Wednesday, 2 March 2016

Sunn Beta Preamp

This is a single channel version of Sunn Beta Bass & Lead Preamps.
You can find the original FSB thread here.
There are two different sets of caps depending on which version you want to build.



You could use Mark's Bipolar Voltage Converter if you want:
http://tagboardeffects.blogspot.fr/2014/01/bipolar-voltage-converter.html

You could also use this external board to wire a Bass/Lead Switch instead of using fixed caps:

(20/H, 19/C, 22/J.. are board's points coordinates where C1-4 should be placed)


78 comments:

  1. Replies
    1. Can I just check your wiring for the dual gang pot - I'm assuming it's as follows:

      123
      456

      With the lugs facing me and the shaft upwards.

      Ineed to buy vero - a LOT more vero!

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    2. Hi Beaker!
      That's correct.

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    3. This layout has my shaft pointing upwards too Beaker.

      Nice layout Alex!

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  2. Yessss! There's no way I'm not building one of these. Thanks for the layout!

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  3. If I wanted to do a version with both which switch to use to be able to switch between bass or lead version?

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  4. Since you're switching 4 caps at once, you will need a 4PDT on on

    The caps are going to need to be "flying" offboard

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  5. I built this based off of the vero from the fs thread a few weeks ago. It could be my build, but the way the volume control is wired, it doesn't lower or raise the volume, just change the texture of the sound slightly. Other than that, it sounds amazing!

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    1. How is it the volume level at the moment?
      Too loud? Too quite? Unity?

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    2. It depends on where the gain is set. Less = quieter, more = louder, with more or less gain as well. Might be worth it for someone to experiment with having the dual pot split, as mentioned below.

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  6. interesting. what happens if i seperate the dual pot to 2 pots?

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    1. i mean somewhere at the dba interstellar overdriver, what is also uses a dual gang pot that if it seperated into two it gives different kind of overdrive tones

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    2. hi shvtsvcka. I am going to use 2 1Meg pots. I separated the dual gang pots on several builds on this site into two equal value pots and it worked fine. that's not to say this one will work.(I'll let you know) just remember that a dual pot intends that one value increases as the other decreases.

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  7. When they say you have to be careful when working on amps, is this one of those situations or is it just like any other stompbox. Nervous beginner here....

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    1. It's a stombox emulation of a Sunn preamp, so treat it just like any other pedal. It only has +/- 15 volts across it, so no risk of hurting yourself. The same applies to all the other amp circuits on here. if they are battery or wall wart powered, you don't need to worry.

      It's mains voltage amps where you have to be careful with what you are doing. The internal voltages in these can exceed 400 Volts, so one wrong move could potentially prove fatal.

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    2. That's what I suspected but I wanted to make sure. Thanks Beaker

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    3. just to add, i don't think we're going to see any full on amp layouts posted here for a few reasons. i've actually have a few done for some tube amps, but i've decided to not post them.

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    4. I agree Zach.
      For Amps I would go for a PCB too.

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    5. oh i didn't make any PCB for the amp layouts, they're all old school point-to-point turretboard. i really like the way turretboard amps look, just super neat, and you get to use super mojo parts for better sound. :P

      my issues are more about people really not ready for tackling something like it doing it and getting hurt or if it doesn't work not being able to troubleshoot it and wasting all the money on parts. that and there are some that i don't feel should have access to them, as they may use them in a way i don't approve of, if you know what i mean.

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    6. Agreed, turretboard is the only way to go for a robust amp build, with any real hope of repairing it should any part fail in the future.

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    7. go to tube depot. I built the 18 watt Marshall head and it is fantastic and really fun to build. drives a 4x12 perfectly for small to medium bars/clubs.

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  8. Will a 1N60p, 45watt germanium diode work in place of the 456A?

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  9. Can 1N456As be replaced with other 30V zeners?

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    1. Does anyone have an answer for this? I was about to ask the same thing as I'm having a huge amount of trouble sourcing the 1N456A's.

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  10. Does anyone know if I could theoretically run this into the effects return of my amp, bypassing my amps preamp? And taking this further could I buy a slave amp and just use that? Say, this circuit into a Sunn beta slave. Would that work like a Sunn beta without the two channels. Or is there something else between pre amp and power amp usually?

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    1. You should be able to run it into your effects return or poweramp. Depending on your amp, you may have to control your master volume from the pedal.

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    2. Wondering the same thing. I suppose it depends on how hot the signal is coming out of this preamp. I would like to run it into a Crown XLS power amp. A friend tried running his Tonebone bassbone into the Crown, but the the pedal is really meant to run into the front of a preamp as more of an effect rather than a true preamp outputting line level. The amp's input sensitivity is too high to drive it to full output with the Tonebone. Wondering if it would be a similar situation with this preamp, or if it can be adjusted to output a full on line level signal if it isn't already.

