[Ian Thompson-Bell]

Iain Churches wrote:
"Tynan AgviÐr" wrote in message
. 70...
is 80 dB enough for this?

Regards,

John Byrns

With the mics I am currently using, 80dB is good.My current mic pres have
66, and that is *barely* enough.

OK. So that's me back to the drawing board:-)
Except that my mic pre is to be plugged into the
line input of a console so 60dB is more than sufficient.

Line in of a console - sorry can you explain what that is??

Cheers

Ian

[Iain Churches[_2_]]

"Ian Thompson-Bell" wrote in message
...
John Byrns wrote:

I have also started thinking about packaging issues, which may lead to
some changes in the mixer section. I can't remember if the OP said
anything about his size and weight requirements?


This is important not only from an aethestics point of view but also from
an electronic performance one too.



Wasn't it Graham who mentioned the possibility of a
3U 19 inch rack mounted construction with plug in,
modular channels? This might be a very good format.
The psu could then be in its own chassis.

A mixer does not necessarily have to have a horizontal
operational surface, particularly if rotary faders are chosen.


Iain

[Ian Thompson-Bell]

Iain Churches wrote:
"Ian Thompson-Bell" wrote in message
...
John Byrns wrote:

I have also started thinking about packaging issues, which may lead to
some changes in the mixer section. I can't remember if the OP said
anything about his size and weight requirements?


This is important not only from an aethestics point of view but also from
an electronic performance one too.



Wasn't it Graham who mentioned the possibility of a
3U 19 inch rack mounted construction with plug in,
modular channels? This might be a very good format.
The psu could then be in its own chassis.

A mixer does not necessarily have to have a horizontal
operational surface, particularly if rotary faders are chosen.



How are you going to get the channel faders to fit in this space or were
you thinking of rotary controls?

Cheers

Ian

[Iain Churches[_2_]]

"Ian Thompson-Bell" wrote in message
...
Iain Churches wrote:
"Ian Thompson-Bell" wrote in message
...
John Byrns wrote:

I have also started thinking about packaging issues, which may lead to
some changes in the mixer section. I can't remember if the OP said
anything about his size and weight requirements?


This is important not only from an aethestics point of view but also
from an electronic performance one too.



Wasn't it Graham who mentioned the possibility of a
3U 19 inch rack mounted construction with plug in,
modular channels? This might be a very good format.
The psu could then be in its own chassis.

A mixer does not necessarily have to have a horizontal
operational surface, particularly if rotary faders are chosen.



How are you going to get the channel faders to fit in this space or were
you thinking of rotary controls?

Some early mixers were made like this for OB and
location recording use. The ones I have seen invariably
had rotary faders. Short throw linear faders tend to be
cheap and cheerful, not at all suitable for this prestigious
project:-)

Iain

[Ian Thompson-Bell]

Iain Churches wrote:
"Ian Thompson-Bell" wrote in message
...
Iain Churches wrote:
"Ian Thompson-Bell" wrote in message
...
John Byrns wrote:
I have also started thinking about packaging issues, which may lead to
some changes in the mixer section. I can't remember if the OP said
anything about his size and weight requirements?


This is important not only from an aethestics point of view but also
from an electronic performance one too.


Wasn't it Graham who mentioned the possibility of a
3U 19 inch rack mounted construction with plug in,
modular channels? This might be a very good format.
The psu could then be in its own chassis.

A mixer does not necessarily have to have a horizontal
operational surface, particularly if rotary faders are chosen.


How are you going to get the channel faders to fit in this space or were
you thinking of rotary controls?

Some early mixers were made like this for OB and
location recording use. The ones I have seen invariably
had rotary faders. Short throw linear faders tend to be
cheap and cheerful, not at all suitable for this prestigious
project:-)

Iain



I wasn't thinking of short throw faders, but proper P&G types.

Ian

[Eeyore]

"Tynan AgviÐr" wrote:

is 80 dB enough for this?

80dB is what I'd recommend. Certainly no less than 70dB.


With the mics I am currently using, 80dB is good.My current mic pres have
66, and that is *barely* enough.

With ribbon mics I expect that's especially so.

Graham

[Eeyore]

robert casey wrote:

Are you claiming that you need to *design* a cathode follower for example ? Or
*design* a volume control ?

