Gentlemen,

here is another project I completed (at last...).

http://www.tubes.mynetcologne.de/roe...e/6v6se_e.html

It was intended as a birthday present for a friend to be used
in a small room with small bookshelf speakers.

It is a 4,5 Watt/channel pentode/pentode single ended integrated
which gives a damn on all this "single ended triode without any
negative feedback" madness.

Instead, it is a no-fuss, solidly designed all-pentode
circuit amp, which simply does what it is expected to do.

If you are interested in the circuit development process, you can
find it described extensively in the form of a moderate level
walkthrough, starting at:

http://www.tubes.mynetcologne.de/roe...ematics_e.html

May this walkthrough help other tube DIY amp enthusiasts construct
and enjoy their own DIY amps.

I would like to thank the crowd at
"The G33k Zone" http://geek.scorpiorising.ca/GeeK_ZonE/index.php
who helped a lot in making the schematics section walkthrough
come true.

I wish you and your relatives a great new year!

Tom

--
The opposite of a correct statement is a false statement. But the
opposite of a profound truth may well be another profound truth.
- Niels Bohr

On Sat, 31 Dec 2005 11:53:43 +0100, Tom Schlangen
wrote:

Gentlemen,

here is another project I completed (at last...).

http://www.tubes.mynetcologne.de/roe...e/6v6se_e.html

It was intended as a birthday present for a friend to be used
in a small room with small bookshelf speakers.

It is a 4,5 Watt/channel pentode/pentode single ended integrated
which gives a damn on all this "single ended triode without any
negative feedback" madness.

Instead, it is a no-fuss, solidly designed all-pentode
circuit amp, which simply does what it is expected to do.

If you are interested in the circuit development process, you can
find it described extensively in the form of a moderate level
walkthrough, starting at:

http://www.tubes.mynetcologne.de/roe...ematics_e.html

May this walkthrough help other tube DIY amp enthusiasts construct
and enjoy their own DIY amps.

I would like to thank the crowd at
"The G33k Zone" http://geek.scorpiorising.ca/GeeK_ZonE/index.php
who helped a lot in making the schematics section walkthrough
come true.

I wish you and your relatives a great new year!

Tom

Just out of interest, how did you wire the 6V6 as a pentode? It is a
beam tetrode.

d

Pearce Consulting
http://www.pearce.uk.com

Don Pearce wrote:

On Sat, 31 Dec 2005 11:53:43 +0100, Tom Schlangen
wrote:

Gentlemen,

here is another project I completed (at last...).

http://www.tubes.mynetcologne.de/roe...e/6v6se_e.html

It was intended as a birthday present for a friend to be used
in a small room with small bookshelf speakers.

It is a 4,5 Watt/channel pentode/pentode single ended integrated
which gives a damn on all this "single ended triode without any
negative feedback" madness.

Instead, it is a no-fuss, solidly designed all-pentode
circuit amp, which simply does what it is expected to do.

If you are interested in the circuit development process, you can
find it described extensively in the form of a moderate level
walkthrough, starting at:

http://www.tubes.mynetcologne.de/roe...ematics_e.html

May this walkthrough help other tube DIY amp enthusiasts construct
and enjoy their own DIY amps.

I would like to thank the crowd at
"The G33k Zone" http://geek.scorpiorising.ca/GeeK_ZonE/index.php
who helped a lot in making the schematics section walkthrough
come true.

I wish you and your relatives a great new year!

Tom

Just out of interest, how did you wire the 6V6 as a pentode? It is a
beam tetrode.

d

Pearce Consulting
http://www.pearce.uk.com

Picky! Picky!

Very Pretty!

Cheers, John Stewart

John Stewart wrote:

Don Pearce wrote:

On Sat, 31 Dec 2005 11:53:43 +0100, Tom Schlangen
wrote:

Gentlemen,

here is another project I completed (at last...).

http://www.tubes.mynetcologne.de/roe...e/6v6se_e.html

It was intended as a birthday present for a friend to be used
in a small room with small bookshelf speakers.

It is a 4,5 Watt/channel pentode/pentode single ended integrated
which gives a damn on all this "single ended triode without any
negative feedback" madness.

Instead, it is a no-fuss, solidly designed all-pentode
circuit amp, which simply does what it is expected to do.

If you are interested in the circuit development process, you can
find it described extensively in the form of a moderate level
walkthrough, starting at:

http://www.tubes.mynetcologne.de/roe...ematics_e.html

May this walkthrough help other tube DIY amp enthusiasts construct
and enjoy their own DIY amps.

I would like to thank the crowd at
"The G33k Zone" http://geek.scorpiorising.ca/GeeK_ZonE/index.php
who helped a lot in making the schematics section walkthrough
come true.

I wish you and your relatives a great new year!

Tom

Just out of interest, how did you wire the 6V6 as a pentode? It is a
beam tetrode.

d

Pearce Consulting
http://www.pearce.uk.com

Picky! Picky!

Very Pretty!

Cheers, John Stewart

Whose OPT's? And what about the chassis & cover, all in beautiful color.
Do you do that yourself?

Cheers, John Stewart

Hi Don,

Just out of interest, how did you wire the 6V6 as a pentode?
It is a beam tetrode.

I have forgotten to include the tetrode-pentode conversion in
the walkthru, indeed!

