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Active Crossover

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Anonymous
June 29, 2005 2:17:47 PM

Archived from groups: rec.audio.pro (More info?)

Anyone know or can recommend a 3-way active (electronic) tube crossover at
least 3rd order? Thank you.
Cordially,
west

More about : active crossover

Anonymous
June 29, 2005 2:17:48 PM

Archived from groups: rec.audio.pro (More info?)

In article <fzuwe.190106$w15.130656@tornado.tampabay.rr.com> westley@Tampabay.rr.com writes:

> Anyone know or can recommend a 3-way active (electronic) tube crossover at
> least 3rd order?

Tube crossover? I haven't heard of one, but ask in the tweak audio
newsgroups, not rec.audio.pro. Somebody's bound to have been nutty
enough to make one.

And please don't cross-post your question here. We don't need another
tube vs. solid state discussion.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
June 29, 2005 2:17:48 PM

Archived from groups: rec.audio.pro (More info?)

"west" <westley@Tampabay.rr.com> wrote in message
news:fzuwe.190106$w15.130656@tornado.tampabay.rr.com

> Anyone know or can recommend a 3-way active (electronic)
tube
> crossover at least 3rd order? Thank you.

"know of":

http://www.marchandelec.com/xm126.html
Related resources
Anonymous
June 29, 2005 2:23:21 PM

Archived from groups: rec.audio.pro (More info?)

west <westley@Tampabay.rr.com> wrote:
>Anyone know or can recommend a 3-way active (electronic) tube crossover at
>least 3rd order? Thank you.

No, it would be enormous if you did it active.

You might be able to chain several Krohn-Hite filter modules together
to increase the slope, but it's going to weigh a ton and probably take
up more space than the amp rack.

Why do you want to do this? Active filters and tubes are usually a very
bad combination, even with wideband video pentodes.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 29, 2005 2:39:59 PM

Archived from groups: rec.audio.pro (More info?)

In article <znr1120047168k@trad>, Mike Rivers <mrivers@d-and-d.com> wrote:
>In article <fzuwe.190106$w15.130656@tornado.tampabay.rr.com> westley@Tampabay.rr.com writes:
>
>> Anyone know or can recommend a 3-way active (electronic) tube crossover at
>> least 3rd order?
>
>Tube crossover? I haven't heard of one, but ask in the tweak audio
>newsgroups, not rec.audio.pro. Somebody's bound to have been nutty
>enough to make one.

Heathkit made one. Actually, a bunch of folks have made them, using
passive filters. All the ones I have seen, though, were only 6 dB/octave.
And kind of noisy.

If you want sharper slopes, you're looking at instrumentation filters
like Krohn-Hites.

>And please don't cross-post your question here. We don't need another
>tube vs. solid state discussion.

Tubes are no good. Solid state electronics are no good either. Only
live music is any good at all.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 29, 2005 2:44:16 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D 9ubrv$11b$1@panix2.panix.com

> Tubes are no good. Solid state electronics are no good
> either. Only live music is any good at all.

Now, if we could get live musicians to work for the price of
playback electronics...
Anonymous
June 29, 2005 8:27:52 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D 9ubrv$11b$1@panix2.panix.com...
> In article <znr1120047168k@trad>, Mike Rivers <mrivers@d-and-d.com> wrote:
> >In article <fzuwe.190106$w15.130656@tornado.tampabay.rr.com>
westley@Tampabay.rr.com writes:
> >
> >> Anyone know or can recommend a 3-way active (electronic) tube crossover
at
> >> least 3rd order?
> Heathkit made one. Actually, a bunch of folks have made them, using
> passive filters. All the ones I have seen, though, were only 6 dB/octave.
> And kind of noisy.
>
> If you want sharper slopes, you're looking at instrumentation filters
> like Krohn-Hites.

Marchand Electronics (www.marchandelec.com) sells the XM126, which can be
configured as a 2-, 3- or 4-way crossover, 24dB/octave (4th order). It's
available as a kit if you like. Convenience factor isn't huge: crossover
frequencies are selected by plugging in different passive-component boards.
It's also unbalanced I/O, which may or may not be important to the poster.
Looks like a decent design, though, and Marchand's reputation for electronic
crossovers is good.

Peace,
Paul
Anonymous
June 29, 2005 8:41:50 PM

Archived from groups: rec.audio.pro (More info?)

In article <MLSdnX1MY_pcLl_fRVn-ig@comcast.com> arnyk@hotpop.com writes:

> Now, if we could get live musicians to work for the price of
> playback electronics...

Unfortunately, some do. Or for less.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
June 30, 2005 1:10:45 AM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
>Ohhh - talking of which you'll easily get an open loop gain of around
>4000 with a transistor operating off 250V. It's kinda necessary to use
>feedback to tame the gain.

This is a major irritation to my mind, and you can hardly even _get_
small signal semis at that voltage. On Semiconductor makes a nice line
of bipolars intended for CRT drive, but they aren't exactly selected
for precise beta.

>Reminds me, I once substituted a 2N3055 for a BC109 once in a pre-amp
>'just to see'. It worked.

I saw some folks who made a preamp for moving coil phono cartridges,
who used the 2N3055 as a front end, because the large area allowed them
to better match the very low output impedance of the cartridge. As I
recall the noise numbers weren't all that great, but they were better
than some circuits using low noise semis.