Well, you'd need to know if the OP user wants slide pots or twist knobs.
and other such ergonomic considerations. And select such accordingly.
But that would not change anything in the schematic design.

Indeed.

Graham

[Eeyore]

Ian Thompson-Bell wrote:

Eeyore wrote:
John Byrns wrote:

I concentrated on the design of the mixer section

Yes, that'll require a triode with AC coupled nfb from anode to grid to form
the virtual earth, the remainder being routine mix Rs, level controls etc.

That's hardly a DESIGN. It's a stock circuit.


Hmmm, that assumes virtual earth mixing is the way to go for tubes. A
typical triode will have a stage gain of 20 maybe 30dB so the virtual
earth will not be that good (Rfb/30 maybe) and there's not really enough
gain to make up for mix losses.

Gain at the mix amp is invariably noisy. Placing 'gain in hand' would be best
after the fader and that's also best for low THD.


Also Rfb needs to be large enough not to
significantly load the anode, so we are talking 300K or so here which
means the mix resistors will be 100K for for 10dB gain make up.

Ahh... well my design with a buffered anode wouldn't have that restriction.


If you want to stick with VE mixing then a tubed long tailed pair and
another triode will make a simple op amp like circuit where Rfb can be
much smaller and the open loop gain is much higher making a better VE.

Or simpler still just stick a CF on the end of the triode and feed its
cathode back to the grid via a lowish Rfb.

That would be another way.

Graham

[Eeyore]

Ian Thompson-Bell wrote:

Eeyore wrote:

The pad is *inline* with the signal path, NOT the phantom power.


Actually Graham I was referring to a pad external to the mixer, added
in-line with the mic cable so the pad *is* in-line with the phantom
power. This pad is additional to the 20dB pad inside the mixer which as
you rightly say in only in the signal path.

Oh I see. I imagined this mixer would have an internal pad. It would be
essential IMHO.

An external 20dB pad would add about 1k in each leg which wouldn't be a
disaster.

Graham

[Eeyore]

Ian Thompson-Bell wrote:

Iain Churches wrote:
"Ian Thompson-Bell" wrote
John Byrns wrote:

I have also started thinking about packaging issues, which may lead to
some changes in the mixer section. I can't remember if the OP said
anything about his size and weight requirements?

This is important not only from an aethestics point of view but also from
an electronic performance one too.

Wasn't it Graham who mentioned the possibility of a
3U 19 inch rack mounted construction with plug in,
modular channels? This might be a very good format.
The psu could then be in its own chassis.

A mixer does not necessarily have to have a horizontal
operational surface, particularly if rotary faders are chosen.


How are you going to get the channel faders to fit in this space or were
you thinking of rotary controls?

My idea was to have rotary controls on the rack mount unit itself so it's self
contained and compact and these could be bypassed with external slide faders
that could be mounted in an ancillary 'pod'. Just a thought.

Graham

[Eeyore]

Ian Thompson-Bell wrote:

I wasn't thinking of short throw faders, but proper P&G types.

I shudder to think of the cost of those now !

ALPS also make some decent 'studio faders'. Yes, genuine ones with guide rails
and minimal friction etc.

Graham

[Iain Churches[_2_]]

"Eeyore" wrote in message
...


Ian Thompson-Bell wrote:

I wasn't thinking of short throw faders, but proper P&G types.

I shudder to think of the cost of those now !

Indeed very expensive. Some old-style "quadrant" faders
would be appropriate if they could be found.

Iain

[Eeyore]

Iain Churches wrote:

"Eeyore" wrote
Ian Thompson-Bell wrote:

I wasn't thinking of short throw faders, but proper P&G types.

I shudder to think of the cost of those now !

Indeed very expensive. Some old-style "quadrant" faders
would be appropriate if they could be found.

I'm not sure what you think they could offer other than an antique look.
I'd certainly not like to mix in 3dB steps or whatever it is they
provide. Plus aren't they mostly 600 ohm and therefore need further
buffering ?

Graham

[John Byrns]

In article ,
Eeyore wrote:

John Byrns wrote:

Eeyore wrote:
John Byrns wrote:
Eeyore wrote:

No, a pad isn't a problem. The phantom power resistors still go
direct to
the XLR pins 2 and 3.

