Monday, 2 April 2012

AMT B1 Legend


And so on to the next AMT pedal, this one is based on the Bognor Triple Giant Sharp Channel.  I've included trimmers with this one to help bias the alternative JFETs so this may be a better one to start with if you're interested in building an AMT pedal.  I haven't included the cab sim, but you should be able to use the one shown in the AMT S1 layout.  At 23 columns wide it will only fit in a 1590B vertically, but I wasn't too bothered about keeping the size down with this one because I think most people would want to put a 5 knob effect in a 1590BB size box.

Info from AMT about the original:

The B1 Legend Amp Series pedal, superior high gain quality distortion, as found in the Bogner Sharp Channel Amplifier*. The sound of the AMT B1 is monstrous in tone, aggression, and provides massive amounts of gain. Thunderous lows, screaming highs, and scoopable mids leave you with unbeatable heavy distortion sounds. This one could be the "kick" your guitar rig has been needing.

•  The AMT Legend Amp Series guitar pedals provide excellent dynamics, nuances, and characteristics similar to that of tube driven amplifiers.
•  Tube-like range of volume control provides great sound density, playability, and power when playing at full volume and also in conjunction with your guitars volume knob.
•  TRUE BYPASS. The preamps of the Legend Amp Series pedals use passive true bypass circuitry, therefore no loss of guitar signal is noticed in your pedal chain. Similar to if no pedal was there at all when bypassed.
•  Features high level of output signal (+10dB in extreme position of Level knob) corresponds to the output levels similar of tube preamps. Thus, you have adjustable signal level allowing to hook up your preamp AND direct input of a power amplifier.
• Controls include LEVEL, GAIN, LOW, MID, and HIGH.
• TWO signal outputs: DIRECT AMPLIFIER OUT for guitar amplifier use and CAB SIMULATION OUT for mixer, or studio use. 






Update 1: The person who prepared the schematic has posted that he has noticed an issue and he needs to correct it, so hold off on making this until we can get some confirmation of the scheme it is based on. 

Update 2: I will do a new B1 vero layout based on the corrected schematic, but in the meantime if you have started building this version, you can complete it by using the daughterboard shown below: 

70 comments:

  1. I am gonna try to build this one.. what do you think the odds are of it working lol?

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    1. I've been over the layout a few times and am pretty confident that it matches the schematic, and using trimmers should help with any biasing issues that you may get because of the different choice of JFETs. I've also got a pretty good success rate so yeah, why not! :o)

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  2. Oh damn... I just about had it built :(

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    1. He literally only just posted on FSB a minute before I put it on hold. Hopefully it will only be a small mod of some sort but I'll let you know what needs to be done.

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  3. Cool, Thanks Mark! I see lugburz2000 posted the corrected schematic already...

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    1. Yes, as soon as he confirms my question, I'll do a little addon board for it. It should only be small so shouldn't be a problem.

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  4. Did you by chance see the full P1 schematic posted yesterday on FSB? Not sure how accurate it is but it looks pretty good... He actually de-soldered the smd caps and measured...
    http://www.freestompboxes.org/download/file.php?id=17702&mode=view

    Thanks,
    Jim

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    1. Yes I got the corrected layout he posted. It looks like he is confident about that one, but after what happened with the B1 I think I may wait for the schematic to be verified before I do the layout

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  5. Mark, thanks for the daughter-board! I may try it tonight... I am about 3/4 of the way done designing a PC board to etch.. I have not been real lucky with vero boards.. I have made hundreds of PC boards but for some reason I shy away from vero. I really need to go to Radio Shack and get a bread board... I am a procrastinator. Either way I will let you know if that schematic is any good.. Thanks Again ~ Jim

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    1. Cheers Jim. I actually think vero is quite forgiving because you have such a large track to solder to, although I agree there is something nice and easy about using a PCB.

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  6. Mark - I think the schematic for the B1 is pretty much verified by "lugburz2000"... He posted 3 audio tracks, one is the real B1, one is the protoboard without final stage and the last one is the protoboard with the final stage added. They all sound alike and the protoboards sound almost just exactly like the original B1 from what I can hear... I have looked over your vero and it looks to be 100% with the schematic, so... I don't have a 2N5457 so, I really can't verify your vero yet but my guess is that it will work.

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  7. Ah, looks like he also put up a couple more schematics... A few more changes lol.

