Tube rectifiers for Dummies

[bigjppop]

So I'm just getting started putting my Simple SE together and I've fallen victim to the addiction that is buying tubes on ebay. I'm currently scouting for rectifier tubes and discovering there's a million of them out there.

I know that Tubelab's website mentions a few specifics that can be used, and I know most of the threads on here mention the 5AR4 as the best tube for this particular circuit but nice NOS 5AR4s don't come cheap!

There are a ton of "odd ball" rectifiers that seem to go for super cheap, even for old NOS stuff so I'm thinking I'd like to try a few of them out. My only concern is doing irreparable harm to my amp.

So, instead of posting every five minutes with "will this tube work in my amp" I'm hoping someone can shed some light on what to look for in a tube spec sheet that will tell me go/no go for a particular tube. Is there a certain value I should be looking for?

Thanks in advance for any help.

[316a]

Originally posted by bigjppop

I know that Tubelab's website mentions a few specifics that can be used, and I know most of the threads on here mention the 5AR4 as the best tube for this particular circuit but nice NOS 5AR4s don't come cheap!

There are a ton of "odd ball" rectifiers that seem to go for super cheap, even for old NOS stuff so I'm thinking I'd like to try a few of them out. My only concern is doing irreparable harm to my amp.

Japanese 5AR4/GZ34 are still available , cheap and very good quality . 2nd hand Mullards can also be sourced fairly inexpensively and literally last forever . As for oddball rectifiers , I'm very partial to PY500A TV dampers , the main issues with these are two are required , the 42 volt heater and topcaps

316A

[kmtang]

5U4 rectifier tube is great for most of the tube amps that are commonly available.

Johnny

[Tom Bavis]

5V4 may be a good second choice, though it's rated a bit lower (175 mA - should be enough). It can be found in the "ST" style (shouldered bulb) if you like - look for 5V4G. 5U4 draws 3A for the heater, so make sure your transformer is rated for that. 5U4 or 5R4 might be a good choice if your voltage is too high. Don't try 5Y3, 5Z4, 5W4 - ratings are too low.

I doubt you'd have any problem with Russian or Chinese 5AR4s in this amp, as it doesn't push them as hard as many commercial designs.

[boywonder]

As mentioned, the 5U4 tubes will work in the simple SE, although they are directly heated (will warm up faster than the indirectly heated 5AR4) and will drop more volts than a 5AR4. The 5U4 family can handle more forward current than the 5AR4. They are pin-outs are the same, and can be handy if your B+ is too high and you want to drop it without soldering. 5U4's are dirt cheap also.

The mullard GZ37 is also a replacement for a 5AR4, but they are expensive and slightly rare. IIRC, these take more filament current than a 5AR4.

Check out the TDSL tube data pages on www.duncanamps.com, when you input a tube, it gives lots of equivalent and "close to equivalent" tubes.

http://tdsl.duncanamps.com/tubesearch.php

[andyjevans]

Check out damper diodes - very cheap and very good. I use two 6DT4 as a rule, but there are several equivalents like 6AU4, all with different power ratings. They're very robust, and work off ordinary 6.3v filaments.

http://www.classiccmp.org/rtellason/tubedata/6DT4.pdf

andy

[Robert McLean]

what to look for in a tube spec sheet that will tell me go/no go for a particular tube. Is there a certain value I should be looking for?

Look for Steady State Peak Current, and for Peak Inverse Voltage. The higher those numbers are, the better. But as for the values you actually need, and what is overkill, that depends on the amp you are trying to power. What current will it draw ?And the type of rectifier circuit you are intending to use, Bridge vs Full Wave etc. What peak reverse voltage will the diodes see ?

If you want to replace 5AR4 then you want to compare candidate substitute's max current and PIV to the 5AR4 max current and PIV which according to GE data sheet are 825mA and 1700 V.

When comparing current ratings make sure you are reading the same kind of current rating on each spec sheet, there are several ways of expressing max current.

[CharleyW]

Why not 5R4 "potato mashers"? Cheap, very rugged, and very available.

[chrish]

I have been using a standard Sovtek 5AR4 for over a year with no problems. Not expensive.

Chris