rectifer tube question

[hebaton]

I am looking to experiment with different rectifiers in an amp. First : DO all rec tubes have the same pinout ? so they are "interchangeable " ?
I am thinking of trying a 5AR4 vs a 5u3 in the same amp to compare tone and sag characteristics. Will this run the risk of damaging anything ?

Thanks !

[martin manning]

I believe 5U4 and 5U3C are close, with 5U3C being a Russian version of 5U4. Here's a comparison chart for the more commonly seen rectifiers: https://300guitars.com/articles/rectifi ... rop-chart/

Pinouts are the same, but watch out for power tube bias change and rectifier filament current requirements.

[pdf64]

Make sure that the amp and its components can accommodate a rise in HT voltage. eg HT cap voltage rating.
If using indirectly heated types, eg 5AR4, make sure that the DC rectified output is taken from pin8 rather than pin2.
Sockets intended for directly heated types may have been wired 8 or 2.

[Turbojunkie]

I like playing with a 5R4-GYB in place of the GZ34....

[hebaton]

Thank you Poeple, this is very good information !

[hebaton]

I like playing with a 5R4-GYB in place of the GZ34....

Went looking for some, they seem rare and expensive. Do you know a good source for them ?

P.S. tryed to send you P.M. but they seem to get stock in my outbox and never sent...

[Stevem]

You might want to play around with something like this if you have room for the two 25 watt resistors.

The diodes handle most of the current load, yet you still get sag, in fact with this you can run a 5Y3 where only a 5AR4 or 5U4 could be used current load wise.

It also allows a higher limit as to the Uf value of the first filter that the DC dumps into.

Also note that if the tube blow’s at a gig like they do at times all you have to do is yank the tube, replace the fuse and then your playing / running on the diodes just fine!

[pompeiisneaks]

I like playing with a 5R4-GYB in place of the GZ34....

Went looking for some, they seem rare and expensive. Do you know a good source for them ?

P.S. tryed to send you P.M. but they seem to get stock in my outbox and never sent...

They're not 'stuck' in the outbox. Since every email app ever means that the email is not sent, I still don't get why phpbb decided instead that this was the 'default' behavior to tell you 'the user has not yet read your PM' It's sent and sitting in their inbox, they just haven't logged in to read it yet.

~Phil

[pdf64]

You might want to play around with something like this if you have room for the two 25 watt resistors.

The diodes handle most of the current load, yet you still get sag, in fact with this you can run a 5Y3 where only a 5AR4 or 5U4 could be used current load wise.

It also allows a higher limit as to the Uf value of the first filter that the DC dumps into.

Also note that if the tube blow’s at a gig like they do at times all you have to do is yank the tube, replace the fuse and then your playing / running on the diodes just fine!

That all seems to be hypothesis / assertion; is there a technically valid reference, or any actual measurements, to back things up?
eg I suspect that the solid state diode and resistor current path won't take much load off a 5AR4, so an excessive reservoir cap value could cause its peak anode current to be exceeded.

It seems to me that a better use of resistors and diodes would be to protect the valve rectifier anodes, ie in series with them.

As it is, the valve rectifier could short anode to anode, hopefully taking out the mains fuse before the PT fails.

[Phil_S]

This is an interesting topic, but I'm not sure we're addressing the OP's question all that well, and that is because he didn't really say what his goal was beyond experimentation. To me, this looks like a case of stirring up the stew to see what comes up from the bottom. It is my view that experimentation is generally better when testing a hypothesis or when seeking a particular result.

It seems to me that the problem is that introducing various tube/valve rectifiers into an existing amp isn't really a great idea unless totally compatible with the existing circuit. If the goal is experimentation, then create an experiment. Build an amp as a test rig with multiple rectifier sockets which will allow a simple approach to the appropriate configuration for different specs and pin outs. It may be necessary to provide for some switching in/out of power supply caps to maintain a configuration that is appropriate to a particular rectifier.

All this business with adding diodes and risk of too much capacitance seems too complicated to me. I'm not suggesting it won't work. I'm suggesting it's too much soldering and has the risk of getting confused. I keep thinking that it is always better to get the right tool for the job at hand. Just my 2¢. Carry on. Good luck!

[thetragichero]

thought just popped into my head about adding a tube rectifier to a traynor yba1 (which i believe is the poster's original intention): does the power transformer have a center tap on the ht winding? if i remember mine correctly it did not as it used a bridge rectifier. no center tap would mean no ability to use full wave rectification (your ht would have no ground reference)

[martin manning]

http://www.valvewizard.co.uk/bridge.html

[hebaton]

Hey guys, This is getting way out of my initial enquiery, I just want to get "some" sag happenig so the amp feels somewat "looser"
I am adding a tranny for the 5v supply and will try a 5AR4 to start...
ALso plan to make this switchable between SS and TUbe REctification. Seems to me several existing amps have this feature...

[martin manning]

I just want to get "some" sag happenig so the amp feels somewat "looser"

If that is the case, you could just put a power resistor between the rectifier and the reservoir capacitor to get a feel for the sag effect.