Background: I am looking to buy output tubes for an upcoming SET project. OPT's are 7.6K impedance, and B+ possibly 475V (if you this is a bad operating point feel free to interject). I am thinking Russian KT66 would be a good choice.
So I am a bit warier of the cheap Russian tubes now that I ordered some Sovtek 6SN7 and they came with the old labelling of 6H8C right on them as well as the new 6SN7 labelling. Wish I'd known that beforehand.
And so I was looking through the 6L6 family to see what was cheap on eBay, and 6P3S-E, the bigger version of the 6P3S, and I've read is often relabelled 5881, looked good. However the only datasheet for the -E version I could find listed the max anode voltage as 250V, hardly a good situation if you sub it into a 5881 amp with a higher B+.
So my question is twofold: in shopping for a Russian 6L6 family tube are there some particularly bad eggs to avoid, and are the Russian KT66's some other tube just relabelled that I could buy cheaper as a Russian equivalent?
So I am a bit warier of the cheap Russian tubes now that I ordered some Sovtek 6SN7 and they came with the old labelling of 6H8C right on them as well as the new 6SN7 labelling. Wish I'd known that beforehand.
And so I was looking through the 6L6 family to see what was cheap on eBay, and 6P3S-E, the bigger version of the 6P3S, and I've read is often relabelled 5881, looked good. However the only datasheet for the -E version I could find listed the max anode voltage as 250V, hardly a good situation if you sub it into a 5881 amp with a higher B+.
So my question is twofold: in shopping for a Russian 6L6 family tube are there some particularly bad eggs to avoid, and are the Russian KT66's some other tube just relabelled that I could buy cheaper as a Russian equivalent?
Leadbelly,
Yes, I found the Russians can be pretty free with their designations. I have listed the 6L6 variations elsewhere, I think on the "Quad" thread but cannot find it now. Summarising, there was a 6L6GB at 19W, the 5881 at 23W and the (preferred) 6L6GC at 30W plate dissipation. The Russians sometimes call everything 6L6GC. They also market a KT66 with actual 6L6 innards, but that is not such a problem as they are very close. (But do beware of Chinese "equivalents"! A no-go.)
SY,
That is good news for me - as a moderator you would have noticed my quieries from time to time about NOS 6L6GCs, which have become quite expensive. Not to doubt your word, but the only 6BG6(GA) that I find in my RCA Manual is a discontinued type with the anode going to a top cap and different base connections to 7027. Are you saying that this super 6BG6 is exactly like a 7027, or with the 6BG6 base connections and cap? You did say "rebased". Does the innards look like a 6L6? I am in the market for 10 or so, which in our economy is quite a bit of money; I cannot afford a mistake.
Regards and thanks.
Yes, I found the Russians can be pretty free with their designations. I have listed the 6L6 variations elsewhere, I think on the "Quad" thread but cannot find it now. Summarising, there was a 6L6GB at 19W, the 5881 at 23W and the (preferred) 6L6GC at 30W plate dissipation. The Russians sometimes call everything 6L6GC. They also market a KT66 with actual 6L6 innards, but that is not such a problem as they are very close. (But do beware of Chinese "equivalents"! A no-go.)
SY,
That is good news for me - as a moderator you would have noticed my quieries from time to time about NOS 6L6GCs, which have become quite expensive. Not to doubt your word, but the only 6BG6(GA) that I find in my RCA Manual is a discontinued type with the anode going to a top cap and different base connections to 7027. Are you saying that this super 6BG6 is exactly like a 7027, or with the 6BG6 base connections and cap? You did say "rebased". Does the innards look like a 6L6? I am in the market for 10 or so, which in our economy is quite a bit of money; I cannot afford a mistake.
Regards and thanks.
Both visually and in how they run in my amp, these appear to be rebased 7027A, i.e., 7027 guts with a top cap and 6BG6 pinout. The original 6BG6 spec is 20W plate dissipation- I run the "super" 6BG6 near 30 without any signs of redness. Power output is identical to EL37s that previously graced this amp (a rebuilt Eico HF87).
If I were better at photography and had a decent camera, I'd show you the tube side by side with an authentic 7027A. But since I'm not and I don't, I can only say that after buying the first 4 and trying them out, I immediately ordered 24 more.
http://www.vacuumtubes.com/6BG6.html
Disclaimer: no financial involvement there except as a very satisfied customer
If I were better at photography and had a decent camera, I'd show you the tube side by side with an authentic 7027A. But since I'm not and I don't, I can only say that after buying the first 4 and trying them out, I immediately ordered 24 more.
http://www.vacuumtubes.com/6BG6.html
Disclaimer: no financial involvement there except as a very satisfied customer
At this price, I bought a pile of unmatched and made matched quads out of them (matched at idle current only- I didn't further do a transconductance match). The variation was unexceptional, i.e., not trivial but not extraordinary.
