Rocket Impressions

[CapnCrunch]

For those of you who have built Rocket Clones and/or variations of the Rocket circuit, what are your impressions of the amp? I just finished mine and have spent only about 3 hours playing it, but I have some initial impressions in just that short time. I have heard it described as an amp with all the good stuff from an AC30 and none of the bad. I hesitated to build this amp, because (blasphemy alert) I have never been a huge fan of the AC30 sound that I'm familiar with. i.e. Brian May, the Edge, George Harrison. The only AC30 user whose tone I really like is Mike Campbell (guitar player for Tom Petty). I was prepared for this amp to be congested and very compressed, because thats what I associate with the AC30 (I'm not saying this is correct, it is just my association).

That said, I was totally floored when I finally played the Rocket. It is one of the most dynamic amps I've ever touched. It is the total opposite of compressed. Even cranked up, it never sounds, or feels compressed. The other thing that I was not prepared for was the balance of the amp. Again, AC30's (or at least recordings of them) never have struck me as well balanced. They seem to pump the upper mids but seem lacking in the low end. By playing with the tone pots and the cut control, you can get the upper mid hump, but it always seems to be balanced out with a nice thick low end. So, when people say that a Rocket is an AC30 with all the good and none of the bad, if that means that the Rocket has all the chimey upper mid range magic of the AC30 with an awesome full range low end......I totally agree. Caveat, I haven't played any AC30's let alone any vintage ones, so I'm not qualified to compare and contrast. My intent in this post is to see what others think of the Rocket and especially see how people set their amps up. I'm also interested in what speakers people are using with this amp.

After a just a few hours(full disclosure), this is how I set mine up.

With my Tele (neck PU)

Volume 11 to 12 o'clock, Treble 1 o'clock,Bass 11 o'clock, Cut dimed
This gives an amazingly full thick, shimmering clean tone like a Super Reverb on steroids, and with a run of the mill ts9, yields almost dumblish lead tones (I'm sure it would be better yet with a good OD pedal).

With the Tele bridge, I found that I like to back off the Treble to 11 and set the Cut at about 2 o'clock. This works really good with delay, and yeilds a great modern country sound.

With the Les Paul

For cleans
Volume at 10 to 11 o'clock, Treble at 12 o'clock, Bass at 10 to 11 o'clock cut at 3 o'clock guitar volumes backed off to 6 or so.

For OD
Volume at 2 to 3 o'clock treble at 1 o'clock Bass at 9 to 10 o'clock, cut dimed.

Another cool OD sound was as above but with Treble at 0 and cut dimed with guitar volume all the way up.

I haven't plugged my Rangemaster into this amp yet, but I'm going to.........For speakers I've run mine through a 2x12 cab with one Celestion Alnico Gold, and a g12h30, and also a mid 90's 1960a with English Greenbacks.
I was a little surprised that I much preferred the 4x12 w/ Greenbacks for both guitars played clean. The 2x12 cab sounded awesome with the Les Paul in full overdrive while the greenbacks lacked focus and definition with the amp in full overdrive. This was the absolute opposite of what I expected.

[ampmike]

I love to hear somebody happy when they hit the finish line,Sounds like you just did,I think we are so used to thinking because we didnt buy this it will just be average sounding,But there you go ,you build it and you love,and its sounds awesome.
Good Job,Enjoy you new amp,Mike

[KellyBass]

Thanks for the detailed description of your rocket. It makes me to wonder about mine. I fired my rocket up for the first time last night and was quite surprised...it was very dark and murky sounding, with very little headroom. All my voltages are right in line with the ones on the voltage chart...so, I was scratching my head for a bit.

Then I remembered that I had placed a 82pf +/-10% silver mica cap on the volume pot...I didn't have a 100pf at the time. When I replaced this cap with a 100pf +/-5% cap, the amp opened up real nicely and definitely has the voxy vibe.

I'm still not sure if everything is right, though. It starts to break up pretty early...at about 9:00. It's also my understanding that this amp is pretty loud. Well, it could be my ears (I've been playing bass and standing next to Marshall stacks and Twins for about 30 years) but this amp just doesn't seem that loud. But then again, neither does my xpress! Maybe the lack of clean headroom contributes to the perceived lack of volume. I'd like for the amp to just start to break up at about 12:00...what would be a good way to accomplish this and open the amp up a bit more?

Thanks!

