AX84 BBS Recent Posts as of Fri, Oct 24th, 2014 @ 09:37:52 http://ax84.com Amp Parts and KitsDoberman Music Products, LLC offers a variety of parts and kitshttp://shop.dobermanamps.com RE: Weber-esque 5F4 using '60 Conn Organ Chassis(by PhilS) John, Without a voltage chart and a schematic, this discussion is difficult. If you built a standard circuit, please name it and point me to a link for the schematic you used. A full set of voltage readings is also essential. You can just post them here as ordinary text. To make it easy to read, list one tube at a time and then one line for each pin number. Like this: V1: 12AX7 p1, 200V p2, 0v p3, 1.2V etc. Skip the filament pins. We'll assume they are OK since you are getting sound and volume. Also, the voltage readings at the rectifier, and at the + side of each filter cap. This is the B+ ladder -- the power supply. List as B+1, B+2, B+3, etc. Even without the schematic, the voltage readings alone will tell a great deal. Meanwhile, my thinking runs in this direction. Tubes are biased way too hot, maybe double what they should be, but I can't tell that for sure without the plate voltage and bias voltage. I am guessing plate voltage is around 380, but I don't want to guess when I can get actual. The other possibility is the design isn't appropriate in respect of your wants. For example, the grid leak resistors on the power tubes need to be reduced in value, or the PI is putting out too much drive signal; things like that. Are there grid stoppers on the power tubes? All this is on the schematic. Please see what you can do. Voltage readings are essential. Schematic is important too, but second to the voltage readings. If you are simply able to name the circuit, I can work with a schematic that may not be exact. Right now, your audience is still quite blind. You've come this far, I want to suggest it isn't much further to tweak this to your liking.Fri, 24 Oct 2014 08:11:01 -0400 http://ax84.com/bbs/dm.php?id=486971 RE: AX84 1x12 Tools Needed(by ledzepp007) Great advice. After listening to folks here, I'll probably get a benchtop router table, drill press, jig saw, and sander. I'll probably just have Lowe's cut lumber down to size or pick up a cheap circular saw later. In terms of amp design, I've decided to do an ultra simple champ-like build first. Then, I'll probably tackle and 18-watt. Then the AX84 4-4-0. Then a full-bore TW Express. Then... ? Maybe a Dumble clone? I guess it kind of depends on how well the initial projects go. Luckily my fiance is better at putting things together than I am (she says, "I like puzzles" and proceeds to effortlessly build things--we shall see how well she does with electronics). This weekend, I'm going to build a small workbench that will fit in the apartment and probably pick up a new soldering iron, sander, and router table. It's all exciting. My family is really, really, really not the DIY type and I was never taught any handyman skills. So, I really appreciate everyone taking the time to be helpful. Fri, 24 Oct 2014 07:58:55 -0400 http://ax84.com/bbs/dm.php?id=486970 RE: AX84 1x12 Tools Needed(by Darren Porter) <div class="quoteblock" >On 10/24/2014 @ 05:25, ledzepp007 wrote : : : THANKS ALL! : : And yes it is I, the guitar amp and DIY noob from 18watt. I am collecting information from you helpful gents from all over the web. : : So, with a compact table saw (would have to be a bench top model), a 3/4" dado blade, and a fabricated jig I could make box joints? : : Here's what I'm thinking: : : 1) Compact, bench top, table saw : 2) Plunger router : 3) Jigsaw : 4) Sander : 5) Wood glue : 6) Wood screws : : Would that be a good start? Thanks! -- </div> In my experience with bench-top table saws... forget it. Get a circular saw with a good blade and a fence (I used a long level with clamps) to get a nice straight cut. Buy your wood in easy-to-handle sizes like 2x4 panels of plywood and 1x12x4-foot or 6-foot planks. Bench-top saws will offer you nothing that a circular saw won't do for you, except dado's but if you are getting a router, you can easily do those