stage becomes over
biased for as long as it takes for the RC time constant to allow
discharge of the C. This time constant is much longer than the time
constant of charge up.

For AB2 drive to output tube one has to couple the cathodes of the CF
directly to output grids and bias the output tubes with C coupling &
bias R to the input grid of the CF. This works well until one gets a
CF tube that has a short between anode and grid which can then make an
output tube biased well into saturation and unless suitable protection
or fusing is there then parts such as OPT and PT can become fused.


The bootstrap isn't 'perfect' because, for one, CF gain is less than
one. There will be, therefore, some "audio AC Voltage 'difference'"
across Rl and the current does not "always remains the same" despite
their protestation to the contrary. Loading also lowers it's
effectiveness and the bootstrap falls apart when the following stage
goes into positive grid drive.

Indeed.

In addition, the CF triode is not 'perfect', not operating into a CCS,
and current certainly does vary so it's distortion will alter the
signal into the bootstrap, which contributes to the signal not being
'equal' across Rl.- Hide quoted text -

There is some interaction there which makes the bootstrapping shown at
the Lenard site to be less than perfect and not as good as they make
out.

In the old days when they wanted a low Rout driver they might have
used a pair of EL34 in triode with 1:1 IST to power a number of KT88
in paralell for high power. This gave some drive into class AB2, but
the secondary winding was tied to a low Rout bias supply so baising
remained firm. Its not a perfect class AB2 driver because the grid
current load isn't linear and you get compression effect at high
levels, so you get a lot more 3H in the region between class AB1 and
AB2.
Nobody minded this effect because the grid current region only was
needed for transients, drum beats etc.

One might also use a pair of µ-followers in an LTP where the top CF
tubes offer low Rout and bottom tubes see a load that is bootstrapped.
Such a stage RC coupled to an output stage is awful with grid current.
But very good for AB1.

But balancing the pair of µ-followers in an LTP driver becomes tricky.

Patrick Turner.

[Bret L]

"Pussy burst"?? Is that a new reissue Les Paul?


Anyway, see the Mcintosh MI200.

[Patrick Turner]

On Apr 15, 8:01*pm, Bret L wrote:
"Pussy burst"?? Is that a new reissue Les Paul?

*Anyway, see the Mcintosh MI200.

Naked shielas should beware leaping off diving towers into water below
with legs apart and hitting water feet first.

The resulting outward extensions of the reproduction organs due to
rapid water ingress and pressure increase can cause distress and
reduction of ability to reproduce for an unspecified time after such
experiences.

Patrick Turner.

[Patrick Turner]

On Apr 16, 10:48*pm, flipper wrote:
On Wed, 14 Apr 2010 02:38:19 -0700 (PDT), Patrick Turner





wrote:
On Apr 13, 6:50*pm, flipper wrote:
On Tue, 13 Apr 2010 16:29:22 +1000, "`ZACK`"

wrote:

"Don Pearce" wrote in message
...
On Sat, 10 Apr 2010 14:12:18 +1000, "`ZACK`"
wrote:

has anyone used the boot strap diver in tube
outputs?

and what are your your thoughts on this method.

It's fine provided you have a reliable method for releasing the lead
weights from your shoes once you reach the bottom. I understand a few
people have drowned because they improvised and got it wrong. The
actual tube output system can be problematic because its safe
operation assumes that your submariner is not overweight. A fat man
can easily get jammed and of course that is it for the rest of the
crew too.

d

look if you want to know what a
ac boot strapped driver is click this
http://www.lenardaudio.com/education...ve_amps_3.html

and scroll down the page to the
heading ac boot strapped driver.

Oh, so that's the kind of bootstrap you're asking about.

I've spiced but not built that version, although I used an AC
bootstrap CCS in the solid state section of the hybrid PC Speaker Amp.

I don't know why they picked 150K/47k. The cathode load will be those
in parallel, then in (AC) parallel with Rk, so all dissimilar value
resistors does is lower the load, and the bootstrapped impedance, from
what equal ones would be: I.E. 100k each.

It's a good driver but, their idealized description notwithstanding,
it isn't "zero distortion." Nothing is "zero distortion."