You obviously missed the "in-line pad" part, an in-line pad definitely
has the potential to cause a problem if the wrong type of pad is used.

The pad is *inline* with the signal path, NOT the phantom power.

Can you explain how an inline pad is going to be able to avoid being in
series with the phantom power?

HOLY ****.

You're dumb as they come for sure.

The phantom power NEVER flows through the pad (or it shouldn't at least). See
if
you can't draw yourself a circuit with the 6k8 phnatom power Rs going to pins
2 and
3 of the XLT input connector for the mic and try and work it out for yourself
will
you ?

I already did exactly that, and the phantom power definitely flows
through the pad as a common mode signal. Can you explain how the
phantom power might get to the microphone if not through the pad, there
is no other route it can take?


Regards,

John Byrns

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

[Tynan AgviÐr]

robert casey wrote in
:


Are you claiming that you need to *design* a cathode follower for
example ? Or *design* a volume control ?


Well, you'd need to know if the OP user wants slide pots or twist
knobs.
and other such ergonomic considerations. And select such
accordingly. But that would not change anything in the schematic
design.

Well, i prefer sliders by a huge margin, but aint above using twist pots if
there is any benefit to it, sonically.

[John Byrns]

In article ,
Ian Thompson-Bell wrote:

John Byrns wrote:
In article ,
Ian Thompson-Bell wrote:

John Byrns wrote:
I have completed a preliminary design for a 6-in 2-out microphone mixer
similar to the one requested by ³Tynan².
Excellent. Care to post a schematic?

There are a couple of problems with doing that right now. First my
scanner has been broken for some time and I either need to repair it, or
buy a new one. The repair should be simple if I can locate the required
material. The problem is that I left a stack of books piled on top of
the scanner for too long a time period, and this caused the thin double
sided tape that was used to attach the glass to loose its grip. To fix
it I would need to find some suitable thin double sided tape. I should
probably just bin it and buy a new one because it only interfaces with
my old computer anyway.

Hope you get it fixed soon.

It is more likely headed for the trash bin, to be replaced by a new one
thereby eliminating the hassle of getting out my old computer to run it.

I would love to see what you have come up
with. I notice your web page is mainly radio related - is that you main
tube interst?

Yes, early in my life I worked for a while in broadcasting, so I have a
fondness for radio related stuff.


Regards,

John Byrns





The second problem is that I took this design as a two-part problem, the
design of a microphone amplifier and the design of a mixer. I
concentrated on the design of the mixer section, only laying out a
concept for my own microphone amplifier design. From previous
discussions I had assumed that the idea was to paste in the schematic of
the end users favorite vintage tube microphone amplifier. I have had a
tube microphone amplifier module sitting on my desk next to my computer
for the last 8 years, so yesterday I decided to try interfacing that
with my mixer design. I immediately ran into a major problem using this
existing microphone amplifier design, and I realized that several other
existing microphone amplifier designs would also have similar problems.


Welcome to the world of mixer design.

As a result I am left without a suitable design for the microphone
amplifier section until I can complete my own design. I am left
agonizing over how to accomplish all my goals for the microphone
amplifier without having to make compromises that I would rather avoid.


Welcome to the world of mixer design.

I have also started thinking about packaging issues, which may lead to
some changes in the mixer section. I can't remember if the OP said
anything about his size and weight requirements?


This is important not only from an aethestics point of view but also
from an electronic performance one too.

Good Luck

Ian

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

[Tynan AgviÐr]

"Iain Churches" wrote in news:hZijj.281635$sV4.19102
@reader1.news.saunalahti.fi:

I was just thinking ahead. He may not want them now, but
experience tells me that it will not be long before he wants
to patch some extermal EQ or processor (even a simple limiter)
into a single channel or across the output mix buss.

A simple mixer, if it is to be of any practical use, is not
actually terribly simple.

Iain



I never use these things, and dont ever see myself using them. Perhaps if I
were working in the studio realm in "secular" music, but I work with
acoustic based(Chamber Jazz, String/Woodwind quartets, Appalachian Folk,
Bluegrass, acapella vocal stuff, choral) music exclusively and my studio is
the concert venue. I like things to be as simple as humanly possible for
myriad reasons, the largest of which being that it always sounds better..