with that. Bench-tops are a real pain to get accurate cuts with and ripping long pieces accurately and _safely_ is nearly impossible. This is my experience with them, others may feel differently. Start by building with simple joints. Butt-joints with corner battens are plenty strong enough. I like to do biscuit joints too, but yeah it's just something else to buy. You can do dowels simply enough but nothing is as easy as the corner battens and you don't need any specialized tools or jigs to do them. Finger joints (box joints) are hard to master. I'm still working on it... wasted a lot of lumber in the process... IMO best done on a router table with a jig. If it were me, I would get a decent router table and use a circular saw over getting a bench-top table saw. By the way, what did you decide on for an amp build?Fri, 24 Oct 2014 07:24:48 -0400 http://ax84.com/bbs/dm.php?id=486969 RE: advice on building and designing amps for a living(by stringbend) Clearly you are very passionate about this. As a person who has pursued greatness and failed, I applaud you. You have asked for, and received good, honest advice - even when it isn't very pretty. I won't offer more of the same. As you are going into this with eyes wide open, fully cognizant of the associated risks, I'll simply offer you the best of luck. Fri, 24 Oct 2014 07:04:14 -0400 http://ax84.com/bbs/dm.php?id=486968 RE: AX84 1x12 Tools Needed(by stringbend) <div class="quoteblock" >On 10/24/2014 @ 05:25, ledzepp007 wrote : : 1) Compact, bench top, table saw : 2) Plunger router : 3) Jigsaw : 4) Sander : 5) Wood glue : 6) Wood screws : : Would that be a good start? Thanks! </div> Yes, that would be a good start. Add multiple clamps, if you don't already have them. A power drill is damn near essential. (A spade bit will create your jigsaw pilot). A circle cutting jig for speakers. (Can be homemade). In truth, a strong router with clamped straight edge could do what that table saw will do. (but I wouldn't). It's also worth noting that a heavy duty router can be cumbersome when rounding over, if you aren't using a router table. It can even be dangerous IMO. A smaller, lighter type is better for handheld use. I prefer biscuit joints, but that's another tool. Easy as pie to use. Lots of screws and cleats don't appeal to me, but I can't pretend it's essential. Clamps. Did I mention lots of clamps? Fri, 24 Oct 2014 06:14:30 -0400 http://ax84.com/bbs/dm.php?id=486967 RE: Weber-esque 5F4 using '60 Conn Organ Chassis(by Jonathan Haynes) <a href="http://i161.photobucket.com/albums/t238/kc7fys/20141014_135432_Tatum_St1.jpg " target="newwin1414157879">[link]</a> <a href="http://i161.photobucket.com/albums/t238/kc7fys/20141024_072849_Tatum_St1.jpg " target="newwin1414157879">[link]</a> <a href="http://i161.photobucket.com/albums/t238/kc7fys/20141024_072956_Tatum_St1.jpg" target="newwin1414157879">[link]</a> Fri, 24 Oct 2014 05:35:36 -0400 http://ax84.com/bbs/dm.php?id=486966 RE: Weber-esque 5F4 using '60 Conn Organ Chassis(by Jonathan Haynes) A very understandable request, Phil. I posted that when I was fairly fed up with the project and subsequently hung it up in the basement rafters with other unfinished detritus. But I'm awful close to success with this one. At present I am using a pair of 6V6GT power tubes (I pulled this pair from a nice-sounding and loud Hammond M3 out in the garage. I have others 6V6 tubes, but only have ONE 6L6 available. *Its partner got a crack near the base and has been retired.