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Shuguang 807s?

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Hey all,

Just wondering if anyone's had any experience with the Shuguang 807 in audio applications out there? If so I would like to hear about it. Wondering how they sound and if they're reliable. I've had some less-than-wonderful experience with Chinese 6146s in radio stuff recently. Would rather not repeat that experience.

Thanks in advance.
 
I can't speak for the Shuguang 807's. The US 807 is derived from the 6L6GB. If Shuguang adopted the western philosophy of stuffing the same guts into a few different bottles, then you could be in luck.

I have been experimenting with the Shuguang "Coke Bottle 6L6GC" and the tubular 6L6GCR, which appear to be the same guts inside different shaped glass. These tubes sound good in audio application, and stand up to serious abuse without any problem. I have been operating a pair, that previously served duty in a Bandmaster, in an SE amplifier at 35 watts plate dissipation (dull glow in dark room) to test their reliability. These tubes have been going strong for over a year at this power level without issue. I have cranked this pair to 44 watts dissipation for an hour (serious plate glow) without failure. I have recently tested 6 more pair at the 35 watt level for about an hour each without issue.

If their 807 is made with the same guts they should be indestructible at 807 power levels (19 watts). I looked at the picture, and it looks the same as their 6L6GCR.
 
I agree......More 807's were produced than any other tube and are very reliable. I've used newer SHugang types and found the internal cage not so mechanically stable as other makes. So I don't use Shugangs in amps parked on a bass bin. In the past, it was the done thing to put tube amps on top of bass bins, but I went through a bad experience with a 200W bass amp using KT90's which ended up with internal shorts and a blown psu.
Generally I mod amps to take 5881's instead of 807's. I can't count the number of times I've had the inside arm "stung" by the wretched top cap.

richj
 
I never thought about the possibility of mechanical weakness. That's a good point. The PA section will be used either for bass guitar or pedal steel, depending on the need at the time. I've wanted to use an older 'top cap' type of tube for a while now just to be a bit different. They're also far cheaper. I have several NOS 807s and 1625s in the junk box but wondered about supply should this crazy idea of mine take off and by some strange stroke of luck actually be something marketable. (NOT) Since "lots-of-watts" is a requirement for this project, I do want the ability to be able to run them all the way up to the maximum rated anode voltage though if that's where the 'sweet spot' is, and based on a not-so-fun-filled experience trying to do this with EL-34s some time back (arcing through the tube socket at 725 volts) I figured there'd be a pretty good chance that wouldn't happen with 807s. I also heard a push-pull 807 monoblock some time back and it had an enchanting character about it. I've heard those tubes are real sleepers. Speaking of EL-34s.... I just re-tubed my Marshall guitar amp clone with some new JJs. Nice! Very nice! ( mentioned this because someone mentioned JJ tubes earlier in this thread ) So really, to answer the questions as to "why Chinese", mostly because of cost and supply considerations. I'll poke around as a couple have suggested and see what I can find on ePay. I know I can get NOS 1625s for around $5 a piece but there aren't many left.

Anyway.... thanks all!
 
AD5GB said:
Since "lots-of-watts" is a requirement for this project, I do want the ability to be able to run them all the way up to the maximum rated anode voltage though if that's where the 'sweet spot' is, and based on a not-so-fun-filled experience trying to do this with EL-34s some time back (arcing through the tube socket at 725 volts) I figured there'd be a pretty good chance that wouldn't happen with 807s.

You can get "lots o' watts" from 807s. Although the sweetest spot occurs at Vpp= 365Vdc, Vsgs= 270Vdc; Po= 26.5W. This Q-Point gives a THD of 1.8% before any NFB is applied. That beats almost every "audio" final out there. Since I wanted fidelity, that's where I run the 807s for my project. Since you said you wanted a gee-tar amp, that's not so important. If you put them into Class AB2, you can get more power. Class AB2 807s can do 80W at a respectable 3.5% THD, which is not uncommon for many an audio final anyway. According to the data from RCA, 807s run at the max Vpp can put out 120W. This is for AM modulator purposes, and there are no figures for THD, probably because this particular app doesn't bother with THD since high fidelity is neither needed nor desireable. For a guitar amp, it might work out just fine.