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    1. Yes. I think I'm going to wait with these AMT pedals to do my final layouts. After a few have been built by people I'll have a better idea of what scheme to base it on.

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  8. Ok Mark, I finally got around to finishing the vero that you did and it works! Very nice and I didn't even use the daughter board.. Also I used a J201 for Q1 because I didn't have a 2N5453. I didn't have any 20k trimmers so I used 50k instead and adjusted, works fine, there is just a lot of extra head room... Sounds damn good!! Every thing else is exactly spot-on with your vero! I know "lugburz2000" changed his schematic a couple time after he posted the first one and they are probably good also but this one is wicked good! Tons of gain and the tone stack is great!!! It's a keeper!

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    1. Brilliant, thanks for confirming. After hearing the clips there probably isn't a lot of point in doing another layout, I'll definitely be building this.

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  9. Oh I forgot, I used 1N4148 for D1 - D3 and I think on the vero yours are in backwards? I know that he changed the diodes on his last schematic from the + side of the 47uF caps and ran them straight to ground. I tried them both way and I really didn't hear a difference...

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    1. I don't think they're backwards. He has anode to gate in the old and updated schematics. I've got BAT85's so I'll stick to the gate to source, can't be bothered trying to accomodate diodes to ground to experiment! :o)

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  10. No luck on the cab sim yet... :( I will work on that this weekend and see what I can come up with.

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  11. Ok, I was just going by this with the orientation of the diodes...http://dl.dropbox.com/u/11178619/diode.jpg

    Maybe I am confused but it looks like the striped(Cathode)end of the diode is going to source?

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    1. Yes that's right, the cathode is going to source in his corrected schematic: http://i76.photobucket.com/albums/j6/IvIark_2006/Layouts/Schematics/AMTB1-corrected.png

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  12. Why did it space all of my words like that?? LOL

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    1. Blogspot must have auto justification :o)

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  13. Mark, the B1 sounds insanely good!!! Wish I could get the cab simulation to work...

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    1. I've been over it a few times and it certainly looks accurate to the schematic to me. I'm just wondering if it could be a biasing issue with it using different JFETs. Maybe a trimmer instead of the 12K to Q2 drain could help bias it, or maybe the 12K at Q1 emitter

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  14. Great idea! I will try that!!! Geez, why didn't I think of that? That's why you're the pro and I'm the schmo... ;)

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    1. Ha ha, there's no pro here, I'm an electrical engineer by trade who spent years designing control systems and programming PLCs rather than getting down to component level, and now spend most of my working life creating things in and playing with Flash. I'd love to be a real expert in electronics, but I'll have to make do with my hobbyist status! :o)

      I'm very interested in what you discover with the trimmers, it would be nice to mod the layout so we know it will work with our usual through hole JFETs.

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    2. Incidentally, just for future reference what have you got the main trimmers on the B1 board set at? Can you measure the voltage at the drain of each JFET as that will be a great guide for anyone else building this. Thanks :o)

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  15. Ok here is what I have and keep in mind that I adjusted these by ear... I do that because I am lazy lol. Seemed to be pretty close so I guess my ear isn't too bad..!
    Q2 = 4.95v trimmer = 6.8k
    Q3 = 4.00v trimmer = 7.3k
    Q4 = 7.15v trimmer = ?? not sure since I have a 100k trimmer in there because that was all I had so, it's almost completely off... Doesn't give a consistent reading and I don't feel like removing it at the moment.. I believe a 20k will work perfectly so anybody building it should have no trouble...

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  16. I also used the low pass RC filter connected between tone control and volume pot to ground.
    The ones I use are 47nF and 10k.. Seems to tighten up the bottom end quite a bit. No need to change the current layout for this, they can be added on lug 2 of the treble pot to ground...

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  17. I think the 100nF cap going to Low 2 & 3 is supposed to be 47nF..?

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    1. Yes, cheers for that. Copy and paste (and forget to changed value) syndrome! :o)

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  18. btw - 22nF sounds good also...

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  19. i think that i'd like to build this one but i'm not sure how the daughter board connects to the main board? did you evr make a vero that has all of it on one board?

