Saturday, 10 September 2016

Orange AD200b MkI (On Hold)

Up next in the tube preamp series, I give you the Orange AD200B MkI. Made in very limited numbers, only a few hundred if that, in 2001 these were made P2P on turretboard. Known for great clean, with a focused midrange, but has great grit with the gain cranked.

Unlike the Sunn Model T, this has not been breadboarded and tested out, I just followed the same concepts Ciaran and I used to convert the Model T preamp to use FETs. This means at this point, there may need to be some tweaking to component values to get it just right.

One thing to note, as I didn't put it in the build notes. All the pots are dual gang pots, with each corresponding lug connected. What this means is lugs 1a & 1b are connected together, 2a &2b are connected together, and 3a & 3b are connected together.


Edit: Putting this on hold until i can get some time to breadboard it and get it sounding right.

26 comments:

  1. Great upload! Where can I found the schematic of this amp?

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    1. search google, you should find it.

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    2. Lol man. It's out there. There's a site that has a bunch of amp schematics, you need to be on the prowl for it, if you catch what I'm saying.

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    3. man there are a lot of sites with a bunch of amp schematics(first of all bmamps) and no one have the mki, only that wrong mkiii. is no longer simple say me what is the right one? i really don't understand all this useless secret.

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  2. This comment has been removed by the author.

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  3. Very nice.Is this a bass amp or guitar amp? Are there any other Orange amp in a box builds out there? I have a good friend that loves the Orange amps he has 5 or 6 heads . I might want to make one of these and gift it too him But I want it too be for guitar. I googled the model number and it says Bass head. I have vintage Marshalls other than open Jams or sitting in I have never really got to check one out properly. They are killer amps though. Nice work on the layout thanks

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    1. I believe this is a bass amp based on Dr.Google. The Earthquaker Devices Monarch simulates an Orange if I'm not wrong, and I think it has a layout here.

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    2. dr.google my ass. you are 100% wrong D_Pan. Read the description of the Monarch, and look at the topography, and compare it to this circuit. they are completely different animals.

      The Monarch is a generic distortion/od that is supposed to sound similar to a generic orange guitar amp, this is a preamp that has been converted 1:1 from the tube preamp from the orange ad200b bass head, which you can also see in the switch to give you the option for hi and lo inputs.

      now if you look at the topography of both circuits. assuming that each FET is a replacement for half of a preamp tube, such as a 12AX7, the Monarch has 4 FETS, which would equal 2 tubes, while this preamp has 2 FETS for the single preamp tube in the ad200b before the phase inverter and power tubes.

      not only all that, the layouts are completely different. i suggest before you make a remark like this you check it out for yourself.

      strassercaster, the ad200b is a 200watt tube bass amp. it should be good to go, but since it's hasn't been breadboarded. i'm not sure how the output is, so if it's low you may want to put a little booster after this to bring up the output, and not sure why they used dual pots like this in the amp. i'm fairly certain that the values should be good though to get it where it should be.

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    3. strassercaster: The only one I know of is the Orange Peel, originally developed by Runoffgroove, however I can't find it anymore on their website. It was also published here as a tagboard layout under the name Orange Graphic MKII as it is the preamp of that Orange bass amp.

      Zach: I'm not writing too often here, so I would like to thank you here for keeping this site alive and all your great work. So... Thanks a lot :)

      As for the dual gang pots: if you solder the lugs together I think it is like having two pots in paralel with the same values. And then you could simply half the value and take a single pot, e.g. Gain here is 500k Log dual, then one could use a 250k Log single. Or am I maybe missing something essential...?

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    4. that could be the reason, but not sure to be honest. if you think about a dual gang pot, the two parts usually are opposites, so as one increases resistance the other decreases. the MKIII which you can still get uses single gang pots most are the same values, which is why it's throwing me.

      as for the graphic citrus, it's more of an upgrade to the orange peel. it's not as noisey and supposidly sounds better. can't say from personal experience since i haven't built it.

      thanks for the kind words man. happy you're part of the community and you should post more often. no need to lurk around we're all brothers of the iron here.

