[Iain Churches]

I have brought this discussion with Joyhn Byrns
over from another thread, as it has the makings
of what might prove to be aninteresting project.



"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:


John wrote

The LF and HF ranges of your proposed +/- 3 dB equalizer are obvious
enough, but it is not so obvious what you are talking about for the MF
range?

Before the days of parametric EQ, many recording consoles had three
band equalisers on most channels. The mid band was often termed
"presence" (particularly on broadcast consoles) and was centred at 3kHz
(the BBC used 2.6kHz IIRC)


The BBC analogue meter is no longer in production, though I do know
a source from which they can probably be obtained NOS.

I did not mean to imply and actual BBC meter should be used, I assumed a
peak reading meter circuit designed specifically for this project, or a
clone of the BBC circuit if desired. I assume that analog meter
movements are still manufactured, or am I wrong about this?

The BBC type is pretty funky. Two movements on one meter face,
green needle pointer for left, red needle pointer for right. White
lettering on a black background. Few people outside broadcast
have seen them. They are always a talking point.

See:
http://www.kolumbus.fi/iain.churches/Pics/BBC_PPM.jpg

What do you mean by the "Peter Baxandall topology"? When I think of a
"Peter Baxandall topology" I always think of his feedback tone control
circuit, but today many people, at least here on this usenet group, seem
to consider the "Baxandall" tone control circuit to be the standard
passive tone control circuit.

It is a long time since I read the Baxandall articles. IIRC the first
circuit was a feedback tone control as you describe. The passive
version arrived soon afterwards. The circuit was later modified for
use with guitar amps in the USA, and known by the name of James.

I would like to see some evidence of who
actually developed the common passive tone control circuit, it is not
obvious to me that it was "Peter Baxandall" was responsible for it as
many today claim, although it is possible, I don't know and would like
to see some evidence to settle the issue once and for all.

Peter Baxandall was the author of the articles which AFAIK first
described this tone control in a British journal. All the textbooks I
have seen attribute it to him also.

Unfortunately I don't think the passive topology, whoever may have
designed it, easily accommodates the addition of a "MF" band.

Agreed. I was thinking of Baxandall for a two frequency
control LF and HF ( I would probably never use the mid control)
but if one needs mid, then there are plenty of other options.


I have been giving this idea quite a bit of thought. There are a lot of
alternatives, but I have picked one as a starting point, although it is
difficult to proceed very far without having a better idea what you want
the "MF" equalizer to do? Could you provide some input on the
specifications desired for the "MF" equalizer? Once I have had a chance
to think a bit about the requirements for the "MF" equalizer, I will
write up my thoughts and post them here.

As mentiond before, I think it should be fairy wide Q and centred on
3kHz Personally, I could live without it.

Let me do some listening tests with a parametric set up as a three band
(I have some Neve modules) and I will see if I can find a compromise.
I am sure there is no "one size fits all" solution.

Best regards
Iain

[Patrick Turner]

Iain Churches wrote:

I have brought this discussion with Joyhn Byrns
over from another thread, as it has the makings
of what might prove to be aninteresting project.

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:


John wrote

The LF and HF ranges of your proposed +/- 3 dB equalizer are obvious
enough, but it is not so obvious what you are talking about for the MF
range?

Before the days of parametric EQ, many recording consoles had three
band equalisers on most channels. The mid band was often termed
"presence" (particularly on broadcast consoles) and was centred at 3kHz
(the BBC used 2.6kHz IIRC)

The BBC analogue meter is no longer in production, though I do know
a source from which they can probably be obtained NOS.

I did not mean to imply and actual BBC meter should be used, I assumed a
peak reading meter circuit designed specifically for this project, or a
clone of the BBC circuit if desired. I assume that analog meter
movements are still manufactured, or am I wrong about this?

The BBC type is pretty funky. Two movements on one meter face,
green needle pointer for left, red needle pointer for right. White
lettering on a black background. Few people outside broadcast
have seen them. They are always a talking point.

See:
http://www.kolumbus.fi/iain.churches/Pics/BBC_PPM.jpg

What do you mean by the "Peter Baxandall topology"? When I think of a
"Peter Baxandall topology" I always think of his feedback tone control
circuit, but today many people, at least here on this usenet group, seem
to consider the "Baxandall" tone control circuit to be the standard
passive tone control circuit.

It is a long time since I read the Baxandall articles. IIRC the first
circuit was a feedback tone control as you describe. The passive
version arrived soon afterwards. The circuit was later modified for
use with guitar amps in the USA, and known by the name of James.

I would like to see some evidence of who
actually developed the common passive tone control circuit, it is not
obvious to me that it was "Peter Baxandall" was responsible for it as
many today claim, although it is possible, I don't know and would like
to see some evidence to settle the issue once and for all.

Peter Baxandall was the author of the articles which AFAIK first
described this tone control in a British journal. All the textbooks I
have seen attribute it to him also.

Unfortunately I don't think the passive topology, whoever may have
designed it, easily accommodates the addition of a "MF" band.

Agreed. I was thinking of Baxandall for a two frequency
control LF and HF ( I would probably never use the mid control)
but if one needs mid, then there are plenty of other options.


I have been giving this idea quite a bit of thought. There are a lot of
alternatives, but I have picked one as a starting point, although it is
difficult to proceed very far without having a better idea what you want
the "MF" equalizer to do? Could you provide some input on the
specifications desired for the "MF" equalizer? Once I have had a chance
to think a bit about the requirements for the "MF" equalizer, I will
write up my thoughts and post them here.

As mentiond before, I think it should be fairy wide Q and centred on
3kHz Personally, I could live without it.

Let me do some listening tests with a parametric set up as a three band
(I have some Neve modules) and I will see if I can find a compromise.
I am sure there is no "one size fits all" solution.

Best regards
Iain

I use the baxandal network in a FB circuit around a µ follower stage,

See Sheet 3, V4A,V4B, lhs about 60% down the page at

http://www.turneraudio.com.au/preamp...ated-2006.html

Its all anyone needs for hi-fi tone controls.

Patrick Turner

[John Byrns]

In article ,
"Iain Churches" wrote:

I have brought this discussion with Joyhn Byrns
over from another thread, as it has the makings
of what might prove to be aninteresting project.

Or not, I held off on replying to see if anyone else jumped in to
express interest in the project, Patrick was the only one to comment.

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

The LF and HF ranges of your proposed +/- 3 dB equalizer are obvious
enough, but it is not so obvious what you are talking about for the MF
range?

Before the days of parametric EQ, many recording consoles had three
band equalisers on most channels. The mid band was often termed
"presence" (particularly on broadcast consoles) and was centred at 3kHz
(the BBC used 2.6kHz IIRC)

I have taken the time to start thinking about three different design
approaches for this equalizer. The first approach, and probably the
simplest is to use the Baxandall feedback tone control topology that
Patrick suggested. This seems like the simplest approach because it
doesn't require a gain makeup stage like the passive approach does. The
problem with the Baxandall feedback approach is that adding an MF
equalizer seems a bit of a kludge to me.

A better feedback approach, which more easily accommodates an MF
equalizer would be to use a differential amplifier as the feedback
stage. This is the basis of my magnum opus design which also uses a
gyrator to create a virtual inductor for the MF equalizer. Nine triodes
are required for each channel with this design, 2 for an ALCF input
buffer, 2 for the gyrator, 3 for the differential amplifier feedback
equalizer stage, and 2 for an ALCF output buffer.

The third approach, which is my favorite, is a passive network with a
gain makeup stage, although I am not sure how to build a gain makeup
stage with such low gain. My approach, which I have yet to simulate to
see if it can meet the MF equalizer requirements, would use a normal RC
LF equalizer and two cascaded RC HF equalizers whose effects start at
different frequencies. The way this would work for MF equalization
would be as follows. One HF equalizer would begin its boost/cut at say
1 kHz, and the second would become effective at say 7 kHz. The precise
operating frequencies have yet to be determined. A MF bump around the
presence region could be created by setting the 1 kHz equalizer toggle
to its boost position, and setting the 7 kHz equalizer to its cut
position. An MF dip would be created with the combination of a 1kHz cut
and 7 kHz boost. I see two problems with this approach. First the MF
region affected is going to be quite wide. Second since each of the
individual equalizers is designed for an ultimate boost/cut of 3 dB, the
combined effect at MF of the two equalizers isn't going to reach a full
3 dB due to the overlap of their curves. To fix this problem so that
the full 3 dB boost/cut is available at MF, I propose linking the two HF
toggles in such a way that when they are operated to opposite positions
the ultimate boost/cut provided by each is increased to more than 3 dB
so that the resultant effect at MF is the required 3 dB. Unfortunately
there is a possibility that this would require a contact configuration
on the toggle switches that isn't easily available. An added feature of
this design is that an ultimate HF boost/cut of 6 dB becomes available
by activating both HF switches in the same direction.

