Before I buy KT88's

[pforeman]

Before I buy some KT88's for my simple se.
Could someone enlighten me as to weather they sound good without negative feedback/ultralinear.
My simple se loves EL34's.
Thanks,
Paul

[LinuksGuru]

Its question of amplifier circuit, parts used, and taste. BTW, KT88 is not a direct plug-and-play replacement of EL34, it may work fine or may not, depending on driver tube.

[Gorgomat]

It may even toast your transformers.

[SGregory]

pforeman,
why don't you post what you have as far as PT and OPT's. The Simple SE should work fine with the 12at7 driver. The KT88 or EL34 will work in the Simple SE with a couple of resistor changes.

As far as the sound? I am very pleased with the KT-88, very listenable and enjoyable in this circuit. I would be interested to here your comments comparing the two. I think it becomes more of a personal preference based on what you like and the type of speakers you have.

[pforeman]

Hi, Thanks for your responses.
Yes I know it will work as mine is the fourth of 4 that I built, and I did listen somewhat to my brothers/friends before I gave them out. For all of the other three, I purchased KT88,6550 EL34,KT77, 6L6GC and 6CA7's.
I listened to all of them slightly, but was mainly checking voltages, and looking for plate glow.
I built mine without a cathode f.b. switch, or ultralinear.
Just straight triode. It does have a six position cathode resistor network starting at 1Kohm and going to 450 kohm.
I have my speaker wires going right to the tabs on the Edcor GXSE 15-8-5k output transformers
Powered by Edcor XPWR035 (370-0-370 ;200 mA)
Plate voltage is about 460 volts, I get plate glow with EL34's unless I'm on the 1Kohm bias setting.
All I ever see about KT88's is when connected in ultralinear
(even the tube data sheets seem to skip right to ultralinear ) and that the kt88 in ultralinear works best with cfb.
I was just wondering if many people prefer the sound of their KT88's in Triode, and what brand they use if'n they do.
Thanks,
Paul

[pforeman]

Whoops going from 1 kohm to 450 ohms

[tubelab.com]

Before I buy some KT88's for my simple se. Could someone enlighten me as to weather they sound good without negative feedback/ultralinear. My simple se loves EL34's.

I regularly switch between the EL34 and the KT88. The EL34 shows the most detail, while the KT88 is more authoritative. I find that both tubes sound fine in triode, but both seem to prefer CFB when used in UL mode. Of course this depends on your speakers, the type of music you listen to, and how loud you play it. On my little Yamaha speakers the EL34 in triode works for most music (the amp used there doesn't have a UL tap). KT88's are used for louder music. No feedback is used in either case.

My big Open Baffle (Silver Iris) speakers work well with the EL34 in triode, but when I want to shake the house with some techno, or Pink Floyd, the KT88 in UL with CFB is exactly the right tool for the job. Bumping up the current a bit (500 ohm total cathode resistor) helps improve the damping factor a bit more too.

I don't use expensive tubes, so I have no experience with them, but of the reasonably priced KT88's the Electro Harmonix version seems to handle the higher current the best and cranks out the biggest most accurate bass (again speaker and OPT dependent).

[SGregory]

I have both the GEC and EH kt88 (current production) The GEC is cleaner with less haze in the higher frequecies. I have identical trannies. My preference is triode. The UL is too zingy(is that a word) or "on edge". I listen with and without CFB, but prefer the CFB for all but vocals as it has more control for my speakers.

I have not tried my GEC's in UL mode yet.

I hope that helps.

Sounds like you have a very nice set-up


UL definatley will rock better!