Bare Knuckle Pickups Forum
Forum Ringside => Guitars, Amps and Effects => Topic started by: Tricalibur on April 05, 2007, 07:23:33 PM
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So im pretty sure I want a Matamp GTL custom 140 watt guitar head and im just wondering what the tonal differences are between EL34's and 6550's. Ive heard people say that the 6550's are more 'fogged' or bassy and that EL34's have more 'bite' and midrange grind, but what does all of that mean? I relay am looking to get the tone of 'The Sword' or 'Heavy lord' and im pretty sure both of those bands use Matamp or Orange amps. Most likely with EL34's in the power section, but i want something that will eb a little bit different form the proto-typical stoner / doom amp so im thinkin 6550's will be what i want. PLus you get more wattage.
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6550s have a lower & tighter bass response than EL34s, there is nothing foggy/blurred about them at all. think tight, punchy and lots of headroom.
EL34s have more compression and forward midrange presenatation.
I personally like 6550s for all metal styles, they're just ballsier.
:twisted:
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Well think of 6550s to be in the Engl/Recto corner and EL34 in the Marshall/Orange ballpark.
As HTH said, for some metal styles, 6550s are better, but this is not a must, as there are metal tones that do have mids aplenty.
Would the option just be the stock tubes or a different amp configuration? If it's just the tubes why not buy it with 6550s and get a set of EL34s right after to swap and try?
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6550 : american
el34 : british
thats how it was described to me.
el34's have lower headroom, so they saturate and compress alot faster than 6550's. They have less bass definition and less overall clarity. (clarity 90% depends on the amp itself though.) When they break up, it gets VERY compressed and sounds kinda fuzzy... my friend described it to me as being like 70's rock when they were playing small non master volume amps set to full volume.
6550's have way deeper bass (they can be used in bass amps), more top end bite, more headroom so your preamp supplies most of the distortion. They're also amazingly tight and clear. Peavey 5150's have them. Random fact: they were hendrix's fav tube.
in my opinion, i'd take 6550's for metal and el34's more for a rock situation. Though if you like poweramp breakup with 6550's, be ready to kill some small animals with your volume :twisted:
amps with el34's: marshalls... except for the late 80's early 90's designed ones... like the jcm900.
some oranges use them... but orange likes to switch alot between el34's, el84's, 6550's, 6v6's and kt88's... depends what you specify.
So compressed sound, lots of mids.
Amps with 6550's... ampeg bass amps... peavey 5150... not alot of people use them. Mesa and Engl both use either 6l6's or el34's, and alot of companies are also using 6v6's. I'll look around and try and find more amps that use them.
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One small correction, Peavey 5150 amps use 6L6 tubes not 6550 tubes.
But apart from that what was said above is sound advice.
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Unfortunately, Matamp no longer make the GTL head, but do a combined GTO/GTL head in one box, the GT1. It's been getting some very good reviews from the Matamp users.
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One small correction, Peavey 5150 amps use 6L6 tubes not 6550 tubes.
But apart from that what was said above is sound advice.
damn i could have SWORN they used 6550's... i never knew an amp with 6l6's could sound so tight...
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One small correction, Peavey 5150 amps use 6L6 tubes not 6550 tubes.
But apart from that what was said above is sound advice.
damn i could have SWORN they used 6550's... i never knew an amp with 6l6's could sound so tight...
ENGL Powerball ring any bells?
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Actually most high gain amps seem to use 6L6 tubes. The Mesa Rectifiers, Engl Powerball, Peavey Triple XXX and 6505 (used to be the 5150) all use 6L6 tubes.
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Actually most high gain amps seem to use 6L6 tubes. The Mesa Rectifiers, Engl Powerball, Peavey Triple XXX and 6505 (used to be the 5150) all use 6L6 tubes.
Soldano do too. Off the top of my head, only VHT use 6550s as standard though I'm sure there are others.
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Engl Invaders use EL34s if I remember right.
And how about KT88s - How do they sound?
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Unfortunately, Matamp no longer make the GTL head, but do a combined GTO/GTL head in one box, the GT1. It's been getting some very good reviews from the Matamp users.
Yeh thats probably what id end up getting if they couldnt buld me on from scratch. Im thinkin that if I got 6550's the amp config would have to be changed as well so im not sure if it oculd eb enterchangeable between the the two tube types.