[crbowman]

IMHO, a good well serviced AC30 is one of the finest amps ever. Never played through a rocket before, but looking at the schem it should sound like a good 'ole Vox. Think about the example of the 4 guitarists you mentioned. All four have completely different sounds despite the fact that they use the same amp. AC30's do a great job of letting the sound of your guitar come through while giving you enough control to create a unique voice at a very reasonable volume level. Your Rocket should give you this as well.
OK, I'm off the soapbox now.

[M Fowler]

The EL84 Rocket amp is a loud amp and stays clean right up to about 6-7 on the volume knob. Has nice vox chime and a great amp.

The (EL34/6L6/KT66) Rocket amp is even louder and still great sounding amp non vox sounding better than Fender. Add reverb and you have a great gigging amp, that takes pedals well.

Mark

[rawnster]

Nice stuff, CapnCrunch. I feel pretty much the same way about my rocket. Loads of chime and charm. As with you, I play mine in church quite a bit, and never got a complaint about volume and such. Not that I have to play at a super low volume; but it just shows how good the tones are when the amp's not cranked yet hit with a wall of pedals for crunch, modulation, and drip. I've tried the amp with G12H30's, but felt it sounded a little scooped. Fanes and scummy's have sounded the best to me, so far. And you're right, there's something about a greenback that sounds stellar with this circuit. I can't remember but did you use open back or closed back cabs?

I know you asked in the other thread about delay pedals. I use DL4. It's a decent unit; and the presets are the best thing about it. When you've got to switch tones on the fly, it's really cool to have the pedal setup and ready to go. I also use a Fulltone Supatrem for tremolo; and old early 80's Ross chorus for Leslie effect. As Mark said, the rocket takes pedals extremely well.

[CapnCrunch]

I'm still not sure if everything is right, though. It starts to break up pretty early...at about 9:00. It's also my understanding that this amp is pretty loud. Well, it could be my ears (I've been playing bass and standing next to Marshall stacks and Twins for about 30 years) but this amp just doesn't seem that loud. But then again, neither does my xpress! Maybe the lack of clean headroom contributes to the perceived lack of volume. I'd like for the amp to just start to break up at about 12:00...what would be a good way to accomplish this and open the amp up a bit more?

Thanks!

I am not a trouble shooting expert, but if you post pics and ask the gurus here, I know you'll get some great ideas and help. I had similar issues with mine when I fired it off. A change of bias resisters and getting everything solidly grounded, mad a world of difference in my amp. Now my amp is pretty darn clean to about 2 or 3 o'clock with my Tele, and to almost noon with my Les Paul (with the guitar volume backed off a little).

I don't know what trannies and other parts you used in your build, but for what it's worth, I tried to stick as close as possible to Ken's original components. I also studied Allyn's Rocket for parts and layout. He posted pics a couple years ago and that thread can be found here: https://tubeamparchive.com/viewtopic.ph ... ght=rocket

As far as the comparison to the AC30, this circuit is obviously pretty much the same with some power supply differences. I suppose it would be incredible if it didn't sound a lot like an AC30. I hesitated even to compare, because as I said, I've not played AC30's and my impression of what they sound like may be very innacurate. I'm limited to the recorded sounds that I know are AC30's, which, by and large, I personally don't care that much for. I didn't mean to slam what may be the favorite amp of many folks. If it came out that way, my apologies. If good old AC30's sound as good as the Rocket, then my appreciation for them has increased immeasurably, and I now understand why people are willing to pay so much for them........

[crbowman]

I didn't mean to slam what may be the favorite amp of many folks. If it came out that way, my apologies. If good old AC30's sound as good as the Rocket, then my appreciation for them has increased immeasurably, and I now understand why people are willing to pay so much for them........

No prob Capn! I guess what I should have said was Welcome to the wide, Wide world of AC30 variants of which, the Rocket may be the best.
If you ever do get the chance to play through an old Vox/JMI AC30 (particularly if it still has the old blue alnicos!) jump on it! I had one come across my bench a few years ago, tried to trade the guy my car for it, but no go.

[CapnCrunch]

I've tried the amp with G12H30's, but felt it sounded a little scooped. Fanes and scummy's have sounded the best to me, so far. And you're right, there's something about a greenback that sounds stellar with this circuit. I can't remember but did you use open back or closed back cabs?

