I am looking for a pair of new production (meaning not expensive NOS) 6l6GC's that can HONESTLY withstand 500+ volts on the plates. The amp is a late 70's Fender Pro-Reverb with a b+ of around 500-512 volts, depending on biasing. I have tried Groove tubes, Mesa Boogies, Sovteks and Svetlanas and they all went to hell (red plates, meltdown, etc).
It appears the reissue Tung Sol's can withstand 550 volts. Anyone have experience with these?
It appears the reissue Tung Sol's can withstand 550 volts. Anyone have experience with these?
hey-Hey!!!,
With the -GC version I have found dissipation far more important than voltage. I've run 6L6GC in my Dynaco Mk.III at ~520V and a full 30W of dissipation. At this level, grid circuit value, and dissipation limits are quite more than the usual tube-flavoured 'suggestion', much more like the ratings applied to silicon devices...
Make sure your amp isn't running them over the limits first.
cheers,
Douglas
With the -GC version I have found dissipation far more important than voltage. I've run 6L6GC in my Dynaco Mk.III at ~520V and a full 30W of dissipation. At this level, grid circuit value, and dissipation limits are quite more than the usual tube-flavoured 'suggestion', much more like the ratings applied to silicon devices...
Make sure your amp isn't running them over the limits first.
cheers,
Douglas
I have used GC's (new production) and even with the bias at minimum (around -50 volts) they fail. They don't make em like they used to, I guess. I also read that JJ has a version rated at 550 plate. Anyone tried those?
Interestingly, the vintage Sylvanias that came with the amp when I bought it worked just fine. The only issue was that one broke and the other became microphonic , but those 6BG6's look good.
Interestingly, the vintage Sylvanias that came with the amp when I bought it worked just fine. The only issue was that one broke and the other became microphonic
, but those 6BG6's look good.I restore and mod Fender Amps fairly often.
On the latest (Bassman 100) I used JJ 6L6GC and regretted it. They were'nt really well matched and 2 stopped working as a result of very minor physical taps. I had the amp upside down on the work bench. I pulled the tubes - as they released they moved maybe 1 inch (2.5 cm) and the glass domes rapped onto the rubberized antistatic mat on my work bench. Evebn so that was enough to kill them. Simply no current at all from 2 of the 4 output tubes when put back in. That meant I had to buy another quad.
The amp I did before that was a Twin Reverb, the 135W Ultralinear job, and I used Winged C Svetlana. This was an amp for a professional muso - and he loved them. They balanced perfectly and did'nt even blink at the B+ of +500V on anodes AND screens.
The one before that was a Vintage Bandmaster and I used Winged C Svets in it as well.
The Winged C Svetlana are little more expensive BUT worth it for their superior sound and reliability - PLUS their bases fit into those dingy Fender tube clamps - and they are cheaper than having to buy 2 quads from JJ to end up with one working quad.
Next time its Winged C Svetlana for me.
Cheers,
Ian
On the latest (Bassman 100) I used JJ 6L6GC and regretted it. They were'nt really well matched and 2 stopped working as a result of very minor physical taps. I had the amp upside down on the work bench. I pulled the tubes - as they released they moved maybe 1 inch (2.5 cm) and the glass domes rapped onto the rubberized antistatic mat on my work bench. Evebn so that was enough to kill them. Simply no current at all from 2 of the 4 output tubes when put back in. That meant I had to buy another quad.
The amp I did before that was a Twin Reverb, the 135W Ultralinear job, and I used Winged C Svetlana. This was an amp for a professional muso - and he loved them. They balanced perfectly and did'nt even blink at the B+ of +500V on anodes AND screens.
The one before that was a Vintage Bandmaster and I used Winged C Svets in it as well.
The Winged C Svetlana are little more expensive BUT worth it for their superior sound and reliability - PLUS their bases fit into those dingy Fender tube clamps - and they are cheaper than having to buy 2 quads from JJ to end up with one working quad.
Next time its Winged C Svetlana for me.
Cheers,
Ian
I've put 500V on SED 6L6GCs and they took it no problem. Great sound tube too.
http://thetubestore.com/6l6gc.html
http://thetubestore.com/6l6gc.html
I don't like putting 500V on modern 6L6GCs, and even less on EL34s.
I explain this weakness to my customers, and many like to have a mod installed to drop the screen voltage - since the screen is the problem (even the modern ones can take it on the anode/plate).
Use a 900V TO-220 ISO packaged PowerMOS device bolted to the chassis and a potential divider (use high voltage resistors: 220..560K to gate, about 2M to ground). 47nF or so at the gate is enough in many guitar amps to do without a choke, if the incoming supply is not too rough. Feed the FET drain through a 5W+ 100ohm resistor and 1uF or more of adequately rated capacitor (MKP best here). At the source, 22uF to 68uF depending on the amp's power. A 10V gate protection zener (don't ever omit this) and 390ohms or so of gate resistor (noninductive, pref. chip resistor, right up at the gate pin) rounds off the design.