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And how about KT88s - How do they sound?
kt88's are the uber tube. They take their own socket (5-10$ mod to your amp) and have a super high current draw so they might not be compatible with your transformer. They're probably the biggest bottle powertube out there... From what i've read, theyre the british 6550. But they have WAY more current draw and have REDICULOUS headroom. They're loved by hifi amp people because they just dont $%&#ing break up. If you want enough clean headroom to kill kittens, this is the tube for you. Personally, if i had an amp and wanted to use kt88's, i'd only use a pair of them and not a full quartet... oh and one last thing.. they will cut a hole in your wallet.
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All the Mat's are built from scratch to your specs, so I don't think you'd any problem getting 6550's fitted from the start. Don't know how flexible the biasing would be to swap between the two valve types (EL34's & 6550's). I'm sure if you ask nicely, they'll sort something out for you. ;)
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And how about KT88s - How do they sound?
kt88's are the uber tube. They take their own socket (5-10$ mod to your amp) and have a super high current draw so they might not be compatible with your transformer. They're probably the biggest bottle powertube out there... From what i've read, theyre the british 6550. But they have WAY more current draw and have REDICULOUS headroom. They're loved by hifi amp people because they just dont #$%!& break up. If you want enough clean headroom to kill kittens, this is the tube for you. Personally, if i had an amp and wanted to use kt88's, i'd only use a pair of them and not a full quartet... oh and one last thing.. they will cut a hole in your wallet.
sorry, but this is just not true - KT88s will plug right into an EL34 amp. they draw 1.6A each compared to 1.5A each with an EL34 (100mA per valve extra is not gonna worry your mains transformer).
most KT88s and 6550s these days are the same thing, just rebranded or rebottled (i.e. same guts). that said, when you get the real thing, KT88s have a slightly more aggressive midrange than 6550s but are essentially very similar.
I had a quad of KT88s in a 2203 and it sounded great, VERY punchy. Apparently Billy Corgan used KT88s in his 2203 for Siemese Dream.
:twisted:
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sorry, but this is just not true - KT88s will plug right into an EL34 amp. they draw 1.6A each compared to 1.5A each with an EL34 (100mA per valve extra is not gonna worry your mains transformer).
most KT88s and 6550s these days are the same thing, just rebranded or rebottled (i.e. same guts). that said, when you get the real thing, KT88s have a slightly more aggressive midrange than 6550s but are essentially very similar.
I had a quad of KT88s in a 2203 and it sounded great, VERY punchy. Apparently Billy Corgan used KT88s in his 2203 for Siemese Dream.
:twisted:
Yeahhhh, my amp is a 6l6 one, and so are my future amps :roll: ...
...so i have to watch out for the transformer and socket stuff... never knew that about el34 amps though. Quetsion though... why are 4 tube el34 amps rated at 100w, and 4 tube kt88's rated at 180w?
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Thanks for the input on this thread, HTH. I'm gonna get some 6550s for my TSL. Sounds like it would go a long way to fix what I think the imperfections in the sound are (been getting great tones out of it with an EQ in the FX loop but not....quite........'there')
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if you put a quad of KT88s or 6550s in an EL34 amp you'll not really get any more output. EL34s have a maximum dissipation 25w a piece whereas 6550s and KT88s (depending on what you get) are 42w each. to get the full rated power, you need an output transformer that will handle that wattage.
what you WILL get though is a tonal change - 6550s and KT88s will just give you a much lower and tighter bass with lots of punch and headroom. this sounds great if you run any kind of gain with an aggressive style. downtuners will love this too.
Newer EL34 amps will have a fairly reasonable plate voltage (450v'ish) so you're fine for running 6550s and KT88s without any modifications. 6L6 amps otoh will often have the bases wired slightly different (pin 1 used as a tie point for the bias snubber resistors) so don't plug other valves in without checking this out first.
:twisted:
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quick newbie question here, but are 6550s, EL34s, 6L6s etc. preamp or poweramp valves?
