Yes, I've spotted it too. For fixed bias, the spec suggests 51K grid leak at the spec voltages shown. The 29pF input capacitance requires a current dump for best performance. Both are nasty. For lowest distortion, only the best low Z driver stages can deal with them. For autobias, it's another picture. Does ones design warrrant such a beast ? Maybe New Sensors experience with the EH KT90 (I get excellent results with this in UL 40%, better performance than any 88's) have now come up with the trump meister.
richy
richy
NOT plug in for KT88/6550. Heater current draw is greater and the tube biases very differently. The 51 KOhm grid to ground max. will make for big trouble in most amps that employ "fixed" bias.
I do not know about you guys, but I see this as a white elephant!
Lots of chatter over on the guitar amp forums as well, but think about it really.
Who would design an amp around a single source tube given the spotty reputations ALL current production tube manufactures have.
Now if SED, JJ and New Sensor and maybe others were all making the same tube it might not be a bad idea, but single source? Not likely.
Lots of chatter over on the guitar amp forums as well, but think about it really.
Who would design an amp around a single source tube given the spotty reputations ALL current production tube manufactures have.
Now if SED, JJ and New Sensor and maybe others were all making the same tube it might not be a bad idea, but single source? Not likely.
This is probably the most reliable single source currently extant for tube manufacture. (Tightly run and well managed) Should there be sufficient demand someone else will probably clone it.
I can guarantee that if no one buys it because it is single source there will be no incentive for anyone to introduce anything new. Remember when the EI KT-90 was single source, that vendor is now gone, and guess who makes it now? A lot of you guys are using the original and the EH clone.. (The same parent company and plant as is making the KT-120. hmmm...)
The people who will probably buy it are those who have always purchased the currently available production: companies like Conrad Johnson, ARC, Quick Silver, Manley, and VTL who currently manufacture big PP tube amps. Throw in a few guitar amplifier manufacturers and you get the picture. These guys aren't buying NOS tubes from some secret stash somewhere. I imagine the appeal will be even higher power PP amps with lower tube counts keeping manufacturing costs down.
I plan to purchase a few for use in a high voltage, high current series pass regulator.
(pentode connected) For my application it looks ideal and I will purchase enough of them to meet my needs for some time. (Not too many)
Given that every tube made today - even the EL34 suffers from some level of inconsistency of performance with some vendors clearly making better sounding/more reliable versions than others one could almost argue that a lot of these tubes are effectively single source if you happen to have a particular favorite.
Almost none of my favorites are currently made - so I have stock piled a sufficient quantity to keep me going indefinitely. With a little planning, some luck, and a reasonable budget it is possible to do that with any type that has not yet achieved cult status.
What I am saying is if the tube interests you buy a few, and perhaps more interesting types will subsequently follow.
Expo-Pul, New Sensor's Russian plant probably makes more tubes than anyone else and is responsible for the following brands: Sovtek, EH, Mullard (reissues), Tungsol, Svetlana from the old SED joint venture (Not to be confused with the now separate Svetlana SPB) and probably a few I have missed. IIRC Over 800 employees working in this plant have got to make it just about the largest remaining tube manufacturing operation.
Nay saying is so fashionable these days..
I can guarantee that if no one buys it because it is single source there will be no incentive for anyone to introduce anything new. Remember when the EI KT-90 was single source, that vendor is now gone, and guess who makes it now? A lot of you guys are using the original and the EH clone.. (The same parent company and plant as is making the KT-120. hmmm...)
The people who will probably buy it are those who have always purchased the currently available production: companies like Conrad Johnson, ARC, Quick Silver, Manley, and VTL who currently manufacture big PP tube amps. Throw in a few guitar amplifier manufacturers and you get the picture. These guys aren't buying NOS tubes from some secret stash somewhere. I imagine the appeal will be even higher power PP amps with lower tube counts keeping manufacturing costs down.
I plan to purchase a few for use in a high voltage, high current series pass regulator.
(pentode connected) For my application it looks ideal and I will purchase enough of them to meet my needs for some time. (Not too many)
Given that every tube made today - even the EL34 suffers from some level of inconsistency of performance with some vendors clearly making better sounding/more reliable versions than others one could almost argue that a lot of these tubes are effectively single source if you happen to have a particular favorite.
