View Full Version : KT-120s... anyone using them?
Hi All,
I'm thinking that my GL-KT88 re-issues may need replacement next year, and I've been thinking about what I want to replace them with.
I have a Rogue Audio Stereo 90, and Mark from Rogue says that they perform very well in his amp, as well as being 'safe' to use in terms of heater current etc. The Stereo 90 is a fixed bias amp that can use EL-34w, KT88/6550s, KT-90s as well as KT-120s.
I am tempted, as they will be likely to last for quite a while at the operating point they would be run at in the Stereo 90.
Any views as to the KT-120 in a push-pull power amp?. Any other current prodution KT-88 types worth a look?. I think that the GL KT-88 reissue is damn fine tube for the money, and has been very consistent and reliable over the last year and a half of use. I haven't tried or heard the Shuguang Black Treasure series, but know they are well regarded, albeit very expensive.
Regards,
Alex
Speak to Marco or Anthony TD I think both really rate them and Anthony can get you them
Calling Marco... what were your impressions of the KT120? The reviews that I have seen are somewhat confusing (i.e. very positive or slightly scathing!).
Regards,
Alex
I've decided to take the plunge, given a very positive opinion from Mark O'Brien at Rogue Audion.
I've ordered a set from Hotrox, who are doing a matched quad for £116 inc vat and delivery, which seems like a sharp price!.
I'll let you all know how I get on.
Alex
Sorry, mate. I've only just seen this! You should've PM'd me... :)
Anyway, I think you'll love them, providing that your amp can maximise their advantages. They're so good, I wouldn't go near KT88s again, GECs or otherwise!
KT88s just sound soft and fluffy in comparison....
Pity though you didn't order them from Anthony, as he'd have given you a good deal, and his valves are all hand-selected and tested in optimum matched pairs and quads - not to worry.
Do let us know how you get on :cool:
Marco.
Thanks Marco.
A lot of manufacturers seem to have started fitting KT 120s - ARC, Rogue and others. I view this as an endorsement of their quality and performance.I hope that they are clearer, not harder sounding than KT88s. Hard to be sure from online reviews as most of the DIYAudio crowd seem to be using them in SET rather than PP amps. My amp is adjustable fixed bias, so matching is less of an issue than with some amps, but my experience of New Sensor product is that the factory matched quads are superbly matched anyway - most of my sets have been within a ma or less. They have obviosly invested heavily in QC and test gear.
I held off deciding to give them a try until I was sure that there wasn't going to be.a problem with the power transformer from the increased heater current draw compared to a KT88. Mark assurred me that the transformer was considerably overrated, and I suppose that it is a pretty huge lump of iron, and is totally cool to the touch at the moment.
I'd advise that anyone thinking of using them should check with the manufacturer or dealer before using them as they aren't quite a drop-in upgrade.
Apparently they will also be barely ticking over in my amp, so they will hopefully be long lived too, and be operating well within their most linear part of the curve.
The Black Adder
31-01-2012, 20:52
KT120's... sooon, it will be sooon!!! Oh yeah, changes on the way!!!
Rock and roll, guys - you're gonna love it! :D
Marco.
They arrived this morning... quite a bit taller than the Genelex KT88s. A quick visual inspection shows double getter flashes mid way up the envelope, a much larger plate structure, and that the grids have large cooling fins.
I'm just waiting for the amp to warm up so I can finish the bias adjustments, and then on to some listening tests.
Cheers,
Alex
http://farm8.staticflickr.com/7157/6811742429_abcc38b80f_b.jpg (http://www.flickr.com/photos/14548229@N07/6811742429/)
Tung sol KT120 (http://www.flickr.com/photos/14548229@N07/6811742429/) by alexmastersuk (http://www.flickr.com/people/14548229@N07/), on Flickr
I hope you'll bear with me on this as I'm not very knowledgeable on the electrical/electronics side of things. I blame my physics teacher for making it very dull, but that's another story.:(
The concensus seems to be a positive change in SQ when moving from KT88 to KT120 (looking forward to your impressions, Alex). What changes from a technical perspective? Greater output W? Increased damping factor?
