Philips 5R4GYS Rectifier

Got it! So 5R4GYS is about as risky as I should get with a 5AR4 replacement. Now I feel much better. Thank you very much!

Finally got around to plugging in the Phillips rectifier into the ST120 and can categorically state, without reservation ...

... it didna explode.  

~ ~ ~

All tests were made with three RCA clear tops for drivers and no change in the power tubes other than adjusting the  bias.

So far I've tried the SS WZ68 ... great overall sound with good impact, but it felt a bit ... sterile.

Next up was the Shuguang 5AR4 ... mellowed things out considerably, but boomy bottom.

The 5R4GYS seems to be a nice middle ground. Mellow, yet tightened up the low bass considerably. Only a couple sessions on it so far, and no idea about breakin, but I like it. If I had a complaint, it's not got much glow to it. Yeah ... important stuff, that.  

Big surprise was how far I had to turn the bias up to get it right. The pots were set to maybe 1 o'clock on both the 5AR4 and WZ68 ... they're now at around 3 o'clock with the Phillips tube. After a couple minutes, the bias was stabilizing at less than 30mV at the original settings. Good news is, the 50k bias pots have the range to handle them, and the power transformer isn't heating any more than normal. I checked the bias after an hour and it was holding steady. I would have expected a bit of drift from a new tube, but not complaining ...

sKiZo wrote:Finally got around to plugging in the Phillips rectifier into the ST120 and can categorically state, without reservation ...

... it didna explode.  

~ ~ ~

All tests were made with three RCA clear tops for drivers and no change in the power tubes other than adjusting the  bias.

So far I've tried the SS WZ68 ... great overall sound with good impact, but it felt a bit ... sterile.

Next up was the Shuguang 5AR4 ... mellowed things out considerably, but boomy bottom.

The 5R4GYS seems to be a nice middle ground. Mellow, yet tightened up the low bass considerably. Only a couple sessions on it so far, and no idea about breakin, but I like it. If I had a complaint, it's not got much glow to it. Yeah ... important stuff, that.  

Big surprise was how far I had to turn the bias up to get it right. The pots were set to maybe 1 o'clock on both the 5AR4 and WZ68 ... they're now at around 3 o'clock with the Phillips tube. After a couple minutes, the bias was stabilizing at less than 30mV at the original settings. Good news is, the 50k bias pots have the range to handle them, and the power transformer isn't heating any more than normal. I checked the bias after an hour and it was holding steady. I would have expected a bit of drift from a new tube, but not complaining ...

You want glow, for a bright-room situation may we suggest the Mullard GZ-33s NOS at $100 a pop (oooh, bad choice of words there). However, the ambiance of the Philips will grow on you over time, especially in the northern latitudes during winter months when the aurora borealis is not out. . .

The requirement to turn the bias control "higher" (as we know, what you are actually doing is turning the bias voltage on the grid so it's LESS NEGATIVE, to be precise) is expected because of the higher series drop of the 5R4.  The B+ goes down but because the bias rectifier, resistor string and control are independent of the rectifier, bias on the grid remains the same.  The result: lower cathode current, which requires readjustment of bias.

Bob L. suggests adding a 5K ohm resistor at R-39, which is a jumper on the M-125 driver boards, to give the pots more latitude in adjusting the bias voltage for the 5AR4s.

Extra range isn't an issue right now ... should be interesting to see what happens when I swap in a set of KT120's ...

Not sure if I'm getting more range than I would have using the trimmers used on the stock VTA board, but both those and the outboard pots I installed are rated at 50k ... remember these?



I do like the knobs though. Beats the carp out of digging into little holes with a jeweler's screwdriver. Also right nice having the test points right next to the controls. Very intuitive and fast ...

PS ... if I'd known more about the "mystery resistor" at R39 when I did the build, I might have been tempted to add a 10k pot there also.

sKiZo wrote:Extra range isn't an issue right now ... should be interesting to see what happens when I swap in a set of KT120's ...