[Tynan AgviÐr]

As far as layout goes, and features, the Wendt X4/x5 is nearly perfect.
Unfortunately, it sounds like hot ass. I of course know that the actual
layout on the requested mixer could not be anything like that, but the
features are spot-on. (I dont need the ENG port though)

http://www.wendtinc.net/x4specs.pdf

http://www.wendtinc.net/x4specs.htm

[John Byrns]

In article ,
Eeyore wrote:

Ian Thompson-Bell wrote:

Eeyore wrote:

The pad is *inline* with the signal path, NOT the phantom power.


Actually Graham I was referring to a pad external to the mixer, added
in-line with the mic cable so the pad *is* in-line with the phantom
power. This pad is additional to the 20dB pad inside the mixer which as
you rightly say in only in the signal path.

Oh I see. I imagined this mixer would have an internal pad. It would be
essential IMHO.

An external 20dB pad would add about 1k in each leg which wouldn't be a
disaster.

Graham, you have a worse reading comprehension problem than I do! Not
only was Ian referring to an "in-line" pad as I pointed out to you in an
earlier post, but the proposed mixer does include a built in switchable
20 dB pad as Ian mentioned above. My impression was that Ian was
proposing the possibility of using an additional pad when input levels
are above what can be handled by a microphone amplifier with limited
gain adjustment capability even with the internal 20 dB pad.


Regards,

John Byrns

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

[Ian Thompson-Bell]

Eeyore wrote:

Gain at the mix amp is invariably noisy. Placing 'gain in hand' would be best
after the fader and that's also best for low THD.



Quite right. Missed that one.

Cheers

Ian

[Ian Thompson-Bell]

Eeyore wrote:

Ian Thompson-Bell wrote:

Eeyore wrote:
The pad is *inline* with the signal path, NOT the phantom power.

Actually Graham I was referring to a pad external to the mixer, added
in-line with the mic cable so the pad *is* in-line with the phantom
power. This pad is additional to the 20dB pad inside the mixer which as
you rightly say in only in the signal path.

Oh I see. I imagined this mixer would have an internal pad. It would be
essential IMHO.


I imagined it would too. However, if a minimum gain of 0db was required,
this could present problems with the first stage valve input level i.e.
-20dB in the *internal pad*, +20dB in the input transformer = 0dBu at
the first valve grid. As the first valve is typically biased at about
-1V a 0dB input signal could cause significant grid rectification
distortion. Hence my suggestion for a minimum 20dB gain and -20dBu max
input (=-20dBu max on first stage grid). If the OP really did have a
0dBu input then I suggested an *additional* external 20dB pad would do
the trick.

Cheers

Ian

[Ian Thompson-Bell]

Tynan AgviÐr wrote:
As far as layout goes, and features, the Wendt X4/x5 is nearly perfect.
Unfortunately, it sounds like hot ass. I of course know that the actual
layout on the requested mixer could not be anything like that, but the
features are spot-on. (I dont need the ENG port though)

http://www.wendtinc.net/x4specs.pdf

http://www.wendtinc.net/x4specs.htm


Doesn't seem to mention the gain provided.

Cheers

Ian

[Ian Thompson-Bell]

John Byrns wrote:
In article ,
Eeyore wrote:

Ian Thompson-Bell wrote:

Eeyore wrote:
The pad is *inline* with the signal path, NOT the phantom power.

Actually Graham I was referring to a pad external to the mixer, added
in-line with the mic cable so the pad *is* in-line with the phantom
power. This pad is additional to the 20dB pad inside the mixer which as
you rightly say in only in the signal path.
Oh I see. I imagined this mixer would have an internal pad. It would be
essential IMHO.

An external 20dB pad would add about 1k in each leg which wouldn't be a
disaster.

Graham, you have a worse reading comprehension problem than I do! Not
only was Ian referring to an "in-line" pad as I pointed out to you in an
earlier post, but the proposed mixer does include a built in switchable
20 dB pad as Ian mentioned above. My impression was that Ian was
proposing the possibility of using an additional pad when input levels
are above what can be handled by a microphone amplifier with limited
gain adjustment capability even with the internal 20 dB pad.



