AX84 BBS New Threads as of Mon, Sep 01st, 2014 @ 04:58:12 Amp Parts and KitsDoberman Music Products, LLC offers a variety of parts and kits A stab at a Daisycutter(by Borgar Dahle) Hey. for some time i wanted to build a tube amp. I've been messing with it for a while, but i wanted to have some results before posting. I'm an electronics technician, but i have little experience with tubes or audio for that matter. After having my attempt at a Daisycutter shelved for a solid two months, i got it out again. I was having some crazy oscillations last time and i didn't know here to start. Not having a scope at my residence didn't help. I figured I'd just remove the tonestack and see, i had a hunch i messed that up somehow. Sure enough, it worked. a lot of hum though. No shielding what-so-ever and the heatersupply runs right by the input, still a prototype i suppose. I'm not really knowledgeable when it comes to guitar, tone or amps. but i like what I'm hearing so far. I'll get some of my guitar friends to check it out later. the parts is whatever i had from my failed marantz7c build, components from work and of course,Ebay. Nothing was chosen for tonal quality. tubes: 2x Chinese nobrand 7ax12's. just reads: 7ax12 china. 2x russian NOS 6p14p with CCCP branding. Powertransformer: Toroidal 55W supply. Hugely overdimensioned for a marantz preamp. still over overdimensioned for an 18W daisycutter. output transformer: OUTPUT TRANSFORMER 22W 6600 CT. the ebay listing mentioned fender but it looks brandless. the rest is vishey polyester film caps and resistors of different origins, sockets and screwterminals ect. from ebay. I'm powering it through a fusebox I built with 2x 5A automatic fuses, for projects involving mains. when I'm done it will have the regular glassfuse, obviously. Pictures: <a href=" " target="newwin1409561892">[link]</a> Now i will have to read up on building a chassis. I'm not sure i even want a tonestack at this point. Maybe a single pot one, with a pullout switch to bypass. that would be cool. any comments and suggestions are welcome.Sun, 31 Aug 2014 14:11:57 -0400 A little recording sample.(by JeffW) I have been slowly learning how to use Studio One and trying to get back to recording after a long gap. Seems like good software so far. The drums are from Studio One, bass is direct using built in tones, the guitar is a tele I built and the amp is a Kustom Defender that is modded then into a 2x10 open back loaded with Jensen C10R's. Mic is an EV Cardinal. Here is the clip. <a href="" target="newwin1409561892">[link]</a> Sun, 31 Aug 2014 11:13:59 -0400 Return To Solid State(by Douche Baggins) Downsized from a 3/2 SFH to a 2/2 condo four months ago and had to downsize my guitar volume as well. I'd been looking at a few modeling amps for the past 6 months and was near purchase on a Fender Mustang 3 however, I didn't want to spend that much. I went to Sam Ash today to pickup this: <a href=" " target="newwin1409561892">[link]</a> and ended up trying out and bought this amp: <a href=" " target="newwin1409561892">[link]</a> This amp exceeded my expectations in many ways. The most impressive is the sound doesn't crap out, fade or pulsate when multiple effects are used together. Even, with distortion plus multiple effects together it holds true. It doesn't do low gain very well, but medium gain is good and high gain is great. Big sound for 2 x 3" (stereo) speakers. Here's a couple vids: <a href=" " target="newwin1409561892">[link]</a> and <a href=" " target="newwin1409561892">[link]</a> It's easy to figure out and unlike the other modeling amps (including the Mustang 3) it doesn't have any useless stock settings. For $100 it's a lot of fun and should make a good recording amp.Sun, 31 Aug 2014 22:31:31 -0400 schematic for 8 to 12 watt class A EL84 amp(by David Ray) I have a Laney LC-15R chassis complete with the power and output transformers still mounted. The main circuit board is trashed because of one of the plastic EL-84 sockets arching and Charing the board. I also have the reverb/effects board still mounted in the chassis, but the wires have been cut from the main