Telefunken EF804S (EF 804 S)

As the EF804S are a good start to a V76 or V72, what are the costs I need to add to get a preamp?
I mean I know that there are expansive Xformer reeditions but I do not necessary want to go to the exact clone way. I just would like to know if it would be possible to cut cost without sacrifying quality and get a good tube preamp based on these EF804S or maybe should I sell these cause I?m a newbie and tubes are dangerous and difficult to work with.

Yes, maybe you should sell, but if you keep it, you could use it anywhere an ef86 is called for... Maybe a microphone? It´s basically the same tube, but 804s should be lower noise.

But you could also try my simplified verdion of the V76:

http://www.groupdiy.com/index.php?topic=15169&highlight=simplified+v76

I didn´t tried it myself, but I can´t see why it wouldn´t work well.

Use any high ratio 1:10 or better input transformer. UTC sounds great!

But you still need a plate chopke. This one could be DIY. Use a double or tripple bobin to wind lots of turns of very thin wire and you are done. I think you need something like 6k resistance and a very thin airgap in the core...

Sowter will sell you a higher inductance one. Don´t know if that would work. Or maybe Oliver at TAB, but then you have to pay more than $100 each.

Think about a REDD 47 mic pre. Much easier.

Mmmm. Thank you for these infos.
I?ll look at the REDD 47 and easier projects available with EF86.
These tubes are going in my very long term project drawer, next to the two 1073 channels.

The EF86 is the lower spec´d version of the EF806S, but not of the EF804S. I´m not sure if they even have the same pinout. You´d better check that.

Ah ok thanks. :wink:

EF86 and EF804(S) do not have the same pinout. I was actually looking around this subject, because I am having an old tube mike at home wich I am trying to restore. Now my EF804(S) seems (to me) broken.
So I was searching for an possibility to stick in some other easy to get tube to find out if the tube is faulty or me.
You should be able to do most things aimed for an EF86 with an EF804. Just beware of the pinout.
If you don´t like your EF804´s anymore, because you suddently start to hate tube stuff. You can send it to me :green:
If you are able to understand some German, this may be an interesting read for you. It´s about EF86 and EF804. And provides datasheets:

http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Ef86/Ef86.htm

[quote author="DerEber"]You should be able to do most things aimed for an EF86 with an EF804. Just beware of the pinout.[/quote]

Another tube that fits into this family is the E80F (Philips, Mullard and others). It was introduced by Philips in 1954 as higher quality replacement for the EF86. In some circuits I like the E80F better than a EF86 or even EF806S. Both are pin compatible, but the E80F bottle is a little bit higher and might not fit into a any case without trouble.
The E80F seems to be relatively unknown and can often be found much cheaper than EF86/806S tubes.

Olaf

Build a V72.
Two stage amp, simple circuit, awesome amp, you already have two of the most expensive pieces.
All you need is an input, and output, and a choke.
You might have some scrap iron laying around, do ya?
Sowter sells a choke for the V-72.
I do not know your account balance, maybe go the Edcor route if you are just getting your feet wet.

Any 600:10K xfmr will work.
Output could be a Jensen 8:1/ 4:1 Ni output.
This is a parafeed, so no worry about DC on output.

Very easy wiring job.
Go for it.

[quote author="CJ"]Build a V72.
Very easy wiring job.
Go for it.[/quote]

Thanks, this idea is sexier to me.
No traffos lying around, apart from HS-66 but I can not use these in a V72.
I'll check evilBay.