[Mariusz]

Hi tube luvrs

Let me get to the point-
Can I swap 5V4 with other tubes?
For exp: 5U4 etc.
It ofcause it's a rectifier tube.

Thanks in advance

PS
Preamp that uses that tube was custom build and I do not have much if any info or details about it.

[Quiet Earth]

Some preliminary data from the duncanamps tube pages :

5V4 Ratings
Vh   Ih   VaMax   IkMax   Notes
5.0   2.0   PIV=1400V   525 Ia pk   Tube drop = 25V @175mA

5U4-G Ratings
Vh   Ih   VaMax   IkMax   Notes
5   3.0   PIV=1550V   800   Tube drop = 44V @ 225mA DC

One difference that you can see is that the 5U4 needs 3A for the heater current. The 5V4 only draws 2A. So, your power transformer needs to be able to supply that extra amp of current without freaking out.

There may be other significant differences, like the maximum value of capacitance that is safe to use with it, the voltage drop, etc. Maybe someone else can jump in and help with that. I personally don't like to substitute tubes unless I'm dead sure that it is safe to do for the long run.

The data page for the 5V4 says its only "equivalent" is the CV729.

http://tdsl.duncanamps.com/show.php?des=5V4

[Mariusz]

Thanks
 

Mariusz

P.S
You wouldn't happen to know some worthy recommendations?

[Quiet Earth]

I'm not familiar with that particular tube Mariusz, I'm just being cautious. Hopefully someone will stop in and shed some light on alternatives.

[Mariusz]

Thanks Quiet Earth
Any info will help me figure out what am I dealing with.
Interestingly......while fallowing the links and related info on the web, I came across Cary Audio SLI 80 integrated amplifier which uses CV729 as a rectifying tube. And 5U4 as option. So, if CV729 is in fact compatible with 5V4 the 5U4 should be as well?.......or there is some grey area and explanation?

Mariusz

[Mariusz]

Oh ..... here is the link:
SLI80pdf

[Quiet Earth]

I saw that link too. But I don't know what's inside the cary to allow the substitution. BTW, I'm not saying that you can't sub, I just don't know if there will be a long term issue or not. Arching or sparks at turn on would be an indication that the tube is having a difficult time, even if everything else seems to be OK.

I'm probably getting in over my head, but I like these kind of threads because we can learn a lot.

I guess what you need to know specifically is what is inside of your pre amp. Can you identify the power transformer part number and the value of the first capacitor after the rectifier?  If you can, then maybe you can figure out if a 5U4G will work. A 5U4GB would probably be a safer bet, because it can handle a larger capacitance value for the first cap after the rectifier.

[Mariusz]

I'll give it a shot and take some pictures.
(tonight or tomorrow)

From your experience -is there any improvement/benefits in rectifying tube rolling?

Mariusz

[Mariusz]

Quick shot - guts & other info later

[JohnR]

5U4 has a 3A filament. If your power transformer only has a 2A-rated filament winding then a sub may not be such a good idea. Also, it's directly heated so turns on much faster. Personally, I wouldn't... A 5R4 would be a safer bet.

[Mariusz]

Would pictures of the insides help ??

[Quiet Earth]

is there any improvement/benefits in rectifying tube rolling?

There can be. And as you would expect, the amount of improvement (or change) can depend on the tubes the rectifier is supplying power to. Synergy is at play. For example, my JJ 300Bs actually sound better with a cheaper 5U4GB instead of a costlier 5U4G.

The only rectifiers I have rolled are the 5U4G types and 6X5s. In my power amp, my favorite 5U4G is a 1943 National Union. It provides a big, comfortable, earthy sound. Sylvania VT-244 (a military number for 5U4G) is also very nice. I've had good luck with some 5U4GB straight bottle types too, like Raytheon black plate. The Phillips, GE, RCA, and Sylvania 5U4GBs don't really sound any different to me, and none are as good as some of the ST shaped 5U4Gs. They're not bad, but just not as big, full, and earthy. Right now I'm using some Russian no-name 5U4Gs that I got on the cheap. I like them. I believe they were made for Sovtek, but never silk screened.

I learned a lesson in tube substituting with the 6X5 rectifier in a tube DAC. Everyone recommended the Bendix 5852 as the ultimate 6X5 substitute, so I purchased one. Indeed it did sound better. One early morning I realized there was a noticeable hum coming from the DAC (not through the speakers, but from the transformer of the DAC).  I was worried that something might be wrong. Later, I figured out that the circuit in the DAC was not really designed for the extra heater current and capacitance requirements for the 5852. I went back to using regular 6X5 rectifiers and the hum went away. Maybe there was no problem with the power supply working extra hard, but I feel better about reducing that stress for the long run.

Since your pre is a home brew, it could be that the 5V4 was whatever was on hand at the time of build and a different tube type is totally suitable. The transformer sure looks like it could handle it. Just check the capacitor value to make sure that it's not too much for a 5U4G at turn on. I think that 30 to 40 uF is the maximum limit. Sometimes there will be two capacitors in series, which will be half of the capacitance value listed on the caps. (I.E. two 68uF caps in series provides 34 uF at twice the rated voltage.)

Maybe one of our more experienced tube builders can chime in and shed some more light . . . . . 

[Quiet Earth]

Personally, I wouldn't...

Me neither unless I could see it for myself.

If you're not sure what you're looking at, you could take it to a local tech and have him take a quick look at it. It shouldn't take more than a few minutes with the cover already off and he may not charge you anything for the advice.

[Mariusz]

Me neither unless I could see it for myself.

If you're not sure what you're looking at, you could take it to a local tech and have him take a quick look at it. It shouldn't take more than a few minutes with the cover already off and he may not charge you anything for the advice.

Not sure if it helps but here are some pics.
There are no markings of any kind on the trannies.

[Quiet Earth]

It's hard to be sure from the pics even if I were a tube expert, which I am certainly not. It looks like that big yellow cap is attached to one of the rectifier pins and it is the first capacitor after the rectifier. It looks like 100uF (written 100MFD) which is kind of high for a 5U4 and even 5R4. I can't tell what the resistor value is, is that 220 ohms? Since I am in over my head I would leave well enough alone and roll different brands of 5V4s.

Anyone else?