I will try and do some calculations in the next couple of days to see if
this approach is workable.

What do you mean by the "Peter Baxandall topology"? When I think of a
"Peter Baxandall topology" I always think of his feedback tone control
circuit, but today many people, at least here on this usenet group, seem
to consider the "Baxandall" tone control circuit to be the standard
passive tone control circuit.

It is a long time since I read the Baxandall articles. IIRC the first
circuit was a feedback tone control as you describe. The passive
version arrived soon afterwards. The circuit was later modified for
use with guitar amps in the USA, and known by the name of James.

I have an old Wireless World article by P.J. Baxandall which describes
his feedback tone control, I don't know if this was his original
disclosure of the circuit or not. I don't have any article by Baxandall
that describes the passive approach, if anyone has an early article by
Baxandall on the passive tone control circuit I would be interested in a
copy. I also have an article by James describing the typical passive
tone control circuit as used in Hi-Fi, I don't remember where this
article was published, it may also have been Wireless World. I assume
that the original designer of the standard passive Hi-Fi tone control
network was either James or an anonymous unknown, not Baxandall,
although I am open to being convinced otherwise if there is any real
evidence available, for example an article by Baxandall where he
actually asserts a claim that he was the original designer, or an
article by Baxandall that predates any known use of the circuit in Hi-Fi
sets. The standard passive Hi-Fi tone control network seems to have
appeared some time in the early 1950s, it does not appear to be
discussed in the 1953 edition of the famous RDH4th, although it does
appear in the 1954 edition of the RCA Receiving Tube Manual. I used to
assume that the typical passive Hi-Fi tone control circuit dated back to
the beginning of time and was surprised when I looked for early examples
and couldn't find any.

The "tone stack" used in guitar amps seems to be a quite different
design than the standard passive Hi-Fi tone control circuit.

I would like to see some evidence of who
actually developed the common passive tone control circuit, it is not
obvious to me that it was "Peter Baxandall" was responsible for it as
many today claim, although it is possible, I don't know and would like
to see some evidence to settle the issue once and for all.

Peter Baxandall was the author of the articles which AFAIK first
described this tone control in a British journal. All the textbooks I
have seen attribute it to him also.

I would be interested in seeing those articles and textbook references.
Baxandall's name has always been associated with the feedback tone
control circuit in articles and textbooks, but I never saw the passive
circuit attributed to him until audio groups appeared on the internet.
It just has too much of the feel of an Urban Legend to me without some
serious evidence to the contrary. Do you know what issue of Wireless
World Baxandall's article describing the standard passive tone control
circuit appeared in? I have a fair collection of Wireless World from
the relevant period and might be able to find it.

I have been giving this idea quite a bit of thought. There are a lot of
alternatives, but I have picked one as a starting point, although it is
difficult to proceed very far without having a better idea what you want
the "MF" equalizer to do? Could you provide some input on the
specifications desired for the "MF" equalizer? Once I have had a chance
to think a bit about the requirements for the "MF" equalizer, I will
write up my thoughts and post them here.

As mentiond before, I think it should be fairy wide Q and centred on
3kHz Personally, I could live without it.

Broad makes it easier, without an MF range of some sort the design is
trivial

Let me do some listening tests with a parametric set up as a three band
(I have some Neve modules) and I will see if I can find a compromise.
I am sure there is no "one size fits all" solution.

Of course not, but with a limit of only 3, three position toggle
switches one must force a single size to fit all, even if some pushing
and shoving is required.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Patrick Turner]

John Byrns wrote:

In article ,
"Iain Churches" wrote:

I have brought this discussion with Joyhn Byrns
over from another thread, as it has the makings
of what might prove to be aninteresting project.

Or not, I held off on replying to see if anyone else jumped in to
express interest in the project, Patrick was the only one to comment.

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

The LF and HF ranges of your proposed +/- 3 dB equalizer are obvious
enough, but it is not so obvious what you are talking about for the MF
range?

Before the days of parametric EQ, many recording consoles had three
band equalisers on most channels. The mid band was often termed
"presence" (particularly on broadcast consoles) and was centred at 3kHz
(the BBC used 2.6kHz IIRC)

I have taken the time to start thinking about three different design
approaches for this equalizer. The first approach, and probably the
simplest is to use the Baxandall feedback tone control topology that
Patrick suggested. This seems like the simplest approach because it
doesn't require a gain makeup stage like the passive approach does. The
problem with the Baxandall feedback approach is that adding an MF
equalizer seems a bit of a kludge to me.

If you want midrange boost, just turn down both bass and treble,
and then turn up the gain. You have midrange boost.

But the problem with most tone controls even with Baxandal style FB
networks
is that when adjusted to full cut or boost, there is just a pole at
about say 2kHz
and beyond that the F are all cut or boosted at at 6dB per octave slope.

The ideal way for hi-fi ppl to adjust the tone of their audio is to have
shelving
networks so that the greatest cut or boost
possible is say 6dB, which will halve or double the loudness of the
F involved, and so when you turn down the treble,
there are two poles, one at say 1k, and then one at 2k, which is 6dB /
octave.
You can draw the line of the response which remains about level
to 300Hz, then sways down 3dB at about 1.4kHz, then ends up going level
beyond 3kHz. This shape to the cut profile means that you don't loose
detail,
but you change the tone, ie the balance between what is below 1kHz to
what is above1kHz.
if you apply the same idea to bass cut/boost, you get a nicer effect.

I have never needed to have a midrange cut/boost.

The only time the tone gets adjusted a lot is on the kitchen am radio
because of much variable
quality, and its ability for 10kHz of audio bw.

I rarely ever use tone adjustments of the main hi-fi system, and nor
does anyone else,
so you didn't get too many replys to your post.
Its become both fashionable and normal for all high end gear
to NOT have any tone controls.
Good recordings have it all done well for you.



A better feedback approach, which more easily accommodates an MF
equalizer would be to use a differential amplifier as the feedback
stage. This is the basis of my magnum opus design which also uses a
gyrator to create a virtual inductor for the MF equalizer. Nine triodes
are required for each channel with this design, 2 for an ALCF input
buffer, 2 for the gyrator, 3 for the differential amplifier feedback
equalizer stage, and 2 for an ALCF output buffer.

What exactly what to you want to use this all for?



The third approach, which is my favorite, is a passive network with a
gain makeup stage, although I am not sure how to build a gain makeup
stage with such low gain.

Passive tone controls are very hard to get right, ie, get the desired
log pots to track correctly and have more than one channel equal.
If you start with a volt, you must amplify it to say 8V
then when set level the Baxandal passive produces a volt,
but you have the distortions of the amplifier all present.

YUK!!!!

Gain is typically via one half of a 12AU7.

So lets start again with a volt....

Use the same 12AU7, but this time there is a baxandal shunt FB network
using linear pots, and same value R&C either side of the pots, and
first tine that you set it up you will wonder why you ever bothered with
a gain stage
followed by a passive TC network.
The FB TC stage gives say 0.93V out at low Z.

The distortion of the tube is reduced by the shunt NFB,
and I don't know anyone who can tell me when i have my
tone stages switched in or out when in the flat position.
In fact the maximum V the tube has to make is the 0.93V out,
so THD is negligible without FB and when
FB is used the THD is extremely low.
The only trouble is that the FB network is a lower Rin than a passive
set up.
But Rout is less than 2k, due to FB.
so I make sure when the TC stage is switched in, its driven by something
with
low Rout, such as the CD player, or the phono amp output.
There isn't anything these days which is high Rout, only old crap which
has high Rout
where bean counter's said no to a CF on the output.