>Curiously, despite what I ( and indeed one of my colleagues ) had
>previously imagined to be the case, I came across about a discussion
>about toob linearity in r.a.t probably and to my surprise when comparing
>an EF86 to an ECC83 for example, the load line on the triode was
>significantly more linear.

Why does this surprise you? Pentodes are designed for gain rather than
linearity. You want serious linearity, drop the ECC83 entirely and go
with a frame grid triode. You want a lot of gain in a small footprint
for cheap, you go 6AU6 and try to ignore the noise. And don't clip it
whatever you do... 6AU6 clipping behaviour is no fun, whereas most triode
circuits clip less obnoxiously.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 30, 2005 2:33:36 AM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> west <westley@Tampabay.rr.com> wrote:
> >Anyone know or can recommend a 3-way active (electronic) tube crossover at
> >least 3rd order? Thank you.
>
> No, it would be enormous if you did it active.
>
> You might be able to chain several Krohn-Hite filter modules together
> to increase the slope, but it's going to weigh a ton and probably take
> up more space than the amp rack.
>
> Why do you want to do this? Active filters and tubes are usually a very
> bad combination, even with wideband video pentodes.

One can only assume he heard the " toobs are bettter " nonsence and swallowed
it.

Graham
Anonymous
June 30, 2005 5:47:02 AM

Archived from groups: rec.audio.pro (More info?)

On Thu, 30 Jun 2005 00:31:27 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

>Curiously, despite what I ( and indeed one of my colleagues ) had
>previously imagined to be the case, I came across about a discussion
>about toob linearity in r.a.t probably and to my surprise when comparing
>an EF86 to an ECC83 for example, the load line on the triode was
>significantly more linear.

Perhaps surprisingly, an ECC83 is one of the most linear
devices ever made. And over *very* large parts of the
transfer curve.

Valves have a bad rep these days because of unsavory
associations, but the devices themselves can be amazingly
linear. Implementation can be expensive and impedances
limit compatibility, but for linearity, they're tough
to beat.

Chris Hornbeck
"Chief Assistant to the Assistant Chief" -F&S
Anonymous
June 30, 2005 5:47:03 AM

Archived from groups: rec.audio.pro (More info?)

"Chris Hornbeck" <chrishornbeckremovethis@att.net> wrote in
message news:k8j6c1t3ijemp2ieddn21da62p4kuhom1l@4ax.com
> On Thu, 30 Jun 2005 00:31:27 +0100, Pooh Bear
> <rabbitsfriendsandrelations@hotmail.com> wrote:
>
>> Curiously, despite what I ( and indeed one of my
colleagues )
>> had previously imagined to be the case, I came across
about a
>> discussion about toob linearity in r.a.t probably and to
my
>> surprise when comparing an EF86 to an ECC83 for example,
the
>> load line on the triode was significantly more linear.
>
> Perhaps surprisingly, an ECC83 is one of the most linear
> devices ever made. And over *very* large parts of the
> transfer curve.
>
> Valves have a bad rep these days because of unsavory
> associations, but the devices themselves can be amazingly
> linear. Implementation can be expensive and impedances
> limit compatibility, but for linearity, they're tough
> to beat.

Triodes are relatively linear as devices because they have
a great deal of local feedback, built-in. As a consequence,
they have relatively low amounts of gain.

From the standpoint of building a working amplifier that is
highly linear, both the gain and the linearity need to be
considered. No way are small amounts of amplification more
desirable when they have less linearity considering the
relatively low amount of gain that they have.
Anonymous
June 30, 2005 6:27:06 AM

Archived from groups: rec.audio.pro (More info?)

On Wed, 29 Jun 2005 21:54:16 -0400, "Arny Krueger" <arnyk@hotpop.com>
wrote:

> Triodes are relatively linear as devices because they have
>a great deal of local feedback, built-in. As a consequence,
>they have relatively low amounts of gain.

I would say instead that triodes are *amazingly* linear
devices compared to conventional modern devices. The
concept of "local feedback" gets a lot of newsgroup ink
these days, but still seems totally wacky to me.

Perhaps you're the guy to convince me otherwise...

>From the standpoint of building a working amplifier that is
>highly linear, both the gain and the linearity need to be
>considered. No way are small amounts of amplification more
>desirable when they have less linearity considering the
>relatively low amount of gain that they have.

Good point, and perfectly appropriate for input bandwidth
limited situations. We need to include both elements, just
as we would for an A/D conversion or a sample rate reduction.
Often (usually?) forgotten real-world.

Thanks, as always,

Chris Hornbeck
"Chief Assistant to the Assistant Chief" -F&S
Anonymous
June 30, 2005 10:21:55 AM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D 9vgql$1di$1@panix2.panix.com...

> >Curiously, despite what I ( and indeed one of my colleagues ) had
> >previously imagined to be the case, I came across about a discussion
> >about toob linearity in r.a.t probably and to my surprise when comparing
> >an EF86 to an ECC83 for example, the load line on the triode was
> >significantly more linear.
>
> Why does this surprise you? Pentodes are designed for gain rather than
> linearity. You want serious linearity, drop the ECC83 entirely and go
> with a frame grid triode.

Is the 6SN7 a frame-grid triode? Cuz that's about the most linear device
without feedback that I've found.

There's a problem using triodes for electronic crossovers, though; you can't
just plug in numbers from the Active Filter Cookbook the way you can with
opamps. The cookbook numbers assume an active device (or block) with very
high open-loop gain, which triodes -- especially the really linear ones like
the 6SN7 -- ain't got. The filters' curves come out wrong if you use the
cookbook numbers on, say, a 6SN7 cathode follower, and to get them right you
actually have to do some work.

