Can anyone comment on the Telefuken v311 - diyAudio
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Old 23rd July 2003, 06:30 PM   #1
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Default Can anyone comment on the Telefuken v311

Have a chance to buy one in working condition. The tubes seem to be difficult to get, but the quality is said to be among the best of their type. I would power my 88 db speakers (that before I finally go for a SET/full range combination).

Thanks in advance
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Old 23rd July 2003, 11:51 PM   #2
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Hi,

Do you mean VF11?
If that's the one then it's a valve used in microphones, nothing to make an amp with...not even a mono one.

If ever you happen to have seen it, it looks like a scaled down oilfilter for cars, no kidding.

Cheers,
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Old 24th July 2003, 12:13 AM   #3
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Default IT'S AN AMP?...

Hi,

If this is the one then you'd better find some of those expensivissimo EL156s as spares as well:

V311

Cheers,
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Old 24th July 2003, 02:39 PM   #4
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Hi fdvgrove,

Yes thats the one. I was aware the El156 are expensive, but I think not as expensive here in germany as in other places.

Could you comment on the amps sonic quality? Your link is the only page with information I was able to find.

thanks,

Seb
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Old 24th July 2003, 06:53 PM   #5
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Hi,

Quote:
Could you comment on the amps sonic quality?
The only thing I can add to it is that the EL156 is a very good valve.

TFK always had a good rep for quality but am I correct in thinking that this is a public address amp?

Not that that is necessarily a bad thing...

Cheers,
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Old 25th July 2003, 08:35 PM   #6
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> Telefuken v311.... Have a chance to buy one .... power my 88 db speakers

The posted schematic shows ONLY a 100V output, intended to be loaded with 100Ω or more.

i.e., this is a dedicated Public Address amplifier made to drive long lines to multiple speakers, each speaker having a transformer to match voice coil impedance to an appropriate loading on the line.

You can get 100 watt 100V to VC transformers, but they are very expensive (and very heavy), and won't do the sound any good.

Oh, there is a 1V winding too but this is surely for a small monitor speaker and VU meter in the amplifier closet. 1V in 8Ω is 0.125 Watts, and this is a lot of cost, bulk, and heat for a 1/8 watt amp. In theory you could put 0.01Ω on the 1V tap and get the 100 watts, but 0.01Ω is not a standard speaker impedance and the winding probably has self-resistance well over 0.01Ω.

This is not a good amp for driving 4-8-16Ω speakers.

> The tubes seem to be difficult to get

As a practical matter: you "could" adapt it to run 6550, which is available as good-old stock and readily available as new-cheap stock. The B+ is well over the 6550's rating but the better types will stand it for many hours. You would have to rig ceramic octal sockets above the existing 10-pin sockets. You must use very well insulated wire for the plate leads because they will have over a kilovolt of audio. Leads must be very short (a hi-volt hi-power amp that goes into oscillation is a frightening event). Cleanliness is essential when working with 840+V on octal sockets: even fingerprints will encourage arc-over.

Tack a 100Ω resistor across R9 and a 500µFd cap across C4 to get the bias supply up to over -35V. Fire-up with DC voltmeters on R58 and R16 (80Ω resistors) and hope they don't go over 4 volts (42 Watts in the 6550 plate). With small R9 a 6550 will probably bias-up with less than 3 volts on the 80Ω resistors. If it is less than 2.5V, increase the size of the R9 resistor to get 2.5V-3.0V idle voltage on the cathodes.

However unless you have 100Ω speakers, I don't see that this amp is any use in home audio. It was made for a ballpark, large factory, etc, and its output is dedicated to that work.

Unless of course you have a similar model except wound for voice-coil impedance outputs.
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Old 25th July 2003, 09:45 PM   #7
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Quote:
Originally posted by fdegrove
Hi,

Do you mean VF11?
If that's the one then it's a valve used in microphones, nothing to make an amp with...not even a mono one.
Wasn't that a VF14 penthode used in the legendary Neumann U47 and U48? Collectors will pay a small fortune for an original VF14.

Click the image to open in full size.


Cheers
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Old 25th July 2003, 09:48 PM   #8
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Hi,

Yep, a few thousand $ a pop.

EF14 and UF14 are well sought after too, as is the legendary TFK AC701, a subminiature used in some mics as well.

Cheers,

My last ones went to Holland...
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