V76 Hack !!!

Too many expensive pentodes in a V76 :evil:. I want something simpler but something that I still can call a V76, and still will sound like a V76 (if original iron is used). How about this?

I take it we are taking about the EF86 - are those expensive down your way?
They are about £10+ over here

This industry surplus/general junk dealer in .de has E83F (which is not a long life EF83 (just for the archive :wink: )) pretty cheap:
http://www.pollin.de/shop/shop.php?cf=suche_ergebnis.php&S_TEXT=e83f&btn_submit=Suchen&ts=0
(they have PCC189, too. and D3a, which looks like a very nice hi gm signal pentode)

Shipping to Brazil might be another thing, although you can subtract 16% sales tax...

Don't tell anybody, but 6SJ7 is pretty much an EF-86.
And since you need to try 10 ef86 to get one low noise...

EF-86 info:

http://tdsl.duncanamps.com/show.php?des=EF86

6SJ7 $4.40 at Antique.
Metal.

Glass version: $10.40

www.tubesandmore.com




I bet you find mucho 6SJ7 down south. Maybe many Tele tubes also. I think Telefunken
stuff was briefly made down there, no?

E83F are not the problem. They are cheap. It's the EF804S in the original design that are $35-50 each, which are expensive.

Yes, I´m talking about EF804s. The original V76 calls for three of those and one E83F. I only managed to get two EF804s in the long run.

CJ, I don´t think I´ve ever seen telefunken tubes made in Brazil. We had lots of miniwatt and RCA, and other good quality tubes, but no telefunken as far as I know...

Anyway, I was trying a V76 simplified schematics, with only two tubes instead of four, and no filter. Just a mic amp. This way I could use my two EF804s and build a two channel in a rack unit to try it out. I really think many people run away because from this schem because of the three EF804s and two also expensive chokes. This modified use also only one choke.

What do you think about the schematic I´ve posted?

Looks cool!
You might want to try using EF 86 for output as well. What's the gain on the 83F?

Server got hacked for a while, thats why not a lot of replys, I think.


cj

mmm... For using a EF86 on the output I think the choke would have to go up in Henries, and also the output xfr pri impedance should go up.

Didn´t you used a jensen 10k:600 output on yours, with the E83F? So, it seems that this output stage can drive more load than in the original. If the schematics is right, the original output was a 50k:600, but I will try going lower to a 30k:600 and see if it works well.

I also have some 250H / 6kohms chokes here, but these are single bobin. I don´t know if it will work nice. The original was dual bobin. I will start with this and then buy an original from oliver in the future.

some E83F data:

http://www.mif.pg.gda.pl/homepages/frank/sheets/009/e/E83F.pdf
http://www.mif.pg.gda.pl/homepages/frank/sheets/030/e/E83F.pdf
http://www.mif.pg.gda.pl/homepages/frank/sheets/050/e/E83F.pdf

Isn't it possible to use the "consumer" quality EF804 instead of the EF804s for the V76 / V72 style preamps? Last time I looked these are way more affordable...

cheers, Marten

Possibly it could be used. There are other subs possible also. Oliver has an article about it.

Making the second stage another E804 type pentode would lead us to a V72 circuit.