Peace,
Paul
Anonymous
June 30, 2005 10:28:43 AM

Archived from groups: rec.audio.pro (More info?)

"Chris Hornbeck" <chrishornbeckremovethis@att.net> wrote in
message news:9il6c1tuc3qm4mgq3j473kpdc3kf4msan7@4ax.com

> On Wed, 29 Jun 2005 21:54:16 -0400, "Arny Krueger"
> <arnyk@hotpop.com> wrote:

>> Triodes are relatively linear as devices because they
have
>> a great deal of local feedback, built-in. As a
consequence,
>> they have relatively low amounts of gain.

> I would say instead that triodes are *amazingly* linear
> devices compared to conventional modern devices.

With all that local feedback, they can hardly miss.

However, if you properly design a transistor circuit with
enough local or loop feedback to reduce its gain to triode
levels, it can be even more linear than the triode.

>The concept of "local feedback" gets a lot of newsgroup
ink
> these days, but still seems totally wacky to me.

There's nothing wacky about local feedback at all. It is
relatively simple to implement, and it pretty much works as
designed.

> Perhaps you're the guy to convince me otherwise...

Convincing people about the validity of basic electronics is
not what I do if I can avoid it.

Here's a fairly sane article about tubes and feedback, local
and otherwise:

http://www.normankoren.com/Audio/FeedbackFidelity.html

>> From the standpoint of building a working amplifier that
is
>> highly linear, both the gain and the linearity need to be
>> considered. No way are small amounts of amplification
more
>> desirable when they have less linearity considering the
>> relatively low amount of gain that they have.

> Good point, and perfectly appropriate for input bandwidth
> limited situations. We need to include both elements, just
> as we would for an A/D conversion or a sample rate
reduction.
> Often (usually?) forgotten real-world.

There is one other figure of merit in a design, and that's
the degree to which available power supply voltages are
exploited to produce relatively high output voltages and
improve dynamic range. Because of their relatively high
saturation voltages, tubes are not efficient users of
available power supply voltages.
Anonymous
June 30, 2005 11:18:34 AM

Archived from groups: rec.audio.pro (More info?)

"west" <westley@Tampabay.rr.com> wrote in message
news:fzuwe.190106$w15.130656@tornado.tampabay.rr.com...
> Anyone know or can recommend a 3-way active (electronic) tube crossover at
> least 3rd order? Thank you.
> Cordially,
> west
>
>

Not a tube type, but I can heartily recommend the Behringer DCX-2496, which
is a crossover that possessess several major slope types in just about any
order you can imagine, in addition to dynamic compressors, limiters and EQs,
all with the advantage of save and restore settings from memory and PCMCIA
card reader.
I added one to the big house system in December and oh, what an improvement
over my Linkwitz-Riley that I built in 1983.


--
Best Regards,

Mark A. Weiss, P.E.
www.mwcomms.com
-
Anonymous
June 30, 2005 12:44:19 PM

Archived from groups: rec.audio.pro (More info?)

Paul Stamler <pstamlerhell@pobox.com> wrote:
>"Scott Dorsey" <kludge@panix.com> wrote in message
>
>> >Curiously, despite what I ( and indeed one of my colleagues ) had
>> >previously imagined to be the case, I came across about a discussion
>> >about toob linearity in r.a.t probably and to my surprise when comparing
>> >an EF86 to an ECC83 for example, the load line on the triode was
>> >significantly more linear.
>>
>> Why does this surprise you? Pentodes are designed for gain rather than
>> linearity. You want serious linearity, drop the ECC83 entirely and go
>> with a frame grid triode.
>
>Is the 6SN7 a frame-grid triode? Cuz that's about the most linear device
>without feedback that I've found.

No, it predates all the frame grid stuff by many years. It is a really
linear device, though. The problem is that the gain is low.

>There's a problem using triodes for electronic crossovers, though; you can't
>just plug in numbers from the Active Filter Cookbook the way you can with
>opamps. The cookbook numbers assume an active device (or block) with very
>high open-loop gain, which triodes -- especially the really linear ones like
>the 6SN7 -- ain't got. The filters' curves come out wrong if you use the
>cookbook numbers on, say, a 6SN7 cathode follower, and to get them right you
>actually have to do some work.

Every attempt I have seen to build active filters with tube op-amp networks
has turned out badly, usually due to slew rate limitations. But there
is no reason you can't just build a bunch of passive RLC networks, with
tube gain stages between them. Other than S/N of course.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 30, 2005 3:52:42 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey <kludge@panix.com> wrote:


> I saw some folks who made a preamp for moving coil phono cartridges,
> who used the 2N3055 as a front end, because the large area allowed them
> to better match the very low output impedance of the cartridge. As I
> recall the noise numbers weren't all that great, but they were better
> than some circuits using low noise semis.

I seem to remember a circuit which used several printer-hammer driver
transistors in parallel to achieve low input impedance (they may have
been from the ZTX series).

It was in the [UK] Wireless World (or Electronics World?) about 10 or 15
years ago and was intended as a moving coil cartridge pre-amp without a
transformer. I think a pretty good noise figure was claimed.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
Anonymous
June 30, 2005 7:45:16 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D a0pf3$hu6$1@panix2.panix.com...

