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Einric 1st July 2012 03:03 PM

Simple P-P Rectifier
 
1 Attachment(s)
Getting my orders together for my tubes and I am wondering about using one of these "Potato Masher" rectifiers.
Would they be suitable for this application?
I think they look cool.

JAN-Cetron 5R4WGB

akimmet 1st July 2012 07:05 PM

A 5R4 will work just fine if you lower the value of C1. The 5R4 datasheets mention a max of value of 4uF (4.7uF is ok).

The 5R4 is very rugged and would probably survive 47uF, but it is pushing it.

Beware, a 5R4 has the most voltage drop and sag of any compatible 200mA (or more) full wave rectifier.

Einric 2nd July 2012 02:00 AM

The higher voltage drop would just mean I should look for a 310-0-310 transformer huh?

What is with the "sag" is it a bad thing?

A smaller C1 will be cheaper, or maybe I should spring for a special one.

Davec113 2nd July 2012 02:24 AM

Quote:

Originally Posted by Einric (Post 3078672)
The higher voltage drop would just mean I should look for a 310-0-310 transformer huh?

What is with the "sag" is it a bad thing?

A smaller C1 will be cheaper, or maybe I should spring for a special one.

Sag is a small dip and equal rise in the rectified DC voltage at the frequency of the AC voltage. Not sure if this or a much lower C1 would be a good thing.

akimmet 2nd July 2012 02:36 AM

The transformer specified (300) is way too close to meltdown on some new EL84 tubes. Lowering the voltage some using a different transformer (280) or rectifier (5U4 or 5R4) is a good thing.

Voltage sag is caused from of the internal resistance inside of the tube. When more current is drawn the voltage drop of the rectifier will increase. The most noticeable affect is poorer low frequency response.

Voltage sag in a hifi amplifier is a bad thing in my opinion. However, some audiophile people will disagree.

I recommend using a 5AR4 for best performance with a tube rectifier.
I haven't had any problems with new Sovtek 5AR4 tubes so far.

If you end up using a 5AR4 or 5U4 use 33uF for C1, otherwise use 4.7uF for the 5R4. 47uF is a bit too much for some new 5ar4 tubes to handle.


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