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Friday, October 8, 2021

The ELROG ER5Z3 Rectifier Tube


Yet another addition to the ELROG family, the ER5Z3!

Admittedly this was an easy one since the 5Z3 is electrically equivalent to the 5U4 except that it has a 4 pin UX4 base.

After the introduction of the ER5U4G, it was a small step to add this tube to the portfolio.

Best regards


Monday, October 4, 2021

Stereo Single Ended 45 amplifier


below some photos of a recently finished 45 amp.

It is a stereo amplifier with the power supply integrated.

This represents my entry level in amplification with the 45 tube.

Tube rectification with two 6AX4 TV damper tubes. A pair of 6N7 as driver tubes is interstage transformer coupled to the output tubes.

All transformers and chokes, except the main power transformer reside inside the chassis.

The two trim pots between the output tubes are hum buckers to minimise residual hum from the AC heated 45s.

This enables a hum free operation except on extremely sensitive speakers for which I would recommend the DC heated version of the 45 amps. On my 98dB speakers no hum whatsoever was audible.

Best regards


Monday, September 27, 2021

Tube of the Month : The ECC88 / 6DJ8


This month I am presenting a 9 pin miniature (Noval) medium mu twin triode. Meet the ECC88:

The ECC88 is one of the more popular tubes among tube amplifier manufacturers and has seen some widespread use. For example some Audio Research preamplifiers use this tube.

With an amplification factor of 33 it is classified as a medium mu triode. The Noval base shares the same pinout with other popular ECC family tubes as the ECC83, ECC82, ECC81 or ECC85. The pinout is shown on the left. What makes the ECC88 stand out among the others is the rather high transconductance of 12.5 mS. As the prefix 'E' indicates it has a 6.3V heater which consumes only 300mA. For all technical parameters see the Telefunken data sheet. I never really used the ECC88 much in any of my own projects. For my applications the amplification factor was a bit too low or the plate resistance somewhat too high. Or the available output voltage would not provide the headroom I wanted. But that doesn't make it a bad tube. In contrary, if the parameters fit the application I would not hesitate to use it. The ECC88 was made by all the major European manufacturers and also came in industrial or rugged flavours with enhanced life time, tighter parameters and other improvements. These were called E88CC or CCa. The American equivalent was the 6DJ8 which had an industrial variant as well, called 6922.

As always we start with a look at the plate curves. Datasheet curves above and measurement of an actual tube below.

A very linear tube, which explains the popularity.

Since I never really used the ECC88 I did not accumulate a large stock of them. Above is all I have.

Starting with what is probably the most sought after version, the Telefunken E88CC with embossed diamond logo in the base.

Made at the famous Telefunken factory in Ulm.

Siemens E88CC:

Siemens-Halske tube in US military packaging:

E88CC made by Valvo:

And lastly a JAN 6922 made by Philips ECG:

And closing the post with a tube in operation:

Best regards


Wednesday, September 15, 2021

D3a LCR phono stage, landscape style


Here a few pics of a D3a phono in landscape chassis.

Technically the same as the phono in portrait chassis, just a different style.

Two of the capacitors on the power supply pick up the grey color of the LCR modules on the signal chassis as a special touch:

Pick the chassis style you like most for your own D3s phono or if you have a different idea, email me for a custom solution.

Any ideas which are technically feasible and allow to house all the parts needed will be considered.

Best regards