> Every attempt I have seen to build active filters with tube op-amp
networks
> has turned out badly, usually due to slew rate limitations. But there
> is no reason you can't just build a bunch of passive RLC networks, with
> tube gain stages between them. Other than S/N of course.

S/N could probably be made acceptable. What's tough is that at impedances
high enough for tubes to be comfortable with, the inductors need to be very
big and expensive. Unless you transformer-couple the tubes and make the
impedances low, but then you're paying for expensive transformers instead of
expensive inductors.

Peace,
Paul
Anonymous
June 30, 2005 7:45:17 PM

Archived from groups: rec.audio.pro (More info?)

Paul Stamler <pstamlerhell@pobox.com> wrote:
>"Scott Dorsey" <kludge@panix.com> wrote in message
>
>> Every attempt I have seen to build active filters with tube op-amp
>networks
>> has turned out badly, usually due to slew rate limitations. But there
>> is no reason you can't just build a bunch of passive RLC networks, with
>> tube gain stages between them. Other than S/N of course.
>
>S/N could probably be made acceptable. What's tough is that at impedances
>high enough for tubes to be comfortable with, the inductors need to be very
>big and expensive. Unless you transformer-couple the tubes and make the
>impedances low, but then you're paying for expensive transformers instead of
>expensive inductors.

Yes, absolutely. And you also now wind up having to deal with inductor
nonlinearity and non-ideal overload behaviours.

I will say that I have a source now for large-value audio inductors at
reasonable prices, though.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 30, 2005 7:45:17 PM

Archived from groups: rec.audio.pro (More info?)

"Paul Stamler" <pstamlerhell@pobox.com> wrote in message
news:gsUwe.373502$cg1.212278@bgtnsc04-news.ops.worldnet.att.net
> "Scott Dorsey" <kludge@panix.com> wrote in message
> news:D a0pf3$hu6$1@panix2.panix.com...
>
>> Every attempt I have seen to build active filters with
tube
>> op-amp networks has turned out badly, usually due to slew
>> rate limitations. But there is no reason you can't just
>> build a bunch of passive RLC networks, with tube gain
stages
>> between them. Other than S/N of course.
>
> S/N could probably be made acceptable. What's tough is
that at
> impedances high enough for tubes to be comfortable with,
the
> inductors need to be very big and expensive. Unless you
> transformer-couple the tubes and make the impedances low,
but
> then you're paying for expensive transformers instead of
> expensive inductors.

What would stop one from doing state-variable filters with
tube op amps, patterned ofter the Philbrick modules of the
days of tubes?
Anonymous
June 30, 2005 7:45:18 PM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger <arnyk@hotpop.com> wrote:
>
>What would stop one from doing state-variable filters with
>tube op amps, patterned ofter the Philbrick modules of the
>days of tubes?

Slew rate and bandwidth. Those Philbrick and HP tube op-amps
really did not have the bandwidth for anything approaching audio.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 30, 2005 7:45:19 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D a1bsl$rv1$1@panix2.panix.com

> Arny Krueger <arnyk@hotpop.com> wrote:

>> What would stop one from doing state-variable filters
with
>> tube op amps, patterned ofter the Philbrick modules of
the
>> days of tubes?

> Slew rate and bandwidth. Those Philbrick and HP tube
op-amps
> really did not have the bandwidth for anything approaching
> audio. --scott

I didn't know that tubed op-amps were that bad.
Anonymous
June 30, 2005 7:45:20 PM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger <arnyk@hotpop.com> wrote:
>"Scott Dorsey" <kludge@panix.com> wrote in message
>news:D a1bsl$rv1$1@panix2.panix.com
>
>> Arny Krueger <arnyk@hotpop.com> wrote:
>
>>> What would stop one from doing state-variable filters
>with
>>> tube op amps, patterned ofter the Philbrick modules of
>the
>>> days of tubes?
>
>> Slew rate and bandwidth. Those Philbrick and HP tube
>op-amps
>> really did not have the bandwidth for anything approaching
>> audio. --scott
>
>I didn't know that tubed op-amps were that bad.


Bob Pease has data sheets!

http://www.national.com/rap/images/BBB1.gif
http://www.national.com/rap/images/BBB2.jpg

This one actually isn't bad, with an open loop DC gain of 15,000
and a gain-bandwidth product of 100 KHz. That's about a tenth the
speed of a 741.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 30, 2005 9:52:08 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D a1hfu$t7k$1@panix2.panix.com

> Arny Krueger <arnyk@hotpop.com> wrote:
>> "Scott Dorsey" <kludge@panix.com> wrote in message

>> news:D a1bsl$rv1$1@panix2.panix.com
>>
>>> Arny Krueger <arnyk@hotpop.com> wrote:

>>>> What would stop one from doing state-variable filters
with
>>>> tube op amps, patterned ofter the Philbrick modules of
the
>>>> days of tubes?

>>> Slew rate and bandwidth. Those Philbrick and HP tube
op-amps
>>> really did not have the bandwidth for anything
approaching
>>> audio. --scott
>>
>> I didn't know that tubed op-amps were that bad.

> Bob Pease has data sheets!

> http://www.national.com/rap/images/BBB1.gif
> http://www.national.com/rap/images/BBB2.jpg

> This one actually isn't bad, with an open loop DC gain of
> 15,000 and a gain-bandwidth product of 100 KHz. That's
about
> a tenth the speed of a 741.

