Oppinion on 807 and 6L6 ga
R.Pit
I'm going to build an amp for my sub-woofer speaker system.
The idea is SE stereo for the satelites and PP mono for the woofer.
Now I have 2 Valvo 807's Reichseigentum (ex german army) and
2 Sylvania JAN CHS 6L6GA. All brand new !!
Just on power ratings I'd say 807 for PP and 6L6 for SE.
But wich one sounds best in SE?
I don't want to run the tube ( all 4) to hot , for long life.
Rectivication is going to be tubes also.
The only SS I use is for heater PSU.
Any oppinions?
Ronald
Fred Nachbaur
For the PP mono I agree, 807 is hard to beat. You'll get lots of punch
for the woofer, assuming you get a good, over-rated OPT.
But for the SE, I have misgivings about 6L6. Terrific tube for PP, but
doesn't do so well in SE (unless maybe you use triode connection - I
never did that so can't say).
Triodes do well in SE, you might see if you can find 809 or 811 (both
similar in appearance to 807, but larger). You'll need a pretty
high-voltage supply, also a good driver since these pretty much have to
run in Class A2. If you want to stay in Class A1, maybe 845... but they
seem to be at a premium these days.
HTH
Fred N
R.Pit wrote:
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Tim
> doesn't do so well in SE (unless maybe you use triode connection - I
> never did that so can't say).
I made a 6L6*GC* SE amp, a good 5W or so.. I can't say for sure
how good it is, because it has a metric sh&tload of this weird
noise that I can't fix. Now that my scope's got a normal-sized
trace, I should try taking an electrical stroll trough it.
Tim
--
"WOOHOO! Who would've guessed reading and writing would pay off!"
- Homer Simpson
R.Pit
Maybe I have to go the other way around then , I know people that are
very happy with their 807 SE , they pull about 10 W out of it.
What can I expect from 2 6L6GA's in PP for a sub woofer? (30-125Hz ,
85dB/W/M , single vented band pass with a Visaton WSP21DV).
How much power may I expect?
For the PP OPT , I have a well sized EL34 tranny , I have to find out
about Raa .
Regards,
Ronald
"Fred Nachbaur" <fnac...@netscape.net> schreef in bericht
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Fred Nachbaur
Well, 6L6GA is essentially the same (ratings-wise) as 6L6, and according
to the RCA Receiving Tube Manual:
Max. dissipation: 19 watts (per valve)
At Vp, Vg2=250V, Vg1=-16V: class A1 PP, max. power 14.5 watts, Raa 5k
At Vp=360V, Vg2=270V, Vg1=-22.5V: class A1 PP, max. power 26.5 W, Raa=6.8k
Interestingly, Ia is given as 120/140 mA in the first case, and 88/132
mA for the second case (zero-signal and maximum-signal respectively),
tending to imply that it's dipping at least partially into Class AB1
even though the table says A1.
At Vp=360V, Vg2=225V, Vg1=-18V, Ia=78/142 mA: class AB1 PP, max. power
31W, Raa=6k.
Maximum recommended Rg1=100k (fixed bias), 500k (cathode bias).
Regards,
Tim
>
> Interestingly,
Interestingly, my rx tube manual (RC-26) says two current ratings,
88/132 and 88/140mA under 6L6 class A1 PP. Also, screen 5/15 vs.
5/11mA; the only two given differences I see in these two setups
is the load - 6600 vs. 3800 ohms. Rather odd how they both say
2% distortion, despite the lower impedance (though power is less,
26.5 vs 18W).
> At Vp=360V, Vg2=225V, Vg1=-18V, Ia=78/142 mA: class AB1 PP, max. power
> 31W, Raa=6k.
Whoops, my book says this is class AB_2_. :-) Grid is -18V,
but drive is 52V p-p, indicating peaks of up to +8V on the grids.
Suprisingly, distortion is still only 2%, so if you have a nice
solid direct-coupled CF driver, you could make a nice solid sub
amp with these tubes.
It should be noted that it doesn't say whether this is 6L6 or 'GC,
but since the AB1 'GC, though @ 450V, can push 55W, I think it's
safe to assume it's the plain.
On a similar subject, I had a wild thought to use my quad (which
appears to be matched!) of 6L6GAs as a stereo PP amp.. but this
matter doesn't concern any of you because it's nothing special...
Fred Nachbaur
Tim wrote:
>>[...]
>
> Whoops, my book says this is class AB_2_. :-)
Yeah, whoops. You're right, those wee numbers all look the same to aging
eyes.
> [...]
> It should be noted that it doesn't say whether this is 6L6 or 'GC,
> but since the AB1 'GC, though @ 450V, can push 55W, I think it's
> safe to assume it's the plain.
If your book is like mine, you have to look up to the previous table's
headers to see which set of data belong to which class of tube.
> On a similar subject, I had a wild thought to use my quad (which
> appears to be matched!) of 6L6GAs as a stereo PP amp.. but this
> matter doesn't concern any of you because it's nothing special...
