Matamp combo ...

A

Arfa Daily

Guest
Had one of these Orange clones on the bench today, and the bastard bit me.
Hard. A faulty EL34 in the output stage had blown the HT fuse, and left the
main smoothing caps fully charged at 630 volts. My own silly fault - I
should have checked. But then it occurred to me that 630 v is a stonking lot
of voltage to have applied to a panel mount screw-cap 20 mm fuseholder. I
checked the specs on a few, and they seem to only carry an AC rating, that
being 250 v. There's a lot of difference between the peak value of AC mains,
and 630 v DC, and I'm a bit surprised that the insulation stands up to it
ok. I suppose it must be ok because these things are quite old now.

I also thought that 630 v on the anode of a modern EL34 is pushing it a bit
as well. The data sheets say that the maximum is 800 volts, but I don't know
how many of today's offerings I would trust to not be flashing over at that
sort of level ...

Arfa
 
quote without comment...

http://www.rfcafe.com/references/popular-electronics/unpopular-electronics-aug-1959-popular-electronics.htm
 
"Arfa Daily"
I also thought that 630 v on the anode of a modern EL34 is pushing it a
bit as well. The data sheets say that the maximum is 800 volts, but I
don't know how many of today's offerings I would trust to not be flashing
over at that sort of level ...
Click to expand...

** EL34s and 6L6s are hardier than most people think and can stand very high
peak plate voltages when used in guitar amps.

A (4x EL34) 100W Marshall uses a B+ of about 475V and a screen supply that
is only a few volts less.

In normal operation, the plate voltage swings up to almost 900V and down to
about 75V during each cycle. However, in hard overdrive with a speaker
connected, something new happens and the peak plate voltage can reach 5kV.

Some amp makers( eg Music Man, Boogie, Peavey) include high voltage diode
stacks wired from plates to ground to clip these very high peaks values, but
Marshall do not.

Despite this, arc over failures are not too common.


.... Phil
 
"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:b783u1Ftdr6U1@mid.individual.net...
"Arfa Daily"

I also thought that 630 v on the anode of a modern EL34 is pushing it a
bit as well. The data sheets say that the maximum is 800 volts, but I
don't know how many of today's offerings I would trust to not be flashing
over at that sort of level ...


** EL34s and 6L6s are hardier than most people think and can stand very
high peak plate voltages when used in guitar amps.

A (4x EL34) 100W Marshall uses a B+ of about 475V and a screen supply that
is only a few volts less.

In normal operation, the plate voltage swings up to almost 900V and down
to about 75V during each cycle. However, in hard overdrive with a speaker
connected, something new happens and the peak plate voltage can reach 5kV.
Click to expand...


So if that's the case with a B+ of 475, imagine what peaks this thing must
get to with 630 v ... !!

Arfa


Some amp makers( eg Music Man, Boogie, Peavey) include high voltage diode
stacks wired from plates to ground to clip these very high peaks values,
but Marshall do not.

Despite this, arc over failures are not too common.


... Phil
Click to expand...
 
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:kumk0n$9nk$1@dont-email.me...
quote without comment...

http://www.rfcafe.com/references/popular-electronics/unpopular-electronics-aug-1959-popular-electronics.htm
Click to expand...

Taken on the chin ... :)

Arfa
 
"Arfa Daily"
"Phil Allison"
"Arfa Daily"

I also thought that 630 v on the anode of a modern EL34 is pushing it a
bit as well. The data sheets say that the maximum is 800 volts, but I
don't know how many of today's offerings I would trust to not be
flashing over at that sort of level ...


** EL34s and 6L6s are hardier than most people think and can stand very
high peak plate voltages when used in guitar amps.

A (4x EL34) 100W Marshall uses a B+ of about 475V and a screen supply
that is only a few volts less.

In normal operation, the plate voltage swings up to almost 900V and down
to about 75V during each cycle. However, in hard overdrive with a speaker
connected, something new happens and the peak plate voltage can reach
5kV.

So if that's the case with a B+ of 475, imagine what peaks this thing must
get to with 630 v ... !!
Click to expand...

** Any diodes in sight ??

Both Music Man and Dynacord used a B+ of 770V with EL34s.

Only MM used diodes.

Aussie brand "Lenard" used 900V with no diodes - but he used RC snubbers.

