Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Return to Tube DIY Asylum

Message Sort: Post Order or Asylum Reverse Threaded

Bad 5AR4

108.168.121.47
Posted on August 27, 2015 at 13:03:34
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 I had bought some new Sovtek 5AR4 when I built the new 2A3 DC Gargoyles 8 or 9 months ago.

One of the 5AR4 tubes had a pretty big rattle when you move it around. I tried it out, it seemed OK until recently, it likes to arc over now.

Now this failure is probably my fault.
I run my tube amps on a mechanical timer as I use the amps for TV etc while I fall asleep.
The timer is not set for a specific time, I just spin the dial so it gives me about 1 1/2 hours before it shuts off.
Now sometimes during the day, it will shut the amps off just depending where the dial is, I would quickly run over and turn the timer back on.
I think it was these hot starts that put the questionable tube over the edge, apparently they don't like that.

Although the very first arc over happened when I tapped the amp checking for a microphonic/noisey tube, this is when it all started.

So I guess I will check the local music store to see if they have any 5AR4 and give them a quick shake before I buy them.
I will probably avoid Sovtek from now on as really this tube should not have made it past quality control with such an obvious rattle.
It was purchased from a eBay retailer, really I should have sent it back because of the rattle.

Now I could add some diodes that would probably mitigate such events, but I don't think it is necessary if I get some better tubes.

I will also set the timer to the proper time, to avoid it turning them off during the day. (Or will wait for the amps to cool before restarting them.)
The timer was set properly originally, but the time drifted because I kept spinning it ahead depending on what time I was going to sleep.

Normally I only use NOS or used vintage tubes to avoid the shoddy new ones, but the price of vintage 5AR4 are kinda crazy these days. I'm not interested in paying $500 for a pair of NOS rectifiers.
If I can't find a pair locally, perhaps I will gamble bidding on a used set.

△This message will self destruct in 10 seconds△

 

Hide full thread outline!
    ...
RE: Bad 5AR4, posted on August 27, 2015 at 13:14:02
Jim McShane
Dealer

Posts: 5910
Location: Chicago
Joined: January 13, 2003
 The new production Genalex and Tung-Sols are quite good (probably the Mullard as well, but I don't carry them so I have no experience with them). I would recommend either of the Genalex or Tung-Sol new production to you.

 

RE: Bad 5AR4, posted on August 27, 2015 at 13:33:13
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 OK I will look into these this evening, I don't have any 5AR4 available locally.

Thanks.


△This message will self destruct in 10 seconds△

 

I had very bad luck with Sovtek 5AR4's (nt), posted on August 27, 2015 at 14:16:50
gusser
Audiophile

Posts: 3649
Location: So. California
Joined: September 6, 2006
 z

 

RE: Bad 5AR4, posted on August 27, 2015 at 15:46:09
krankkall
Audiophile

Posts: 296
Location: New Mexico
Joined: April 5, 2014
 NOS Japanese 5AR4 tubes are about HALF the price of a NOS Mullard.
The build quality is quite good and they are reliable also.
I've been using a Hitachi 5AR4 tube for awhile now, with NO problems whatsoever.

Steve

 

RE: Bad 5AR4, posted on August 27, 2015 at 17:45:40
Paully
Audiophile

Posts: 5909
Location: West Virginia
Joined: February 15, 2004
 I thought JJ had a reputation for arcing at one point as well. That was a few years ago, no idea what their quality reputation is now. I watched one make a neat flash back then. Quite a show.

 

RE: I had very bad luck with Sovtek 5AR4's (nt), posted on August 27, 2015 at 18:53:02
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000



Have you tried the series SS diode tweak? It is known to stop "fireworks".


Eli D.

 

RE: Bad 5AR4, posted on August 27, 2015 at 19:48:32
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 Upon inspection of the Tung-Sol and Genalex, they "appear" to be the same tube as the Sovtek.
I haven't ruled them out, however at this point if it quacks like a duck...
Groove Tube's 5AR4 also appear to be the same Russian rectifier.
There is also a vintage General Electric branded Mullard that looks very, very similar to the Sovtek etc, although there are slight differences.

