Anyone use SHUGUANG tubes?

[Audiotexan]

About the only sure thing I've found to avoid, is using Sovtek 5881 wafer-base tubes with "bear trap" style retainers. The bear trap steel doesn't grab the glass, and raps against it in shipping or rattling around in the back of the equipment truck.

Great point! In those cases, I'd always bend the traps almost flat, and then make sure that the sockets have plenty of tension. Still not ideal...but better than cracked glass all the same.

Incidentally, I've always hated the 'bear trap' style. Just because of the pressure. Some would dig in so hard (depending on the base material used on the tube), that you have to literally *bend them* out of the way, or bend them back into 'holding position' after a swap because of lack of uniformity in base dimensions across brands.

I've always preferred the dual springs/cap method myself (retention wise), but those have their own minor hang-ups as well.

Perhaps one of these days, someone will create replacement noval and octal 'retention bases' that have a base made out of hard plastic, with a main body that partially encapsulates the lower third/half of the tube made out of high-temp silicon to perform tube-retention duties.
One plus would be the silicon style (as described) should be able to 'give' enough to accomodate the differences in dimensions between brands. As a perk, it could/should also conceivably help with microphonics!

[Audiotexan]

Ha ha, I don't have the rich knowledge on tubes, so I take two pictures of the 6L6 and EL34. Let me know whether that answer your question or you want picture from another angle. I got it on ebay.....the cheapest of the cheap!!!!

(Without offense) That's what those are
The 'baseline' run-of-the-mill shug's. The 6L6 pic is a format they've used since at least 1986..as I have an old set of Mesa STR-420s that used the same design still NOS in the package, that I've yet to need (which I bought in 86-87). They're decent enough tubes though -especially for the price, as long as they're not microphonic, and you can match them up (as you noted in a previous post in this thread).

The EL34 is a bit newer revision. Not sure when they started this style, but it's definitely 'newer'. The first thing I noticed was it has the dimpled square getters on bent posts. (Just above the darker 'wings' resting above the top mica spacer.)
The older version had circular getters on straight posts IIRC.

EDIT:
Here's a couple of variants to give you an idea..

"Coke Bottle":
pic property of srs-webstore.com
*note - getter(s) hidden by the flashing in the base*

6L6GC large bottle w-getters at bottom:
pic property of mableaudio.com

6L6GC w-halo getter at top:
*note the different plates*

larger glass bottled EL34:
pic property of srs-webstore.com
*note the halo getter*

and there's a few others...not to mention the variants in between the 'same model' over the years. But that'll at least hopefully give you a better idea!

[Leo_Gnardo]

What audiotexan said ^^^ with lots of illustrations. That EL34 is an old bugaboo for me. I started noticing them late 80'a same time just about all other EL34 production lines were shutting down or long gone. There's a "splint" spot welded to the plate - what for - to keep it from bending when it gets hot? I was hoping someday Shuguang would order a thicker plate material, maybe make their EL34 more reliable. Early 90's I had a conversation with the man who runs Ruby/Magic. He had already started to leave a trail across the Pacific with many trips to Shuguang, trying to get them to improve their product. He told me his meeting with Shuggie's vacuum tube manager ended like this: "We make 300,000 EL34 every year and every one gets sold. I don't see any reason to improve the product." Put bang-head-against-wall smiley thing here. Not long after this, Marshall started loading their new amps with Sovtek 5881 wafer-bases. Do you think Mr. Shuguang Manager noticed his orders deeply diminished? Oh yes, I think so - by late 90's they were making a definitely improved EL34 that Ruby marketed as EL34BSTR. Couple more years, some heat-sink wings added to the plate, & maybe other interior improvements, Ruby's EL34BHT. TAD also started putting in orders for their special tubes from Shuguang and all for the better. By early 2000's =C= the real Svetlana EL34's were also established on the market, and they certainly won some fans. Even Sovtek/EH had some pretty good ones too.

Splint on the plate, (shakes head), what were they thinking? I got a pile of 'em, anybody want? Good for target practice. They go pop when you hit 'em.

[Alan0354]

I can tell you I use one pair of 6L6 in my Pro Reverb, so far so good. I really should power up the EL34 as I have it for over a month and still have not power it up yet.

Ha ha, I really don't know the history of these tubes, at this point, as long it's not microphonic, it's fine with me. Maybe when my ears learn to be more sensitive, I might be pickier. Besides, let's be real, all my amps is not likely going leave the house!!!! So ruggedness are not exactly at the top priority at the moment. This and studying is more like cross word puzzle for the retirees, something to keep the old brain going.

