EL36 / 6CM5 TESLA tube tubes store. TESLA EL36 / 6CM5 high power amp tube. Customers who bought this product also purchased. Class, Va, Vg2, Vg1, Ia, Ig2, Zout, Pout, THD. Line output, , , , B ( idle), , , , 36, 1, B, , , , , 38, 3,, , He offers a 6CM5/EL36 based 2 x 22 Watt Stereo Class AB1 triode amplifier, the fuss was about tube sound, while their solid-state amp’s are being repaired.

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Really nice reverb, 2 x 12 speakers, uses two EL36 output valves, about 40Wcombo style, but not open back – the speakers are fully enclosed. Beam tetrode, used in output stages of line scanning of TV with 0 deflection. I simply re-wound mine to 40 volts. The other method is of a much higher impedance, and also tends to sag as the main HT winding drops with currant drawn. The down side again is low output power in the order of 3 Watts RMS.

A 6AQ5 or 6V6 will give nearly double the output power for less than half the thbe current! Pushing the EL36 family of tubes this hard may reduce their lifespan? As I am able to design and wind my own transformers I decided to do the experiments with separate power supplies for now, so I could play around with voltages and try and achieve the desired results; the end idea being to rewind the mains transformers with the voltages I ended up with.

I am now ready to re-build all 4 of these amplifiers as and when, and then eventually display them on this website. Interesting they were, HiFi they weren’t! These had all cost me a fair bit of money and I still needed more!

Well, firstly, in this mode it sounds a lot better than a single-ended 6V6 or EL34, and better even than a single-ended 2A3, and secondly, its low cost.

The screen decoupling capacitor is connected from G2 to cathode rather than hard to ground because the cathode is not at AC ground on account of the negative feedback into the cathode.

BoxVilnius, LT, Lithuania. New Zealand followed the series heater designs to a much greater degree than here in Australia. Unfortunately the 12AX7 is highly revered by audiophiles and some brand names attract unusually high prices when sold at on-line auction. Also, you can’t simply plug in EL34’s, this won’t work. Very little is published on this, so take heed! This is with V on the anode and a 5kOhm load, so it compares favourably with ‘proper’ audio valves like the 6AQ5 and 6V6.


So, that’s why I set the P d line to 15 Watts on this sheet. As with all electronic experimentation, there are components hanging out everywhere. So, yes it can be done, but it’s terribly inefficient when you consider that the heater current is 1. In reality the actual power to the voice coil will be less due to transformer losses.

6P31S / 6P31C = EL36 = 6CM5 tube. Beam tetrode

The second characteristic that I found problematic was that when using a fixed bias supply the grid voltage was critical within a few Volts, from trying to set an anode current of 50mA to being completely cut-off. Philips got around the height problem by mounting them horizontally with generous ventilation. Especially since the EL84’s were used as the drivers for the EL36, and so must have had their part in the signal shaping. One of the photos shows a re-wound power transformer with the extra screens grid 2 winding on two tags previously used for the 20 volt bias winding.

The output transformers were made in in Sydney and the power transformer and chassis is a new one by T.


The screen-grid voltage is set by the 6CG7 cathode follower; about 25V is what is required for correct 6CM5 anode current. Recently, I’ve further been privileged to have highly esteemed South Australian designer Graham Dicker offer the following most valuable and extensive research report. This and the required Ohm speaker transformer don’t tend to match in well with other valve circuitry and parts availability i.

If not, you will need to re-think this; possibly with a very small, few milliamps 40 volt transformer to give the higher needed voltage. The scope photo shows it just clipping at Enhanced triode mode is harder to drive, but also much more linear than conventional triode mode. These were brilliant and actually were the best results of all I tbe tried from a power point of view.


The anode is DC coupled into the grid of the cathode follower by a voltage divider which sets the 25V on the cathode. Click on the image to enlarge and view the circuit properly. The one referred to in this text primarily, is that with a top-cap anode connection. This makes a nice simple power amplifier.

It was so totally different from my EL84 amp, comparing mono to mono. I have done this many times before with other valves with great success; try an and you will never use any other method again. The other thing with TV valves, particularly the European ones, is they are good performers with low voltage anode and screen.


As I’ve mentioned before, initial attempts at getting a 6CM5 working in the conventional triode or pentode circuits only provided about 2W. This was starting to look good! The transformers are mediocre at best, though.

The one I have here actually produces 36 watts quite easily before clipping! I have brought the new 40 volt bias winding out on fly leads, no more tags left! The pot is simply adjusted for a total current consumption of 50mA, or 45mA for the 6CM5 anode.

In theory this is not a practical thing to do as this would allow the pot to completely shut down the bias of the connected tube! But after quite a bit of experimentation with other output valves I used 6CM5’s, based on the large amount of information now available on these dime-a-dozen valves. Lots of secondary taps for various impedances, including 70V and V line driving windings.

Philips used them in PA amplifiers as well. The sound is clean, accurate, detailed, emotionally involving, with the typical smooth treble and precise bass with a warm midrange. I believe negative feedback gives the amplifier a substantially flatter frequency response, than otherwise would be.

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