Not sure if I'm getting more range than I would have using the trimmers used on the stock VTA board, but both those and the outboard pots I installed are rated at 50k ... remember these?



I do like the knobs though. Beats the carp out of digging into little holes with a jeweler's screwdriver. Also right nice having the test points right next to the controls. Very intuitive and fast ...

PS ... if I'd known more about the "mystery resistor" at R39 when I did the build, I might have been tempted to add a 10k pot there also.

Skiz, how're you liking those Psvanes now that you've burned 'em awhile.

 

Real nice tone - good and tight bottom to top. Then again, they're the only power tubes I've tried. Been rolling the drivers to see what happens and wanted to be able to give them all an equal playing field.

The Psvane's were originally intended as spares, but at this point, there's no real incentive to swap in the KT120's I was planning to use as a primary set. And to think these are their entry level HiFi version. Me like!

Current set is the copper cap WZ68, the Psvane KT88's, a Marconi 12AU7 in the center, and Sylvania 12BH7's on the sides, running in pentode mode.



Tried quite a few combos already, and these really sing. The Marconi opened up the sound stage considerably, and the Sylvania's add punch, yet keep things smooth ... bit of a Tina Turner "we always do it nice ... and rough"  kinda thang ...

** And ya ... I know ... this is a 5R4GYS thread.  

Haven't tried this tube set with the big bottle, and the amp's back down on the bench for one more go round with the meters. Few minor changes should get those working properly. Once I get it back in the system, I'll swap that rectifier back in and see what happens.

PS ... ooPS! Mail just came, and there's a set of gray plate RCA 12BH7's in there. One more rotation before I swap the rectifier ... somebody stops me!!

I have to say, that is one fine looking amp! Regardless of whether the meters work as intended it looks great!

Yeah ... if it's pretty enough, who cares if it works, right?  

But ... I believe a dancing banana is in order, as I finally got them things working ... here's the gory details ...

https://dynacotubeaudio.forumotion.com/t1656p120-custom-chassis#13646

PS ... thanx for the flowers. Pretty happy with how it turned out. Even if it doesn't look anything like what I originally intended. Still thinking about adding a cage for the transformers, but no rush there.

PS ... one more shout out for Front Panel Express. They do VERY nice work that adds a whole nuther level of goodness to the fit and finish.

WntrMute2 wrote:I have to say, that is one fine looking amp!   Regardless of whether the meters work as intended it looks great!

Agreed!

Started feeling guilty of all these pics of my shiny new amp ... MY PRECIOUS (gollum gollum)... running a standard rectifier in this thread, so here it is, with the big Phillips installed ... Also figured now that things have settled down and the amp's out of it's experimental phase, time to try those big KT120's that have been gathering dust.



One concern was how the Phillips and KT120's would bias up together. With a standard rectifier and the KT88's, the bias pots would be just a bit past 12 o'clock. Big difference with this tube set ... they're now at around 3 o'clock.



Not an issue, long as they got the range. I imagine the same would hold true of any ST120 using the stock trimmer pots also. I rolled one tube up to around 80mA just for a sec to make sure I had some wiggle room. Eventual plan is to run the KT120's up to 60mA after they burn in a bit.

And ya ... the meters work now. Nice for quick checks, and remarkably accurate just tweaking the knobs and double checking with the VOM to see how close I got. So, like ... neener neener ...  



THE VERDICT

Too early to tell really, as both the Phillips and KT120's are new out of the box, but the combo is definitely already tighter and smoother in the deep bass, and feels very airy in the midrange. The top seems to roll off a bit compared to the Psvane KT88's, but for me, that's a good thing as my room tends toward bright. All in all, I think I'm gonna stick with this for a bit and get some hours on the tubes, then report back.

