Can KT88's be used in my amp?

[daz]

It's a JCM type homebrew. Output is about the same aside from a few tweaks. EL34's, 3.6k OT, fixed bias, NFB. Any reason i can't? I've used 6550's in it before and aren't 88's a version of those?

[pdf64]

I don't see why not; the bias voltage will need to be 10 to 20V higher than with EL34 but the same applies to 6550.
Pete

[daz]

Thanks. Just wanted to see if there was anything different about them, pinout or whatever.

[defaced]

Tube spacing can sometimes be problematic. Many KT-88s have a larger diameter glass envelope than some 6550s. And no, there is no lineage between the 6550 and the KT-88. While often times interchangeable, they are different tubes which were initially designed for different applications.

[daz]

Tube spacing can sometimes be problematic. Many KT-88s have a larger diameter glass envelope than some 6550s. And no, there is no lineage between the 6550 and the KT-88. While often times interchangeable, they are different tubes which were initially designed for different applications.

yeah, they're big but they fit no problem. The sockets are spaced well apart. I tried to use them last nite but i forget to add resistance to my bias circuit and turn the bias pots (2 pots, dual bias) all the way down. So when when i flipped the standby a tube sparked and the fuse went. I don't know if that was from huge over current or one was bad, but it was a free quad so i'll set the one that sparked aside and give em another try soon and this time no homer simpson stuff.

By the way, what do KT88's generally sound like? I think i read like a 6550, but then i think i read that in the same place that said they are like a beefier 6550, so apparently not good info from what you said about "no lineage".

[Chuck H]

I've never used KT88's. They're not touted for clipped tones like the classic EL34 and 6L6 big bottles. But that doesn't mean they won't work for you. They've worked for others. I've been surprised a few times by tubes that others said sounded just alright. Finding that proper bias and drive voltage made them killers. I think the lack of ability within the general guitar amp community to actually tune a circuit for a specific tube is largely responsible for the el34/6L6 pigeon hole. People who KNEW how to use tubes designed amps with these because they were cheap. But the designers knew how to get the most out of them. Most power tubes can be made to sound/clip good for a guitar amp. It's just a matter of dialing it in.

[defaced]

KT-88 is my favorite tube because they give a big clean sound. Overall to my ears they sound more balanced than 6L6/EL34, meaning, more even frequency response over the whole audio spectrum. They also sound like they reproduce more of the audio spectrum better, but I'd be real hesitant to say that without some data. In the amps I play, I rely on the preamp for all distortion and the power amp for being clean/providing the "feel" of the OT/speaker interaction. Since I don't use power tube distortion as part of my tone, I'm not sure how useful this description is to you, but that's sorta what they sound like to me.

[Alf]

And what brand are they ? JJ ?

[daz]

I tried them and thy're ok, but i prefer the el34's, winged C in particular. I have to think that because i've spent years perfecting this amp's tone down to the most tiny yet hearable detail, having done so with winged C's in it the map has been designed to sound best with those tubes. Nothing i try seems as good. The 88's were nice and like 6550's they are clean and articulate and i DO like them. Probably better than 6550's which sound the same but not quite as good. But putting the el34 C's back is like coming home. It's just THE sound for me. If not for wearing out the sockets i would however like to add a switch so i could bias both and make it switchable from one to the other without having to rebias every time. I did that with a JCM800 once so i could quickly A/B 6550's and el34s and it made me realize theres just a smooth complex midrange i love about el34's that other tubes like 6550's don't have. The ones i use i have no idea what country of origin they are, but they are labeled by TAD which is just a reseller. But they look nice with chrome bases and look well made. I got a free used quad, but 2 were bad. On didn't light up and the other blew a fuse leaving me with one good pair.

[Alf]

but i prefer the el34's, winged C in particular. I have to think that because i've spent years perfecting this amp's tone down to the most tiny yet hearable detail, having done so with winged C's in it the map has been designed to sound best with those tubes. Nothing i try seems as good.

Recently I heard that they have quit production of these tubes so if this is really true I would advise you to stock up .
It's a pity that these really good sounding are going to disappear from the market.

Anybody here who knows more about his ?

Alf

[big_teee]

I tried them and thy're ok, but i prefer the el34's, winged C in particular. I have to think that because i've spent years perfecting this amp's tone down to the most tiny yet hearable detail, having done so with winged C's in it the map has been designed to sound best with those tubes. Nothing i try seems as good. The 88's were nice and like 6550's they are clean and articulate and i DO like them. Probably better than 6550's which sound the same but not quite as good. But putting the el34 C's back is like coming home. It's just THE sound for me. If not for wearing out the sockets i would however like to add a switch so i could bias both and make it switchable from one to the other without having to rebias every time. I did that with a JCM800 once so i could quickly A/B 6550's and el34s and it made me realize theres just a smooth complex midrange i love about el34's that other tubes like 6550's don't have. The ones i use i have no idea what country of origin they are, but they are labeled by TAD which is just a reseller. But they look nice with chrome bases and look well made. I got a free used quad, but 2 were bad. On didn't light up and the other blew a fuse leaving me with one good pair.

Hey Daz:
What did you have to do to run the KT88s, and what bias current did you run on a 50w amp?
T

[daz]

Hey Daz:
What did you have to do to run the KT88s, and what bias current did you run on a 50w amp?
T

About 50 ma per tube which i derived with weber's calc.

[big_teee]

About 50 ma per tube which i derived with weber's calc.

You had No trouble blowing the B+ 1/2 amp fuse?
I have my version of the JCM800 2204, with both MVs, I currently run the E34Ls.
Was wondering what the KT88s would do, and sound like but a pretty expensive wondering at $80 a pair for the JJs.
T

[daz]

You had No trouble blowing the B+ 1/2 amp fuse?
I have my version of the JCM800 2204, with both MVs, I currently run the E34Ls.
Was wondering what the KT88s would do, and sound like but a pretty expensive wondering at $80 a pair for the JJs.
T

No, they ran fine. I suppose you have to see whether your PT can handle the load, but i just figured mine has used 6550's before and i assumed at these would be about the same.