Choke on Rocket

[Markusv]

Hi Folks

I just built myself a "rocket" 15 watt from spare parts
I had a Nordmende Radio PT and a Triode electronics OT for a Bandmaster
PT is 240-0-240
The thing sounds killer!
I put a "clean" switch in. Basically it lifts the 2nd cathode bypass cap and simultaneously inserts a 150 K resistor from the 220K to ground just before the PI.
Did this because I have a buddy who builds resonators and he is looking for an amp that stays cleaner longer for his resonator with a sc pickup.

Question: I put a 1K 25 watt resistor where the choke would have been
Am I missing any audible effect, or is the choke simply there for filtering. The amp is quiet as a mouse

Markus V

[passfan]

A choke in a power supply can do a couple of things. Helping to keep the voltage constant is what I think it does in the rocket. A poor mans regulation if you will, for the preamp filtering. I've built them with and without to no ill effect. Up around 4 or 5 oclock (max volume) you should get a great Malcom Young crunch.

[RJ Guitars]

... I've built them with and without to no ill effect...

I seem to recall that Paul Ruby said something very similar. I have always been skeptical that I needed it in the circuit but the Rocket amps sound so cool that I didn't want to mess with the formula.

Markus - I would love to see some images and hear some clips.

thanks,

rj

[Markusv]

Passfan & RJ

Thanks for the replies
Your responses seem to confirm my suspicions that a choke is a matter of tradition- that was the way it was done and people don't want to mess with something that works.
I have amps with chokes and without. I don't see a specific tonal or "feel" benefit


RJ

I have no recording ability but I can send you some pics
I don't think this build is something I want to display publicly though. It is very messy.
Old re-used board
Re-used pots
Re-used parts etc
Lots of holes on a re-used chassis

I can send you a pm

Markus V

[RJ Guitars]

...I don't think this build is something I want to display publicly though. It is very messy.
Old re-used board
Re-used pots
Re-used parts etc
Lots of holes on a re-used chassis...

Somehow it always works out that way. It seems that is part of the magic formula!

[Reeltarded]

Come on! None of us will laugh. Have you seen my twisted solder blobs?

It is part of the magic!

[Markusv]

http://i1004.photobucket.com/albums/af1 ... t15009.jpg
http://i1004.photobucket.com/albums/af1 ... t15008.jpg
http://i1004.photobucket.com/albums/af1 ... t15006.jpg
http://i1004.photobucket.com/albums/af1 ... t15001.jpg
http://i1004.photobucket.com/albums/af1 ... t15011.jpg

I can't believe I'm posting this- I'm so ashamed
It's incredibly messy looking.

Here is some background.
The Chassis played host to probably 5 amps now including a 15 watt Liverpool, a Traynor YGM2, an 18 Watt with Tremolo and this Rocket.
Except for about 5 resistors and as many caps, everything is salvaged from other projects
Pots, jacks, board chassis, Power supply, OT etc.
The Chassis was hand-bent before I owned a metal brake. That was maybe 4 years ago

The cab was an experiment with the idea of a combo with a partition between speaker and chassis. Its way over sized for the 12 inch speaker but honestly I have never heard anything sound as good. The dovetail jointed Pine cab is about the size of a Bassman combo. Little on the cumbersome side and not what you would associate with a 15 watter.

The amp itself is just incredible to my ears. I used a PPIMV and the Hot/clean switch. I currently also have a switchable feedback (presence) on a pot at the back.
Gonna take it out likely

The clean setting has the lifted 2nd stage cathode bypass and the grounded 150K resistor at the 220K to the PI
The Hot setting is the opposite.
This amp is way more aggressive that I thought it would be and I like it!!

Thanks folks

Questions, comments and loud laughter welcome

Markus V

[greekie]

Oh will you quit being ashamed right now!

You've built an amp. An amp that works. It could be tidier, yes, but who cares when the music's playing? Only you. And guess who the guy who builds the next amp will be? You!

Great job. This is a fantastic journey.

[Markusv]

Thanks Greekie

Well the irony is that I have built numerous amps for other people
But when you pick stuff and leftovers from your bench and you start with holes drilled that weren't really optimized for the current build, then the aesthetics go south.
Not to mention the bent leads on components, the scraps of wire used etc
Oh well - as you say it sounds good and I 'm playing music.

I have certainly sorted out a few technical questions I had about the Rocket. So my next one will be the real deal with the right transformers etc>

Markus

[LeftyStrat]

Oh will you quit being ashamed right now!

You've built an amp. An amp that works. It could be tidier, yes, but who cares when the music's playing? Only you. And guess who the guy who builds the next amp will be? You!

Great job. This is a fantastic journey.

+1

If you built something that sounds great and you love it, you've succeeded. I have built really neat amps I hated, and some really ugly Frankenstein amps that were transformed a hundred times before I loved them.

I don't think Dumble or Fischer ever had the neatness of say a Komet. I'm pretty sure the owners of Dr. D's or Ken's amps don't really care, as long as they are reliable.

At the end of the day, it's still about how it sounds.

[rooster]

I just looked at photo #5, a gut shot, and it doesn't look all that bad really. Clean it up someday if you're inclined. For now though, take a break and pat yourself on the back, it sounds like it's working great. I get that thing where you have some parts and the urge, that's maybe the best place to hang out.


As to that choke, Jennings kind of screwed up on the 59 model with the 100 ohm resistors, corrected them in the 60 model - but in either case didn't use a choke. I personally think your 1K is way too big. I would cut that value in half or down to 250 ohms typically, but yes, I would use one along with the 100 ohm resistors on the screens.

[Markusv]

Thanks Rooster

With a 250 R resistor instead of the 1K- What could I expect in terms of behavior?
Stiffer maybe?
I had a smallish ohm resistor in that position in a previous amp and I remember it getting very hot but the whole amp was a different animal so I can't compare

Markus

[Cliff Schecht]

Yeah I've built much uglier. I actually just ripped my last ugly build apart (a 5C3 clone) for the PT and OT. I'm going to finagle some sort of Deluxe together with a swiss cheese chassis that has been a few amps in the past. Unfortunately all of the preamp socket holes are way too close to the pots (typical of point to point builds) and I think will need to be covered up with something. It's going to be ugly but I'm sure it'll sound great. With enough practice and a clever headshell/faceplate you can hide most any mistakes .

FWIW I try to make everything I build now look as tidy as possible but it's hard sometimes when you recycle chassis like I do. The last two Fender builds I've done were in some really nice aluminum chassis that were someones previous projects (three of them, the third will soon be a 100W Marshall). All of them had a hole for an Eimac socket and a massive hole for a fan to blow. I covered this up on the first amp I built but my Vibroverb build has about a 4.5" hole right under the preamp section! I might cover it in plexiglass someday, it looks pretty neat actually!

[rooster]

250 would be louder and tighter. The thing to be aware of is that various power tubes have an screen/plate relationship that effects their behavior. With some tubes (6L6 by design) you can hit this soft spot by going up in value, say 2K, or likewise having no choke at all. Take a look at the tweed 5E5-A Super for a learning experience. A very soft amp that actually has more voltage on the screens than the plates.

[NickC]

..........

I can't believe I'm posting this- I'm so ashamed
It's incredibly messy looking.

.............

It doesn't look bad to my eyes! You built a working tube guitar amp, and they are ALL beautiful.