As one of the USA's most prolific movie makers and actors famously said.

" Do you feel lucky punk - well do ya ? "

And don't fucking snip posts to hell so you can hijack the context.




..... Phil
 
"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:b795qkF5nncU1@mid.individual.net...
"Arfa Daily"
"Phil Allison"
"Arfa Daily"

I also thought that 630 v on the anode of a modern EL34 is pushing it a
bit as well. The data sheets say that the maximum is 800 volts, but I
don't know how many of today's offerings I would trust to not be
flashing over at that sort of level ...


** EL34s and 6L6s are hardier than most people think and can stand very
high peak plate voltages when used in guitar amps.

A (4x EL34) 100W Marshall uses a B+ of about 475V and a screen supply
that is only a few volts less.

In normal operation, the plate voltage swings up to almost 900V and down
to about 75V during each cycle. However, in hard overdrive with a
speaker connected, something new happens and the peak plate voltage can
reach 5kV.

So if that's the case with a B+ of 475, imagine what peaks this thing
must get to with 630 v ... !!



** Any diodes in sight ??

Both Music Man and Dynacord used a B+ of 770V with EL34s.

Only MM used diodes.

Aussie brand "Lenard" used 900V with no diodes - but he used RC snubbers.

As one of the USA's most prolific movie makers and actors famously said.

" Do you feel lucky punk - well do ya ? "

And don't fucking snip posts to hell so you can hijack the context.




.... Phil
Click to expand...

Errr, I didn't snip anything at all ... ?? And no sign of any diodes, no.

Arfa
 
William Sommerwerck wrote:
quote without comment...

http://www.rfcafe.com/references/popular-electronics/unpopular-electronics-aug-1959-popular-electronics.htm
Click to expand...

Do you remember their "Just when I forgot my (Soldering) gun"
electronics pun contest?



I wanted to build this, but couldn't find the parts when I was 10.


<http://www.rfcafe.com/references/popular-electronics/nasa-136-june-1962-popular-electronics.htm>


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
 
"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:FvKdnZOBTYyNLI_PnZ2dnUVZ_t-dnZ2d@earthlink.com...
William Sommerwerck wrote:

quote without comment...

http://www.rfcafe.com/references/popular-electronics/unpopular-electronics-aug-1959-popular-electronics.htm


Do you remember their "Just when I forgot my (Soldering) gun"
electronics pun contest?



I wanted to build this, but couldn't find the parts when I was 10.


http://www.rfcafe.com/references/popular-electronics/nasa-136-june-1962-popular-electronics.htm
Click to expand...

I've got some nuvistors on the shelf still ... :)

Arfa


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
Click to expand...
 
I wanted to build this, but couldn't find the parts when I was 10.
http://www.rfcafe.com/references/popular-electronics/nasa-136-june-1962-popular-electronics.htm
Click to expand...

The nuvistor was a high-gain, low-noise vacuum tube intended for VHF and UHF.
RCA used them in their TVs, dubbing the sets "New Vista".

God, I loved Popular Electronics' schematics. In the past 55 years, I've never
seen better symbols. The pictorial is a work of art (reminiscent of Knight
Kit).
 
On Mon, 19 Aug 2013, Michael A. Terrell wrote:

William Sommerwerck wrote:

quote without comment...

http://www.rfcafe.com/references/popular-electronics/unpopular-electronics-aug-1959-popular-electronics.htm


Do you remember their "Just when I forgot my (Soldering) gun"
electronics pun contest?
Click to expand...
Maybe it was in 1971 when I was actually buying the magazine off the news
stand, or maybe about 1969 from a back issue I'd been given, but there was
a letter to Popular Electronics about how the magazine had changed, no
more Carl & Jerry, no more blah, blah, blah and noe more of that soldering
gun thing. The magazine replies "some of those things haven't been in the
magazine for most of a decade".

I had no idea what the soldering gun thing was about until I got older
back issues and actually saw it, and even then, I don't remember seeiing
that many installments of it.

I wanted to build this, but couldn't find the parts when I was 10.


http://www.rfcafe.com/references/popular-electronics/nasa-136-june-1962-popular-electronics.htm
Click to expand...
Nuvistors came along at about the wrong time. Nice and small, and good
noise figure, they were soon wiped out by transistors.