Spot on.

Cheers

Ian

[John Byrns]

In article ,
"Tynan AgviÐr" wrote:

As far as layout goes, and features, the Wendt X4/x5 is nearly perfect.
Unfortunately, it sounds like hot ass. I of course know that the actual
layout on the requested mixer could not be anything like that, but the
features are spot-on. (I dont need the ENG port though)

http://www.wendtinc.net/x4specs.pdf

http://www.wendtinc.net/x4specs.htm

How can the layout of the Wendt X4/x5 be nearly perfect, it looks like
it uses rotary faders?


Regards,

John Byrns

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

[Iain Churches[_2_]]

"Tynan AgviÐr" wrote in message
. 3.70...
"Iain Churches" wrote in news:hZijj.281635$sV4.19102
@reader1.news.saunalahti.fi:

I was just thinking ahead. He may not want them now, but
experience tells me that it will not be long before he wants
to patch some extermal EQ or processor (even a simple limiter)
into a single channel or across the output mix buss.

A simple mixer, if it is to be of any practical use, is not
actually terribly simple.

I never use these things, and dont ever see myself using them. Perhaps if
I
were working in the studio realm in "secular" music, but I work with
acoustic based(Chamber Jazz, String/Woodwind quartets, Appalachian Folk,
Bluegrass, acapella vocal stuff, choral) music exclusively and my studio
is
the concert venue.


You have an interesting range of recording repertoire.
Mine is restricted to only two of these, classical
(mainly baroque) ensembles and jazz. For the latter,
I would not even consider a console without
good EQ and a gentle compressor or two.

For Bluegrass, I think I would want the full Neve
and all the bells and whistles it can offer:-)

It may well be that something you consider
inessential now, will prove to be of vital importance
just a little way down the road. If you are going to
the time and expense of having a mixer custom
built, plan it very very carefully.

I like things to be as simple as humanly
possible for myriad reasons, the largest of
which being that it always sounds better..

That's why I suggested pre and post insert point.
You then have simple straight path when no
outboard units are connected.

Iain

[Iain Churches[_2_]]

"Tynan AgviÐr" wrote in message
. 3.70...
"Iain Churches" wrote in news:hZijj.281635$sV4.19102
@reader1.news.saunalahti.fi:

I was just thinking ahead. He may not want them now, but
experience tells me that it will not be long before he wants
to patch some extermal EQ or processor (even a simple limiter)
into a single channel or across the output mix buss.

A simple mixer, if it is to be of any practical use, is not
actually terribly simple.

I never use these things, and dont ever see myself using them. Perhaps if
I
were working in the studio realm in "secular" music, but I work with
acoustic based(Chamber Jazz, String/Woodwind quartets, Appalachian Folk,
Bluegrass, acapella vocal stuff, choral) music exclusively and my studio
is
the concert venue.


You have an interesting range of recording repertoi-)
Mine is restricted to only two of these, classical
(mainly baroque) ensembles and jazz. For the latter,
I would not even consider a console without
good EQ and a gentle compressor or two.

For Bluegrass, I think I would want the full Neve
and all the bells and whistles it can offer:-)

It may well be that something you consider
inessential now, will prove to be of vital importance
just a little way down the road. If you are going to
the time and expense of having a mixer custom
built, plan it very very carefully.

I like things to be as simple as humanly
possible for myriad reasons, the largest of
which being that it always sounds better..

That's why I suggested pre and post insert point.
You then have simple straight path when no
outboard units are connected.

Iain

[Iain Churches[_2_]]

"Tynan AgviÐr" wrote in message
. 3.70...
"Iain Churches" wrote in news:hZijj.281635$sV4.19102
@reader1.news.saunalahti.fi:

I was just thinking ahead. He may not want them now, but
experience tells me that it will not be long before he wants
to patch some extermal EQ or processor (even a simple limiter)
into a single channel or across the output mix buss.

A simple mixer, if it is to be of any practical use, is not
actually terribly simple.

I never use these things, and dont ever see myself using them. Perhaps if
I
were working in the studio realm in "secular" music, but I work with
acoustic based(Chamber Jazz, String/Woodwind quartets, Appalachian Folk,
Bluegrass, acapella vocal stuff, choral) music exclusively and my studio
is
the concert venue.