My approach, which I have yet to simulate to
see if it can meet the MF equalizer requirements, would use a normal RC
LF equalizer and two cascaded RC HF equalizers whose effects start at
different frequencies. The way this would work for MF equalization
would be as follows. One HF equalizer would begin its boost/cut at say
1 kHz, and the second would become effective at say 7 kHz. The precise
operating frequencies have yet to be determined. A MF bump around the
presence region could be created by setting the 1 kHz equalizer toggle
to its boost position, and setting the 7 kHz equalizer to its cut
position. An MF dip would be created with the combination of a 1kHz cut
and 7 kHz boost. I see two problems with this approach. First the MF
region affected is going to be quite wide. Second since each of the
individual equalizers is designed for an ultimate boost/cut of 3 dB, the
combined effect at MF of the two equalizers isn't going to reach a full
3 dB due to the overlap of their curves. To fix this problem so that
the full 3 dB boost/cut is available at MF, I propose linking the two HF
toggles in such a way that when they are operated to opposite positions
the ultimate boost/cut provided by each is increased to more than 3 dB
so that the resultant effect at MF is the required 3 dB. Unfortunately
there is a possibility that this would require a contact configuration
on the toggle switches that isn't easily available. An added feature of
this design is that an ultimate HF boost/cut of 6 dB becomes available
by activating both HF switches in the same direction.

I will try and do some calculations in the next couple of days to see if
this approach is workable.

Good luck with the endless possibilities.

Patrick Turner.

What do you mean by the "Peter Baxandall topology"? When I think of a
"Peter Baxandall topology" I always think of his feedback tone control
circuit, but today many people, at least here on this usenet group, seem
to consider the "Baxandall" tone control circuit to be the standard
passive tone control circuit.

It is a long time since I read the Baxandall articles. IIRC the first
circuit was a feedback tone control as you describe. The passive
version arrived soon afterwards. The circuit was later modified for
use with guitar amps in the USA, and known by the name of James.

I have an old Wireless World article by P.J. Baxandall which describes
his feedback tone control, I don't know if this was his original
disclosure of the circuit or not. I don't have any article by Baxandall
that describes the passive approach, if anyone has an early article by
Baxandall on the passive tone control circuit I would be interested in a
copy. I also have an article by James describing the typical passive
tone control circuit as used in Hi-Fi, I don't remember where this
article was published, it may also have been Wireless World. I assume
that the original designer of the standard passive Hi-Fi tone control
network was either James or an anonymous unknown, not Baxandall,
although I am open to being convinced otherwise if there is any real
evidence available, for example an article by Baxandall where he
actually asserts a claim that he was the original designer, or an
article by Baxandall that predates any known use of the circuit in Hi-Fi
sets. The standard passive Hi-Fi tone control network seems to have
appeared some time in the early 1950s, it does not appear to be
discussed in the 1953 edition of the famous RDH4th, although it does
appear in the 1954 edition of the RCA Receiving Tube Manual. I used to
assume that the typical passive Hi-Fi tone control circuit dated back to
the beginning of time and was surprised when I looked for early examples
and couldn't find any.

The "tone stack" used in guitar amps seems to be a quite different
design than the standard passive Hi-Fi tone control circuit.

I would like to see some evidence of who
actually developed the common passive tone control circuit, it is not
obvious to me that it was "Peter Baxandall" was responsible for it as
many today claim, although it is possible, I don't know and would like
to see some evidence to settle the issue once and for all.

Peter Baxandall was the author of the articles which AFAIK first
described this tone control in a British journal. All the textbooks I
have seen attribute it to him also.

I would be interested in seeing those articles and textbook references.
Baxandall's name has always been associated with the feedback tone
control circuit in articles and textbooks, but I never saw the passive
circuit attributed to him until audio groups appeared on the internet.
It just has too much of the feel of an Urban Legend to me without some
serious evidence to the contrary. Do you know what issue of Wireless
World Baxandall's article describing the standard passive tone control
circuit appeared in? I have a fair collection of Wireless World from
the relevant period and might be able to find it.

I have been giving this idea quite a bit of thought. There are a lot of
alternatives, but I have picked one as a starting point, although it is
difficult to proceed very far without having a better idea what you want
the "MF" equalizer to do? Could you provide some input on the
specifications desired for the "MF" equalizer? Once I have had a chance
to think a bit about the requirements for the "MF" equalizer, I will
write up my thoughts and post them here.

As mentiond before, I think it should be fairy wide Q and centred on
3kHz Personally, I could live without it.

Broad makes it easier, without an MF range of some sort the design is
trivial

Let me do some listening tests with a parametric set up as a three band
(I have some Neve modules) and I will see if I can find a compromise.
I am sure there is no "one size fits all" solution.

Of course not, but with a limit of only 3, three position toggle
switches one must force a single size to fit all, even if some pushing
and shoving is required.

Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns]

In article ,
Patrick Turner wrote:

John Byrns wrote:

I have taken the time to start thinking about three different design
approaches for this equalizer. The first approach, and probably the
simplest is to use the Baxandall feedback tone control topology that
Patrick suggested. This seems like the simplest approach because it
doesn't require a gain makeup stage like the passive approach does. The
problem with the Baxandall feedback approach is that adding an MF
equalizer seems a bit of a kludge to me.

If you want midrange boost, just turn down both bass and treble,
and then turn up the gain. You have midrange boost.

I thought of that, its obvious, but it is too simplistic and doesn't
work if you want the MF band to be narrower than the distance between
the LF and HF bands.

But the problem with most tone controls even with Baxandal style FB
networks
is that when adjusted to full cut or boost, there is just a pole at
about say 2kHz
and beyond that the F are all cut or boosted at at 6dB per octave slope.

Not true, if you remember, Iain's spec. called for a maximum boost and
cut of 3 dB total, controlled by three position toggle switches
providing -3 dB, 0 dB, and +3 dB at LF, MF, and HF. The 6 dB per octave
slope doesn't get a chance to get beyond 3 dB.

The ideal way for hi-fi ppl to adjust the tone of their audio is to have
shelving
networks so that the greatest cut or boost
possible is say 6dB, which will halve or double the loudness of the
F involved, and so when you turn down the treble,
there are two poles, one at say 1k, and then one at 2k, which is 6dB /
octave.

Actually I think you have got that wrong, there are not two poles in a
shelving network, there is one pole and one zero IIRC. Actually the LF
and HF networks I was proposing are shelving networks with the pole and
zero closely spaced to provide 3 dB shelves.

You can draw the line of the response which remains about level
to 300Hz, then sways down 3dB at about 1.4kHz, then ends up going level
beyond 3kHz. This shape to the cut profile means that you don't loose
detail,
but you change the tone, ie the balance between what is below 1kHz to
what is above1kHz.
if you apply the same idea to bass cut/boost, you get a nicer effect.

You have correctly grasped the idea, that is exactly the response the LF
and HF networks I proposed have, except the shelf is limited to 3 dB.

I have never needed to have a midrange cut/boost.

The MF control can be used to produce some interesting effects if the MF
band is not made too wide as in your proposal above.

The only time the tone gets adjusted a lot is on the kitchen am radio
because of much variable
quality, and its ability for 10kHz of audio bw.

I rarely ever use tone adjustments of the main hi-fi system, and nor
does anyone else,

That's not true, I for one often like to twiddle the 5 band tone
controls on my preamp to suit my mood. Surely when visiting friends or
relatives, or riding in their vehicles, you have noticed how they
usually have their graphic equalizers set to the infamous "smile" curve.
Even years ago long before automobile radios had graphic equalizers, my
Father would turn the single knob tone control fully counter clockwise
which boosted the bass and cut the treble. When I would ride with my
Mother I would turn the knob fully clockwise which provided electrically
flat response, my Father would always complain about this the next time
he drove the car.

so you didn't get too many replys to your post.

My post was the result of a comment I made about a matching equalizer in
a response to Iain's original preamp post. I didn't expect a positive
response from Iain, and was surprised at his marginally positive
response, although I did considered it might have been a joke on Iain's
part. Since you have been the only one besides Iain to respond, I
should probably drop the idea.

I would however still like to locate a source for three position toggle
switches with nonstandard switching configurations.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Patrick Turner]

John Byrns wrote:

In article ,
Patrick Turner wrote:

John Byrns wrote:

I have taken the time to start thinking about three different design
approaches for this equalizer. The first approach, and probably the
simplest is to use the Baxandall feedback tone control topology that
Patrick suggested. This seems like the simplest approach because it
doesn't require a gain makeup stage like the passive approach does. The
problem with the Baxandall feedback approach is that adding an MF
equalizer seems a bit of a kludge to me.

If you want midrange boost, just turn down both bass and treble,
and then turn up the gain. You have midrange boost.

I thought of that, its obvious, but it is too simplistic and doesn't
work if you want the MF band to be narrower than the distance between
the LF and HF bands.

