Tuesday, 22 April 2014

Fulltone Bassdrive Mosfet

And the bass version.  This is based on the guitar version but with the passive changes to match the filters in the bass version.  The diodes seem to have changed often in this, some with symmetrical mosfet/germanium combinations with a 1N34A in both directions and some with asymmetrical as shown here.  Some with more than one 1N4001 (or 4005) or asymmetrical on the silicon side with 2 x 1N4001 and 1 x 1N914.  So I'm just leaving the clipping as per the guitar version, and you can put your favourite combination in there if you choose.

Info about the discontinued original:

Bassists need dirt too! But no one, until now, has given you something that works, with all the full, rich bottom-end that you deserve, damn-it! BTW, many guitarists use and prefer the Bassdrive for Guitar!

The Bass-Drive is a lot like its cousin the Full-Drive2, but voiced with an extra octave of bass coverage... still giving a natural, uncolored FATNESS to your thang.

From just adding a little grind, to replicating a raging SVT, to sounding like Jack Bruce in Cream. (He's got one already!)

THIS WILL DO IT!








Here is another version seen in one schematic and confirmed by John K based on values noted in ones he repaired.  This one based on symmetrical clipping with the mosfets using 2 x 1N4001 in that section.  If you prefer to use the asymmetrical mosfet clipping with a germanium diode shown in the first layout, then just use the V1 layout as a base and change the capacitors to the alternative values mentioned in John's post:

1) 100n input coupling cap is 22n
2) 10p input cap to ground is 51p
3) 51p cap between pins 1 and 2 is 100p
4) 220n at pin 2 is 330n
5) 220n at pin 5 is 68n




36 comments:

  1. Awesome Mark, thanks for this one. Just one question about the layout, what schematic did you use or did you just change the passive components to suit a bass? Cause i was trying to find pictures of the board or a schematic and I found this,

    http://wwww.freestompboxes.org/viewtopic.php?f=1&t=5420&start=60

    which has a few different schematics, and some large high-res images. In the photos it looks like there are 5 or 6 diodes. I was also thinking what about adding to the layout a diode selection switch, so you can have different clipping arrangements?

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    1. That's an example of what I was talking about the clipper choices changing from build to build, it seems Fuller changed his mind a lot about it. The scheme I based it on was by Bernardduur and had a germanium diodes in series with each mosfet. The pics on the page you linked has no germanium diodes that I can see, and instead seems to have 1N4001's in series with each mosfet.

      I'll do a diagram later of all the different diode and mosfet variations that I can find, so people can try other things.

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    2. I've added a couple of additional versions above with clipping variations.

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    3. damn mark that was ridiculously fast. i didn't realize that there were that many different versions of this. i figure that if there are multiple clipping options i like i can just put them on a switch. i just found that thread with all that info, i think there's a V1 board picture at the beginning of the thread, that has another different clipping arrangement. should be a real nice bass od, wonder what he took this from. lol

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    4. I've always liked switches to alter clipping diodes, for something like a TS I'll always include one. It has two good points because as well as the different sounds you can get it also takes the diodes off the board and onto the switch which can help make the layout more compact. But as soon as mosfets are involved that all goes out of the window because of all the connections required which would be horribly untidy to try to solder straight to a switch.

      Having said that, just for the fact that I love extra options like LED clipping, I'd still be tempted to add a switch for the two silicon diodes above the opamp to give a couple of extra options. For a DPDT on/off/on switch like this:

      1---4
      2---5
      3---6

      If you removed D1 and D2 from the board and soldered them between 1 and 4, back to back LEDs between 2 and 5, and maybe back to back germaniums between 3 and 6, with the feed wires also going to 2 and 5, then you would have lots of different tones there. Just make sure the option with the highest forward voltage are between 2 and 5 because they will always be in circuit so you don't want them to have any effect when the 1-4 and 3-6 diodes are selected.

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    5. that's pretty much what i was thinking about doing, but wasn't thinking about the LEDs. that's an awesome idea. the only think is with the LEDs between 2 & 5 they would always be in the circuit, so you really would never get the original sound. but i guess that doesn't matter that much since there are so many variations. i thought this looked like a TS, but wasn't sure, totally see why he had the hid all the mojo with goop.

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    6. If the LEDs are between 2 and 5 then they won't clip when the switch is in the other two positions because the other diodes will clip the signal before the voltage can reach the level where the LEDs clip. Just make sure the diode pair with the highest forward voltage are in the middle position.