On the other hand, probably everyone interested in tube tech has
done that already I suppose, since actually this is quite simple
to do. If you have not yet, here is a short how-to for you:

Take a glas envelope 6V6, a hammer and smash the glas envelope
gently (you could use a metal envelope 6V6, but smashing glas
is so much more fun). Take care capturing the vacuum, since we
will need it later. Remove the plate structure and the beam
forming plates. Solder some windings of fine wire to the posts
that did hold the beam forming plates to make the supressor grid.
Use one of the formerly not connected pins in the base to make a
connection to the new supressor grid. Take a suitable glas tube
(neck of a clear wine bottle comes to mind) and a torch. Use the
torch to carefully melt and join the bottle neck to the base,
while putting the vacuum back in again (no problem to re-use the
previously used vacuum here - do not trust audiophools that try
to sell you special new old stock vacuum from TFK or Mullard
plants - those most likely are fakes to rip your money). Last
but not least, at the socket, wire the new supressor grid pin
to the cathode pin.

Wasn't that hard, wasn't it?

Tom

--
The opposite of a correct statement is a false statement. But the
opposite of a profound truth may well be another profound truth.
- Niels Bohr

Hi John,

Whose OPT's?

These are from www.roehrentechnik.de, by Gerd Reinhöfer.

And what about the chassis & cover, all in beautiful color.
Do you do that yourself?

Yes, so far I did all the chassis work and painting of my amps
myself, except for a single quick hack project, where I used
a Hammond case.

Actually, the paint on this chassis (like the 807PP/UL at my
homepage, which is the best chassis I think I made so far,
multilayered "British Racing Green") is not brushed nor spayed,
but "drawn" by hand. A retired piano maker told me how to do
that. After some decades and square miles of trying and training,
it isn't that hard to do and gives excellent results.

Joking aside, "drawing" laquer really isn't that hard, given
a bit patience and experience.

Tom

--
Life: All in all a bad game, but graphics are really good.

"Tom Schlangen" wrote in message
...
Hi John,

Whose OPT's?

These are from www.roehrentechnik.de, by Gerd Reinhöfer.

And what about the chassis & cover, all in beautiful color.
Do you do that yourself?

Yes, so far I did all the chassis work and painting of my amps
myself, except for a single quick hack project, where I used
a Hammond case.

Actually, the paint on this chassis (like the 807PP/UL at my
homepage, which is the best chassis I think I made so far,
multilayered "British Racing Green") is not brushed nor spayed,
but "drawn" by hand. A retired piano maker told me how to do
that. After some decades and square miles of trying and training,
it isn't that hard to do and gives excellent results.

Joking aside, "drawing" laquer really isn't that hard, given
a bit patience and experience.

Tom

Hello Tom. Excellent job. congratulations:-)
It is pleasing to note that interest in tube audio is growing steadily.
Projects like yours do much to encourage new builders.

Iain

Super project, Tom. Thanks for sharing. I know it was a birthday gift,
but would you be prepared to publish a rough cost breakdown. It may be
of interest to the other Tom, who is just starting.

Andre Jute

Tom Schlangen wrote:
Gentlemen,

here is another project I completed (at last...).

http://www.tubes.mynetcologne.de/roe...e/6v6se_e.html

It was intended as a birthday present for a friend to be used
in a small room with small bookshelf speakers.

It is a 4,5 Watt/channel pentode/pentode single ended integrated
which gives a damn on all this "single ended triode without any
negative feedback" madness.

Instead, it is a no-fuss, solidly designed all-pentode
circuit amp, which simply does what it is expected to do.

If you are interested in the circuit development process, you can
find it described extensively in the form of a moderate level
walkthrough, starting at:

http://www.tubes.mynetcologne.de/roe...ematics_e.html

May this walkthrough help other tube DIY amp enthusiasts construct
and enjoy their own DIY amps.

I would like to thank the crowd at
"The G33k Zone" http://geek.scorpiorising.ca/GeeK_ZonE/index.php
who helped a lot in making the schematics section walkthrough
come true.

I wish you and your relatives a great new year!

Tom

--
The opposite of a correct statement is a false statement. But the
opposite of a profound truth may well be another profound truth.
- Niels Bohr

"Don Pearce" wrote

Just out of interest, how did you wire the 6V6 as a pentode? It is
a
beam tetrode.

So can't a 6V6 be in pentode mode? I have never heard of beam
tetrode mode.

cheers, Ian

"Tom Schlangen" a écrit dans le message de news:
...
Hi Don,

Just out of interest, how did you wire the 6V6 as a pentode?
It is a beam tetrode.

I have forgotten to include the tetrode-pentode conversion in
the walkthru, indeed!

On the other hand, probably everyone interested in tube tech has
done that already I suppose, since actually this is quite simple
to do. If you have not yet, here is a short how-to for you:

Take a glas envelope 6V6, a hammer and smash the glas envelope
gently (you could use a metal envelope 6V6, but smashing glas
is so much more fun). Take care capturing the vacuum, since we
will need it later. Remove the plate structure and the beam
forming plates. Solder some windings of fine wire to the posts
that did hold the beam forming plates to make the supressor grid.
Use one of the formerly not connected pins in the base to make a
connection to the new supressor grid. Take a suitable glas tube
(neck of a clear wine bottle comes to mind) and a torch. Use the
torch to carefully melt and join the bottle neck to the base,
while putting the vacuum back in again (no problem to re-use the
previously used vacuum here - do not trust audiophools that try
to sell you special new old stock vacuum from TFK or Mullard
plants - those most likely are fakes to rip your money). Last
but not least, at the socket, wire the new supressor grid pin
to the cathode pin.