[Alan0354]

One of the 10 12AX7 is microphonic. It cannot be used as the first stage of the high gain channel.

[Alan0354]

Now this one is bad, I finally power up all the EL34, one has something loose inside and it make a loud cracking noise when tapped. I am going to write to the seller, but it's been 2 months, I doubt the seller going to do anything. lesson learn, test the tubes when you receive them!!!

[Alan0354]

Update:

A 12AX7 just bite the dust. I was playing and all of a sudden noise came on, hissing and some popping and I loss the sound. I trouble shoot down, the cathode of the cathode follower read 330V and the grid read 239V. I change the tube and everything back to normal. So I have one 12AX7 and one EL34 that are bad so far. And one microphonic.

Now, this one is not out of the box bad, it's been running for like 2 months.

[Chuck H]

To be clear, this was a Shuguang 12ax7 that failed, correct? How many volts on your cathode when the cathode follower is working correctly? AND what is your filament arrangement like?

[Alan0354]

To be clear, this was a Shuguang 12ax7 that failed, correct? How many volts on your cathode when the cathode follower is working correctly? AND what is your filament arrangement like?

Yes, it's the Shunguang that failed. It's not brand new, it's been in the amp when I first received the tubes at the starting of this thread. But it's no where old, I say it's about 30 hours max. It failed right in the middle of me playing the guitar. When the CF working correctly, the cathode voltage is about a volt or so higher than the grid, I measured that before. The filament is in parallel using about 5.8V DC. I rectifier the 5V winding for the floating filament that is for the rectifier tube.

[frus]

When the CF working correctly, the cathode voltage is about a volt or so higher than the grid

yes, but how much higher than the heaters?

[Alan0354]

yes, but how much higher than the heaters?

240V. Yes, I run the voltage very high. I just read two 12AX7, the limiting value is 180V. I went in and change the dropping resistor and now one CF reads 190V and the other 205V. You think this is safe?

[Chuck H]

240V. Yes, I run the voltage very high. I just read two 12AX7, the limiting value is 180V. You think that's the problem?

In a perfect world, no. The 5F6A (for example) doesn't exceed that max rating, but some of the old Fender tremolo circuits do and those amps work fine! Right!?! Well... Back in the golden age I suppose they tried it and got away with it. I simply don't expect new tubes to be capable of exceeding the ratings. In fact, for a recent custom build I had to do a bias vary trem. Knowing the sensitivity of new preamp tubes to the filament cathode differential (especially the Rusky tubes) I decided to use the reissue Fender circuit. It presents a lower differential. I also used a power transformer with two 6.3V windings and elevated the preamp (and trem) about 50V to further reduce the differential. When I was consulting here about the build I was advised repeatedly to just build a stock 6G16 type circuit since they work fine, But the way I see it, I expect this amp to be around for awhile and this situation with preamp tubes isn't going to get better. Also, I may die (or something) before the amp does. Then some goofy guru tech might service the amp and plug a Rusky tube into the trem circuit. No good. I had to build it fail safe. So...

I'd suggest lowering that voltage to the stock 5F6A spec of 180V and also DC elevate the filaments a bit for added insurance. That's just my way. You can't make music with a broken amp. So build it to work. That means accounting for more tender preamp tubes.

This is actually the first time I'm hearing of the Shuguang product failing due to the cathode/filament differential. It may just be a random event. I'd redesign the circuit with caution anyway.

[Alan0354]

Yes, I edited post #116 that I lower the voltage to 190 and 205. At least I dropped 50 on one and 35 on the other.

[Chuck H]

That's probably fine with the Shuguang tubes if you float the filaments 25 volts or more. I wouldn't use any Russian tubes for the CF and I wouldn't assume the Shuguangs for better than the typical 180V spec differential. Maybe they are.?. Why take the chance when it's easy to elevate the heaters.

[Alan0354]

That's probably fine with the Shuguang tubes if you float the filaments 25 volts or more. I wouldn't use any Russian tubes for the CF and I wouldn't assume the Shuguangs for better than the typical 180V spec differential. Maybe they are.?. Why take the chance when it's easy to elevate the heaters.

I might just do that!!! Last time you advice me to run higher plate voltage, I like it better, I hate to lower it down. My preamp tubes are running on the 5V separate secondary originally for the floating filament of the rectifier tube, so I just float all the filaments of the preamp tubes up to say 60V and I go back to 240V plate again.

Thanks, you always have good ideas and come to rescue.