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All the Mat's are built from scratch to your specs, so I don't think you'd any problem getting 6550's fitted from the start. Don't know how flexible the biasing would be to swap between the two valve types (EL34's & 6550's). I'm sure if you ask nicely, they'll sort something out for you. ;)
Yeh thast pretty much what i would wnat i spose. If you go to the Emectric Amp site here; www.electricamp.com you can see they have an amp model that is 140 watts with 6550's. Thats pretty much what i want but with a GTL. Im just not sure though if I would rather have EL34's or 6550's. To get the full 140 watts out of an EL34 amp then I would need 5 -6 of the tubes AND a 140 watt transformer correct? Where as if I had 6550's I would only need about 4?
BLOODMOUNTAIN; Those are all Poweramp tubes ;].
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All the Mat's are built from scratch to your specs, so I don't think you'd any problem getting 6550's fitted from the start. Don't know how flexible the biasing would be to swap between the two valve types (EL34's & 6550's). I'm sure if you ask nicely, they'll sort something out for you. ;)
Yeh thast pretty much what i would wnat i spose. If you go to the Emectric Amp site here; www.electricamp.com you can see they have an amp model that is 140 watts with 6550's. Thats pretty much what i want but with a GTL. Im just not sure though if I would rather have EL34's or 6550's. To get the full 140 watts out of an EL34 amp then I would need 5 -6 of the tubes AND a 140 watt transformer correct? Where as if I had 6550's I would only need about 4?
Just a quick note. Electric amps are not Matamp. Even though they look similar they are a US made amp with no ties to Matamp. To look at the Matamp site use http://www.matamp.co.uk/
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Just a quick note. Electric amps are not Matamp. Even though they look similar they are a US made amp with no ties to Matamp. To look at the Matamp site use http://www.matamp.co.uk/
truesay. Electric is the american bar-stewardized version of matamp. They do loose copies which don't really sound similar to the originals; they have more of their own sound. However, the electric amp company is also a distributor of matamp products, so if you want a matamp in the US, you'd typically go to them.
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If you want the punch of a 6550 and the mid range growl of an EL34, why not try a set of KT77's. They're much closer to EL34's than the new E34L's and should go into an EL34 powered amp with just a minor tweak of the standard bias settings.
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However, the electric amp company is also a distributor of matamp products, so if you want a matamp in the US, you'd typically go to them.
I'm pretty certain that they are not the distributor anymore. They used to be, but I believe there was a big falling out - if you look at the amps they make you can perhaps guess why!
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Well I just got my Tungsol 6550s ordered.
Should be here tomorrow. Then biassing. Happy happy joy joy.
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Well I just got my Tungsol 6550s ordered.
Should be here tomorrow. Then biassing. Happy happy joy joy.
Are you biasing the amp yourself? - just making sure you know that the bias circuit will most likely need altered slightly to give the correct bias range for 6550s.
:twisted:
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Well I just got my Tungsol 6550s ordered.
Should be here tomorrow. Then biassing. Happy happy joy joy.
Are you biasing the amp yourself? - just making sure you know that the bias circuit will most likely need altered slightly to give the correct bias range for 6550s.
:twisted:
Well I was gonna, yeah. TSLs are a piece of piss to bias.
But please elaborate!
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However, the electric amp company is also a distributor of matamp products, so if you want a matamp in the US, you'd typically go to them.
I'm pretty certain that they are not the distributor anymore. They used to be, but I believe there was a big falling out - if you look at the amps they make you can perhaps guess why!
yeah, the "real" matamp website had something on it a while ago about the usa website not being allowed to sell/distribute matamp or something. if I remember correctly.
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yeah, the "real" matamp website had something on it a while ago about the usa website not being allowed to sell/distribute matamp or something. if I remember correctly.
oh no! this means i'll never get one :(
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I believe there is a new US distributor (and it is not Junior's :shock: )
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^ aye, just to clarify, when I said "the usa website", i meant the one people had been talking about. i doubt matamp would say "we got screwed there before, that's it, no more sales to the USA!"....
:lol:
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quick newbie question here, but are 6550s, EL34s, 6L6s etc. preamp or poweramp valves?
All poweramp tubes
The only preamp tubes you are likely to see or hear about are
12AX7 - called ECC83 in UK
Also some lower gain applications may use
12AU7 - ECC82
12AT7 - ECC81
You may enjoy reading this
http://www.marshallamps.com/resources/secret_life_of_valves/secret_life_valves.asp
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^ aye, just to clarify, when I said "the usa website", i meant the one people had been talking about. i doubt matamp would say "we got screwed there before, that's it, no more sales to the USA!"....
