Catalinbread - SFT  [traced]

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Diamond
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Post by Diamond »

Can anyone please post correct transistor voltages if they have any? I built Mike's vero layout and it works, meaning that all knobbies function like they should. The only problem is that the gain sounds a bit 'misbiassed'. The sustain is pretty low and it sounds a bit scratchy.

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Post by Nocentelli »

I'm a single cap short of finishing this - C2 is a polarised electrolytic in the schematic, but I've only got an unpolarised polybox in that value. Is the value or the polarised nature likely to be more important in this circuit do you think? I could sub in a 0.1uF or 1uF electro instead.

It's here in the schematic -
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SFT_snippet.PNG
SFT_snippet.PNG (2.16 KiB) Viewed 4006 times
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Post by mysticwhiskey »

Nocentelli wrote:I'm a single cap short of finishing this - C2 is a polarised electrolytic in the schematic, but I've only got an unpolarised polybox in that value. Is the value or the polarised nature likely to be more important in this circuit do you think? I could sub in a 0.1uF or 1uF electro instead.

It's here in the schematic -
Using a non-polar cap instead of a polarised (of the same value) will work with no problems. Just check that its voltage rating is the same or higher as the original one, and you're good to go.

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bigstomp
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Post by bigstomp »

Here is a pic of my SFT build....sounds good at 9v....sounds way better at 18.....check it out...
Image

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Post by cropec »

Hello everyone

I wonder if anyone can get the "motown bass tone"() using a copy of SFT?

I build one using madbean's layout . It's sound ok with guitar and higher bass guitar notes, used as a distortion. However when I try to clean it up it starts sounding rather horrible.

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Post by Crumbchildz »

Bigstomp, that's just gorgeous! Well done, sir! :applause:
Loud's a tone, right?

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Post by Lawnchair »

Yea, great looking box.

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Post by bigstomp »

cropec wrote:Hello everyone

I wonder if anyone can get the "motown bass tone"() using a copy of SFT?

I build one using madbean's layout . It's sound ok with guitar and higher bass guitar notes, used as a distortion. However when I try to clean it up it starts sounding rather horrible.
The one I built, I gave to the bass player in my band. He plays a vintage style P-Bass with a Lollar, and keeps this pedal on all the time. It really gets that old school sound....he runs it at 18v.....and sets it fairly clean with a touch of grind when you dig in. Really comes to life in a band context. This is just my experience.

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Post by minnow »

Hi Friends,
I have had issues figuring out the "scaling" in order to print the PCB transfer images being shared here.
There's the SFT PCB transfer by gkoerselman, which could be found here: https://www.freestompboxes.org/viewtopic ... 116#p83116

Attached here is the same transfer, only in PDF form, whereby when you want to print, all you have to do is choose Page Scaling > None in the PDF print option.
All credit goes to gkoerselman!!
SFT - gkoerselman.pdf
SFT
(78.86 KiB) Downloaded 391 times

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martn
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Post by martn »

Hi, i got a problem with mine, build with Mikes Veroboard Layout (V1.0)

Problem: no sound :(

Using the voltage doubler, here ist what i got:

Q1:
q: 0
s:1.15
d: 9.23

Q2:
q: 7.9
s: 9.23
d:16.56

Q3:
q: 9.23
s: 9.41
d: 16.58

Q4:
q: 0
s: 0.8
d: 9.13

Q5:
q: 7.8
s: 9.13
d: 16.56

Q6:
q: 0.65
s: 1.8
d: 9.27

Q7:
q: 7.87
s: 9.27
d: 16.58

Q8:
q: 9.26
s: 9.46
d: 16.57

Moreover, i had no 470nF (replaced by two 220nF) and no 4.7uF (replaced by two 2.2uF), but this should not affekt the funktion, if im right..

I'll try to make some pictures tomorrow.

Thanks to all who could help ;)

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Post by azrael »

Man! I etched an older version of Madbean's Faultline layout some time ago, and I just got to it. However, the one on his site isn't the same one as the one I etched. Does anyone have the old layout information? I have no idea what goes where now, hahah. :slap:

Don't feel right about just discarding a board, so if I can save this one, I'd prefer to. Thanks!

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Post by madbean »

azrael wrote:Man! I etched an older version of Madbean's Faultline layout some time ago, and I just got to it. However, the one on his site isn't the same one as the one I etched. Does anyone have the old layout information? I have no idea what goes where now, hahah. :slap:

Don't feel right about just discarding a board, so if I can save this one, I'd prefer to. Thanks!
This is the "old" version one:
Faulltline_ver1_OLD.pdf

Note that it says "revised 3.01.10" That's an important revision because the initial version was missing a trace due to an error in Eagle. IIRC, it was Q3 that was missing a trace on either the gate or source. So, take note of your etched board and compare the traces on yours to the ones on the layout in this one. You may have to use a small wire jumper, if so.