Wasn't that hard, wasn't it?

;))) So true


Tom

--
The opposite of a correct statement is a false statement. But the
opposite of a profound truth may well be another profound truth.
- Niels Bohr

Ian Iveson wrote:

"Don Pearce" wrote

Just out of interest, how did you wire the 6V6 as a pentode? It is
a
beam tetrode.

So can't a 6V6 be in pentode mode? I have never heard of beam
tetrode mode.

A 6V6 *is* a beam tetrode. It isn't actually a pentode.

Graham

Hi Andre,

but would you be prepared to publish a rough
cost breakdown. It may be of interest to the
other Tom, who is just starting.

Now this is really hard to tell, since the only
parts I purchased were the OPTs (33 Euro a piece)
the two 6SJ7 tubes, four 68pF styroflex condensers
and some sheets of abrasive paper to prepare for
the painting.

Everything else I had already in various drawers,
like the PT, tube sockets, 6V6 valves, speaker posts,
input jacks, resistors, condensors, switches,
solder strips, IEC jack, fuses + holders, screws,
grommets, shims, metal sheets for the chassis, the
paint, wires, whatelse.

No boutique parts were used, just generic carbon
comp resistors, a few wirewounds, standard Wima MKS
and MKP condensors.

One should not underestimate the costs for all
those small parts, especially if one is mad enough
(or has no other chance than) to buy screws at DIY
markets, packed to 4 pieces in blister display
packages, for 2 Euro a packet ...

Moreover, one should not underestimate the costs
of tools and measuring gear when starting. Especially
if one wants to make the chassis completely DIY and
wants to measure through the circuit and optimize
frequency dependent feedback networks.

When I would be asked what I consider to be the most
essential tools for tube DIY in my workshop, I would
say, 1st a real good soldering iron and 2nd, a trusty
VTVM (yes, a VTVM, not a DVM. I was luckily enough to
get a HP410C w/ HP11036A AC probe this christmas,
but a simple Heathkit IM-18E or comparable, available
at Ebay for 20-30 Euros or something, will do okay).

But back to your question: As a rough estimate I would
say it would take about 150 Euros in parts to duplicate
this little amp screw for screw, if one has to buy all
the parts, including paint and whatelse. Again, the
necessary tools are not included in these 150 Euros,
of course.

Tom

--
The first rule of magick is simple: Don't waste your time
waving your hands and hoping, when a rock or club will do.

Tom Schlangen wrote:

No boutique parts were used, just generic carbon
comp resistors,

Do you actually mean *carbon composition* resistors ? The ones sealed
with wax or plain ordinary carbon film that have been made for the
last 40+ yrs ?

Graham

Tom Schlangen wrote:

Hi Andre,

but would you be prepared to publish a rough
cost breakdown. It may be of interest to the
other Tom, who is just starting.

Now this is really hard to tell, since the only
parts I purchased were the OPTs (33 Euro a piece)
the two 6SJ7 tubes, four 68pF styroflex condensers
and some sheets of abrasive paper to prepare for
the painting.

Everything else I had already in various drawers,
like the PT, tube sockets, 6V6 valves, speaker posts,
input jacks, resistors, condensors, switches,
solder strips, IEC jack, fuses + holders, screws,
grommets, shims, metal sheets for the chassis, the
paint, wires, whatelse.

No boutique parts were used, just generic carbon
comp resistors, a few wirewounds, standard Wima MKS
and MKP condensors.

One should not underestimate the costs for all
those small parts, especially if one is mad enough
(or has no other chance than) to buy screws at DIY
markets, packed to 4 pieces in blister display
packages, for 2 Euro a packet ...

Moreover, one should not underestimate the costs
of tools and measuring gear when starting. Especially
if one wants to make the chassis completely DIY and
wants to measure through the circuit and optimize
frequency dependent feedback networks.

When I would be asked what I consider to be the most
essential tools for tube DIY in my workshop, I would
say, 1st a real good soldering iron and 2nd, a trusty
VTVM (yes, a VTVM, not a DVM. I was luckily enough to
get a HP410C w/ HP11036A AC probe this christmas,
but a simple Heathkit IM-18E or comparable, available
at Ebay for 20-30 Euros or something, will do okay).

But back to your question: As a rough estimate I would
say it would take about 150 Euros in parts to duplicate
this little amp screw for screw, if one has to buy all
the parts, including paint and whatelse. Again, the
necessary tools are not included in these 150 Euros,
of course.

Tom

--
The first rule of magick is simple: Don't waste your time
waving your hands and hoping, when a rock or club will do.

Looks like your major investment in this one is your time. But a very
good & I'm sure satisfying result!

Cheers, John Stewart

Hi Graham,

you are right, I mixed that up - I meant carbon film
resistors, indeed.

Tom

--
If in doubt, mumble.

Hi John,

Looks like your major investment in this one is
your time.

Indeed. Often, I experiment around at the breadboard
a long time w/o having a clear aim, trying this & that
and making notes. Until suddenly I think to myself:

"Now its time to actually _build_ and _finish_ something".
Which, once decided, goes ahead quite fast.

The most work in this project was writing down the
circuit design walkthru for others to help and enjoy,
the actual amp is almost only a by-product of that
story.

Tom

--
Life: All in all a bad game, but graphics are really good.

Very nice, I would like to know more about this hand drawn painting
technique.