*). The tube rectifier is a 5U4GB NOS by RCA. I looked at all the hulks here and in the basement and didn't find any WU4GB or GZ34 tubes to use as comparison. There have been shouts to check voltages between windings of the PT and here they are, measured again this morning. RED-766VAC GREEN-12.87VAC YELLOW-4.88VAC LINE VOLTAGE 113.4VAC Measured across the windings. I have a variac and a current limiting device but did not use them in the measurements above. The red wires go to the plates of the rectifier, pins 4 and 6. The yellow wires go to the filament, pins 2 and 8 of the tube rectifier. The green leads go to the power tube filaments and the 12AX7 filaments all parallel-in that order. My bias voltage is grabbed from the rectifier high voltage and dropped with resistors and a pot as follows: resistors equalling 82K (-29.5VDC~38VDC range with the 10K pot) I now have 40/41mA plate current, giving me about 15.1w plate dissipation by using the "Uncle Doug" method of measurement. The DC resistance on each side of the OT measures 199.6 and 246.5 ohms. The OT, incidentally, is a K-58459 from the same Woodward Schumacher that made the PT in this former Conn organ. I've also been using a tone-generator as a signal source (Behringer CT-100 on +4dBu @1khz and 440hz), so when I plugged in an actual guitar ('78 Greco LP with those goofy Dimebucker pickups), it was a lot of fun to actually play through this thing. To be blunt, I don't like the amp at all. Ha ha. It's really growly and I can't seem to get a clean sound at all--so I know I have some experimentation ahead to get it to produce some sounds "worthy of woodworking." But still, I'm thrilled that my first amp actually, um, amplifies. What further measurements can inform this conversation in greater detail? I will post them. I am looking for my 'home forum' and don't really want to windowshop any longer. Here are photos, also. Generally speaking my questions are: have I properly utilized the voltages this PT has to offer in mating it with this particular amp design? Why can't I get a clean tone when it appears I'm providing the proper voltage to the 12AX7 preamp tubes? Am I OK using 6V6GC tubes until my 6L6 tubes are sourced? How about the rectifier tube? [URL= <a href="http://s161.photobucket.com/user/kc7fys/media/20141014_135432_Tatum_St1.jpg.html][IMG]http://i161.photobucket.com/albums/t238/kc7fys/20141014_135432_Tatum_St1.jpg[/IMG][/URL] " target="newwin1414157879">[link]</a> [URL= <a href="http://s161.photobucket.com/user/kc7fys/media/20141024_072849_Tatum_St1.jpg.html][IMG]http://i161.photobucket.com/albums/t238/kc7fys/20141024_072849_Tatum_St1.jpg[/IMG][/URL] " target="newwin1414157879">[link]</a> [URL= <a href="http://s161.photobucket.com/user/kc7fys/media/20141024_072956_Tatum_St1.jpg.html][IMG]http://i161.photobucket.com/albums/t238/kc7fys/20141024_072956_Tatum_St1.jpg[/IMG][/URL] " target="newwin1414157879">[link]</a> Thanks!Fri, 24 Oct 2014 05:31:21 -0400 http://ax84.com/bbs/dm.php?id=486965 RE: AX84 1x12 Tools Needed(by ledzepp007) <div class="quoteblock" >On 10/23/2014 @ 19:34, Darren Porter wrote : Hey are you the one I was helping out over on 18watt.com? I'm MakerDP over there. If so, welcome aboard! If not, well welcome anyways! lol : : Absolute bare minimum to get it done is some kind of a saw, a screwdriver and a ruler. But for me, that would be an exercise in total frustration. : : Bare minimum I would consider for myself doing it: : : - A circular saw to make the sides, top, bottom and baffles. : - A jig-saw for the speaker cutout. : - A drill to pre-drill your screw holes. : - Some sandpaper to ease the rough edges. : : It's probably safe to assume you have the basics like a screwdriver, tape measure, etc. : : A router with a round-over bit would take it to the next level and make it look "professional." : : If you set up some kind of fence with clamps to keep your cuts straight you can probably even get away with just having a jigsaw to do all of the cuts you need. unless you can do a nice straight cut with a jigsaw without a fence. I sure can't. : : You can paint it, stain it and shoot it with some spray finish, or just leave it natural. : : For joining your box, you can just buy some 1x2 cleats and glue screw them in from the inside. If you are concerned about them changing the volume of the box then just add 1/2" or so to the depth and call it good. : : I just made one loosely based on the AX84 design out of Poplar and I really like it. For my 18-watter I like it closed-back with a small gap in between the rear panels for porting instead of the round hole. For my AX84 Simple Preamp/20Watt push-pull amp, I like to take the smaller rear panel off and have it "open backed." : -- </div> THANKS ALL! And yes it is I, the guitar amp and DIY noob from 18watt. I am collecting information from you helpful gents from all over the web. So, with a compact table saw (would have to be a bench top model), a 3/4" dado blade, and a fabricated jig I could make box joints? Here's what I'm thinking: 1) Compact, bench top, table saw 2) Plunger router 3) Jigsaw 4) Sander 5) Wood glue 6) Wood screws Would that be a good start? Thanks!Fri, 24 Oct 2014 05:25:43 -0400 http://ax84.com/bbs/dm.php?id=486964 RE: Adventures in Digital Control(by Stephen Keller) They would form a half-wave rectifier if wired in parallel. As long as the signal voltage at the anode voltage stays above the cathode, it wouldn't matter, but they would clip if the signal ever dipped below cathode potential. If you take two and connect anode to cathode, then it won't matter. If the anode of one falls below cathode potential and shuts off, the the cathode of the other has fallen below anode potential and it starts to conduct. Switching distortion is the concern, but I have no insight on that matter, having never tried this. StphFri, 24 Oct 2014 05:15:20 -0400 http://ax84.com/bbs/dm.php?id=486963 RE: Mic preamp phantom power(by steve25) sorry, the TL783 would be the way to go!Fri, 24 Oct 2014 04:47:14 -0400 http://ax84.com/bbs/dm.php?id=486962 RE: Adventures in Digital Control(by Chris Hurley) In thinking about this, if they act like a diode of sorts, won't putting them in antiparallel just make a full wave rectifier? Fri, 24 Oct 2014 04:10:46 -0400 http://ax84.com/bbs/dm.php?id=486961 RE: The fartiness has been found.(by Alva Goldbook) The easiest solution would be to remove C14a and C14b and replace with a 0.022uf cap. And this is going to be a little unconventional, but remove the C18 500pf cap. Replace it with a 120pf (mica) cap. You'll lose a little on the treble, but not much, and you'll get nice round and punchy bass, and you'll get a more balanced and well functioning tone stack. Here's the results of a simulation with the mod in blue. Bass, Mid, and Treble are set to noon. <a href="http://s27.postimg.org/w1bbthwcz/440tonestackmod.png" target="newwin1414157879">[link]</a> Fri, 24 Oct 2014 00:40:15 -0400 http://ax84.com/bbs/dm.php?id=486960 RE: The fartiness has been found.(by bullpeters) ok. I looked at the link and that seems to explain a lot. i will try a different tone stack, happy to see some suggestions. try to move the "dip' a little further along. many thanksFri, 24 Oct 2014 00:33:25 -0400 http://ax84.com/bbs/dm.php?id=486959 RE: The fartiness has been found.(by bullpeters) i am happy to change whatever. mostly interested in what you come up with. I wonder why i am unhappy with my configuration, given that many others are happy with theirs. do u think possibly its some kind of oscillation or feedback? There isnt any "one" note that oscillates, so i didnt go down that road. but why does everyone else love theres and mine really isnt the quite right? Fri, 24 Oct 2014 00:30:09 -0400 http://ax84.com/bbs/dm.php?id=486958 RE: The fartiness has been found.(by Alva Goldbook) I got curious about this, and so I ran a simulation of the tone stack in the 4-4-0. The results were surprising. Here, you can compare the tone stack to a Blackface and British amp. <a href="http://s23.postimg.org/p2i9musdn/440tonestack.png " target="newwin1414157879">[link]</a> Notice that the mid scoop is far lower than it is with the others. This means that less bass frequencies are boosted in the tone stack, producing very farty bass. And this was with the bass and treble controls turned up and the mids cut a bit. The tone stack is even worse with all 3 controls set to noon. Ack. We can solve this a couple of ways. We could just put a blackface tone stack in there (which sounds lovely with a clean sound, but is less appealing to *some* when cranked). But this means changing all the tone stack caps, plus two of the pots. Another possible option is I could run a few simulations and see if I can (kinda sorta) replicate a different tone stack without you having to