You have an interesting range of recording repertoi-)
Mine is restricted to only two of these, classical
(mainly baroque) ensembles and jazz. For the latter,
I would not even consider a console without
good EQ and a gentle compressor or two.

For Bluegrass, I think I would want the full Neve
and all the bells and whistles it can offer:-)

It may well be that something you consider
inessential now, will prove to be of vital importance
just a little way down the road. If you are going to
the time and expense of having a mixer custom
built, plan it very very carefully.

I like things to be as simple as humanly
possible for myriad reasons, the largest of
which being that it always sounds better..

That's why I suggested pre and post insert point.
You then have simple straight path when no
outboard units are connected.

Iain

[John Byrns]

In article ,
Ian Thompson-Bell wrote:

John Byrns wrote:
In article ,
Ian Thompson-Bell wrote:

The one thing John did not mention in his spec was the mic pre gain (or
overall gain for that matter). What's yours?

The current iteration of my design has a gain of 80 dB from microphone
input to line output, 10 dB of this is in the output amplifier,
excluding makeup gain. I used this number because it was repeatedly
mentioned in the original thread, however I am not a "pro audio"
designer and don't know exactly how much gain might actually be
required. I would like enough gain to be able to use RCA ribbon mics,
or similar, for that vintage sound, is 80 dB enough for this?



I know of no pro mixer with more than 80dB gain so from that point of
view it should be enough. It will be hard to get better than 50dB S/N
with 80dB of gain so more would be rather pointless and I don't think
even the most insenstive ribbon would need more gain than that.

The big question is what method have you used to vary the gain?

In the current iteration of my design, the overall gain of 80 dB is
allocated as follows, input transformer 20 dB, microphone amplifier 50
dB, and output amplifier 10 dB exclusive of makeup gain. There is a
switchable 20 dB pad at the input, and the gain of the microphone
amplifier proper can be varied between 50 dB and zero dB in steps of
perhaps 10 dB. The amplifier consists of two stages each with a gain of
34 dB. 18 dB of negative feedback is applied by a feedback loop around
the two stages. This feedback should improve the overload margin at the
input by 18 dB. The gain is varied by an attenuator between the two
stages with attenuation variable between 0 dB and 50 dB, the same switch
also adjusts the feedback loop so that the overall feedback remains 18
dB at all attenuation settings. That is my current thinking on the
matter, but it is subject to change at any time.


Regards,

John Byrns

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

[John Byrns]

In article ,
Ian Thompson-Bell wrote:

Eeyore wrote:

John Byrns wrote:

I concentrated on the design of the mixer section

Yes, that'll require a triode with AC coupled nfb from anode to grid to form
the virtual earth, the remainder being routine mix Rs, level controls etc.

That's hardly a DESIGN. It's a stock circuit.

Graham


Hmmm, that assumes virtual earth mixing is the way to go for tubes. A
typical triode will have a stage gain of 20 maybe 30dB so the virtual
earth will not be that good (Rfb/30 maybe) and there's not really enough
gain to make up for mix losses. Also Rfb needs to be large enough not to
significantly load the anode, so we are talking 300K or so here which
means the mix resistors will be 100K for for 10dB gain make up.

I have at least for the moment dropped the idea of virtual earth mixing
from my design, however my original virtual earth design used a feedback
resistor around the tube providing the virtual earth function, equal in
value to the resistors used for each channels connection to the virtual
earth mix bus. Driving this relatively low value feedback resistor was
done by using the same buffer circuit, perhaps a CF, used in the channel
modules which have the same problem driving the mixing resistors. With
this scheme of equal value resistors the mixer circuit proper has a gain
of unity.

If you want to stick with VE mixing then a tubed long tailed pair and
another triode will make a simple op amp like circuit where Rfb can be
much smaller and the open loop gain is much higher making a better VE.

Or simpler still just stick a CF on the end of the triode and feed its
cathode back to the grid via a lowish Rfb.

That was essentially my original scheme, noting that the problem of
driving the feedback resistor is no worse than that of the individual
channels driving their mixing resistors.


