New DSM project...XTC preamp..PCB!!

[dschwartz]

HI all!!!
i just finished this board layout for a fet emu of the famous BOGNER ECSTASY..
I Based the design on the good ol´ DR. Boogie thread, that resulted in Gauss Markov´s layout..REALLY GREAT!!!!

I made it the same way as the double shot preamp, with graphic editing software and the schematic in the hands..
I have´nt build it yet, so Help yourselves and build the first one!!!!! and please tell me about how it worked out!!!!

this is the schematic wich i based the project

http://www.mif.pg.gda.pl/homepages/tom/files/xtcod.gif

board and layout:

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i left out the gain switch...

[bancika]

I've heard that schematic you have contains some errors compared to the original xtc.
Another though, mesa mark IIc+ would be cool to try to build with JFETs, there's schematic traced out of real circuit on slo clone forum (and probably elsewhere)...
Cheers

[dschwartz]

hmmm.,..there may be some different values than the original. but for what i see in the schem, it will work

if anyone knows the differences please post ´em

[John Lyons]

Looks interesting David!
Can you post a larger layout. It's heard to see some of the values and components.
The layout may be a tricky one to get quiet and free of oscillation.
If you could post a larger layout image we can see what's going on.

Thanks

John

[dschwartz]

here´s a larger image:

[John Lyons]

I missed this one david....
The layout looks pretty good. I need to look at it closer though to be sure.
Just make sure to put the Level pot on the other side of the tone pots and not next to the gain pot as this may cause oscillation.

The input stages should stay away from the output stages, left to right. If you could mount the board so the gain pot is routed as far away from the tone and level pots that would be best. Like the DB layout.

John

[bancika]

who's david?

[drewl]

Wouldn't it be easier to just build the amp?
I know it would be for me.....more practical too.

[bancika]

yeah but it's cheaper. For a fraction of money and effort you need for tube amp you build emulator.
I know, it won't be the same. I'm for amp solution, too. But for folks who don't want to involve with high voltages, spend much money on this, etc. it's a nice thing to try...

[DWBH]

Hey bancika, when will we have "our" new DIY layout creator? I'm starving here 

[drewl]

yeah but it's cheaper. For a fraction of money and effort you need for tube amp you build emulator.
I know, it won't be the same. I'm for amp solution, too. But for folks who don't want to involve with high voltages, spend much money on this, etc. it's a nice thing to try...

It's great work there, and I'm all for building stuff!
But how close to the real thing is it going to sound with FETS as opposed to tubes?
Will it sound like an XTC or a Crate, or Valvestate?
I've built tube preamps which although involve high volages are pretty cheap to build and sound like the real thing....well, cause they are.
I guess I'm just an amp guy!
But that's great work there!

[dschwartz]

i have a tube amp, and i made a dual rectifier tube preamp (the double shot ) ..both sound really good!!
but i mostly play with my dual rectal (modified dr boogie) cause i like its feel and sound better than the tube stuff..
it´s a matter of taste... and economics and simpler building..

tubes will never be replaced 100%, but for my taste, fet distortions are the way to go if you want a simple, great sounding, hassle free, low maintenance, cheap and versatile distortion..

and other thingy...fet distortions are the best way to learn about how preamps and audio circuits work..i could never build the double shot without understanding sound filtering and amplifying that are so clear and accesible with this kind of circuit..

i just would like you to give them a chance..i´ll bet you´d be surprise with the results!!!!

pd:_ john, i´m Daniel....don´t worry , i get the "David " stuff very often...

[dschwartz]

I missed this one david....
The layout looks pretty good. I need to look at it closer though to be sure.
Just make sure to put the Level pot on the other side of the tone pots and not next to the gain pot as this may cause oscillation.

The input stages should stay away from the output stages, left to right. If you could mount the board so the gain pot is routed as far away from the tone and level pots that would be best. Like the DB layout.

John

i did the layout considering those things..
if you look close, the input is far from the output, and the gain pot uses wires, so you can place it wherever you want..on my boogies i put the gain knob next to the bass knob, and the output at the other end of the tonestack..i just placed it like that on the layout because....i don´t know..it turn that way out 

[bancika]

Hey bancika, when will we have "our" new DIY layout creator? I'm starving here 

check out sticky thread, I just released new alpha version...

[nico21]

hello!
I made this project with the Dr boogey's PCB and layout
So i change the values and some component's legs are "flying" so that now i have the xtc preamp in a box, based on the above schematic

Some minor differences:
1st cathode resistor is 1k instead of 820
no caps across gain pots
no structure switch, only 2.7k with 2.2µ
5k mid pot instead of 2.5k

So i plug it in the return of my H&K tour reverb (input impedance of 47k) and it's sounds very very goog i like it, lots of fun to play with
Can't compare the sound with a real xtc, never played one!
all trimmers are set around 4.5v, the third one is 5.8v

the second stage trimmer is around 20k so i change the cap from 1n to 4,7n
the third stage trimmer is around 50k so i change the cap from 470p to 1n

anyone could tell me if it's a good idea to change the values of these previous capacitors to match the trimmers?
because i play a little with the value of the 2nd stage capacitor and it seems to have an audible effect only at 10n!

Thx for your help!
Nicolas

PS: sorry for my bad english

[dschwartz]

it´s really not necessary to change those cap values since they work with trimmers.
even if you use 100k or 20k trimmers, the sweetspot would be at the same spot (around 15k, depending on the fet)..

those caps cut really high frequencies to avoid hi freq oscillations, so you have to put a big cap to hear the difference (some treble cut), just put any cap over there as long as they are in the same order of magnitude (1n, 2n, 3.3n, etc not more than 6.8n)find the value you like most..it will make little or no effect to the voicing or gain character, but it could help to lower the hiss or noise.

could you pleas, please post a clip?

[nico21]

for the clip i can only record it with a digital camera, and then extract the audio part ...i think about it

in the real xtc, 100k and 1n for second plate give about 1.6 khz, and in the sim 20k and 1n give about 8khz
so that's why i tought to change from 1n to about 5n, to get the same frequency cut as in the real one

Am i wrong? is there something i missed or that i don't understand enough?

[bamera]

Daniel, thanks for putting up your project. Hopefully this thread will evolve with interesting discussions. 

[GonzoFonts]

Does anyone have a schematic of the pedal?

Thanks.

GF

[CLAAS]

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