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    7. man i feel like a total noob for not realizing that. then you are totally right, that layout for the switch is an incredible ideal. totally going to do that.

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  2. Thanks Mark, this was in my to-do list. I haven't built it yet but I think you have missed some cuts, one under D2 in the third layout, and other between Q1 and Q2 bases in the three layouts.

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    1. It figures with the stupid things I've missed recently, I think I need a break again :o)
      Thanks for the heads up, all changed (and the Fulldrive - oops)

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  3. Just a heads up for anyone building this after Brownpedals comment on the Fulldrive thread. Before you build it, check that the contacts on the CFV switch behaves in the following way before soldering it up. The way it is drawn requires 2 & 3 and 4 & 5 to be made in the centre position. If that isn't the case with the ones you buy and instead 1 & 2 and 5 & 6 are made in the middle position, then swap over the poles so:

    Lug 1 becomes 4
    Lug 2 becomes 5
    Lug 3 becomes 6
    Lug 4 becomes 1
    Lug 5 becomes 2
    Lug 6 becomes 3

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  4. just an FYI. in the bassdrive, the 220n that connects to the 4K7 in the drive circuit should be a 330n, and the 220n that connects to lug 1 of the tone pot and pin 5 of the chip is a 68n.
    i'm building this one right now (V1) & should be able to verify it soon.

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    1. Again he's used a few variations in this one, I've seen the Japanese schematic, but this was one that was traced by Bernardduur and they were definitely the values shown. But when you look at how often he seems to have changed his mind with diodes I suppose it should be no great surprise that the same is true with some of the passives.

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  5. Replies
    1. Awesome! After the Cave dweller debacle I was starting to worry :o)
      What do you think of it?

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    2. I drew up my own vero for one about a year ago and I really dig it, so I built your V1 layout today and it sounds exactly the same. I did replace those two 220n caps that I mentioned in the new one since my first one had those values and I wanted to compare them. I've also repaired a few originals for some friends and they also had the 330n and 68n caps in them.

      here's two pics of my newest one (your layout):

      http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/BassDrive/BassDrive2/BassDrive2-01.jpg

      http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/BassDrive/BassDrive2/BassDrive2-02.jpg

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    3. That looks excellent mate, thanks for the pics and for verifying

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    4. I may as well add a version with the values you mentioned as it's a verified arrangement. Did the one you looked at have a 22n input cap like the one in the Japanese schematic?

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    5. yep, they had a 22n for the input coupling cap, with a 51p to ground (instead of a 10p), and a 100p across the diodes in the clipping stage, so that's how I build mine.

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    6. Cool thanks John, I'll add the layout

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  6. Whew, I just spent a while debugging the version 2 vero. The jumper that goes from the clipping section to pin2 of the opamp should be going to pin one.

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    1. I've just had a look and that doesn't make sense. The Mos/Std Sw2 is already connected to pin 1 of the IC via the Drive 1 > CFV Sw5 and Mos/Std Sw2 > CFV Sw4 links. So in one position of the CFV switch IC pin 1 is connected to the Mos/Std switch and so either the mosfet or standard diode arrangements are already connecting to pin 1. If that link goes to pin 1 too, then both sides of the diode connections would be going to pin 1. Is everything else in your build as per the V2 layout?

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    2. Well I skipped the CMV switch and simply wired pins 2&3 together, as well as pins 4&5 (which would be the middle position of the on/on/on switch, right?)
      I believe that right now, pin 1 goes through drive 1 to the clipping section, which then goes to the 1k resistor to the right of the opamp. I believe pin 1 should go straight to that resistor instead.

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    3. To add on to that, in the version 1 layout there's a jumper going from pin 1 to the 1k resistor, and that jumper is missing in version 2. I'm going to build another one this week and I'll let you know if it happens again and if the same fix will work.

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    4. Marcel have right about second layout(ver4). Resistor 1k should be connected to pin1 and on fourth line/twelfth column must be cut. I spend on this 3 days and i finally found why my layout not working. I hope so it help all of you.

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  7. Hey fellas, could someone please post a wiring diagram for this if they've been successful building it...?? Pretty please. I've done the board and boxed it up. Doesn't sound right at all....just super saturated and not sure if I've done this right.
    I did look at the wiring instructions and kinda go...wuuuut?

    Thanks fellas!