My reason for asking is my EAR 890 uses KT90s (clues in the name, I guess :rolleyes:). Although there's still plenty of life left in them, KT120s could be an option on renewal (I'm assuming they're compatible). As Alex warns, I would check with TdP first, of course.
Chris
Bias stabilized after 10 mins, and has stayed bang on from then on. Currently
Running them at 40ma bias current, but may increase this later.
First impression is that the sound is clear and detailed through the mid and high frequencies, with very good instrumental seperation. It seems easy to hear into the mix to pick out individual lines, while still having good sense of the band playing together. Imaging is wide and deep, and nicely out of the box
Bass is less 'tubey' and resonant than with the genelex kt88, bass extension seems similar if not a bit better.
Only two hours on them so far, so just my first impressions. I expect them to improve through the burn in phase.
Regards,
Alex
The sound is opening up nicely, and the mid and upper bass seems to be quite a lot more transparent. The texture of guitars seems more brightly lit, making the previous Genelex KT88s sound a little opaque by comparison. As before, stereo width, height and depth seems to have taken quite a step forward. The image is now less in between the speakers, and stereo production effects seem more noticable. I was listening to Yello Stella last night, and the panning helicopter seemed to be doing orbits around the listening room.
Interestingly the difference between SPDIF and Toslink outputs is now very noticeable, and I am actually prefering Toslink for the first time. Mids in particular seem more transparent, with instruments more distinct in the mix and low level detail to be easier to discern clearly.
Bass quality, if not weight, has improved quite a bit. Double bass from Brian Bromberg on 'Wood' is definately more clear and authentically wood-like. There seems to be less woof and muddle colouring the sound. At first it did sound a little less rich, but now I've adjusted to it and prefer this presentation. It is a little drier, but definately more accurate.
For £119 per quad I'm very pleased and this is definately the best the best sound I have heard from my Stereo 90.
Regards,
Alex
Dominic Harper
04-02-2012, 13:05
Dom is looking at getting some of these for his monoblocks, but as each monoblock takes 4 tubes each, we need 8 so not the cheapest. He will just have to keep saving for a while. It will be interesting to know your views on them after you have had them for sometime.
Natalie;);)
Dominic,
I don't think you will do better for £240 for eight power valves. Aahh just noticed you've posted as Nathalie - explains why this requires an indefinte period of saving ;)
If you're using them in a circuit for KT-88s they should last a very long time also as they're just ticking over.
Alex
Natalie, when I get my spare set, I'll have eight in total and so will bring them round for Dom to try before he buys. Mine have also been cryo-treated :)
Alex, nice one, mate. It's a no-brainer, isn't it? What you're hearing is exactly what I heard in my own system, when comparing the 120s to 88s, which just sound small, weedy and a bit dull, in comparison.
Quite simply, if KT120s work properly in you amp(s), as seems to be the case with you, there's no going back! Enjoy :cool:
Marco.
anthonyTD
04-02-2012, 13:50
Hi all,
The KT120 is indeed a very good replacement for a lot of power amps using either KT88 or 6550, however, I must stress that it is not identical in electrical parameters i.e.; they will take a little more current from conventional AC heater supplies [average is around 100ma once valve has settled] which for high quality well made equipment, is not a problem, yes, you may find that the mains transformer will run a little warmer etc.
Also, the bias supply usually will need careful adjustment to exactly match the same steady state current as a KT88, however, with the KT120 having a considerably higher anode/plate dissipation of 60 watts compared to even the highest available KT88 [Svetlana winged c] of 42 watts it can be clearly seen that the KT120 when run as a direct replacement for KT88 and 6550 it will have seemingly a much easier life.