But the problem with most tone controls even with Baxandal style FB
networks
is that when adjusted to full cut or boost, there is just a pole at
about say 2kHz
and beyond that the F are all cut or boosted at at 6dB per octave slope.

Not true, if you remember, Iain's spec. called for a maximum boost and
cut of 3 dB total, controlled by three position toggle switches
providing -3 dB, 0 dB, and +3 dB at LF, MF, and HF. The 6 dB per octave
slope doesn't get a chance to get beyond 3 dB.

The ideal way for hi-fi ppl to adjust the tone of their audio is to have
shelving
networks so that the greatest cut or boost
possible is say 6dB, which will halve or double the loudness of the
F involved, and so when you turn down the treble,
there are two poles, one at say 1k, and then one at 2k, which is 6dB /
octave.

Actually I think you have got that wrong, there are not two poles in a
shelving network, there is one pole and one zero IIRC. Actually the LF
and HF networks I was proposing are shelving networks with the pole and
zero closely spaced to provide 3 dB shelves.

Lemme just describe what i meant.

Say you want to shelve F above 2k to take more edge of a harsh digital
recording.
Or you have a bright speaker.

Then you can design an RC network with two poles, and start with
horizontal line
from LF to 500Hz, then draw the slope down to HF graph side at 6dB per
octave,
until say -6dB is achieved, which is at 1kHz, then continue horizontally
to the HF.

This line won't be the resoense, F begins to visibly sag at say 300Hz,
then
its about -3 at 700Hz, then then is levels out with a curve. At thew
"poles"
there actually isn't a full 3dB sag. Its an easy swayed curved line
to get the shape of the shelf.

You should under stand about drawing where the poles are and drawing
rates of attenuration, then filling the straight lines with curces. RC
filters never have an abrupt
angular response curve.


You can draw the line of the response which remains about level
to 300Hz, then sways down 3dB at about 1.4kHz, then ends up going level
beyond 3kHz. This shape to the cut profile means that you don't loose
detail,
but you change the tone, ie the balance between what is below 1kHz to
what is above1kHz.
if you apply the same idea to bass cut/boost, you get a nicer effect.

You have correctly grasped the idea, that is exactly the response the LF
and HF networks I proposed have, except the shelf is limited to 3 dB.

3dB is very little, I like to have minimum 6dB, max 8 dB

I have never needed to have a midrange cut/boost.

The MF control can be used to produce some interesting effects if the MF
band is not made too wide as in your proposal above.

I just have bass/treble cut & boost and have never bothered with
anything else.

The only time the tone gets adjusted a lot is on the kitchen am radio
because of much variable
quality, and its ability for 10kHz of audio bw.

I rarely ever use tone adjustments of the main hi-fi system, and nor
does anyone else,

That's not true, I for one often like to twiddle the 5 band tone
controls on my preamp to suit my mood. Surely when visiting friends or
relatives, or riding in their vehicles, you have noticed how they
usually have their graphic equalizers set to the infamous "smile" curve.

If the system has no bass and smothers the HF, you know why.


Even years ago long before automobile radios had graphic equalizers, my
Father would turn the single knob tone control fully counter clockwise
which boosted the bass and cut the treble. When I would ride with my
Mother I would turn the knob fully clockwise which provided electrically
flat response, my Father would always complain about this the next time
he drove the car.

People are different.

so you didn't get too many replys to your post.

My post was the result of a comment I made about a matching equalizer in
a response to Iain's original preamp post. I didn't expect a positive
response from Iain, and was surprised at his marginally positive
response, although I did considered it might have been a joke on Iain's
part. Since you have been the only one besides Iain to respond, I
should probably drop the idea.

I would however still like to locate a source for three position toggle
switches with nonstandard switching configurations.

Good luck finding good switches...

Patrick Turner.

Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns]

In article ,
Patrick Turner wrote:

John Byrns wrote:

In article ,
Patrick Turner wrote:

John Byrns wrote:

I have taken the time to start thinking about three different design
approaches for this equalizer. The first approach, and probably the
simplest is to use the Baxandall feedback tone control topology that
Patrick suggested. This seems like the simplest approach because it
doesn't require a gain makeup stage like the passive approach does. The
problem with the Baxandall feedback approach is that adding an MF
equalizer seems a bit of a kludge to me.

If you want midrange boost, just turn down both bass and treble,
and then turn up the gain. You have midrange boost.

I thought of that, its obvious, but it is too simplistic and doesn't
work if you want the MF band to be narrower than the distance between
the LF and HF bands.

But the problem with most tone controls even with Baxandal style FB
networks
is that when adjusted to full cut or boost, there is just a pole at
about say 2kHz
and beyond that the F are all cut or boosted at at 6dB per octave slope.

Not true, if you remember, Iain's spec. called for a maximum boost and
cut of 3 dB total, controlled by three position toggle switches
providing -3 dB, 0 dB, and +3 dB at LF, MF, and HF. The 6 dB per octave
slope doesn't get a chance to get beyond 3 dB.

The ideal way for hi-fi ppl to adjust the tone of their audio is to have
shelving
networks so that the greatest cut or boost
possible is say 6dB, which will halve or double the loudness of the
F involved, and so when you turn down the treble,
there are two poles, one at say 1k, and then one at 2k, which is 6dB /
octave.

Actually I think you have got that wrong, there are not two poles in a
shelving network, there is one pole and one zero IIRC. Actually the LF
and HF networks I was proposing are shelving networks with the pole and
zero closely spaced to provide 3 dB shelves.

Lemme just describe what i meant.

You already did that in your previous post, and I understood what you
meant the first time around.

Say you want to shelve F above 2k to take more edge of a harsh digital
recording.
Or you have a bright speaker.

Then you can design an RC network with two poles,

This is the part where you are wrong, an RC network with the response
you have described doesn't have two poles, it has one pole and one zero,
that is my point.

and start with
horizontal line
from LF to 500Hz, then draw the slope down to HF graph side at 6dB per
octave,
until say -6dB is achieved, which is at 1kHz, then continue horizontally
to the HF.

This line won't be the resoense, F begins to visibly sag at say 300Hz,
then
its about -3 at 700Hz, then then is levels out with a curve. At thew
"poles"
there actually isn't a full 3dB sag. Its an easy swayed curved line
to get the shape of the shelf.

You should under stand about drawing where the poles are and drawing
rates of attenuration, then filling the straight lines with curces. RC
filters never have an abrupt
angular response curve.

The thing to understand about drawing this response curve is that there
is one pole and one zero, not two poles, where is Henry Pasternack when
we need him?

You can draw the line of the response which remains about level
to 300Hz, then sways down 3dB at about 1.4kHz, then ends up going level
beyond 3kHz. This shape to the cut profile means that you don't loose
detail,
but you change the tone, ie the balance between what is below 1kHz to
what is above1kHz.
if you apply the same idea to bass cut/boost, you get a nicer effect.

You have correctly grasped the idea, that is exactly the response the LF
and HF networks I proposed have, except the shelf is limited to 3 dB.

3dB is very little, I like to have minimum 6dB, max 8 dB

I agree with you on this, I suggested a seven position switch with
positions for -6 dB, -4 dB, -2 dB, 0 dB, +2 dB, +4 dB, and +6 dB, but
Iain said 6 dB was too much.

I have never needed to have a midrange cut/boost.

Perhaps you were only trying to compensate for a speaker with weak bass
or treble, then you might not have felt the need for a midrange
equalizer. If you were trying equalize a recording so that it was more
in line with your personal taste, then you might have found use for a
midrange equalizer. My personal preference is for a semi parametric
midrange equalizer where both the center frequency and the amount of
boost/cut are adjustable.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Patrick Turner]

Lemme just describe what i meant.

You already did that in your previous post, and I understood what you
meant the first time around.

Say you want to shelve F above 2k to take more edge of a harsh digital
recording.
Or you have a bright speaker.

Then you can design an RC network with two poles,

This is the part where you are wrong, an RC network with the response
you have described doesn't have two poles, it has one pole and one zero,
that is my point.

I see two poles, you see one. OK, but
you undertsand the shelving apprach.



and start with
horizontal line
from LF to 500Hz, then draw the slope down to HF graph side at 6dB per
octave,
until say -6dB is achieved, which is at 1kHz, then continue horizontally
to the HF.

