Dwarf Tube Rocket Amp

[rbryerton]

Here's some voltages for anyone interested.

[M Fowler]

Rob,

Thanks for the information, I will be tackling this project soon and information like this is very helpful.

Mark

[RJ Guitars]

Totally excellent work by Rob in putting together his build and sending me back several fixes on the schematic and layout drawings...

I updated the schematic to Rev 1.2. If you have anything previous it is close but not quite on the money.

Thanks again Rob... looking forward to the gut shots and the sound clips.

rj

[rbryerton]

Glad to help wherever I can...

Here's some gut shots. Note that I'm tweaking on this amp still, but haven't deviated from RJ's schematic that much. My changes have been:

Dropped the cut control (I never use this in any of my amps) and used the pot as a mid control, bypassing the onboard trimmer.

Added a 0.68uf bypass cap to the 2nd stage cathode resistor.

Here's some pics:

Check out how small it is on top of my regular Rocket clone!

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0001.JPG[/img]

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0002.JPG[/img]

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0003.JPG[/img]

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0004.JPG[/img][/img]

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0005.JPG[/img]

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0006.JPG[/img]

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0007.JPG[/img]

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0008.JPG[/img]

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0009.JPG[/img]

[img1333]http://www.bryerton.com/misc/v2rocket/IMG_0010.JPG[/img]

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0011.JPG[/img]

[img1000]http://www.bryerton.com/misc/v2rocket/IMG_0012.JPG[/img]

[img999]http://www.bryerton.com/misc/v2rocket/IMG_0013.JPG[/img]

[img999]http://www.bryerton.com/misc/v2rocket/IMG_0014.JPG[/img]

[img999]http://www.bryerton.com/misc/v2rocket/IMG_0015.JPG[/img]

[M Fowler]

Rob that amp is sweet can't wait to get started on mine. It looks really small on top of that great bunch of amps you got stacked there.

I;m going with the cut control because I use it on my amps that have it and really don't find much use for a mid pot. Must be my defective ears or tinnitus.

[RJ Guitars]

Hey guys,

Almost caught up on sending out the V-2 kits so I have a little time to amp tweak and tell you about it...

When I played my Les Paul through this amp I found I could push it into distortion pretty easily so I decided to reduce the gain a bit and see how it acted then. This was a bit more and earlier breakup than I got with the stratocaster that I initially dialed the amp in with... no big surprise here.

My first attempt to reduce "the amount of" and "early onset of" distortion was to install a Phase Inverter Gain or "PIG Control" as named by my buddy Zippy. This is one of the master volume controls out of the Trainwreck pages. By inserting a 500K trim pot in place of R9 and using it as a voltage divider with one leg going to ground I was able to dial down the signal going into the phase inverter. This worked like a nice master volume but didn't change the early breakup I was seeing with the Les Paul. So I figured the distortion was in the preamp part of the circuit... real Rocket science?

So plan B - I increased the value of the cathode resistor (R5) in the 2nd gain stage from 1.5K to 3.3K and viola - it really cleaned things up. Has me wondering if I need a knob somewhere to make this yet another variable I can tweak to taste at any given moment... So right now, maybe it's a bit too clean but has me thinking that this might be a sensitive tweak to be added (or not) to a Rocket circuit.

I may go for a 2.2K resistor there and maybe play with the value of the cathode resistor (R3) on that first gain stage as well.

Remember, I have thus far done nothing to optimize the circuit for use with this little 6112 preamp tube. The Rev 1.2 schematic is still using the 12AX7 optimized values for the cathode resistors.

So there is a tweak to think about that will give you the option of dialing in the amp for a high gain humbucker pickup.

Now if you like gain, the 6112 does a great job but I like the cleaner version and then add the option of using a pedal... these amps are pedal friendly like all the other iterations of the Rocket I've messed with.

rj

[RJ Guitars]

By the way - excellent build documentation by Rob Breyerton... the guy is an amp building machine!

[RJ Guitars]

Hey guys,

I've had a few inquiries about getting some cabinets in a different color of Tolex. I've always kinda liked black for myself and I'm not sure what other colors might be popular. I think the cabinet guy will build them out of whatever.... Does anybody have a good grasp of the best choices for alternative colors?

