Philips 5R4GYS Rectifier

https://dynacotubeaudio.forumotion.com/t2391p75-that-good-old-rectifier-sound

The tubes start out strong, but get progressively weaker with minimal hours, until they can no longer bias up the amp. I dropped a note to Upscale Audio, and they're aware of the problem.

Not sayin' don't buy them - it's your call. Just sayin' , as they say ...

~~~~~

These work in a VTA ST-120? Any reviews? Real world experience on these amps?



I see they get some good credits here and there, but wondering how much of a match they are for the GZ34 ...
Supposed to have real good bass and a very nice warm midrange ...

But mostly I think one would look sooooo cool with the TungSol KT120's ...  

Found the spec sheet for the tube type if that helps.



http://www.mif.pg.gda.pl/homepages/frank/sheets/049/5/5R4GY.pdf

Not sure if this is a slow start or not. Maybe add a CL90 inrush limiter on the AC tap?

woooooOOOOOOooooooOOOOOOOOOooooooo ..

(It's quiet ... too quiet)

I take this as a no?

Hey, thanx ... long as it won't blow anything up, I may just pick up on one just to see what happens. Depends on how "slight" slight is on the power drop. I should have plenty to spare, and always have other options. I'm thinking the lower voltage would tend to prolong power tube life also? I'd consider that a good thing.

I do like the looks of that big bottle though. Won't get lost in the redwoods otherwise known as the TungSol KT120's. Yeah, I know ... looks shouldn't be a factor, but ...

I like big bottles, and I don't know why
Them big glass bottles kinda catch the eye

Appreciate the comparison sheet. One thing caught my eye ... what's the difference between a 5DA and a 5T base? Be nice if the tube lines up properly with the socket connections ... assUming it even fits?

Reason I ask is Parts Connexion is running a special on em right now.

I was thinking that might have been the issue in a post long ways back about tubes falling out of sockets when flipping the amp over for service. I do know there's fat pins and skinny pins. What I don't know is if that's true of these varieties.

Another brainfart that may or may not make sense in the real world.

My AC power runs high at around 122.5 average per my Kill-A-Watt doing random tests over a couple weeks. It's my understanding these amps like to see around 117vac, but not more than around 120vac average.

Do ya think the expected voltage drop of the 5R4 might help to buffer that? That'd be great - no playing with a variac ... I got one, but I'd rather not.

Tube came in yesterday ... a lesson in relativity ...



For those wondering why I was spacing the rectifier out as much as I was on the chassis design ... I'm just hoping I spaced it enough! Sucker's HUGE! Looks right at home next to the TungSol KT-120s.

Side getter too, so that makes it a clear top. Bob should be able to see the glow in Masscanuchets ...

Parts Connexion was running them at $40, which seemed reasonable. They also had a NOS Marconi 12AU7 which I've seen good reviews on. It's a medium mu and I plan to try it in the center position. Not sure if it's a flasher or not. Fun fact - Brimar are British Marconi, and those seem to be in demand also. This one is a true 12AU7, not a 12AU7A, which would put it mid sixties at the latest? Don't see any date codes.

sKiZo wrote:Tube came in yesterday ... a lesson in relativity ...



For those wondering why I was spacing the rectifier out as much as I was on the chassis design ... I'm just hoping I spaced it enough! Sucker's HUGE! Looks right at home next to the TungSol KT-120s.

Side getter too, so that makes it a clear top. Bob should be able to see the glow in Masscanuchets ...

Parts Connexion was running them at $40, which seemed reasonable. They also had a NOS Marconi 12AU7 which I've seen good reviews on. It's a medium mu and I plan to try it in the center position. Not sure if it's a flasher or not. Fun fact - Brimar are British Marconi, and those seem to be in demand also. This one is a true 12AU7, not a 12AU7A, which would put it mid sixties at the latest? Don't see any date codes.

Did you ever compare this rectifier to the SS Weber and any others you have used and can say how it sounds by comparison?

Thanks!