I remember one article reviewing a commercial VHF or UHF converter and
they said "I tried it next to my 417 converter, and either that needs a
big tuneup or these nuvistors are really good". The 417 being one of the
best tubes for a VHF or UHF front end, at least if you didn't want to
spend money on a 416 or a parametric amplifier. But the nuvistor
apparently gave good noise figure without as much fussing as the 417.

So there was a big wave of nuvistor converters and preamps, and then a few
years later, everyone was rushing to transistors (which weren't good to
begin with) then JFets and then towards the end of the sixties, people had
figure out how to make good low noise transistor preamps that didn't
overload as much.

Michael
 
"Michael Black" wrote in message
news:alpine.LNX.2.02.1308200912050.19245@darkstar.example.org...

On Mon, 19 Aug 2013, Michael A. Terrell wrote:

William Sommerwerck wrote:

quote without comment...

http://www.rfcafe.com/references/popular-electronics/unpopular-electronics-aug-1959-popular-electronics.htm


Do you remember their "Just when I forgot my (Soldering) gun"
electronics pun contest?
Click to expand...
Maybe it was in 1971 when I was actually buying the magazine off the news
stand, or maybe about 1969 from a back issue I'd been given, but there was
a letter to Popular Electronics about how the magazine had changed, no
more Carl & Jerry, no more blah, blah, blah and noe more of that soldering
gun thing. The magazine replies "some of those things haven't been in the
magazine for most of a decade".

I had no idea what the soldering gun thing was about until I got older
back issues and actually saw it, and even then, I don't remember seeiing
that many installments of it.

I wanted to build this, but couldn't find the parts when I was 10.


http://www.rfcafe.com/references/popular-electronics/nasa-136-june-1962-popular-electronics.htm
Click to expand...
Nuvistors came along at about the wrong time. Nice and small, and good
noise figure, they were soon wiped out by transistors.

I remember one article reviewing a commercial VHF or UHF converter and
they said "I tried it next to my 417 converter, and either that needs a
big tuneup or these nuvistors are really good". The 417 being one of the
best tubes for a VHF or UHF front end, at least if you didn't want to
spend money on a 416 or a parametric amplifier. But the nuvistor
apparently gave good noise figure without as much fussing as the 417.

So there was a big wave of nuvistor converters and preamps, and then a few
years later, everyone was rushing to transistors (which weren't good to
begin with) then JFets and then towards the end of the sixties, people had
figure out how to make good low noise transistor preamps that didn't
overload as much.

Michael







AKG put a Nuvistor into the C12a microphone, considered by many to be one of
the finest mics ever made.
(Subjectively, of course)

Neumann started putting them in the also-considered-one-of-the-finest U47
microphone when they ran out of Telefunken V14 tubes, but many people hated
the conversion.



Gareth.
 
This is quite interesting, sorry for OT/hijack:

http://www.wagner-microphones.com/vf14_background.htm



Gareth.
 
Arfa Daily wrote:
"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:FvKdnZOBTYyNLI_PnZ2dnUVZ_t-dnZ2d@earthlink.com...

William Sommerwerck wrote:

quote without comment...

http://www.rfcafe.com/references/popular-electronics/unpopular-electronics-aug-1959-popular-electronics.htm


Do you remember their "Just when I forgot my (Soldering) gun"
electronics pun contest?



I wanted to build this, but couldn't find the parts when I was 10.


http://www.rfcafe.com/references/popular-electronics/nasa-136-june-1962-popular-electronics.htm

I've got some nuvistors on the shelf still ... :)
Click to expand...

I have about a dozen, in 6.3 & 13 volt versions. The 6CW4/6DS4 was
used in a lot of RCA TV tuners. The 13CW4/13DS4 were used in a crude
tone squelch in some 'Sonar' brand business radios. The Tektronix 453
scope used some with industrial part numbers, as well.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
 
Gareth Magennis wrote:
AKG put a Nuvistor into the C12a microphone, considered by many to be one of
the finest mics ever made.
(Subjectively, of course)

Neumann started putting them in the also-considered-one-of-the-finest U47
microphone when they ran out of Telefunken V14 tubes, but many people hated
the conversion.
Click to expand...