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    3. Just my $0.02, but anything distortion, fuzz, or overdrive I would not put into the effects loop of any amp, as the results are usually crap sound. The reason being that distortion, fuzz, and OD is supposed to emulate the preamp tubes being pushed into harmonic distortion, and using these sorts of pedals affects your preamp as well adding texture. If you put them in your effects loop you're bypassing the preamp tubes and going directly to the power tubes, which defeats the pedals purpose.

      The effects loop is really meant and great for modulation effects like chorus, phaser, trem, and delay. This helps keep them clear and from being slammed by pedals in front of them.

      If you're using an amp simulation pedal like this, it's best used as a preamp. So you want to put your amps eq into the neutral position, and use the eq on the amp pedal. Catalinbread likes to call these foundation pedals, since the idea is they replace your amps preamp, and will behave as such. So if you put an OD in front of this it should behave like a real sunn beta.

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    4. Disagree with Zach here. The Catalinbread pedals are designed as pedals and intended to work with an existing preamp. If this is an accurate copy of the Beta preamp, then it's more akin to something like the Tech 21 amp sim pedals, which are generally intended to be run into a clean power amp or PA, and the documenation for them recommends using the FX return to bypass the preamp when used with a normal amp. Unless there's an issue with the output level of this pedal, it should definitely be run in a way that bypasses your amp's preamp section. Also, ideally into a solid state power section, as that's what the Betas were to begin with.

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  11. Hello fellas!
    Anyone can explain please how to releaze switch between Bass and Lead caps?
    As I understand, 4PDT switch will not be enough for the four different capacitors.

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    1. The only way to do it mechanically on a single switch would be with an 8-pole. They do exist, but they're really expensive and difficult to find. The most elegant solution would be to make up a daughterboard with 4 double-pole relays, that way you could activate them from a single switch, even a stomp. This would eat up a lot of internal space though, I don't think you'd get everything in a 1590BB.

      The simplest option is just to use multiple switches, either two 4P3Ts or four DPDTs. I'm gonna go with the DPDTs, It'll be a bit clunky, but I can't really see wanting to switch between bass and lead on the fly.

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    2. You have built it already? Its fully workin' vero?

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  12. You can do it with a single 4PDT and no daughter board. It will require some flying connections

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    1. How would you do it on a single 4-pole?

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  13. It's a bit complicated to explain with text. I'll have to make a diagram when I get home later.

    Until then, think about how you can switch between two caps with one SPDT, and then do that 4 times for the 4PDT

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  14. This is how you can wire the 4PDT, and switch between the 8 capacitors in same time.
    https://dl.dropboxusercontent.com/u/8372380/4pdt.jpeg

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    1. https://dl.dropboxusercontent.com/u/8372380/4pdt.jpeg

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  15. Ahh of course, brain's a bit foggy today, I've never used an SPDT for this kind of component switching so it didn't really occur to me, the extra wire and floating side of the cap always bugged. It's doable but it'd be very messy, I'm sure someone can make it look neat, but I think I'll stick with the 4 DPDTs.

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  16. Built it! Had a false start wiring lugs 4 and 6 the wrong way round on the drive pot. I also had to use the voltage converter on the rusty box layout to get the voltage to -15/+15. Once I'd sorted it though....

    I've never played a sunn beta so I can't say for sure but it sounds pretty good to me.

    Thanks for the layouts

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  17. Thanks for verifying it!
    I've added an extra board for the Bass/Lead Switch.

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    1. Thanks Alex. Just to confirm, if using the Lead/Bass daughter board and switch, C1 - C4 should be ommitted (or removed) from the main board?

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  18. The board/switch subs those caps.
    Both sets of C1-4s will be on the daughter-board.
    The 4PDT will switch between set 1(Bass) and set 2(Lead).

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    1. That's what I thought, but just wanted to make sure!

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  19. Better safe than sorry!
    Hope it works well.

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  20. Would anyone be willing to upload some sounds or videos with sounds of their builds of this circuit? I've been falling in love with the Sunn sounds lately and am contemplating either buying or building a 70's- era Model T (original or clone), or something similar, but haven't bit the bullet yet.. I'm wondering if this would be able to get me into that territory or at least somewhat close.

    Thanks for all your efforts and feedback so far on this one.. great!

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  21. Does this build require building 3 'little' boards. One for 9v >18v+. 0ne for 9v>-18v, and then a board for +/-18v into +/-15v?

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    1. No. There's a link right under the layout which will take you to the daughterboard for power. You could also use the daughterboard from the rusty box, which will give you +15v/-15v rather then +17v/-17v which is the board in the link.

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  22. I had a Sunn Beta Lead combo about.....35 years ago. If this comes close it is really quite a sound.