Still working on building the amp ... but you'll be the second to know! :-}

That is a large voltage drop on the 5R4Gs .  This rectifier will get extremely warm as you will be pulling near the maximum recommended current limit just idling in the ST-120.  50V drop x 250mA = 12.5watts plus another 10watts for the heaters.  But you'll never know until you try it and the amp layout well spaced.  Keep that WZ68 handy though for the KT-120s!

The 5R4 is too low in current capability for an ST-120.

I use it on a Mark II with larger-than-normal power supply reservoir capacitors, to good effect. Still, were it to be measured at full power on a steady-state basis, it would fall short. But these amps only operate from 100Hz up and steady-state full power operation is rare in real music.

Yup to all of the above. Mulled that over before getting the tube. Ran it by Bob, and he had the same concerns, but feels the amp can handle it easily enough as there's plenty of reserve in it. And ya ... a stock Dynaco would certainly have issues.

As said, extra heat shouldn't be an issue ... that big bottle should make for a decent enough radiator by itself. I'd worry about whether the stock chassis would give it enough room to breathe. Power supply should be more than strong enough to handle it, and if I'm reading it right, the voltage drop should actually help protect the power tubes, which won't be working all that hard anyway due to the amp not being designed to use the full output of the KT-120's.

Put it all together, and it should make for an interesting experiment. I don't plan to put it in until after I've put the amp thru it's paces, and then keep a real close eye on it. Mostly, I just like the look of the big bottle, and the fact that it was half the price of a decent GZ37 helps.

One way to find out ... but I expect it'll be a while ... the build just took a step backwards as I found a light dusting of rust dust on the heavy iron, so I wasn't going to get away with a couple coats of wax. Fortunately, I hadn't gotten around to wiring yet, so got those out and painted the other day. I'll let those cure a couple days. Sometimes it helps to be slower than a turtle on ludes ...  

Skiz (and Bob L.) are right as usual. Over the long-haul, these things suck in a VTA amp.

someone asked the difference between the 5DA base (5AR4) and the 5T base (most all other rectifiers).
The 5DA actually has a cathode. All the other rectifiers just have a filament that also acts as a cathode.
Same exact pin-out, in a 5DA the cathode is tied to the filament at pin 8.

Bob Latino wrote:deepee,

If you want to get more bias range when using 5R4GYS rectiifiers in your M-125's, pull the jumper wire out of R39 on the driver board and put a 2K to 3.5K (1/2 watt is fine) resistor in there. This should allow you to have more range with the two bias pots using the 5R4GYS rectifiers. It should also allow the use of a GZ34 tube rectifier or Weber WZ68 solid state rectifier.

Bob

Bob, hadn't thought of that. Thanks. No harm done running the KTs at below optimum 1.2, is there?

deepee99 wrote:

Bob Latino wrote:deepee,

If you want to get more bias range when using 5R4GYS rectiifiers in your M-125's, pull the jumper wire out of R39 on the driver board and put a 2K to 3.5K (1/2 watt is fine) resistor in there. This should allow you to have more range with the two bias pots using the 5R4GYS rectifiers. It should also allow the use of a GZ34 tube rectifier or Weber WZ68 solid state rectifier.

Bob

Bob, hadn't thought of that. Thanks. No harm done running the KTs at below optimum 1.2, is there?

Ah, so THAT's why the jumper in on the bottom of the board ... and why there's the mystery R39 in the first place.

Have to make a note of that in case I have issues here. Thanx and a tip o'the hat for that.

Bob, Roy, Troy, Jim Mc., et. al,
I just did a Google search on tube and rectifier issues with Dynaco designs, blew my little tiny mind and long live David Hafler. (McIntosh never comes up, because I guess nobody wants to admit they spent a fortune on pretty blue meters and they still ain't happy).
Rectifiers are a bitch. Embrace that knowledge. Learn to love the fact that rectifiers are a pain and will get you talking to yourself late at night.
As Brother Bob Latino has suggested, though not in so many words, your relationship with a tube system is a marriage, not a shack-up.  You want to listen to sand, get solid state. You want to listen to music, well, prepare to dance all night.
Just to share my experiences with brother newbies, and I had a ham license for a good long time and do know the difference between a 6146A and a preamp tube . . .
