AX84 BBS Threads with new messages as of Sun, Apr 20th, 2014 @ 22:01:36 Amp Parts and KitsDoberman Music Products, LLC offers a variety of parts and kits Existing PT good enough?(by Dustin LeBlanc) Hey everyone, I am considering transforming my Blackheart Little Giant into a Comanchero. I am trying to do some cost estimating on the project to ball park what it will take monetarily before I decide to put the amp under the knife. I know that I will need a new OT along with other parts, I am hoping to reuse as much as I can from this combo. The speaker, cab, chassis, existing tubes, and as much other stuff as I can keep are coming along for the ride. The biggest items on the purchase list are transformers. I am trying to get specs on the existing PT and I pulled the chassis and here are the numbers: 0-100V-120V-240C <- Input/primary voltages I think? 5V-0 6.3V-0 275V-0-275V - secondary/ output voltages? I dont see amperage listed at all and that seems to be my main concern. The comanchero calls for 220-0-220@125mA / 3.15@4a Without being able to see the amperage on the PT, how do I know if I can reuse it? I assume it can be tested in some manner, though I dont know if I have the tools yet to do so. Any pointers on this? If I can reuse this one, it would save a lot on the project. I have heard that these amps came with decent iron and the specs on the PT seem to indicate that but I dont want to misjudge the requirements. I obviously have a lot to learn still, my only projects thus far have been some mods to this amp, building a boost pedal and modifying an OD pedal. I am eyeballing the Camanchero because I want a PP amp, not SE (the blackheart seems to be a darn fine SE amp as is). I am looking for something with the tight responsiveness of a PP amp as it seems small SE amps are too spongy/muddy for me. Future plans for the amp could include an effects loop and/or reverb down the road if that matters at all. Thanks!Sun, 20 Apr 2014 21:08:49 -0400 October Bright Volume Noise(by John Bgron) Hi guys, My October Club has developed an annoying noise/buzz which gets louder as I turn the Bright Volume pot. I've swapped all my preamp tubes with a known working set and done the chopstick test around the wires of all the preamp tubes. I've also reflowed most joints in the area and on the ground bus. Nothing I've tried so far has had any effect on the noise. I'm really not sure what else to do other than replace the pot. The amp has worked flawlessly for a few days. Can anyone point me in the right direction? Many thanks, John Sun, 20 Apr 2014 18:49:49 -0400 Stand alone reverb!! Love this thing!!(by Zambo) <a href=" " target="newwin1398045696">[link]</a> Just built this and love it! Never had one or tried one but im a believer. Used the standard schematic for the g15 but instead of the 6k6 power tube I used a 12at7 with 1k cathode bypassed with 22uf . seems to work just fine.Sun, 20 Apr 2014 13:34:33 -0400 ECC88 / E88CC linearity(by DanGu) Hi! An old friend of mine asked me to build him an hifi SE amp using 300B tubes. So designing it I thinked to drive that big triode with an SRPP stage. My choice dropped to the E88CC looking at those grid curves. So LTSpice comes again with ayumi models gently provided by jazbo8 here, but can't find the model for that triode. So I used the ECC88 model, and in simulation worked unexpectedly well! My question is Are E88CC and ECC88 the same triode? On the net I found infos that are equivalents and on ebay these are selled sometime as the same tube, but datasheets does not agree. ECC88 exibits lower anode voltages than E88CC Can u help me to figure out if its the same tube or not? If not A tube model would be appreciated :) Thanks guysSat, 19 Apr 2014 22:59:12 -0400 P1eX clean for jazz(by Michael McCarthy) I have in mind building a clean p1eX for jazz. It doesn't have to be perfectly clean when dimed, but I would like it to be clean at least through the first half of the gain control on the first stage. I'm thinking of the following changes from a standard p1eX: 1. Allen TO11C output transformer, since the Doberman is not available. 2. Moving the tone stack to between the first two stages. 3. Adding a 0.022uF coupling cap following the second stage, before the master volume control. 4. Using the Merlin bone ray tone stack. 5. Placing the tone stack right between the first stage coupling cap, and the R21 gain attenuator. 