Building a Rocket - Layout Check for group build

[Ampsterdoom]

A couple questions.

Is it possible to mount the VVR pot on the back panel? I got one of Lonely Ravens nice wood front panels with my Rocket parts and I would like to leave the face panel alone.

The VVR sounds like a cool idea. If it doesn't change the tone then could you just hard wire in a few specific resistor values on a rotary switch and say have 1-4-8-16-32 watts? Then expect to have similar tone for all those settings?

Dr. Doom

[UR12]

A couple questions.

Is it possible to mount the VVR pot on the back panel? I got one of Lonely Ravens nice wood front panels with my Rocket parts and I would like to leave the face panel alone.

The VVR sounds like a cool idea. If it doesn't change the tone then could you just hard wire in a few specific resistor values on a rotary switch and say have 1-4-8-16-32 watts? Then expect to have similar tone for all those settings?

Dr. Doom

Yes and yes.........The pot and the mosfet come unmounted so you can mount the board, mosfet and pot in different locations if you want.

[RJ Guitars]

Good Day AmpGarage,

With a little time available yesterday to put toward the Rocket build, I made measurable progress on my amp.

I ordered one of Dana's VVR boards with the parts pre-loaded... hoping I can work it in to look and act respectable.

You can now see the hybrid aspects are becoming more clear but hopefully even the Trainwreck Police will find a lot of Rocket in this work...

rj

[Sven]

Greetings,

Thanks everyone for the great input. I have done my own layout, better than the previous, hopefully (previous ones were erased to clean up this thread a bit). First, I really do not like the ¨stack o' caps¨, the six-pack of electrolytic capacitors (a six-pack of lytes, right?), since it looks and comes out pathetic in terms of engineering elegance and such. I really do not see ANY reason to have them stacked-glued and bunched up like that. If someone can convince us that it is important for ¨the sound¨, I shall thow away my engineering degree in a mud puddle. So, I lined up the caps properly, safely and elegantly, like ALL other amplifiers ...

Also, I red plexi_67 post, a while ago this year, about grounding scheme for TW amps, and liked it a lot. So, I have attempted to put together a scheme along the lines of his recommendations, the scheme without having to solder onto pots. Also, I opted for no dual power switch. So, without further ado, here is the layout drawing, kindly comment if you like. Thanks.

Sven

[RJ Guitars]

Hello AmpGarage,

I have completed my first Rocket build and I am greatly pleased with it.

I powered it up for the first time at some point after midnight last night. I played it quietly for a while then both of us rested.

Today, I've played it a couple hours and I am greatly pleased with the initial sound and feel of it. My first discovery was that it got loud quickly... soon followed by my second discovery, it breaks up pretty early, and then finally I found that it isn't altogether tremendously loud even when you get it really cranked.

I was also pleasantly surprised by how effective the half power option works. A significant change in volume without a big change in tone. I was expecting the half power to have more impact on the tone flavor and less on the volume... a gratifying effort that I expected less from.

I have a ton of gut shot images and a few dozen lessons learned, all of which I am willing to post for the forum... one of my early commitments to those who provided Rocket info and the others who helped me gather it up.

Does it sound like a real Rocket? I'm not sure I would know. It sounds pretty cool and it seems to like my Les Paul as well as my Strat. As soon as I get it into a cabinet and one of Lonely Ravens faceplates on it I'll follow up with some sound clips and then we can all evaluate the sound of it for ourselves.

In the near future I'll provide more details about the design, layout, schematic, component values, and hybrid variations...

rj

[Mark]

Dear RJ

Nice looking build. It is a bit of a mystery why KF decided to mount the caps on the chassis and not a circuit card.

There are recordings of a Rocket floating around. The prototype amp I build sounded similar to recordings I've heard. Though who knows unless the amp is in front of you?

Nice and jangly at lower volumes, when turned up the amp thickened up and my Strat sounded wonderful. Humbuckers sound good too.

I preferred an open backed cab with this amp.

[Fischerman]

Looks great RJ!

It looks like you went to a little extra effort to ground your preamp buss over by the IEC receptacle. Any particular reason for that?

...it got loud quickly... soon followed by my second discovery, it breaks up pretty early, and then finally I found that it isn't altogether tremendously loud even when you get it really cranked.

Nice and jangly at lower volumes, when turned up the amp thickened up and my Strat sounded wonderful. Humbuckers sound good too.

That's pretty much how mine behaves. The break-up is pretty gradual though...there is a nice smooth, gradual transition from clean to slightly dirty.

I noticed you have the cathode bypass cap for the second stage already in place to try...I tried one in mine and although I didn't give it much chance I think I preferred it without the bypass cap on the second stage.

[Lonely Raven]

Looks good! I've still not had time or $$ to order parts and build mine up. I appear to be the slow one of the group.