:lol:
http://www.matamp.com/matamp-distributionUSA.html
article explaining!
now i just have to find a distributor near me.
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^ aye, just to clarify, when I said "the usa website", i meant the one people had been talking about. i doubt matamp would say "we got screwed there before, that's it, no more sales to the USA!"....
:lol:
http://www.matamp.com/matamp-distributionUSA.html
article explaining!
now i just have to find a distributor near me.
the way Jeff @ Matamp is described in that article does not mesh with the Jeff I've known for the past 5+ years. I'd take it with a pinch of salt, especially since they've basically lifted Matamp's entire image (and most likely the circuit too)
:evil:
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Quite practically I was able to compare my JCM900 50Watt EL34 amp with the other guitar player's JCM 900 50Watt 6l6 amp.
The descriptions pretty much sum it up. The 6l6 was a bit nicer for clean and blues, the EL34 better for rock and metal sounds.
But the differences are fairly small. To be honest, I really think you can disregard them on modern high gain amps (like ENGLs or Peaveys). Those amps seem to get most of their sound from the preamp and just try to have a fairly neutral sounding power amp section. These ain't the days anymore where you're achieve your sound Hendrix style, i.e. cranking a full stack all the way and using volume and tone pots for finetuning.
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Yeh the way Ive heard it from Joel at Electric is that they were once the sole US distributor but they then decided to break off and become their own company making their own amps and such. Matamps can still be bought in the US from here; www.motorcitymatamp.com.
Just to clarify, Im pretty much basing my needs out of a Matamp off of what i have seen on the Electric website realy but i just want the real deal and not a close copy.
So has anyone here ever tried KT77's?
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So has anyone here ever tried KT77's?
just the current JJ ones - they were fine, very much like the JJ E34L imo.
a cynic would say they're the same valve relabelled :roll:
:twisted:
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the way Jeff @ Matamp is described in that article does not mesh with the Jeff I've known for the past 5+ years. I'd take it with a pinch of salt, especially since they've basically lifted Matamp's entire image (and most likely the circuit too)
:evil:
yeah, that sounds a bit fishy to me. haven't dealt with him myself, but by all accounts, matamp is run the way companies should be run, with great guys doing the running.
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Matamp UK: http://www.matamp.co.uk/home.htm
Matamp Canadian Distro: http://www.g-spot-music.com/matamp.html
Matamp US Distro: http://www.motorcitymatamp.com/
Matamp.com has nothing to do with Matamp any longer.
Electric Amps have something like a 6+ month order period, and there's plenty of people who have paid in full and waited far longer (just do a search on HC/The Gear Page/Plexi Palace forums etc).
Matamp in the UK have a turn around of around 1 month for a custom, hand built amp.
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Billy Corgan used a 2203?
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Billy Corgan used a 2203?
I know nothing about him or his band, I just remember when I sold my 2203 with KT88s installed the guy that bought it was wetting himself over it saying he'd been searching for ages for a such an amp (obviously didn't know that you can just plug KT88s in any 2203 with the appropriate bias adjustments).
I've since seen the same thing mentioned on the net quite alot.
He obviously didn't use their built-in overdrive since his sound was all about the Big Muff PI.
:twisted:
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Quite practically I was able to compare my JCM900 50Watt EL34 amp with the other guitar player's JCM 900 50Watt 6l6 amp.
The descriptions pretty much sum it up. The 6l6 was a bit nicer for clean and blues, the EL34 better for rock and metal sounds.
But the differences are fairly small. To be honest, I really think you can disregard them on modern high gain amps (like ENGLs or Peaveys). Those amps seem to get most of their sound from the preamp and just try to have a fairly neutral sounding power amp section. These ain't the days anymore where you're achieve your sound Hendrix style, i.e. cranking a full stack all the way and using volume and tone pots for finetuning.
Thanks for posting those observations Alex, as the owner of two 6L6 based amps ( and having never tried an EL34 based amp ) - I have long been curious about what I may have been missing. Sounds like I have the right option for me anyway. It was nice to hear that the difference was subtle though, we gear heads do not like to think there is something we're missing ! :lol:
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i'm glad this thread was resurrected... man were some of my comments so wrong. I've given up listening to people and been doing my own research now, so im cleanin up now.
