Siemens/Klangfilm Postwar Cinema Amplifiers (W

The name “Klangfilm”stands for Siemens ‘ famous cinema/theater ra n g e. K l a n g f i l m directly translated means “the sound of c i n e m a ” or the “so und o f the film ”.

Siemens produce d some of t he most sought after power amplifiers and speakers, as well as some remarkable preamplifiers and mixers.

Made in W-Germany were the models:

KL-401, KL-402a, KL-403a, KL-502a, KL-

408a, KL-203/4 and the KL-V-410. There are other models, but they are ELA amps, using only 100 ohms output tra n s f o r m e r s and so not useful for the av e rage audio enthusiast.

Made in Austria is the model KL-5418, there might be more Austrian models but in more than fifteen years research,this is the only one I came across, and I could not find any literature on this model.

Klangfilm used only three power tubes, the EF-12 (just after the wa r, which is a small version of the EL-156, and sounds very smooth and beautiful, if made by

Te l e f u n k e n ) ; the German professional

F 2 a 1 1 , and later the EL-34. The driver tubes were the EF-12, an early version of the famous EF-804 (very similar to the EF-

86, but far superior); later the ECC-40, an early version of the ECC-82 (12AU7) and then the ECC-83. Rectifiers were the EZ-

12 and ,later, the GZ-34.

All amplifiers were designed for cinema u s e, which means that the ultra - s e n s i t i v e inputs should not be used for home audio

It is a shame that one cannot make use of the outstanding input tra n s f o r m e r s, b u t . . .

they can be used for other designs! Most users just connect the input to the grid of the 2nd, or if less gain is needed, even to the grid of the 3rd of the drivers. An input resistor in the region of 1 Kohms in series to the grid and a 100-220 picofarad C will

Siemens/Klangfilm Postwar Cinema Amplifiers

(W-Germany and Austria) by Dipl. Ing. H. Jakobi, Sulzbach, Germany

be all that is needed to suppress high frequency disturbances or oscillation.

With some luck one might find an old pair of matching input transformers and to use for balanced input. But beware, it is better stick with the simple “ g r i d ” e n t r y, i n s t e a d of using a bad transformer.

The heart of these amplifiers are their outst anding ou tpu t tra n s f o r m e r s, w h i c h nobody can wind anymore with this quality. All parts are first class, it is not recommended to modify too much, and most of the electrolytic condensers will work for many years. In the early KL-401a only p a p e r-in-oil condensers are used. T h e s e sadly can dry out, and it is recommended to replace them with similar types.

The build quality is typical W- G e r m a n ,

Mercedes like, long lasting and precision m e c h a n i c s, best parts quality: S i e m e n s c e ramic insulated silver foil coupling-C’s

( ! ! ! ) , MP or paper-in-oil C’s, e t c. , will be found as a standard! Tube rectification with highest quality chokes is standard, the power transformers are oversized, use the best mate rials and are us ually

110/120/220/240 volts, 50/60 Hz.

All tubes can still be found easily, only the

F2a11 is expensive, but then it is a professional long life tube and shall last at least

8000 hours, if matched pairs are used.

Very important: do not use cheap EL-34’s!

Only original Te l e f u n k e n s, Va l v o ’s (which are also sold under Philips, M i n i wa t t ,

S i e m e n s, A m p e r e x , and yes. . . also the famous Mullard was made by Philips Valvo in Holland!) must be used for full potential. Do not use the E-German EL-12 (also

EL-12N) made by Hoges, it is inferior! The best is the Te l e f u n k e n , the stronger EL-

12/325 and EL-12/375 can take higher plate voltages and are suited as well.

As the F2a11 (and the F2a, which just has a different base) are such extra o r d i n a r y p e n t o d e s, which cannot be found elsewhere, I decided to have the data here as well:

Type Longlife prof.Tetrode

Filament 6.3V/2A

(indirectly heated)

Platevolt. 250V

Platecurrent

Max platevolt

97 mA

425 V

(some books suggest 600V max.!)

Gridvolt 250V (max. 425 V)

Neg. gridvolt

Platedissip.

-19V

30W

The way this tetrode is built makes it perfect for triode configura t i o n s. It sounds extremely natural if applied correctly, even in a non-triode circuit!

IMPORTANT: Klangfilm used a Klangfilm code for most of their tubes, starting with a KL like for the other units. For the postwar amps we have the most important codes: (prewar codes will be shown in part

II!)

KL-70715 = EF-12

KL-70716 = EF-12k

(k stands for “klirrarm”= low noise)

KL-73550 = EF-12

KL-73551 = F2a11

KL-76303 = RGN 2504

Tubes used in the later models like the EF-

4 0 , E C C - 8 3 , E L - 3 4 , GZ-34 have no KL code!