When I was an undergraduate back in the 60s, I did some time
*programming* analog computers. My recollection is the
Philbrick parts posted at
http://www.national.com/rap/vacuumtubes.html were
bottom-of-the barrel parts.

The sort of vacuum tube op amps I'm thinking of were more on
the order of this one:

http://ed-thelen.org/dc_amp.gif

There's really no excuse for vacuum tube amplifiers to be
terribly slow, after all Tektronics made some pretty fast
'scopes out of bottles....
Anonymous
June 30, 2005 11:54:31 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D a1bsl$rv1$1@panix2.panix.com...
> Arny Krueger <arnyk@hotpop.com> wrote:
> >
> >What would stop one from doing state-variable filters with
> >tube op amps, patterned ofter the Philbrick modules of the
> >days of tubes?
>
> Slew rate and bandwidth. Those Philbrick and HP tube op-amps
> really did not have the bandwidth for anything approaching audio.

Well, one isn't limited to those designs. Fred Forssell designed tube-based
op-amps that had a lot better audio specs. The maximum open-loop gain was
still a lot less than with IC op-amps, though, so one still has to do some
jiggering to make the filters come out right. It is, however, a lot more
feasible than with a simple cathode follower.

Also, you're looking at eight tubes for a 2-way 4th-order crossover, and
you're starting to generate some serious heat there.

Peace,
Paul
Anonymous
July 1, 2005 1:42:46 AM

Archived from groups: rec.audio.pro (More info?)

On Thu, 30 Jun 2005 06:28:43 -0400, "Arny Krueger" <arnyk@hotpop.com>
wrote:

>With all that local feedback, they can hardly miss.
>
>However, if you properly design a transistor circuit with
>enough local or loop feedback to reduce its gain to triode
>levels, it can be even more linear than the triode.
>
>>The concept of "local feedback" gets a lot of newsgroup
>ink
>> these days, but still seems totally wacky to me.
>
>There's nothing wacky about local feedback at all. It is
>relatively simple to implement, and it pretty much works as
>designed.

>http://www.normankoren.com/Audio/FeedbackFidelity.html

Oh, OK. I thought you meant the "internal feedback"
concept that's going around on rec.audio.tubes.

So, why must a triode design inherently have more local
feedback than any other?

Chris Hornbeck
"Chief Assistant to the Assistant Chief" -F&S
Anonymous
July 1, 2005 1:42:47 AM

Archived from groups: rec.audio.pro (More info?)

"Chris Hornbeck" <chrishornbeckremovethis@att.net> wrote in
message news:D jp8c199vme0c56dqa1cl9t5tf6fed00lb@4ax.com
> On Thu, 30 Jun 2005 06:28:43 -0400, "Arny Krueger"
> <arnyk@hotpop.com> wrote:
>
>> With all that local feedback, they can hardly miss.
>>
>> However, if you properly design a transistor circuit with
>> enough local or loop feedback to reduce its gain to
triode
>> levels, it can be even more linear than the triode.
>>
>>> The concept of "local feedback" gets a lot of newsgroup
>> ink
>>> these days, but still seems totally wacky to me.
>>
>> There's nothing wacky about local feedback at all. It is
>> relatively simple to implement, and it pretty much works
as
>> designed.
>
>> http://www.normankoren.com/Audio/FeedbackFidelity.html

> Oh, OK. I thought you meant the "internal feedback"
> concept that's going around on rec.audio.tubes.

> So, why must a triode design inherently have more local
> feedback than any other?

It has to do with the space charge around the plate feeding
signal back to the region around the grid. They invented
tetrodes and pentodes to keep that from happening.
Anonymous
July 1, 2005 1:42:47 AM

Archived from groups: rec.audio.pro (More info?)

In article <djp8c199vme0c56dqa1cl9t5tf6fed00lb@4ax.com> chrishornbeckremovethis@att.net writes:

> >There's nothing wacky about local feedback at all. It is
> >relatively simple to implement, and it pretty much works as
> >designed.

> Oh, OK. I thought you meant the "internal feedback"
> concept that's going around on rec.audio.tubes.
>
> So, why must a triode design inherently have more local
> feedback than any other?

I was wondering about that term "local feedback" too. It sounds like
one of those terms coined by the same folks who talk about LDC and
SDC. Is it some hip name for not bypassing the cathode resistor?



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
July 1, 2005 3:15:08 AM

Archived from groups: rec.audio.pro (More info?)

On Thu, 30 Jun 2005 18:51:01 -0400, "Arny Krueger" <arnyk@hotpop.com>
wrote:

>> So, why must a triode design inherently have more local
>> feedback than any other?
>
>It has to do with the space charge around the plate feeding
>signal back to the region around the grid. They invented
>tetrodes and pentodes to keep that from happening.

Say it ain't so, Arny. Just say no to the Dark Side. Don't
let the pod people get ya, please.

Stay strong,

Chris Hornbeck
"Chief Assistant to the Assistant Chief" -F&S
Anonymous
July 1, 2005 5:14:41 AM

Archived from groups: rec.audio.pro (More info?)

On 30 Jun 2005 20:58:00 -0400, mrivers@d-and-d.com (Mike Rivers)
wrote:

>> So, why must a triode design inherently have more local
>> feedback than any other?
>
>I was wondering about that term "local feedback" too. It sounds like
>one of those terms coined by the same folks who talk about LDC and
>SDC. Is it some hip name for not bypassing the cathode resistor?