Tom Schlangen wrote:
Gentlemen,

here is another project I completed (at last...).

http://www.tubes.mynetcologne.de/roe...e/6v6se_e.html

It was intended as a birthday present for a friend to be used
in a small room with small bookshelf speakers.

It is a 4,5 Watt/channel pentode/pentode single ended integrated
which gives a damn on all this "single ended triode without any
negative feedback" madness.

Instead, it is a no-fuss, solidly designed all-pentode
circuit amp, which simply does what it is expected to do.

If you are interested in the circuit development process, you can
find it described extensively in the form of a moderate level
walkthrough, starting at:

http://www.tubes.mynetcologne.de/roe...ematics_e.html

May this walkthrough help other tube DIY amp enthusiasts construct
and enjoy their own DIY amps.

I would like to thank the crowd at
"The G33k Zone" http://geek.scorpiorising.ca/GeeK_ZonE/index.php
who helped a lot in making the schematics section walkthrough
come true.

I wish you and your relatives a great new year!

Tom

I agree, Lou, very nice work indeed! I would also like to know more
about the painting technique.

Happy New Ears (bows to Al)

Raymond

Lou deGonzague wrote:
Very nice, I would like to know more about this hand drawn painting
technique.

Tom Schlangen wrote:

Gentlemen,

here is another project I completed (at last...).

http://www.tubes.mynetcologne.de/roe...e/6v6se_e.html

It was intended as a birthday present for a friend to be used
in a small room with small bookshelf speakers.

It is a 4,5 Watt/channel pentode/pentode single ended integrated
which gives a damn on all this "single ended triode without any
negative feedback" madness.

Instead, it is a no-fuss, solidly designed all-pentode
circuit amp, which simply does what it is expected to do.

If you are interested in the circuit development process, you can
find it described extensively in the form of a moderate level
walkthrough, starting at:

http://www.tubes.mynetcologne.de/roe...ematics_e.html

May this walkthrough help other tube DIY amp enthusiasts construct
and enjoy their own DIY amps.

I would like to thank the crowd at
"The G33k Zone" http://geek.scorpiorising.ca/GeeK_ZonE/index.php
who helped a lot in making the schematics section walkthrough
come true.

I wish you and your relatives a great new year!

Tom

On Sat, 31 Dec 2005 18:23:34 -0600, Raymond Koonce
wrote:

I agree, Lou, very nice work indeed! I would also like to know more
about the painting technique.


AOLMe too!!!!/AOL

- YD.

--
Remove HAT if replying by mail.

Tom Alaerts wrote:

Those are very interesting pages which you published and indeed the
combination of amp theory and practical construction that I am looking
for.
And the project price seems ok, without the specific tools: what is a
VTVM? I have a simple digital multimeter. That's not good enough?

An ancient acronym for valve test voltmeter. Fron the days when that meant
a moving coil meter with tube buffer.

A modern digital multimeter is just fine ( unless you reckon the tube will
enhance your readings )


Graham

Tom Alaerts wrote:

Those are very interesting pages which you published and indeed the
combination of amp theory and practical construction that I am looking for.
And the project price seems ok, without the specific tools: what is a
VTVM? I have a simple digital multimeter. That's not good enough?

Vacuum Tube Volt Meter

For most of my projects, a DMM works fine, but for measuring very small
resistances, my VTVM can't be beat. Works great for AC voltage
measurements at various frequencies too.

Raymond


Tom

snip

Pooh Bear said:

And the project price seems ok, without the specific tools: what is a
VTVM? I have a simple digital multimeter. That's not good enough?

An ancient acronym for valve test voltmeter. Fron the days when that meant
a moving coil meter with tube buffer.


[nit-picking mode]
Ahem....a Vacuum Tube Volt Meter.
[/nitpicking mode]


A modern digital multimeter is just fine ( unless you reckon the tube will
enhance your readings )


An analog meter can be an advantage in certain situations, e.g.
indicating a trend instead of an absolute value.

--

"Audio as a serious hobby is going down the tubes."
- Howard Ferstler, 25/4/2005

Sander deWaal wrote:

Pooh Bear said:

And the project price seems ok, without the specific tools: what is a
VTVM? I have a simple digital multimeter. That's not good enough?

An ancient acronym for valve test voltmeter. Fron the days when that meant
a moving coil meter with tube buffer.

[nit-picking mode]
Ahem....a Vacuum Tube Volt Meter.
[/nitpicking mode]

Lol.

Since Valves were never known as vacuum tubes here, I guess that's a UK
alternative name.

A modern digital multimeter is just fine ( unless you reckon the tube will
enhance your readings )

An analog meter can be an advantage in certain situations, e.g.
indicating a trend instead of an absolute value.

Very true. The Fluke 80 something series I use has a bargraph on the LCD
display but it's no substitute for a needle in that application.

Graham

In article , Tom Schlangen
wrote:

Gentlemen,

here is another project I completed (at last...).

http://www.tubes.mynetcologne.de/roe...e/6v6se_e.html

It was intended as a birthday present for a friend to be used
in a small room with small bookshelf speakers.

It is a 4,5 Watt/channel pentode/pentode single ended integrated
which gives a damn on all this "single ended triode without any
negative feedback" madness.

Instead, it is a no-fuss, solidly designed all-pentode
circuit amp, which simply does what it is expected to do.

If you are interested in the circuit development process, you can
find it described extensively in the form of a moderate level
walkthrough, starting at:

http://www.tubes.mynetcologne.de/roe...ematics_e.html

May this walkthrough help other tube DIY amp enthusiasts construct
and enjoy their own DIY amps.