6. Using a 5751 instead of a 12AX7. Here is a schematic: I have a few questions: There are some positions of the bone ray controls that have no capacitor in line, or no resistor in line, so I assume that the stack has to go right where I described it, and not obviate anything there. Are both of those assumptions correct? I do need another coupling cap after the second stage, right? Will this design, with the tone stack moved, and a 5751 instead of a 12AX7 have plenty of clean headroom? Is there anything else I might consider to go in a clean direction? I'm not interested in much distortion; maybe a little bluesy crunch, but that's about it. Sorry about that, Zaphod, et. al. I would really appreciate any comments from the fine people here. Thank you very much!Sat, 19 Apr 2014 22:49:53 -0400 Marshall Superlite TMB(by peterg) I am looking into building the above mentioned amp based on this schematic <a href=" " target="newwin1398045696">[link]</a> Classic Tone manufactures transformers for this amp but I'm hoping to use Hammond. Hammond is manufacturing a match (1750PA) for the Classic Tone 40-18037 output transformer which will be for sale at the end of February. They are currently designing the exact match for the Classic Tone 40-18035 power transformer but it will not be in production until the end of April. Does anyone know of a current Hammond PT model that will work? Sat, 19 Apr 2014 16:42:01 -0400 Mark L's fx loop(by sajyho) Hi guys, sorry to bother you again, I'm trying to add a fx loop to my HO. I've tries some of 12au7 designs but none worked well. I've read on this forum that Mark L has a nice design using 12ax7, but all the links to the schematic are old and broken. Does anyone have the schem, if have please post a link. Thanks SajadSat, 19 Apr 2014 11:24:15 -0400 Anode and cathode resistor effect on frequency response(by foulowl) Hi folks, Looking for a good rough rule of thumb with regard to how anode and cathode resistors affect frequency response, if they do at all. (for example, increasing X will boost high end, etc.) Thanks!!Sat, 19 Apr 2014 06:11:58 -0400 8" Celestion(by Peliass) Hi guys, I'm looking for a Celestion Vintage 8 or a Super 8. They're supposedly new but I can't find them anywhere! Does anybody have either of these speakers and if so, would be willing to sell? Also, any other 8" speakers that anyone is willing to sell? Thank you. Sat, 19 Apr 2014 03:29:00 -0400 Deluxe 57 reissue OT fault(by Frankleslie) I just recently had a Fender Deluxe 57 reissue in for repair. The guy who owned it said it had a strange "bubbling noise" when he played, and only occasionally. That was it. I started measuring all voltages and they where all pretty normal. The suprise came when I put a signal through it, ca. 3 watts and it started clipping, it should have been over 12W. After all other sources of fault was eliminated I changed the OT to a Magnetic Components type 40-18022, a 5E3 copy and the amp now sounds great and power is restored. Now, the really strange thing here is that the Mercury Magnetics OT that was installed showed no outer signs of damage, no smells, no arcing when it was tested in the amp. Even more strange is that when I measured the impedance ratio, it was ca 8K into 8 ohms, wich is very much as expected. I did not use high voltage AC, just a normal signal generator so as to measure the turns ratio. So it appears to be nothing wrong with it, but in service, it fails. Have any of you out there experienced something similar? I have read about the MM OTs just dying like this one. It also needs to be said that this player looks after his amps very well and he never plays fully cranked. Glad for any kind of feedback.Fri, 18 Apr 2014 14:26:55 -0400 Transformer Bass Response(by foulowl) Generally I have been advised that guitar should be eq'd with significant bass rolloff. Certainly it depends on what you're playing of course, but I have found generally that that is advised. Why then, the demand for oversized transformers with extended bass response? Edcor, Mercury Magnetics, etc? Just trying to understand. Thanks!Fri, 18 Apr 2014 13:21:22 -0400 Time to MOD the Hi-Octain(by Curran Murphy) OK- I have had my Hi-Octain running for over a year now, and I have built a train wreck/ac30, I want to figure out if I can add another pre-amp tube to this beast, and gain the heck out of it. When I bought this kit, I got the upgrade output tranny with it. This is a fun little amp,and I am want to figure out if I can also up the output tube into a SE el34 or bigger? Fri, 18 Apr 2014 11:52:32 -0400 Transformer selection for se el34(by kayakman) I am a newcomer to your community. I have had some positive exposure to Mercury Magnetics transformers. Thought of using there SE-3K OT and there F-CHMP-FS-P 362V-362V 53BiasB+6.3V 5v rectifier.