Attempted Simplification of the Express - Non Traditional

[RJ Guitars]

I've been interested in developing a way to consistently build an Express without the traditional pain of getting every wire in exactly the right place, tweaking and cursing. While on a long airplane flight I designed my own Express based layout and circuit board. I had been trading ideas back and forth and sharing designs with Mark Fowler for a couple years on this idea but time had not allowed me to get anything done. After I got to me destination overseas I ordered four prototype boards and when I returned, they were here waiting for me.

First - a digression about some of the recycled hardware I am using. I had this idea a while back that I would revisit the Trainwreck layout and move those transformers apart... seemed like a good idea at the time but it hummed like a Bumble Bee. I fought with it for a while but finally gave up and decided to just admit it wasn't going to work. I pulled the output tranny and head-phoned it around and found a half dozen places where the hum was minimal and one spot where it was zero (at the other end of the chassis). Funny, one of those minimal places was the traditional Trainwreck location. So I commenced to cutting out the top of the chassis and re-purposing it for yet another new idea. I made up a new top plate and fit it onto the chassis and began the efforts to create a simplified version...

I found three willing partners to build a prototype with my board and chassis and once that hardware arrives in their hands (this coming week for most of them) you may see some activity on this effort. I'll keep you up to date as I work on this project but I expect the other guys will be done before me... I am a bit too busy for anything but sharing the idea right now. Depending on the results, I'll make improvements on the boards and chassis and make more of them available.

Stay tuned, this could turn out to be entertaining...

rj

[guitarsnguns04]

Pretty cool concept rj....I'll keep my eyes on this ....curious to what the results will be....if you need another willing builder let me know. I'd be interested in giving it a go myself.

[Bob S]

Heresy...
I am very interested in this.
I would really like to build an Express or Liverpool without having to dink with them too much when initial assembly is complete.
When they are right they sound wonderful.
Getting there is a real PIA.
Good Luck with your worthwhile endeavors RJ & associates.

[guitarsnguns04]

Bobs...sounds like a natural progression that once the express is solved the Liverpool layout will probably next in this experiment....just a guess though. It would be nice to be able to build them consistently with a revised layout that keeps all the tone intact and reduces all the tweak time to get them quiet and stable. I'll be staying in tune with this thread.

[RJ Guitars]

I'll throw up a couple more photos that will add some perspective to this effort... some folks already had this part figured out. I'll say up front that I really don't know how well it is going to work but I wanted to develop a layout and circuit board that will add consistency to the results. The hope is that the results will ultimately be good not just consistent. That's why I asked for some help in putting these first prototypes together because I anticpate that it will be a challenge to conquer the beast. If we are successful the we will preserve the Express character and performance while reducing the build time, etc..

For those that are interested I was sorta thinking that we'd test the waters with the first four prototypes that are out there and then offer up more of them in a Gen-2 version. The bare bones package (Chassis, Transformers, and circuit board) is about $300 and that shouldn't change with the nest iteration. As you can see I've set these up with Edcor transformers and a standard sized Trainwreck chassis. I wanted to use non-traditional components to avoid the high dollar mojo tax since we've already broken most of the trainwreck rules anyway.

The front panel is standard Trainwreck specifications and I've added the IEC socket to the back but otherwise it's similar to the familiar Wreck controls.

Thanks for the interest.

rj

[UR12]

Here is one that does work. Like you, I have had this project on hold for about 4 years. The prototype you see in the pic works flawlessly and uses the traditional chassis layout. One recomendation I would give you is to go ahead and include the pots mounted on the PCB so that you eliminate wires runs to the pots. Don't want to side track your thread,. Just thought you might like a little input. I don't have any plans to offer this in a kit but it will probably become our production Express in the near future.

[Jana]

RJ,

In the first photo, is that orange thing on the chassis a new style of transformer? Does it give the push/pull, killer bee sounds for metal sounding amps? What's the bias current on something like that?

[dorrisant]

Is the bright switch disconnected, Dana?

[UR12]

Is the bright switch disconnected, Dana?

Yes, when this pic was taken it was.