Bearing the potential higher power dissipation in mind, some amplifiers [mainly grid biased] can indeed be tweaked to produce even more power without getting anywhere near the maximum plate dissipation of the KT120.
however if you have a [conventional] cathode biased amplifier, care must be taken to make sure that the bias resistor values and wattage fitted for KT88 do not allow the KT120's to draw excessive current which could indeed lead to premature failure of the valve and equipment. On a positive note then, excellent results can be achieved using the new KT120 valve, but certain tests and precautions should be adhered to before doing the swap over, if your not sure then either consult your equipments manufacturer or a qualified technician for advice.
On a final note, the KT120 is a relatively new valve in terms of the regulars that have been around now for well over half a century i.e.; KT66, 6L6, EL34, KT88 etc, so,only time will tell if there are any serious negatives to using them, but from tests I have carried out in numerous equipment over the time I have been involved with this valve I can confirm that it favours positively with me, I just hope that its quality and relatively good longevity continues throughout its production as is often not the case.
Regards, Anthony, TD...
Yes, and as Anthony is too shy to say :eyebrows: he has the Tung Sol KT120s in stock, and will be able to sell you a professionally tested (for shorts, etc) matched quad or pair. The valves he buys are all hand-selected from his supplier, and so after being tested, fully guaranteed!
So folks, if you would like some really nice KT120s, contact Anthony on: 01443 814738.
http://www.tubedistinctions.co.uk/main.htm
:)
Marco.
Anthony,
I have noticed that in my amp the bias current on one valve is hard to adjust down to 40ma (Rogue's recommendation). Maybe that pot is out of range, or maybe it is just some variation valve to valve. If I set them during the day, bias seems to drop in the evening. I assume the there must be some variation in the supply voltage, and getting them down to 42ma is the limit of adjustment on the trim pot for that valve.
What effect if any will running them at, say, 45-50ma have across the quad?. Does power rise with bias?.
Shame you're not a bit closer to me or I'd be intereste in you seeing what you could do with it to optimise around the KT 120 (oooh an some mods at the same time!).
Regards,
Alex
anthonyTD
06-02-2012, 15:55
Anthony,
I have noticed that in my amp the bias current on one valve is hard to adjust down to 40ma (Rogue's recommendation). Maybe that pot is out of range, or maybe it is just some variation valve to valve. If I set them during the day, bias seems to drop in the evening. I assume the there must be some variation in the supply voltage, and getting them down to 42ma is the limit of adjustment on the trim pot for that valve.
What effect if any will running them at, say, 45-50ma have across the quad?. Does power rise with bias?.
Shame you're not a bit closer to me or I'd be intereste in you seeing what you could do with it to optimise around the KT 120 (oooh an some mods at the same time!).
Regards,
Alex
hi Alex,
only just read this, OK,Some valves will creep a bit untill they have fully stabilised, a lot will depend on how long they were subjected to burn in at the factory, or where they were finaly matched into sets etc.
As for running them slightly higher current wise, well, as i have already hinted, if the equipment has a decent amount of over margin designed in then to a sensible point i cant see any issues, however, how far you can go will depend on the individual equipment itself, some amplifier transformers have quite a lot of reserve built in, some are already running on close to max, again, it will be mostly down to the manufacturers to advise on safe parameters for their equipment, in my honest opinion, i cannot see any harm in running a valve over in the region of between 5 to 10 ma per valve, most power amp transformers should be able to cope with that, anymore and your running into unknown territory.
Hope this helps, I would continue to monitor that one paticular valve for now, also, try swapping it to another position in the amp and see if you can get it to a more acceptable steady state, if you do find that no matter which valve you put in that paticular position, you cannot get it to stabilise then it could mean that you have an issue with the amp.
Let us know how you get on.:)
Anthony,TD...
Thanks Anthony,
I will try moving that valve to another socket and see if it has more bias adjustment on the trimmer.