But SND doesn't charge a lot for the matching, so if you don't anticipate blowing through a lot of them, pay the couple bucks extra. They're still dirt cheap.
But SND doesn't charge a lot for the matching, so if you don't anticipate blowing through a lot of them, pay the couple bucks extra. They're still dirt cheap.
There are real new production KT66.
http://www.thetubestore.com/6l65881types.html
Scroll down and the last one is exactly what you do not want (A 6L6 relabelled as a KT66). There was also someone selling Chinese coke bottle 6L6 as KT66 a couple months ago.
The Saratov KT66 and Shuguang KT66 are real KT66. I got a quad of the Saratov version on ebay 1 year ago for about 40$. I can't compare them to the real GEC KT66 (too expensive), but I like mine.
I think I read that the Groove Tube version is the Saratov one.
They are available at many places, but just be sure to get a real KT66 (the internal construction is unmistakable).
http://www.thetubestore.com/6l65881types.html
Scroll down and the last one is exactly what you do not want (A 6L6 relabelled as a KT66). There was also someone selling Chinese coke bottle 6L6 as KT66 a couple months ago.
The Saratov KT66 and Shuguang KT66 are real KT66. I got a quad of the Saratov version on ebay 1 year ago for about 40$. I can't compare them to the real GEC KT66 (too expensive), but I like mine.
I think I read that the Groove Tube version is the Saratov one.
They are available at many places, but just be sure to get a real KT66 (the internal construction is unmistakable).
OK, SY, they're here!
The 6BG6's have arrived. They look so cool I am excited!
Well SY, you seem to be the expert on these, what kind of drive do they like (both SE and PP, I bought enough for both)? Will a simple grounded stage do or is something beefier required? I've got tubes like 6922, 6N1P, 6H8C, 6EJ7, 6N6P saved up, as well as some of the Group Buy Aikido boards.
The 6BG6's have arrived. They look so cool I am excited!
Well SY, you seem to be the expert on these, what kind of drive do they like (both SE and PP, I bought enough for both)? Will a simple grounded stage do or is something beefier required? I've got tubes like 6922, 6N1P, 6H8C, 6EJ7, 6N6P saved up, as well as some of the Group Buy Aikido boards.
Re: OK, SY, they're here!
The 6BG6 is a rebottled 807. Here is the schematic of an 807 project I did. I used the 6SN7 as a cathode follower driver. This can source enough current so that slew rate limiting isn't a problem. With fixed bias, the 807s can slip into AB(2) transparantly. Xfmr saturation is more of a problem than clipping when you really crank it.
leadbelly said:
The 6BG6 is a rebottled 807. Here is the schematic of an 807 project I did. I used the 6SN7 as a cathode follower driver. This can source enough current so that slew rate limiting isn't a problem. With fixed bias, the 807s can slip into AB(2) transparantly. Xfmr saturation is more of a problem than clipping when you really crank it.
Hi Tubholics! Alle these refs are subs of the 6L6 beam tetrode structure build in the late 30' . The main difference from 6L6 to 807 and 6BG6 is socket or pinout (top cap) . I tried many tests with Tungsol 6BG6G , 6L6GC and others and finally swop all my amps to 807 because of the large stock i found (HYTRON 120pcs) . I can guarantee these to be the coolest i have ever seen and heard . I sold my 6l6 to Marshall lovers so that they can save their vintage gear !
Interesting Thread,
I have an urge to tinker as always, If I am reading this correctly,
6BG6GA can sub for 6L6 with just a couple minor pin-out changes?
I looked at the Pin outs for both tubes, If I am reading it right, Would This Conversion Be correct?
I have an old project that never worked right, SOOooo I was thinking, Pull out the 6L6, Swap a few wires and Give it a go.
Circuit is of course, Fender Champ AA746 based, 5K OPT Transformer is rated 100 Hz to 20 KHz -2 dB at 5 watts with 40 ma.
I regularly Run 6L6s in this unit with no overheats of problems,So with this OPT that can easily handle 60ma, Will this come close to being possible?
Trout
I have an urge to tinker as always, If I am reading this correctly,
6BG6GA can sub for 6L6 with just a couple minor pin-out changes?
I looked at the Pin outs for both tubes, If I am reading it right, Would This Conversion Be correct?
I have an old project that never worked right, SOOooo I was thinking, Pull out the 6L6, Swap a few wires and Give it a go.