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    1. The daughterboard is fed by the High 2 lug. I didn't do the full board, I decided to hold off on all the AMT pedals until we have a bit more experimentation regarding which JFETs worked as good replacements for the SMT ones they used, and any other corresponding circuit changes that may be required. But it seems that it's still pretty safe to do this one because I included a trimmer for every gain stage JFET and everyone I know who has built this said it worked fine. I'd consider omitting the daughterboard completely at first and see what you think, because the clips I heard with and without seemed very similar to me. All the daughterboard is is a filter and a final recovery stage (which doesn't seem to be required anyway as there's plenty of level on tap with this).

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  20. Hello! I built it? but I can't bias Q3 anyway. Tell please, does anyone have such a problem? What did you do with it? Thanks!

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    1. Sorry! I mean Q4! Q3 ok) But in Q4 is 9V on drain and can't do anything with it.. Thanks!

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    2. Oops, just had a quick look and the source resistor is down as 680K instead of 680R. Swap that and see if that fixes it.

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    3. Thanks! It's work at last! Correct source 680R resistor fixed Q4 bias problem. Now it's work and sounds very nice.

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  21. Hi Mark,
    I am interested in the P1. On May 19, 2012 I noticed you posted in another long website chain (should I not mention the specific site here?!?) that you had nearly finished the veroboard for the P1 - that it was very large, about 46 columns.
    Did you ever finish that? I'm more interested in the main circuit, not the cab sim.
    Thanks.

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    1. I didn't finish it because I thought it had got a bit big so my intention was to redo it on two levels instead of one long run. This was how far I got with it, just to check against the schematic

      http://oi48.tinypic.com/t68748.jpg

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    2. Thanks for sharing that Mark. Can I assume you used J201's as you did in the other AMT layouts (I see your added trim pots for biasing in the incomplete layout). Also, were you going to use BAT85's in place of the BAT54's ? (I read that those were good substitutes and I see one can still find them).
      Thanks!

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    3. Yes I'd have used J201's, not sure about the diodes, I suppose it would have been a case of experimenting but the BAT85's sound good to me (and I've got some so I would have tried them).

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  22. Yep, its working for me too.

    I only had 3 x BAT41, i used a "1N914" for the daughterboard.

    It seems to sound a little bit bright and bottomless in connection with my Champ12 clean channel.

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  23. just built this one and it sounds just like the video. I didn't build the cab sim yet, but I did combine the daughterboard with the main one. I also found that an A50K gain pot (audio) has a much better taper than a C50K (reverse audio). I tried a C50K, a B50K (lin) and an A50K and the A50K gives the smoothest range).

    here's my layout based on Mark's two veros:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/AMT/B1_Legend_Vero.png

    I socketed a couple of the resistor's drain (Q1 & Q5) so that I could get their drains at the proper bias voltage (Q5 took a 13K resistor on mine)

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  24. DONE! I really like this one. pics below:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/AMT/B1-01.jpg

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/AMT/B1-02.jpg

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    1. REALLY VERY NICE, John! Really good!
      Which voltages did you use in the trimmers? Thanks in advance.

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    2. IIRC, 4.5-4.75V, (normal drain voltages for a Jfet bias)

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  25. I can't seem to get this to sound quite right. It's definitely not a high gain type of distortion, I'd compare the sound I'm getting to more like a DS-1. I have to turn the trimmer for Q3 all the way off to get a decent sound. I've looked all around Q3 for placement errors and even replaced the J201 just in case I burned it up. I did use Fairchild J201's, this wouldn't cause a problem would it?

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    1. Measure all the transistor pin voltages to ground. That should give a good clue as to where your problem is happening. It's high gain so something isn't right

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    2. Right now I've got
      Q2= 4.5v
      Q3= 9.6v
      Q4= 3.2v
      With that configuration I get a usable distortion sound, but it's nothing like the demo vid. If I rebias to J0K3RX's recommended voltages then I get a horrible thin and unusable icepick overdrive type of sound. Any thoughts?

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    3. you may have something wrong with your build. I love how mine sounds with the trimmable jfets set at 4.5-4.7V.

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    4. Yeah, I wish I could figure it out. The demo sounds amazing.

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  26. This comment has been removed by the author.

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  27. Hi, My B1 sounds fine. When I omit the daugtherboard the gain doesn't do much after the first half of the range of the pot. I am getting full gain so that is not a big problem. However, when I connect the daughterboard my volume pot only works as a sort of on/off knob in the first small part of it's range, then doesn''t do anything until it reaches almost the end of it's range where it suddenly makes the difference between low and max volume.

    Does anyone have a clue why this is happening?

    Any help is greatly appreciated!