This line won't be the resoense, F begins to visibly sag at say 300Hz,
then
its about -3 at 700Hz, then then is levels out with a curve. At thew
"poles"
there actually isn't a full 3dB sag. Its an easy swayed curved line
to get the shape of the shelf.

You should under stand about drawing where the poles are and drawing
rates of attenuration, then filling the straight lines with curces. RC
filters never have an abrupt
angular response curve.

The thing to understand about drawing this response curve is that there
is one pole and one zero, not two poles, where is Henry Pasternack when
we need him?

Does anyone need Henry? I thought they he had trouble being wanted here
let alone needed.

Anyway, the extra series R in my Baxandal derived tone control networks
make the TCN a little easier on the ears IMHO.

You can draw the line of the response which remains about level
to 300Hz, then sways down 3dB at about 1.4kHz, then ends up going level
beyond 3kHz. This shape to the cut profile means that you don't loose
detail,
but you change the tone, ie the balance between what is below 1kHz to
what is above1kHz.
if you apply the same idea to bass cut/boost, you get a nicer effect.

You have correctly grasped the idea, that is exactly the response the LF
and HF networks I proposed have, except the shelf is limited to 3 dB.

3dB is very little, I like to have minimum 6dB, max 8 dB

I agree with you on this, I suggested a seven position switch with
positions for -6 dB, -4 dB, -2 dB, 0 dB, +2 dB, +4 dB, and +6 dB, but
Iain said 6 dB was too much.

Switching is OK.


I have never needed to have a midrange cut/boost.

Perhaps you were only trying to compensate for a speaker with weak bass
or treble, then you might not have felt the need for a midrange
equalizer. If you were trying equalize a recording so that it was more
in line with your personal taste, then you might have found use for a
midrange equalizer. My personal preference is for a semi parametric
midrange equalizer where both the center frequency and the amount of
boost/cut are adjustable.

I have not wanted to make much else than what I have.
I've never felt a need for it.

Patrick Turner.

Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Iain Churches]

"John Byrns" wrote in message
...

My post was the result of a comment I made about a matching equalizer in
a response to Iain's original preamp post. I didn't expect a positive
response from Iain, and was surprised at his marginally positive
response, although I did considered it might have been a joke on Iain's
part. Since you have been the only one besides Iain to respond, I
should probably drop the idea.

I was positive enough to think your ideas were worthy of a new
thread, which I duly started. Didn't you notice it, John?


Best regards

[John Byrns]

In article ,
"Iain Churches" wrote:

"John Byrns" wrote in message
...

My post was the result of a comment I made about a matching equalizer in
a response to Iain's original preamp post. I didn't expect a positive
response from Iain, and was surprised at his marginally positive
response, although I did considered it might have been a joke on Iain's
part. Since you have been the only one besides Iain to respond, I
should probably drop the idea.

I was positive enough to think your ideas were worthy of a new
thread, which I duly started. Didn't you notice it, John?

Yes, I did notice your interest, but there is no missing Patrick's
point, the mention of equalizers in this group always draws intense
silence. I suspect people believe they will be somehow tainted by even
discussing this forbidden item, much less actually using one in their
system.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Sander deWaal]

John Byrns said:


Yes, I did notice your interest, but there is no missing Patrick's
point, the mention of equalizers in this group always draws intense
silence. I suspect people believe they will be somehow tainted by even
discussing this forbidden item, much less actually using one in their
system.


Huh? We all use equalisers, in the form of RIAA networks, crossovers,
tone controls or even tube amplifiers.

I just don't see the point in designing an eq with tubes...........

--

- Maggies are an addiction for life. -

[John Byrns]

In article ,
Patrick Turner wrote:


Does anyone need Henry? I thought they he had trouble being wanted here
let alone needed.

Henry had a good University education, knew his theory well, and he
could explain it clearly to others, except when he choose to give it
some extra spin in order to advance his agenda.

Anyway, the extra series R in my Baxandal derived tone control networks
make the TCN a little easier on the ears IMHO.

Which extra series R are you talking about, the 4k7, 11k, or another one
entirely?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Patrick Turner]

John Byrns wrote:

In article ,
Patrick Turner wrote:


Does anyone need Henry? I thought they he had trouble being wanted here
let alone needed.

Henry had a good University education, knew his theory well, and he
could explain it clearly to others, except when he choose to give it
some extra spin in order to advance his agenda.

Anyway, the extra series R in my Baxandal derived tone control networks
make the TCN a little easier on the ears IMHO.

Which extra series R are you talking about, the 4k7, 11k, or another one
entirely?

John, go to

http://www.turneraudio.com.au/preamp...ated-2006.html

Then scroll down 60% to sheet 3, which has a gain stage and tone control
stage schematic.
See R7, R8, R9, R10.

Maybe someone may like to simulate the performance in Spice or whatever.

Patrick Turner.



Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns]

In article ,
Patrick Turner wrote:

John Byrns wrote:

In article ,
Patrick Turner wrote:

Anyway, the extra series R in my Baxandal derived tone control networks
make the TCN a little easier on the ears IMHO.

Which extra series R are you talking about, the 4k7, 11k, or another one
entirely?

John, go to

http://www.turneraudio.com.au/preamp...ated-2006.html

Then scroll down 60% to sheet 3, which has a gain stage and tone control
stage schematic.
See R7, R8, R9, R10.

Patrick, R7 & R9 in the schematic of your tone control stage are simply
the main shunt feedback resistors and as such are nothing new, they are
not an optional part of the Baxandall tone control circuit. R8 & R10
are the only series resistors that I can see you have added to the basic
Baxandall tone control circuit, however I don't see how they could "make
the TCN a little easier on the ears"? Their effect on the response is
no different than if they weren't present in the circuit at all and you
had replaced VR3, the HF pot, with a 144k pot with mechanical stops to
limit the maximum amount of High Frequency boost and cut that could be
applied. The mechanical stops on the pot could even be eliminated to
some potential advantage if the user could keep his baser urges under
control.

If you want a tone control circuit that is easier on the ears I would
think a better course of action than your series resisters would be to
replace V4 with a 12AU7.

I did however notice that you have eliminated the isolation resister
that is traditionally used between the wipers of the pots in the
Baxandall type of tone control circuit. If you are interested in
counting beans, you could also save two capacitors by consolidating C5 &
C6 into a single capacitor connected between the two ends of VR2, and
replacing C7 & C8 with a single capacitor in series with the wiper of
VR3.

Maybe someone may like to simulate the performance in Spice or whatever.

Spice is hardly necessary to determine the effect of series resistors R8
& R10 on the circuit.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Iain Churches]

"Arny Krueger" wrote in message
. ..
"Phil Allison" wrote in message



** What a pile of masturbation fantasy CRAP !!!!

Phil, regrettably, it all seems real enough - no fantasy.

It may be crap, but it is gilt-edged crap. ;-)


On Friday, a gentleman to whom the unit
had been sent for evaluation on his home turf, sent a
message to say that he would be willing to provide finance
(venture capital) to fund the building of a series of these
preamplifiers. This man, who is the senior partner in a
high-end dealership, liked very much both what he
heard and what he saw.

The toolmaker starts on metalwork jigs and templates
today.

So he who laughs last, laughs longest,
Arns, m' dear ol' tambourine basher.


Cordially,
Iain

[bassett[_2_]]

"Iain Churches" wrote in message
. fi...

"Arny Krueger" wrote in message
. ..
"Phil Allison" wrote in message



** What a pile of masturbation fantasy CRAP !!!!

Phil, regrettably, it all seems real enough - no fantasy.

It may be crap, but it is gilt-edged crap. ;-)


On Friday, a gentleman to whom the unit
had been sent for evaluation on his home turf, sent a
message to say that he would be willing to provide finance
(venture capital) to fund the building of a series of these
preamplifiers. This man, who is the senior partner in a
high-end dealership, liked very much both what he
heard and what he saw.

The toolmaker starts on metalwork jigs and templates
today.

So he who laughs last, laughs longest,
Arns, m' dear ol' tambourine basher.


Cordially,
Iain

You would be wise to produce these on a ordered only basis, half
the cash with the order, the remainder on delivery. many people look at
something, then when the item is produced , they say they have changed
there minds.
Genuine people are few and far apart where money is concerned, You
may not believe this, but the genuine buyers will not object to a
payment with the order, and it des help with material costs,
especially when your out sourcing some of the work, they all want
paying on delivery of there products.