[RJ Guitars]

RJ,

In the first photo, is that orange thing on the chassis a new style of transformer? Does it give the push/pull, killer bee sounds for metal sounding amps? What's the bias current on something like that?

That is an add on effects gadget... definitely push pull and produces the sorta sound that really makes you feel better when it stops. Specifically it produces the effect of throwing away a bad chassis design and acting you you have a new technique for chassis fabrication... Good news is that I only had 24 of these made. Look for various iterations on the replacement top chassis technique.

[dorrisant]

Dana,
Did you build more than one, and if so do they sound the same? Just curious... Express builds are hard to make sound alike. With the pots mounted to the pcb, it seems you will repeat the harmonic content due to that wiring or the lack of it.

[RJ Guitars]

Thanks Dana UR12 for sharing your inside look on your PCB Express efforts - It looks like you have preserved a lot of the Express layout. I agree that focus on the "pots" is at the forefront in this effort. I find that the volume pot and associated "brite" electronics are very sensitive in the Express circuit and the Presence control can also be at the root of many Wreck issues.

I used this link as a starting guide for development of the board - http://www.geofex.com/article_folders/p ... -to-pt.htm There are some tradeoffs that I can see in simplifying and minimizing amp lead lengths and it will be interesting to see what is required to untangle the good from the bad on a PCB layout.

thanks again,

rj

[UR12]

Dana,
Did you build more than one, and if so do they sound the same? Just curious... Express builds are hard to make sound alike. With the pots mounted to the pcb, it seems you will repeat the harmonic content due to that wiring or the lack of it.

I have built many many Lil Devil's that are all PCB and basically a mini version of the Express. If you take the time to measure and select the right components you can get amps that are consistent and very close in tone and feel. That is the key to getting a good sounding amp. You can duplicate the same thing time and time again. It's funny you should ask this question. We did some blind tests and I had Richie play a couple of Express amps I had completed. It was really blind as Richie had no idea I have even built an amp using PCbs He played both amps and remarked he liked one better than the other. I turned the chassis over and showed him the guts and he was speechless. He had picked the PCB amp. There are only a couple different reasons to go to the trouble to build using the PCBs. The most important to me was to cut down on the time it takes to construct the amp. If you cut down the labor costs involved then you can sell the amp cheaper and build them faster while getting the same quality each time. The other side of the coin is that it makes it easier to construct and get it right for a novice which is what I think RJ is going for.

Thanks Dana UR12 for sharing your inside look on your PCB Express efforts - It looks like you have preserved a lot of the Express layout. I agree that focus on the "pots" is at the forefront in this effort. I find that the volume pot and associated "brite" electronics are very sensitive in the Express circuit and the Presence control can also be at the root of many Wreck issues.

thanks again,

rj

No problem, Yea my goal was to produce a design that allowed you to use the same chassis as the original layout. That way the same boards could be used to produce either a Liverpool or an Express and the only changes were the power tube boards. The power supply board was configured for either cathode bias or fixed bias just by populating it with the right components and the preamp board was the same just different values used for stuff like the PI.

I did change the original layout of the "Stack-o-caps" or cap cans by moving the filter caps closer to the nodes on the board that they were actually filtering. There were design changes that drifted away from the original layout but only when it made sense to from a production point of view. That pic was of the prototype and I have moved on to cables and molex connectors to simplify the wiring even more between the boards and tube sockets. I also wanted to make sure all tubes were mounted to the chasis and not the PCB. The power tubes sockets on the amp in the pic are bolted to the chassis and the board is actually mounted on the sockets using standoffs. So the sockets are supporting the board and not the other way round. I had spec'ed out board mounted power and Standby switches after the prototype was finished. (Which is the reason the Brite switch isn't connected in the pic). If done correctly you can get a great sounding amp.

[M Fowler]

It's great seeing a couple of PCB designs and knowing Dana's works so well.

We will be putting the rj PCB Express to test soon.

I always had interest in JoeBob's Hoffman style board as well not sure if anyone ever built one?

Mark

[Richie]

I'll vouch for what Dana said. It was fun playing it, and sounded great. I was really suprised.
I figured others might feel the way i did. And the only way would be to play them,and then you could make your own judgment on them.