Regards,

John Byrns

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

[Tynan AgviÐr]

John Byrns wrote in news:byrnsj-
:

In article ,
"Tynan AgviÐr" wrote:

As far as layout goes, and features, the Wendt X4/x5 is nearly perfect.
Unfortunately, it sounds like hot ass. I of course know that the actual
layout on the requested mixer could not be anything like that, but the
features are spot-on. (I dont need the ENG port though)

http://www.wendtinc.net/x4specs.pdf

http://www.wendtinc.net/x4specs.htm

How can the layout of the Wendt X4/x5 be nearly perfect, it looks like
it uses rotary faders?


Regards,

John Byrns


I meant the features, primarily.

(of course the extra stuff like all the bass cuts..not needed)

[Tynan AgviÐr]

Ian Thompson-Bell wrote in news:fmlb25$tuc$1
@energise.enta.net:

Tynan AgviÐr wrote:
As far as layout goes, and features, the Wendt X4/x5 is nearly perfect.
Unfortunately, it sounds like hot ass. I of course know that the actual
layout on the requested mixer could not be anything like that, but the
features are spot-on. (I dont need the ENG port though)

http://www.wendtinc.net/x4specs.pdf

http://www.wendtinc.net/x4specs.htm


Doesn't seem to mention the gain provided.

Cheers

Ian


Ian, i meant features, Sir. The Features are pretty much what I would want.

[Ian Thompson-Bell]

John Byrns wrote:
In the current iteration of my design, the overall gain of 80 dB is
allocated as follows, input transformer 20 dB, microphone amplifier 50
dB, and output amplifier 10 dB exclusive of makeup gain. There is a
switchable 20 dB pad at the input, and the gain of the microphone
amplifier proper can be varied between 50 dB and zero dB in steps of
perhaps 10 dB. The amplifier consists of two stages each with a gain of
34 dB. 18 dB of negative feedback is applied by a feedback loop around
the two stages. This feedback should improve the overload margin at the
input by 18 dB. The gain is varied by an attenuator between the two
stages with attenuation variable between 0 dB and 50 dB, the same switch
also adjusts the feedback loop so that the overall feedback remains 18
dB at all attenuation settings. That is my current thinking on the
matter, but it is subject to change at any time.



A novel scheme. I shall have to think about that topology.

Cheers

Ian

[robert casey]

It is more likely headed for the trash bin, to be replaced by a new one
thereby eliminating the hassle of getting out my old computer to run it.


Before such things get tossed, I usually take it apart to salvage any
usable parts, line cords, circuit boards bearing a few discrete parts
like caps, resistors, transistors (heresy in this NG), and the metric
screws and nuts (hard to come by in American hardware stores). This is
an old tradition in ham radio, the "junk box"... Other bits of it end
up in the recycling can, with the beer cans and plastic or glass bottles
and packaging.

[Ian Iveson]

John wrote:

...
Both the line amplifier and the headphone amplifier are
push pull
circuits. The microphone amplifiers are "SE", as 6 push
pull microphone
amplifiers seemed a bit much for a portable mixer.
...

For what reasons do you perceive PP to be preferable in this
application?

In particular, why, after converting from balanced to SE,
you decided on PP for the output stages?

I have been dipping into the thread occasionally hoping to
find the bit where voicing is discussed. I wonder by what
process an agreement about desired quality of sound can be
reached remotely with a prospective end user who wants
"something special"

Anyway, I'm impressed with your simple approach, and the way
you have stuck to the brief without contracting Recalcitrant
Engineers' Syndrome. Perhaps your experience of designing
valve circuits has made you more wary of added complexity.

Ian (wondering in passing what a pad is...but don't worry,
I'll look it up)

[Eeyore]

"Tynan AgviÐr" wrote:

Ian Thompson-Bell wrote
Tynan AgviÐr wrote:

As far as layout goes, and features, the Wendt X4/x5 is nearly perfect.
Unfortunately, it sounds like hot ass. I of course know that the actual
layout on the requested mixer could not be anything like that, but the
features are spot-on. (I dont need the ENG port though)

http://www.wendtinc.net/x4specs.pdf

http://www.wendtinc.net/x4specs.htm


Doesn't seem to mention the gain provided.


Ian, i meant features, Sir. The Features are pretty much what I would want.

So really very straighforward.