Rectifiers suck. Did I say that already?
I never had a problem with them in the ham shack (KB7 GTO) lashed up to a Collins S-line set-up, but in audio systems they will break your heart. They blow up and go away without the slightest provocation.
Witness my yesterday's "listening to background music -- honest!" explosion of the latest Weber. The house went dark, a loud buzz ensued, well, you know the rest.
The Webers are cheap, but after you go through 10 of them or so inside of a year, they do get a bit precious.
Seeing snow on the nearby mountain passes, it was time for a tube-roll anyway. Out went the KT-120s and in went the McShane KT-88s. Out with the -120s went the Webers, replaced by those 6-foot-tall Philips rectifier tubes.
All was well, one supposes.
Except one of my brand-new $50 glow-in-the-dark Philips 5R4GYS wouldn't deliver any volts whatsover, dared John Flue to come up with a value, and of course I've lost the warranty paperwork issued by some coupon-clipper in Amsterdam.
End of story: After ploughing through my box of the big dark scary Philips rectifiers I found another one that could come off at 1.2 volts. So all is in balance as I play Chopin.
Until the next rectifier blows.

I've been lucky. I have blown all of ONE rectifier in all the years I've run tube audio (1966 to around 1975, then 1983 or so to the present). It was a Mullard GZ34 but since it was already in the Mark II that I bought as a junker in 1982 and upgraded into one of my current power amps, I'm not going to cry.

That one GZ34 failed two years ago. Guess my luck ran out.

I now use 5V4 rectifiers. They have slower startup than the 5U4 originally specified in the Mark II, and the voltage drop compensates nicely for higher line voltage and the beefed up power supply (choke and larger capacitors). They were also cheap when I laid in a supply of them, about $3 each, and I didn't even have to do THAT; I forgot about the supply from when I used Fisher 70A amplifiers, that used the 5V4 as stock. I never even dipped into that stash.

With the beefier capacitors in the modified Mark IIs and their being freed from extreme LF by subwoofers, the 5V4 works fine.

Howdy folks:

Newbie here.  I've read diligently through the thread yet I'm compelled to ask: soooo ... will these boss-lookin' 5R4GYS's work in a pair of Dynaco Mk III's?  And by "work" I mean no kaboom?

I love my lightly-modded Mk III's and they've been very good to me.  Yet the siren song of the big glass bottles is becoming too difficult to ignore.

Thank you in advance for your responses.

veloceracing wrote:Howdy folks:

Newbie here.  I've read diligently through the thread yet I'm compelled to ask: soooo ... will these boss-lookin' 5R4GYS's work in a pair of Dynaco Mk III's?  And by "work" I mean no kaboom?

I love my lightly-modded Mk III's and they've been very good to me.  Yet the siren song of the big glass bottles is becoming too difficult to ignore.

Thank you in advance for your responses.

No kaboom. Lower maximum output power due to more forward voltage drop causing lower B+ voltage. The filament draws only marginally more than that of the stock 5AR4. Probably more margin against failure under adverse conditions such as an output tube failure.

Howdy GP49!

Fantastic news! Thank you very much for that reassuring post. This is a great forum and a fantastic resource.

So, how about another one: in a haste, I bought a pair of beautiful coke-bottle Brimar labelled GZ34 (and underneath in parentheses "GZ32"), with the seller assuring me that these were direct replacements for the 5AR4. Well ... to put it charitably, I suspect he spoke in error.

Even though this tube's top line says "GZ34", I'm sure that the correct designation is the one in parentheses ( GZ32 ) which would make it a 5V4G, a directly heated tube, vs. the indirectly heated 5AR4. So this one is definitely a NO GO for the rectifier in the Dyna III's, yes?

Thanks again!

5V4 is indirectly heated. It is the 5U4 that is directly heated, and even it was used in the Mark II, the predecessor to the Mark III. But 5U4 has a higher filament current, and the Mark III's 6550s each draw 0.1A more filament current than the Mark II's EL34s; so between the two there will be more stress on the power transformer. Both the 5V4 and 5U4 have higher internal series resistance and will put out lower DC voltage.