PS ... also running different drivers, but I swapped those out BEFORE the power tube and rectifier changes. Current drivers are a matched pair of RCA grey plate 12AH7s and a NOS Gulbransen (Holland bugle boy) 12AU7 in the center.

Bad news ...

I just had the Phillips tube go weird on me in the last couple days. Bias started creeping DOWN during operation and I was having to reset it another 5mA UP each day when powering up. Still sounded good. That went on for a couple days and I gave up on it, as I'm already tickling the high side of the bias pots' range with this tube.

Put the WZ68 copper cap back in yesterday and rock steady once again. Immediately noticed better punch. Strange thing there is that I liked the Phillips because THAT was giving me better punch than the WZ68 ... go figure.

Top end was back to being a bit bright for my tastes, but I was able to compensate for that by switching out to a set of Sylvania 12GH7's and the Marconi 12AU7 center for drivers. I also switched to a WE 2C51(JW) in my tube DAC to bump the low bass and mids back up where I want them.

I suppose first thing I should do is get hold of Parts Connexion and see if I can get any kind of warranty on it. Come to find out, I bought it back in April, but figure it's only got about 10 hours running time. (mutter mutter mumble)

sKiZo wrote:Bad news ...

I just had the Phillips tube go weird on me in the last couple days. Bias started creeping DOWN during operation and I was having to reset it another 5mA UP each day when powering up. Still sounded good. That went on for a couple days and I gave up on it, as I'm already tickling the high side of the bias pots' range with this tube.

Put the WZ68 copper cap back in yesterday and rock steady once again. Immediately noticed better punch. Strange thing there is that I liked the Phillips because THAT was giving me better punch than the WZ68 ... go figure.

Top end was back to being a bit bright for my tastes, but I was able to compensate for that by switching out to a set of Sylvania 12GH7's and the Marconi 12AU7 center for drivers. I also switched to a WE 2C51(JW) in my tube DAC to bump the low bass and mids back up where I want them.

I suppose first thing I should do is get hold of Parts Connexion and see if I can get any kind of warranty on it. Come to find out, I bought it back in April, but figure it's only got about 10 hours running time. (mutter mutter mumble)

I've had fairly good luck with the Phillps tubes but am only running two output tubes on my M-125s, so less stress. Had one or two go gunny-bag with four outputs in the bank. At Bob Latino's suggestion I got some NOS Mullard GZ-33s. Brendan Biever has a nice stash of them at Tube World for $100 bux but are well worth it. They're "only" good for 2-3k hours, but that beats the Webers and Phillips by a fair run. They look better at night than the Philips and are rock solid throughout the audible frequency ranges.

Got an email back from Parts Connexion telling me basically ... too bad, so sad ... Ah, well.

I did find a guy with a couple Hammond 5AR4's ... $25 each ... Deal? He's also got a Sylvania for the same price. I imagine the Hammond pulls are British Mullards ...

That's a great price for the Hammonds, regardless of whether they're of British or Japanese origin. It's also a very good price for the Sylvania.

Yeah ... what I thought. I went ahead and bit for one Hammond and the Sylvania. That should keep me going for a while ...

PS ... long as I'm shuffling rectifiers, I finally got around to putting in your old Mullard. Rock steady and sounds sweet! Also doesn't have that "nuclear dawn" glow of the Chinese tube ... that's scary!

Those Shuguang 5AR4s do put off a huge glow. Probably why they're not able to handle as much load as a vintage Mullard! Still, it seems to have held up in your ST-120 under heavy load... so not too bad after all.

I've been hesitant to pop a tube rectifier into my ST-120 or my pair of M-125s. One of these days...

I ran GZ33s in those M-125s pretty much exclusively, Scott. I think the WZ68s I included with them had less than 20 hours on them. Of course, a GZ33 isn't cheap, but if you watch eBay and are patient you can snag them for around $50 per. I've three pair here I got relatively cheap that way.

JP

Guess I'll set up a saved search on eBay.