What would YOU build in a...

[Le Basseur]

...screwed-up Carvin X-60A chassis?
(I'm not sure where'd belong such a post so I put it in the "design" section)
So I got this Carvin on the bench a while ago:cosmetics 9/10,fair British Vintage 12-inch driver BUT...the previous owner thought that the combo should be MUCH better if the output stage shall be modified from tube to SS.The guy that made this "upgrade" (TV-repairman,zero-knowledge in tube amps and guitar playing whatsoever) ripped the OPT and thrashed it,then literally butchered the PCB and installed a proprietary SK-based output stage outside the chassis.To keep things short,the SS output burned out and the actual owner wants the amp back to it's "original state" wich I'm afraid it's impossible due to the above-mentioned destroyed PCB (to the "point of no return" degree) and missing components.
My offer was to re-build completely the amp (a new PCB that follows just the physical config of the original one because of the three noval and two octal tubes,the pots' placement and rear connectors).I have some PTs,chokes and OPTs rescued from some other amps so the iron isn't a problem...well,this is where you should chime in:what config to choose?
The owner didn't say nothing about his preferences but it happens that I know his playing style and sound...70's R&R.
The input stage/tonestack config should be anything two-channel(clean/dist) that uses a pair of 12AX7's.Also,the PI and output sections might be the straightest possible,either EL34s or 6L6s (as I said,I have several OPTs).
Bottom line:this post might sound silly for some of you,no doubt.I could build anything (well,almost...)but the truth is that I'm torned apart between so many good designs and I'd want to rescue this amp as elegantly as possible.Also,because of the PCB's (fairy large) size,I'd like to get it working within a rather small number of experimentations.
This job is a "cost-no-object" one because the owner deserves it fully (he kindly let my jazz trio to rehearse in a gorgeous establishment with no restrictions and fees so this amp job is the least I can do for him).
Thank you for any idea and comment (even the "use your own brain dude and don't waste my time" ones are welcome! ).
Regards,

[Steve Conner]

Trainwreck clone!

[stokes]

I dont see the "ruined" PCB as a problem,why not just go point to point?If your preamp is still intact,just remove all the crap the butcher put in and re-build the output point to point.If you are set on a total gut and rebuild,I would still suggest the point to point and forego the PCB's altogether.The Trainwreck Steve mentioned is nice,I just finished a build that I used a T-Wreck preamp into a 2X6L6GC single ended out put head,matched up with a 15" Celestion cab in combo with a Leslie 2 speed cab with a 12" EV 12L,best sounding amp I have built so far.I havent had the opportunity to use a real Trainwreck,but this clone is incredible.I used one of the Express schems for the preamp.

[Le Basseur]

Thanks guys for your fast replies!

Trainwreck clone!

...well,Steve,I was afraid that someone'll spell the "TW" word...
Thanks for your undoubtful option!

I dont see the "ruined" PCB as a problem,why not just go point to point?If your preamp is still intact,just remove all the crap the butcher put in and re-build the output point to point.

Yeah Stokes,this was my primary intention...until I saw the inside's chassis.
I'm really sorry that right now I can't take some pics of that PCB.I could bet that very few of Ampagers had seen something similar.There's not only the output stage that has been decimated (nearly all components missing,except the octal sockets wich are burned out by the means of heavy use and abuse of a powerful soldering iron) but the pre sections had been butchered as well...a handful of strange and illogical "hand wirings",missing components and some weird values added where you'd least expect,alot of copper traces cutted out or burned...insanity all over.
Honestly,I just can't imagine HOW this amp worked at all!?!

If you are set on a total gut and rebuild,I would still suggest the point to point and forego the PCB's altogether.

Yes,I HAVE to be set on a total rebuilt.I wasn't very specific in my first post but PtP was the first thing I thought about.

The Trainwreck Steve mentioned is nice,I just finished a build that I used a T-Wreck preamp into a 2X6L6GC single ended out put head,matched up with a 15" Celestion cab in combo with a Leslie 2 speed cab with a 12" EV12L,best sounding amp I have built so far.

Thanks for confirming the TW clone's quality!(Unfortunately,I never heard an original TW nor a clone but I understand that should be THE way to go).
I'll have to stick to a PP output for a couple of reasons.On the other hand,the 12" EV12L you mentioned is a story of it's own....maybe the best-sounding 12" I ever heard (I have one in my guitar player's Acoustic 164 combo).

I used one of the Express schems for the preamp.

Yes,I saw several versions of this schemo.If you don't mind...wich one did you use and for what reasons (pros and cons)?
Thank you!
Regards,

[Jelle]

I hope you don't mind me asking...


Stokes,

How did you do the Phase inverter section with the SE amp? Or did you go from the .1 cap into the 6L6 grid?