Hi Tom,

That's a great project, and it is good to see someone using pentodes in
place of the obligatory triodes.

I have only one major complaint about the walk through, which is that the
section on the choice of output tube, and its operating point, doesn't
really discuss alternatives to the 6V6 and the chosen operating point. It
gave me the impression that the real reason for the choice of the 6V6 was
because you like the tube and had some in your drawer, nothing wrong that,
or the tube, but it would have been better to either drop the pretense of
a comparison, or provide some discussion of the alternatives.

With regard to the 6V6 operating point, the 250 volt operating point would
have also worked with the given transformer using the 5.2k primary tap.
The inductance argument in favor of the 315 volt operating point is a
false one because the inductance reflected to the secondary remains the
same with either the 5.2k or 8.2k primary tapping.

With regard to other possible octal base tubes, it would appear that the
EL34/6CA7 would also work with the given transformer in either of two
operating modes. The first would be to operate a EL34 in triode mode.
The second would be to use the EL34 in pentode mode with a lower than
normal screen voltage giving a lower current high impedance operating
point suitable for a 8.2k load.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

Pooh Bear wrote

So can't a 6V6 be in pentode mode? I have never heard of beam
tetrode mode.

A 6V6 *is* a beam tetrode. It isn't actually a pentode.

Obviously.

My comment concerns not what it "*is*", but what *mode* it is *in*.

The original post nowhere claims AFAIK that a 6V6 is a pentode.

It says it is a pentode amp. That is, the output valves are operated
in pentode mode.

"Beam tetrode" is not a mode, it is a kind of valve.

"Pentode" is a kind of valve too. It is also a mode of operation,
which can be applied to pentode valves or to beam tetrode valves.

Hope this makes my comment clear.

cheers, Ian

"Pooh Bear" wrote in message
...
:
:
: Ian Iveson wrote:
:
: "Don Pearce" wrote
:
: Just out of interest, how did you wire the 6V6 as a pentode? It is
: a
: beam tetrode.
:
: So can't a 6V6 be in pentode mode? I have never heard of beam
: tetrode mode.
:
: A 6V6 *is* a beam tetrode. It isn't actually a pentode.
:
: Graham
:
ok, you've earned the duh-of-the-month award. happy new year ;-)
Rudy

On Sat, 31 Dec 2005 14:31:44 +0100, Tom Schlangen burbled:

snip

Yes, so far I did all the chassis work and painting of my amps myself,
except for a single quick hack project, where I used a Hammond case.

Actually, the paint on this chassis (like the 807PP/UL at my homepage,
which is the best chassis I think I made so far, multilayered "British
Racing Green") is not brushed nor spayed, but "drawn" by hand. A retired
piano maker told me how to do that. After some decades and square miles of
trying and training, it isn't that hard to do and gives excellent results.

Joking aside, "drawing" laquer really isn't that hard, given a bit
patience and experience.


That is gorgeous.... :-)
And using such a lovely old valve too - I like the 807 but haven't got any
at present. The last one had a bit of a mechanical problem & the vacuum
genie escaped... :-(


--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info
Web: http://projectedsound.tk

On Sat, 31 Dec 2005 07:15:03 -0500, John Stewart
wrote:



Don Pearce wrote:

On Sat, 31 Dec 2005 11:53:43 +0100, Tom Schlangen
wrote:

Gentlemen,

here is another project I completed (at last...).

http://www.tubes.mynetcologne.de/roe...e/6v6se_e.html

It was intended as a birthday present for a friend to be used
in a small room with small bookshelf speakers.

It is a 4,5 Watt/channel pentode/pentode single ended integrated
which gives a damn on all this "single ended triode without any
negative feedback" madness.

Instead, it is a no-fuss, solidly designed all-pentode
circuit amp, which simply does what it is expected to do.

If you are interested in the circuit development process, you can
find it described extensively in the form of a moderate level
walkthrough, starting at:

http://www.tubes.mynetcologne.de/roe...ematics_e.html

May this walkthrough help other tube DIY amp enthusiasts construct
and enjoy their own DIY amps.

I would like to thank the crowd at
"The G33k Zone" http://geek.scorpiorising.ca/GeeK_ZonE/index.php
who helped a lot in making the schematics section walkthrough
come true.

I wish you and your relatives a great new year!

Tom

Just out of interest, how did you wire the 6V6 as a pentode? It is a
beam tetrode.

d

Pearce Consulting
http://www.pearce.uk.com

Picky! Picky!

Very Pretty!

Cheers, John Stewart

Sorry - should have realised a tiny detail like that wouldn't make any
difference to a tubie! I'm sure it sounds predictably lovely.

d

Pearce Consulting
http://www.pearce.uk.com

John Byrns wrote:

In article , Tom Schlangen
wrote:

Gentlemen,

here is another project I completed (at last...).

http://www.tubes.mynetcologne.de/roe...e/6v6se_e.html

It was intended as a birthday present for a friend to be used
in a small room with small bookshelf speakers.

It is a 4,5 Watt/channel pentode/pentode single ended integrated
which gives a damn on all this "single ended triode without any
negative feedback" madness.

Instead, it is a no-fuss, solidly designed all-pentode
circuit amp, which simply does what it is expected to do.

If you are interested in the circuit development process, you can
find it described extensively in the form of a moderate level
walkthrough, starting at:

http://www.tubes.mynetcologne.de/roe...ematics_e.html

May this walkthrough help other tube DIY amp enthusiasts construct
and enjoy their own DIY amps.