board. I was hoping to reuse the ebd trannys, chassis, etc... To build a 10 or 12 watt class A amp and mount the new board in the chassis. I can read schematics fairly well and have rudimentary soldering skills and the desire to try to build my own amp to play through. Any ideas especially schematics for something between 8 to 12 watts would be a big help, so anyone who has done something similar help me out here. Thanks in advance.Mon, 01 Sep 2014 04:55:10 -0400 KT120 Driver(by tooltime) I'm designing a bass amp with a push-pull quartet of KT120's. I was wondering if anyone has experience with these tubes, and what was used to drive them. -Would an ECC99 or 12BH7 as an LTPI be a good driver? -Would a 12AU7 be 'better' than the ECC99 / 12BH7? -What about a PI earlier in the circuit, with an ECC99 after it as a gain stage/driver? I haven't used the ECC99, it seems like a good tube for these big tubes. For simplicity reasons, I was looking to avoid a cathode follower after the PI.Sun, 31 Aug 2014 10:38:27 -0400 New Vishay MKP 20uF & 30uF 700V low profile film caps(by CChurchill) for sale: Brand new Vishay metalized polypropylene film capacitors in the following values: 20uF/700v <a href=" " target="newwin1409561892">[link]</a> <a href=" " target="newwin1409561892">[link]</a> 30uF/700v <a href=" " target="newwin1409561892">[link]</a> <a href=" " target="newwin1409561892">[link]</a> High Voltage rating, low ESR, and compact size make it a good option for DC filtering in amps where board and chassis real estate is a consideration. Plus, they look cool. Here's the deal with the 4 leads... These caps with 4 leads have about half the ESR (Equivolent Series Resistance) of the same capacitors with 2 leads. The leads at each end share continuity with the other(at the same end). In other words, (in theory)you could attach one lead at each end into an appropriate circuit and have a functioning capacitor. That is probably the most importand distiction and if you want anymore info, datasheets are available. I hope that clears up any confusion someone may have who isn't familiar with this style. Wed, 27 Aug 2014 12:08:35 -0400 5 Watt Carbon Film resistors 20uF 100V film Cathode Bypass cap(by CChurchill) for sale: New Cornell Dubliner 20uF Metalized Polypropylene 100v capacitors - axial leads. great for cathode bypass. I have 3 I can sell for $10 a piece <a href=" " target="newwin1409561892">[link]</a> Brand New 5 watt Carbon Film resistors from KOA Speer. These are the same resistors re-branded and sold in Audiophile markets as Kiwame. They have better thermal noise performance than metal film. They are flame proof and are rated for 800V. I can sell some of the stock I have. I have the following values: 100K 4.7K 2.7K 1.5K 1k (a few) 820 I'll sell them for $1 a piece (plus shipping) in sets of 10 if anyone is interested <a href="" target="newwin1409561892">[link]</a> Wed, 27 Aug 2014 11:36:47 -0400 Bone ray tone stack question(by reverberocket) Hello guys Some newby questions. I want to change my single tone controle in the bone ray stack. Do I put the volume afther te tone stack or leave it like the tweed infront of the stack ? Will a12ay7 in parralel be enough to push it. Thanx in advanceThu, 28 Aug 2014 12:37:46 -0400 Need help identifying mistake(by LuptonM) Hi all, I am currently building a P1800 from ampmaker. I've completed the soldering but when doing continuity checks I have failed in one place. I don't have enough electronics knowledge to determine where it has failed. The amp has a switch which can select either single ended, push pull or push pull plus modes. When push pull is selected I fail the continuity test on the left testing point but pass on all the other output modes. The general layout of the amp is found here <a href=" " target="newwin1409561892">[link]</a> On this page I have failed the part called "Checking the Output switch" There are two test points, one on the left and one on the right. More info on wiring the output switch is on this page <a href=" " target="newwin1409561892">[link]</a> under "Connecting the Output switch" From this diagram can anyone