66 Rockster Build

[M Fowler]

bluesbreaker62,

I would not wrap the wires around the sockets like that shorten them up noise will be minimal. My 2 cents. Looking like a nice amp so far, can't wait to hear what you think of the amp.

Mark

[fishy]

For those that have built the Rockster and the Rocket, what are the differences in terms of tone.

Ange

From my experience the octals are fatter and really need more to get them singing. Bypassing the 2nd stage will do this for you.

I have a project amp that uses either 2 octals or 2 el84s, variable bias setup. No wish to derail the thread here, I intend to post more on it when I get there. Clips will follow whne that time arrives.

[M Fowler]

Yeah fishy you need to start a thread on that amp for us to read about

Mark

[RJ Guitars]

Robert,

My apologies for the late jump in on this thread... but then again you have gotten some great help and are doing fine without me! I've been on an overseas assignment that distracted me from the real fun in life (building amps). Anyway I missed this thread until this evening... you are on your way through a very nice looking build!

The KT-66 Rocket or as I call it "The Rockster" was inspired by my evaluation of the things Ken Fischer had done and a few other places I thought he might have experimented had his health been up to it. What I found was that the KT-66 tubes sounded very similar to the EL-84 tubes but add just a little bit more of everything - high end - low end - volume.

It seems that every amp that KF built he used a power transformer that provided a lower B+ voltage than Fender or Marshall would typically use so I intentionally starved these a bit to follow suit. If you buy into the VVR concept that lowering the voltage doesn't drastically change the sound, then the 245 volt tranny makes sense and gives you a world of options for tubes that will work in it. Also, this preserves the voltages in the preamp tubes and I believe that KF had these dialed in pretty well in the Rocket.

Even though I built it using KT-66's, I've got great sounds out of it with EL34's and 5881's. One other great iteration is the way that Fishy made his so that it could use either KT-66's or EL84's... very cool!

In the end, I was a little bit surprised how good these amps sounded without much tweaking required. Curiously, at some point Zippy pointed out to me that I had basically recreated the 59' Bassman. Looking at the schematics, he's got something there. Now if you take Allyn's comment about the JTM amp and consider that it was based off the 59' Bassman, he's also got something there. The big difference here is that I used a cathode biased configuration in addition to the lower B+.

Lastly, Fishy's mention of the cathode bypass cap on the 2nd stage is significant. On a traditional Rocket circuit, this doesn't really do much for me but in the Rockster its like the steroid overdose switch... it makes a big change that does some really cool things for you.

Keep the documentation coming. You will have some very useful data points for the rest of us to learn from. So far nobody has used the Heyboer HTS8093 output transformer in this build. It should be a good match and I am anxious to hear your results.

thanks for the good thread!

rj

[M Fowler]

Hey I am curious what ever happened to this build?

[fishy]

Hey I am curious what ever happened to this build?

which build are you refering to?

[M Fowler]

Fishy I was referring to bluesbreaker62's Rocket 66 or Rockster

[fishy]

Cool. I saw your post then thought about my el84\ octal amp. I need to post that still but I have been a bit slow getting it done. A good reminder albeit indirectly.

[M Fowler]

Fishy I thought your amp was done?

[fishy]

Yes, it is but I haven't really posted on it yet. Later this week if I can get the camera out.

[bluesbreaker62]

Hi All,

Sorry that it’s been such a long time since I last posted.
I’ve been very busy lately and haven’t had any time for amp building.
I finished the amp some time ago, but I had to set it aside, so I haven’t tweaked it yet.

The amp fired right up, nu hiss or hum, so that’s good.

The downside is that the amp sounds like a fuzz running on a dead battery. Very splatty/sputtering sound, not nice at all. There also isn’t a lot of volume.

I’ve attached the voltage chart I made. Where would you suggest I’d start tweaking?



[img768]http://i610.photobucket.com/albums/tt18 ... G_1436.jpg[/img]

[img768]http://i610.photobucket.com/albums/tt18 ... G_1439.jpg[/img]

[img:602:741]http://i610.photobucket.com/albums/tt18 ... echart.jpg[/img]

[nickt]

My first thought would be you have oscillation.

Your wiring is very neat but the OT inputs are raised and near lots of other wires.

I had a bunch of problems with oscillation with my Lightning (half sized rocket basically) and it was the OT leads that needed moving.

Anyway hope this helps

Nick

[fishy]

I have only had a quick glance but V3 raises some questions for me.

Looking at pins 1 and 2 it looks very much like they are swapped over with the long tail pair input going to pin 1 and the PI going to pin 2. Looking at the voltages for v3, the plate signals on pins 1 and 6 should be much closer.

I can believe this would not sound so good.

Check that out and prove it or otherwise.

Nice looking build though.

[M Fowler]

Fishy,

Your right pin 1 and 2 on V3 are not correctly wired, good catch.

Mark

[bluesbreaker62]

Thanks a lot guys,

I would never have caught that.

Switched the wires and now it sound great with a strat.
Very clear sounding, plenty of volume and a nice crunch.

The eq. is also very effective.

Still needs some tweaking though,

The high notes can be bit raspy/brittle.

Also, it doesn't sound as good with humbuckers.
The overdrive becomes loose/undefined, with the buckers.

Any ideas on how to adress this?

Thanks again guys,

Robert