6550's and kt88's have ALL THE SAME RATINGS, hell, theyre pretty much the same thing.
The only difference is in the pins.
In a 6550, the supressor grid is attached to pin 1; and cathode to pin 8.
in a kt88 (which stands for "kinkless tetrode" but is actually a pentode), the supressor grid AND cathode are attached to pin 8; and pin 1 is attached to nothing.
other than this, they are IDENTICAL in every rating.
http://www.mclink.it/com/audiomatica/tubes/kt88.htm
http://www.mclink.it/com/audiomatica/tubes/6550.htm
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I have heard though from Tube sellers KT88 have sweeter mids
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I have heard though from Tube sellers KT88 have sweeter mids
oh they definately sound different, but construction wise the only thing that should be different is the pin locations and sometimes size of the bottle.
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Yeh the way Ive heard it from Joel at Electric is that they were once the sole US distributor but they then decided to break off and become their own company making their own amps and such.
Not quite. he was sacked as the US distributor after trying to register Matamp as a trademark in the US behind Jeff's back, and without his permission. A bit cheeky. Jeff took legal action, won and removed his distributorship.
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6550s have a lower & tighter bass response than EL34s, there is nothing foggy/blurred about them at all. think tight, punchy and lots of headroom.
EL34s have more compression and forward midrange presenatation.
I personally like 6550s for all metal styles, they're just ballsier.
:twisted:
When pushed, 6550s will be quite foggy though....
The way I'd go is KT88s if you go that route... they are military grade 6550s and should be able to be used as a replacement for 6550s with proper bias adjustments.
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6550s have a lower & tighter bass response than EL34s, there is nothing foggy/blurred about them at all. think tight, punchy and lots of headroom.
EL34s have more compression and forward midrange presenatation.
I personally like 6550s for all metal styles, they're just ballsier.
:twisted:
When pushed, 6550s will be quite foggy though....
The way I'd go is KT88s if you go that route... they are military grade 6550s and should be able to be used as a replacement for 6550s with proper bias adjustments.
I can't say thats what I've ever found with 6550s, as always ymmv.
KT88s back in the day of GEC could be considered military grade equivalents of 6550s, but not with current production KT88s.
With modern KT88s you're more likely to get 6550 guts in a KT88 bottle (i.e. the same valve)
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I can't say thats what I've ever found with 6550s, as always ymmv.
KT88s back in the day of GEC could be considered military grade equivalents of 6550s, but not with current production KT88s.
With modern KT88s you're more likely to get 6550 guts in a KT88 bottle (i.e. the same valve)
true say. the kt88 originally had a higher plate voltage than the 6550, but these days they're identical except for pins.
Brits invented the kt88 as an upgrade of the kt66 (which was the british answer to the bad construction of the 6l6), and 6550's were invented by the americans as an upgrade of the 6l6 after seeing what the brits can do. Yes theres more to this story, but thats the basics of it.
However, 6550's do get foggy, but i've only ever heard the fog in bass amps when they're pushing super low frequencies, like an ampeg svt. Everybody knows what an overdriven SVT sounds like. 6550's stay pretty clear for guitar though :)
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I can't say thats what I've ever found with 6550s, as always ymmv.
KT88s back in the day of GEC could be considered military grade equivalents of 6550s, but not with current production KT88s.
With modern KT88s you're more likely to get 6550 guts in a KT88 bottle (i.e. the same valve)
true say. the kt88 originally had a higher plate voltage than the 6550, but these days they're identical except for pins.
Brits invented the kt88 as an upgrade of the kt66 (which was the british answer to the bad construction of the 6l6), and 6550's were invented by the americans as an upgrade of the 6l6 after seeing what the brits can do. Yes theres more to this story, but thats the basics of it.
However, 6550's do get foggy, but i've only ever heard the fog in bass amps when they're pushing super low frequencies, like an ampeg svt. Everybody knows what an overdriven SVT sounds like. 6550's stay pretty clear for guitar though :)
Ahh, we're talking overdriven 6550s in bass amps - well thats a different story altogether. In guitar amps there really isnt the low end to get that fuzzy bass imo.
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I can't say thats what I've ever found with 6550s, as always ymmv.
