Gathering input for big bottle rocket build

[donzoid]

Yep...I have an affliction.

Over the last year I have been slowly collecting the parts for a "full power" Rocket using kt66. I got the iron/chassis off of the sale section, one piece at a time. Oddly, both the PT and OT are Heyboer's.

I am planning to use a single board like KellyBass just did as I also want to keep as much (or all) of the leads "above board" or not running across/under...

I've looked at a TON of great (really great) builds for these here, and have a few decisions to make:

Diodes or GZ34 - this has been discussed at length and given the GZ is a "stiff" recto tube I wonder how much difference it will make. I'm curious what those here think, who have built both. I'm leaning toward the tube, because my 2 hole Rocket is sounding so good, but that's using a 5y3 so the sag factor is pretty noticeable.

Reservoir - I know I can go higher like 100uF if diodes, but have read about the strain on even a GZ if balancing resistors aren't used on the sec. to increase the PT's reflected total impedance. Or conversely using two 33's to make 66uF instead of an 80uF reservoir to be easier on the life of the tube. What's the downside of that?

Couplers- I noticed on some builds, some of you are using .1's as couplers instead of the .047's. Is this to "bring out the best" of the big bottles? Or for more gain, tonal diff. noise, or???

Not sure yet if I want to try including reverb, but seriously considering it. I am going to use one of Colossal's relays to switch in the 2nd stage cap, and extra dividing resistor (off) at the PI as a "lead boost" since this is gonna get gigged...prolly a lot. And if finances allow, I hope a VVR as the MV in my Express has proven repeatedly to be a significant compromise on the tone (no surprise there 'cause of its PI driven topology).

Just trying to not go off in the weeds "too far" in the planning stages. Any of you guys/gals who build these things regularly please feel free to gimme your .02, and a big THANKS from the noob!

[KellyBass]

I gotta tell ya, I don't think I'll be building any more rockets without that reverb circuit...it's just that good to my ears. It's very transparent...and subtle...compared to most other reverb circuits that I've tried. It doesn't at all, seem like an "add on".

I ended up using 2 33uf's for my power supply reservoir...i've had bad luck recently with gz34's and didn't want to take any chances. All of your ideas for your build are great...what is the size of your chassis?

I'm sure that you'll want to do your own single board layout, but if you want to see my layout for any ideas (bad?) just holler. I'm gonna start on my big bottle version this weekend. I'm looking forward to resolving a lot of mistakes that I made in my first single board go 'round.

[sepulchre]

If finances are against the VVR you might consider a PPIMV which leaves the PI tone intact.

[JoeCon]

Don

I went with diodes just for the simple fact you don't wanna be changing tubes at a gig when the recto fails, which I've had happen. OUCH!

I went with the same supply that Mark Fowler used in his 2 EL84 Rocket and like Kelly two 33uF cap, for the reservoir.

And yes the PPIMV is nice, just a touch down and then I can really crank the gain. NICE!! With my Rocket and Liverpool I always come back to the KT66 Rockster.

Try it, you'll like it.....

[matt h]

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[JoeCon]

Matt

OK power supply dummie here...
So cap then choke then another cap then plates??
Usually it's cap to plates choke cap to screens yes??
So pi filter gives better smoothing...see power supply dummie!

[donzoid]

Thanks everyone. I appreciate the input! Hoping to avoid mistakes (unlike my 6v6 fiasco).

Kelly, my chassis is the standard wreck size 17x8x2.5 its unpunched so I can do whatever I want with layout.

I do have a question, or pretty much the same clarification as JoeCon...Matt do you mean what he described? I have a choke but it sounds to me like you are saying to place that and the cap at a different location in the string? Or do you mean in addition to the existing choke location (I "think" that makes a CLCLC???).

[JoeCon]

Don

Yes cap to choke to 2nd cap and then to OT center tap for the plate voltage. So even the plates go thru the choke..."pie filter" LOL.

[matt h]

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[matt h]

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[RJ Guitars]

Don, my own thought is that KF used the GZ-34 in the rocket because he was working on perfecting the AC-30 and he didn't want to deviate too far from that amp. Somewhere in the archives there is a quote from KF where he says that the GZ-34 sounds most like a solid state rectifier. I have always found that to say, in some offhand way, that he preferred the way solid state rectifiers sound and perform. With a set of octals in the output section you're far enough away from the AC-30 to feel free to go with 25 cents worth of diodes. YMMV

However, if there is some sonic magic in the GZ-34, consider emulating it with a simple circuit (see attached image)... I forgot where I picked this up but it's a great little piece of work. If you try it let us know how it works out.

I love the KT-66 output tubes in my Rockster builds. I have also heard some great tones form a pair of old 5881's... lots of great options for output tubes in the Octal configuration.

Also, I'll post the combo cabinet drawing you asked about in the PM. It's a great cabinet size for a small combo amp. For the next iteration I would not make the cutback on the top like the drawing shows and a few other subtle changes to make easy to slip the amp in and out. Also, pardon me for the error in what is clearly the top view that is labeled as a side view??

Enjoy!

[sepulchre]

I recently chose to make such a replacement in a design I've been working on and found this useful:

https://www.youtube.com/watch?v=HScmoReY2Zs

It has nothing to do with guitar amps but gives you the math needed (simple) for the conversion. It worked great for me.

[donzoid]

Thank you all!!! Lots of great stuff here to chew on. Really great.

What type of diodes are the using there RJ, just 1n4007's or are they "freds"?

[matt h]

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[KellyBass]

+1 on the uf4007's. My o'scope highly recommends them.