Thanks,

rj

[mclmk8d]

I've always liked medium to dark forest green, navy blue, royal blue, red.

[M Fowler]

WHAT Now you say we can order custom colors

Black was just fine rj.

[RJ Guitars]

WHAT Now you say we can order custom colors

Black was just fine rj.

As Henry Ford put it long ago - you can get it any color you want as long as you want it in Black!

I asked for a quote for the next batch to include some red ones... we'll see what that adds to the bottom line.

rj

[UR12]

I have been doing a lot of different colors for people requesting different color tolexes. I think I have done the most in either black, red, Red/black. Seafoam green is popular along with the dark marshall green. I have also had requests and did amps in orange, purple, white and camofladge. I am just getting ready to do another request in black / red boa snakeskin. So good luck figuring out what people will want They are all over the map. It isn't too bad if you're doing the cabs yourself but if you have to have them built and covered I would stick with one or two colors. On the other hand, people like being able to choose any color they want. Just my 2 cents

[RJ Guitars]

Hey guys,

I have been working with the sub-miniature tubes for a while now and my fondness for them is not really growing. However, my ability to work with them has improved a bit.

Funny thing about Macro photos, they show stuff that an old set of eyes didn't really see. I decided to share these photos anyway because they might be helpful to others headed down this same road. My eyes suck so bad that I worked most of this using my reading glasses and a bench top magnifying glass. I actually can see the results better in the photo than I did as I prepped the leads.

I worked through the prototype builds just kinda looking at things and then bending leads on the fly. When I was done it was clear I needed to think about this aspect of things and get some sort of a uniform idea on prepping the tubes for insertion into the circuit board or tube sockets. I knew that too much bending would cause work hardening of the lead and I'd break one off if I messed around too long. The primary goal in prepping these is to get them to the right width for insertion and also to keep the profile low so that they don't stick way up out of the chassis. This trick is to make short quick bends without kinking the wire.

I limited myself to only one bend in any given spot and lived with the look of the results even if everything wasn't visually perfect. I did all this with my little needle nose pliers and it seems that unless somebody is going into mass production a proper fixture is waste of effort. I can see that I need a little set of round nose pliers to smooth things up and not scar up the leads.

These are NOS tubes from way back and as you can see these particular 5902 tubes have tarnished leads from sitting around in non ideal storage conditions for 40 years. That made them a good candidate for figuring out how I wanted to prep the leads for insertion into a socket or directly onto a circuit board. I cleaned the crud off the leads as I worked and it seemed to come off easy and solder flowed and wet to everything nicely.

I put these tubes into 8 pin IC sockets since I had the IC socket receivers already installed in one of my demo amps. I don't care much for the IC socket option but I wanted to work through the process just to see if it could be done well. I also wanted to be able to change out the tubes for other prototype ideas.

I did get better with each tube and I think it will work well. However, this mounting technique will require some sort of tube keeper to really produce a gig friendly amp. The IC sockets don't really grip the tube carrier and it's real easy to pull the tube out with just the slightest touch.

enjoy,

rj

[Structo]

I wonder if you could find a high heat grommet to fit in the tube holes in the chassis?
So that they fit the tube rather tightly.
That would help hold the tube in the socket and cushion the tube from vibrations as well.

[RJ Guitars]

I have been doing a lot of different colors for people requesting different color tolexes. I think I have done the most in either black, red, Red/black. Seafoam green is popular along with the dark marshall green. I have also had requests and did amps in orange, purple, white and camofladge. I am just getting ready to do another request in black / red boa snakeskin. So good luck figuring out what people will want They are all over the map. It isn't too bad if you're doing the cabs yourself but if you have to have them built and covered I would stick with one or two colors. On the other hand, people like being able to choose any color they want. Just my 2 cents

Thanks Dana - I'll certainly only add one color option at a time and then only if it doesn't add too much to the complexity of things. I am really trying to keep this as a platform for us to develop and perfect ideas while still making it something that you can gig with.

I don't make my own cabinets and spare time has become my most precious commodity, so its up to the Tolex guy whether or not we'll add couple color options.

If color options adds appeal to the users that would be cool but my favorite visual part of these amps is the raised eyebrows and puzzled looks when folks look into the back of these things and see those little tubes.

rj