Indeed you are correct.

A better way for a low Rout driver is to start with a gain stage using
a choke with CT to B+ plus series R from each end of choke to gain
triode anodes. The un-gapped choke would have L = 200H at least so
that is becomes an extremely high impedance load for audio F. THIS
reduces the THD to perhaps 1.5% 3H at 200Vrms anode to anode but no
matter what one does with raising the anode load ohms or with
bootstrapping there will still be the odd order THD of the triodes
even if thw anode load was a CCS. The LTP produced mainly 3H. It is
inherent in the triodes and does not cancel, or is formed because the
gm change in each +/- parts of wave cycles are different, ie, the
increase and decrease in gm at Va = -100V is different to where Va =
+100V, and the discrepancy resolves to 3H.

Yes. The advantage, of course, is the boostrap doesn't require
expensive chokes nor weigh a hundred pounds.

Bootstrapping works fine when you don't ask too much voltage from the
circuit.
The main purpose of a bootstrap in a preamp is to load the gain triode
with a very high RL and boost its gain to near µ and thus to where THD
is minimal.
In a power amp such as a McIntosh they have a 12BH7 in an LTP driver
with its anode RL of 13k taken to taps on the OPT so that from the
BH&'s point of view its as if the BHT had a much higher B+ suply than
it actually does. The THD at the tap on the OPT is fed back positively
to the BH7 anode through the 13k anode RL. But because the output
stage gain is so low and because the BH7 Ra is only about 5k, the
amount of boost to THD with the PFB is not high and possibly no worse
than if you had an effective load on the BH7 which was much lower
because there was no bootstrapping.
But I still prefrer the CT choke because you can get a driver LTP to
have a higher RL than you'd get with the McIntosh syle of
bootstrapping and there is NO PFB. The choke involved need not be a
huge heavy or expensive thing. In my 8585 I used a 10mm stack of 32mm
tongue GOSS with 8,000 turns of 0.15mm dia wire and that gave very
high L and high Z across the audio band.


Speaking of CT chokes, though, did you ever try that solid state
substitute I came up with a couple years ago?

You have got me. I don't recal exactly what that was.

I recall none of us could come up with an SS equivalent of a CT choke
so that if you pulled the voltage down at one anode terminal the
voltage at the other anode terminal would rise, like a see saw
arrangement, so that if you wanted to one could make the equivalent of
an SS interstage transformer.

But I have now used a pair of independant CCS on each side of an LTP
and with C coupled Rg biasing resistance to the OP stage and thus this
Rg can be a nice low value of say 100k max to help prevent excessive
+ve grids when tube age.
I found a way to series two MJ340 to make a CCS so that the voltage
between B+ and anode is evenly spread over each collector to emitter
of each bjt, so that where you have B+ of say 500V and the tube anode
has a short to 0V then you have only 250V across a bjt rated for 300V.
KSE340 is slightly better rated BTW.

I never take the output signal from any low Rout part of the SS
circuitry because then you have a hybrid circuit.

When one uses EL84 routinely as driver tubes with 16mA of Ia the Ra is
only 2k2, and low enough not to need any bootstrapping. In a line
preamp, There is nothing to stop anyone using an EL84 as a triode in a
gain stage with output straight off the anode via a 2uF cap. Simple
and effective, and gain up to 17 in most samples.

Using a lone SE tube the THD at 100Vrms from say a 1/2 12AU7 with very
high value RL might be 3%.
The 3H might be 0.3%. But when you have two together in a PP LTP
you'll get maybe 1.5% 3H and virtually no 2H unless the tubes have
differing characteristics, or you have a tail for the LTP which is too
low a resistance. CCS make the best tails for LTP.

The above stage can de direct coupled to 12AU7 CF and Rout is very
low. But when grid current is encountered the low Rout ensures the
coupling caps to output grids will charge up very quickly, amd most
quickly when GNFB is used to that the slightest overload into grid
current causes vicious paralysis because the output stage becomes over
biased for as long as it takes for the RC time constant to allow
discharge of the C. This time constant is much longer than the time
constant of charge up.