Graham

[Eeyore]

Ian Iveson wrote:

I have been dipping into the thread occasionally hoping to
find the bit where voicing is discussed. I wonder by what
process an agreement about desired quality of sound can be
reached remotely with a prospective end user who wants
"something special"

Indeed. I'd like to know if Tynan has a particular benchmark tubed mic
pre that he likes already.

snip

Ian (wondering in passing what a pad is...but don't worry,
I'll look it up)

Attenuator.

Graham

[John Byrns]

In article ,
"Ian Iveson" wrote:

John wrote:

...
Both the line amplifier and the headphone amplifier are
push pull
circuits. The microphone amplifiers are "SE", as 6 push
pull microphone
amplifiers seemed a bit much for a portable mixer.
...

For what reasons do you perceive PP to be preferable in this
application?

In particular, why, after converting from balanced to SE,
you decided on PP for the output stages?

Two main reasons. First to eliminate DC from the output transformer so
that it can be smaller and have better performance. Second to achieve
the output power level I desired with a small tube that is used at other
locations in the mixer, reducing the number of required tube types to
two.

I have been dipping into the thread occasionally hoping to
find the bit where voicing is discussed. I wonder by what
process an agreement about desired quality of sound can be
reached remotely with a prospective end user who wants
"something special"

Anyway, I'm impressed with your simple approach,

I have been worrying that my approach is overly complex, there are much
simpler approaches, look at a few remote mixers from the 1950s for ideas.

and the way
you have stuck to the brief without contracting Recalcitrant
Engineers' Syndrome.

What pray tell is "Recalcitrant Engineers' Syndrome", I have never heard
of that before?

Perhaps your experience of designing
valve circuits has made you more wary of added complexity.

A circuit should not be so simple it can't do the job properly, nor
should it be more complex than is needed to do the job. A lot of people
seem to pursue complexity for complexities sake.


Regards,

John Byrns

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

[Iain Churches[_2_]]

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

Ian (wondering in passing what a pad is...but don't worry, I'll look it
up)

It's an attenuator.
I can tell you of its origin. In the days of acoustic recording,
the recording phonograph was placed in front of the orchestra
with the horn pointing forwards. Because of the somewhat
limited dynamic of the acoustic recording chain, the
loud passages need to be attenuated. The engineer did this
by carefully pushing a ball of angora wood (known as
"the pad") into the mouth of the horn, and then gradually
pulling it out when the loud passage was over.

As Sir Michael Caine might say:
"Not a lot of people know that!"

Iain

[Arny Krueger]

"Eeyore" wrote in
message
"Tynan AgviÐr" wrote:

Ian Thompson-Bell wrote
Tynan AgviÐr wrote:

As far as layout goes, and features, the Wendt X4/x5
is nearly perfect. Unfortunately, it sounds like hot
ass. I of course know that the actual layout on the
requested mixer could not be anything like that, but
the features are spot-on. (I dont need the ENG port
though)

http://www.wendtinc.net/x4specs.pdf

http://www.wendtinc.net/x4specs.htm


Doesn't seem to mention the gain provided.


Ian, i meant features, Sir. The Features are pretty much
what I would want.

So really very straighforward.

Only, imagine what a 1:1 technical implementation in tubes would look like!

IOW, replace the IC op amps with comparable tube op amps, but use the same
gain staging, equalization, controls, etc.

(1) It would a lot larger.
(2) It would be a lot heavier.
(3) It would use a lot more power.

For a moment I thought of an implementation based on the subminiature
wire-in tubes that I worked with in the Army back in the 60s. But, that
would be way over the head of your average tubie. And, it would still be far
larger, gobble power, and literally cook.

[Arny Krueger]

"Ian Iveson" wrote in
message
.uk
John wrote:

...
Both the line amplifier and the headphone amplifier are
push pull
circuits. The microphone amplifiers are "SE", as 6 push
pull microphone
amplifiers seemed a bit much for a portable mixer.
...

For what reasons do you perceive PP to be preferable in
this application?

Low distortion, redundancy and therefore reliability.

In particular, why, after converting from balanced to SE,
you decided on PP for the output stages?

P-P gives you more dynamic range into real-world low impedance (5k-10k)
loads.