The pic shows such a gyrator nestling into a JCM800. The "PCB" is just blank copper FR4 with hacksawed tiles.
Set the voltage at 450V or less for good 6L6GCs, 400V or less for other 6L6/5881, and 390V for EL34s.
Even with 390V Vg2 on EL34PP (fixed bias) and 450V anode (plate) volts, you still get over 50W if the trafo is OK.
Dropping the screen volts hugely improves the durability of old high volt guitar amps, and if you use the protection components listed, the reliability of the dropper/gyrator is perfect. And, players are very happy with the sound, most importantly!
I explain this weakness to my customers, and many like to have a mod installed to drop the screen voltage - since the screen is the problem (even the modern ones can take it on the anode/plate).
Use a 900V TO-220 ISO packaged PowerMOS device bolted to the chassis and a potential divider (use high voltage resistors: 220..560K to gate, about 2M to ground). 47nF or so at the gate is enough in many guitar amps to do without a choke, if the incoming supply is not too rough. Feed the FET drain through a 5W+ 100ohm resistor and 1uF or more of adequately rated capacitor (MKP best here). At the source, 22uF to 68uF depending on the amp's power. A 10V gate protection zener (don't ever omit this) and 390ohms or so of gate resistor (noninductive, pref. chip resistor, right up at the gate pin) rounds off the design.
The pic shows such a gyrator nestling into a JCM800. The "PCB" is just blank copper FR4 with hacksawed tiles.
Set the voltage at 450V or less for good 6L6GCs, 400V or less for other 6L6/5881, and 390V for EL34s.
Even with 390V Vg2 on EL34PP (fixed bias) and 450V anode (plate) volts, you still get over 50W if the trafo is OK.
Dropping the screen volts hugely improves the durability of old high volt guitar amps, and if you use the protection components listed, the reliability of the dropper/gyrator is perfect. And, players are very happy with the sound, most importantly!
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Thanks for the suggestions. I think Im gonna give the Sovtek 6L6WXT+ a try since they are so cheap. The SED's look nice but are too expensive at $60/pair!!
Rod,
Your comment about the screen grid makes sense as these are usually connected to the almost the same potential as the plates on most guitar amps. Btw, doesn't the EL34 handle 800 volts(plate only)? I think it also uses an extra pin that's unused in the 6L6's. But EL34's on a Fender, heressy
Rod,
Your comment about the screen grid makes sense as these are usually connected to the almost the same potential as the plates on most guitar amps. Btw, doesn't the EL34 handle 800 volts(plate only)? I think it also uses an extra pin that's unused in the 6L6's. But EL34's on a Fender, heressy
Try the generic Sovtek 5881's they will handle that amp easily they sound ok. I really liked the old Sevetlana 6L6's in Fenders like that one but I've also had good luck with the JJ 6L6 maybe you had some bad ones? The newer Sevetlanas sold by New Sensor are just not as good as the old ones were I've had those blow up and fail quickly in a Fender, I have not tried the SED tubes.
If you want to use an EL34, yes. Pins 1 and 8. Just make sure pin 1 isn't being used for anything else.
http://tdsl.duncanamps.com/show.php?des=6L6GC
http://tdsl.duncanamps.com/show.php?des=EL34
http://tdsl.duncanamps.com/show.php?des=6L6GC
http://tdsl.duncanamps.com/show.php?des=EL34
Yeah, I agree, you could never put EL34s in a Fender, any more than 6L6s in a Marshall!
The high 800V spec on the EL34s just shows that anode volt limits are NOT the problem. In fact the modern EL34 is usually reckoned to be weaker than 6L6GC in guitar amps - check out the notes in the Mesa-Boogie manual for instance.
The Mullard EL34 spec was Anode 800V max, Screen 500V max. Compare the new JJ EL34: 800V/450V - and if you play your JJs hard, you will quickly see why they reduced that spec.
For 6L6GCs the ratings are 500V anode, 450V screen for most -GC versions.
Overrunning the screen voltage is always going to run you into short life and sudden failure territory, especially if you like to turn it up. Keep in mind that screen overheating, below the level of outright failure, can release contaminants into the vacuum, ultimately killing tone. I reckon the screen dropper pays for itself fairly soon against frequent valve replacement.
Nothing wrong with using a 6L6 in a Marshall and many of their amps came with them or similar type KT66's. For what it's worth I've tried a 6V6 in a Marshall 50 watt just to try to reduce power and to experiment. Believe it or not it still sounded very "Marshall".. EL34's in a Fender can be done but be careful about drawing too much heater current.
Your options are many on the 6L6 amp. Try a set of the Valve Art KT66's and see how you like them in the Fender. I use them in Marshalls and they are quite nice. The Saratov version that Groove Tubes used to sell as the KT66HP was great but I don't have any more of those.
Your options are many on the 6L6 amp. Try a set of the Valve Art KT66's and see how you like them in the Fender. I use them in Marshalls and they are quite nice. The Saratov version that Groove Tubes used to sell as the KT66HP was great but I don't have any more of those.
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