Why does my Rocket sound the way it does? (long post)

[Paultergeist]

.......which is to say, really, really good (or at least much to my liking!)

I was not really sure how to begin this thread, but it is in a quest for greater understanding that I kick off this thread. I have been a tube-amp DIY-er for several years now, and I have built a handful of functional tube amps from kits or parts. They all sounded pretty good in various ways. In addition, I have owned a number of pretty good-quality commercial tube amps over the years. All of these amps had their merits, and all of them sounded "good" to one degree or another in various contexts. One problem which has continually plagued me, however, was that I found distorted tube amp tone to do a terrible job of cutting through the mix of other instruments in a band setting. It seemd like -- with that harmonic distortion compression/sustain generated by over-driving tubes -- the *sound* of the lead guitar somehow got buried (a sense of dark, muffled, low-to-the-ground sort of thing). It would seem loud based on initial volume setting, but I just did not *hear* the solo rise up out of the mix. I don't know if others have also experienced this effect, but I have never understood the physics of the issue of "cannot hear the lead guitar."

Now this Rocket build....dimed through an attenuator with no effects......seems to have this clear, open, soaring, tone that seems to rise above ambient band mix, like an opera soprano singing solo over many voices in a chorus.....not louder per se, but one can really hear the lead voice. The distortion and compression is there, but, there is yet a sense of clarity to the notes. Straight into the amp, I love this tone; it is a tone I have been imagining in my head for some time, and now it comes out of my amp. What I am seeking to understand is how that tone is manifest? Power tube vs. pre-amp tube distortion? Less triodes run at higher gain? Some sort of dumb-luck as to how I got the lead dress? Scooped mids? Boosted mids? I am at a loss to account for what is happening......

Sorry for the long post; I didn't know how else to explain the effect I am perceiving. I'll appreciate any useful insights.

[matt h]

(deleted)

[dorrisant]

One thing... It probably doesn't have anything to do with "luck" when it comes to lead dress... That circuit is very forgiving when it comes to that.

Well, two things... The combination of parts is magic but I think the tone stack driven by a cathode follower is key.

Glad you are enjoying your Rocket, I think everyone should try one at least once.

Tony

[Colossal]

Paul, that is really great that you hit tonal nirvana. I know what you mean about the clarity and the singing quality.

If you haven't already, you might want to detail the attributes of your amp for discussion's sake: PT, OT, choke, caps, resistors, wire type, tubes, and then thoroughly document the voltages everywhere in the amp. Mark up a schematic. This will be good to have for reference in case it ever changes, but also so you can replicate it to some degree if you choose.

[RJ Guitars]

I sorta believe that the key to this great sounding amp is in the schematic and selection of good parts. You can mess that up with really bad lead dress but generally speaking all the right components in the right place is going to give the average amp builder a decent chance at building a good sounding amp. After that it gets down to squeezing the final few percent out of the ultimate components and using correct build technique (including lead dress). That is why I think the folks buying the "not quite authentic" Rocket amp packages are consistently able to build a decent amp. My 2 cents - YMMV.

[overtone]

my two € cents:

The Rocket seems to me to be an extremely clear and articulate circuit. You have your distortion and compression but with detail. My hunch is that the whole power supply string goes a long way to keeping the articulation and response just where one needs it.

In terms of sitting in the mix I suspect the Rocket has just the right amount of frequency "spectrum" and harmonics to get the message over without getting in the way of the other instruments.

t

[RJ Guitars]

my two € cents:

The Rocket seems to me to be an extremely clear and articulate circuit. You have your distortion and compression but with detail. My hunch is that the whole power supply string goes a long way to keeping the articulation and response just where one needs it.

In terms of sitting in the mix I suspect the Rocket has just the right amount of frequency "spectrum" and harmonics to get the message over without getting in the way of the other instruments.

t

will 2 cents buy more than it does here? just curious. I agree that the power supply is part of it...

In the old Trainwreck sales literature you can find the statement that 9 out of 10 owners of an original AC-30 preferred the sound of the Trainwreck Rocket over their original VOX... kinda wish I could get a listen to that VOX!!! wonder if that was with the original speaker in the original cabinet compared to a Rocket and an Ampeg speaker cabinet?

There is also something in there about taking all the best features of an AC-30 and omitting the not so great. Start with a proven great sounding amp and apply some better engineering (aka simplify it) and you have a platform that allows well trained monkeys and guys like myself to make decent amps. Add some good ears and a master builder has the formula for the Holy Grail of tone.

[Paultergeist]

My sincere thanks to all for the insightful replies. I'll try to add some meaningful commentary without making this too long-winded.....

It would be really helpful if you named some of the other amps you've built/played... otherwise it's sort of hard to talk about what of the rocket is different.

It would be a long list over the years, but I'll focus on the amp circuits I have built (a much smaller number than what I may have played).