Yes. In most case I don't think it's worth it to inject a CF if you're
RC coupling although I suppose the theory is it's only for the
occasional transient peak.

For AB2 drive to output tube one has to couple the cathodes of the CF
directly to output grids and bias the output tubes with C coupling &
bias R to the input grid of the CF. This works well until one gets a
CF tube that has a short between anode and grid which can then make an
output tube biased well into saturation and unless suitable protection
or fusing is there then parts such as OPT and PT can become fused.

That's what I'm planning to do, except MOSFETs for the CF, in the
triode mode amp I keep thinking about but never quite get around to
finishing. Maybe this year.

Many ppl have used mosfets for impedance converting buffers.

The bootstrap isn't 'perfect' because, for one, CF gain is less than
one. There will be, therefore, some "audio AC Voltage 'difference'"
across Rl and the current does not "always remains the same" despite
their protestation to the contrary. Loading also lowers it's
effectiveness and the bootstrap falls apart when the following stage
goes into positive grid drive.

Indeed.

In addition, the CF triode is not 'perfect', not operating into a CCS,
and current certainly does vary so it's distortion will alter the
signal into the bootstrap, which contributes to the signal not being
'equal' across Rl.- Hide quoted text -

There is some interaction there which makes the bootstrapping shown at
the Lenard site to be less than perfect and not as good as they make
out.

In the old days when they wanted a low Rout driver they might have
used a pair of EL34 in triode with 1:1 IST to power a number of KT88
in paralell for high power. This gave some drive into class AB2, but
the secondary winding was tied to a low Rout bias supply so baising
remained firm. Its not a perfect class AB2 driver because the grid
current load isn't linear and you get compression effect at high
levels, so you get a lot more 3H in the region between class AB1 and
AB2.
Nobody minded this effect because the grid current region only was
needed for transients, drum beats etc.

Yep, that's the idea and it's certainly less distortion than the flat
out clip you'd get without it.

yes



Patrick Turner.



One might also use a pair of µ-followers in an LTP where the top CF
tubes offer low Rout and bottom tubes see a load that is bootstrapped.
Such a stage RC coupled to an output stage is awful with grid current.
But very good for AB1.

But balancing the pair of µ-followers in an LTP driver becomes tricky.

Patrick Turner.- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

[Paul D. Spiegel]

Patrick Turner wrote:
But I still prefrer the CT choke because you can get a driver LTP to
have a higher RL than you'd get with the McIntosh syle of
bootstrapping and there is NO PFB. The choke involved need not be a
huge heavy or expensive thing. In my 8585 I used a 10mm stack of 32mm
tongue GOSS with 8,000 turns of 0.15mm dia wire and that gave very
high L and high Z across the audio band.

I needed huge driver voltage swing for PP CF project and chose a CT
choke for the driver. Bootstrapping seems like an inelegant solution.
If NFB broadens bandwidth and decreases distortion then PFB...

I used a Lundahl 1667/5ma as the load for a 6BL7 dual triode with a CCS
tail. B+ is 450v and the CCS is set for 15ma per triode. At 1Khz I
measure ~440Vrms before clipping.

At the time, the Lundahl CT chokes were $85 USD from K&K Audio. Now I
think they are near $200 USD which makes this a more difficult choice.

I've wondered about using a much less expensive standard PP Hi-Z primary
transformer with a resistor terminated secondary. Has anyone ever tried
this? Should it work?

- Paul

[Patrick Turner]

On Apr 20, 4:17*pm, "Paul D. Spiegel" wrote:
Patrick Turner wrote:
But I still prefrer the CT choke because you can get a driver LTP to
have a higher RL than you'd get with the McIntosh syle of
bootstrapping and there is NO PFB. The choke involved need not be a
huge heavy or expensive thing. In my 8585 I used a 10mm stack of 32mm
tongue GOSS with 8,000 turns of 0.15mm dia wire and that gave very
high L and high Z across the audio band.

I needed huge driver voltage swing for PP CF project and chose a CT * * * * * *
choke for the driver. *Bootstrapping seems like an inelegant solution.
If NFB broadens bandwidth and decreases distortion then PFB...