I'm eager to hear clips from the group as a whole, as I feel if we hear enough of the builds we will have a better idea (average the sound) of what a Rocket should sound like.

Though clips of a real Rocket would help. Anyone have one they can loan to Glen?

[Curbdog]

RJ, looks great ! Love the grounding buss out from the board and off the POTS...nice and clean

Hey, any reason you used 1 watt resistors? I understand that 1/2 watt will do the job. Can 1 watt carbon films be noisier than 1/2 watt, or don't we need to worry about that?

Got distracted with an amp repair, but I am back to my Rocket build now. Thanks for the pics and clips

[RJ Guitars]

It looks like you went to a little extra effort to ground your preamp buss over by the IEC receptacle. Any particular reason for that?

I learned amp building from a bunch of HiFi guys who really insist that star grounding is critical for noise and avoiding ground loops... So at this point, wire is cheap and those guys are way smarter than I am... I would have to build one another way to actually tell you if it made a difference.

I noticed you have the cathode bypass cap for the second stage already in place to try...I tried one in mine and although I didn't give it much chance I think I preferred it without the bypass cap on the second stage.

I put that there and I will either mess with it using a jumper or if I think it has potential, I'll add a switch.

Hey, any reason you used 1 watt resistors? I understand that 1/2 watt will do the job. Can 1 watt carbon films be noisier than 1/2 watt, or don't we need to worry about that?

Curbdog, My reasons are not very technical... I keep 1 watters in stock and I think they are easier to handle that the 1/2 watt size. Are they more noisy or otherwise problematic... I dunno. Notice I did use a half watter for the 10K that is soldered to the pot. It was a little cramped for a 1 watter in there.

...It is a bit of a mystery why KF decided to mount the caps on the chassis and not a circuit card.

There are recordings of a Rocket floating around. The prototype amp I build sounded similar to recordings I've heard. Though who knows unless the amp is in front of you?

Nice and jangly at lower volumes, when turned up the amp thickened up and my Strat sounded wonderful. Humbuckers sound good too.

I preferred an open backed cab with this amp.

Yeah I would love to know what he had for motivation in the "Stack O' Caps". I've changed enough filter caps that I didn't want to try it.

I'd love to hear a Rocket and see how close we got... but I am greatly pleased that we seem to all have some similarity in the sounds.

I hope to try an open back cab tonight. My first tests were with a single 12 and then a 2-12 sealed cabinet.

Thanks for the kind words!

rj

[nickt]

Hey, any reason you used 1 watt resistors? I understand that 1/2 watt will do the job. Can 1 watt carbon films be noisier than 1/2 watt, or don't we need to worry about that?

With noise bigger is quieter however ALL the noise you get in an amp (any amp) comes from the first gain stage. If you can minimise noise in the first gain stage then possibly you might have some benefit from looking at other parts of the circuit.

Having said that: in high gain amps (that dump a lot of signal) the noise issue might be more spread around.

Rocket dumps gain via the volume control (as do Express and Liverpool) so the only places that make a big difference in noise are first stage and maybe the first stage after the vol control. but YMMV

[guitarsnguns04]

dont feel bad LonelyRaven..I am finishing up a express build but will be sourcing parts for my rocket build soon. I guess you and I will finish up the first round of builds..lol

[Zippy]

I hope to try an open back cab tonight. My first tests were with a single 12 and then a 2-12 sealed cabinet.

I had the pleasure of sitting down with that amp the other day and couldn't help but smile when I played it. Lots of usable tones with both Strat and Les Paul - a very musical amp.

Regarding larger resistors: As I recall, the larger cross section of the higher power resistor reduces the electron flux through the medium and thus reduces Schottky noise (a small fraction of the overall noise).

[RJ Guitars]

Tonight I tried an open back 2-12 cabinet with my Rocket build. I really liked it better than any of the previous setups I had tried.

My 2-12 closed back cabinet sounded good but eventually got muddy when I really cranked on the amp. After tonights test I'm convinced that this cabinet and speakers are not ideal for my Rocket amp. This set of speakers are also not very efficient.

The cabinet I tried tonight had two Celestion Vintage 30's in an open back twin shaped cabinet. The amp really sang and I couldn't play it loud enough to make any mud, just great tone and clarity. I also had a noticeable increase in volume. I'm becoming more inclined to think I'll need the VVR to make this unit small venue friendly.

Does anyone have a thought on the ideal speaker cabinet for a Rocket and also I was curious if anyone has had any experience using a pair of 10's in these cabinets?

rj

[dansamp]

there is a used Bruno Underground 30 at my local G.C.
it is a 2x10 combo with celestion speakers
it sounded good when I tried it in the store
Dan......
p.s. couldn't really play it very loud in the store though