The KL-401a:

This unit is made with a cast frame and is very heavy (about 60 lbs.). Four EF-12’s are used, and a special tone control unit (volume, bass and treble) can be plugged into the circuit between the input tube and the 3rd stage (not advised for best performance). Wi t h o u t the tone control unit it is easiest to use the grid of the 3rd EF-12 as the input (V- 3 ) .

The rectification is done with the EZ-12, a very common rectifier used in German studio and cinema technique, and in early models with the RGN-2504, which is in its mesh plate versions together with the

RGN-2004 the very best rectifier I ever heard.

We find paper-in-oil condensers throughout the whole circuit and a wonderful output transformer with 15 ohms and 200 ohms. 200 ohms were not needed for ELA s p e a k e r s, but for some special Siemens speakers which will be introduced in a later part. The EF-12/375’s in the PP output stage are triode connected (without the usual 100 ohms resistor, the screen grid is directly connected to the plate!)

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The KL-402a and 403a

(identical): These amps are nearly the same in circuitry as the 401a, but use precision welded galvanized steel sheets in the case and are 19” rack-mount (like all amps built after the

401’s). Instead of the EZ-12 the GZ-34 is used as a rectifier and a better tone control unit is used (if needed). M P - c o n d e n s e r s replace the paper-in-oils (and are still better than all MKP’s or electrolytic C’s!) and we find Siemens silver foil coupling C’s. I compared this amp with the famous

M a rantz 9’s. The KL-403’s outperformed the Marantz with ease! I am not kidding!

Even the KL-502a,after modified to triode connection of its EL-34’s did.The KL-403 is on the same level as the famous WE-86, and this means something as it does not use 300B’s. It is as dynamic and immedia t e, a little less euphonic and with more clarity and speed. A fantastic amp. A n d built to last forever. A n d . . . the price is about 40% of the Marantz Model 9).

The KL-502a:

This amp uses the wellknown EL-34 and is in my ears the very best EL-34 amp ever built, if triode connected (connect each screen grid of each

EL-34 via 100 ohms on the plate and only use “real” EL-34’s as mentioned before). It outperformed the Marantz 9 with ease, and is very close in its sonic signature to the KL-403a. The driver/input tubes are

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the ECC-40’s (3) the rectifier is the GZ-

34. Best parts are used as in the KL-403.

The KL-408a:

This was an amplifier built for smaller cinemas, and it is not on par with the models mentioned before, w h i c h does not mean that it does not sound good.

It sounds pret ty close t o the Mara n t z

Model 8b, and it is a matter of taste (as always) which one sounds better. There are two inputs which c an be used, a 500

Koh ms unba lance d and a balanc ed 3

Kohms using a very good permalloy input t ra n s f o r m e r. A g a i n , this amp sounds best when the EL-34’s are triode connected as described before. Sadly the C’s in the PS are electrolytic types, but at least of good

Siemens or Bosch quality. Check them and if you can, replace with MP’s. The rectifier is again the GZ-34. Build quality is otherwise on the same level as the others.

Now we come to the most sought after KLamps, the KL-203/204 and the later KL-V-

410 amps, which are so called “ R e s e r v e

Ve r s t a r k e r ” which means amps for emergency. Well, they are by no means cheaply built amps, only the power output is low, as they are single ended pentode amps (F2a11

SE) and produce therefore only about 7 wa t t s, but they are very, very clean wa t t s.

But these amps are overrated! They are not on the same level as the others with the exception of the KL-408a, which are outperformed with more attack, clarity and

“being there”, which is typical for single ended designs.

We finish Part I with the KL-5418, w h i c h wa s m ade by the Austrian branc h of

Siemens (called K l a n g f i l m there as well).

This branch produced some very remarkable units, for example the late “ E d ” t u b e was made there (a famous European triode, the industrial version of the AD-1!) as well as an ultra rare speaker called the Klangfilm

“ E u r o n e t t e ” , a full range wooden/textile tractrix horn (not to be mixed up with the prewar “Euronette” power amp).

This amp uses again EL-34’s (ultra l i n e a r ) and triode connected it sounds as good as the KL-502a. It uses a rare rectifier called the Z2c, which is again an industrial tube like the Ed, is totally different in its design approach to the German power amps. Most parts are Austrian made, and it is necessary to change all the orange coloured 100 uF electrolytic C’s as they are prone to be dried out.

KL-401a —shown without tubes

Austrian-made Kl-5418— Shown without rectifier above

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