tell where my mistakeis likely to be? Cheers Marc Note: I think the maker of the kits is on holiday for a couple of weeks hence me posting on the forumWed, 27 Aug 2014 03:24:41 -0400 need a quality iron(by Dan Moos) I've built all my amps with a cheap radioshack iron. It has worked ok, but I feel I d ao enough of this stuff to want a quality tool. Suggestions? I do enough PCB stuff along with the point to point turret stuff to need a wide and selectable heat range. Low power has been my chief complaint with the current iron ( it's a 40 watter)Tue, 26 Aug 2014 13:28:32 -0400 5W SE with Blues Preamp(by Pete Davis) I'm very interested in building the 5W SE power amp with the blues pre-amp. From what I've been reading the 6U8 is suitable replacement for the 7199 (at a small fraction of the price). Is that still the general thinking? The power transformer specifies a 2.5amp rating for the 6.3V. Using these values: 6U8 - 0.48 amps 12AU7 - 0.3 amps 6V6 - 0.45 amps Would a 2 amp rating on the 6.3V be sufficient? It's not a huge deal, but it might save me about $10 on the transformer. I was planning on going with the EDCOR XPWR136 ($32.46 US). Also, as B+1 is unused in this configuration, do I need to alter the RC filters at all or just leave things as they are and just not connect B+1? On the preamp, would there be any value in having a rotary switch to use different types of LEDs (or even non LED diodes) for the parallel stage? Different colors. Maybe 2 1n4004s in series, an HER106, stuff like that? Seems like you might be able to mix things up a bit there. My thinking was to have a rotary switch for each of the two diodes. Would there be any danger to doing this (possibility of damage in the brief time switching between diodes). Finally, does the circuit require any modifications to swap out the 12AU7 for other tubes or can you simply plug and play with the 12A?7s (where ? = T, U, V, X, Y)? I like being able to tweak things, so if the circuit would need changes to handle that, I'd like to put in switches or whatever I need to support the changes. Sun, 24 Aug 2014 14:59:09 -0400 yellen-on-fed(by Kursad K) The forum rules clearly state that any political discussion is not welcomed, but, maybe we could consider this to be technical subject (as technical as economics could be, I have no idea). In short I wonder what does this mean: <a href=" " target="newwin1409561892">[link]</a> and what has been happening in your side of the world during the last 7 years or so, because apparently nowadays it affects almost everybody on the earth. Thanks for any comments and remember to keep it technical..:) KursadTue, 26 Aug 2014 12:56:10 -0400 Hybrid 1 Watter (not mine)(by Douche Baggins) Did a YouTube search recently for 1 watt amps and this: <a href=" " target="newwin1409561892">[link]</a> is among many posted. Here: <a href=" " target="newwin1409561892">[link]</a> is the schematic/build link. Build pics: <a href=" " target="newwin1409561892">[link]</a> Cheers to nzCdog for the build, video and guitar chops.Thu, 21 Aug 2014 21:29:39 -0400 OT impedance match(by BaltorTinazli) Hi; I have an OT which has 18,4k primary impedance instead of 22.5k with 8 ohm speaker. Is it ok or any disadvantages with it? I have bought five sets of them 4 years ago to build fireflys. But i could start building it yet:) Voltage ratio is 1:48. Impedance ratio is 1:(48)=1/2304====>2304*8ohm=18,4k. It has center tap also. I have built HO,20WPP amps before. Great site great people.Thanks. BaltorThu, 21 Aug 2014 07:03:19 -0400 Dual Concentric 1 meg Pots?