Perhaps there is a pecking order for who gets the better quality tube to re-brand, however I don't want to play Russian Roulette with rectifiers. (Horrible pun intended)

Now the JJ does a different construction, presumably made in the Slovak Republic. Preliminary research suggests it has a similar failure rate as the Sovtek.

I had not considered a Matsushita or Hitachi, I will keep my eyes peeled for those. The Japanese made good stuff.

That yellow schematic Eli suggested for Gusser was the one I ran across as well.
Fingers crossed I won't have to resort to that, though I don't think it would be the worst thing in the world.


△This message will self destruct in 10 seconds△

 

US made NOS are good, too, posted on August 28, 2015 at 04:46:20
FenderLover
 GE, Sylvania, & Philips ECG make good 5AR4s. If your PT can handle the extra current load & your unit can use a 5U4GB --- this maybe a good alternative. Many good NOS 5U4GB rectifiers are available.

 

RE: Bad 5AR4, posted on August 28, 2015 at 05:47:20
Jim McShane
Dealer

Posts: 5910
Location: Chicago
Joined: January 13, 2003
 I've posted this a million times - you CANNOT judge only by what you can see from outside the tube! MANY tubes with much different performance look alike but are not alike.

I've sent out a good number of the Tung-Sols and Genalexes - and they are sturdier and more durable than the Sovtek. The Tung-Sols and Genalex tubes hold up in difficult applications like Bob Latino's amps where the Sovtek is really at the extreme limit of its capability.

As I see it - in essence your post is saying I'm not representing the performance of the Genalex and Tung-Sol honestly. Or that I'm incompetent to judge the tubes, that my experience carries no weight. I can assure anyone reading this that I am passing along my honest opinion, period; and that opinion is based on actual experience with 100s of these new tubes.

Come on folks! These new rectifiers (like so many of the most recent Russian tubes) are top shelf products. If you absolutely have to have an old stock piece - fine. But IMHO it is no longer necessary to hunt down a rare and expensive old stock 5AR4 now that the new ones are here.

 

RE: US made NOS are good, too, posted on August 28, 2015 at 08:32:40
Cleantimestream
Audiophile

Posts: 7550
Location: Kentucky
Joined: June 30, 2005
 Yes Sir...the Tung Sol being my favorite over All rectifiers.... unless we include mercury vapor.
The Mind has No Firewall~ U.S. Army War College.

 

RE: US made NOS are good, too, posted on August 28, 2015 at 08:58:02
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 I agree there are a lot of good NOS tubes around.

The 5AR4/GZ-34 was chosen for this design because it has the least voltage drop of the common 5 volt rectifiers.

I might be able to rework the amps to accept 5V4 or GZ37, that's about it. Voltage is a hot commodity in the Gargoyle 2A3 DC amps.

△This message will self destruct in 10 seconds△

 

RE: Bad 5AR4, posted on August 28, 2015 at 09:48:29
Alpha Al
Industry Professional

Posts: 2958
Location: N. Carolina
Joined: February 16, 2004
Contributor
  Since: December 3, 2015
 Make sure your design has no more than 40uF for the first filter capacitor. 5AR4's don't like that. Actually, less is better for the tube.

 

RE: Bad 5AR4, posted on August 28, 2015 at 10:29:45
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 I used a 50uF based on the data sheet maximum 60uF.

I would consider reducing it even further if NOS rectifiers end up doing the same thing, but it probably won't be necessary.

It is kind of a low-compromise design. If I was to get backed into a corner, I would probably convert it to SS rectification.
That being said dropping to 40uF from 50uF is probably fairly insignificant.

Thanks.

△This message will self destruct in 10 seconds△

 

why do you HAVE to have a valve rectifier, anyway?, posted on August 29, 2015 at 02:20:48
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 Fast, soft recovery SS diodes are reliable, quiet and have no difficulty filling up large capacitors. Also, reliable and inexpensive.

Stiff power supplies are a good thing.




Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: why do you HAVE to have a valve rectifier, anyway?, posted on August 29, 2015 at 09:30:23
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 Tim,

All PN junction diodes exhibit a reverse recovery spike (switching noise). In modern UFnnnn types, the spike is small and easily snubbed.

