[Patrick M.B.]

Hello group,

I found a pair of these miniature Telefunken triodes AC701, connection with
flying wires, no socket.
Any idea of what these are for? They seem used and come from an university
stock, in original package.
What could be the value of these tubes?
A short search tells these are rare.

Patrick

[Sander deWaal]

"Patrick M.B." said:

Hello group,

I found a pair of these miniature Telefunken triodes AC701, connection with
flying wires, no socket.
Any idea of what these are for? They seem used and come from an university
stock, in original package.
What could be the value of these tubes?
A short search tells these are rare.


A microphone preamp tube:
http://tdsl.duncanamps.com/sheets/ac701/ac701g.gif
http://oldradio.qrz.ru/tubes/foreign/01/AC701.gif
http://tdsl.duncanamps.com/link.php?target=0025A13F


--
- Ever seen someone with 5.1 ears? So, what does that tell you? -

[Patrick M.B.]

"Bret Ludwig" schreef in bericht
ups.com...

Sander deWaal wrote:
"Patrick M.B." said:

Hello group,

I found a pair of these miniature Telefunken triodes AC701, connection
with
flying wires, no socket.
Any idea of what these are for? They seem used and come from an
university
stock, in original package.
What could be the value of these tubes?
A short search tells these are rare.



They are worth a great deal of money in fact, as users of Neumann mics
valued in the high thousands or tens of thousands need them. You hit
the Superfecta, that is, if you are not a troll.


They have the same batch?number U6209500, one has a mark 984, the other 931
(I think these are serial numbers) and seem to be carefully desoldered:
http://users.belgacom.net/m28/images/12130002_984.JPG
http://users.belgacom.net/m28/images/12130001_931.JPG
I wonder to what parameter to test these little tubes.

[Stevel]

Patrick M.B. wrote:
Hello group,

I found a pair of these miniature Telefunken triodes AC701, connection with
flying wires, no socket.
Any idea of what these are for? They seem used and come from an university
stock, in original package.
What could be the value of these tubes?
A short search tells these are rare.

Patrick

These were used in Neumman M50 M49 KM50 series and SM2 microphones and
also the Euro version of the ELAM 250/251. The prefered version is
AC701k and had a wrapper with selection number as these were selected
by Neumman for low noise and microphonics.
The k indicated a special frame grid for low microphony. Early non k
versions had a tubular grid
and were used for less critical audio applications.
I believe after 1965 all AC701 had a frame grid and the k may have been
ommited.
All AC701 have serial numbers.

NOS genuine Telefunken AC701k tubes can sell for hundreds of $.
Used or ex equipment and non K versions are worth much less as any
buyer will assume they are faulty or noisy as nobody would normally
remove a good one from an otherwise good mic.
What makes you think they are used? A used one would have shortened
leads that show signs of being twisted around a turret. Some versions
were used in other miniature electronics such as military radios etc.

Go to Ake's excellent web site for data.
http://www.akh.se/tubes/htm/ac701.htm

The real gold dust tube is a NOS Telefunken VF14m. These can sell for
thousands of $
Used in Nuemman M47/48 mics.

You could put them on eBay with pics and an accurate description to get
their value.
I would suggest you sell them without warrenty as is as the only way to
be sure they are good for mics is to run them for at least 24 hours in
the mic to expose any noise problems.

Steve

[[email protected]]

Stevel wrote:
Patrick M.B. wrote:
Hello group,

I found a pair of these miniature Telefunken triodes AC701, connection with
flying wires, no socket.
Any idea of what these are for? They seem used and come from an university
stock, in original package.
What could be the value of these tubes?
A short search tells these are rare.

Patrick

These were used in Neumman M50 M49 KM50 series and SM2 microphones and
also the Euro version of the ELAM 250/251. The prefered version is
AC701k and had a wrapper with selection number as these were selected
by Neumman for low noise and microphonics.
The k indicated a special frame grid for low microphony. Early non k
versions had a tubular grid
and were used for less critical audio applications.
I believe after 1965 all AC701 had a frame grid and the k may have been
ommited.
All AC701 have serial numbers.

NOS genuine Telefunken AC701k tubes can sell for hundreds of $.
Used or ex equipment and non K versions are worth much less as any
buyer will assume they are faulty or noisy as nobody would normally
remove a good one from an otherwise good mic.
What makes you think they are used? A used one would have shortened
leads that show signs of being twisted around a turret. Some versions
were used in other miniature electronics such as military radios etc.

Go to Ake's excellent web site for data.
http://www.akh.se/tubes/htm/ac701.htm

The real gold dust tube is a NOS Telefunken VF14m. These can sell for
thousands of $
Used in Nuemman M47/48 mics.

You could put them on eBay with pics and an accurate description to get
their value.
I would suggest you sell them without warrenty as is as the only way to
be sure they are good for mics is to run them for at least 24 hours in
the mic to expose any noise problems.


The AC701 was designed for meter buffering in avionics.

[Stevel]

wrote:
Stevel wrote:
Patrick M.B. wrote:
Hello group,

I found a pair of these miniature Telefunken triodes AC701, connection with
flying wires, no socket.
Any idea of what these are for? They seem used and come from an university
stock, in original package.
What could be the value of these tubes?
A short search tells these are rare.

Patrick

These were used in Neumman M50 M49 KM50 series and SM2 microphones and
also the Euro version of the ELAM 250/251. The prefered version is
AC701k and had a wrapper with selection number as these were selected
by Neumman for low noise and microphonics.
The k indicated a special frame grid for low microphony. Early non k
versions had a tubular grid
and were used for less critical audio applications.
I believe after 1965 all AC701 had a frame grid and the k may have been
ommited.
All AC701 have serial numbers.