Nothing special? An amp capable of pushing over 60 watts (or even more
if you like living on the edge) is pretty special in my book!
Fred N
Tim
> > appears to be matched!) of 6L6GAs as a stereo PP amp.. but this
> > matter doesn't concern any of you because it's nothing special...
>
> Nothing special? An amp capable of pushing over 60 watts (or even more
> if you like living on the edge) is pretty special in my book!
Nahh was thinking a conservative 20WPC.
Now that ya got me thinkin', I should use this pair of 7355s
("6V6 on steroids"), 40W into 5K (@400V) sounds nice to me...
As you said in another post, Hammond is conservative about
their ratings eh? So their 30W OPT - 5k primary, #1645 -
wouldn't be that bad a bet here?
OTOH, there's the appropriately rated 1650G or H, but that's
1.6K Ra-a past ideal.
As to the power source, maybe a 273CZ, 650VCT 150mA + heaters?
Chris Merren
http://groups.yahoo.com/group/tubetechnical/files/Schematics/66amp.gif
Let me know what you think...
Regards
Chris
Tim
I think I'm not a member. Why not post it to our favorite binary group?
(If you don't have access, you could send it to me and I could post it.)
Philip Lawrence
The 807 goes very well Se, i have made several. But i think the
6L6GC would too but the 6L6gA has much lower rating's. I imagine they
would be best as push pull.
Phil
R.Pit
"Chris Merren" <cer...@engineer.com> schreef in bericht
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R.Pit
And I think the screen voltage is way to high , so will Wg2.
"Chris Merren" <cer...@engineer.com> schreef in bericht
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Tube
Actually 6L6 and 807 is very similar and has almost the same characteristics,
I doubt there are any difference between those in a SE amp, probably there
are more differences between tubes from different manufacturers.
If you compare these you will see that the internal electrodes are indeed
very similar especially if they are from the same manufacturer. The main
difference is the top anode cap on the 807 giving low capacitance making it
useable on higher frequencies.
I used 807's in my first P-P amp pushing out ~100W in AB2 pushpull at 700V,
so this is indeed possible and would probably be OK for a SUB woofer amp if
you can get the output transformer.
One caution in using 807 or 6L6 is that the emission of the cathode is
marginal due to the low heater power, cathode stripping is well known on 6L6
and 807 in some circuits.
Hans
http://www2.gol.com/users/tube/tubeamplifiersindex.html
Richard S. McCown
history of the KT8 before. Anyone have an Osram book and know the
introduction dates of KT8, KT66?
The KT8 was a not very successful British attempt to emulate the
American type 807. The 807 was based on the RCA type 6L6 beam tetrode,
which had a long, fairly thin, anode and a carefully-aligned grid
structure. The 6L6 employed rapidly-accelerated electrons and short
electron paths. This made it efficient but its characteristic had a
distinct residual kink. It was a very successful valve but its
characteristic was not quite straight enough to give the ultimate in
audio quality at high output levels.
The KT66 was essentially a 6L6 redesigned with a larger cathode and a
shorter, fatter anode. The KT66 had less rapid acceleration, longer
electron paths, and almost no kink. It was ace for audio hi-fi but the
electrons took longer to reach the anode and were more open to influence
from magnetic, etc, fields on the way. Moreover, under HF conditions the
electron stream was not perfectly in phase with the grid signal and this
resulted in a loss of output power.
The KT8 was based on the KT66 but the longer electron path (compared to
the 6L6 and 807 types) was a disadvantage at the high radio frequencies.
Not a problem at AF but the KT8 was pretty useless above 15 MHz whereas
the 807 was still doing great things at 60 MHz.
In the end the British Services abandoned the KT8 in favour of the
American 807. Attempts to make 807s in the UK were largely unsuccessful.
The anode is made of plates, shaped to increase surface area and
blackened to radiate more heat. The base is ceramic indicating high
temperature operating and the need for good insulation.
The envelope is 47 mm in diameter and excluding the base pins it stands
115 mm tall.
I got this here,
http://www.r-type.org/exhib/aab0080.htm
it has a photo to worship :-)
Richard S. McCown
From: (François Yves Le Gal)
McCown) wrote:
Attempts to make 807s in the UK were largely unsuccessful.
which are some of the best examples of 807's I've ever come across.
--------
Yikes! Hi Francois.
I won't claim those as *my* words :-)
Are they beam tetrodes? By Mullard?
I'm a fan of British tubes and I'll take your word for it.
I know Mullard had EL38 (pentode) which I guess might be considered a
sweep tube? Crosses to 6CN6.
STC made a lot of 807 *types* 5B-245, 5B-255 etc... and I'm sure regular
807's.
Those little 5B-XXX's sure have long plates in them. I myself am only
interested in the audio end of this.
Maybe the guy just meant that the Brits didn't really improve on the 807
design, not that they couldn't build a good 807.
I believe someone else mentioned that the kink was above the AF's and
that would agree (maybe?) with what was said about the KT design not
doing as well in RF's as the 807.
I was hoping someone would comment if the guy had a sound theory on
the plates etc...