Almost none of my favorites are currently made - so I have stock piled a sufficient quantity to keep me going indefinitely. With a little planning, some luck, and a reasonable budget it is possible to do that with any type that has not yet achieved cult status.
What I am saying is if the tube interests you buy a few, and perhaps more interesting types will subsequently follow.
Expo-Pul, New Sensor's Russian plant probably makes more tubes than anyone else and is responsible for the following brands: Sovtek, EH, Mullard (reissues), Tungsol, Svetlana from the old SED joint venture (Not to be confused with the now separate Svetlana SPB) and probably a few I have missed. IIRC Over 800 employees working in this plant have got to make it just about the largest remaining tube manufacturing operation.
Nay saying is so fashionable these days..
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Kevin,
Properly made EI KT90s are a joy. The EH version, with its flat sound stage, is a disappointment.
FWIW, I'd rather that New Sensor restarted production of 7199s and 12BY7s, types for which a clear need exits, instead of introducing a power O/P type of dubious merit. NS has already done well by resuming 12AY7 and EF86 production. I wish they would do more, along those lines.
With a few circuit tweaks, maybe the KT120 can be useful in the Fender bass guitar amp that works well with GE 6550A "finals".
Properly made EI KT90s are a joy. The EH version, with its flat sound stage, is a disappointment.
FWIW, I'd rather that New Sensor restarted production of 7199s and 12BY7s, types for which a clear need exits, instead of introducing a power O/P type of dubious merit. NS has already done well by resuming 12AY7 and EF86 production. I wish they would do more, along those lines.
With a few circuit tweaks, maybe the KT120 can be useful in the Fender bass guitar amp that works well with GE 6550A "finals".
Kevin,
Properly made EI KT90s are a joy. The EH version, with its flat sound stage, is a disappointment.
FWIW, I'd rather that New Sensor restarted production of 7199s and 12BY7s, types for which a clear need exits, instead of introducing a power O/P type of dubious merit. NS has already done well by resuming 12AY7 and EF86 production. I wish they would do more, along those lines.
With a few circuit tweaks, maybe the KT120 can be useful in the Fender bass guitar amp that works well with GE 6550A "finals".
Hi Eli,
I remember the early exploding EI KT-90 rather well, and the later ones with serious linearity issues, and I remember some that performed quite gloriously in the modified Citation II's I was responsible for.. I haven't tried the EH KT-90 so I can't say anything about their merit or lack thereof..
I agree with your comments about the 7199 and 12BY7A - would definitely be worth their while to make good ones.
Are you sure that the KT-120 is not the result of demand for a higher power KT series tube, and that in fact someone did not ask for this tube? I guess we will have to wait and see where it appears first. Mike Matthews is nothing if not an astute business man...
I can see an immediate use for it in some power supplies I am designing for my next SE amplifier.. A KT-88 would be running at the limit of its dissipation in my application, the KT-120 gives me some margin.
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Agreed up till reliable, since that has not been my previous experience with new sensor tubes in general the past 3 years.
I have thrown away more bad tubes from them than from JJ or SED (new fresh from the box)
My out of the box bad percentage has been horrid enough that I rarely buy them now, so I do not know exactly how they are now.
I did throw away 6 more new 12AY7's last month, 6 out of 10 bad? PASS for now TYVM
12BY7A being revamped: can't visualise it although I love this tube. The g1 being so close to the cathode makes it a manufacturing challenge.
richy
I tend to stick to NOS for my own needs, but have had somewhat more trouble with JJ than New Sensor products, but I have not bought appreciable quantities in years. I also get matched and burned in power tubes when I buy them and have had no problems so far.. I'm running recent vintage EH KT88 in my power supplies without issues.
