Help! 5755 or 420A tube as ecc83

[wenig watt]

Through a series of convoluted circumstances, I got my hands on many of the above-mentioned tubes for little money and an SRPP tube phono stage with six double triodes. With the help of two adapters I was able to replace the input tubes (ecc83) with a WE 420A. It sounds really very good!
Now I'm thinking about converting my China clone of a Jadis preamp that runs with six ecc83 to this tube. Does anyone know the necessary changes to the tube sockets? If I knew, it would be a nice little Sunday task. Otherwise I would have to spend hours measuring on the adapter and drawing pictures to find out...
Any help would be greatly appreciated! The adapters do not fit in the case...

With best regards

Arndt

[simon]

I hope that is easy to understand

[simon]

 1, 4, 5, 9 pins are the same.
 2 => 3
 3 => 2
 6 => 8
 7 => 6
 8 => 7

[wenig watt]

Wow!
thank you very much!! That was fast and comprehensive.
I`ll report.

Best regards

Arndt

[be.audiophil]

Neither 5755 nor WE420A are direct replacements for the Ecc83 - most obviously the pin layout isn´t identical, but there´s more to look at



Ecc83 datasheet





5755 datasheet

You´d need to calculate proper values for anode, kathode and grid resistors first and have a look into what current the heater will need and whether this current can be delivered by your actual used schematic without any stress.

Rolling tubes without doing that of course will produce some kind of sound output, but it´s not feasible to rate this as beeing worse, better or sounding anyways interestingly, because You might even add a hughe portion of distortion to the signal with improper tube rolling ...

[simon]

Yes Rolf, you are right:
Heater current of 5755 / 420A is 0.36 A  vs  0.3 A for ECC83 (for 6.3V) i.e. 20% more
 fro each tube !  For long and good working of  whole amp, with "new" tubes,
must be checked power supply for heaters ! It is more important when is with DC heater !
For 3 tubes , this (maybe) will be too much current with "new" tubes !

Others: plate volatge and current, grid voltage must be checked of course,
and if they are out of "usual" , must be changed working points of tubes.
By the way, SRPP is more "comfortable" schematic for such of chages  ,
and if lower amplification factor with new tubes is ok, then o.k.  .

[wenig watt]

Well,
nobody says they are the same tubes.  They don't have different names by chance... However, many circuits and devices are designed with sufficient backlash. Besides, tubes are very tolerant and even ecc83 often doesn't mean ecc83. My friend Bernd has been designing tube amplifiers for more than 40 years. If I am not convinced by the result, he will look into it and adapt the circuit. The good thing about the WE tubes is that the systems are quite similar without so-called matching. The Chinese tubes with which the device was delivered have a clear quality problem that is not due to the circuitry and other components. Good ecc83s are ridiculously expensive. Hence the tube replacement approach.
A preamplifier with six double triodes has luxury problems anyway. Both the phono and the high-level preamplifier each have six double triodes...
Vlad's tube phono is far more economical and still sounds very good. Different distortion spectrum of course, but if you only look at measurement data, you don't really need tubes and turntables.

With best regards

Arndt

[niclaspa]

I had a glance at the Jadis circuit and the tube data.  The tubes operating points could change quite a bit with the new tubes.  Let your friend measure them before and after the change to verify that the new ones are feasible.

NOS ECC83s are expensive.  I have used Soviet 6N2P instead and been pleased with the result.  The electrical characteristics are close and the pin configurations are the same except for the heaters.  However, 6N2P can only be run on 6.3 V so you would need to change the heater supply in the Jadis.  I'm sure Bernd can help you with that.   

[wenig watt]

Thank you Niclas!
The before measurement is a good tip.

With best regards

Arndt