I'm halfway trying to tease Arny into making the effort to
convince me about the "internal feedback" model of active
(transconductance) devices, which I'm too much of an old grump
to accept casually, and halfway making a serious argument
about gain-staging within feedback loops.

But to answer your question, yeah, pretty much (to my point
of view), and no (to the internal feedback POV).

Much clearer now, isn't it? Sorry to drag this peripheral
argument in here. Spank me!

Thanks, as always,

Chris Hornbeck
"taking the cure, so I can be quiet,
wherever I want, so leave me alone.
You outta be proud, that I'm getting
good marks." -Elliott Smith
Anonymous
July 1, 2005 6:26:47 AM

Archived from groups: rec.audio.pro (More info?)

Adrian Tuddenham wrote:

> Scott Dorsey <kludge@panix.com> wrote:
>
> > I saw some folks who made a preamp for moving coil phono cartridges,
> > who used the 2N3055 as a front end, because the large area allowed them
> > to better match the very low output impedance of the cartridge. As I
> > recall the noise numbers weren't all that great, but they were better
> > than some circuits using low noise semis.
>
> I seem to remember a circuit which used several printer-hammer driver
> transistors in parallel to achieve low input impedance (they may have
> been from the ZTX series).
>
> It was in the [UK] Wireless World (or Electronics World?) about 10 or 15
> years ago and was intended as a moving coil cartridge pre-amp without a
> transformer. I think a pretty good noise figure was claimed.

If you want a decent noise figure at low imedance you need a device with low
intrinsic resistance. That means a power / switching type device may be
suitable if you don't have access to a specialist part.

2N4401 and 3s did quite well in that respect. The Japanese devices intended
for the job are better though and also have a decent hfe.

Graham
Anonymous
July 1, 2005 6:26:48 AM

Archived from groups: rec.audio.pro (More info?)

On Fri, 01 Jul 2005 02:26:47 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

>If you want a decent noise figure at low imedance you need a device with low
>intrinsic resistance.

Perzactly. Impedance matching is a red herring here. The input
device's intrinsic resistance (reciprocal of transconductance)
determines (thermal) noise voltage.

Noise factor and noise figure have well defined meanings in
related fields, and shouldn't be mis-used casually in our work.
What we care about is best defined as noise voltage in relation
to signal voltage.

Chris Hornbeck
"taking the cure, so I can be quiet,
wherever I want, so leave me alone.
You outta be proud, that I'm getting
good marks." -Elliott Smith
Anonymous
July 1, 2005 6:30:13 AM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger wrote:

> "Chris Hornbeck" <chrishornbeckremovethis@att.net> wrote in
> message news:D jp8c199vme0c56dqa1cl9t5tf6fed00lb@4ax.com
> > On Thu, 30 Jun 2005 06:28:43 -0400, "Arny Krueger"
> > <arnyk@hotpop.com> wrote:
> >
> >> With all that local feedback, they can hardly miss.
> >>
> >> However, if you properly design a transistor circuit with
> >> enough local or loop feedback to reduce its gain to
> triode
> >> levels, it can be even more linear than the triode.
> >>
> >>> The concept of "local feedback" gets a lot of newsgroup
> >> ink
> >>> these days, but still seems totally wacky to me.
> >>
> >> There's nothing wacky about local feedback at all. It is
> >> relatively simple to implement, and it pretty much works
> as
> >> designed.
> >
> >> http://www.normankoren.com/Audio/FeedbackFidelity.html
>
> > Oh, OK. I thought you meant the "internal feedback"
> > concept that's going around on rec.audio.tubes.
>
> > So, why must a triode design inherently have more local
> > feedback than any other?
>
> It has to do with the space charge around the plate feeding
> signal back to the region around the grid. They invented
> tetrodes and pentodes to keep that from happening.

Indeed !

So-called screen or suppressor grids.

Graham
Anonymous
July 1, 2005 6:30:14 AM

Archived from groups: rec.audio.pro (More info?)

On Fri, 01 Jul 2005 02:30:13 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

>> It has to do with the space charge around the plate feeding
>> signal back to the region around the grid. They invented
>> tetrodes and pentodes to keep that from happening.
>
>Indeed !
>
>So-called screen or suppressor grids.

Well, screen (G2) and suppressor (G3) grids are different critters,
doing very different gigs.

But that ain't my gripe with the whole argument. And I still
feel uncomfortable airing it here. Ain't nobody's bidness...
etc.

Thanks,

Chris Hornbeck
"taking the cure, so I can be quiet,
wherever I want, so leave me alone.
You outta be proud, that I'm getting
good marks." -Elliott Smith
Anonymous
July 1, 2005 10:21:48 AM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1120170690k@trad...

> I was wondering about that term "local feedback" too. It sounds like
> one of those terms coined by the same folks who talk about LDC and
> SDC. Is it some hip name for not bypassing the cathode resistor?

In standard parlance, yes. I'd call the single-stage "anode follower"
(resistor from the output side of the plate coupling capacitor back to the
grid, another resistor from the grid to the input) global feedback even
though it's around a single stage, whereas an unbypassed cathode resistor is
local.

Peace,
Paul
Anonymous
July 1, 2005 10:24:27 AM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:l6GdndcY4L8V9FnfRVn-1A@comcast.com...