You just haven't pushed them hard enough... but that's hard to do. It's all a matter of how much you abuse them. Last time I did that (1969 Marshall Major with a Keeley Java Booster) it cost me a total of $600 in repairs and new tubes as I melted some tube sockets in the amp and some 2000 volt capable wiring.
KT88s back in the day of GEC could be considered military grade equivalents of 6550s, but not with current production KT88s.
With modern KT88s you're more likely to get 6550 guts in a KT88 bottle (i.e. the same valve)
Actually it is still as true in this day in age as it was 35 years ago... it's just the KT88s got cr@ppier, but so did the 6550s as well.
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The EL34 is a pentode, whereas KT66, KT77, KT88, 6L6 and 6550 are beam tetrodes which work on a slightly different principal to a pentode. One feature of the beam tetrode is that the screen grid is wound concentrically with the control grid ie its in the "shadow" of the control grid. As less electrons strike the screen grid, beam tetrodes have lower screen currents than pentodes (which is why screen grid resistors are typically higher for EL34s than 6L6s). Lower screen current means more efficiency (screen current doesn't contribute to output power) and less third harmonic distortion, which I expect part of the reason that EL34 have a crunchier sound.
EL34s have quite high transconductance, ie they don't require as much drive voltage as say 6550s or KT88s. Thus is you put 6550s in a Marshall you will get more head room as a greater signal is required to clip the output stage.
Incidentally Marshall made an amp called the Park 70 which used two KT88s, which from what I can see from working on one is simply a Park 45 which uses EL34s, with KT88s in it.
By the way the new JJ-KT77 is a genuine beam tetrode as I have spoken to someone who broke one open and disassembled the internal structure and NOT a repackaged EL34. I think the rumours that the JJ-KT77 was actually a pentode came from a valve vendors web-site that statesd that as the plate curves did not have a kink in them it couldn't be a tetrode (true but it could be a BEAM tetrode). KT actually stand for "kinkless tetrode"! I notice they have now amended their web-site.
By the way we have been doing quite a lot of listening to different valves, especially comparing the JJ-KT77 with EL34s. We really like the sound of the KT77 as it has the extended bass and smoother sound of a beam tetrode. KT77s will work fine in all EL34 loaded amps, so its good to have another option available.
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jpf,
Are the new JJ KT77s using standard pin sizes now? - the first run were using thinner (mil-spec according to Eurotubes) pins and many amps needed their sockets retensioned.
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Yes the JJs are fortunately now using standard sized pins, although I expect there is still some old stock knocking about.
The problem with the pins on the JJ valves was that there was no taper on the end of the pins so if you were not careful about how you inserted the valves into their sockets you could damage the socket. JJ's answer to this was to make the pins thinner! We stopped using JJ octal valves because of this as even if we retensioned the sockets we couldn't guarantee that the valves would not fall out. My guess is that the main motivation for the change in the pin size came from the hi-fi community who don't tend to throw their amps into the back of transits etc. I think Groove Tubes supply their own tapered pins for the JJ-Valves they re-brand.
Whether the thinner pins are Mil-spec or not, well who knows. I haven't had any dealings with Eurotubes, however as they only stock JJ tubes I suspect they are NOT the most unbiased source of information on JJ-tubes. Incidentally I installed a quad of JJ-KT88s into a JCM800 that where supplied by Eurotubes and the matching was all over the shop, although this could have been due to being clattered around in transit.
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By the way we have been doing quite a lot of listening to different valves, especially comparing the JJ-KT77 with EL34s. We really like the sound of the KT77 as it has the extended bass and smoother sond of a beam tetrode. KT77s will work fine in all EL34 loaded amps, so its good to have another option available
. My earlier post about the KT77 didn't work,so.....The JJKT77 has been a saviour for me .They sound like a cross between a 6L6 and a EL34.Or halfway between them.Nice.
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EL84 - Compressed british lots of mids, sparkling cleans think Bryan May
EL34 - Classic Rock, 70s and 80s Heavier Styles
6CA7 - EL34's American Military version, as used by EVH.
KT77 - Higher plate voltage version of EL34, Extended bass and highend
KT88 - Huge plate voltage handlin extended bass and highs kinda scratchy
6V6 - Fender Deluxe Reverb, sounds like smaller 6L6's
6L6 - Vintage 6L6 sound, think country etc.
