All rights of photos and text reserved. Usage of photos or text from my blog on other websites or for any other purpose only with prior permission. If you want to use any material from my blog please contact me by email.

Saturday, October 20, 2018

The Differential 46 Amplifiers


In a recent post I announced the development of a differential push pull amplifier with the 46. The first set of mono blocks with this configuration is finished.

It also uses a pair 46 tubes in differential configuration as driver.

Layout and chassis style is the same as used for the single ended 46 drive 46 amps.

4 type 46 tubes per channel providing almost 3W of  '46 bliss'.

Here both mono blocks together.

They retain the character of the single ended 46 amps but with a bit more grunt and they are leaning more towards the neutral side.

Chuck Michlin who just visited described the sound as very palpable.

Above a photo together with a new set of single ended 46/46 amps with all silver transformers. More about those in an upcoming post. Stay tuned.

Best regards


Tuesday, October 16, 2018

Tube of the Month : The 19DE3


For this month I pulled a rather odd TV Damper tube from my collection, the 19DE3.

I just came across a box labelled 19DE3 in my tube storage and opened it since I was totally unaware that he had these.

I first thought it is just another odd heater voltage variant of a 6.3V type. As there are the 19AU4, 17AX4, 25AX4 and many others. But when I looked it up I realised that there never seems to have been a 6DE3 and this type was only made with a 19V / 0.6A heater for use in series heater arrangement and obviously for Damper service in color TVs. It has the late 12 Pin Compactron base and the cathode connection is brought out to a top cap. Color TVs required some hefty Damper diodes with high current and voltage capability. The 19DE3 can deliver 350mA steady DC current and can handle peaks of just over 1A. With that it is similar to the 6CG3. Like other TV Dampers this diode is perfectly usable for rectification although the tube manufacturers never advertised their Damper tubes for that. They have a slow heater warm up which brings up the voltage nicely and can deliver large currents. This is usually combined with a rather low voltage drop which in case of the 19DE3 is extremely low and comparable to mercury vapour rectifiers like the 866A. See the plate characteristic below.

Many tube amplifier builders have realised the usability of TV Dampers. So the usual Octal types with 6.3V heater have become a bit scarcer compared to years ago. But they are still easy to find at reasonable prices.

If you are on an extremely limited budget or if you need them in larger quantities, such compactron dampers or those with odd heater voltage are still sold for next to nothing and tube dealers are happy to sell them in volume at discounts.

So if you plan to do a small series production of tube amplifiers or if you need current and voltage capabilities beyond those of the classic rectifiers, TV Dampers are the way to go.

They had been produced in millions which enabled the tube manufacturers to sort out all potential weaknesses and they were designed to withstand the stressful operation in TV sets without frequent failures.

Let's have a look at some 19DE3 in detail.

This one was made by Sylvania.

The top cap:

The 12 pin base:

Some close ups:

Despite being a mass market product a solid construction.

Another Sylvania in later box, after Sylvania was acquired by Philips:

General Electric 19DE3:

Slightly different construction compared to the Sylvania above.


Again different in construction, so no cross branding with these.

That's all the different 19DE3 tubes I have.

Now let's open one and inspect the internal construction.

Glas removed:

The top showing the heater inside it's insulation spiral within the pate:

Bottom side:

Getter ring:

The heater:

Heater wire removed from the insulation spiral:

The cathode:


And lastly a 19DE3 with the heater lit up:

Close Up:

I hope you enjoyed the presentation of yet another TV Damper in the Tube of the Month series.

Best regards