Fender Blackface Twin (AB763 circuit): Mercury iron, SoZo signal caps, Sprague Atom filter caps, metal film resistors. 2 x 6L6 power tubes. Switchable fixed vs. cathode bias, switchable tone-stack defeat (boost). Pretty nice clean, but nothing special in the over-drive department.

Marshall 18 watt (normal channel / TMB channel): GDS OT, generic PT, SoZo signal caps, F&T filter caps, carbon film resistors. 2 x EL84 power tubes. Very gainy on the TMB channel; sounds great alone, but really gets buried in the band mix.

Dumble-inspired 22-watt variant (Brown Note D'Lite): Built as per the Brown Note kit, with their iron, Orange-drop (715) signal caps, Illinois filter caps, and carbon film resistors. 2 x 6V6 power tubes. A very grindy "Santana-esc" sound which -- while wonderful to hear solo -- again can be challenging from a "cut through the mix" standpoint. (Note: Due to numerous issues regarding questionable business practices, this opinion is not intended to endorse Brown Note Amplifiers in any way).

Weber-based "Smokin' Joe I" circuit: This was a parts build, using a single EL84 and whatever stuff I had in the bin. Worked okay, but not inspiring over-drive tone. Sold some time ago.

Fender "Champ" circuit: Another parts build. Heyboer OT, generic PT, a mix of other components. Single 6V6 power stage, but I have enough overbuilt iron to put in a EL34 if desired. I added a choke (not present in the original circuit). Takes pedals very well, a moderate "dirty boost" will drive the input stage decently if the amp is cranked-up.

Matchless-inspried DC30 (from a Ceriatone kit): I used everything from the Ceriatone kit (Ceriatone iron and filter caps, Orange drop signal caps). 4 x EL84 power tubes. This amp really missed the mark for me -- it never sounded all that good if one was going for a harmonically-rich overdrive sound (to my ears). Plenty of loud clean headroom...sold this one to a guy who liked a warm clean sound.

Been a bunch of tweaks and repairs, but I think this is my list of start-to-finish builds.....including the Rocket being discussed currently.

I don't know if any of your other experience with amps includes multi-multi el84 designs, but this is also worth noting. So not only is it in the 30w class of amps, but it's doing it with high-transconductance/gain power tubes. This and the lack of nfb give, i believe, much of the presence you're talking about.

Thank you for those insights, Matt. Are you saying that -- by design -- the EL84 is a high-transconductance power tube, or that the Rocket circuit uses the EL84s in such a manner? I do follow you on the lack of NFB.

I have never played an actual AC30, by the way.....

Thanks for the thoughts.

Paul

[Paultergeist]

.....I think the tone stack driven by a cathode follower is key.

Thanks Tony. I confess that I need to understand that part of the circuit better, but that gives me a place to investigate.

Cheers!

[Paultergeist]

The Rocket seems to me to be an extremely clear and articulate circuit. You have your distortion and compression but with detail.

Yes, I think that is very well-stated.

[Paultergeist]

.....Start with a proven great sounding amp and apply some better engineering (aka simplify it) and you have a platform that allows well trained monkeys and guys like myself to make decent amps. Add some good ears and a master builder has the formula for the Holy Grail of tone.

Simplicity was indeed one of the things that drew me to the Rocket. I have at times gone a bit over-board with trying to add switchable features to amps. Usually, I got the *features* to work....but.....it seemed like just having those extra switches in there -- even if said switches were turned "OFF" -- detracted a little something from the tone (?). I have since learned to strive for a more direct signal path. Master Volume (MV) controls have been -- in my experience -- particularly problematic.

In my case, I consider the "well-trained monkeys" reference to be an insult.........to monkeys! (LOL)

[matt h]

(deleted)

[Paultergeist]

Matt,

Thanks for the additional thoughts. It may not be entirely fair to cite my lack-of-love for the DC30 circuit as being representative of all DC30s, as it was a Ceriatone kit and there may have been deviations from what was intended from Matchless. It is also simply possible that there was some limitation on my part with respect to construction methods. I thought that the over-driven sound on that particular amp was terrible, but it is now out of my possession so I cannot research it farther at this time.

It seems that there is a lot of room for more understanding on my part as to the influence of the PI upon the sound. I hope to get to look into this a bit more, maybe tweak a few values in order to understand how the existing choices effect the overall tone.

Thanks again.

[RJ Guitars]

Because of the simplicity of the Rocket amp, you can deviate from the original Trainwreck Rocket layout a bunch and not ruin the magic. I won't say the same thing about the schematic and the parts selection but even there as you can see by the Z-Wreck and other Rocket deviations this is a very forgiving circuit that will tolerate a lot of freedom in how you build it.

Having said all that, it's worth a look at why KF settled on the layout and parts selections he did before you make any changes... not that we entirely know why he did some of those things.