But if things go well, they will sell on recommendation, and while you
might not consider them a business, they just might end up
supplying you with a retirement fund. You might even consider
exporting downunder.
Good luck with your venture, but I really doubt Patrick will
offer to build for you on licence. We are all waiting for a Chinese
CLONE, of some of PT's better efforts.
bassett

[Patrick Turner]

Iain Churches wrote:

"Arny Krueger" wrote in message
. ..
"Phil Allison" wrote in message


** What a pile of masturbation fantasy CRAP !!!!

Phil, regrettably, it all seems real enough - no fantasy.

It may be crap, but it is gilt-edged crap. ;-)

On Friday, a gentleman to whom the unit
had been sent for evaluation on his home turf, sent a
message to say that he would be willing to provide finance
(venture capital) to fund the building of a series of these
preamplifiers. This man, who is the senior partner in a
high-end dealership, liked very much both what he
heard and what he saw.

The toolmaker starts on metalwork jigs and templates
today.

So he who laughs last, laughs longest,
Arns, m' dear ol' tambourine basher.

Cordially,
Iain

I hope the financing and production all go well for you Iain.


I still think you could do a little optimising to
give the ALCF circuit more idle current, say 4mA minimum.

Please feel free to experiment with constant current sources
and the use of a negative supply so the CCS cathode load
can be taken to the negative supply, and the CF is all above 0V,
with the grid input at 0V right off the gain pot wiper without
the additional C and R coupling.

The CF can also have its cathode output directly connected to the
primary of a 10K : 10k output transformer with entirely floating
secondary
for genuinely balanced output.
The primary is grounded and its dc winding resistance is often about
the right value to act asa bias resistor for the triode whose grid
is at 0V off the gain pot.
Anode supply need only be +150V, and no negative supply is needed.

Often the 4 mA of DC in the ungapped core
of a 1:1 ratio signal tranny won't cause a huge amount of dc saturation,
and the tranny while slightly dc magnetised should then not produce
so much 3H, and slightly more 2H.
Its going to be a very tiny amount because tranny distortions become
lower
as the driving triode output resistance becomes lower.

Electronically, the OPT driven with CF is a very simple circuit.

The option for balanced is a wanted feature in pro land.
Ever seen pro gear without XLR sockets on the rear panel?

And BTW, a dude here rescued an old church organ with 72 12AX7
oscillators
intact, but with a large number of serious problems.
He gradually stripped it down and I got a couple
of the oscillator chassis.

In the old days, building a gyrator using tubes was BS.
They'd always use a coil because it was cheaper than a tube.

So for a graphic eq where you want to exploit the
LC resonance once you have more than 3 bands, the tube plus LC
means you don't need 18 triodes for an eq you are considering.
Or, put it this way, 18 x 12AX7 will go a lot further
and give more bands if you use them for gain and do the reactive part
with coils of fine wire and caps.

Even the Quad 22 control unit had filters based around an LC circuit
for a sharp cut off noise filter for noisy records.
The coils had taps and switchable cut offs, and were very nicely made.

Quad 22 isn't my favourite preamp; its far too complex, has far too many
switches
and it tries to be able to wear every hat for every occasion, and get
away with
using 1 x EF86 for phono, tape or mic input, and just two halves of a
12AX7
for the line stage amp which has a large amount of open loop gain
and a shirtload of NFB with tone adjustments to control THD and IMD.
The remarkable thing is that the Quad 22 switches have been so reliable
for so long.

Patrick Turner.

[Ian Iveson]

Iain Churches wrote

On Friday, a gentleman to whom the unit
had been sent for evaluation on his home turf, sent a
message to say that he would be willing to provide finance
(venture capital) to fund the building of a series of these
preamplifiers. This man, who is the senior partner in a
high-end dealership, liked very much both what he
heard and what he saw.

The toolmaker starts on metalwork jigs and templates
today.

So he who laughs last, laughs longest,
Arns, m' dear ol' tambourine basher.

Just wondering what kind of things you laugh at. Are you sure it's not
too soon?

How many do you need to sell?

Have you sold them yet?

cheers, Ian

[Patrick Turner]

bassett wrote:

"Iain Churches" wrote in message
. fi...

"Arny Krueger" wrote in message
. ..
"Phil Allison" wrote in message



** What a pile of masturbation fantasy CRAP !!!!

Phil, regrettably, it all seems real enough - no fantasy.

It may be crap, but it is gilt-edged crap. ;-)


On Friday, a gentleman to whom the unit
had been sent for evaluation on his home turf, sent a
message to say that he would be willing to provide finance
(venture capital) to fund the building of a series of these
preamplifiers. This man, who is the senior partner in a
high-end dealership, liked very much both what he
heard and what he saw.

The toolmaker starts on metalwork jigs and templates
today.

So he who laughs last, laughs longest,
Arns, m' dear ol' tambourine basher.


Cordially,
Iain

You would be wise to produce these on a ordered only basis, half
the cash with the order, the remainder on delivery. many people look at
something, then when the item is produced , they say they have changed
there minds.
Genuine people are few and far apart where money is concerned, You
may not believe this, but the genuine buyers will not object to a
payment with the order, and it des help with material costs,
especially when your out sourcing some of the work, they all want
paying on delivery of there products.

But if things go well, they will sell on recommendation, and while you
might not consider them a business, they just might end up
supplying you with a retirement fund. You might even consider
exporting downunder.
Good luck with your venture, but I really doubt Patrick will
offer to build for you on licence. We are all waiting for a Chinese
CLONE, of some of PT's better efforts.

The Chinese will never bother to copy any of my designs.

They only know how to make something look pretty
to get a sale, and would never go to all the trouble I go to when i
build an amp.

I am almost utterly invisible and unknown in World Audio.

I have never lined up outside Stereophile magazine to buy another good
review
and pay squillions for a series of glossy adds after having invested a
million in stock which is in the shops.

After I get the rave review, the ratting really starts, and ppl think
there's
money in copying a brand like they copy Gucci and Rolex.

Idiots buy this crap.
The makers of the imitations ride on the bandwagon of someone else's
fame.

But in fact in the shops I see few imitations; they don't have to
imitate.
Cheap crummy Chinese tube amps sell well by direct order now.

Ppl's dreams about what they want on their equipment stands
are now more easily realised than ever before.
100 watts of tube power costs no more than a week's pay now.
In 1957, such power cost a fortune in wages.

Dreams can turn into nightmares sometimes, and I have had to rewire a
couple
of recently bought cheap Chinese tube amps to make sure the smoke does
not come out.

Hahso, if the smoke come out, it cannot put back in!

Patrick Turner.







bassett

[Arny Krueger]

"Ian Iveson" wrote in
message
. uk

Iain Churches wrote

On Friday, a gentleman to whom the unit
had been sent for evaluation on his home turf, sent a
message to say that he would be willing to provide
finance (venture capital) to fund the building of a
series of these preamplifiers. This man, who is the
senior partner in a high-end dealership, liked very much
both what he heard and what he saw.

The toolmaker starts on metalwork jigs and templates
today.

What are the details of the contract covering your royalties, Iain?

So he who laughs last, laughs longest,
Arns, m' dear ol' tambourine basher.

It ain't time for last, yet.

Just wondering what kind of things you laugh at. Are you
sure it's not too soon?

Point well taken.

How many do you need to sell?

Have you sold them yet?

More to the point - Iain, have you cashed any checks related to this
project?

[Iain Churches]

"Ian Iveson" wrote in message
. uk...
Just wondering what kind of things you laugh at. Are you sure it's not too
soon?

'Twas a turn of phrase, Ian.
Our friend Arny laughed at my and my pal's efforts.
But then that was to be expected.

Others thought this preamp sounded and looked
just as it should.

How many do you need to sell?
Don't really need to sell any. We are set up for
a short run of 10 pcs each psu and preamp.

Have you sold them yet?
The dealer who is funding the production of the
first batch takes them all.

Iain

[Iain Churches]

"Arny Krueger" wrote in message
. ..
"Ian Iveson" wrote in
message
. uk

Iain Churches wrote

On Friday, a gentleman to whom the unit
had been sent for evaluation on his home turf, sent a
message to say that he would be willing to provide
finance (venture capital) to fund the building of a
series of these preamplifiers. This man, who is the
senior partner in a high-end dealership, liked very much
both what he heard and what he saw.

The toolmaker starts on metalwork jigs and templates
today.

What are the details of the contract covering your royalties, Iain?

It is a standard venture-capital deal. This is the
way that many ideas are brought to fruition and
become products. The same method of finance
is common in recording projects also.