(by The Ballzz) Hi All, This is my first post, so please be gentle. I have searched for 1 meg dual concentric pots and found them to generally be made of "UNOBTAINIUM", however, I have finally found a source to have them manufactured in reasonable quantity at a fair price. I'm wondering if anyone, besides me, sees or understands the potential use(s) for such a pot? I have not yet placed my order and am exploring interest in any of these at a reasonable cost. This is not intended as a "for sale" post simply seeing if anyone would want a few of these if I were to acquire100 or so of these. If no interest, I will likely not make the investment. Thanks In Advance, Gene Thu, 21 Aug 2014 08:23:38 -0400 Passing the time(by Ken Graves) On my job I have to stay alert but there's not much activity for me. So, when I don't have a project going I need to keep my hands busy. So I bought some mild steel from Home Depot, some files and wet or dry and went to work. Since this is mild steel and can't hold an edge long I call it a letter opener. <a href=" " target="newwin1409561892">[link]</a> <a href=" " target="newwin1409561892">[link]</a> When my daughter in law saw it she asked if I could make a letter opener for her so . . . <a href=" " target="newwin1409561892">[link]</a> <a href=" " target="newwin1409561892">[link]</a> My next couple of tries will be with carbon steel to be hardened so they will be sure enough real Daggers. One will have a Rosewood handle, the next will use Bocote. Tue, 19 Aug 2014 15:41:07 -0400 P1 eXtreme transformer question(by aeronaut) Greetings, Has anyone played around with other transformers for the P1 eXtreme? Thinking of doing it for a first build, and it looks like one can get an Edcor CXPP30-MS-5K for about the same price as the Hammond 125ESE output transformer. The Edcor is rated at 30W, 20 Hz to 20 kHz, and has a 5k primary and 4, 8, and 16 ohm outputs. Seems like a lot more iron for the money, and rated to handle the bigger tubes the P1 eXtreme can take (perhaps a little shy for the KT88, but much closer than the Hammond's 15 W). Might be more than one needs, but for the same price, seems like a no brainer. Any concerns or potential problems? Or is the 30 Watt push pull rating the same as a SE 15 Watt because in push pull it only conducts part of the time? Even so, the better frequency response is still an upgrade, albeit perhaps not a useful one. Can't link it, but go to, menu bar class X, item push-pull. Seems to be way better value than the hammond tranny. Regards, Martin Tue, 19 Aug 2014 21:49:41 -0400 Help! How is this possible?!?(by tooltime) <a href=" " target="newwin1409561892">[link]</a> ^^Watch the video first. I am getting a hum/buzz that seems to come from PI area. It does turn down with volume, but I dont believe its actually coming from the preamp. The amp looks like a mess b/c I have spent many hours working on it. I have tried... -Physically moving OT further away from preamp -disconnecting the OT and temporarily wiring in another one outside the chassis so I could move it around to see if anything changed. -shielding signal wires -humdinger -new PT -all new tubes I don't understand what is causing the voltage to appear on the fiber board, this baffles me. How can a non-conductive material have an induced voltage?? But somehow voltage is being induced which I believe is the cause of the hum that I can't eliminate. This is a clean amp, I am using the LTPI as a mixer of the 2 preamp circuits (a 12AX7 channel, and an EF86 channel) I have built several of these with no issue. Any help is greatly appreciated, I don't have much hair left to pull out.Wed, 20 Aug 2014 10:37:57 -0400 Soldering to turrets(by David Staepelaere) Here's an old instructional video on soldering to turrets... <a href=" " target="newwin1409561892">[link]</a> It certainly has good information for people just starting out, but it also has a few details that might be helpful even for more experienced folks. Tue, 19 Aug 2014 22:27:42 -0400 Some questions before I build P1-eX(by JayWalker) Hey guys. I'm interested in building the P1-eXtreme amp, but I have some questions. I'm not buying a kit (I have many parts laying around) but I want to make sure the things I am buying will be suitable. I'm planning to use a 6L6GC power tube, will this OPT be suitable for B+ of around 350v (plus or minus, depending on power trans)? <a href=" " target="newwin1409561892">[link]</a> I ask because I'm still a little fuzzy on OPT theory, but I think 5k is almost perfect for this, right? With that transformer, the anode current would be 70ma for 24.5 watts dissipated @ 350v. The OPT says 15 watts rating, is that referring to max OUTPUT power or the