The somewhat recently introduced high PIV silicon carbide Schottky diodes are noise free. The only item of advantage left for vacuum diodes is the slow start of types with cathode sleeves. Several good methods are available to "soften" the start of SS rectified PSUs.

Given forward drop considerations, old units built with vacuum rectifiers are frequently best left that way.

BTW, the great vintage amps known for superior bass performance (McIntosh 2nn, H/K Cit. 2, Marantz 8B) employ SS rectified PSUs. :>D


Eli D.

 

IME using SR SS rectifiers - snubbed - improved the bass a LOT!bit more power , posted on August 29, 2015 at 15:00:33
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 More power too, though we didn't exploit all the extra volts. The real benefit was a much wider full power bandwidth, which is more important to fidelity.

The bass is better than from the Class_A STAX DA80 I had for back-up, and it should be, with so much more energy storage.

There are a few Rs in the PSU to hold back the HT volts a bit. IF I wanted to, I could reduce the resistance in their PSUs, and put in a choke, and still perhaps get a bit more power.

But, when we started we weren't fully aware of the EL84M option.

Learnt a lot. .........

Get rid of all high mu / low GM small-signal tubes and you can use a lot less NFB in the gain stage. (LEAK power amps have a lot of gain, lost some.)

Add a CCS to the splitter-driver stage, and you can use less NFB around the following OPT stage.

Use NFB locally, and far less overall loop NFB. (Figure out what is enough loop NFB for your room/spkrs.)

Use best possible R's and Cs for each NFB section, local or loop.

Have a big *STIFF PSU - because you now can - and by-pass the last two caps.

*How much energy we can store in a PSU is given by the voltage squared and valve amp PSUs have 100s of volts.

IME valve amps can have far better bass IME&O than SS amps can. Warm expressive nuanced tube bass, but with SLAM.

IF I find I need more than 20watts Pentode (bass) and 16W UL (170 Hz up) for the being-built Manger based speakers? We can lose those Rs and use those extra volts! OR change the PT!!

I do agree that for some classics it is best to stay at the same power. Less stress on the original iron / output tubes, where the design runs them hard already.

I tried to stay with the GZ34 VR but they weren't cheap ..... and watching a Chinese one fail was not fun. Lesson one.

In short, I don't see any audible / lifetime / MTBFailure advantage to VRs, given that we can slow the inrush in other simple or more complex ways. Dropping them increases power-bandwidth and hugely improves the bass.

Who needs 'sag' in a hi-fi amplifier, eh?

We used the GZ34 octal sized hole for another PSU cap. ;-)








Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: why do you HAVE to have a valve rectifier, anyway?, posted on August 29, 2015 at 19:17:18
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 I agree, usually I do build my amps with a SS supply.

As Eli mentioned it does have it's merits for slow turn on, although might not be necessary for receiving class tubes.

By the nature of the design, I don't think I will hear an improvement in bass, but I suppose I could try by making something similar to a copper cap.
△This message will self destruct in 10 seconds△

 

A slow enough turn on can be achieved in lots of other ways, posted on August 29, 2015 at 21:17:44
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 But it is an important feature for most valves.

You can simply put a thermistor in the primary / AC mains side of the power transformer and leave it at that. And the heaters will come on first.

Or add another in the B+ / HT secondary on the other side. IIRC that is what we did for the LEAKs.

Or you can use a 555? timer circuit to delay the B+, set to the time your circuit takes to get all its filaments nice and hot.

Or ..... with Eli's suggestion using both VRs and SR diodes.

I simply saw the space where the GZ34/5AR4 socket was and wanted it for a filter cap. ;-) For the best sonic reasons.












Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: A slow enough turn on can be achieved in lots of other ways, posted on August 29, 2015 at 23:22:00
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 Tim I'm not sure if you are familiar with my amps, but do you think I would still see a bass improvement with these 1 watt class A amplifiers?

Even though they have valve rectifiers, the B+ is rock solid in this design.
(As well as the B+ on the 6J5)
It is a direct coupled design with the B+ for the driver coming off the cathode of the 2A3 similar in topology to the Free Lunch and BB Proof etc, but much better performing.

