LukeFRC

[quote name='Daquifsta' post='779926' date='Mar 19 2010, 03:55 PM']Tell me more about this clone - your own interpretation of the design or a DIY kit or something?

I really like the sounds from the various youtube clips for this pedal, and I enjoy waggling a soldering iron about :-)[/quote]


Well I wanted an ampeg style OD sound, and was going to make a 'flipster' project... following links took me to look at other alternatives and the SFT really stood out as as something doing the same thing really well. Anyway the freestompboxes.org forum has a load of folk who have backwards engineered one of them [url="http://freestompboxes.org/viewtopic.php?f=7&t=7368&hilit=sft"]http://freestompboxes.org/viewtopic.php?f=...8&hilit=sft[/url] there's a number of different PCB layouts (the one on the last page looks like the best) and a vero-board layout (page 4 ?) which I made. Dead easy build, it was my first attempt at making something. There are different pictures of the insides if you want to guess at cap types.
My one isn't housed yet but my initial response would be
1 ) really really good SVT type drive sounds - better than the SVT model on the bass pod i had before
2 ) brilliant touch sensitivity. Other 'overdrive' pedals I have had/used actually seem more like some kinda warm fuzz pedels- your tone is just covered with this sound. This is better, if you set it up so, when you dig in it overdrives, when you don't it doesn't. Again comparing this to the bass pod model both did this yet the SFT is way more responsive to technique in your right hand, and sounds more natural as a response.
3) the Eq is amazing. Parametric Eq's have their place, as do graphic sliders. My amp has 4 different bands of parrallel Eq, the church amp has 7 knobs of series Eq.... this has two.... and sounds so so... musical. If victor wooton double thumbing are your thing, or funk slap, this may not work out for you, but for fingerstyle....... heaven..

I'm pretty happy as you can see!

i built my own SFT clone- its amazing. I've no idea what the others are but a +1 for a SFT (or approximation of one)

Have you ever looked inside a 1950's or '60 radio or stereo? Compare that to a modern (not high end) one.
The old one will tend to look over engineered, use big old components (valves and old style resistors and caps) and be made using old techniques like point to point wiring.

New stuff will have modern components mounted on a PCB by a machine. Probably in china. Hardwear can be a wee bit flimsier, using cheaper metals. Or conversely better metals for the job.
Now there is a whole argument as to which is better technically. But the old one has more romance.

Point being production techniques have changed. The availability of different types of wood and the way these woods care dried, the finishing on a guitar and so on.
So I don't understand the whole 'they're the same' arguement. Bar finding a massive bargin I would never really want to dive into the vintage fender market personally but I can understand folk who do.

i had the body of one. wieghes a tonne and is some superhard plywood.

C= 0.21
B= 6.43
E = 5.33

which looks wrong to me!

EDIT 2: arrggh I give up. starting again with another layout that makes more sense and is a wee bit different but at least i know someone else has got it working!


EDIT 3: one day later and half a dismantled effect..... ahh the transistor to ground resistor being 390,000 ohms not 390 ohms may have something to do with that!

ok those voltages may be useless, ill try get better ones for each pin relative to input...

umm help... made a big muff pi, everything looks like it should be working but it's not....

l[url="http://www.aronnelson.com/gallery/main.php/v/Gila_Crisis/Big_Muff/BMP.gif.html?g2_imageViewsIndex=1"]ayout: [/url]

possible problem with the transistors? using an audio probe nothing seems to get through the first transistor! any help would be great!

Transistor....BC239C

battery 8.25v
c - b = 6.12v
b - e = 0.47v
c - e = 5.86v

[quote name='Dubs' post='775367' date='Mar 15 2010, 04:16 PM']I'd say the best value 2nd bass you could get would have been about 12 months ago when you could pick up a Warwick Streamer Stage I in good condition for between £600 - £650 off of here and eBay. A bass that retails at almost £2k for silly money.[/quote]

+1..... or my 1991 natural one for £400...... The best thing about it being it's a cracking bass and i would have bought this particular one at 3 times the price, not that I have 3 times the price but you get what I mean.
I've seen some quite nice stingrays sold on here for low prices too

[quote name='escholl' post='773501' date='Mar 13 2010, 11:21 AM']Try changing the 1uF cap going out of the first gain stage into the effect part of the circuit to something smaller, 0.22uF or 0.33uF perhaps. This won't give you more treble, but it will put less bass through the effect circuitry, and might clean up the sound a bit. Try the 0.33uF to start, if you feel up to it.

I've also just had a thought -- check the connections around the IC1a, make sure those components are all right on the board and there's no loose connections. Most people seem to complain the pedal has too much of a bass roll-off, as you've not found that to be the case but instead have found not enough treble, if may be that the pre-emphasis filtering network is not working correctly for some reason. This is just speculation though.

What I usually do in situations like this is, find all the mods you can, and try the ones you like the sound of. Then try some new ones, and just play about a bit -- it helps here if you know what you're doing though [/quote]

It did have too much bass roll off. The 0.1 cap at the start sorted that though. If I get a chance to go to the shop on monday I may stick a 0.33uF. To be honest it sounds good so I'm not too bothered.



As another note, If anyone is using the breadboard big muff plan that was posted up here a few pages back it has some interesting differences (mistakes?) in the bottom right section. Look up a schematic and swap around two sets of resistors and caps.


EDIT: tried it all again, and yes will try that 0.33uF cap....or maybe reduce the 0.1 cap at the start to 0.066 or something.
EDIT 2: Put the 0.033 back in. Not as bassy but sounds fine. I think I may just leave it! Want to get these all finished!

1) should be in 'for sale section'
2) it's an amp not a bass so should be in amp section
3) hello, looks nice amp!

I think nickzinner of the yeah yeah yeah's has a pretty cool looking rig with the guitar signal being split between a fender twin de-vile and a ampeg bass amp. massive sounding.

If i wanted the 'guitar amp' sound I would split my signal and feed it into a bass pod or something. then from that into some poweramp and a small cab. If you manage to blow up a POD it would be cheaper than a valve guitar amp

so stuck a 100k resistor in the output op-amp and the volumes seem to match.
I'm really not sure what I've made here, the 0.1 cap on the input makes a massive massive difference.
It doesn't seem to have a massive amount of the top end shimmeryness that chorus seems to have, it's a lot deeper. Close to sounding like one of those lesley rotating speaker, yet with more stuff going on. I'm going to play with it and see what I think.

[url="http://www.diystompboxes.com/smfforum/index.php?topic=67908.0"]This thread is somone one else with the same problem making it work for bass and addressing it differently...[/url]


EDIT: wee play again. I do like it. As it has more bottom end it comes accross as more subtle. It doesn't 'shimmer' much and doesn't sound great on a guitar but it sounds good. Live and in the mix I'm think it possibly is a good sound.
I wonder... heres an idea.... is the chorus bit of the circuit very good with low end? If I put in a cap smaller that the 1uF in the feed from the op amp to the chorus bit of the circuit would it let give me a more trebly wet sound with the better bottom end i already have? Prob wont do it mind just interested.

Radansey: that A/B box is older than me!


EDIT No. 2: here's some mod's on a small clone [url="http://moosapotamus.net/THINGS/wavy.htm"]http://moosapotamus.net/THINGS/wavy.htm[/url]

[quote name='escholl' post='772303' date='Mar 11 2010, 11:52 PM']A larger input cap shouldn't affect the sound in a detrimental way, it will simply lower the cutoff frequency of the high pass filter that is effectively created by that cap -- in fact, as the pedal was designed for guitar, 0.1 uF is probably a good value to put in for bass, instead of the original. It is a good choice.

You've got the right idea that the 33k resistor affects the volume, however it works in the opposite way. So, if you wanted a louder volume, increase the value of that resistor. This is why when the connection to that resistor was broken, effectively raising the resistance very high, the gain was increased and the distortion occurred. By calculating a ratio of the input resistor (in this case 10k) to the feedback resistor (33k) the gain of the op-amp stage can be calculated, in this case the gain is roughly 3. If you want to increase it, you could try a 39k resistor in place of the 33k, for a gain of roughly 4, or a 47k resistor, for a gain of about 5. You could also try, say, a 47k pot in series with a 10k resistor, which would give you a variable output level.

In case you are wondering, the 6.8k resistor in series with the 0.01 uF cap is there to prevent that gain stage from amplifying too much high frequency noise above the usual audio spectrum, so that can stay as it is and does not need to be adjusted, although it could be if you felt like playing about with the high frequency response.

Also, if you are curious and did want a wet/dry mod, stick a 47k linear pot in place of where the 22k and 20k resistors are next to points A and D on the schematic. Not really needed though, I don't think.[/quote]

thanks!
Stuck a 47k resistor in, may make it smaller later as still a wee volume drop but it works a treat. I like the 0.1uF cap, makes it very bassey.

Lovely bass... off topic on the Grammar police logo, surely you don't require the full stops before the 'to' and the T of the 'to' should be capitalised as a new sentance?

Yay! It works!



I tested it with a 0.015 on the input last night. It clearly wasn't letting the bass through. So I've stuck a 0.1 on the input rather than the 0.033. It probably isnt the same sound as the original but it works fine for me, makes sure there's a bottom end to it (I know idealy you would have some kind of wet dry mod but I havnt got space on the enclosure for another pentometer!

There is a fair volume drop though... would I be right in guessing from what you said that if the 33k resistor in the output op amp was less than 33k it would be louder?

no! it works i think! too late to try out loud now but it seems to work!!!!

[quote name='escholl' post='771133' date='Mar 10 2010, 11:56 PM']The 4558 is indeed two separate op-amps. Check that pin 5 is definitely at 4.5 volts, and check that there isn't any sort of broken track or dry joint on the 33k feedback resistor (the one just above the 6.8k in the diagram). If everything is in order, but the output of pin 7 is still not what you expect, pull the IC out of it's little socket and then connect your audio probe to pin 6 of the socket. If the input is exactly what you expect to hear on the output, just quieter, then you will need to replace the IC.

Don't worry, it's not that uncommon a fault -- I've done it myself by accident. In case for some reason you can't find the 4558, you can also use an NE5532 in it's place, which is technically a better op amp. Either will work however and they are both cheap (under a quid from Maplin).

If, however, the input at pin 6 with the chip removed is not what you'd expect to hear on the output, then your problem lies elsewhere, and the IC is simply amplifying the problem. From what you've said however, that would seem not to be the case.[/quote]


thanks so much for the reply!

voltage at 5 is 4.5v, 33k resistor is fine. I can't take it out to test (no signal will get through to the second op-amp without the first! but putting the probe on the input on the right hand side and the signal was there.
Checking the 33k resistor and there seems to be a gap on the icb there so no signal gets to either the 33k or .01 cap. Easily fixed.
So ill go buy a new chip tomorrow! Thanks folks

[quote name='escholl' post='771133' date='Mar 10 2010, 11:56 PM']The 4558 is indeed two separate op-amps. Check that pin 5 is definitely at 4.5 volts, and check that there isn't any sort of broken track or dry joint on the 33k feedback resistor (the one just above the 6.8k in the diagram). If everything is in order, but the output of pin 7 is still not what you expect, pull the IC out of it's little socket and then connect your audio probe to pin 6 of the socket. If the input is exactly what you expect to hear on the output, just quieter, then you will need to replace the IC.

Don't worry, it's not that uncommon a fault -- I've done it myself by accident. In case for some reason you can't find the 4558, you can also use an NE5532 in it's place, which is technically a better op amp. Either will work however and they are both cheap (under a quid from Maplin).

If, however, the input at pin 6 with the chip removed is not what you'd expect to hear on the output, then your problem lies elsewhere, and the IC is simply amplifying the problem. From what you've said however, that would seem not to be the case.[/quote]


thanks so much for the reply!

voltage at 5 is 4.5v, 33k resistor is fine. I can't take it out to test (no signal will get through to the second op-amp without the first! but putting the probe on the input on the right hand side and the signal was there.
Checking the 33k resistor and there seems to be a gap on the icb there so no signal gets to either the 33k or .01 cap. Easily fixed.
So ill go buy a new chip tomorrow! Thanks folks

only just saw your reply!

Yes it is brilliant. I've not put it in an enclosure yet but playing with it outside i have to say the Eq controls are brilliant.
What it is AMAZING at, and what I've always missed in most other pedals I've had is that it's very touch sensitive, can do lovely warm motown style sounds too.

sorry to bother you all again...
tracked down the problem I think. The 4558 chip seems to be funny.
On the [url="http://www.tonepad.com/getFile.asp?id=97"]schematic[/url] it works as two seperate units (op amps???) IC1a seems to be fine, everything doing what it should.
Ground is ok, as is the voltage into this chip. On the IC1b part however we seem to have a wierd fuzzy loudness. input 6 is fine, the signal from the bass, the output 7 however comes out all distorted. IS there a reason it would do this or have i broken the IC somehow?

sorry to bother you all again...
tracked down the problem I think. The 4558 chip seems to be funny.
On the [url="http://www.tonepad.com/getFile.asp?id=97"]schematic[/url] it works as two seperate units (op amps???) IC1a seems to be fine, everything doing what it should.
Ground is ok, as is the voltage into this chip. On the IC1b part however we seem to have a wierd fuzzy loudness. input 6 is fine, the signal from the bass, the output 7 however comes out all distorted. IS there a reason it would do this or have i broken the IC somehow?

I got my H&K Q600 bass amp for under the trade price because it had been sitting around for a few years at the bass merchant and I think mike wanted rid of it.
This is a good thing.

so wired together in hopefully properly... and I have a pedal that amplifies and does a nice fuzz sound! with a phasing thing in the background. not what i was aiming for but progress!



EDIT:


ARRRGGHHH!!!! Whats gone wrong this time? the chorus is there in the background its just something is turning it into a fuzz pedal. Im guessing either the 4558 chip or one of the transistors??

I get to wear the bass chat dunces hat for a bit though

[quote name='escholl' post='770154' date='Mar 10 2010, 10:50 AM']0.033 nF, or 33 pF, seems awfully small for a cap in this position in the circuit -- are you sure that is the right value? If it was 0.033 uF, which is 33 nF, that would make more sense given the typical input impedance and bandwidth requirements of these types of input stages.[/quote]



yes, i think you're right! I was just following my plans which were confsing me, I've just looked up the baja version on freestompbox and it's way clearer! Oddly I had ordered the right pieces, just thought i had them wrong.... lets start again.
The good news is that I have now worked out enough of what each bit is doing that I pinpointed the 2 problems!