Hi Tom,

That's a great project, and it is good to see someone using pentodes in
place of the obligatory triodes.

I have only one major complaint about the walk through, which is that the
section on the choice of output tube, and its operating point, doesn't
really discuss alternatives to the 6V6 and the chosen operating point. It
gave me the impression that the real reason for the choice of the 6V6 was
because you like the tube and had some in your drawer, nothing wrong that,
or the tube, but it would have been better to either drop the pretense of
a comparison, or provide some discussion of the alternatives.

With regard to the 6V6 operating point, the 250 volt operating point would
have also worked with the given transformer using the 5.2k primary tap.
The inductance argument in favor of the 315 volt operating point is a
false one because the inductance reflected to the secondary remains the
same with either the 5.2k or 8.2k primary tapping.

With regard to other possible octal base tubes, it would appear that the
EL34/6CA7 would also work with the given transformer in either of two
operating modes. The first would be to operate a EL34 in triode mode.
The second would be to use the EL34 in pentode mode with a lower than
normal screen voltage giving a lower current high impedance operating
point suitable for a 8.2k load.

6V6 is only capable of about 40% max efficiency,
so if Pda = 12 watts, then 4.8 watts come out but the OPT soaks up
some power, so 4 watts is all you get, wind permitting on a good day.

But a 6L6 also can be used in triode with Pda = 25 watts,
and efficiency is about 25%, so expect about 6.2 watts, and allowing
for OPT losses, you get 5 watts, which will be a lot better watts than
from
the
6V6 in beam tetrode mode.

EL34 and 6CA7 are also nice in triode.

SEUL is the other option, or CFB; either work well like triode
to reduce odd order like triode locally before some additional loop
FB is used to reduce Ro.
8 watts is easy from EL34 with a low B+.

Even 6L6 in SEUL, or SEcfb works well....

Patrick Turner.




Regards,

John Byrns

Surf my web pages at, http://users.rcn.com/jbyrns/

Hi John,

I have only one major complaint about the walk
through, which is that the section on the choice
of output tube, and its operating point, doesn't
really discuss alternatives to the 6V6 and the
chosen operating point. It gave me the impression
that the real reason for the choice of the 6V6 was
because you like the tube and had some in your drawer,
nothing wrong that, or the tube, but it would have
been better to either drop the pretense of a
comparison, or provide some discussion of the
alternatives.

You are right with this since you must come to this
conclusion because I probably left out (didn't write
it down in the walkthru) an additional "reason": I had
a PT with a 280V secondary I wanted to use, thus it
would make sense to head for a 300-350V B+.

With regard to the 6V6 operating point, the 250 volt
operating point would have also worked with the
given transformer using the 5.2k primary tap.

Sure, but ....

The inductance argument in favor of the 315 volt
operating point is a false one because the inductance
reflected to the secondary remains the same with
either the 5.2k or 8.2k primary tapping.

I think you are mixing up reflected impedance (that
is what you are talking about) and primary inductance,
(that is what I am talking about).

Inductance, other than impedance, is not reflected
in an OPT, it is just a function of winding turns
and core material properties. If you tap a coil,
you tap its inductance. Most winding turns, most
inductance.

With regard to other possible octal base tubes,
it would appear that the EL34/6CA7 would also
work with the given transformer in either of two
operating modes.

Well, this would have resulted in plate currents
dangerously close or above the rated 50mA iddle
current rating of the OPTs, except maybe for a
high B+ operating point (similar to my EL34SET,
see my homepage) of 400V plate voltage. But
yes, I should have mentioned this argument. I
will include it in the walkthru for completeness.

Tnx2u4 those constructive criticism!

Tom

--
All the true gurus I've met never claimed
they were one, and always pointed to someone
better. -- Bill Vermillion

Hi Patrick,

But a 6L6 also can be used in triode with
Pda = 25 watts, and efficiency is about 25%,
so expect about 6.2 watts, and allowing
for OPT losses, you get 5 watts, which will
be a lot better watts than from the 6V6 in
beam tetrode mode.

Sorry, Patrick, I cannot find an operation point
for triode op 6L6 that will crank out 5 Watt Po,
not even 4 or 3 Watt. Have a look at the
spec sheets. 6L6, 807 & the like are extremely
inefficient in triode op.

For tetrode mode, 6L6 would have exceeded the
50mA DC current limit of those tiny OPTs for
usual (means: can be found in spec sheets)
operation points.

For this low to intermediate level walkthrough
the reader (and author) was not expected to find
exotic op points, but just to follow spec sheet
recommendations (suggested op points).

EL34 and 6CA7 are also nice in triode.

I know, I am very fond of my EL34SET :-)

SEUL is the other option, or CFB; either
work well like triode to reduce odd order
like triode locally before some additional
loop FB is used to reduce Ro.

Sure, and indeed I did quite some experiments
with 6V6 UL op, since those multitapped
"experimentation" OPTs just cried for it :-)

But I considered UL op to be beyond the scope
level of that walkthru, not to speak of CFB.

You know, I really wanted to build a simple
amp and write a simple how-to (and, admittedly,
use straight tetrode/pentode mode for a change).

This amp is not state of the art, the walkthru
is not a RDH4 surrogate. But the amp does what
it was intended to do (it reaches and exceeds
the goals that were set) and the walkthrough
will give interested novices a hand to understand
basic tube amp tech.