Thanks,

Jelle

[stokes]

Like I said I only used the preamp from a "Trainwreck" schem,if it is indeed a TW schem.As you probably know Ken Fisher was pretty tight lipped about his schems,so I have only found schems of other peoples "renditions" of TW's.I found a bunch that I printed up,they were described as "Based on Ken Fishers Design" or "Inspired by designs by Ken F".There were about 8 or so of them marked "Trainwreck Express Version A1",A2 A3 etc.I had a Hammond 25watt SE OT,so I first wired up the output and power section and experimented with different preamps with it.I settled on the A7 version,and used the first 3 1/2 12AX7 stages from the TW schem feeding a paralleled 12AT7 driving two NOS RCA Black plate 6L6GC's.When compared to the Fender type preamps I used, the TW pre really opened it up and gave it a great touch response,like it came alive and could "breath",that my next build is going to be a copy of the complete TW schem.By the way the SE amp has a 5V4 rectifier instead of the SS rect.So it isnt really a TW,if the schem is actually even close to one,but that preamp really got my attention.

[Jelle]

Stokes,

Thanks for the info! Much appreciated.

Jelle

[bob p]

i would have to agree with Stokes that the magic of the TW circuit is in its preamp. i would go one step farther and say that there is NOTHING interesting going on in the output section of a trainwreck express.

I'm also familiar with Steve's schematics for amps that were "inspired by" the Express circuit. my opinion on that is that they're pretty accurate, but I don't want to put words in anyone's mouth. time having passed the way it has, maybe Steve could chime in and tell us exactly what he meant by phrasing things that way.

to take as much speculation out of this subject as possible, take a peek at this in the spirit of Fair Use:

[stokes]

When I found the site with the schems I have,unfortunately I didnt print them all,but the three I have are slightly different than the one you posted here,bob,but it is different in the same way the 3 I have differ from each other.Also,having never seen a real TW myself,it is pretty much impossible to tell how close or not they are.When I first saw them,I thought they were only slightly different than,say a Fender on the face of it,but once I actually assembled one of the circuits,I was pretty impressed with the tone and response.And since the amp I built has the SE output and the tube rect,we can be sure what I have isnt close to a real TW,so my curiosity now has the better of me so as I said,my next venture is to try the schematic as it is with the PP out,etc.I gotta agree tho, that the power section doesnt look like anything special.There is alot of "hype" about the real TW's having specially selected components and Ken Fishers special mojo etc.,and that even if you have an accurate schem,you cant duplicate one.I dont see myself ever spending the kind of money it would take to buy a real TW just to find out.If I can find where I got the schems I have I'll post it so you guys can take a look for yourself,but right now I cant remember where they came from.

[Satamax]

Stokes, talking bout theses ones???

http://www.freeinfosociety.com/elect...eckexpress.pdf

[bob p]

max, that those are inded the drawings i was referring to by our friend Steve.

Stokes, the fact that "authentic" TW schems bear subtle differences from one another that are all similar goes with the lore that KF intentionally put subtle differences in the amps so that he would know, by the appearance of schematics, which TW owner allowed their amp to be "inspected." i'm not sure how true the lore is -- some of this could really just be a parts is parts phenomenon, and since KF is gone we'll never know. suffice it to say that the snippet i've posted is from a real Express, and its one of two documented variations that were observed in real specimens.

i agree with Steve's assessment that the basic topology of the TW circuit is nothing more than a Fender Princeton Reverb that has a jumper in place of one of the high value resistors (reverb IIRC). one signficant difference i've noticed between steve's schematics and the preamp snippet that i've posted is the value of some of the support structures in the gain stages. those can impart a pretty significant difference in the tone of the amp, especially when the first gain stage gets the signal juiced up before it hits the tonestack.

[stokes]

Max,those are the schems. I have had them so long I cant remember where they came from,I dont recall seeing that text before,but the schems do match the ones I have.bob,you refered to "steves schematics" in both your replies here,is there a link to some other TW schems,that are different from the ones posted in this thread?

[bob p]

One of the best references for wreckoid schematics is to follow the course of Steve Ahola's Blues Express project. those schems are available at BlueGuitar.org, and I think you already have them. you might want to go there and make sure that you have all the files.

the only other online source that i remember is the Yahoo Trainwreck group. its been closed for quite some time, as the person who started the group moved it to a privately owned portal. i don't remember where the Yahoo Group actually went, but IIRC there is a hyperlink at the Yahoo Group site that takes you to the new site.

[bob p]

http://launch.groups.yahoo.com/group/twreck/

[Le Basseur]

The link http://launch.groups.yahoo.com/group/twreck/ seems unoperational at this moment...what I got was "Sorry, this group is available to members ONLY.You are not allowed to access this group."...and no registering option whatsoever.
Maybe you meant this?
http://ampgarage.com/forum/
Regards,