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    5. Well... I have only one 100k dual pot here, but with that the two halves go in the same direction. And I think in the past where I used dual pots (Boss Blues Driver, Rub-A-Dub Deluxe) they all were the same. I don't build much on tagboards lately, I prefer my own PCB layouts, but I might try this one, just for trying out the "theory of pots" :)

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    6. Sorry, Zach. Didn't mean to anger you. I misunderstood OP's comment and accidentally gave him the layout for an OD instead of the proper amp preamp which he actually asked for. On the Dr.Google comment, I was just saying that from my searching, the AD200B turned out to be a bass amp. I didn't mean to disrespect your work. In fact, I respect and admire the fact that you and Ciaran have been making these tube preamp layouts for the rest of us. Sorry. I should really try to be a bit smarter with these kinds of things and to be 100% sure of what I'm saying before saying anything.

      Sorry, mate.

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    7. no worries man. as i wrote below with max, i think things can get out of hand when talking through text, since you can never hear ones inflection or tone. i took it wrong way, ie saying it's just a waste of time and doing something that's already out there. i think i'm losing my mind atm, since i got a massive gross anatomy exam coming up.

      i swear going for my doctorate is botht he best and worst thing i've done. but, honestly, no hard feelings, we're both brothers of the iron. we can get all pissy and shit, but everything is good.

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  4. Dear Zach,

    just some bits of information before you continue with your work on your preamp pedals.

    The JFET to Tube idea is years old and if I am not mistaken popularized by ROG. They reference to the original research article of Mr. Danyuk that gives some specifications on how to achieve tube like behavior. Most importantly the source resistor needs to be tailored to the particular JFET used to 'tame' the transfer characteristics from square to 'to the power of 1.5', the latter also describing a triode transfer curve.

    However this is only true in the case that the JFETs are not overdriven. In this case the transfer characteristics is set back to square as the local feedback in the source path is rendered ineffective. This is a severe limitation of the JFET to triode approach.

    a few remarks:

    - a lot of people dropped J201 in favor for 2N5457, as the latter are closer to ECC83 in terms of gain, internal resistance, etc.

    - higher voltages than 9V (18V or even better 25V) lead to better results

    - one cannot paint by numbers (e.g. just replace a ECC83 with a J201 and scale down the voltage). Everything is off. The bandpass created by the tube (miller capacitance - read ROG), the internal resistance of the JFET (try to do tweed deluxe preamp and you will see that it doesn't work), the gain, etc.

    - studying the schematics of the AMT pedals gives an indication of what can be done with a little bit of engineering.

    - the distortion behavior of the two preamps you have put on this side (Model T and Orange) is dominated by the PI and poweramp distorting, a thing you completely omit. Such an approach is OK for high gain preamps (only preamp distortion - see AMT pedals again), but fails for vintage NMV amps.

    max

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    1. hey man. you're completely right that this idea of tube emulation has been around for a long time, and yes ROG is one of the places where the idea got traction in the DIY community. you also seem to think i know less about this then i do, that i haven't read what's been post involving tube emulation, but I have.

      i want to touch on the other things you mention.

      1: the switch from J201 to 2N5457 because they "sound" more like ECC83 tubes. the ECC83 and 12AX7 are the same basic tube, the ECC83 is the british equivalent of the 12AX7, so if that were the case then 2N5457 would not be used in effects that are repacing 12AX7 tubes. each have their own characteristic distortion, and are swappable. one of the reasons for the switch was J201s were obsolete and prices went sky high, while 2N5457s were still good prices. you can interchange 2N5457s and J201s in an effect like this.

      2: the idea that running something like this at 18V or 25V will make it sound right or better rather then running it at 9V isn't always true. the most recent amp in box from ROG, the thunderbird is run at 25V and uses TL072 chips rather then FETs. there are a few amp in a box pedals that are floating around running at even higher voltage, but that does not dictate how whether it will sound good or right or not. high voltage does not mean better results.

      3. there is no paint by parts going on in this or the model t preamp. the model t was tested and tuned on the breadboard, and as i stated in the top of this layout using what was learned from that design was used to make this layout, and has NOT been breadboarded so you may need to change some values. all good circuit designers use what they've learned from other designs to create other ones.

      4: it's not power tube distortion it's preamp distortion and phase inverter distortion. the power section amplifies the distortion, it does not react to how your playing (not touch sensitive). you very rarely get power tube distortion. in one of these pedals we can leave off the phase inverter in many cases. could this need it added? maybe, again this is one that has NOT been breadboarded. so at this point who ever works on it will have a hand in designing it, which many people in the community don't usually do or have a chance to do. now they can.

      read this: http://www.guitaramplifierblueprinting.com/files/Phaseinverter.pdf

      5: while the model t is vintage, the orange isn'tm nor are they NMV amps. NMV amps may very well likely need to have the phase inverter tube, as it will not just add distortion but it's part of the power section and will help amplify the signal. in all tube amps, regardless of type, you're getting major preamp tube distortion, followed by phase inverter distortion, and then amplified by the power tubes.

