Kt66 considered for retube

[Guitarist]

I just did a lot of reading of KT type tubes. I have a pair of KT88s in a Lee Jackson Ampeg and it sounds way better that the original el34s. Yesterday I just bought a near-new Carvin TS 100 all tube rack poweramp. The output transformers aren't that big but it has bias switches for 34s or 6L6s but I am leaning towards these KT66s for use with pedals but mainly to match with my Digitech GSP1101 modeller.

Just wanted your thoughts on this; I'm after FULL low end and tone throughout. So far, the Carvin sounds excellent but it could be better...

Anyone else have one of these? Because I can see a few things inside that are about to get modded. I don't like 220K plate resistors for one. I wrapped the preamp to/fro ribbon cable in alum. tape- now it's quieter. I'm not sure what the design is so a schematic would be nice. I am thinking of some different tube types. If I put in 12at7s for the PI, a plate resistor of 47K is best right? [Interesting how VHT says that their 12AT7 PI tube is NOT interchangeable] I wanted a VHT poweramp (again) but this Carvin looks to be a good choice!

thanks,

[Richard]

Double check that the tubes will fit. The tubes in mine seem mighty close together and close to the rear wall of the enclosure. Are you planning on replacing the circuit boards or are you going to mod the existing board?

[Guitarist]

They won't fit as th 66s need 2 1/4" between centers. Only 6L6 or 77s (thanks Eurotube guy) will fit. The Gt el34s are brand new in it with only 15 hrs run time he said. If I were to take the board out It could get messy
Maybe more filtering. Do have any idea if there are any CFers and if the PI is like the Legacy? It's hard to tell with the dbl sided boards. Two stages of preamp gain would be too much.
'pretty happy with it! I put two TungSol 12ax7s in the first stages; better...

[Amp Kat]

Two KT-88's should work nice but even if the 4- 88's did fit it is possible it would eventually burn up the OT. Are you using the Digitech in the front or the return. If your going in the return which is where it will sound much better then you are bypassing the preamp and not using the 220k plate resistors anyway. If your going into the front you will increase your signal to noise ratio 10 fold and it will get much looser especially with that gain control pot cranked mixed with the GSP gain could even push heavily into overdriving the grids very heavily causing oscillations and screaching if either is cranked to hard. Doesn't the GSP have some serious EQ's in the parameters ? My GSP 2101 has EQ out the YZU and you can dial a serious low frequency voicing with it and the other parameters of the DSP.

[Guitarist]

The tone recipe continues; Amp Kat, you are 100% correct with those findings. The newer gsp1101 has tried to deal with this its effects loop. I am going straight in and it will be fine. I found four kt77s used for $40 with I give a spin.

Anyone have schematic? I think those 220K are in parallel for some reason so hopefully V1 and V2 are cathode followers...