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  23. hey there,
    i'm having problems getting the 15volt board to work. when i measure the output (aiming for 15v with 1n4001 diodes) i'm not getting any at all. sometimes it goes up to 15, 18 something and immediately to 0v. unfortunatly i think i caused a shortcut when trying to measure the first time (little sparks, ups ;-)
    well so i guess i might have broken something.
    i measured the ic ground to the pins as follows:
    1- 1,14v
    2- 0,85v
    4- 0,25v
    5- 0v
    6- 2,3-2,5v (not steady)
    7- 1,88v
    8- 9,39v
    can you guys read any trouble with the ic from this?
    thanks

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  24. I have a noobish question about this build, can someone tell me if this can be used as an Amp to power a 1x12 speaker or 4x12 cab?

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  25. Built and worked a charm first try. I assembled the bass version without the switch and I really like the driven tone for stoner doom sludgy riffs! Works great on guitar too. Things to say:
    1) I had some trouble getting the Voltage Converter to work with 1N4001 diodes (still having +-17 volts readings) so I had to use the Rusty Box trimmer. This seems to be a common problem and common solution.
    2) The volume pot does nothing. It does some nasty noise below 9 o clock, reading on FSB thread this seems to be a common problem also.
    3) I get quite low output, good for using this as a pedal but not for using as a preamp to go in a amp's effects return input.

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    1. Hello, how did you fix the problem with the volume pot?

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    2. Mine came out really loud actually. If I use it into my effects return it's actually too loud for bedroom practice. I have to run it into the amps preamp to rein it in a bit. Considering this I would say the problems with your volume pot is causing yours to be quiet. I don't know what to suggest though as mine worked pretty much first time. Maybe check the wiring of your gain dualgang pot as I fudged that up initially and it all sounded a bit off.

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    3. This comment has been removed by the author.

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  26. after getting the 15v to work i now struggle on getting the rest to work ;-) the signal cuts out on pin7 of ic2 (first 4558)
    i opened the topic in the following link, where the voltages and a few pics are to be found.

    http://guitar-fx-layouts.42897.x6.nabble.com/Sunn-Beta-Preamp-no-output-on-pin-7-of-the-first-IC-4558-tp31771.html

    it'd be great if you guys could take a look at it and let me know if you can read any false values on the ic's.

    thanks

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  27. Any soundclips of pedals anywhere? Mine's still WIP status, missing some components.

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  28. Hi everyone,

    Mine's built but not working unfortunately. On power up I get no signal save for occasional crackling/popping through to the speaker when turning the treble pot only. As I take the treble pot down around to 0 I tend to get the popping then and little sparks within the pot itself.

    I've done 3 things but get the same problem...

    1) I retraced every component and found I'd missed the 10u cap in the middle of the board.

    2) I took a Stanley knife to the back and made sure I'd not had an solder bridging rows.

    3) I changed the treble pot (though a quick test on the previous one with a multimeter showed that it was perfectly fine).

    Does the solution to this sound obvious to anyone? I can post pictures if requested. I've built quite a few pedals but am unfortunately a complete noob when it comes to troubleshooting.

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    1. P.S. I'm doing a +/-15V version using the suggested charge-pump build. It's all on the same vero board but that section is completely separated. Measuring the voltage from battery-in to ground on the preamp itself gives about 15.7V.

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    2. Sparks in the pot is never a good thing. The row above Treble 3 is a power rail (after the cut under the 12K) Turning the treble pot down will short v+ to ground if you have a solder bridge somewhere here. That explains the sparks when fully CCW. Test for DC on lug 2. Then check for DC on the Level and Bass pots.

      Have a good look with a magnifying glass and test for continuity with a meter. Failing all this, post some hi res pics in the Debugging section of the forum.

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    3. Thanks very much, Ciaran. It's approaching midnight where I am but I'll give that a crack soon and post results. Failing that I'll get a good image up.

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    4. Fixed, by the way. Sounds excellent. Cheers. Turns out one of my links was one space out and I managed to cross things out on my schematics too messily to notice until I went back and triple checked things.

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  29. Guys,

    Since I've fixed mine I've noticed that pushing the level past even halfway completes destroys the sound if I've got the gain turned up past zero. It stops giving me a nice overdriven sound and turns into a complete nightmare of crackles.

    Anybody else have that issue? I sounds beautiful in other situations whether they be totally clean, overdriven or full blown distorted sounds... but there's not way I can crank the gain even a little and have the level go past the halfway point.

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  31. Is it emulation of preamplifier or it full value preamplifier that needs to be plugged in a power-amplifier?

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    1. Not sure what you mean full value preamplifier. This is the preamp section of the sunn model t amp.

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    2. I meant it, that it will be a full preamp section, but not stompbox giving the alike sounding, as "аcapulco gold". Thanks!

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    3. Don't know if I've understood correctly but this doesn't emulate the preamp.
      It is its exact copy.
      I've used the original schematic.

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    4. Splendid! This is exactly what I wanted to know!!!
      Sorry for my english, I'm from Belarus

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    5. Don-t worry. Your english is good enough.
      Glad we could help!

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  32. Does anyone have any demo of the finished preamp?

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  33. Any real purpose of using tl071 on the output? Does it have same characteristics as 4558?

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