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  28. Maybe I will just rebuild it but now with John K's version but it's a lot of work for just a pot range problem...

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  29. Anyone have the vero layout for the AMT P1 or P2???

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  30. I just finished this circuit and I love it. You can use use the 2N5457 for Q1 no problem. Mine came right up. The volyages on the J201s have a LOT of range and the very cool thing about it is how much the frequency ranges on the tome pots vary depending on how much volyage you give each transistor.

    Start out with 4.5v on each, but maybe reduce Q4 to lower the noise and raise Q2 for more fullness. The best thing about this for me so far is it the SOOO loud that it does not lose its edge when you turn it down, it sounds just as full on half-volume as it does on full volume (referring to the volume pot).

    I used B50k for gain, A500k volume, A500k bass, B10k mid and B100k for high. My favorite by far so far and I will box it up tomorrow.

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    1. Nice one Paul, AMT do make some great pedals.
      Did you just make the main board or include the daughterboard too? I wasn't sure whether the daughterboard would even be needed as there seems to be plenty of volume after the tone stack even without the recovery stage

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  31. I didn't even notice there was a daughterboard when I started building it (not sure how I missed it), but no, I I did not build the daughterboard. The circuit works fine, great, even, woithout the daughterboard.

    By the way, I never fully understood why the daughterboard was needed. I also do not know which part of the circuit is the speaker emulator.

    Since I know you are interested - here are the voltages that I like best on the J201s
    Q2 = 3.25
    Q3 = 5.3
    Q4 = 1.7

    However, you could practically pull numbers out of a hat for these voltages. I also had Q2 at 7.0 and Q3 at 2.5 and I liked that tone as well. In other words, there is a wide working range of voltages here. You could even build this pedal with holes to access these trim pots and individualized the pedal for different amps. The point is that the tone controls seem to respond differently depending on what voltages you select - so it is purely a matter of taste.

    I have it hooked up to a breadboard for power and I am noticing a somewhat irritating buzz at about 480 Hz. I am not sure where to start looking to eliminate that. I can tame it by turning down Q4 (or any Q) but you lose some of the gain.

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  32. Oh, I see now the speaker emulator was a separate add-on project, not in this circuit.

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  33. Final Update on the Legend B1 - what an amazing drive! This pedal is the best one I have built form this site yet, and that includes the Wampler Plexi and the Timmy. With the versatility of these tone controls you could use this pedal to get almost any overdrive tone you want.

    I mentioned before a couple of things - an oscillation, and that you can bias the trannys at differents Vs for a variety of effects. Once I boxed it up - the oscillation went away. I also boxed it up with the Vs that sounded best to my ear, but when I tried it on different amps I sometimes got too much bass, and weird effects like a delayed attack, so I reset all biases to 4.5 and reclosed the box.

    This thing sounds perfect that way. It is dead silent when not playing and the loudest effects yet when I play. The tone controls are still ultra versatile, but tilted more towards the high end with the Vs all set at 4.5. Overall, just a great effect. I added an effects loop to it so you can tie in a delay unit if you want.

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    1. And where is the final, complete and revised layout? Thanks!

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    2. I just built the top circuit without any daughter board for a corrected schematic. It sounds great.

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    3. And is it sounding exactly like the video?

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  34. I built this one this afternoon using Johnk's layout http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/AMT/B1_Legend_Vero.png
    It sounds absolutely hudge !
    Tons of gain, very effective eq controls, bass stay tight on palm mutes. I'm very happy, a keeper.
    I have only one remark, maybe too much highs, I have to roll the pot almost all the way back to get the sound I like, so which capacitor(s) should I tweak correct this ?
    Thank you !

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    1. How can i find more of johnk diy effects vero layouts?

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    2. How can i find more of johnk diy effects vero layouts?

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  35. All veros from this site (included johnk vero) doesnt match schematic (this one from site-> http://i76.photobucket.com/albums/j6/IvIark_2006/Layouts/Schematics/AMTB1-corrected.png). In those veros are missed two 100uF, one 470uF, one 100nF and one resistor 33R. I believe B1 without those caps and resistor can work very well, but I was thinking how it will sound if I will build it with all the parts from schematic. Will see :)

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    1. All of those are redundant power filter caps. Meaning that single 1000µ cap does the same thing. And since those are all power filters, the impact they have on the circuit and its tone is zero.
      +m

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