6L6GC - High power handling version, think Mesa/Boogie etc..
5881 - European 6L6 as used by ENGL
6550 - American KT88, harsher less mids than KT88 still huge sounding
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Interestingly, the Orange Thunderverb head uses 6550s I think...
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Very interesting read, allthough i kind of expected to find more talk about
MULLAAARDS !!!!
Ok cant help it, just needed to get out.......
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i want to post a note about kt88s vs 6550's.
ORIGINALLY the kt88 was designed to have a higher plate voltage.
Presently, most current production kt88's have the same plate voltage as 6550's, the only difference between them being a pin connection.
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The pin out of 6550s and KT88s is the same.
The original data sheets for the KT88 and 6550 list the maximum plate voltage as 600V (later data sheets list 800 V for the KT88), however the main difference between these valves is that the 6550 has a much lower screen voltage rating of 400 V versus the KT88 (600 V). The KT88 was designed for ultra-linear operation, and in this mode the screens and plate are at virtually the same voltage.
Amps that use 6550 with high plate voltages use much lower screen voltages. For example I was working on a Marshall 2001 bass amp which uses 8 (yes eight!!) 6550s to generate 375 Watts. The plate voltage was around 670 V (careful now), however the screens were run at around 350 V. Ampeg use a similar arrangement in the SVT and Orange do the same in the Thunderverb.
The Marshall Major runs the output stage in ultralinear configuration with a B+ of around 650 V, so it is not advisable to run 6550s in this amp as the creen voltage is way too high.
So the 6550 and KT88 are not equivalent valves. There is always a suspicion with Sovtek valves that the 6550 and KT88 are the same valve in a different package; as there are no datasheets for these valves you can't tell. However the winged-C and JJ-KT88s have the expected parameters for a KT88. Also the winged-C 6550 has the expected lower voltage ratings.
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The pin out of 6550s and KT88s is the same.
uhh, nope.
In a kt88, pin 8 is linked to the cathode and the screen, and pin 1 connects to nothing
in a 6550, pin 8 is exclusively linked to the cathode, and pin 1 to the screen.
pin 8 being linked to screen and cathode in kt88's would DEFINATELY have something to do with the ultralinear purpose because it would keep the screen and cathode the same :P
but, all this being said, i'm glad the winged "c" factory is making the kt88's and 6550's as different tubes instead of the same tubes with different packages.
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All the manufacturer's data sheets I have seen for KT88s and 6550s have the same pin out indicated ie the cathode and beam forming plates are tied together internally and to pin 8 (see http://tdsl.duncanamps.com/ for valve data or Svetlana web-site), as have all the examples I have seen of these valves.
Beam tetrodes, unlike pentodes, don't have a suppressor grid but the distance between the screen grid and the plate is proportioned to reduce the effects of secondary emission, and this is enhanced by beam forming plates which are tied to the cathode.
The pentode EL34 has the suppressor grid pin 1 and cathode pin 8 tied to separate pins. This makes it possible to tie the suppressor grid to a voltage other than that of the cathode, perhaps the raw bias supply as used in some Traynor amps.
I'm not sure if tying the beam forming plates of a beam tetrode to a voltage other than the cathode would be useful, and indeed it might disrupt how the valves functions. However there may well be some versions of the 6550 that have this pin out option, although my suspicion might be that these are in fact pentodes and not beam tetrodes. Pentodes are generally cheaper to manufacture.
This pin out option has NOTHING to do with ultralinear operation; it is the screen grid (pin 4) which is tied to the UL taps on the output transformer.
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here's a GEC datasheet showing the KT88 pinout... http://www.triodeel.com/kt8856p1.gif
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So what are the tonal differences between the 6L6 and 5881?
I've narrowed it down to these two for my new head (Egnater mod50) and style (hardcore), my 5150 II uses 6L6's and although i like them, i would like a little more mids in them, would 5881 sort this?
What's a good brand to get?
i know tung sols are but they're £65!!!! each on watford valves
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thanks for the informative post JPF :)
you probably just saved me alot of hassle later in life.
and the difference between 5881s and 6l6's i've found is that 5881s are a more sterile version, less bass, less highs. A very boring tube for me where i like extended bass. Mind you im running mesa/sovtek ones, which arent good tubes in the first place.