Circuit is of course, Fender Champ AA746 based, 5K OPT Transformer is rated 100 Hz to 20 KHz -2 dB at 5 watts with 40 ma.
I regularly Run 6L6s in this unit with no overheats of problems,So with this OPT that can easily handle 60ma, Will this come close to being possible?
Trout
I'm considering trying to use those 6BG6s as replacements for the 8417s in my Bogen (2 output tubes, 60W), since the 8417 has the same pinout as the 6L6, the 6BG6s are capable of handling high plate voltages, and because they're cheap enough to experiment with.
I know I'm going to need bias supply mods, how much bias voltage do you think these would need if they're run at around 600V on the plates and 300V on the screen grid? It runs about -17.5V bias with the 8417s, I'm going to be rebuilding the bias supply with a voltage doubler and individual bias controls for each tube.
-Darren
I know I'm going to need bias supply mods, how much bias voltage do you think these would need if they're run at around 600V on the plates and 300V on the screen grid? It runs about -17.5V bias with the 8417s, I'm going to be rebuilding the bias supply with a voltage doubler and individual bias controls for each tube.
-Darren
Trout said:
Yes, the sockets have a different pinout and the 6BG6 has a plate cap. Some people think that's an advantage (I'm one of them). Grab a data sheet from a tube manual of from Frank's site and it will be obvious how to do the rewire.
As for your tubes, I don't have them in front of me for comparison, so I'm incompetent to comment about that. I can just attest that the cheap ones at SND really are what they claim.
A standard 6BG6 is an 807 with an octal base on it. It (and the 807) are derivitaves of the 6L6GB. In fact most of the WWII era and before 807's, 6BG6's and 6L6GB's all have the same guts in them and work about the same. These tubes will NOT take the abuse that an amp designed for an 8417, 7027 or 6L6GC will dish out. They will work fine in amps designed for 6L6GA or 6L6GB. They should do well in a Champ type amp. This applies to all coke bottle shaped 6BG6's and possibly some straight sided ones.
The "Super 6BG6GA" sold by SND apparently has upgraded guts in them and can take up to 30 watts dissipation. This is based on what I have heard here and on their data. I have not tested their tubes.
I know that as TV sets got bigger and brighter and color TV's became popular (early 1960's) the horizontal output tube was a high failure component. This tube must operate at full power for several hours a day. It was not uncommon to replace it every 6 months. Tube manufacturers often upgraded their sweep tubes without changing the ratings or documentation. Sometimes the entire guts were swapped for those of another tube to increase reliability.
As TV sets migrated to solid state, tube manufacturers were seeing diminished production volumes, so there was some consolidation of product. It was not uncommon in the early 1970's to see the same guts in several different tubes. Often this was done to lower production costs. Total compatibillity was not always guaranteed. I worked in a Philco authorized service shop in the early 70's. I remember seeing service info that showed whose tubes to use when repairing Philco TV's.
In my sweep tube testing (so far limited to a few types) I have now seen at least 9 different types of 6AV5GA's including 3 different RCA's and 3 different GE's. The 6AV5 is rated for 12 watts. Some of these begin to glow red at 15 watts, and some are quite happy at 30 watts. Same deal with 6CD6GA.
If you are going to push a 6BG6 to dissipations above 20 watts make sure that you have ones that can take it, or test carefully in a circuit that you can afford to blow up.
The "Super 6BG6GA" sold by SND apparently has upgraded guts in them and can take up to 30 watts dissipation. This is based on what I have heard here and on their data. I have not tested their tubes.
I know that as TV sets got bigger and brighter and color TV's became popular (early 1960's) the horizontal output tube was a high failure component. This tube must operate at full power for several hours a day. It was not uncommon to replace it every 6 months. Tube manufacturers often upgraded their sweep tubes without changing the ratings or documentation. Sometimes the entire guts were swapped for those of another tube to increase reliability.
As TV sets migrated to solid state, tube manufacturers were seeing diminished production volumes, so there was some consolidation of product. It was not uncommon in the early 1970's to see the same guts in several different tubes. Often this was done to lower production costs. Total compatibillity was not always guaranteed. I worked in a Philco authorized service shop in the early 70's. I remember seeing service info that showed whose tubes to use when repairing Philco TV's.
In my sweep tube testing (so far limited to a few types) I have now seen at least 9 different types of 6AV5GA's including 3 different RCA's and 3 different GE's. The 6AV5 is rated for 12 watts. Some of these begin to glow red at 15 watts, and some are quite happy at 30 watts. Same deal with 6CD6GA.
If you are going to push a 6BG6 to dissipations above 20 watts make sure that you have ones that can take it, or test carefully in a circuit that you can afford to blow up.
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