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    2. Hi Zach,

      I feel a little uncomfortable replying to your last post. So as a primer: no harsh feelings from my side and please don't take my words personal. I am just referring to the engineering aspect of your tube to JFET preamps.

      ad 1: I don't differentiate between ECC83, 12AX7, ECC808, russian equivalents, etc. They are all characterized by µ=100, Ri= 62.5kOhm, S=1.6mA/V.

      The switch from J201 to 2N5457: You may be right. Still the point about J201s having completely different transfer characteristics than a 12AX7 is valid, especially if the JFETs are operated with 9V.

      ad 2: This was referring to JFETs like 2N5457 and J201 in the type of stomp boxes we are talking about. No need to bring in Opamps. 2N5457 and J201 have a max voltage of around 27V-30V, if there are builds with higher dc voltages, than they are just the brain child of people not knowing what they do.

      ad 3: Sorry to be blunt. There seem to be no engineering done on your side. Spice simulations? Read research papers? The status quo of JFET emulation is established by the guys around AMT electronics (and a few other Russians). Ever tried Schottky diodes at the gates? What about using n-channel and p-channel JFETs like in the LA2 series and compare the results? I've been there and all of the above mentioned strategies yield better results than just replacing triodes with a J201 and using 9V as supply voltage.

      ad 4: Sorry Zach. The supplied pdf is not really informative and wrong in most parts. Please reread good articles (Merlin Blencowe is a good start). The input impedance of output tubes is collapsing when driven hard. This tremendously loads the PI tubes, which in turn creates a completely different distortion than the PI-tube alone. But I don't want to start a debate about labelling. >70% of the distortion in the Orange and Model T is created in the poweramp (incl. PI).

      ad 5: I was sloppy with the wording about NMV amps. I intended to say: Amps that create the distortion in the poweramp (incl. PI). You are absolutely wrong about all tube amps creating distortion in the preamp (only modern amps do that). You can easily check that yourself: Do a Spice Simulation of the Orange amp or use an oscilloscope and measure the signal inside the amp at different points (warning: high voltages. You should know what you are doing).

      max

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  5. To complete the above post:

    here is the link (http://uploaded.net/file/xfl1lir8) to a LTSpice (it is free, so no reason to not have it installed) simulation of the AD200B MkIII (I don't have the MkI schematic and I am not going to waste more time on looking for it).

    Included is a version of the original amp up to the cathode follower driving the output tubes. For comparison there is Zach's version and a version I just compiled for comparison minding some basic design rules (18V, suitable source resistors, caps emulating the miller capacitance).

    max

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  6. Geez Max. There are a lot of smart folks on this site who enjoy building guitar effects. I'm no electronics expert and enjoy gaining some knowledge of electronics related to my hobby building the effects on this site thanks to Mark, Miro, Alex and Zach as well as other contributors here. One of the reasons I use this site is that it is at the perfect level for me for this hobby. I can appreciate some of your advice/contribution here but I'm not looking for an engineering Ph.D level debate on the in/outs of these effects. I can't speak for the guys that run this site as I am a user and not a contributor but this site seems to avoid such deep debates and intricate theory. I would suggest looking for another site if this one does not meet your needs.
    Thanks Zach for the layout and the many others you've posted to keep this site going! Your time invested in this even while pursuing your doctorate is admirable. Let's just let this discussion die here and move on the fun and enjoyable aspects of these builds.

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  7. Dear ???,

    you are absolutely right. This site is about valuable information carried together by people in their free time and those people have my respect for their work. I've been playing around with JFETs for ages it is one of the things that got me started in building guitar related equipment (unrelated to what I do during the day). The majority of effects presented here are clones of pedals from renown companies and that is perfect if you are looking for that information. From time to time someone adds his/her own idea/pedal - nothing wrong with that. But in this particular example the circuits are half-baked and not really up to the standards of the other circuits on this site. I regard this valuable information. I posted this to save people the time and hassle to build such a circuit and be disappointed with the result. I posted details, a schematic and simulations of an improved version to provide something constructive to the discussion/site.

