Wrecks other than Francesca

[JamesHealey]

I've got this .pdf with various versions of the trainwreck schematic from schematicheaven.com, and the variations tends to be how the mid pot is connected up and the 150k and 2n2 couping cap and grid leak.

Variations are as follows:

56k 1n
56k 1n parallel with 1n ceramic
150k 2n2 polyester
150k 1n parallel with 1n ceramic

are these confirmed differences or speculation? they seem to be fairly consistant do these wrecks, going on Glens Orphan Annie and Francesca.. although I've seen Ginger inside and that is another story. Malou looks to be quite different but she's a Liverpool also.

what kinds of circuits do people here favour and have tried?

[gearhead]

The first Trainwreck that had widely available, highly detailed photographs was Francesca. That was in late 05, early 06. That broke the code on not only the circuit and components, but especially the physical layout and lead dress. Crucial stuff.

For the Schematic Heavean (and other sites), note the date on those schematics; 00-01-ish. As far as I recall, those were based on best effort observations/interpretations and hand drawings.

[dartanion]

I like 68k and 4.7nF poly or other film cap. Going too big on the resistor and it loses focus with too much bass. It's just flavors, so find a combo that's tasty to you.

[doctord02]

Yep the wreck pdf thats at schematic heaven and blue guitar is pre Franchesca best guess and hazy recollections. Of the schematics in that file, the A1a is the closest to correct.

Stick with the schematics here in the reference section, either the Franchesca one or the Kelly one. They are the real deal. Both drawn by forum members here with actual hands-on knowledge of the amps themselves.

[Richie]

Don't know how you all keep overlooking this one..

http://ampgarage.com/forum/download/file.php?id=1892

Its legit..uses a few different type caps,and most was measured from being on the bench.

[funkmeblue]

thanks richie, don't think I ever seen that one.

[sliberty]

Just compared Trudy to Kelly, and the differences are small. 500K volume instead of 1M. Parallel caps after stage 2. And a couple of small differences in teh power supply.

How did Trudy sound? Was there a noticable difference to other Express amps we've heard?

[M Fowler]

Richie,

I have never seen that one and read the old posts three times. Thanks.

[Structo]

I was looking at that schematic.

I'm seeing the two diode rectifiers coming off of the bottom tap there but no caps on it to smooth the ripple.

On the Kelly schematic it has extensive filtering on the bias.

[gearhead]

Don't know how you all keep overlooking this one..

http://ampgarage.com/forum/download/file.php?id=1892

Its legit..uses a few different type caps,and most was measured from being on the bench.

Don't know how I missed that puppy? That needs to go in the files section!

Bombay did the schematic; assume he either had access to or owned Trudy?

Original thread: http://ampgarage.com/forum/viewtopic.ph ... y&start=90

[sliberty]

I was looking at that schematic.

I'm seeing the two diode rectifiers coming off of the bottom tap there but no caps on it to smooth the ripple.

On the Kelly schematic it has extensive filtering on the bias.

The biggest difference in the power supply is the placement of the standby switch. Kelly has it after the main filters, Trudy has it before the main filters.

Unrelated, I also noticed that Trudy doesn't include the power tube protection diodes.

[Richie]

Brian Wallace should have the credit on the Trudy. as you can see it has his marstran in the upper corner..

[JamesHealey]

I like 68k and 4.7nF poly or other film cap. Going too big on the resistor and it loses focus with too much bass. It's just flavors, so find a combo that's tasty to you.

68k 4n7 gives roughly the same corner frequency as 150k 2n2, just reduced gain, probably why you're liking that combo.

482.5Hz vs 498.2Hz

Very similar

[funkmeblue]

the diodes are there, see the note about both plates. I would bet some of his earlier amps had some more experimenting going on until he got it down to a science.

[gearhead]

Brian Wallace should have the credit on the Trudy. as you can see it has his marstran in the upper corner..

Thanks for the point out. Am pretty sure that Bombay=Brian Wallace.