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    1. what kind of wiring diagram do you mean? are you talking about one for the pots or the offboard? if you're looking for the offboard look at the following:

      http://tagboardeffects.blogspot.com/2012/02/offboard-wiring.html

      if you mean the wiring for the pots, you need to know how to number the lugs, which is on the same post. if you look at the layout every offboard piece is numbered and needs to be connected to the right location on the pot or switch. so for example Drive 1 needs to be connected to lug 1 of the drive pot. there's is also directions on how to wire the switches to change between the different modes, and a picture of each switch with the lug numbered. so MOS/STD Sw3 goes to lug three of the Mosfet/Standard switch.

      i don't think anyone will made a layout showing where each wire goes. it's very time consuming, and since each layout tells you where to connect each wire, it's really not necessary. you have to learn how to read the layout to make it properly.

      if this is your first build i would put it to the side and make something simpler first, so you get to understand how to build a pedal, and then move to something more complicated like this. aside from possibly having the pots and switches wired wrong, you could have put components in the wrong place, or in the wrong way. remember, it's better to learn to walk first before you run.....

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  8. Hey Johns thanks for the reply. The Offboard section is a good read, agreed.

    What I'm confused on is the DRIVE2 and BOOST2 wiring really.
    The vero has an out called Drive2, but the notes also say Drive2 to ChSw2....similar situation.

    So can I assume drive pot2 goes to chsw2 and from there to drive2 on the board?
    I've tried it going from drive pot2 to board drive2 AND chsw2 .
    This is probably where I'm going wrong, but I'd just like some clarification.

    I'm pretty proficient at building electronics, albeit not as neat as Mr.Kallas!
    At present the pedal just sounds like constant diode clipping, with no real response from the gain and boost pots. So this is where I assume I'm slipping up.

    Thanks Sir! Appreciate the response.

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    1. Not a problem man. Sometimes we jump into the deep end of the pool way before we can swim, if you know what I mean. I myself built a Russian green muff using the "correct" Russian parts as my first build, so I was hoping you essentially didn't make the same mistake I did, cause it's better to start with something simple and work to something more difficult, especially if you have a problem debugging something like this is a bitch and a half.

      But anyways, what that means in the wiring description is that you need to have a wire connecting all those components. So you have a wire that goes from drive 2 to the switch, and have a wire that runs the board at the location marked drive 2. Boost 2 is similar in that you need to connect a wire from boost 2 to the channel switch, and a wire to the boost 2 location on the board.

      Don't take what I say as me being snappy or anything. I just type how I talk. I'm always glad to help.

      As a side note, I don't think there are many people even clots to as neat a JohnK's. I have one of his gamma ray od's that he designed and in person it's even neater then it looks in pictures.

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    2. And no need for formality, so no sir needed. Just glad to help buddy.

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  9. No worries. I've dialed it in now. The only thing I have is a massive volume difference on one of the CFV settings, and I've wired the boost LED in reverse.
    It gotta give it a proper test though.

    Cheers again for the help. You'd be amazed how much of my errors is just rushing things due to work demands.

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    1. Oh I hear that. Lately work for me has been crazy, so I haven't had time to build, but when I've built when it is I make the dumbest mistakes. My most embarrassing is that I had a pedal all boxed, I plug in, get bypass, turn it on and nothing. So I start checking for errors, solder bridges, the normal stuff, put it all back in, still nothing. I take it out mess with it, try it out of the enclosure and it works, box it back up, nothing. I spent probably 2-3hrs debugging until I realized the jack was in the wrong position in the enclosure and grounding out. I wanted to die.

      Glad it's working man. I'm not sure as I haven't built this yet, but it's on my list, but if the cf switch controls clipping diodes there could be a massive volume difference, as the forward voltage controls the overall output, so the higher the forward voltage the higher the output. If it takes the clipping away, there there will be a massive increase in output, so it could be right.

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  10. I just finished building this pedal and it sounds good, but i am having an issue with the output volume. I have to max out the volume knob to get just above unity gain. Anybody else have any issues with this? Any ideas on how to increase my volume output? Any help would be greatly appreciated.

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    1. I forgot to add that i built Version 1 with all of the alternative values.

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  11. Has anyone successfully built the second layout (version 4)? I've been debugging for days (and I'm no rookie) but I'm about to give up. Everything works great except for the volume pot and I have no idea why. It's not that different than the first layout, and I did switch the jumper to pin 1 of the IC instead of pin 2 as commented about above (that's gotta be a mistake with the layout), still no volume. Works great in boost mode...

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    1. I figured it out... after staring at the fool thing for hours. I had the 100 ohm resistor on the output going to the wrong place.

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