So he who laughs last, laughs longest,
Arns, m' dear ol' tambourine basher.

It ain't time for last, yet.

The money was in the bank today at 1200 hrs
as agreed.

More to the point - Iain, have you cashed any checks related to this
project?

See above. Arny, we haven't used cheques in Scandinavia
since 1981.

Iain.

[John Byrns]

In article ,
Patrick Turner wrote:

I still think you could do a little optimising to
give the ALCF circuit more idle current, say 4mA minimum.

Please feel free to experiment with constant current sources
and the use of a negative supply so the CCS cathode load
can be taken to the negative supply, and the CF is all above 0V,
with the grid input at 0V right off the gain pot wiper without
the additional C and R coupling.

The CF can also have its cathode output directly connected to the
primary of a 10K : 10k output transformer with entirely floating
secondary
for genuinely balanced output.

I like this idea, I have considered it several times because it
eliminates the need for a negative supply, and provides a floating
output not referenced to ground. Unfortunately I have not found a
suitable transformer designed for this service that is specified to
handle DC.

The primary is grounded and its dc winding resistance is often about
the right value to act asa bias resistor for the triode whose grid
is at 0V off the gain pot.
Anode supply need only be +150V, and no negative supply is needed.

Often the 4 mA of DC in the ungapped core
of a 1:1 ratio signal tranny won't cause a huge amount of dc saturation,
and the tranny while slightly dc magnetised should then not produce
so much 3H, and slightly more 2H.
Its going to be a very tiny amount because tranny distortions become
lower
as the driving triode output resistance becomes lower.

Electronically, the OPT driven with CF is a very simple circuit.

The option for balanced is a wanted feature in pro land.

All very desirable features, have you tested any commercially available
10K : 10k output transformers with DC to see what the actual distortion
is?

Ever seen pro gear without XLR sockets on the rear panel?

Yes, I have seen a lot of pro gear without XLR sockets on the rear
panel, barrier screw terminal strips used to be common on equipment
intended for permanent rack mount installation.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Iain Churches]

"bassett" wrote in message
...


You would be wise to produce these on a ordered only basis, half
the cash with the order, the remainder on delivery. many people look
at something, then when the item is produced , they say they have
changed there minds.
Genuine people are few and far apart where money is concerned,
You may not believe this, but the genuine buyers will not object to
a payment with the order, and it des help with material costs,
especially when your out sourcing some of the work, they all want
paying on delivery of there products.

Hi Bassett.

This is a standard venture capital deal.

But if things go well, they will sell on recommendation, and while
you might not consider them a business, they just might end up
supplying you with a retirement fund. You might even consider
exporting downunder.

:-)) Our capacity is such that I think we shall only be able to turn out
a small number - I prefer quality to quantity.

Good luck with your venture, but I really doubt Patrick will
offer to build for you on licence. We are all waiting for a Chinese
CLONE, of some of PT's better efforts.

No chance of the Chinese cloning anything of Patrick's. They are
interested only in the cheapest of cheap solutions dressed up to
look like something they are not. The Chinese prefer a generic
"one size fits all" pcb which they can use for amps from
10 to 100W. Patrick is more interested in tube-craft, which is
really what it is all about.

Iain

[Ian Iveson]

Iain Churches

How many do you need to sell?

Don't really need to sell any. We are set up for
a short run of 10 pcs each psu and preamp.

Have you sold them yet?

The dealer who is funding the production of the
first batch takes them all.

Crikey...nice work if you can get it. Did you cover all your own time
and expenses?

Does Arny get a cut for his contribution?

cheers, Ian

[Ian Iveson]

Iain Churches" wrote

No chance of the Chinese cloning anything of Patrick's. They are
interested only in the cheapest of cheap solutions dressed up to
look like something they are not. The Chinese prefer a generic
"one size fits all" pcb which they can use for amps from
10 to 100W.

This must surely be unfair to at least a few of the billions of
Chinese in the world. Why they may not be interested in cloning
Patrick's amps is a matter of conjecture. Personally, I can't see any
reason why they should.

Perhaps they respect his copyright?

cheers, Ian

[Sander deWaal]

"Ian Iveson" said:


Does Arny get a cut for his contribution?


ROFL!!! ;-)

--

- Maggies are an addiction for life. -

[bassett[_2_]]

"Iain Churches" wrote in message

No chance of the Chinese cloning anything of Patrick's. They are
interested only in the cheapest of cheap solutions dressed up to
look like something they are not. The Chinese prefer a generic
"one size fits all" pcb which they can use for amps from
10 to 100W. Patrick is more interested in tube-craft, which is
really what it is all about.

Iain

The Chinese manafacturing machine is now at a point where the japanese
where in the early 60's with there cheap and nasty models of everything,
But they evolved to a point where they became a world leader in there
products.

But having said that, I heard a Shanling C.D. player the other day,
and it did rate up with the best the world can produce.

The big problem will be in a few years when all the well known
manufacturers will no longer be around due to mass cloneing my the
chinese, as with the established manufacturers also comes the research
and development , which is needed in any product. It would seem th
Chinese do nothing of this, and simply Clone, to the point where even
the original manufacturers can,t tell the differance.

Also Jo consummer cares not about the quality of manufacture, and is
dictated in his choice by price. An example of this is el'cheapo DVD
players that are flooding the market here at the moment $39.00 yes
thirty nine dollars, gets you a DVD player that does everything and
sometimes more then a high priced model, And as people will tell you,
"So it blows, up" throw it away and buy another one.

Unfortunatly, this example is apparent in just about every consumable
these days.
There was a progrom on some time ago, where some bright Chinese
jeweller obtained Opal chips, from an Australian jeweller, The
Australian operation just swept them in the garbage bin. The Chinese
company bought them for practically nothing, paid people $2.00 an
hour to mount the scrappings and scrap Opal on to
Broaches, fiilled with an Araldite substance, and was making a small
fortune.

bassett

[Patrick Turner]

John Byrns wrote:

In article ,
Patrick Turner wrote:

I still think you could do a little optimising to
give the ALCF circuit more idle current, say 4mA minimum.

Please feel free to experiment with constant current sources
and the use of a negative supply so the CCS cathode load
can be taken to the negative supply, and the CF is all above 0V,
with the grid input at 0V right off the gain pot wiper without
the additional C and R coupling.

The CF can also have its cathode output directly connected to the
primary of a 10K : 10k output transformer with entirely floating
secondary
for genuinely balanced output.

I like this idea, I have considered it several times because it
eliminates the need for a negative supply, and provides a floating
output not referenced to ground. Unfortunately I have not found a
suitable transformer designed for this service that is specified to
handle DC.

The DC is very low, and may not cause any problems unless it was 30mA or
more.

The dc magnetisation shoud be under 0.8 tesla for this app, leaving
enough headroom for the small ac signal output.

Sowter or Lundahl would have something suitable.

If you have say 3,000 turns for each winding, and you have a core say
20mm x 30mm, then you can work out the probable dc flux density.
there are formulas for all this at my website.


The primary is grounded and its dc winding resistance is often about
the right value to act asa bias resistor for the triode whose grid
is at 0V off the gain pot.
Anode supply need only be +150V, and no negative supply is needed.

Often the 4 mA of DC in the ungapped core
of a 1:1 ratio signal tranny won't cause a huge amount of dc saturation,
and the tranny while slightly dc magnetised should then not produce
so much 3H, and slightly more 2H.
Its going to be a very tiny amount because tranny distortions become
lower
as the driving triode output resistance becomes lower.

Electronically, the OPT driven with CF is a very simple circuit.

The option for balanced is a wanted feature in pro land.

All very desirable features, have you tested any commercially available
10K : 10k output transformers with DC to see what the actual distortion
is?

No, but I did once use a 5K:16 ohm tranny powered with a paralleled
12AT7 without any problem to drive a spring box in a guitar amp reverb
unit
where maybe 20Vrms is the primary voltage.
The core was an ungapped GOSS, very small, like a speaker tranny in an
old radio.

But you need two equal voltage windings for maybe 1Vrms output.
If the load for the CF was ideally 20k, paralleling a twin triode allows
say 6mA and 10k load. The 10k impedance suggests that
the primary inductance has 10k reactance at 20Hz, and shunt C reactance
at 20kHz = 10k.
so Lp should be at least 80H, and Csh should be no more than 800pF.
In fact usually the LP will vary betwen 50H and 500H with ungapped GOSS,
and Csh will easily be 300pF.

