ROCKET! (with original A470 iron)

[MHProd]

First, thanks again RJ for the wonderful parts and amazing service!

Built in 3 days!

The amp sounds fantastic. Super quiet. I followed the original circuit with the following exceptions:

470Ohms screen Rs vs 100 Ohms
10K screen grid Rs vs 1K5
Added a 220K to ground on first caps.

Used the 250V tap on the PT.

First impressions with these settings:
V5.5, T8.5, B5, C8.5.
I found the amp to be a tad dark initially but some tube rolling helped a bit. Fat bottom indeed BUT quite controlled and very articulate, certainly not boomy or muddy (played with a Les Paul with original PAFs). Mids are not as scooped as I expected which is nice. Top end is very pleasing, not harsh at all.
I find the amp to sound a tad congested and I guess it will open up after more than 25 minutes of playing.

First tried with Gold Lions N709/EL84s but switched to a quad of mid 80s 6p14p which made the top end more alive although it still lacks some chime.
Right now the preamp tubes are old Mullards in V1 and V2 and a 12AX7LPS in V3. A new Sovtek 5AR4 is in there but I tried an old Mullard GZ34 which sounds good, different but not necessarily better... Cab has 20W G12Ms with 103 cones. I think the amp will be better suited for an open back cab.
I like crunch sounds and the amp seems to come alive around 4. Sweet spot is probably around 6 or 7. I expected the amp to overdrive a lot more (I had planned to switch the first plate R to a 120K but that won't be necessary). I have a 1965 AC30TB chassis here which has A LOT more drive (I went through it before and was never able to figure out where all this gain came from).

Anyway, the only thing I'd like to hear more of is some air/chime at the top. Low end is solid and muscular and mids are present enough.

This is my first Rocket, never heard another one in person. I suspect my AC30 doesn't sound like it should... Definitely more chime but a lot more breakup.

I'm sure the amp needs some good burn in time but I'd be interested in hearing some opinions/experiences. I'm pushing the Treble quite a bit on the amp while the Cut is almost maxed out (so not much "cut" is happening). I'm wondering if using the 280V tap on the PT might be a better choice...

[M Fowler]

I like WGS Veteran 30 speakers open back.

I like a bright switch on my Rockets 250pf/500pf and I usually use the 500pf setting. No 100pf on the pot.

I would try JJ EL84s for chime and the 6p14p are darker.

I like 100R screens with 1k5 grids.

Definitely need 220k plate for breakup.

Not necessary but I always add it anyway is bypass cap 25uf on 2nd stage.

Mark

[MHProd]

Thanks Mark!

[Winder]

Looks very nice. Haven't built a Rocket yet. I set my Bright Switch up something like Mark's ... 330pF/500pF. 100pF is too dark and unusable for me.

[Reeltarded]

I can't get chime out of PAFs.. Rics or Fenders or Retsches chime all day.. also get the sound you want with the cut defeated, cut until it sounds however more pleasant, then DIME the treble. There is chime in there. Mostly run ACs LOW LOW volume for anything clean with the tones dimed and the cut up enough not to make you twitch when you bash it.

I think your volume expecation is not what you think you hear on recordings. 3 or 4 and its already barking.

[dorrisant]

...the only thing I'd like to hear more of is some air/chime at the top

At the second stage, the one that feeds the cathode follower... add a 680Ω resistor from cathode to ground, in parallel to the 1k5. Put it on a switch... boost and chime. Use it with or without a bypass cap (22µF)... put that on a switch too. Tack it in and try it =

[MHProd]

Thanks Dorrisant! I'll play some more and report back!

[Mark]

Your Rocket is quite different from my Rocket, it has a stack of chime, I was thinking of removing the bright cap altogether. My amp uses a Pacific output transformer and a Classictone power transformer, I have a rail voltage of 315VDC which is a little high for a Rocket which are normally around 300VDC.

I have Russian output valves and Amperex 12AX7's, but it was still chimey without them. I think the amp sounded fatter with 12AX7's with large plates, maybe try a little valve rolling for chime?

For speakers I have a AC-30 sized cab with a Celestion Blue and a H30 in it, they are eight ohm speakers wired in series.

[M Fowler]

...the only thing I'd like to hear more of is some air/chime at the top

At the second stage, the one that feeds the cathode follower... add a 680Ω resistor from cathode to ground, in parallel to the 1k5. Put it on a switch... boost and chime. Use it with or without a bypass cap (22µF)... put that on a switch too. Tack it in and try it =

On some Rockets I add that bypass cap boosting with mini toggle switch; push/pull pot switched; and sometimes add foot switch.
Some guys even forget they have that push/pull boost switch in their Rocket. It does add some more air.

Mark

[MHProd]

The amp started to open up after playing some music through it for a few hours for the last few days.

There is some chime going on now. Probably the best amp I built so far... The 6p14p annihilate the gold lions which sound very flat/boring in comparison.

The low end is bigger with an old GZ34 (Mullard Cv137 version) but there's more punch from the Sovtek which I prefer a bit right now.

In most cases, I've been able to source vintage iron and it makes a world of difference... My amps are usually never too bright.

I'm tempted to use a second bypass cap to see what it does but the amp has such a nice ring to it, I'm reluctant to touch anything (except for V3, see if I have something better than the LPS).

I really think there's significant tonal differences compared to an AC30.

I'd take this amp over an Express any day... (mine has vintage iron too). I'll build a Liverpool soon though.

I still have a spare Dynaco, thinking about trying a SW30. Anyone has a layout? Can't seem to find it in the docs section.

[Mark]

The songwriter 30 is in here as I remember seeing it. That's a big call that the Rocket is better than the Express though you're not the first to say it. Why so?

[MHProd]

I looked again but can't find the layout...

I never said the Rocket was better than the Express... It's such a different amp... I guess it suits my playing style better, I don't need tons of gain, just a Big crunch sound. Right now, my Express has a pair of 6V6s and a 12AY7 in the PI. Sounds OK... I spent a lot of time listening to recordings on Youtube / videos of original amps and mine certainly sounds in this ballpark, especially with the Stancor OT. But it's not a sound I've been able to bond with... I find the mids too forward and the amp lacks some size in the bottom end (especially compared to the Rocket and despite the extra .0022uf cap in the preamp, ala Ingrid). It's a nice sounding amp, not too bright, I actually use the switch with the 500pF cap on, just not my cup of tea. I've enjoyed clips of Liverpools a lot more and that's why I want to build one. Having said that, there's something special about an Express with a good pair of XF2s... Now that's a cool sound but it just doesn't match my playing style.

[Mark]

Have you tried removing the 500pF treble cap and replacing it with a 50pF cap, that should give you some of the Liverpool vibe. Try adding another 0.0022uF cap across the other 0.0022uF, and see how that sounds.

[hitchcaster]

i tried the original A470 iron in my rocket.. then compared with the pacific... the pacific sounded way better to me... i don't think the a470 stock is what was in a rocket based on what i heard.. him and merrin must of done something to it to make it work for the rocket.. i don't know whats possible as far as modding a a470, but i just feel that it can't be stock in the rocket the way it sounded to me.. maybe im wrong but thats what i think. it sure would be cool if the final secrets of the rocket were let out of the bag

[Mark]

I have the Pacific transformer in my Rocket clone. Haven't compared it to an AC-30 but it does sound good.