change out the pots. Changing a couple caps might be less irritating. Fri, 24 Oct 2014 00:13:19 -0400 http://ax84.com/bbs/dm.php?id=486957 RE: my apologies (by Alva Goldbook) I should have familiarized myself with the 4-4-0 project. Thought you built a high octane. The 4-4-0 is quite similiar to a blackface preamplifier circuit, but with a British tone stack. The problem I see is with C14a and C14b. I would remove them and replace with a 0.022uf cap or a 0.047uf cap. Only use one cap here. The blackface amps used a 3.3M & 10pf cap here, but that was put there to accomidate the reverb circuit, which isn't a concern on this amp.Thu, 23 Oct 2014 23:23:45 -0400 http://ax84.com/bbs/dm.php?id=486956 RE: More bass or less bass?(by Douche Baggins) <div class="quoteblock" >On 10/23/2014 @ 19:41, bullpeters wrote : I sometimes cant see for looking, but there seems to be only one coupling cap at C11 thats .1. The rest, including tone stack are all .22. : Anyway thanks for the input, i will try some of what you have suggested and post back the result -- </div> .1, .22 uF ? If that's the case than that's the issue. They should be .01 and .022Thu, 23 Oct 2014 21:47:21 -0400 http://ax84.com/bbs/dm.php?id=486955 RE: Mic preamp phantom power(by DanGu) Do you mean lm317?? is it better than th tl783 for this? I dont think it could stand the 48Vdc of the phantomThu, 23 Oct 2014 21:03:25 -0400 http://ax84.com/bbs/dm.php?id=486954 RE: AX84 1x12 Tools Needed(by Mitch Markin) Darren and I were both replying at the same time, I see and said pretty much the same thing. I wouldn't worry too much about additional battens on the side corners changing the sound. This is a guitar cabinet, not hi-fi! I also wouldn't attempt to cut wood for a cabinet with a jigsaw, even with a guide. The blades don't cut square enough. Good square cuts are the key to this project.Thu, 23 Oct 2014 20:21:37 -0400 http://ax84.com/bbs/dm.php?id=486953 RE: AX84 1x12 Tools Needed(by Mitch Markin) It's hard to do cabinet work with limited space. Ideally you would have a table saw to build something like this. Even small ones take up a lot of space, though. There are aren't many parts to this cabinet. Maybe you could find a local woodworking shop that could cut the plywood for you. A shop that builds kitchen cabinets, for example. Lumber yards can cut plywood but they don't have the time or equipment to do it accurately enough. If you have the space, you can cut plywood quite accurately using only a power circular saw and a long straight edge. You clamp the straight edge to the plywood and use it to guide the saw so you get a nice straight cut. Don't attempt to use a circular saw freehand for a project like this. As for joining the plywood together, finger joints are best. But again you need a table saw or router table to cut them. I wouldn't worry about any fancy joints. Just butt the plywood together and secure it with lots of glue and screws. If you want to add additional strength you can glue and screw battens to the sides the same way the front and back has them. You can buy the wood for the battens already dimensioned to 3/4" x 1 1/2" and all you have to do is cut it to length. A power jigsaw comes in handy for making the round cuts for the speaker opening and trimming the battens to length. If you want the speaker opening to be a perfect circle, cut it with a router and some sort of compass attachment. So the bare minimum for tools would be a power drill with the appropriate bits for drilling and screwing and a power jigsaw. If you can't get the plywood cut to size you will also need a power circular saw, a long straight edge, a couple of clamps and something to support the wood while you are cutting it. If you plan to cover the cabinet with Tolex and use metal corners, you will need to round over all the edges. You need a router for that. Also a power sander comes in handy but it's not absolutely necessary. And you will need a staple gun to fasten the grill cloth. You also need some basic hand tools like a hammer and screwdrivers. This isn't a hard project to build. Just take your time and keep your cuts straight and square. Thu, 23 Oct 2014 20:13:55 -0400 http://ax84.com/bbs/dm.php?id=486952 RE: More bass or less bass?