NOS genuine Telefunken AC701k tubes can sell for hundreds of $.
Used or ex equipment and non K versions are worth much less as any
buyer will assume they are faulty or noisy as nobody would normally
remove a good one from an otherwise good mic.
What makes you think they are used? A used one would have shortened
leads that show signs of being twisted around a turret. Some versions
were used in other miniature electronics such as military radios etc.

Go to Ake's excellent web site for data.
http://www.akh.se/tubes/htm/ac701.htm

The real gold dust tube is a NOS Telefunken VF14m. These can sell for
thousands of $
Used in Nuemman M47/48 mics.

You could put them on eBay with pics and an accurate description to get
their value.
I would suggest you sell them without warrenty as is as the only way to
be sure they are good for mics is to run them for at least 24 hours in
the mic to expose any noise problems.


The AC701 was designed for meter buffering in avionics.

That's interesting. Do you have any more information on that?

Steve

[Karl]

Stevel wrote:
Patrick M.B. wrote:
Hello group,

I found a pair of these miniature Telefunken triodes AC701, connection with
flying wires, no socket.
Any idea of what these are for? They seem used and come from an university
stock, in original package.
What could be the value of these tubes?
A short search tells these are rare.

Patrick

These were used in Neumman M50 M49 KM50 series and SM2 microphones and
also the Euro version of the ELAM 250/251. The prefered version is
AC701k and had a wrapper with selection number as these were selected
by Neumman for low noise and microphonics.
The k indicated a special frame grid for low microphony. Early non k
versions had a tubular grid
and were used for less critical audio applications.
I believe after 1965 all AC701 had a frame grid and the k may have been
ommited.
All AC701 have serial numbers.

NOS genuine Telefunken AC701k tubes can sell for hundreds of $.
Used or ex equipment and non K versions are worth much less as any
buyer will assume they are faulty or noisy as nobody would normally
remove a good one from an otherwise good mic.
What makes you think they are used? A used one would have shortened
leads that show signs of being twisted around a turret. Some versions
were used in other miniature electronics such as military radios etc.

Go to Ake's excellent web site for data.
http://www.akh.se/tubes/htm/ac701.htm

The real gold dust tube is a NOS Telefunken VF14m. These can sell for
thousands of $
Used in Nuemman M47/48 mics.

You could put them on eBay with pics and an accurate description to get
their value.
I would suggest you sell them without warrenty as is as the only way to
be sure they are good for mics is to run them for at least 24 hours in
the mic to expose any noise problems.

Steve

I'm glad to see this thread. I aquired seven used ac701k's with a small
batch of tubes I found in the church I work for. Nobody in the AV dept.
knows anything about the old tubes but I'll ask about Neuman mics. They
are buying some new AKG tube mics soon, but I don't think they still
have Neumans. I suspect (by the way they seem to operate) that these
used tubes were replaced regularly whether they needed to be or not.
That would explain why they kept the old ones, knowing their value. The
leads have been carefully desoldered and there are coils (I assumed for
strain relief) in the leads, but mine look different than these photos.
They have two leads at one end and three at the other.

[Karl]

Karl wrote:
Stevel wrote:
Patrick M.B. wrote:
Hello group,

I found a pair of these miniature Telefunken triodes AC701, connection with
flying wires, no socket.
Any idea of what these are for? They seem used and come from an university
stock, in original package.
What could be the value of these tubes?
A short search tells these are rare.

Patrick

These were used in Neumman M50 M49 KM50 series and SM2 microphones and
also the Euro version of the ELAM 250/251. The prefered version is
AC701k and had a wrapper with selection number as these were selected
by Neumman for low noise and microphonics.
The k indicated a special frame grid for low microphony. Early non k
versions had a tubular grid
and were used for less critical audio applications.
I believe after 1965 all AC701 had a frame grid and the k may have been
ommited.
All AC701 have serial numbers.

NOS genuine Telefunken AC701k tubes can sell for hundreds of $.
Used or ex equipment and non K versions are worth much less as any
buyer will assume they are faulty or noisy as nobody would normally
remove a good one from an otherwise good mic.
What makes you think they are used? A used one would have shortened
leads that show signs of being twisted around a turret. Some versions
were used in other miniature electronics such as military radios etc.

Go to Ake's excellent web site for data.
http://www.akh.se/tubes/htm/ac701.htm

The real gold dust tube is a NOS Telefunken VF14m. These can sell for
thousands of $
Used in Nuemman M47/48 mics.

You could put them on eBay with pics and an accurate description to get
their value.
I would suggest you sell them without warrenty as is as the only way to
be sure they are good for mics is to run them for at least 24 hours in
the mic to expose any noise problems.

Steve

I'm glad to see this thread. I aquired seven used ac701k's with a small
batch of tubes I found in the church I work for. Nobody in the AV dept.
knows anything about the old tubes but I'll ask about Neuman mics. They
are buying some new AKG tube mics soon, but I don't think they still
have Neumans. I suspect (by the way they seem to operate) that these
used tubes were replaced regularly whether they needed to be or not.
That would explain why they kept the old ones, knowing their value. The
leads have been carefully desoldered and there are coils (I assumed for
strain relief) in the leads, but mine look different than these photos.
They have two leads at one end and three at the other.

I took another look at them last night. They are four and one wired,
instead of three and two. Also they are black painted instead of clear,
the way I remembered, so I must have been thinking of something I saw
on the web.