> >>> Slew rate and bandwidth. Those Philbrick and HP tube
> op-amps
> >>> really did not have the bandwidth for anything
> approaching
> >>> audio. --scott
>
> When I was an undergraduate back in the 60s, I did some time
> *programming* analog computers. My recollection is the
> Philbrick parts posted at
> http://www.national.com/rap/vacuumtubes.html were
> bottom-of-the barrel parts.
>
> The sort of vacuum tube op amps I'm thinking of were more on
> the order of this one:
>
> http://ed-thelen.org/dc_amp.gif
>
> There's really no excuse for vacuum tube amplifiers to be
> terribly slow, after all Tektronics made some pretty fast
> 'scopes out of bottles....

Right, but the Philbrock jobs were optimized for DC and low-frequency
operation, not audio. As you say, they were for analog computing, and that
usually didn't involve much in the way of high frequencies.

Peace,
Paul0
Anonymous
July 1, 2005 10:51:27 AM

Archived from groups: rec.audio.pro (More info?)

Chris Hornbeck wrote:

> On Fri, 01 Jul 2005 02:26:47 +0100, Pooh Bear
> <rabbitsfriendsandrelations@hotmail.com> wrote:
>
> >If you want a decent noise figure at low imedance you need a device with low
> >intrinsic resistance.
>
> Perzactly. Impedance matching is a red herring here. The input
> device's intrinsic resistance (reciprocal of transconductance)
> determines (thermal) noise voltage.
>
> Noise factor and noise figure have well defined meanings in
> related fields, and shouldn't be mis-used casually in our work.
> What we care about is best defined as noise voltage in relation
> to signal voltage.

You are indeed 100% correct. I find it mildy amusing ( under recent circumstances
) that your post on the matter came immediately after my comment to Adrian.

You should pop over to s.e.d and see what nonsence he's been posting there (
along with a couple of others ) about decibels.

See the thread - 'the truth about decibels'.

Graham
Anonymous
July 1, 2005 11:15:03 AM

Archived from groups: rec.audio.pro (More info?)

"Paul Stamler" <pstamlerhell@pobox.com> wrote in message
news:vk5xe.1058836$w62.996645@bgtnsc05-news.ops.worldnet.att.net
> "Arny Krueger" <arnyk@hotpop.com> wrote in message
> news:l6GdndcY4L8V9FnfRVn-1A@comcast.com...
>
>>>>> Slew rate and bandwidth. Those Philbrick and HP tube
>> op-amps
>>>>> really did not have the bandwidth for anything
>> approaching
>>>>> audio. --scott
>>
>> When I was an undergraduate back in the 60s, I did some
time
>> *programming* analog computers. My recollection is the
>> Philbrick parts posted at
>> http://www.national.com/rap/vacuumtubes.html were
>> bottom-of-the barrel parts.

>> The sort of vacuum tube op amps I'm thinking of were more
on
>> the order of this one:

>> http://ed-thelen.org/dc_amp.gif

This op amp was part of the analog flight control computer
for a Nike system. This was one of those time-critical
applications. It looks more like what I was used to seeing
in higher-end analog computers (EIA, for example).

>> There's really no excuse for vacuum tube amplifiers to be
>> terribly slow, after all Tektronics made some pretty fast
>> 'scopes out of bottles....

> Right, but the Philbrick jobs were optimized for DC and
> low-frequency operation, not audio. As you say, they were
for
> analog computing, and that usually didn't involve much in
the
> way of high frequencies.

The thing is, that speed was often of the essence in analog
computing. Many problems they were used for involve
optimization of parameters using large sets of
systematically-changed variables, intelligent searching
techniques, or Monte Carlo techniques.

I recall that the op amps in the EIA 680 that I worked with
later on, was speced to be something like 1% accurate while
reproducing a 10 KHz sine wave at 10 volt p-p. IOW, it was
0.1 dB down at 10 KHz while putting out maximum rated
output, so it had something like 50 KHz or better bandwidth.
Anonymous
July 1, 2005 11:19:19 AM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1120170690k@trad
> In article <djp8c199vme0c56dqa1cl9t5tf6fed00lb@4ax.com>
> chrishornbeckremovethis@att.net writes:
>
>>> There's nothing wacky about local feedback at all. It is
>>> relatively simple to implement, and it pretty much works
as
>>> designed.
>
>> Oh, OK. I thought you meant the "internal feedback"
>> concept that's going around on rec.audio.tubes.
>>
>> So, why must a triode design inherently have more local
>> feedback than any other?

> I was wondering about that term "local feedback" too. It
sounds like
> one of those terms coined by the same folks who talk about
LDC and
> SDC. Is it some hip name for not bypassing the cathode
resistor?

Not bypassing the cathode resistor is one way to get local
feedback. Other techniques include a resistor from the plate
to the grid usually with a blocking capacitor, and cathode
windings on the output transformer.
Anonymous
July 1, 2005 12:20:01 PM

Archived from groups: rec.audio.pro (More info?)

Chris Hornbeck <chrishornbeckremovethis@att.net> wrote:
>On 30 Jun 2005 20:58:00 -0400, mrivers@d-and-d.com (Mike Rivers)
>wrote:
>
>>> So, why must a triode design inherently have more local
>>> feedback than any other?
>>
>>I was wondering about that term "local feedback" too. It sounds like
>>one of those terms coined by the same folks who talk about LDC and
>>SDC. Is it some hip name for not bypassing the cathode resistor?
>
>I'm halfway trying to tease Arny into making the effort to
>convince me about the "internal feedback" model of active
>(transconductance) devices, which I'm too much of an old grump
>to accept casually, and halfway making a serious argument
>about gain-staging within feedback loops.