Tom

--
fnord (now you see it, now you don't)
- R.A. Wilson / FZ

Tom Schlangen wrote:

Hi John,

I have only one major complaint about the walk
through, which is that the section on the choice
of output tube, and its operating point, doesn't
really discuss alternatives to the 6V6 and the
chosen operating point. It gave me the impression
that the real reason for the choice of the 6V6 was
because you like the tube and had some in your drawer,
nothing wrong that, or the tube, but it would have
been better to either drop the pretense of a
comparison, or provide some discussion of the
alternatives.

You are right with this since you must come to this
conclusion because I probably left out (didn't write
it down in the walkthru) an additional "reason": I had
a PT with a 280V secondary I wanted to use, thus it
would make sense to head for a 300-350V B+.

With regard to the 6V6 operating point, the 250 volt
operating point would have also worked with the
given transformer using the 5.2k primary tap.

Sure, but ....

The inductance argument in favor of the 315 volt
operating point is a false one because the inductance
reflected to the secondary remains the same with
either the 5.2k or 8.2k primary tapping.

I think you are mixing up reflected impedance (that
is what you are talking about) and primary inductance,
(that is what I am talking about).

Inductance, other than impedance, is not reflected
in an OPT, it is just a function of winding turns
and core material properties. If you tap a coil,
you tap its inductance. Most winding turns, most
inductance.

With regard to other possible octal base tubes,
it would appear that the EL34/6CA7 would also
work with the given transformer in either of two
operating modes.

Well, this would have resulted in plate currents
dangerously close or above the rated 50mA iddle
current rating of the OPTs, except maybe for a
high B+ operating point (similar to my EL34SET,
see my homepage) of 400V plate voltage. But
yes, I should have mentioned this argument. I
will include it in the walkthru for completeness.

I once bought some OPTs made in 1960 for a kit amp that a guy of 75
had never got around to building.
These were meant for 6GW8, and rated for 50mA per side, being for PP.

I used 6CM5 in triode at 50mA, but used Ea of +375V instead of +270V.

Thge load is about 7k a-a, and I get 25 watts from the amp, class AB1,
and it sounds well.

Its quite OK to have the same Ia, but employ a wider voltage swing in
most OPTs.

The triode power of EL34/6CA7/6L6/KT66 would be better than about the
same amount of
tetrode power of a 6V6.

Patrick Turner.



Tnx2u4 those constructive criticism!

Tom

--
All the true gurus I've met never claimed
they were one, and always pointed to someone
better. -- Bill Vermillion

Tom Schlangen wrote:

Hi Patrick,

But a 6L6 also can be used in triode with
Pda = 25 watts, and efficiency is about 25%,
so expect about 6.2 watts, and allowing
for OPT losses, you get 5 watts, which will
be a lot better watts than from the 6V6 in
beam tetrode mode.


Sorry, Patrick, I cannot find an operation point
for triode op 6L6 that will crank out 5 Watt Po,
not even 4 or 3 Watt. Have a look at the
spec sheets. 6L6, 807 & the like are extremely
inefficient in triode op.

You must use a high value for RL to get the swing and Ea is ideally
+425V.



For tetrode mode, 6L6 would have exceeded the
50mA DC current limit of those tiny OPTs for
usual (means: can be found in spec sheets)
operation points.

Yes, the lower Ea, the lower RL must be and the higher Ia must be.




For this low to intermediate level walkthrough
the reader (and author) was not expected to find
exotic op points, but just to follow spec sheet
recommendations (suggested op points).

EL34 and 6CA7 are also nice in triode.

I know, I am very fond of my EL34SET :-)

SEUL is the other option, or CFB; either
work well like triode to reduce odd order
like triode locally before some additional
loop FB is used to reduce Ro.

Sure, and indeed I did quite some experiments
with 6V6 UL op, since those multitapped
"experimentation" OPTs just cried for it :-)

But I considered UL op to be beyond the scope
level of that walkthru, not to speak of CFB.

You know, I really wanted to build a simple
amp and write a simple how-to (and, admittedly,
use straight tetrode/pentode mode for a change).

Straight SE beam tetrode mode for 6V6 is what was used in
countless radios in the 1940s and 50s.
With poor load matching and lossy OPTs, 2 watts at clipping with 15% thd

was about the performance.

They were never turned up loud, no NFB was used, and it wasn't
meant to be hi-fi. It gave a voice to tell ppl the cricket score from
the mantle peice.
My dear mum played Peter and the Wolf from 78s from an old gram she had
with a 6v6.
So distortion was below 5%.

NFB and flat speakers do give a better result and triode even better
still,
with 2 watts at 1% possible.


This amp is not state of the art, the walkthru
is not a RDH4 surrogate. But the amp does what
it was intended to do (it reaches and exceeds
the goals that were set) and the walkthrough
will give interested novices a hand to understand
basic tube amp tech.

Tom

That's fine. A few beginners would immediately wonder if anything they
first consider could be better
without increasing the parts count a lot.

I was like that.

Patrick Turner.



--
fnord (now you see it, now you don't)
- R.A. Wilson / FZ

Hi Patrick,

Sorry, Patrick, I cannot find an operation point
for triode op 6L6 that will crank out 5 Watt Po,
not even 4 or 3 Watt. [...]

You must use a high value for RL to get the swing
and Ea is ideally +425V.

Come on, Patrick, that would grossly exceed 6L6
screen voltage ratings (and plate voltage ratings
a bit, too). Not a thing one would suggest in a
beginners walkthrough.