Regards,
Alex
Only just picked up on this post - dropped my S4s over to Glenn on Wednesday for an overhaul/ recap he suggested I might see if it would run the KT120's - I ordered a quad of Tung Sol KT120's from Watford Valves - update from Glenn is that thy are running fine in the S4s (built 1987) with no heat/voltage issues :)
I'm also getting the 25R upgraded to RS spec so when the beast comes back home it should be pretty special
:cool:
Steve
The RS is a fab preamp, but watch out for transformer noises - the one I heard and fell in loved with buzzed like a chainsaw :lol: It's not immediately "better" than a stock 25 and superficially sounds the same, as it should. I just found it that little bit easier to hear into the music mix, even with less than top rank sources and once heard, never forgotten sadly, unless you can buy one......
Interesting about the KT120 in the Series 4S. I always found this amp a but warm-n-woolly (hifi dave will now do a DSJR on me :)), hence my buying an OTL at the time (should have got Glenn to fit regulators into this one), but if the Kt120's work properly in this, the sound may well be transformed for the better.
The RS is a fab preamp, but watch out for transformer noises - the one I heard and fell in loved with buzzed like a chainsaw :lol: It's not immediately "better" than a stock 25 and superficially sounds the same, as it should. I just found it that little bit easier to hear into the music mix, even with less than top rank sources and once heard, never forgotten sadly, unless you can buy one......
Interesting about the KT120 in the Series 4S. I always found this amp a but warm-n-woolly (hifi dave will now do a DSJR on me :)), hence my buying an OTL at the time (should have got Glenn to fit regulators into this one), but if the Kt120's work properly in this, the sound may well be transformed for the better.
I must admit I was a bit sceptical about the KT120's in such an old design - especially as Glenn tried out a set of NOS GE6550's I had kept as spares which pumped out a perfect 50watts - I was half expecting the KT120's not to work (Glenn was none to sure and I suspect I was a willing Guinea Pig:eyebrows:)
I'll definitely watch out for the hum because my current 25R and the 4s hum and I was rather hoping the 2 box preamp would reduce it:doh:
Steve
Buzz my dear chap, not hum :lol: The great thing is that the supply box can be put as far away as possible from the preamp and this will have a positive effect on the phono stage in any case I reckon :) You'll be so into the music played through it though, that you'll forget everything else very quickly, I promise you :)
You'll be so into the music played through it though, that you'll forget everything else very quickly, I promise you :)
That's the plan Dave :thumbsup:
Steve
hifi_dave
02-11-2012, 22:41
http://http://i1058.photobucket.com/albums/t406/hifi_dave/041.jpg
KT 120s.
No surprise that KT120's work in the IA - I think it's pretty amazing that my 1987 S4s designed for 6550a's can handle them though - surely a testimony to Glenn's design and build quality
I'll post photies of the 25RS/S4s when I get them back - i think they look the muts nuts :cool:
Steve
KT120s (if your amp can take them safely) are a no-brainer upgrade on KT88s in every conceivable way. Basically, they make KT88s sound broken - even the best NOS ones, such as those from GEC. I've done the comparison many times - and they do it at a fraction of the price of the latter.
However, if you *really* want to hear what KT-120s are capable of, order them from suppliers who offer GENUINE cryo-treatment. I use Upscale Audio, in the States. Trust me, the cryo-treated variety are in another league again!! :eek:
Marco.
Have a look at the tube testing (and matching) procedure at Upscale Audio - it really is second to none:
https://www.upscaleaudio.com/pages/Testing-Power-Tubes.html
:eek:
That's why I always use them for my KT120s. As a perfectionist, I admire their attention to detail :)
Marco.
Marco
Glenn uprated my S4s with KT120's last week at the same time as converting my 25R to RS :)
I sourced a matched quad of TungSol KT120's from Watford Valves for a very reasonable £104 + vat - delivered direct to Glenn within 48 hours of ordering.
I'm very pleased with the new amp - hard to know what each bit is contributing. Anyway, the point of the post is that even £104 + vat for a quad of TungSol KT120's is great value for money. :cool:
Steve
Absolutely, Steve. Glad that you're enjoying your amp now more than ever :)
Marco.
Glad that you're enjoying your amp now more than ever :)
Marco.
Thanks Marco
It really is very good :yay:
Steve
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