max power that can be put through it? Should I go for a bigger OPT (or perhaps a higher impedance, as the case may be). The Hammond OPT specified for this project is also rated for 15 watts which makes me think it's OK. Given the above stated, what would the expected output power be? I've seen 50% of anode dissipation quoted, so maybe ~12 watts? I've got some other ideas but I'll start here to make sure I'm not getting ahead of myself. Any help is appreciated.Sun, 24 Aug 2014 20:01:04 -0400 67? Gibson Skylark (new project)(by Kevoid) It took a while, but I finally got an all tube amp project to work on. It's an old Gibson Skylark. Here's a link to one just like the one I have: <a href=" " target="newwin1409561892">[link]</a> It had a really bad hum and the 3 stage (10uf, 10uf, 20uf) filter cap values where way off. I change it out using 2 new NEC 10uf caps and 1 NEC 22uf cap. The 22uf cap read a little over 21uf so I figure it's within the percentage rating of a 20uf cap. Anyways, no more hum. NOW, comes the learning experience... It's really thin and bright sounding, but it's my understanding these amps came from the factory this way. I am hoping to get some help with understanding the tube biasing/pins used in this amp and just overall any thoughts/ideas to help me learn the most I can from/about this amp... I am still heading toward my goal of building my own tube amp(s) one day. But, for now, I am hoping to thoroughly understand this amp... Really looking forward to see what you guys have to say. I know this sight was great when I was working on the 90's solid state Princeton... Thanks again, KevinFri, 15 Aug 2014 17:17:35 -0400 Speaker wire from 120W head into 2x12(by dannyBwheeler) Hey builders. First post on here, I recently replaced an old cheap radioshack solder iron, and have discovered new things to fix with the newfound power of solder gun and a hakko fx. I've played through a friends AX84, and look forward to making one soon. Before I go off on that project, I should probably fix what I got. I've got a nice Ampeg SS140C combo, and one speaker cuts out more than it's in. Since it's almost 30 years old, I'm assuming it just needs to wire. It's a 1/4 phone to slide-ons +/- . Where's the best place to get wire? Each speaker is 4 ohms, and here's a link to the schematics if anyone needs it to answer the question: <a href=" " target="newwin1409561892">[link]</a> Thanks guys!Tue, 19 Aug 2014 05:52:03 -0400 Less work?(by steve25) I was on my way to get my hair cut today and on the way in the barber shop door I though to myself well, I am 59 now and half bald so should I not get charged half price for a hair cut? I mean it's half the work, half the sweep the floor clean up time right, or how about throwing me a bone on a shave or double up on slapping on that after shave stuff they toss on ya!Wed, 27 Aug 2014 06:18:50 -0400 Thinking of "Wreking" my SimplePre-20WPP(by Darren Porter) I saw another thread on here about converting a SimplePre-20WPP amp into a 4-4-0. After looking at the schematics, I see that they are very similar. When I built my Simple20 I even had the forethought to wire in two extra tube sockets just in case I wanted to add an effects loop and a 1-tube reverb, so I think this will be cake. A question though... I see the 4-4-0 has much lower voltages on the 12AX7's than the 20WPP design. Do I need to lower my voltages or will I be ok using them as-is? Would I need to adjust any values anywhere if I did leave them alone? How practical would it be to wire a switch in to make it a two-channel amp? Basically, a Deluxe and a 4-4-0 in one package? Or should I just wire-up a 4-4-0 preamp and feed my Simple20 either through the main input or through an effects loop return?Wed, 13 Aug 2014 12:46:45 -0400 Lower Watt 6V6/Octal Alternative?(by Douche Baggins) Looking to reduce output for my P1 without dropping plate voltage (275v. I know a 6K6 is one option, but I am hoping to get around 1 to 2 watts output in Pentode. I've tried several types(mU) of preamp tubes, but doesn't lower volume enough and effects distortion too much.Thu, 14 Aug 2014 11:33:19 -0400