None of the current production is as good on the quality front as production back in the day.. Unfortunate that you cannot purchase tested graded small signal tubes from NS directly. Some resellers like Ruby do a great job weeding out the rejects - never bought a bad tube from them.
hey-Hey!!!,
I'll be in for a quad of them to run in my W6m's when they're available. It'll be nice to run at +100 mA/tube w/o exceeding the plate ratings of the finals. I do wonder how valid that g1 resistance value spec is. it would indeed be nice to tolerate more like 100k but I'll grid-choke the amps if need be( been wanting to do that anyway...
cheers,
Douglas
I'll be in for a quad of them to run in my W6m's when they're available. It'll be nice to run at +100 mA/tube w/o exceeding the plate ratings of the finals. I do wonder how valid that g1 resistance value spec is. it would indeed be nice to tolerate more like 100k but I'll grid-choke the amps if need be( been wanting to do that anyway...
cheers,
Douglas
At the very least, I am highly encouraged to see them introducing a *real* new tube, rather than all these reissues of the same bits they have always sold. With SED seemingly withering away, New Sensor and JJ seem to be the last of the Mohicans. I've always been hoping to see someone reissue the 8417, but its been so long now that I suspect any such amps still in service have long been modded for 6550s. 12BY7 is another big one, too.
I would rather have these. These tubes are being tested in SE. This picture is about 5 years old. The setup is a Tubelab SE board being used to test several different tube types. The power transformer behind the voltmeter is being used to run the board. The Knight power supply is running the output tubes alone. The analog current meter is measuring the plate current for both tubes (295 mA). The multimeter is reading the plate supply voltage (403). Note that I would have turned things up more if I had more power supply, but this was the biggest supply that I had at the time, and it was beyond maxed out. The output tubes were triode wired and dissipating 55 to 60 watts each. There is no redness anywhere despite operating above the plate dissipation spec, and the screen grid voltage spec.
The world needs at least one big real sweep tube at a realistic price. This one is a 6LW6. I have not seen another "receiving tube" that can be cranked like these. There are several different versions (I have 7 different constructions) that vary in their dissipation capability. The wimpiest will turn red at about 50 watts. The biggest go red at 95 to 100 watts!
The 12BY7 has been mentioned by a few people. These are still common at hamfests for reasonable prices. There are a few similar tubes that often work better than the 12BY7, but may not be a drop in in all circuits. 12GN7, 12HL7, 12HG7, 12DQ7
Attachments
KT120s arrived this morning
I have a set of hand made by myself Oddblock amps with KT 88 tubes. I put a SPDT toggle switch with two different value resistors on it so I can turn down the CCS and run 6L6 and KT77 tubes when I want to. Now I have my quad of KT120s to try out. I have enough heater current to run these tubes and have 450v B+ @250ma. These KT120s should run with no problem. Thanks, Robert P in Lilburn, GA
I have a set of hand made by myself Oddblock amps with KT 88 tubes. I put a SPDT toggle switch with two different value resistors on it so I can turn down the CCS and run 6L6 and KT77 tubes when I want to. Now I have my quad of KT120s to try out. I have enough heater current to run these tubes and have 450v B+ @250ma. These KT120s should run with no problem. Thanks, Robert P in Lilburn, GA
Check out this thread on www.diyaudioprojects.com, It may have some info that is useful.
Tung-Sol KT120 users and abusers • DIY Audio Projects Forum
Cheers
Brian
Tung-Sol KT120 users and abusers • DIY Audio Projects Forum
Cheers
Brian
I understand what you say about designing with a single source tube
But isnt that also the game when building amps with rare NOS tubes
Anyway
If you dont want new tubes, then there wont be any
But maybe making new tube designs is the better way in the future
Its been stated again and again that new reproduction of old tube design are far from the original
Obviously its not possible to make perfect replicas, and never will be
So maybe it really is about designing new tubes
Tubes that handle better in production
From what I understand the KT120 can do 20watt SE(UL)
without too much trouble
and still affordable
Sounds pretty ideal to me
But isnt that also the game when building amps with rare NOS tubes
Anyway
If you dont want new tubes, then there wont be any
But maybe making new tube designs is the better way in the future
Its been stated again and again that new reproduction of old tube design are far from the original
Obviously its not possible to make perfect replicas, and never will be
So maybe it really is about designing new tubes
Tubes that handle better in production
From what I understand the KT120 can do 20watt SE(UL)
without too much trouble
and still affordable
Sounds pretty ideal to me
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