    I am a little sad to read your response to this now. You are telling someone who constructively contributes to stop and look for another forum? And if I understand you correctly because detailed discussions interfere with your approach to your hobby?

    max

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    1. max. i'm going to start off by saying this. i have no problem and support discussion on builds and concepts, but what i do not support or approve of are comments that are condescending without warrant. your initial comment is incredibly condescending and insinuates a complete lack of knowledge on my part, which is completely inaccurate. i am rather well read on tube amps. if you readVacuum Tube Circuit Design: Guitar Amplifier Preamps and Vacuum Tube Circuit Design: Guitar Amplifier Power Amps Richard Kuehnel you'll see what i'm talking about and where i'm coming from. i have read Merlin Blencowe's Designing Tube Preamps for Guitar and Bass, so i'm well aware of his work.

      as far as the pdf i posted is completely relevant to the comments you posted about tube amp distortion. if you're talking about vintage amps (vintage Fender Deluxe, Vox AC30, Marshall plexi, etc.) yes you're getting power tube distortion only, at high volumes. this means you only get it when the amp is cranked and loud. hence most of your distortion comes from your preamp tubes and power inverter tubes. this is the reason i say that power tube distortion isn't relevant. if you are using a preamp pedal you will mimic the distortion characteristics of the preamp distortion from said amp, and can drive your amps power section into distortion if desired. if you have a SS amp you will get SS distortion, if tube you can get tube distortion. i think you're looking at this as an amp replacement and that it's supposed to fully replicate the actual amp, which is not the case.

      you must also take into consideration a few other things. first, you will never truly mimic another amp, tube or otherwise using a pedal or a different amp. you may get similar characteristics in distortion and tone shaping. secondly, FETs do no and can not truly sound like tubes regardless of how much voltage you throw at the circuit. there are flaws in tubes that give them their distortion characteristics that can not truly be emulated.

      i've never said i engineered this circuit, in fact i said that there has been no breadboarding or testing at all. but, as i stated before taking concepts that work, and using knowledge of basic concepts can be applied to similar situations, which this is. while there are other ways to accomplish the same goal, if the results yielded accomplish the goal desired then it's ok. case in point, i have a race car that i race track. if i want to go faster there are multiple ways i can accomplish this goal. i can either remove weight, add power, increase power transfer, etc. is one way better then the other? no. is one easier then the other? it depends.

      to be frank and honest i'm not annoyed at your comments and suggestions. what i'm annoyed at is the tone and condescending character of your first post to me.

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    2. Dear Zach,

      I am sorry if the tone of what I written came across harsh. From the way you assessed the Acapulco gold and answered the questions of people looking for the AD200B Mk1 schematic I may have gotten a wrong impression. I would be happy if we can leave that discussion behind.

      I have suggested to add capacitors to the JFETs to limit the high frequency response and emulate the miller capacitance. In the current state each JFET adds too much high end and high end distortion. ROG details it in the fetzer valve revisited, though adding those caps from gate to gnd is not optimal. In the input stage it loads the resonance peak of the guitar/bass pickups und shifts them (old Valco's did that on purpose, but not the orange). After the gain pot it acts like a variable low pass depending on the position of the gain pot. Paralleling those caps with the drain resistor avoids both effects. Here simulation is really handy to come up with the correct value for the cap.

      max

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    3. agreed max. i didn't mean for things to get out of hand. i always say that one of the worst things about talking through text is that you can never tell someones inflection or real meaning, and i think that's really what happened. so as far as i'm concerned, we're all good.

      so onto the good stuff. i definitely see what you're saying about that. right now there are 220pF caps from gate to ground, the fetzer valve concept. i don't have my breadboard atm due to being away and working on my doctorate, i part of me was hoping that for these some other gunho guys would want to take up the challenge and work on getting things right.

      i'll try to breadboard it up when i get home and run some tests to try and get things sounding right. seriously hope there's no hard feelings man. as i say to everyone, once you're here and part of the community we're brothers of the iron.

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  8. Beside all discussion: i am quite sure that the signal ends at drain of q1. Am i mistaken. Dead End?

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  9. Are there any updates on this circuit?

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  10. Now that we're all friends here... I built this thing today with limited success. Tried it with some K30As and 2N5485s. I know very little about jFET designs, apart from the articles I've read on the fetzer and such, but I'm left here with a super quiet anti-distortion with no time to breadboard, so just wanted to chime in: this needs more work.

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