Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 67polara on July 03, 2011, 01:01:26 am
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I was just wondering if anyone has built an amp using the kt120's and what they thought of the sound quality? From what I have read they seem to put lots of power out but I haven't any idea as to how they sound. I "assume" they will sound kinda EL34 ish.
Tony
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I made one bass amp with 4xKT-120 tubes. It gives some 250-300 W output which is enough to any playing situation. I made my amp with UL configuration because I wanted as clean sound as possible. To me KT-120 sounds nearly 6550/KT88, not like EL34 which has more middles.
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Hey Tony,
I did talk to someone who put them in his Major. There are only a few manufacturers that build 6550s or KT88s that will last in this amp. With the KT120 power ratings, they were not even breaking a sweat. He said they were a lot like 6550's - at least in this application (620v plate, UL design). Lots of headroom and not as warm as a good KT88. He liked them but is going back to a good KT88 when these wear out - which might take a while! They are capable of gobs of power if you want to build the power supply. They do draw some current and generate a lot of heat. They are about an inch taller than a KT88/6550 and the Major tube retainers would not fit. They barely fit in a Major head cabinet so an off-the-shelf Marshall clone head will be too small. Not cheap, but none of the good big ones are! I'm not a big EH fan, but this looks like a very nice tube.
I did try the KT90 in my Major and did not like it at all. It was very EL34ish and not very musical to my taste. But again, we are talking about a unique circuit and that was several years ago. I think the factory was bombed and never reopened. Now EH is making them, so who knows.
What did you have in mind for the amp?
Jim
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Hey HarryK!
That was quite an undertaking! Do you have any pics?
Jim
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My homepage is www.bluetone.fi (http://www.bluetone.fi) The amp with 4xKT-120 tubes is Bluetone Ace of Bass in Bass amplifier section. I have come lazy and have not added schematics of it, but preamp is pretty same as Fender Bassman and power section a mix of Fender/Ampeg etc. Harry
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My homepage is www.bluetone.fi (http://www.bluetone.fi)
nice site and some cool stuff.
--DL
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Not to hijack but...Harry, WOW! You have quite a lineup in your catalog! Those are some really nice builds. The red chassis in the white tolex cab looks really cool. And are those shiny gold chicken head knobs on your Lead Jr. mahogany head? That is a beautiful build. Very, very nice work! I also want your workbench - complete with parts, of course!
I do have an on-topic question. What are you running for plate voltage on those KT120's?
Jim
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The piano store down the street had all these Smarvo heads for sale they were all dummies though. So I bought two of them, 50.00 for both. Well when I got it home I started looking for my next build. I came across the spec's on the KT 120 and was really impressed. I figure I can make a 100 + watt head with only 2 output tubes. That would leave me enough holes left for 6 12a'7's. I was thinking of a fender clean channel and a crunchy OD channel just for giggles w/reverb.
You know they also had about 10 Leslie's for sale for 40 to 100 ea. All different models, they were beautiful pieces of furniture. The wife said no, so I didn't get any of those. They also had tone cabs for sale for 60.00 ea. They were complete also.
Tony
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I came across the spec's on the KT 120 and was really impressed. I figure I can make a 100 + watt head with only 2 output tubes.
The wife said no, so I didn't get any of those.
Yeah, you could really push a couple of good KT88s to get you there. OR you could idle there with no sweat using two KT120's! Sounds like a plan!
The wife said no?!?!?!? The wife said NO? Who wears the pants in your family? You need to man up and tell her who's boss! You need to.... Oops, gotta go, my wife needs to get on the computer....
Jim
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Jim you just gonna let the wife tell you to get off the computer . oops gotta go now my wife needs mine
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Not to hijack but...Harry, WOW! You have quite a lineup in your catalog! Those are some really nice builds. The red chassis in the white tolex cab looks really cool. And are those shiny gold chicken head knobs on your Lead Jr. mahogany head? That is a beautiful build. Very, very nice work! I also want your workbench - complete with parts, of course!
I do have an on-topic question. What are you running for plate voltage on those KT120's?
Jim
Thanks! I like real wood and you can get mahogany pretty easily here in Finland. This wood is glued together of pieces, but it looks like original. I have sanded and oiled surface 5-6 times to get that gloss. My plate voltages are somewhere 470-490 V if I remeber right. You can drive those tubes with higher plate voltages, but it is not so easy to find a suitable PT for them.
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Finns don't get the blues! :laugh:
Nice stuff man!
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I came across the spec's on the KT 120 and was really impressed. I figure I can make a 100 + watt head with only 2 output tubes.
2 x GU-50 in PP
Anode 800v - Grid 300v = 120W
2 x GU-50 = € 14.00 (not matched)
http://www.zeitmann-tubes.com/MilitarySurplus/NosRussianMilitaryTubes/GU50.htm (http://www.zeitmann-tubes.com/MilitarySurplus/NosRussianMilitaryTubes/GU50.htm)
:icon_biggrin: :icon_biggrin: :icon_biggrin:
2 x KT120 = $ 89.95 (matched)
http://thetubestore.com/tungsolkt120.html (http://thetubestore.com/tungsolkt120.html)
10 x GU-50 = $ 49.99 (not matched)
http://cgi.ebay.com/FU-50-FU-50-LS50-GU-50-Pentode-10-tubes-China-NEW-/140551374622 (http://cgi.ebay.com/FU-50-FU-50-LS50-GU-50-Pentode-10-tubes-China-NEW-/140551374622)
(EL152 was the civil version of this tube)
you must also consider that this was a military specialized tube to be used in aircraft apparatus
perfect for moving bass or guitar amps
I think I'll try this very strong russian military tube
Kagliostro
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Finns don't get the blues! :laugh:
Nice stuff man!
they do if their butts touch ice... :icon_biggrin: