tag:blogger.com,1999:blog-6847048658257278783.post5777021025346307058..comments2024-03-29T01:36:12.851+00:00Comments on Guitar FX Layouts: MXR Custom Badass '78 DistortionIvIarkhttp://www.blogger.com/profile/08416945174853142251noreply@blogger.comBlogger43125tag:blogger.com,1999:blog-6847048658257278783.post-66342291896526611142015-04-13T16:39:47.804+01:002015-04-13T16:39:47.804+01:00Hola a todos
me interesa saber si funciona 100% d...Hola a todos<br /><br />me interesa saber si funciona 100% de una y sin problemas..... <br /><br />Hello everyone<br /><br />I want to know if 100 % of one and runs smoothly .....BRAVEWOLFhttps://www.blogger.com/profile/14856398178799198311noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-79579720649019076872015-01-02T04:51:12.836+00:002015-01-02T04:51:12.836+00:00Amateur question: I have the M78 and I love how it...Amateur question: I have the M78 and I love how it sounds with the CRUNCH button engaged. I'm not very good at reading schematics but I'd just like to know what clipping diodes are engaged when the CRUNCH is on. I assumed it was just 2 LEDs, but the schematics look more complicated. Is it a combination? Thanks...Jeff Bigghttps://www.blogger.com/profile/15012976322426220486noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-10724017393784396782014-05-02T13:13:13.681+01:002014-05-02T13:13:13.681+01:00Hi,
In case this has any impact: I see mirosol'...Hi,<br />In case this has any impact: I see mirosol's layout has the capacitor that comes before the last transistor as 1µF, and the output capacitor as 47nF, when it's the other way around in John Kalls' layout (and in the latest schematics posted at FSB).<br />Hope this helps...Anonymoushttps://www.blogger.com/profile/02360194601012631862noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-87227124696437503342014-01-24T10:55:52.990+00:002014-01-24T10:55:52.990+00:00The voltages being correct doesn't mean it wil...The voltages being correct doesn't mean it will work. Everything else could be perfect but one bad connection on the output wire and you won't get anything out of it. <br /><br />The MPSA14's are darlingtons and so much higher gain than the MPSA18's. That could be an issue, I'm sure darlingtons were selected for a reason. I wouldn't expect it to be silent with 18's though even if they aren't high enough gain. But it is certainly a difference from the intended parts and so something worth trying.IvIarkhttps://www.blogger.com/profile/08416945174853142251noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-69230577844852067732014-01-24T10:33:17.854+00:002014-01-24T10:33:17.854+00:00Just thinking of this: "If all the voltages o...Just thinking of this: "If all the voltages on the IC pins are correct, then the circuit itself should be correct"<br />Maybe reason why I don't get any sound out of it could be due to the transistors choose? I use three MPSA18, and the IC is the TL072... :/aeroemihttps://www.blogger.com/profile/01047192029017794580noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-46273033103879625432014-01-24T00:00:34.679+00:002014-01-24T00:00:34.679+00:00Ok so... I've changed 3 electrolitic caps, the...Ok so... I've changed 3 electrolitic caps, the IC and one led that were all damaged... Now I have all the correct voltages around the IC, but still no sound come out...<br />uff....<br />Seems that I have to use a sound probe... I know how to build it, but not how to use it properly...aeroemihttps://www.blogger.com/profile/01047192029017794580noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-37410251770454395062014-01-23T22:13:49.615+00:002014-01-23T22:13:49.615+00:00Yes you could have damaged any polarised component...Yes you could have damaged any polarised components so the electrolytics could potentially be damaged. Plus I don't know whether the IC will have liked 9V on pin 4 or if that could have caused any internal damage. <br /><br />So I think you may have a few things to swap and re-measure. If you're still not getting any sound through then you're going to have to look at sorting yourself out with an DIY audio probe so you can identify where the signal is dropping.IvIarkhttps://www.blogger.com/profile/08416945174853142251noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-38592158908350427762014-01-23T21:16:48.850+00:002014-01-23T21:16:48.850+00:00Mmmm, things get worse... I've crosse 9v wire ...Mmmm, things get worse... I've crosse 9v wire with the ground one... I stopped when I became to smell something strange... and I realized that the IC warmed up very much... Now, if I return to the previous configuration, the voltages that I measure around the IC pins are all 0, except for the 4 and 8 (which still remain 9 and 0)....<br />I tried different transistor, but nothing changes... What else could have been broken? an electrolitic capacitor? aeroemihttps://www.blogger.com/profile/01047192029017794580noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-24866612799122638462014-01-23T18:35:35.904+00:002014-01-23T18:35:35.904+00:00Your ground and 9V wires must be crossed (maybe po...Your ground and 9V wires must be crossed (maybe positive centre pin power supply instead of negative?). As you say, pin 4 should be 0V, pin 8 should be 9V so you've got a build error somewhere that you're going to need to identify.IvIarkhttps://www.blogger.com/profile/08416945174853142251noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-70549608763653801922014-01-23T18:31:17.343+00:002014-01-23T18:31:17.343+00:00:( it doesn't work... just a lot of noise... t...:( it doesn't work... just a lot of noise... the pots seem to work properly anyway; I measured the voltages around the IC, and I found these:<br /><br />pin1 = 4.5V<br />pin2= 4.5V<br />pin3= 4.5V<br />pin4 = 9V<br />pin5 = 4.5V<br />pin6 = 4.5V<br />pin7 = 4.5V<br />pin8 = 0V<br /><br />It seem there's something wrong with pin 4 and 8, which have one the voltage of the other...<br /><br />The transistors I used are MPSA18, and I used 68nF instead of 72 nF, 39nF instead of 38nF, and 880nF instead of 890nF (putting 4 capacitors of 220nF each, in parallel)...<br /><br />:/ could anyone help me?aeroemihttps://www.blogger.com/profile/01047192029017794580noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-89610666770518227842014-01-23T12:34:42.542+00:002014-01-23T12:34:42.542+00:00Thank you Ivlark, so (if I'm not wrong) I have...Thank you Ivlark, so (if I'm not wrong) I have to:<br />a) connect the central lug of the SPDT switch to lug n.1 of output potentiometer AND to "switch 2"<br />b) connect one of the (other two) lugs of the SPDT to "switch 1", and leave the other lug empty<br /><br />Is this correct?<br />Thanks!aeroemihttps://www.blogger.com/profile/01047192029017794580noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-37883521434626750072014-01-23T00:20:36.423+00:002014-01-23T00:20:36.423+00:00That's the ground rail so all it means is that...That's the ground rail so all it means is that both SW2 and Output 1 need to be grounded. Take a wire from the board to SW2 and then another wire daisy chained out of SW2 to Output 1 lug. That's it.IvIarkhttps://www.blogger.com/profile/08416945174853142251noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-15606790801416588432014-01-22T23:54:46.254+00:002014-01-22T23:54:46.254+00:00Hi all! Sorry for the (noob) question... How do I ...Hi all! Sorry for the (noob) question... How do I connect sw2 to output1 ? I mean, I'm using a SPDT switch... How should I do the connections?... please help me!<br />thanksaeroemihttps://www.blogger.com/profile/01047192029017794580noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-666221975646134802013-10-06T17:14:53.204+01:002013-10-06T17:14:53.204+01:00Well, it's been quite a while since I had the ...Well, it's been quite a while since I had the original one, but as much as I can remember it is not too far from it. It actually is a nice ballsy distortion, the clipping options add some variety to the sound. I did not box it, but only because currently the Crunch Box is my favourite and don't need another higher (for me at least) distortion at this moment.drdFXhttps://www.blogger.com/profile/05100895565160403133noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-11617824473861030572013-10-06T13:49:25.666+01:002013-10-06T13:49:25.666+01:00Fixed. So the layout should now be ok for anyone t...Fixed. So the layout should now be ok for anyone to build.mirosolhttps://www.blogger.com/profile/02400327798106357876noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-50808905943570493832013-10-05T17:36:48.840+01:002013-10-05T17:36:48.840+01:00Guys, how different is this from the Super Badass ...Guys, how different is this from the Super Badass Distortion, in terms of tone? Also, any leads for the schematic for that?<br />Thanks.<br />J.Jishnu Dasguptahttps://www.blogger.com/profile/02561213193417793572noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-7514278676182522312013-10-01T10:14:59.288+01:002013-10-01T10:14:59.288+01:00Forgot. I'll replace it once i get to my deskt...Forgot. I'll replace it once i get to my desktop.<br />+mmirosolhttps://www.blogger.com/profile/02400327798106357876noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-53481935570289494952013-10-01T07:14:01.987+01:002013-10-01T07:14:01.987+01:00Mirosol, just realized that you updated the layout...Mirosol, just realized that you updated the layout, thanks for that. However the emitter resistor of the upper left transistor is still 220Ohm, the schematic at FSB says 22Ohm there. I changed it too on mine and indeed it makes a difference, so I'd suggest to change this in your layout too if you have a little time.drdFXhttps://www.blogger.com/profile/05100895565160403133noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-83167964057434646652013-09-27T20:29:29.209+01:002013-09-27T20:29:29.209+01:00oh, and I also went with a C250K for the distortio...oh, and I also went with a C250K for the distortion pot on mine for even more gain.johnkhttps://www.blogger.com/profile/00643996045674470081noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-28104238017298661212013-09-27T20:28:24.383+01:002013-09-27T20:28:24.383+01:00I didn't try it with a 47n, but since I use my...I didn't try it with a 47n, but since I use my pedals mostly with a bass, I just went with the stock 1u. I also ended up with a 220p for the 12n and a 150p for the 290njohnkhttps://www.blogger.com/profile/00643996045674470081noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-87279598263595744772013-09-27T20:08:46.328+01:002013-09-27T20:08:46.328+01:00John, on mine I left the output cap as on miro'...John, on mine I left the output cap as on miro's layout. Does this make a big difference, did you try that? I'm quite happy with how it sounds now, so if the difference is not too much, then I won't bother desoldering it... Thanks!drdFXhttps://www.blogger.com/profile/05100895565160403133noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-79109362646178903732013-09-27T10:15:24.929+01:002013-09-27T10:15:24.929+01:00I just built it and it sounds great. you can verif...I just built it and it sounds great. you can verify it if you change a couple of things. reverse 1 & 3 on the tone and distortion pots, change the 47n output cap to a 1u, and change both the 12n and 290 caps to 100p's. the original pedal also uses a TLC2262 op amp and that's what i'm using in mine.<br /><br />here's my 'corrected' layout:<br /><br />http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/MXRCB78/MXR-Custom-Badass-78-Distortion.png<br /><br />johnkhttps://www.blogger.com/profile/00643996045674470081noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-45851127664001315732013-09-24T07:42:59.676+01:002013-09-24T07:42:59.676+01:00Oh, and if you want to change the second transisto...Oh, and if you want to change the second transistor to a FET, then you need to remove the 470k resistor and the 12nF (or actually 100pF in the revised layout) going from the base to the collector, the FET does not need that.drdFXhttps://www.blogger.com/profile/05100895565160403133noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-41197960373245972522013-09-24T07:40:29.927+01:002013-09-24T07:40:29.927+01:00I might be wrong, but the first and last transisto...I might be wrong, but the first and last transistors probably don't make much difference, as they are only used as buffers. The second transistor is already doing some amplification, so I'd start with that. If you want drastic changes I'd try something with low hfe, 2n2222 for example.<br /><br />I think it would be possible to convert this stage to a FET stage too, but then you would need to change the 10k resistor from collector to +9V to a 100k trimmer, change the 22Ohm resistor to something between 1k5-15k and possibly add a cap in paralel to this resistor with the value between 1uF-47uF (though on this layout it is only possibly in an ugly way, by crossing over other components, or in the same holes as the resistor). With the trimmer then you could bias the drain voltage of the FET to 4.5V.<br /><br />You can also experiment with the clipping section, different diodes or diode arrangements can change the texture of the distortion quite a bit. I'm thinking to remove the switch, and only use some asymmetric arrangement, probably a Ge and a LED or a Ge and two Si in series.<br /><br />You could play with the 4k7 resistor and the 890nF capacitor in series. These form a high-pass filter, if you increase the capacitor value you will get more bass content, lowering the resistor will give you more gain in the opamp stage, but also you will filter out more bass (if you keep the 890nF the same).<br /><br />Optionally you could play with the tone stack and the 72nF cap after the opamp to change the tonality, but I think it is quite useable as it is, so I wouldn't change that.<br /><br />If I was to redesign the whoel circuit, I'd probably try to use the second opamp in the IC better, at this moment it is only a buffer. I'd either try to use it as a first gain stage or use the first opamp for gain stage and the second for an active tone control. But this can't be done on this vero layout.drdFXhttps://www.blogger.com/profile/05100895565160403133noreply@blogger.comtag:blogger.com,1999:blog-6847048658257278783.post-24212947548514773032013-09-23T17:21:14.197+01:002013-09-23T17:21:14.197+01:00Thanks Csaba.
I used a 250k pot for distortion ...Thanks Csaba. <br /><br />I used a 250k pot for distortion and it seems to work well, in case anyone was wondering. <br /><br />I ordered some MPSA14 transistors just for this pedal, but also tried several others. While the MPSA14s sound decent, I tried BC550Cs and that's what I'm sticking with. LOTS of balls.<br /><br />I'd say that built this way it's a pretty damn good distortion pedal, but there are several others on here that are just better. This will probably end up as a "give away" pedal. All the same, if I didn't have better I would definitely use this one.<br /><br />I'm wondering now what kind of bizarre transistor swap could make this a bit more unique. Any ideas? Bohemian Hhttps://www.blogger.com/profile/09155964862358263643noreply@blogger.com