The increase of THD and reduction of BW by PFB as used in a McIntosh
is quite small because the output stage gain is so low. The ill
effects of the PFB are compensated for by the global NFB. Its like
having one step backwards and 5 steps forward to be a total of 4 steps
forward.

I used a Lundahl 1667/5ma as the load for a 6BL7 dual triode with a CCS
tail. *B+ is 450v and the CCS is set for 15ma per triode. *At 1Khz I
measure ~440Vrms before clipping.

At the time, the Lundahl CT chokes were $85 USD from K&K Audio. *Now I
think they are near $200 USD which makes this a more difficult choice.

I just wind whatever I need and the cost is minimal...

I've wondered about using a much less expensive standard PP Hi-Z primary * * * *
transformer with a resistor terminated secondary. *Has anyone ever tried
this? *Should it work?

This would work well except that nearly all OPTs have nowhere near
enough inductance to allow good bass performance.

If you have say a pair of EL84 in triode on each side of a driver LTP
each with Idc = 20mA, then Ra-a = 4k4 approx.
I set the EL84 up with say at least 4k7 R to each end of the choke, so
ther is 100Vdc across each 4k7, and if Ea = 280Vdc, the the B+ will
about 400Vdc allowing for Ek and winding resistances if te grids are
biased from 0V and the LTP tail is a CCS or resistor taken down to
-100V.

Now the total resistance in series with Lp = 4k7 + 4k7 + 4k4 = 13k8
and one wants the XLp = 13k8 at say 20Hz if possible so Lp must be
109H. The response at the anode will shelve down from maximum at say
1kHz as F drops below 100Hz so that with 3Hz the L has so little XL
that the load is mainly 4k7, which allows a considerable v swing
without reliance on the choke. THD will be higher but its at such a
low F it does not matter.
The 109H is just nominal; the more thye better because XL varies with
voltage levels and at low levels L is small.
And most listening is done at low level. I found the 8,000 turns on a
10mm stack of 32T material was OK for 2 x EL84.
The L was **much more** than you'd ever get on many OPTs, most of
which have been designed by accountants.

The other alternative to reducing the worst effects produced by having
to put power intoa dc carrying resistance of a driver stage is to add
some diodes and a couple of electro C to make a driver stage B+
voltage of double the existing B+ for the output stage so that the
driver B+ is raised from the usual +400V to +650V. The RLdc then
becomes a much higher ohm value for the same Iadc and when you do the
load lines you'll see that the overall combined ac and dc load isa
flatter line which makes the LTP produce more Vo at a lower THD.

Parick Turner.


- Paul

[Patrick Turner]

On Apr 20, 4:17*pm, "Paul D. Spiegel" wrote:
Patrick Turner wrote:
But I still prefrer the CT choke because you can get a driver LTP to
have a higher RL than you'd get with the McIntosh syle of
bootstrapping and there is NO PFB. The choke involved need not be a
huge heavy or expensive thing. In my 8585 I used a 10mm stack of 32mm
tongue GOSS with 8,000 turns of 0.15mm dia wire and that gave very
high L and high Z across the audio band.

I needed huge driver voltage swing for PP CF project and chose a CT * * * * * *
choke for the driver. *Bootstrapping seems like an inelegant solution.
If NFB broadens bandwidth and decreases distortion then PFB...

I used a Lundahl 1667/5ma as the load for a 6BL7 dual triode with a CCS
tail. *B+ is 450v and the CCS is set for 15ma per triode. *At 1Khz I
measure ~440Vrms before clipping.

At the time, the Lundahl CT chokes were $85 USD from K&K Audio. *Now I
think they are near $200 USD which makes this a more difficult choice.

I've wondered about using a much less expensive standard PP Hi-Z primary * * * *
transformer with a resistor terminated secondary. *Has anyone ever tried
this? *Should it work?

- Paul

And BTW, there should be no RL loading an OPT used for providing a
high Z load through which dc can be fed to the LTP triodes. The whole
point of the L is to get RL as high as possible. So if any R is used
it should be in series with L not in in shunt across L.

Patrick Turner.