In any case, Class AB2 807s are an easy load, figures cited are 100 -- 200mW of audio drive. That's easily provided by cathode follower drivers.


I also heard a push-pull 807 monoblock some time back and it had an enchanting character about it. I've heard those tubes are real sleepers. I know I can get NOS 1625s for around $5 a piece but there aren't many left.

Anyway.... thanks all!

Don't they though? I'd go get 'em. The only problem might possibly be the sockets. Unlike 807s, 1625s have a seven pin socket instead of the five pin the 807 uses. Go Here and download the STC Application report for the 807.
 
Hi Miles,

Thanks for the link! Quite interesting! Curious about the operating parameters you specified. How did you determine these? At what load Z? How much (if any) NFB? (I'm assuming A1 push-pull at the power level you mentioned???) I've never fooled with them at all yet but am leaning strongly in that direction for this project. Now if I can come up with a good design for a driver stage for 6 of them in parallel push-pull I'll be set! 3.5% THD doesn't sound too bad. For steel guitar and bass I really don't want too much distortion.... especially for steel. Now when I'm playin' rock-n-roll guitar through my homebrewed Marshall clone, I want "square waves" (LOL) but this project is something different entirely. I need to be in the 200-250 watt range, or better, but with lots of dynamic reserve for transients. (especially for bass) Anyway, thanks again!

Kind regards
 
AD5GB said:
Hi Miles,

Thanks for the link! Quite interesting! Curious about the operating parameters you specified. How did you determine these? At what load Z?

I didn't determine anything. I got the Q-Point I used from the STC App report I linked to in the previous post. It's on page 6.

How much (if any) NFB? (I'm assuming A1 push-pull at the power level you mentioned???)

For the 1.8% that the STC quotes, there isn't any NFB applied. In the final design, I used 6.95db(v) of local feedback, and 4.0db(v) of global. As for the local feedback, that figure comes from Beam Power Tubes.


I've never fooled with them at all yet but am leaning strongly in that direction for this project. Now if I can come up with a good design for a driver stage for 6 of them in parallel push-pull I'll be set!

Getting six VTs all pulling together is quite a formidable task indeed. Take a look-see at This and see how he gets the bias servos to track. You'll definitely need lots of silicon, and 6SN7 drivers as well.


3.5% THD doesn't sound too bad. For steel guitar and bass I really don't want too much distortion.... especially for steel. Now when I'm playin' rock-n-roll guitar through my homebrewed Marshall clone, I want "square waves" (LOL) but this project is something different entirely. I need to be in the 200-250 watt range, or better, but with lots of dynamic reserve for transients. (especially for bass) Anyway, thanks again!

Kind regards

That's 3.5% before feedback, remember. If you include feedback, you will be able to get that much lower. Although my preference for a 200+W amp would be beefier RF pentodes. Although I guess that wouldn't do if considering moving the amp from gig to gig.
 
Well.... dang! I read that, but never made the connection that those specs you quoted were the same as in the app notes. Information overload maybe??? Anyway, I originally set out to do this with a pair of 813s as I have several that I no longer use in radio stuff. The things are nearly bulletproof. The only way I know to take one out of service is with a hammer! I talked to a couple of transformer winders about getting the output iron custom made and I was talked out of it. Seems both thought that to get enough L for low frequency response and enough Z for the p-p load, the sheer amount of wire needed would likely cause shunt capacitance problems and do strange things to the high end. I'm not a transformer wizard by any means, though I am getting smarter about it as I pursue this project. A pair of 813s would certainly be much simpler!

Anyway, thanks again.
 
AD5GB said:
Well.... dang! I read that, but never made the connection that those specs you quoted were the same as in the app notes. Information overload maybe??? Anyway, I originally set out to do this with a pair of 813s as I have several that I no longer use in radio stuff. The things are nearly bulletproof. The only way I know to take one out of service is with a hammer! I talked to a couple of transformer winders about getting the output iron custom made and I was talked out of it. Seems both thought that to get enough L for low frequency response and enough Z for the p-p load, the sheer amount of wire needed would likely cause shunt capacitance problems and do strange things to the high end. I'm not a transformer wizard by any means, though I am getting smarter about it as I pursue this project. A pair of 813s would certainly be much simpler!

Anyway, thanks again.

PP 813's has been done lots of times. I'd definitely consider it.
 
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