The Nuvistors weren't microphonic enough for them :)


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
 
William Sommerwerck wrote:
I wanted to build this, but couldn't find the parts when I was 10.
http://www.rfcafe.com/references/popular-electronics/nasa-136-june-1962-popular-electronics.htm

The nuvistor was a high-gain, low-noise vacuum tube intended for VHF and UHF.
RCA used them in their TVs, dubbing the sets "New Vista".
Click to expand...

I saw a lot of them in garage door openers, before the could build
stable solid state UHF receivers. I repaired them for a friend that
owned an 'Overhead Door Company' franchise. The sensitivity of some were
amazing. Careful tuning of the RF and tone circuits could give a block
and a half range if it was out in the open.


God, I loved Popular Electronics' schematics. In the past 55 years, I've never
seen better symbols. The pictorial is a work of art (reminiscent of Knight
Kit).
Click to expand...

They were drawn mainly for kids and beginners, to give a perspective
of the layout used in the prototypes that were built for the articles.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
 
"Michael A. Terrell" wrote in message
news:Q6-dncNX05PiNo7PnZ2dnUVZ_q6dnZ2d@earthlink.com...
Gareth Magennis wrote:

Neumann started putting them in the also-considered-one-of-the-finest
U47 microphone when they ran out of Telefunken V14 tubes, but many
people hated the conversion.

The Nuvistors weren't microphonic enough for them. :)
Click to expand...

"Listen to the depth and spaciousness..."
"Yes... and that's just from a single mic!"
 
"Gareth Magennis" <gareth.magennis@ntlworld.com> wrote in message
news:w8NQt.36646$Yc.5260@fx26.am4...
"Michael Black" wrote in message
news:alpine.LNX.2.02.1308200912050.19245@darkstar.example.org...

On Mon, 19 Aug 2013, Michael A. Terrell wrote:


William Sommerwerck wrote:

quote without comment...

http://www.rfcafe.com/references/popular-electronics/unpopular-electronics-aug-1959-popular-electronics.htm


Do you remember their "Just when I forgot my (Soldering) gun"
electronics pun contest?

Maybe it was in 1971 when I was actually buying the magazine off the news
stand, or maybe about 1969 from a back issue I'd been given, but there was
a letter to Popular Electronics about how the magazine had changed, no
more Carl & Jerry, no more blah, blah, blah and noe more of that soldering
gun thing. The magazine replies "some of those things haven't been in the
magazine for most of a decade".

I had no idea what the soldering gun thing was about until I got older
back issues and actually saw it, and even then, I don't remember seeiing
that many installments of it.


I wanted to build this, but couldn't find the parts when I was 10.


http://www.rfcafe.com/references/popular-electronics/nasa-136-june-1962-popular-electronics.htm

Nuvistors came along at about the wrong time. Nice and small, and good
noise figure, they were soon wiped out by transistors.

I remember one article reviewing a commercial VHF or UHF converter and
they said "I tried it next to my 417 converter, and either that needs a
big tuneup or these nuvistors are really good". The 417 being one of the
best tubes for a VHF or UHF front end, at least if you didn't want to
spend money on a 416 or a parametric amplifier. But the nuvistor
apparently gave good noise figure without as much fussing as the 417.

So there was a big wave of nuvistor converters and preamps, and then a few
years later, everyone was rushing to transistors (which weren't good to
begin with) then JFets and then towards the end of the sixties, people had
figure out how to make good low noise transistor preamps that didn't
overload as much.

Michael


AKG put a Nuvistor into the C12a microphone, considered by many to be one
of the finest mics ever made.
(Subjectively, of course)

Neumann started putting them in the also-considered-one-of-the-finest U47
microphone when they ran out of Telefunken V14 tubes, but many people
hated the conversion.



Gareth.
Click to expand...

Interestingly, these ones that I have came from a very high end - well very
expensive, anyway ! - audio preamp made by Musical Fidelity. I replaced them
because they were really quite microphonic.

Arfa
 
On Tue, 20 Aug 2013 18:05:58 +0100, "Gareth Magennis"
<gareth.magennis@ntlworld.com> wrote:

This is quite interesting, sorry for OT/hijack:

http://www.wagner-microphones.com/vf14_background.htm



Gareth.
Click to expand...
Thanks for posting that link Gareth, it was really interesting.
Eric
 
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