I still doubt that anything near 5W Po would be
possible with trioded 6L6, even when exceeding
screen ratings.

Maybe I will set up a quick breadboard hack to
check in real life. 425V you say across the tube?
Cathode bias, I suppose? Let's say Ra = 8-10k?

Tom

--
Knowledge is power - knowledge shared is power lost.
-- A. Crowley

On Wed, 4 Jan 2006 07:21:39 +0100, Tom Schlangen
wrote:

Come on, Patrick, that would grossly exceed 6L6
screen voltage ratings (and plate voltage ratings
a bit, too).

Just a note about G2 ratings; they're based on power
dissipation limits over significant periods of time,
and assume fixed G2 voltages and varying plate voltages,
IOW, the possibility of higher G2 than plate voltage.

Triode and partial-triode use relaxes the stringency
of this otherwise very important limitation.


Also, modern valves are about a lifetime away from
the pre-war specs in the book, for better and for wurst.

Goog fortune,

Chris Hornbeck
"Only necessity is heavy, and only what is heavy has value."
-Milan Kundera, _The Unbearable Lightness of Being_

Hi Patrick,

Trioded 6L6 plate curves according to Sofia tracer,
with loadline Ra = 10k at Ea = 420V, Ik = 60mA,
Pdplate = 26W = 100% w/o considering additional Pdscreen,
Eg1 = -40V, screen voltage rating exceeded by 120V:

http://www.tubes.mynetcologne.de/roehren/misc/6l6t1.gif

Results derived from the loadline above:

http://www.tubes.mynetcologne.de/roehren/misc/6l6t2.gif

Maybe 3 Watt at the secondary, at about 8% H2.

Tom

--
Anyone who considers protocol unimportant has
never dealt with a cat. - R. Heinlein

Tom Schlangen wrote:

Hi Patrick,

Sorry, Patrick, I cannot find an operation point
for triode op 6L6 that will crank out 5 Watt Po,
not even 4 or 3 Watt. [...]

You must use a high value for RL to get the swing
and Ea is ideally +425V.

Come on, Patrick, that would grossly exceed 6L6
screen voltage ratings (and plate voltage ratings
a bit, too). Not a thing one would suggest in a
beginners walkthrough.

Screen voltage ratings for the 6L6GC is 450V, so they can be used
in guitar amps to get a large amount of class AB power.
The old original 6L6 had 300V for screen ratings.

But the g2 voltage ratings are only valid for beam tetrode operation
where Eg2 is a fixed supply.

807 also had identical ratings to the old 6L6.

But where UL or triode operation is used the g2 rating can be increased
because the g2 dissipation becomes lower if the g2 is fed a signal
which is a large % of the anode signal voltage.

Triode operation of even the old 6L6G, or GB allowed Ea = Eg2 = 425 V.

But if in doubt, use 400V.


I still doubt that anything near 5W Po would be
possible with trioded 6L6, even when exceeding
screen ratings.

Total screen and plate dissipation rating is 25 watts,
22 watts for the plate, 2 watts for the g2, ( approx).
If efficiency is 25%, then 6.25 watts is around the max from a 6L6 in
triode.

It was normal for PP class A triode amps with 6L6 in triode to make 12
watts in class A,
and maybe 16 watts class AB just like a pair of KT66 in the williamson
amp.

But 5 watts is definately possible with one 6L6 GC in triode.

Try having Ea = 425V, Ia = 55mA, and as Ra = about 1.6k,
the load should be about 6.25k, and the high Ea and load value
allows a decent negative voltage swing without grid current,
and about equal to the swing up into cut off.
Swing is about +/- 250v pk.

The damping factor is about RL/Ra = 6.25k / 1.6k = about 3.5
allowing for P&S winding resistance which is effectively in series
between
the RL and Ra.







Maybe I will set up a quick breadboard hack to
check in real life. 425V you say across the tube?
Cathode bias, I suppose? Let's say Ra = 8-10k?

Ra is plate resistance, ie, the dynamic resistance looking into the
anode terminal
from the world outside.
RL is the load.

Cathode bias will have Ek about 40v, so the B+ will have to be around
+465V,
so you will need a pair of 350V rated electros for the B+ rail, or 4
with a choke for a CLC filter.
Use resistors across the caps to keep the voltages across the caps
equal.

Aim for total plate and screen dissipation to be about 22 watts, less
than
the rated max amount. 5881 is another good tube to use, its a well rated
6L6.

Then adjust Rk to a value so that Ea across the tube x Ik = 22 watts.

Ik = Ia + Ig2.

If you don't have 6L6 triode curves, use 807 curves; they can be found,
and I bet you get 5 watts in triode class A1 from a 6L6.

A KT88 can give around 8 watts in triode, KT90 about 10 watts.

The Golden Tube Audio amps with 3 x 5881 in parallel SE CFB claimed po =

40 watts, so that's about 13 watts per tube, so since max class A plate
efficiency
in tetrode is about 40%, they dissipate just over 30 watts,
or they are telling fibs about the po and dissipation.
In my 35 watt SE CFB amps with 4 x 6CA7 I am getting nearly 9 watts
in tetrode per tube, with Pda + Pdg2 = about a comfortable 22 watts.
The same quad of tubes would give about 23 watts in triode,
but I'd have to raise the Ea and RL .

Patrick Turner.






Tom

--
Knowledge is power - knowledge shared is power lost.
-- A. Crowley