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Post by azrael »

wee! that's the exact one, everything checks out, gonna get to soldering! thanks madbean, especially for the quick response. :D

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Post by Brainbender »

Thanks to Madbean for his layout! :hug:
I've made one yesterday and it sounds killer!!! :twisted:

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madbean
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Post by madbean »

One note: 18v is much preferred for this one. It's a pretty dramatic difference.

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Post by Brainbender »

That's good to know! I'll try it out, thanks again! :applause:

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Post by cropec »

I've got some problems with my build. It's cutting of low freq. (kinda annoying especially for bass guitar...)

I'm trying to debug it using multimeter +generator and SPICE simulation : Sinusoidal signal 130 Hz(for E string) Vrms -240mV

Measured Vrms on G Q1 and G Q3 is very similiar to simulated one. However, Vrms on S Q3 is much higher than simulated one AND it's almost the same as G Q3 Vrms.

I measured Vdc on every pin of every tran. and they're similiar to those posted by martn on previous page, so I assume they're ok.(Only diffrence -I use 9V power supply so I divided Martn's voltages by 2).


If anyone have had problem like this? And if somebody could measure Vrms on Q3 at his build? Thx in advance

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Post by MicMicMan »

Hey

Here's an answer of a request from the catalinbread formula 5 thread.
Barcode wrote:Be sure to post a schem of your tweaked schem MicMicMan, I'm sure a lot of us would rather go that route and solder one cap versus multiple resistors. Seems like the noise should be greatly reduced from using the one vref...
Here is the modified schematic I did from the SFT. It's supposed to be less prone to thermic noise.
I'm building it right now... I produced a PCB but it's very, very tight as I want it to fit a 1590B enclosure, but it's not perfect yet (it's my first PCB layout using kicad) ; pads are not large enough also, soldering won't be easy... so I'd rather assemble the model and test it before submittting it.

The schematic and tweaks are pretty self-explanatory I guess... I suppressed that weird 220k resistor between the first mu-amp stage, then increased the source resistor for gain matching. There was a quick adjustment to the capacitor then, for adjusting the bass frequency response of that first stage. I put a common vref instead of divider for every mu-amp stage.
According to my LTSpice simulations, the frequency response, gain settings and phase responses are almost exactly the same as the original catalinbread SFT (let's say, the difference in gain is always less than 0.5 dB). Waveforms also look the same.

In my opinion, the only real difference between the original schemo and this one might lie in the voltage drop caused by that 47 ohms resistor in series with the power source, because the power consuption of that voltage divider and the mu-amp stages might differ from the original schematic. I didn't check this though, feel free to test it.
Attachments
Based upon the original SFT schematic, but with little adjustements (a bit less noisy ?)
Based upon the original SFT schematic, but with little adjustements (a bit less noisy ?)
modified sft.jpg (60.9 KiB) Viewed 4257 times

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Post by RnFR »

looks cool. but is R4 supposed to be 68K, or maybe 6K8?
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Post by MicMicMan »

On the original circuit, R4 is 22k, but then, the mu-amp circuit is followed by a 220k resistor to ground, before the Q3 buffer. The effect of that resistor is to lower the gain of that particular stage. I tried removing this resistor, then increasing R4, and I came up with a 68k value for R4. Then, it made me adopt a .68uF value instead of the original .47uF value for C2, so the modified mu-amp stage matches almost exactly the same gain and frequency response than the original one. I didn't notice any change in the few waveshapes I displayed at several input voltages and frequencies (anyway, it seems to distort very late when powered with 18v dc). At least, that's according to my simulations. Groundtruth may show different conclusions...

Here, in the attached file, are the .asc files I used, with LTSpice. Just in case, I also provide the library I used for potentiometers.

My parameters for the 2N5457 trannies are :

Code: Select all

*2N5457 MCE 7-10-95
*25V  25mA  250 ohm Dep-Mode pkg:TO-92 3,1,2
.MODEL J2N5457 NJF(VTO=-1.8 BETA=0.00135 LAMBDA=0.001 RD=35 RS=31.5 
+ CGS=2.25E-12 CGD=6E-12 KF=6.5E-17 AF=0.5 )
I guess I found this following the first link google provided me.

Cheers,

Pierre
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catalinbread sft.rar
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