Fortunately they are mono blocs so I could in theory do an A-B comparison, it's just that with this design I would have to reconfigure all of the operating points to account for the increased B+.

It's doable, just tricky, I would have to be reasonably confident before I break out the soldering iron.

While I have not modeled the SS diodes in spice to look for an improvement, it is hard to imagine they would be better then what is there now, from a practical point of view.

Right now a 20Hz full blast sine fluctuates the B+ ~0.8 volts.
a 1000Hz full blast sine fluctuates the B+ ~0.01 volts.

If I may pat myself on the back, they are phenomenal.

Are there other areas I should look for improvements that I am not considering?



△This message will self destruct in 10 seconds△

 

Are they SE amps or PP?, posted on August 30, 2015 at 00:36:33
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 I am NOT an expert on valve circuits nor on PSU's but I do like to absorb general principles, that are supported by empirical evidence.

Viz? A good high-storage PSU sounds better than a good but VR-limited PSU. Ripple will be a whole lot lower, for a start.

And, that SS diodes offer you the possibility to substantially increase the energy storage in a valve amplifier, which VRs don't like. If we square 50 volts we get a factor of 2,500 if we square 300 V ( 6 times the volts) we get a factor of 90,000. Divided by 2,500 we get 36 times the storage.

In other words a quite small valve amp - in WPC terms - can have a far stiffer PSU than most BIG SS amps. And IMO&E far better bass. Less dry and tight perhaps but lots of slam. If it's a PP NFB amp then the advantage is considerable.

That is I am not claiming that good SS diodes - SRs / Schottkys - snubbed or not sound better than VRs, but pointing out that VR's do limit the stiffness we can achieve in a PSU.

Peak Inverse Voltage is the limitation VRs have.

I don't see how a VR can to do anything special to the sound a PSU gives us, but I know that a VR will limit the volts we can get and severely limit the amount of storage we can have. I also know that their use in guitar amps is because of the sag they are able to give. No Hi-fi amp needs sag.

So I ask, why do it?

Back to your amps?

It may, as you think possible, be overkill to increase the storage of your 1 watt amps. I don't know.

While it is quite possible to have too much storage which can pulse the PT too much, I haven't heard any negative consequences from these big PSUs in the LEAK St20s. The PT in these is probably a bit stressed in hot climates, so it could have been an issue.

I don't have an OEM LEAK St 20 circuit diagram to hand, but they had IIRC, three? or four 32uf? (small ones anyway) capacitors, circuit-value wise. Two in one can I think.

We used 4 x 470uf 400V dark-brown Nichicon caps in the bass-duty amp and 3 in the mid-treble amp. The last two in each amp are bypassed with MKP and MKS caps.


Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: US made NOS are good, too, posted on August 30, 2015 at 03:59:55
danlaudionut
Audiophile

Posts: 5480
Location: Schenectady
Joined: June 6, 2002

My favorite is the GE Copper Plate.

DanL



 

RE: Are they SE amps or PP?, posted on September 4, 2015 at 17:26:33
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 OK just to update this thread, I am going to use 5V4 rectifiers instead.

They have a little more drop then the 5AR4, but modeling suggests that I won't have to change the amp around.

I suppose because I am not drawing near the rated current through either tube, the voltage drop in practical use is pretty low and comparable between the two.

At full rating the 5AR4 drops 17 volts while the 5V4 drops 25, for all intents and purposes they are within a percent or two of each other in my application.


Thanks for all the suggestions, I'm not sure why I over looked the 5V4 the first time around, I guess I just missed it reading incomplete lists.

So I have a nice pair coming from the 'bay.
The price is SO MUCH better for the 5V4 as well.
I think I paid around $24 USD for the tested and matched pair, that is more like it!
(Coke-bottle glass, black-plate RCAs, what's not to like!)

The 5AR4 is off my list completely in the future, I won't back myself into that corner again by choosing them. I will let the other turkeys fight over them and the crappy new production. Screw that noise.


△This message will self destruct in 10 seconds△

 

Page processed in 0.034 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]