Mu metal cores give much more L and less C for the same core size and
turns,
but are more prone to saturation with dc.



Ever seen pro gear without XLR sockets on the rear panel?

Yes, I have seen a lot of pro gear without XLR sockets on the rear
panel, barrier screw terminal strips used to be common on equipment
intended for permanent rack mount installation.

Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Iain Churches]

"Ian Iveson" wrote in message
. uk...
Iain Churches" wrote

Why they may not be interested in cloning Patrick's amps is a matter of
conjecture. Personally, I can't see any reason why they should.


Perhaps they respect his copyright?

Hardly:-) I saw an amp not long ago with a familiar looking
pot stamps "Elps" :-)

Iain

[Ian Iveson]

Iain wrote:

Perhaps they respect his copyright?

Hardly:-) I saw an amp not long ago with a familiar looking
pot stamps "Elps" :-)

Iain

Ha! Perfect. Genius!

Every little bit Elps.

I'll get by with a little Elp from my friends.

etc.

Wish I'd thought of it...

cheers, Ian

[Iain Churches]

"Ian Iveson" wrote in message
. uk...
Iain Churches

How many do you need to sell?

Don't really need to sell any. We are set up for
a short run of 10 pcs each psu and preamp.

Have you sold them yet?

The dealer who is funding the production of the
first batch takes them all.

Crikey...nice work if you can get it. Did you cover all your own time and
expenses?

The tooling cost is covered, but of course not
the time spent in shirtcuff and table napkin doodling:-)
Our return for this batch will be sufficient to fund
another two batches. We are already talking about
Series II, which will have an infra-red controller
with a stepped motor for the attenuator, and
remote input switching.

Does Arny get a cut for his contribution?

But of course. He is my inspiration to
better things, lest I too end up as a
computer repair man in SE Michigan:-)

Cheers
Iain

[Patrick Turner]

Iain Churches wrote:

"Ian Iveson" wrote in message
. uk...
Iain Churches

How many do you need to sell?

Don't really need to sell any. We are set up for
a short run of 10 pcs each psu and preamp.

Have you sold them yet?

The dealer who is funding the production of the
first batch takes them all.

Crikey...nice work if you can get it. Did you cover all your own time and
expenses?

The tooling cost is covered, but of course not
the time spent in shirtcuff and table napkin doodling:-)
Our return for this batch will be sufficient to fund
another two batches. We are already talking about
Series II, which will have an infra-red controller
with a stepped motor for the attenuator, and
remote input switching.

Nobody pays a cent for design/R&D work.
Ppl see something they like the look of, and have no idea how long a
special amp costs to make in terms of time,
and you are expected to make the special for the same price
someone charges for some crap mass produced item.
Often low volume production costs involved in making the item as stylish
looking as top brands
are quite prohibitive here. And when I did invest $3,000 for extremenly
well made metal
work for a dozen amps 3 years ago, nobody wanted the type of amp I
wanted to sell. ( Quad 40 level of finish )
They wanted SE amps on special chassis, with different features each
time.
So I have all these chassis stamped for tube sockets and cases for
trannies and cover plates et all
sitting under a bench here gathering dust.
They get on Ebay to buy second hand ARC and CJ or some Chinese crap item
rather than pay a lot more for the hand crafted item.
So I have to repair stuff just to pay bills. This work mounts up,
and it all takes lots of time nobody like paying for. And when someone
does try to
order something I have to say I have to finish the repairs first.
Maybe I can start in 3 month's time, so they'd get their amp in 6 mths.
But folks shopping on the Internet want an instant
fix, and I can't do instant fixes.
Have fun building a few amps, but don't be surprised if you don't do
very
well after selling a couple to people you know well.
When you have to compete with the world its a another matter, because
you have to be better than the
other gear out there, and cheaper, and available when they want it, ie,
right now.
So you could build things speculatively, and hope you find a buyer,
but often that can be very frustrating because it may take years to sell
what you have made.
Maybe I am cynical, but I am not part of a team who can operate together
to make and
then promote production. Nobody has ever said they'd provide capital.
There is a company in Sth Aust who began in about 1993 who have done OK
but
they had millions of dollars for the capital investment.
The amps they make are amoung the world's most expensive, and
apparently,
they are doing OK. See http://www.halcro.com/products.asp

When I searched around I could never find a motor drive for remote
control
of a stepped attenuator switch. The circuit you'll need just for
gain control will use lots of chips and about 75dB more circuitry that
the triode
amplifier it has to serve.

I built a preamp several years ago for a guy with DACT switches for
source select and gains.
But DACT don't seem to have drive motors and remote controls for their
swirches.
http://www.dact.com/
The switches I installed have lasted OK.

The only EQ the guy wanted was a shelved treble cut to reduce the
harshness found in some
digital recordings and reduce the top a little in his Vienna Acoustics.
the wafer rotary type of switch seemed only type I thought appropriate.
I wasn't ever going to use a set of toggle switches, let alone a row of
pressbutton types.

Rotary wafers have sliding self cleaning contacts, and good quality are
available
from Farnell, and are 20dB cheaper than anything from DACT.
If at some future time a change is to be made to the amp topology or
features,
the wafer switch can be easily removed/changed/modded.

Being able to do tone control from a distance would be useful for
a hi-fi listener, but why would it be wanted by a pro in a studio?
Don't they have to be able to alter eq of each track while monitors are
set up
so they can be near the desk, and listen from ideal speaker monitor
speaker positioning?

One can easily set out to design a puppy dog, and end up with a camel.

Patrick Turner.

[Ian Iveson]

Iain Churches wrote

...We are already talking about
Series II, which will have an infra-red controller
with a stepped motor for the attenuator, and
remote input switching.

Including a transmitter? Which protocol will you use? Which chip? What
kind of relays? Or fet switches?

cheers, Ian

[bassett[_2_]]

"Patrick Turner" wrote in message

Nobody pays a cent for design/R&D work.
Ppl see something they like the look of, and have no idea how long a
special amp costs to make in terms of time,
and you are expected to make the special for the same price
someone charges for some crap mass produced item.
Often low volume production costs involved in making the item as stylish
looking as top brands
are quite prohibitive here. And when I did invest $3,000 for extremenly
well made metal
work for a dozen amps 3 years ago, nobody wanted the type of amp I
wanted to sell. ( Quad 40 level of finish )
They wanted SE amps on special chassis, with different features each
time.
So I have all these chassis stamped for tube sockets and cases for
trannies and cover plates et all
sitting under a bench here gathering dust.
They get on Ebay to buy second hand ARC and CJ or some Chinese crap item
rather than pay a lot more for the hand crafted item.
So I have to repair stuff just to pay bills. This work mounts up,
and it all takes lots of time nobody like paying for. And when someone
does try to
order something I have to say I have to finish the repairs first.
Maybe I can start in 3 month's time, so they'd get their amp in 6 mths.
But folks shopping on the Internet want an instant
fix, and I can't do instant fixes.

For ****'s sake, some send patrick a box of Tissues

[Iain Churches]

"Ian Iveson" wrote in message
news
Iain Churches wrote

...We are already talking about
Series II, which will have an infra-red controller
with a stepped motor for the attenuator, and
remote input switching.

Including a transmitter? Which protocol will you use? Which chip? What
kind of relays? Or fet switches?

cheers, Ian

A pal of mine who helped me with the square wave analysis
pics, works in a national research establishment as a prototype
engineer. This kind of thing is just his cup of tea. Yesterday he
brought me a stepped motor with a 6mm and 6.3mm sleeve
which drives an attenuator nicely.

We have discussed only briefly the controller board, but the
idea is to incorporate four inputs plus a mute, FET switched.
It will probably take him a week or two to put something
together.

Iain

[west[_3_]]

"Ian Iveson" wrote in message
. uk...
Iain Churches" wrote

No chance of the Chinese cloning anything of Patrick's. They are
interested only in the cheapest of cheap solutions dressed up to
look like something they are not. The Chinese prefer a generic
"one size fits all" pcb which they can use for amps from
10 to 100W.

This must surely be unfair to at least a few of the billions of
Chinese in the world. Why they may not be interested in cloning
Patrick's amps is a matter of conjecture. Personally, I can't see any
reason why they should.

I know that you are not the brightest LED in this group Iverson, but how
many Billions of Chinese do you think there are?

west


Perhaps they respect his copyright?

cheers, Ian