One More Fresh Rocket Build

[gktamps]

Thought I'd share my recent Rocket build.

PT and OT from Allyn, as is the chassis. Circuit is modified from stock, like my last build, using PIO film/foil NOS Russian caps, filter caps on a board, and the treble and bass circuit mods that I've put on switched pots. These give lots of tonal variations, cuts the tendency towards tubby bass, plus gives more drive when wanted, without bypassing the second triode cathode resistor.

Tone is outstanding, just a tick less glorious than my last build, but that's probably because of the tube selection. I started off with Sovtek current production input tubes and JJ output tubes, but tube rolling had me ending up with an NOS Wollensack branded tube in V1 and Svetlanas in V2 and V3, which really helped the tone. I'll be switching the JJs to NOS Russian 6p14ps if more break in time doesn't bring the amp up the last few percent.

Cabinet is a custom build from Jeff Jones, who let me pick through a bunch of photos of samples. A beautiful job, to be sure!

Next post of photos... Rack of TW amps from top left down: Liverpool (Richie); high-gain Rocket; Express build I finished a couple of months ago; Rocket with mods similar to this build, which sits atop another Rocket with tone and gain mods, using a 5k Pacific OT from RJ and a Heyboer PT.

These amps really inspire me to play!

Cheers,

Greg

[Mark]

I'm building or should I say rebuilding a Rocket now. Do you have recordings of your Rocket amps or pictures?

[martin manning]

Can you detail your treble and bass circuit mods? I have a set of Allyn's transformers, and I'm currently planning and gathering parts for a Rocket reverb.

[gktamps]

Original post describes photos...

[gktamps]

I'm building or should I say rebuilding a Rocket now. Do you have recordings of your Rocket amps of pictures?

Hi Mark,
I don't have any recording gear anymore - sold it all and haven't set up anything that would sound good. I'm going to work on that, now that I've been able to work on my chops!
Pics have just been posted - thanks, Mark.
Greg

[gktamps]

Can you detail your treble and bass circuit mods? I have a set of Allyn's transformers, and I'm currently planning and gathering parts for a Rocket reverb.

Hi Martin,

Here's what I've been refining for myself over the last several Rocket builds:

1. Switchable C5 - either 50pF or 50+500pF parallel treble caps.

This gives a nice boost, drop some bass (still enough available by bass pot adjustment), and adds some grind and grit.

2. Switchable C6 - either .0022uF, or .01uF + .0022uF in parallel (last build = .01 or .01+.01).

I was trying to find a way of dropping some of the "tubby" bass that Rockets can exhibit, and had tried dropping C8-C11 values, but didn't like the results. I have found I prefer to tone shape earlier in the circuit. I get a little popping with the switch from .0022 to .01 in parallel with .0022, but none when switching from .01 to .01+.01. .0047 also works well in lieu of .0022.

3. Variable 0-250k PI input resistance (pot) to replace R10 - not what you were asking about, but thought I'd detail this also.

Did this just to upset the apple cart - adds a different flavor of clipping by driving the PI hard, it seems.

These mods do a great job of accommodating pickups of different output characteristics, and I'm not feeling the need for dirt pedals anymore.

Last observation: I've built 7 Rockets now, and have used Heyboer, original Dynaco A470, Edcor, RJs Pacific OT, and Allyn's Pacifics. My best sounding builds, to my ears, have been with Allyn's Pacifics.

Cheers,

Greg

[martin manning]

Fantastic! Much appreciated!

[M Fowler]

Nice job as always love your arsenal.

The most gigged amp I have is my Normster Reverb Rocket, it has the sweetest tone, no noise and lots of features. Currently working on a rj version.

Bright switch 100pf-off-500pf
Foot switchable bypass cap boost V1a 10uf
Reverb with switch to pad down reverb when the amp gets gainy.
Watts control pot (PI bias) works great, no scratchiness and adds a different flavor of gain.
6550 output tubes/currently running EL34's.

https://tubeamparchive.com/viewtopic.ph ... erb+rocket

Mark

[gktamps]

Thank you, Mark. Your reverb build sounds excellent, too.

I've been using the 100pF-off-500pF bright switch on almost all of my Rockets, but on my last build used a small potentiometer to adjust (edited - see photo) a 470pF NOS Russian mica cap to give me more control. I like it so much I'm going to use it again when I can source more surplus small pots to fit the 1/4" switch hole. My damned electronics surplus store closed and I have to buy everything online now!!

I have installed foot switchable bypass cap boost on a few of my builds, but had problems with RFI, so abandoned it in favor of my current approach, though I continue to put turrets on my boards just in case...

One of my earlier builds was a half-power Reverb Rocket using RJ's circuit ideas (oh man, you folks here have taught me so much since then). Plenty of reverb - I use it down at 1/4 or so. I like your idea of padding it with a switch.

I'll be building a big bottle Rocket soon, using an OT from Robert Hinson.

Cheers,

Greg

[M Fowler]

How about using those surplus panel mount trimmer pots with long shaft for knob unless audio pot is needed.

[gktamps]

That's pretty much what I used - it's the small, square black object (rear of pot) to the left of the volume pot in the photo. I used a linear taper, and mounted the cap to a small piece of perf board for lead hookup.
Cheers,
Greg

[Colossal]

Greg,

That's a really slick looking build. You've got quite a few in the stable there!

[gktamps]

Why, thank you, Dave!

[martin manning]

That's pretty much what I used - it's the small, square black object (rear of pot) to the left of the volume pot in the photo. I used a linear taper, and mounted the cap to a small piece of perf board for lead hookup.

It looks like electrically you have the 500p bright cap in the usual location going from the top of the volume pot to the wiper, but the variable resistance is in parallel with the cap? What value is the pot?

[gktamps]

It looks like electrically you have the 500p bright cap in the usual location going from the top of the volume pot to the wiper, but the variable resistance is in parallel with the cap? What value is the pot?

Hi Martin,

Yes, the trimmer and bright cap are wired in parallel, with the wiper and one leg to one side of the cap (sorry, not 500pF as previously stated, but 470pF) and to the wiper of the volume pot, the other leg to the other side of the cap and the volume pot, etc.

The pot is 100k, but I just used the only small pot I had; do you think a different value would be better? The pot is a Bourns - do you know where I might get more, surplus stock?

Cheers,

Greg