Maihak preamps

[bancho]

Does anybody know why are the Maihak preamps (V41A, V44B, etc) so "undiscovered"... all I can see for sale is one unit every couple of years and the prices are sky high. Are these preamps any good? Are there any schematics or did anyone try to build any of these?

 

[Michael Tibes]

I guess it needs a certain amount of units circulating to create a market. There are most likely a lot less units than V76s, which are pretty rare already. They are rare, big and probably need quite some service attention - but sound amazing. I just used one of mine for lead vocals. The other one I have started to desintegrate, all the resistors lose the paint covering the carbon.

Michael

 

[bancho]

Does anybody have the schematics (eg. V41A)?

 

[tony hunt]

I think I downloaded one from Darius Kubarth. Search for V41 on this page: http://audio.kubarth.com/rundfunk/index.cgi

 

[bancho]

Thanks tony for the link!
Do you maybe know which transformers does it have?

 

[bancho]

I searched the web but couldn't find any useful information about it (except the kubi link tony provided). I wonder why nobody build it (as far as I know, regarding the gdiy and gs). At least the scarcity and the praise of the ones who have it should be the reason, right?

ps: maybe this thread should be moved to another folder?

 

[tony hunt]

Here's another link to a schematic drawn slightly different and with some slight differences
e.g. the OT is 9:1 here. On the Kubarth link I read 11,2:1 for the OT
http://www.cdvandt.org/Magnetophon-Proj-2-SB-V41-modi-A3-cut.pdf

Take a look at the two anode chokes in each schematic.

Last time I ever saw a pair of these for sale, the iron looked they had been chucked in the sea. Perhaps the attatched png file of a healthy gut shot will show up.

Cheers, tony

 

[ungifted]

For the brave ones who dare to build it I have EZ11 nos nib in stock. Used to have EF12 but sold out (have some without boxes, and some used).
Transformers and chokes are the first reason why such oldscool schematics are not popular, imo, But it's often interesting to listen any review on preamp based on EF12, EF14, EF37a etc.

 

[bancho]

Still gathering some information about iron & stuff...

- Is there any reason why not to use the Sowter replacement IT and OT for V72? The ratios are looking good (although the ratio is not all, I know).

- the big question is still the plate choke. Sowter also offers some chokes. As this preamp somehow precedes the V72, could I use the V72 choke (same reason as tx)? I know the EF12 and EF804 are not the same esp. regarding the plate current (but yet very similar, so does it matter anyhow?).
@CJ: did you just rewind the V72 choke for a test or is it possible to get it somewhere (eg. from you)?

- about the EF12s... I wonder why there is only one EF12k, all the others are non-k. Is it because it only matters at the beginning of the chain (because of the input) to make the path "clean/silent" and this then translates to the ordinary EF12? Should it be better to use all tubes EF12k?

Thanks for all the answers / elaborations!
(p.s.: some things might sound/read strange... sorry for that, english is not my native language)

 

[Michael Tibes]

The EF12K is a low microphonic version of the EF12. I don't know whether it is a selected EF12 (not a different construction), but I guess so. This matters most in the first stage as all microphonics happening there is being amplified. So a 'K' in the first stage should be sufficient, but using 'K's throughout should be possible.

Michael

 

[rock soderstrom]

The EF12K is a low microphonic version of the EF12. I don't know whether it is a selected EF12 (not a different construction), but I guess so. This matters most in the first stage as all microphonics happening there is being amplified. So a 'K' in the first stage should be sufficient, but using 'K's throughout should be possible.

Michael

+1

The "k" stands for "klingarm" or in english low microphonic.

 

[emrr]

It's funny, the various 1930's RCA preamps are also 41-'x' in name.  Similarly unknown due to scarcity, very expensive when found.  I used to look for V41's/etc as a regular search, and never saw one for sale.

 

[DaveP]

Check out the East German version, the V241.
https://groupdiy.com/index.php?topic=49810.msg638123#msg638123

The advantage of this is that the much lower internal resistance of an ECC85 allows you to use a lower 150 Henry choke, like a Hammond, to get the same result.
https://groupdiy.com/index.php?topic=67386.0

I used this design with a V76 front end which is the same in principle as that used in the V41 and it works very well.

My customer said it works especially well with his AKG C12 mic of the same era.

DaveP