I suppose you could think about any amplifier stage as being an amplifier
of infinite gain combined with degeneration. That's a useful thing from
the standpoint of theoretical modelling.

But, you can also think of a power supply as being a voltage source with
zero impedance in combination with a series resistor. But that's not
actually what's inside the box of my Sorenson here.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
July 1, 2005 1:05:17 PM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger <arnyk@hotpop.com> wrote:
>
>The sort of vacuum tube op amps I'm thinking of were more on
>the order of this one:
>
>http://ed-thelen.org/dc_amp.gif

Man, that thing has a HUGE number of tubes in it!

>There's really no excuse for vacuum tube amplifiers to be
>terribly slow, after all Tektronics made some pretty fast
>'scopes out of bottles....

There is indeed: remember that you can either have gain or you can
have bandwidth, and the whole point of the op-amp is that you can
trade one for the other. If you want wide bandwidth at high gains,
you need a whole lot of open loop gain inside the box, and that
means a big box with a lot of tubes in it. And it means some drift
issues.

For most of the things op-amps got used for back then, drift was
critical. If you didn't want response down to DC, there were plenty
of other solutions that were easier or cheaper (and often involved
transformers).

Look at those 1.8M plate resistors! Yow! Gain at all cost, indeed.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
July 1, 2005 1:36:34 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D a3f2d$5la$1@panix2.panix.com
> Arny Krueger <arnyk@hotpop.com> wrote:
>>
>> The sort of vacuum tube op amps I'm thinking of were more
on
>> the order of this one:
>>
>> http://ed-thelen.org/dc_amp.gif
>
> Man, that thing has a HUGE number of tubes in it!
>
>> There's really no excuse for vacuum tube amplifiers to be
>> terribly slow, after all Tektronics made some pretty fast
>> 'scopes out of bottles....
>
> There is indeed: remember that you can either have gain or
you
> can have bandwidth, and the whole point of the op-amp is
that
> you can trade one for the other. If you want wide
bandwidth
> at high gains, you need a whole lot of open loop gain
inside
> the box, and that means a big box with a lot of tubes in
it.
> And it means some drift issues.
>
> For most of the things op-amps got used for back then,
drift
> was critical. If you didn't want response down to DC,
there
> were plenty of other solutions that were easier or cheaper
> (and often involved transformers).
>
> Look at those 1.8M plate resistors! Yow! Gain at all
cost,
> indeed. --scott

Look again - they 1.8 meggers are in series with the grids
and are bypassed. The plate resistors are 620K, 180K, and
240K. The 620K plate resistors for the input stage are a bit
misleading because there's 24K worth of local feedback.
Anonymous
July 1, 2005 1:41:11 PM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:


> You should pop over to s.e.d and see what nonsence he's been posting there (
> along with a couple of others ) about decibels.
>
> See the thread - 'the truth about decibels'.

....and make up you own mind about who said what.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
Anonymous
July 1, 2005 3:22:34 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D a3h8n$nhu$1@panix2.panix.com

> What is worse is that some of the finest tubes made are TV
and
> military designs that you can't give away today. Those
> Raytheon subminis have some of the best high-gain
> low-microphonic performance of anything around, and people
are
> using them as jewelry because there's no demand for them
for
> anything else.

My radars had literally 100's of 'em, all neatly wired to
carefully swaged silver-plated posts on FRP circuit boards,
clipped to heat sinks that were mounted on the back of the
cakepan-like chassis. I believe they were rated for 10,000
hour MTBF. My largest radar had over 400 of them, and it
dutifully went down about once every 24 hours. Do the math!

They subminis pretty well duplicated the common
signal-handling tubes of the day. There was one that was
12AX7-like, another that was 12AU7-like, others that were
like 6AU6s, and even a 6AL5 work-alike. The biggest
concentration of them in one chassis was a triple IF strip
with about 10 transformer IF stages per channel.

Perhaps the most impressive item in teh system was the
spectrum analyzer. Balanced mixers converted three adjoining
frequency ranges of the inbound signal to the same range of
intermediate frequencies which passed through three
identical sets of additional tuned circuits and rectifiers
to provide a fast-response spectrum analysis of the inbound
signal as the antenna rotated.
Anonymous
July 1, 2005 5:02:54 PM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger <arnyk@hotpop.com> wrote:
>
>Perhaps the most impressive item in teh system was the
>spectrum analyzer. Balanced mixers converted three adjoining
>frequency ranges of the inbound signal to the same range of
>intermediate frequencies which passed through three
>identical sets of additional tuned circuits and rectifiers
>to provide a fast-response spectrum analysis of the inbound
>signal as the antenna rotated.

AN/APR-6?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
July 1, 2005 7:48:51 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D a3svu$dfm$1@panix2.panix.com
> Arny Krueger <arnyk@hotpop.com> wrote:
>>
>> Perhaps the most impressive item in teh system was the
>> spectrum analyzer. Balanced mixers converted three
adjoining
>> frequency ranges of the inbound signal to the same range
of
>> intermediate frequencies which passed through three
>> identical sets of additional tuned circuits and
rectifiers
>> to provide a fast-response spectrum analysis of the
inbound
>> signal as the antenna rotated.
>
> AN/APR-6?
>

The AN/MPQ-34 had the spectrum analyzer, the AN/MPQ-39 had
over 400 subminiature tubes.
!