(ss) My goal is to build an P1 Extreme ala EL34 with an input choke L1/C1/L1/C1 with a VVR. Does anone have experience with these transformers Is an input choke array overkill. I used to work on old Dynacos and Altec theatre amps. My son needs a tube amp, so I thought this would be a nice projectFri, 18 Apr 2014 08:29:01 -0400 New guy(by MrMDK) New guy here. I broke my left wrist in two places about 5 years ago. I tried every way I knew how to play guitar again and failed. Until last week. Sitting on my neighbors couch I was able to play guitar again for the first time in 5 years. I have been building back up every day. My fingers are ready to bleed. I am back with a vengeance. I sold off all my equipment to pay bills. So I am going to rebuild my equipment. This time I am going to build my equipment including my guitar. I live in Austin TX and have access to the Techshop. I can build pretty much anything out of wood or metal but electronics are a new hidden magic to me. I really am looking forward to being a part of this forum and learning from you guys. As for what I am going to build. I think I want to go 80s black label Fender and a 70s style marshal. Any and all help would be appreciated. If you need any custom wood work done I have access to cnc wood and I do cad design and will be willing to help or trade. Happy to be here. Fri, 18 Apr 2014 04:15:28 -0400 pentode or triode/3K or 5k for EL34(by kayakman) I am unsure if this amp is operating an el34 in pentode or triode I have an additional question regarding best primary impedance for EL34 3K or 5K Thu, 17 Apr 2014 23:36:05 -0400 October Impedance Selector(by John Bgron) Hi guys, I got my October Club working yesterday and played it all night. It's a great amp, thanks so much for the project. I'm confused about the impedance selector, I'm using a Hammond 125E and I hooked it up to the rotary switch as described in the build document but I'm not sure which is the 4, 8 or 16 ohm output. Can someone please explain with reference to the pole numbers on the switch? Many thanks, JohnThu, 17 Apr 2014 16:25:10 -0400 Possible replacement for polywood(by sajyho) Hi guys, I'm heading to build an ax84 1x12 cab. Unfortunately I can't find polywood anywhre, but I have access to MDF in every possible thickness, so my questions are: 1. can I use MDF in buffle and if so in which thickness? 2. if no, what is possible replacement for polywood in the baffle and back pannel? Thu, 17 Apr 2014 07:19:27 -0400 Trace Elliot Amp Repair(by boblove) This is the only area that I think this belongs. If this is out of bounds as far as forum rules go, let me know as well. So here goes. I have an old (older) Trace Elliot GP7SM 300 Bass amp head. All Solid state, non- tube so I'm a bit far out of my comfort zone on this one. It's non-working and I would like some coaching trouble shooting this one. I'm researching an accurate schematic and will have the chassis out of the enclosure and in the cradle tonight for pictures. The amp was puchased new from a Trace dealer circa 1996. It ran fine for about 2 month at which point it stopped working. It went in for a warranty repair and came out and ran for about a week and went back in and back out and in. The details are sketchy because it was so long ago but basically here's what I remember. The tech said some thing about a blown output transistor and having a hard time biasing the output transistor or some thing to that effect. I remember hearing alot about Trace amps of the time having problems. I don't recall specifics, meaning if it was design or poor part choices. I can't seem to find any old info on these amps about upgrades and such. Anyone here game to help me out with this ? Maybe some tech help for an adjustable amp cradle.Thu, 17 Apr 2014 07:04:36 -0400 EL34 vs EL84(by Mrwylde) Hey everyone, I am new to this site and have studied the H.O. build now for a couple of months, and am ready to ask some questions. 1. Can I run either the EL34 or the EL84 with the stock Hammond 269EX pt? 2. How do I bias the EL34 if I parallel the sockets?Wed, 16 Apr 2014 15:30:01 -0400 Traynor YCV40/50 power tube setup(by Andyman) I compared the scheamtic of the traynor YCV-40 and its british cousin the YCV-50B. One uses beam tubes (6L6GC) and the other uses the pentodes (EL34). But they have the same power supply.. 