RJ Guitars Rockster 66 latest info needed

[xtian]

After reading past posts, I'm wanting to build a Rockster. Can you, RJ, or anyone else point out the latest schematic?

Opinions on Edcor trannies? A step up from Hammond?

Has anyone installed a Hall VVR? (Is the Rockster fixed or cathode biased?)

Folks who built Rocksters in 2008 and 2009, please let me know what you think of them today! Thanks!

[Zippy]

Did you find the original thread of its development?

https://tubeamparchive.com/viewtopic.ph ... t=rockster

[xtian]

Did you find the original thread of its development?

https://tubeamparchive.com/viewtopic.ph ... t=rockster

Yes, I did. But the last post is almost a year ago, and I wanted to check if more bugs are worked out. Thanks!

[M Fowler]

I don't think there are any bugs with that amp or any of the ones we have been building. You can of course build it your own way, use what ever tubes you want and the type of caps you prefer on the tone board as well.

Cathode resistor/cap can be changed to suit as well or go fixed bias. The voltage chart is very useful for the various tubes rj used and I believe preferred the KT66.

He sells them as a kit on his website.

[Zippy]

Yes, I did. But the last post is almost a year ago, and I wanted to check if more bugs are worked out. Thanks!

It's a pretty bug-free and robust design. Not at all as sensitive to layout as the Express or Liverpool - not that I'd encourage one to make a sloppy build.

I remain a resolute endorser of the mid knob too.

Enjoy!

[RJ Guitars]

xtian,

I think we made contact via email - so thanks for looking me up.

For those that don't know, the Rockster is basically a Trainwreck Rocket (same as a VOX AC-30 top boost) minus the 4 EL-84's and add 2 KT-66's... or any other Octal of your choice.

For those in the know, this looks a lot like a Marshall JTM45 which looks alot like a 59' Bassman circuit. Most significant difference in the case of the Rockster is that it uses cathode biasing. Zippy sorted all that out and brought me a pair of KT-66's as the inspiration for this build.

I'll post the schematic here but I think it is the same as the one on the Rockster thread. Maybe after we have a hundred of them out there I'll remove that "Unverified Draft" note, but at this point it's pretty well proven itself.

I think it was Mark Fowler (can't remember clearly) that put together one with a pair of KT-88's. If you want to go the other way and dial the wattage down you could go with the V-2 Rocket which uses a pair of the subminiature 5902 output tubes.

Then if you want options and effects you can use the extra gain stage as a boost or add reverb.

The transformer selection for these varies pretty widely, especially the output trannies. I used an old Stancor on the build I posted, some have used the Edcor, and some used the Dynaco variant that Heyboer makes... good reports in all cases. I think Rawnster might have used a Pacific 6.6K on his build.

I do consider Edcor a step up from a Hammond although I don't know if anyone ever used a Hammond on this build to give us that data point. Edcor is generally a step up from everything cosmetically and good sonic results as well.

enjoy

rj

[M Fowler]

rj, that was Don I think that built the KT88 which I was looking at that schematic two nights ago thinking hmmmm I should build something like that.

Mark

[rawnster]

I've done with with kt66s, and another with kt77s/el34s. Both amps sound very cool. Just recently I added (with great results) a LarMar MV to the kt77 amp.

[M Fowler]

Two nights ago I switched the KT66 tubes out of my Root 666 build to the Rocket Reverb.

Last night I picked up some new KT66 tubes for that Rocket Reverb amp which sounds good with either the GTEL34M, EL34L, or KT66s.

I will leaved the KT66s in for a while to get my ears acustom to the change and see if I truely like that better.

Ron how do you like the KT77's I want to try those in my other Rocket Reverb I built in the Fender combo cabinet. Space is tight so KT66's are way too large to fit in there as the PT is close to the outer power tube.

[xtian]

I added (with great results) a LarMar MV to the kt77 amp.

Good! That's what I need. Can you point me at details for this?

[M Fowler]

I have been using the prime or watts control rather then MV with good results. I should try the LarMar though.

[rawnster]

I added (with great results) a LarMar MV to the kt77 amp.

Good! That's what I need. Can you point me at details for this?

Details? hmmm. Do a quick search for larmar on this site and you'll see a few threads. Also, see attached file.

Basically, all you need is:

1 - 250ka dual gang pot
2 - 2.2meg resistors
2ft of two-conductor shielded cable

[rawnster]

Mark, the kt77s sound very similar to el34s, yet with a bit more sheen and sonic footprint. In a 1x12 combo they simply offer more butt and bite for the buck.

Give'm a try; pretty cool tubes for sure.

[M Fowler]

Thanks Ron I will give them a try

[Bob S]

Thanks Guys ! I have a nice pair of KT66's that have been whispering Rocket to me. Decision Made !
The sickness continues ...