My 2x12 is an open back with alnico gold and g12h30. The 4x12 is a mid 90's Marshall closed back with English greenbacks, which I re-wired and sealed per Jim's (of Scumback Speakers) instructions. This transformed the cab from ice-pickish and unusable into a pretty sweet and totally respectable cab. I would love to try the Scumbacks and the Fanes, but don't have the $$ right now.

My impression is that the character of this amp is extremely dependent upon which speaker(s) you run it through. Probably true of any amp to some degree, but the difference is much more pronounced with the Rocket then with any other amp I've played. I've come to the conclusion, that much of the compression I referenced in my original post is likely attributable to the old Alnico G12's. I think that's why I like the sound of the amp overdriven into my 2x12. The alnico gold yields that natural Alnico compression which is good with overdrive. The ceramic greenbacks don't do the same thing, and have a more "natural" open tone which I really love for the cleans in this amp. That's my theory anyway. I'm guessing that, set clean, this amp might sound absloutely fantastic through EVM12L's or through JBL's. I don't have either, so if anyone has them and can try it. Please do, and report

[KellyBass]

After trying a LOT of things to get this amp to open up more, I ended up with just a couple of changes...I changed the 2nd stage cathode resistor from 1.5k to 1.2k...still using no cap. I changed the first stage cathode bypass cap from 22uf to 15uf and the 47pf treble cap to 100pf. Now I'm feelin' it! She cleaned up real nice and gained some serious sparkle. I love this thing! But your results may vary...All this is probably due to the crappy off-the-shelf tubes I'm using...or perhaps my lack of healthy eardrums.

[Structo]

My 2x12 is an open back with alnico gold and g12h30. The 4x12 is a mid 90's Marshall closed back with English greenbacks, which I re-wired and sealed per Jim's (of Scumback Speakers) instructions. This transformed the cab from ice-pickish and unusable into a pretty sweet and totally respectable cab.

Can you describe what you did to the 412 to sweeten it up?

[CapnCrunch]

After trying a LOT of things to get this amp to open up more, I ended up with just a couple of changes...I changed the 2nd stage cathode resistor from 1.5k to 1.2k...still using no cap. I changed the first stage cathode bypass cap from 22uf to 15uf and the 47pf treble cap to 100pf. Now I'm feelin' it! She cleaned up real nice and gained some serious sparkle. I love this thing! But your results may vary...All this is probably due to the crappy off-the-shelf tubes I'm using...or perhaps my lack of healthy eardrums.

That's cool. I ordered a bunch of different values in caps and R's thinking I would want to tweak this amp, but I don't see that happening maybe ever. I am glad to hear you finally got yours where you want it.

Tom,

I think the biggest single contributor to the change was switching out the stock 22 ga. speaker wire with 14 ga. I also wired it according to Jim's instructions. It is slightly different then the the modern Marshall series-parallel wiring. I wired it the way the early Marshall cabs were wired. It's still series-parallel but it's different then they do it today. I'll see if I can find the diagram. If I do, I'll post it. While the back was off, I caulked the joints where the baffle meets the sides and top/bottom of the cab.

I don't know for a fact, but I suspect that both the wire and the caulk increase the low and low mids. In the end, I believe the speakers have just as much high end, they just end up having much better balance because they have much better low end response. As such they don't "appear" to the ear to be too bright, where they did before. I honestly don't know if the change in how it's wired contributes anything. Some swear that it does, but I haven't put it back the way it was but for the heavier wire to see if I could tell any difference. It sure didn't hurt.

[CapnCrunch]

Here's a layout of early Marshall series/parallel wiring.

[CapnCrunch]

I actually went back and reviewed an old thread that I started here on my unusable 4x12 Marshall. It was about 8 months ago, and at the time I thought I would only use the Rocket cranked for overdrive tones, and that was the reason I wanted to get the 4x12 to a place where it was useable.

Wow, I was so wrong. My honest assessment now, is that the Rocket is a much better clean amp then it is an overdriven amp. The other shocker for me is the fact that I think it sounds best clean through a 4x12 with Greenbacks. I have found, however, that the magic of the 4x12 disappears when I use my attenuator. The cab gets really dark and muffled. Without the attenuator, it's glorious!

[Structo]

Thanks Cap,

I have a cheaper Marshall 412.
I'll have to pop the back off to see how it is wired.
It only has one jack, not the typical mono/stereo switch.