410V plate, 390 ohm screen dropper and small 1 watt 220 ohm screen resistors. I think they share transformers so the primary impedance is similar.. The grid bias in those amps have some sort of self-regulating function. But I would think that 1W 220 ohm screen resistors (with that small 390 ohm B+ dropper) would be a little small for EL34 tubes which screens can draw a lot of current when driven hard.. The YCV40 with its 6L6GC tubes with a modest 410V on the plates, 4K primary impedance and 40w output power are not super stressed, since the beam tubes draw much less current than the EL34 pentodes in the YCV50 Todays Marshalls with EL34 tubes are always fitted with 1K 5 watt screen resistors. Did Traynor miss something with their EL34 power stage design... ??? Wed, 16 Apr 2014 08:45:27 -0400 October Club blown transformer?(by John Bgron) Hi guys, I finally got around to finishing my October Club amplifier. It worked (almost) fine when I first powered it up but V2 started red plating. I powered down, removed the power tubes and started taking a few measurements then the fuse blew, and it kept blowing each time I turned the amp on. I disconnected the power transformer to test it but now it trips the safety switch in the house. Is it safe to assume the power transformer is blown? Many thanks, JohnTue, 15 Apr 2014 22:48:43 -0400 Modified Layout(by Rick West Coast) This is my first post. Just finished a 5F1 type amp as my first project & now planning my next build. I've got the cabinet to a 1930's radio and want to fit a guitar amp inside. The largest chassis that will fit is 11x7x2, it only has holes for 2 controls and the input jack based on a P1 design. Looking for one volume, one tone control. Speaker will be a Weber 6" so will opt for the 6N1P output Thanks in advance for any suggestionsMon, 14 Apr 2014 20:07:00 -0400 unknown mod function(by Gorhrut) before i begin, i am a newb, and most likely will not understand what u are saying unless it is written in very simple terms. ok, i received some mod advice for my preamp and dont really understand what it does. this is the advice: " the last big mod is the LED mod. Cathode (short leg) goes to ground and the anode connects to the resistor in the gain stages." the resistor he is talking about is v1a cathode resistor which is 820 ohm and has a .68uf bypass next to it. what effect will this have on the sound/what is the function? am i supposed to run the led in parallel with the resistor or after it in series? (ive seen people replace the resistor and bypass for LED bias and ive seen leds used on the plate but what will it do in this situation?)Mon, 14 Apr 2014 05:33:01 -0400 Output problems(by winghamwill) Hi, i have finnished building my first amp, an SEL and it sounds awesome!! So loud, no buzz, its just great, although, when recording last week i had a problem where it suddenly cut out, as we were stuck for time i changed amp at the time. Since then i have done a bit of investigation and the 8ohm output works fine, its just the 4 ohm, (i didnt put a 16 ohm output in). When i play through the 4 ohm i can hear a buzzing theough the output transformer almost to the sound of what im playing on my guitar? Is this just a fault with that output on the transformer or something different? Any ideas? Cheers WillMon, 14 Apr 2014 03:36:12 -0400 Finally decided on a build(by Darren Porter) Well, it took a long time to get some money together to do a build and that gave me a LOT of time to research exactly what I wanted to do. I learned SO MUCH from this site and the nice people who answered my questions and cleared-up all of my misconceptions and errors. The P1-eXtreme Theory Doc is an outstanding learning tool. I only wish there was more detail on the power supply section, but hey, I still learned a LOT from that document. This site also turned me on to Merlin's preamp book. Required reading for this hobby IMHO. I wavered back and forth between building a P1-eX and a hybrid Matchless DC30 clone based on the 20w PP poweramp here and I finally decided to just go ahead and buy and assemble a Trinity TC15 kit. If you are not familiar with that, it's basically a 15-watt DC30 with a MUCH better layout. I've long considered the DC30 to be my holy grail of tone but knew all along I'd never be able to afford one, so this is my chance. So, thanks for all the help I've received here and I'll still be around because I'd still like to build a 20w PP and experiment with the blues preamp and a couple others. Now I just have to wait for my kit to arrive... *sigh* -DarrenSun, 13 Apr 2014 14:08:21 -0400