(by bullpeters) I sometimes cant see for looking, but there seems to be only one coupling cap at C11 thats .1. The rest, including tone stack are all .22. Anyway thanks for the input, i will try some of what you have suggested and post back the resultThu, 23 Oct 2014 19:41:52 -0400 http://ax84.com/bbs/dm.php?id=486951 RE: AX84 1x12 Tools Needed(by Darren Porter) Hey are you the one I was helping out over on 18watt.com? I'm MakerDP over there. If so, welcome aboard! If not, well welcome anyways! lol Absolute bare minimum to get it done is some kind of a saw, a screwdriver and a ruler. But for me, that would be an exercise in total frustration. Bare minimum I would consider for myself doing it: - A circular saw to make the sides, top, bottom and baffles. - A jig-saw for the speaker cutout. - A drill to pre-drill your screw holes. - Some sandpaper to ease the rough edges. It's probably safe to assume you have the basics like a screwdriver, tape measure, etc. A router with a round-over bit would take it to the next level and make it look "professional." If you set up some kind of fence with clamps to keep your cuts straight you can probably even get away with just having a jigsaw to do all of the cuts you need. unless you can do a nice straight cut with a jigsaw without a fence. I sure can't. You can paint it, stain it and shoot it with some spray finish, or just leave it natural. For joining your box, you can just buy some 1x2 cleats and glue screw them in from the inside. If you are concerned about them changing the volume of the box then just add 1/2" or so to the depth and call it good. I just made one loosely based on the AX84 design out of Poplar and I really like it. For my 18-watter I like it closed-back with a small gap in between the rear panels for porting instead of the round hole. For my AX84 Simple Preamp/20Watt push-pull amp, I like to take the smaller rear panel off and have it "open backed." Thu, 23 Oct 2014 19:34:56 -0400 http://ax84.com/bbs/dm.php?id=486950 RE: AX*$ SEL KT88 for sale(by automap68) Hi there Not really sure honestly. I did not have an exact price in mind. Like i said i have about $400 or so in parts alone, plus countless hours building it, painting, plus a really pricey NOS KT88. Im open to offers. If you would like please feel free to email me at bassk94@yahoo.com if you want to discuss it privately I thought this forum had PM,s but i don't see an option for that. Its been 3 years or so since I've been really active here. so feel free to email me i would also be happy to send you my phone number if you would like to call Thu, 23 Oct 2014 18:05:44 -0400 http://ax84.com/bbs/dm.php?id=486949 RE: AX84 1x12 Tools Needed(by ledzepp007) That would be "tools" not "told." Thanks lol.Thu, 23 Oct 2014 17:46:31 -0400 http://ax84.com/bbs/dm.php?id=486948 AX84 1x12 Tools Needed(by ledzepp007) Hi all, I apologize if this has been discussed (I have not found it through the search). I am just getting started with this and I thought I'd start with the woodworking side of things (speaker cab, head cabs) before I dive in to the electronic side. I have a cheapo Seismic 1x12 with a WGS speaker inside (the speaker is fantastic). It sounds ok, but it is an eyesore. I'd love to build the AX84 cab, but I have several limitations: 1) I don't have a lot of cash right now (saving for a wedding, just moved), 2) skill, 3) lack of space (live in an apartment in which there isn't a ton of space), and 4) no real woodworking skill (that I know of). The things I have going for me are that I'm pretty smart and I've been reading about wood joinery, different woodworking tools (saws, routers, etc). My question is this: in order to make the AX84 1x12, what is the bare minimum in terms of woodworking told that I would need, keeping in mind that they would need to be in a small work environment? I really appreciate your help in advance.Fri, 24 Oct 2014 07:58:55 -0400 http://ax84.com/bbs/dm.php?id=486947