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5150 with KT88/6L6 mix


John Busbee

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The KT88's are pulling about 32mA ( the right bias meter ) where they should be pulling about 60mA. But, for you guys who are happy with the stock tone or just don't want to mod the amp then this Integrated quad with the JJ KT88's in the outside sockets and the JJ 6L6GC's in the inside sockets will get you even more low end thunder and a very fat and punchy all around tone. The only thing necessary to install these is to clip the rather useless tube retainers from the two outside sockets so the big bases on the KT88's will fit. ( Note the clipped retainer halves sitting on the amp.)

 

This Integrated quad runs 99.00 and is plug and play, I repeat PLUG AND PLAY!!

 

5150-KT88-6L6.jpg

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From a old thread...JerryP's tip to be safe with this tube set.

 

"You'll have to have the screen grid resistors changed and the bias circuit modified to use the KT88's. I do those mods. To be honest I don't think it's worth it. I have tried 6L6's, EL34's, 6550's and 6V6's in the 5150 and to my ears the 6L6 works best. The EL34 is too crunchy and with the huge gain the 5150 preamp has the EL34's sound like pure mud. The 6550's break up a little more than the 6L6 and aren't as tight and clear as the 6L6. The 6V6 isn't bad, but the 6L6's sounded best for a tight, clear, defined tone. KT88's are very similar to 6550's.

Upgrading the output transformer gives the amp a more defined and clear balanced tone. It gives you a more responsive tighter feeling amp.

Jerry"

 

http://acapella.harmony-central.com/archive/index.php/t-1312768.html

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also...read this...

 

have not tried that myself (I use four JJs in mine), but here is Peavey's Roger Crimm's take on "integrated quads":

 

Integrated Quad

 

Sorry, but this has to be one of the wackiest ideas I have ever seen. I know there are a lot of guys who are doing this, and there is at least one tube supplier who seems to think this is a good idea. I tried to stay silent on this one, after all it's your money.

 

The theory here is that they pick a set of EL34 and a set of 6L6, which draw the same exact amount of natural plate current. The danger here is in the implied assumption that plate current is the only spec that matters, and that the tubes will not drift from these specs as they age.

Two other real differences you have to deal with is available heater current (the EL34 draws twice the current, 1.5 amps as opposed to .9 amps for the 6L6), and that 6L6s and EL34s have different reflected plate impedances. Not taking specs like these into account might get you into real trouble with some amplifiers.

 

This sounds like a good way to move some tubes which you otherwise couldn

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also...read this...

 

have not tried that myself (I use four JJs in mine), but here is Peavey's Roger Crimm's take on "integrated quads":

 

Integrated Quad

 

Sorry, but this has to be one of the wackiest ideas I have ever seen. I know there are a lot of guys who are doing this, and there is at least one tube supplier who seems to think this is a good idea. I tried to stay silent on this one, after all it's your money.

 

The theory here is that they pick a set of EL34 and a set of 6L6, which draw the same exact amount of natural plate current. The danger here is in the implied assumption that plate current is the only spec that matters, and that the tubes will not drift from these specs as they age.

Two other real differences you have to deal with is available heater current (the EL34 draws twice the current, 1.5 amps as opposed to .9 amps for the 6L6), and that 6L6s and EL34s have different reflected plate impedances. Not taking specs like these into account might get you into real trouble with some amplifiers.

 

This sounds like a good way to move some tubes which you otherwise couldn

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left message :poke:

 

content of message:

 

KT88s draw roughly twice the heater current of 6L6s. i don't know what the stock PT is rated for, but i'd be very hesitant to keep those tubes in there without a new PT or a filament transformer to run the heaters.

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left message :poke:


content of message:


KT88s draw roughly twice the heater current of 6L6s. i don't know what the stock PT is rated for, but i'd be very hesitant to keep those tubes in there without a new PT or a filament transformer to run the heaters.

 

 

^ what he said

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there's other issues, as well. the grid to bias resistors need to be different for KT88s than 6L6s, and the info about impedances is also relevant.

 

i think this whole thing really goes back to mesa and the whole simul-class deal. it's a cool idea and all, but the juice ain't worth the squeeze if you're trying to make an amp that wasn't designed for "integrated quads" use them.

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maybe...I think they are too similar. Legacy combo and 5150 half stack more likely.

 

I think the Bogner would cover a lot of the lower mids and the Peavey 5150 would cut a bit better and cover the upper mid range...but it all depends on how you dial it in.

 

Either way...it will be a great set up. :thu:

 

5150 and V30's are great together too. With your bogner cabinet paired with it I imagine it will sound awesome.

 

I just got a mode four cab two days ago with Celestion g12k100's...pretty kickass

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I think the Bogner would cover a lot of the lower mids and the Peavey 5150 would cut a bit better and cover the upper mid range...but it all depends on how you dial it in.


Either way...it will be a great set up.
:thu:

5150 and V30's are great together too. With your bogner cabinet paired with it I imagine it will sound awesome.


I just got a mode four cab two days ago with Celestion g12k100's...pretty kickass

 

Yeah, it would be awesome for sure...hell, my old guitar player ran an Uber and a Triple Rec together and it was awesome.

 

Mode 4 is a good cab, too. You back at USC?

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Yeah, it would be awesome for sure...hell, my old guitar player ran an Uber and a Triple Rec together and it was awesome.


Mode 4 is a good cab, too. You back at USC?

 

i am in texas at the moment. i go to southern methodist university...and for what it is worth i am a tiger fan anyways...

 

it sucks having to keep all your gear in texas since i am here the majority of the year (9 out of 12 months).

 

dont worry though...we will have a bigger and better ampfest this summer. :thu:

 

the two channel triple that i have is extremely similar to scott's minus the voodoo mod he had that added more punch and clarity. maybe it can make its way to carolina to the ampfest...well see.

 

i might not even have it anymore by the time summer comes around with all my gear whoring lately.

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  • 4 years later...
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Hey everyone on this very cool website my name is Jonny Rabbitt and im new to this forum. Today is Dec 19,2014 for the record. I want to comment on all the things going back and forth about using kt88's and 6l6's in a 5150 head. Once and for all im gonna clear up all the facts written that are 100% wrong. First the 5150 is a fixed bias amp from the factory. Bias cant be adjusted without a modification therefore if you want to change the power tubes, as long as they are matched any quad of 6l6's are plug and play. Now to the real juicy stuff lol... You can put a pair of kt88's in the outside sockets just remember to remove the retaining clips so they will fit and 6l6's in the two inside sockets. The kt88 tubes drawing a lot more current will automatically bring the bias up a bit. I've had this setup in my 5150 for seven years and gigged and practiced with it without issue. It sounds amazing. Way more bottom end, notes are very articulate and not mushed together, warm beautiful tone, the eq is also much much more usable. The kt88 tubes can also be replaced with kt 66 tubes for a little more of the British tone and a bit more miss. I've retubed my head five times using this setup and again never one problem. I use jj tubes all around and it sounds better than any amp out there in my opinion. Call eurotubes and bob can set you up with the different options he has. In closing this setup is plug and play and trust me your 5150 will sound better than you dreamed of. Exact tones of the balance record which I think is killer guitar tone. To all the guys out there that say this cant be done, I've been doing it in all three of my 5150 heads since 2007 when I heard about it. Bought all three heads new in 1997. Also this can only be done in the first line of 5150's. Not the 5150II or comb. I hope this helped clear up any people on the fence about doing this. Do it!!!!!! It will blow you away how good that head can sound! Thanks and good luck folks

 

 

 

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